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FEASIBILITY OF UTILIZING OIL-SANDS FLUID COKE
AS A SECONDARY SOURCE OF VANADIUM
by
Jing Feng
A thesis submitted in conformity with the requirements
for the degree of Master of Applied Science
Department of Chemical Engineering and Applied Chemistry
University of Toronto
© Copyright by Jing Feng 2017
ii
Feasibility of Utilizing Oil-Sands Fluid Coke as A Secondary Source
of Vanadium
Jing Feng
Master of Applied Science
Department of Chemical Engineering and Applied Chemistry
University of Toronto
2017
ABSTRACT
Oil-sands fluid coke (OSFC) is a major byproduct of upgrading Athabasca bitumen,
which has a particularly high vanadium concentration (0.15 wt% and predominantly vanadyl
porphyrins). This study explores the feasibility of extracting vanadium from OSFC. Chemical
activation with KOH or NaOH converts organic vanadium in OSFC into water-soluble inorganic
species. After chemical activation, water washing alone is able to dissolve over 98% of total
vanadium in OSFC given enough time. Sequential washing enhances vanadium dissolution,
shortens the washing process, and reduces the water usage by removing other elements (Ca, Ni,
Fe, Al and Si) in the first stage. Overall, it is technically feasible to recover over 90% of
vanadium in OSFC as calcium vanadate via alkali metal hydroxide chemical activation,
sequential water washing and calcium precipitation of vanadium. This process would allow the
recycle, reuse of alkali metal hydroxide, and produce highly porous activated carbon.
iii
ACKNOWLEDGEMENTS
Firstly, I would like to express my greatest appreciation to my supervisor, Professor
Charles Q. Jia, for his support, encouragement, and guidance in my research over the past years.
I am very grateful for everything he has done for me and for my development. I would also like
to thank Professor Donald W. Kirk for his kind advice throughout my entire research. They have
always made time for me and they have always been there for me when I struggled.
Next, I must thank Jocelyn Zuliani for the training in lab work. Along with all the
members in Green Technology, Celine, Leyan, Randeep, Johnathon, and Daniel. I am sure
without any of you, the time I have spent in the department would have been less enjoyable. I am
very glad that I have met and worked with all these wonderful people.
I am also very grateful to Dan Mathers and Jared Mudrik from ANALEST at Department
of Chemistry, University of Toronto. They are always patient with my questions and concerns on
analytical instruments, and thanks to their excellent training, I manage to learn a lot about
instrument troubleshooting.
Last but not least, I would like to acknowledge my dearest family. I want to thank them
for unconditional support regardless of my path in academia. Their support and their
understanding literally have helped me to go through any difficult times and to conquer any
challenges.
iv
TABLE OF CONTENT
ABSTRACT .................................................................................................................................... ii
ACKNOWLEDGEMENTS ........................................................................................................... iii
TABLE OF CONTENT ................................................................................................................. iv
LIST OF TABLES ........................................................................................................................ vii
LIST OF FIGURES ....................................................................................................................... ix
CHAPTER 1. OVERVIEW ............................................................................................................ 1
1.1. INTRODUCTION .......................................................................................................... 1
1.2. RESEARCH OBJECTIVES ........................................................................................... 2
CHAPTER 2. LITERATURE REVIEW ........................................................................................ 3
2.1. VANADIUM ....................................................................................................................... 3
2.1.1. General Background ..................................................................................................... 3
2.1.2. Commercial Recovery Processes .................................................................................. 4
2.2. CHARACTERIZATION OF OIL-SANDS FLUID COKE ................................................ 4
2.3. CHEMICAL ACTIVATION ON FLUID COKE.............................................................. 13
CHAPTER 3. MATERIALS AND METHODS .......................................................................... 17
3.1. DETERMINATION OF TOTAL VANADIUM CONTENT IN OIL-SANDS FLUID
COKE ........................................................................................................................................ 17
3.1.1. Direct Acid Leaching Using Various Acids ............................................................... 19
3.1.2. Direct Caustic Leaching Using 1M KOH Solution .................................................... 19
3.1.3. Dissolution of Ashed OSFC Using Aqua Regia ......................................................... 19
3.1.4. X-Ray Fluorescence (XRF) on Ashed OSFC ............................................................. 20
3.2. VANADIUM RECOVERY USING CHEMICAL ACTIVATION .................................. 20
3.2.1. Chemical Activation of OSFC .................................................................................... 22
3.2.2. Washing Process of Activation Product ..................................................................... 23
3.3. VANADIUM SEPARATION AND STREAM PURIFICATION .................................... 25
3.3.1. Solvent Extraction ....................................................................................................... 27
v
3.3.2. Sequential Washing Using Water ............................................................................... 29
CHAPTER 4. RESULTS AND DISCUSSIONS .......................................................................... 30
4.1. DETERMINATION OF TOTAL VANADIUM CONTENT IN OIL-SANDS FLUID
COKE 30
4.1.1. Direct Leaching of Raw Fluid Coke ........................................................................... 30
4.1.2. Acid Dissolution of Ashed OSFC Using Aqua Regia .......................................... 31
4.1.3. XRF Analysis on Ashed OSFC ............................................................................. 32
4.2. VANADIUM RECOVERY USING CHEMICAL ACTIVATION ............................. 34
4.2.1. Activation Yield and Characteristics of Activated Coke ............................................ 34
4.2.2. Fate of Vanadium During Chemical Activation and Subsequent Washing .......... 36
4.3. VANADIUM SEPARATION AND STREAM PURIFICATION ............................... 38
4.3.1. Solvent Extraction with Aliquat® 336........................................................................ 38
4.3.2. Sequential Washing Using Water ......................................................................... 40
CHAPTER 5. PROPOSED PROCESS OF VANADIUM RECOVERY VIA CHEMICAL
ACTIVATION ON OSFC ............................................................................................................ 44
CHAPTER 6. CONCLUSIONS AND FUTURE RESEARCH ................................................... 46
CHAPTER 7. REFERENCES ...................................................................................................... 48
CHAPTER 8. APPENDICES ....................................................................................................... 53
APPENDIX 1 CALIBRATION CURVES ............................................................................... 53
Single-element ICP Standard Vanadium Calibration ........................................................... 53
Multi-element ICP Standard Vanadium Calibration ............................................................. 54
APPENDIX 2 XRF RAW DATA ............................................................................................. 63
APPENDIX 3 SAMPLE PELLETS OF ASHED OSFC FOR XPF ANALYSIS .................... 66
APPENDIX 4 CORRECTED XRF RESULTS ........................................................................ 67
APPENDIX 6 DETERMINATION OF KOH AND NAOH PELLET PURITY ..................... 68
APPENDIX 7 CALCULATION OF SOLVENT PREPARATION ........................................ 69
APPENDIX 8 DETERMINATION OF PARTITION COEFFICIENT AND MIXING TIME
IN SOLVENT EXTRACTION ................................................................................................. 70
Methodology ......................................................................................................................... 70
Results and Discussions ........................................................................................................ 72
APPENDIX 9 OTHER ELEMENT CONCENTRATION IN SEQUENTIAL WASHING .... 73
vi
APPENDIX 10 OLI SIMULATION ON VANADIUM PRECIPITATION ........................... 74
vii
LIST OF TABLES
TABLE 1 VANADIUM WORLD ANNUAL PRODUCTION BY COUNTRY
(HTTP://MINERALS.USGS.GOV) ....................................................................................... 3
TABLE 2 PROPERTY PROXIMATE ANALYSIS OF FLUID COKE FROM SYNCRUDE,
WT% (FUIMSKY,1998) ........................................................................................................ 9
TABLE 3 ULTIMATE ANALYSIS OF FLUID COKE FROM SYNCRUDE, WT%
(FUIMSKY,1998) ................................................................................................................... 9
TABLE 4 ANALYSIS OF FLUID COKE ASH COMPOSITION FROM SYNCRUDE, WT%
(FUIMSKY,1998) ................................................................................................................. 10
TABLE 5 THE ICP-AES OPERATING CONDITIONS ............................................................. 18
TABLE 6 CHEMICALS INVOLVED IN CHEMICAL ACTIVATION PROCESS .................. 21
TABLE 7 THE INFORMATION OF MATERIALS INVOLVED IN SECTION 3.3 ................ 26
TABLE 8 CHEMICAL COMPOSITION OF 0.5 M ALIQUAT® 336 SOLVENT (500 ML) ... 27
TABLE 9 ASH CONTENT OF FLUID COKE PARTICLES OF DIFFERENT PARTICLE
SIZES .................................................................................................................................... 32
TABLE 10 YIELD OF CHEMICAL ACTIVATION AND ASH CONTENT OF ACTIVATED
COKE AFTER WASHING WITH WATER ....................................................................... 34
TABLE 11 FATE OF VANADIUM AFTER CHEMICAL ACTIVATION AND DURING
WATER AND DILUTED HCL WASHING (BASED ON 25 G OF DRIED OSFC) ......... 36
TABLE 12 VANADIUM DISTRIBUTION IN EACH ACTIVATED PRODUCT CATEGORY
IN A PERCENTAGE BASIS ............................................................................................... 37
TABLE 13 VANADIUM CONCENTRATIONS IN THE AQUEOUS PHASE UPON
COMPLETION OF SOLVENT EXTRACTION WITH PRETREATED AND NON-
PRETREATED SOVLENTS (0.5M, A/O=1) ...................................................................... 39
TABLE 14 CONCENTRATION AND EXTRACTION EFFICIENCY OF 0.5 M ALIQUAT®
336 IN KEROSENE WITH DIFFERENT A/O RATIOS .................................................... 40
TABLE 15 CONCENTRATION AND EXTRACTION EFFICIENCY OF 0.1 M ALIQUAT®
336 IN KEROSENE WITH DIFFERENT A/O RATIOS .................................................... 40
TABLE 16 VANADIUM CONCENTRATION AND RECOVERY PERCENTAGE IN 4-
HOUR PER STAGE ............................................................................................................. 41
viii
TABLE 17 VANADIUM CONCENTRATION AND RECOVERY PERCENTAGE IN 1-
HOUR PER STAGE ............................................................................................................. 41
TABLE 18 COMPOSITIONS OF WASHING SOLUTION AND RECOVERY PERCENTAGE
DURING FIRST TWO WASHING STAGES (1 HOUR PER STAGE) ............................. 42
TABLE 19 A SAMPLE OF CALIBRATION FOR VANADIUM ON ICP-AES ....................... 53
TABLE 20 A SAMPLE OF CALIBRATION FOR VANADIUM ON ICP-AES ....................... 54
TABLE 21 A SAMPLE OF CALIBRATION FOR ALUMINUM ON ICP-AES ....................... 55
TABLE 22 A SAMPLE OF CALIBRATION FOR CALCIUM ON ICP-AES .......................... 56
TABLE 23 A SAMPLE OF CALIBRATION FOR IRON ON ICP-AES .................................. 57
TABLE 24 A SAMPLE OF CALIBRATION FOR POTASSIUM ON ICP-AES ...................... 58
TABLE 25 A SAMPLE OF CALIBRATION FOR NICKEL ON ICP-AES ............................. 59
TABLE 26 A SAMPLE OF CALIBRATION FOR SILICON ON ICP-AES ............................ 60
TABLE 27 XRF ANALYSIS RESULTS FOR ASHED 53-106 µM FLUID COKE .................. 63
TABLE 28 XRF ANALYSIS RESULTS FOR ASHED 106-150 µM FLUID COKE ................ 64
TABLE 29 XRF ANALYSIS RESULTS FOR ASHED 150-212 µM FLUID COKE ................ 65
TABLE 30 AN ESTIMATION OF OTHER ELEMENTS USING VANADIUM CONTENT TO
CORRECT XRF RESULTS ................................................................................................. 67
TABLE 31 PURITY OF KOH PELLET TITRATION RESULTS ............................................. 68
TABLE 32 PURITY OF NAOH PELLET TITRATION RESULTS ......................................... 68
TABLE 33 DETERMINATION OF THE PARTITION COEFFICIENT OF SYNTHETIC
SYSTEM AND MIXING TIME (0.5 M, A/O=2, PRETREATED 7 TIMES)..................... 72
TABLE 34 OTHER ELEMENT CONCENTRATION IN SEQUENTIAL WASHING (1HR, 5-
STAGE) ................................................................................................................................ 73
ix
LIST OF FIGURES
FIGURE 1 SIMPLIFIED FLUID COKE PRODUCING SCHEMATICS (FURIMSKY, 2000). . 5
FIGURE 2 SEM SURFACE IMAGE OF FLUID COKE PARTICLES (CHEN, 2002) ............... 6
FIGURE 3 SEM IMAGE OF A CONTROLLED CHEMICALLY ACTIVATED FLUID COKE
(SSA= 340 M2/G) (CHEN, 2002) ........................................................................................... 7
FIGURE 4 TYPICAL STRUCTURES OF VANADYL PORPHYRINS ...................................... 8
FIGURE 5 SOLUBILITY OF VANADYL PORPHYRINS AT 23±2 °C AS A FUNCTION OF
SOLUBILITY PARAMETER OF SOLVENT (FREEMAN ET AL., 1990) ...................... 12
FIGURE 6 APPARATUS FOR CHEMICAL ACTIVATION PROCESS .................................. 22
FIGURE 7 THE WASHING PROCESS OF ACTIVATED PRODUCT FOR THE 50HOURS
WASHING ............................................................................................................................ 25
FIGURE 8 COMPARISON OF LEACHING EFFECT OF VARIOUS AGENTS OVER 48
HOURS ................................................................................................................................. 30
FIGURE 9 AQUA REGIA DISSOLUTION OF VANADIUM IN ASHED OSFC WITH
DIFFERENT SOLID-LIQUID RATIOS AND DURATIONS ............................................ 31
FIGURE 10 VANADIUM CONTENTS OF FLUID COKE PARTICLES OF DIFFERENT
SIZES .................................................................................................................................... 33
FIGURE 11 PORE SIZE DISTRIBUTION OF KOH- AND NAOH ACTIVATED COKE ...... 35
FIGURE 12 CUMULATIVE SPECIFIC SURFACE AREA OF KOH AND NAOH
ACTIVATED COKE ............................................................................................................ 35
FIGURE 13 DEPENDENCE OF CHLORIDE REMOVAL FROM RAFFINATE ON NUMBER
OF PRETREATMENT STAGES ......................................................................................... 38
FIGURE 14 PROPOSED PROCESS OF VANADIUM RECOVERY FROM OSFC VIA
CHEMICAL ACTIVATION, SEQUENTIAL WATER WASHING AND CALCIUM
PRECIPITATION ................................................................................................................. 45
FIGURE 15 A SAMPLE OF CALIBRATION FOR VANADIUM ON ICP-AES ..................... 54
FIGURE 16 A SAMPLE OF CALIBRATION FOR VANADIUM ON ICP-AES ..................... 55
FIGURE 17 A SAMPLE OF CALIBRATION FOR ALUMINUM ON ICP-AES ..................... 56
FIGURE 18 A SAMPLE OF CALIBRATION FOR CALCIUM ON ICP-AES ........................ 57
FIGURE 19 A SAMPLE OF CALIBRATION FOR IRON ON ICP-AES .................................. 58
FIGURE 20 A SAMPLE OF CALIBRATION FOR POTASSIUM ON ICP-AES ..................... 59
x
FIGURE 21 A SAMPLE OF CALIBRATION FOR NICKEL ON ICP-AES ............................. 60
FIGURE 22 A SAMPLE OF CALIBRATION FOR SILICON ON ICP-AES ............................ 61
FIGURE 23 CALIBRATION CURVE FOR MULTIELEMENT STANDARDS ON ICP-AES 62
FIGURE 24 BRIQUETTED XRF SAMPLES ............................................................................. 66
FIGURE 25 . RELATION BETWEEN THE CONCENTRATION OF VANADIUM
TRANSFERRED TO THE ORGANIC PHASE TO THAT REMAINED IN THE
AQUEOUS PHASE THROUGH THE EXTRACTION BY 0.5 M ALIQUAT® 336
DISSOLVED IN KEROSENE FROM 0.1 M NAOH OR 3 M HCL MEDIA AT 25 °C (EL-
NADI AND ET AL., 2009) .................................................................................................. 70
FIGURE 26 INTERFACE OF OLI STUDIO ON WATER ANALYSIS AND INPUT OF
SPECIES AND CONCENTRATIONS (NAOH-ACTIVATED OSFC) .............................. 75
FIGURE 27 SIMULATION RESULTS OF VANADIUM PRECIPITATION BY ADDITION
OF CALCIUM ION (NAOH-ACTIVATED OSFC) ........................................................... 76
1
CHAPTER 1. OVERVIEW
1.1. INTRODUCTION
Oil-sands fluid coke (OSFC) is an upgrading byproduct from Athabasca oil-sands
bitumen. It is named after fluid coke because of the fluidized-bed reactor used in cracking
process, in which long-chain bitumen molecules are continuously fed into the coker and
simultaneously transferred between the reactor and burner vessels to gain energy for thermal
cracking. Upon the completion of cracking, short chain hydrocarbon streams are achieved and
transferred for future refineries, whereas fluid coke was produced as the waste of this process.
Vanadium, which is a valuable transition metal and often used in a wide range of industries and
applications, is found in crude oils and bitumens with a concentration ranging from 0.04 to 600
ppm in western Canada (Hodgson,1954; Bensebaa, 2000). The form of vanadium present in
crude oils and bitumens is mainly vanadyl porphyrins (Dechaine & Gray, 2010; Zhao et al.,
2013). Initially, it was hypothesized that vanadium would be captured and retained in the same
chemical state after thermal cracking (Li & Le, 2007). Another study discovered crystalline
clusters associated with vanadium, silicon, oxygen, sulfur, and iron were found within the carbon
structure by Transmission Electron Microscopy (TEM) analysis (Zuliani et al., 2016). The
elemental speciation of vanadium in OSFC remains unclear due to complex matrix effects.
Chemical activation is one of the most popular methods to prepare active carbon. By
introducing chemicals into the activation process, a lower activation temperature is required and
a superior grade of activated carbons with high specific surface areas is achieved. Hence,
chemical activation is widely used in the applications such as water and gas purifications.
Chemical activation is essentially an oxidation process that occurs on carbonaceous precursors
with the assistance of the activating agent. Among different activating agents, alkaline
hydroxides have shown their outstanding capability in chemical activation due to their strong
corrosive and stable nature. It is hypothesized that the chemical activation process can oxidize
vanadium within the porphyrin structure and convert it into an inorganic form. On the other
hand, due to the dense structure of fluid coke, it is difficult for chelating agents to penetrate
through the surface of fluid coke to recover vanadium from its organometallic form. With the
help of a developed porous structure, inorganic vanadium becomes more accessible for recovery.
2
OSFC is viable as an alternative source of vanadium as the content of vanadium present
in fluid coke has exceeded the ones in certain lean vanadium ores. With the massive daily
production of fluid coke in bitumen refinery, vanadium can become as an extremely value-added
byproduct.
1.2. RESEARCH OBJECTIVES
The overall objective of this research was to study the technical feasibility of recovering
vanadium from OSFC, while converting the coke to porous carbon. To achieve this objective,
following listed tasks have been carried out:
1. Develop a comprehensive method for quantifying vanadium content in oil sands fluid
coke;
2. Determine the fate of vanadium during KOH chemical activation to recover
vanadium from OSFC;
3. Determine the feasibility of using NaOH - a cheaper activating agent to recover
vanadium from fluid coke;
4. And explore the options for separating vanadium from other elements in leaching
solutions.
3
CHAPTER 2. LITERATURE REVIEW
2.1. VANADIUM
2.1.1. General Background
Vanadium is a transition metal that was firstly discovered by Manuel Del Rio in 1801
within a Mexican lead vanadate ore. It is the 22nd abundant element in the crust of Earth
(Moskalyk & Alfantazi, 2003). Vanadium is widely distributed in various forms; there are more
than 50 vanadium-containing minerals such as carnotite, roscoelite, vanadinite, mottramite, and
partonite (Perron, 2001). Other main sources of vanadium except ores and rock are metallurgical
slags, spent catalysts, petroleum residues (Reese, 2001; Das et al., 2007). Vanadium is well
known for its high tensile strength, fatigue resistance, and hardness; it has a broad range of
applications in metal alloys. Due to the four oxidation states that vanadium possess, vanadium
redox flow battery is another application that utilizes its unique characters. Currently, vanadium
is massively produced by Japan, United States, China, South Africa, and Russia. The detailed
annual production from 2008 to 2012 is tabulated in Table 1.
Table 1 Vanadium World Annual Production by Country (http://minerals.usgs.gov)
Country
Production (thousand tonnes)
2008 2009 2010 2011 2012
China 26 29 32 36 39
United States 0.52 0.23 1.06 0.59 0.272
Russia 14.5 14.5 15 15 15
South Africa 23.3 22.6 23.5 2.5 20
Japan 0.56 0.56 0.56 0.56 0.56
4
2.1.2. Commercial Recovery Processes
It is quite difficult to produce metallic vanadium as it often combines with other elements
in its sources. The salt roasting process that converts vanadium into water-soluble vanadates
followed by leaching is a well-known way of vanadium extraction. Alkali metal salts such as
sodium chloride, sodium carbonate, and sodium sulfate are commonly used for roasting, while
leaching agents can be aqueous solutions of acids and bases or simply water.
In general, salt roasting can take place at temperature between 600 °C and 1250 °C
within a fluidized bed reactor or a multiple hearth furnaces (Chen et al., 2006; Mahdavian et al.,
2006) The proposed reaction of roasting is shown in Equations 1-3 (Gupta, 1992; Geyrhofer et
al., 2003; Hukkanen and Walden, 1985)
Equation 1
or
Equation 2
or
Equation 3
2.2. CHARACTERIZATION OF OIL-SANDS FLUID COKE
Fluid coke, flexi coke, and delayed coke are the main three types of coke. Physical
properties and chemical compositions of the different cokes vary due to their unique coking
processes. In the fluid-coking process, the feedstock is evenly dispersed and injected into the
fluidized bed reactor after preheating to 300°C. The reactor vessel (fluid coker) is operated at a
temperature range of 480°C to 550°C. While the feed vapors are cracked within the temperature
range, a liquid film is forming on the coke particles. Hence, the coke particles grow by layer as
they flow back and forth between the reactor vessel and the heater. During the coking process,
5
some of the coke (15-25%) is burned with air to provide sufficient heat for the coking process
and to eliminate the requirement for external energy supplies. Hot coke nuclei are obtained and
then circulated back to the reactor vessel with unburned hot coke to sustain the cracking
reactions and maintain the reactor temperature. A simplified version of fluid-coking process
scheme is shown in Figure 1 (Furimsky, 2000).
Figure 1 Simplified Fluid Coke Producing Schematics (Furimsky, 2000).
While the coke is circulating between the reactor vessel and the heater, non-volatile
materials are attaching to the surface of the coke, thereby forming a non-porous smooth surface
6
morphology with an “onion-like” internal structure. The Scanning Electron Microscope (SEM)
image of fluid coke particles (100 – 200 µm) is shown in Figure 2. Once the carbon structure
gets damaged via a controlled chemical activation, the internal layered structure is exposed and
captured by SEM analysis as shown in Figure 3.
Figure 2 SEM Surface Image of Fluid Coke Particles (Chen, 2002)
7
Figure 3 SEM Image of a Controlled Physically Activated Fluid Coke (SSA= 340 m2/g)
(Chen, 2002)
Vanadium in coke originates from crude oil or other petroleum feedstock. It has been
reported that vanadium is contained within the highly aromatic, highly polar asphaltene fraction
(Biggs et al., 1985). The asphaltene fraction refers to the fraction of toluene soluble and n-
alkane-insoluble (e.g., n-heptane) species present in a petroleum feed (Dechaine & Gray, 2010).
Previous studies have shown that in crude oils and bitumens, vanadium presents predominantly
in the form of vanadyl porphyrins which is vanadyl ion (VO2+) complexed with porphyrins
(Amorim et al., 2007). In the porphyrin macrocycle, vanadium is bonded with one oxygen atom
and the four nitrogen atoms from the porphyrin structure. Some typical vanadyl porphyrin
structures are shown in Figure 4. Other studies have indicated that the vanadyl porphyrin
compounds contribute to 50% - 80% of the total vanadium present in crude oil (Amorim et al.,
2007). The most common forms of vanadyl porphyrins identified in petroleum deposits are the
8
Etio form (Figure 4b) and the DPEP form (Figure 4d) (Dechaine & Gray, 2010; Qian et al.,
2008). The majority of vanadium compounds exist as vanadyl ion (VO2+) in the form of vanadyl
porphyrins with porous structures frozen in solid (Amorim et al., 2007). The primary chemical
environment of vanadium is unchanged through the coking process, in which vanadium is almost
quantitatively captured in the coking byproduct (Dechaine & Gray, 2010; Kelemen et al., 2007).
Figure 4 Typical Structures of Vanadyl Porphyrins
The chemical composition of fluid coke was studied by Furimsky over the years. The
proximate, ultimate and ash composition analyses over fluid coke produced from 1979 to 1995
are shown in Table 2, Table 3, and Table 4.
9
Table 2 Property Proximate Analysis of Fluid Coke from Syncrude, wt% (Fuimsky,1998)
Years 1979-1980 1980-1982 1982-1983 1983-1985 1985-1995
Property
Proximate
Moisture 0.44 0.60 0.50 0.69 0.25
Ash 5.40 7.21 5.18 7.52 4.83
Volatiles 4.85 5.11 6.23 6.10 4.99
Fixed Carbon 89.31 87.08 88.09 85.69 89.95
Table 3 Ultimate Analysis of Fluid Coke from Syncrude, wt% (Fuimsky,1998)
Years 1979-1980 1980-1982 1982-1983 1983-1985 1985-1995
Ultimate
Carbon 82.73 80.73 81.80 80.94 83.73
Hydrogen 1.72 1.63 1.66 1.56 1.77
H/C 0.25 0.24 0.24 0.23 0.25
Nitrogen 1.75 1.70 1.98 1.73 2.03
Sulfur 6.78 6.63 6.84 6.15 6.52
10
Years 1979-1980 1980-1982 1982-1983 1983-1985 1985-1995
Oxygen 1.18 1.50 2.04 1.41 0.88
Table 4 Analysis of Fluid Coke Ash Composition from Syncrude, wt% (Fuimsky,1998)
Years 1979-1980 1980-1982 1982-1983 1983-1985 1985-1995
Ash content 5.4 7.21 5.18 7.52 4.83
V2O5 4.46 3.2 4.86 3.21 4.94
Al2O3 24.4 20.9 24.2 24.9 24.3
Fe2O3 9.72 8.18 9.26 12.1 11.4
TiO2 3.64 2.86 3.25 4.84 4.63
CaO 4.26 2.58 4.2 1.63 2.94
MgO 1.62 1.29 1.44 1.4 1.46
Na2O 1.51 1.17 1.57 1.16 1.67
K2O 1.83 1.78 1.83 1.93 1.72
BaO 0.2 0.15 0.07 0.14 0.09
SrO 0.11 0.06 0.09 0.06 0.11
11
Years 1979-1980 1980-1982 1982-1983 1983-1985 1985-1995
MnO 0.26 0.21 0.25 0.29 0.27
Cr2O3 0.08 0.05 0.08 0.08 0.09
Total metal 52.0 42.5 51.1 51.8 53.7
SiO2 38.8 50.1 41.6 41.3 37.6
P2O5 0.25 0.21 0.23 0.35 0.04
SO3 3.59 2.73 2.65 1.87 2.88
Loss on fusion 2.9 2.3 1.82 2.5 2.62
Total 97.6 97.8 97.4 97.8 96.9
It is illustrated that the ash contents and the oxide contents in Table 4 exhibit relatively
large variations over the years. However, the weight fractions of major elements with respect to
fluid coke, which are calculated from the ash contents, oxide contents in ash, and the elemental
fractions in their corresponding oxides, remain relatively constant. Therefore, the vanadium
content present in the OFSC produced from 1979 to 1995 is 0.135 wt%± 0.004 wt% (1998).
There have been numerous studies attempting to identify the form of vanadium present in
crude oil and petroleum (Zhao et al., 2013). To quantify vanadium in crude oil and its
derivatives, several researchers have used solvent precipitation and extraction schemes to enrich
vanadium compounds in a single fraction. As mentioned previously, much of the vanadyl
porphyrins in crude oil are concentrated in asphaltene fraction. Asphaltenes can adopt a colloidal
character in solution, the tendency to aggregate and precipitate in n-alkane solvents (primarily n-
pentane or n-heptane) (Dechaine & Gray, 2010). This partitioning of vanadyl compounds in the
asphaltene fraction could be attributed to their low solubility (in the order of 10-5 M) in most
12
solvents (Freeman et al., 1990), as shown in Figure 5 below. Chlorinated solvents (e.g.,
chloroform and dichloromethane) showed the highest solubility, while all other solvents showed
very little solvent power for the vanadyl porphyrins. Several studies have examined the efficacy
of chemical extraction methods for vanadyl porphyrins within asphaltene samples. As observed
with the solvent-based extraction methods, these methods are not likely to completely (the
highest recovery was 57% of the free porphyrins initially present) extract all of the
metalloporphyrins present in petroleum samples (Yin et al., 2009). This chemical limitation is
further compounded by the fact that asphaltenes form aggregated colloidal structures in most
organic solvents, which could further deter the extraction of the metalloporphyrins from the
asphaltene phase.
Figure 5 Solubility of Vanadyl Porphyrins at 23±2 °C as A Function of Solubility
Parameter of Solvent (Freeman et al., 1990)
13
2.3. CHEMICAL ACTIVATION ON FLUID COKE
Activated carbon is often produced using an activation process from carbonaceous
materials such as biomass (e.g. wood, nutshells, and peat) and petroleum pitch (e.g. coal and
coke). There are two main types of activation methods: chemical activation and physical
activation. Physical activation is also called thermal activation as it uses steam, carbon dioxide,
air, or a mixture of any of these to perform a partial gasification/ oxidation process at a relatively
high temperature that is required by chemical activation. Prior to physical activation, an
additional process called carbonation is required, in which a thermal process carried out in an
inert environment is performed. On the other hand, chemical activation requires assistance of
chemicals – activating agents. Common activating agents include zinc chloride (ZnCl2),
phosphoric acid (H3PO4), and potassium hydroxide (KOH). With the help of an activating agent,
it often requires lower temperatures for a chemical activation achieve an equal and often greater
degree of activation. The degree of activation is typically measured by specific surface area
(SSA) in m2/g. The SSA of chemically activated carbon can exceed 2000 m2/g, while that of
physically activated carbon is typically below 1000 m2/g. Also, chemical activation can be
carried out in one step, combining carbonization and oxidation processes. It also results in a
higher yield. (Lillo-Ródenas et al., 2003). However, there are some drawbacks associated with
chemical activation such as a highly corrosive environment and the need of a washing step that
requires a large quantity of water (Teng & Lin, 1998).
Both physical and chemical activations have been conducted on fluid coke previously. A
two-step physical activation was carried out using steam on oil-sands fluid coke produced in
Alberta (DiPanfilo & Egiebor, 1996). After 6 hours of activation at 850°C and atmospheric
pressure, the BET-SSA of activated fluid coke was 318 m2/g with a yield below 50%. The BET
surface area of the coke-based activated carbon is substantially smaller than most of commercial
activated carbon that have an SSA 800 m2/g. Applying chemical activation on fluid coke using
KOH, Zuliani et al. demonstrated that at 850°C and atmospheric pressure for 2 hours, they were
able to produce an SSA of 1957 m2/g with a yield of 56%. The weight ratio of KOH to coke was
2.5:1. Hence, chemical activation is more effective to activate oil-sands fluid coke and create a
better porous structure (Zuliani et al., 2014).
14
Alkali metal hydroxides, particularly KOH, are well known chemical activating agents.
The activated carbon produced with alkali metal hydroxides possesses some unique features such
as low ash content, high adsorption capacity, and narrow pore size distribution (Lillo-Ródenas et
al., 2003).
There are a series of chemical reactions in literature describing chemical activation with
alkali metal hydroxides at 600 -900 °C for various precursors similar to fluid coke (petroleum
cokes or coals). It was suggested that with KOH at 600 - 700°C, K2CO3 and hydrogen were the
main products, whereas only a small portion of CO2 was detected (Otowa et al., 1993) as shown
by Equation 4-6.
Equation 4
Equation 5
Equation 6
Once the activation temperature raised to more than 700°C, metallic potassium is
produced due to the reduction of K2O by reducing agent (carbon or hydrogen) at high
temperature. The reaction mechanism is represented in the equations below:
Equation 7
Equation 8
The author also emphasized that the metallic potassium was in a mobile phase at the
higher activation temperatures, which provided an opportunity for metallic potassium to
intercalate to the carbon matrix and to create pores. The reaction mechanism was further defined
and described in equations below for KOH activation temperature at 600 - 900°C (Yuan et al.,
2012).
15
Equation 9
At temperature over 900°C, following reaction was suggested:
Equation 10
This study confirmed that potassium ion was reduced into metallic potassium at high
temperature chemical activations and established the feasibility of recovering and reusing KOH
in the activation process, as metallic potassium can be readily converted into KOH when reacting
with water.
16
NaOH is a common alkali metal hydroxide widely used in industry, and it is significantly
less expensive than KOH. NaOH-based chemical activation has been studied and compared with
KOH-based activation. It was concluded that the activation mechanisms were the same.
However, KOH was able to start activation at a lower temperature (400 °C) than NaOH (570°C)
(Lillo-Ródenas et al., 2003). It was suggested that metallic sodium can be produced but NaOH-
based activation doesn’t induce intercalations that separate and enlarge graphene layers in
graphitic carbon (Raymundo-Pin ̃ero et al., 2005).
17
CHAPTER 3. MATERIALS AND METHODS
3.1. DETERMINATION OF TOTAL VANADIUM CONTENT IN OIL-
SANDS FLUID COKE
Previous studies have shown that there is approximately 0.135% of vanadium present in
oil-sands fluid coke. To study the recovery of vanadium from fluid coke, it is essential to
accurately determine the total vanadium content and better understand the chemical form of
vanadium in raw fluid coke.
The fluid coke used in the experiments was produced by Syncrude Ltd.Canada. Fluid
coke with a particle size range between 150 and 212 µm was used throughout the study
described in this chapter. Some properties and the typical composition of fluid coke were
obtained from previous studies (Cai & Jia, 2010; Furimsky, 1989).
The leaching agents included concentrated hydrochloric acid (HCl), concentrated nitric
acid (HNO3), Aqua Regia, and 1M potassium hydroxide (KOH) solution. Solid KOH pellets
were purchased from Sigma-Aldrich Canada (Oakville, ON), and KOH content is above 85% as
per the manufacturer; the rest is mainly crystalline water. 1 M KOH solution was freshly made
prior to each caustic leaching experiments, due to its high reactivity towards carbon dioxide.
Both concentrated HCl and concentrated HNO3 was purchased from Caledon Laboratories Ltd
(Halton Hills, ON). Aqua Regia was freshly prepared by slowly mixing one volume of
concentrated HNO3 with four volumes of concentrated HCl to meet a molar ratio of 1:3.
Other reagents involved Milli-Q water (Millipore, Etobicoke, ON) and vanadium
standard for ICP (Fluka Analytical, Sigma-Aldrich Co. LLC., Oakville, ON). All solutions were
prepared using Milli-Q water with a resistivity of 18.2 MΩ.cm at 25 °C. The purity of vanadium
standard is 1000 ± 2 mg/L with a 5 vol% HNO3 background. The standard solutions for ICP
calibration were prepared by diluting the stock standard with 5% HNO3 into 0 mg/L, 0.5 mg/L, 1
mg/L, 5 mg/L, 10 mg/L, and 20 mg/L.
Qualification of elemental composition of aqueous samples containing vanadium was
carried out by ICP-AES housed and maintained by ANALEST in University of Toronto’s
18
Chemistry department. Specifically, vanadium concentrations were determined mostly from the
wavelength of 292.464 nm due to its high sensitivity and less interferences with other elements
that present in the aqueous sample. In limited cases, two other wavelengths (290.881 and
311.837 nm) were used as references. The operating conditions for ICP-AES are tabulated in
Table 5.
Table 5 The ICP-AES Operating Conditions
Parameter
Analytical wavelengths for V (nm) 290.881, 292.464, 311.837
RF Power 1300 W
Plasma gas flow rate 15 µL/min
Auxiliary gas flow rate 0.2 µL/min
Nebulizer gas flow rate 0.8 µL/min
Sample flow rate 1.5 µL/min
View mode Axial
Read Peak area
Reading delay time 45 s
Replicates 3
Gas Argon
19
Trace metal concentrations were determined by dilution using a 5-level calibration curve.
Calibration standards were prepared using 5 vol% HNO3 solution. Along with every batch of
tests, two additional check standards with concentrations of 0 and 1 mg/L were included in
sample analysis to monitor the instrument’s working condition during ICP analysis. Calibration
data and curves are provided in Appendix 1.
3.1.1. Direct Acid Leaching Using Various Acids
The direct leaching process was modified based on the method created by former
students in Green Technology Lab. In their procedure, 1 g of fluid coke was leached using 16
mL fresh Aqua Regia at 100 rpm and 50 °C. Due to the large dilution factor for ICP sample
preparation, the vanadium concentration was below detection limit. In this study, the solid-liquid
ratio was modified to 1 g of fluid coke to 4 mL of Aqua Regia. Upon completion of the leaching
process, all leachate was filtered via a 0.45 µm pore size syringe filter and 2.5 mL of the leachate
was transferred to a 10-mL volumetric flask and Mill-Q water was added to the mark to make up
a 10 mL aqueous solution with an approximate 5 vol% HNO3 background.
A comparison experiment of direct leaching using HNO3 and HCl was also conducted,
where the solid to liquid ratio was kept at 1 g of fluid coke to 4 mL of acid.
3.1.2. Direct Caustic Leaching Using 1M KOH Solution
Caustic leaching is a common method used to dissolve vanadium from vanadium bearing
solid such as spent catalyst (Chen et al., 2006; Zeng & Yong Cheng, 2009). Since fluid coke
contains alumina and silica which are stable in acidic conditions, caustic leaching process was
expected to dissolve alumina and silica compounds that might have locked vanadium. Milli-Q
water was boiled for 15 min to expel carbon dioxide (CO2) present in the water, then it was used
to prepare the 1 M KOH solution. Same solid to liquid ratio was used in direct caustic leaching
Same solid to liquid ratio was used in direct caustic leaching.
3.1.3. Dissolution of Ashed OSFC Using Aqua Regia
The OSFC ashing procedure was adapted from the ASTM (D4422-13) ash-forming
procedure for petroleum coke. 1.5 g of fluid coke with a particle size of 150-212 µm were dried
in an oven at 105 °C overnight and placed in a desiccator. Prior to use, chemical-porcelain
20
crucibles were placed in a muffle furnace at 750 °C for one hour for decontamination. Cleaned
crucibles were stored in a desiccator and weighed before use for leaching experiments.
To ash the OSFC, 1 g of dried coke sample was placed in a cleaned crucible, left the
sample with the crucible in the muffle furnace at 700 °C for 6 hours. Subsequently, the OSFC
ash was transferred into a centrifuge tube that contained 0.8 mL of HNO3 and 3.2 mL of HCl.
Dissolution of OSFC ash was performed in triplicate at 50 °C, 150 rpm for 24 and 48 hours.
Upon the completion of dissolution, the solution was transferred using a syringe filter (pore size:
0.45 µm) to a 10- mL volumetric flask. The syringe was cleaned with Mill-Q water twice.
Finally, make up the mixture of leaching and rinsing solution were made up to a fixed 10 mL
then further diluted by a factor of 6 for ICP analysis.
3.1.4. X-Ray Fluorescence (XRF) on Ashed OSFC
To determine the possible variations of vanadium content with particle size of fluid coke,
fluid coke samples from three different particle size ranges (53-106, 106-150, 150-212 micron)
were ashed and subjected to XRF analysis. XRF was not used directly to fluid coke, due to its
low concentration of vanadium. Moreover, a direct analysis of coke needs a carbon-based
reference material such as various certified coals (Shlewit & Alibrahim, 2006). On the other
hand, XRF has been widely used in identifying and quantifying species in ash samples
(Furimsky, 1989).
Approximately 10 g of fluid coke in each particle size range was sampled and further
grounded to be less than 38 µm then followed by an ashing process to produce ash for XRF
analysis. The ashing procedure followed the same ASTM (D4422-13) method stated in the
previous section. Ashing of fluid coke in each size range and subsequent XRF analysis were
performed in triplicate.
3.2. VANADIUM RECOVERY USING CHEMICAL ACTIVATION
High-temperature chemical activation is able to develop porous structure in coke. There
are many activating agents that are commonly used depending on the precursor, such as KOH,
NaOH, ZnCl and H3PO4. Both the amount and the type of activating agents affect to the yield
and SSA of activated coke products. For the same activating agent, a higher activating agent to
21
coke ratio results in a lower activated coke yield and normally a greater SSA (Otowa et al., 1997;
Sudaryanto et al., 2006). Although the technical feasibility of chemical activation of petroleum
coke has been established in the Green Technology Lab at the University of Toronto, the fate of
vanadium in the coke during chemical activation has not been studied. Understanding the change
of chemical states of vanadium during chemical activation is essential to the recovery of
vanadium. In this chapter, the fate of vanadium during chemical activation as well as subsequent
water washing stage is studied. Following a procedure developed at the Green Technology Lab,
chemical activation was carried out with KOH or NaOH at a hydroxide-to-carbon molar ratio of
0.5. Other details of chemical activation and subsequent water-washing procedures can be found
in the work of Zuliani et al. (2014).
Majority of the materials involved in this section was used in the previous section. Table
6 includes their properties and suppliers.
Table 6 Chemicals Involved in Chemical Activation Process
The State of
Chemicals at Room
Temperature
Material Purity Supplier
Solid
Potassium Hydroxide Pellet ≥85% Sigma-Aldrich Canada
Sodium Hydroxide Pellet ≥97% Caledon Laboratories Ltd
Fluid Coke (150-212 µm) N/A Syncrude
Hydrochloric Acid 36.5%-38% Caledon Laboratories Ltd
Liquid Methanol 99.8% Sigma-Aldrich Canada
Milli-Q Water 18.2 MΩ•cm Millipore
22
Gas N2 99.99% Peaks Scientific
3.2.1. Chemical Activation of OSFC
The experimental apparatus consisted of a stainless steel tube reactor (48 mm ID, 50 mm
OD× 200 mm Length) which was placed in a vertical tubular furnace, a gas supply system which
consisted of a mass flow rate controller attached to a nitrogen gas cylinder and a programmable
temperature controller. The flue gas created from the activation process first passes through a
condenser after exiting the reaction system, then entered a CO scrubber, and finally entered a
CO2 scrubber. The detailed set-up is shown in Figure 6.
Figure 6 Apparatus for Chemical Activation Process
Prior to the chemical activation process, the activating agent and fluid coke were
thoroughly mixed along with an addition of 0.2 mL of methanol and 5 mL of Mill-Q water for
19.5 hours in the holder. To keep a hydroxide-to-carbon molar ratio of 0.5, the amount of KOH
was 57.5 g and 36.5 g of NaOH for 25.0 g of fluid coke.
23
After soaking was completed, the holder was placed at the centre of the tubular furnace.
The system was purged with nitrogen to remove the air in it. The flow rate of nitrogen was 350
mL/min during the activation process. Before an activation started, the system was purged with
nitrogen for 20 minutes. The temperature was raised to the pre-set level at the melting point of
the activating agent. The temperature ramping rate was 5 ˚C/min. Once the temperature reached
the pre-set melting point, the temperature was held for 2 hours in order to allow metal hydroxide
to dehydrate, which stopped coke from being directly attacked by the steam from metal
hydroxide and allowed a fully penetration of coke by molten metal hydroxide (Otowa et al.,
1997). After holding for two hours, the temperature was raised again to reach 850 ˚C activation
temperature with the same ramping rate and held for 2 hours for the activation process to
complete. Within the activation, the system was protected by nitrogen purging. Upon the
completion of activation, the reactor was allowed to cool down, and the product was removed
from the furnace. The solid product was transferred to a beaker and the washing step proceeded.
3.2.2. Washing Process of Activation Product
The washing processes for KOH and NaOH chemical activated products were identical.
The washing consisted of two parts: the first part is water washing as only Milli-Q water was
introduced into the washing system. During water washing, the solid product in the beaker was
washed with 800 mL Milli-Q water with agitation for 2 hours, followed by a vacuum filtration to
separate solid and liquid phases. Eight 2-hour washings were done after the first one to reduce
alkalinity, and 600 mL of fresh Milli-Q water was used each time.
The last water washing lasted for 14 hours (overnight) to ensure a maximum dissolution
of vanadium into the washing solution. After combing all the aqueous samples in the first
washing part, the aqueous body was concentrated using a hot plate into approximately 4 L. In the
second part of the washing process, 400 mL of 20 vol% hydrochloric acid (HCl) solution was
added, and the mixture was agitated overnight to ensure the complete consumption of the
alkaline species present in the solution and all possible oxides on activated coke. After overnight
acid washing, vacuum filtration was used, and 800 ml of Milli-Q water was added and mixed for
2 hours. The procedure was repeated two more times to bring the pH value back to neutral. After
the final filtration, the solid product was collected from the filter paper and dried overnight in an
24
oven at 110 ˚C. After combing all the aqueous samples in the acidic washing part, the aqueous
body was concentrated using a hot plate into approximately 2 L. The steps in the washing
process are shown in Figure 7 below. The purpose of adding acidic washing steps was to
dissolve oxides that can possibly prevent vanadium from leaching into the aqueous phase.
While the duration of acidic washing was kept constant, the duration of each washing
stage in the water washing was then extended for 1 and 2 more hours to study the distribution of
vanadium among different activation products. The three water washing processes made the total
washing time to be 52 hours, 61 hours, and 70 hours.
25
Figure 7 The Washing Process of Activated Product for the 50Hours Washing
3.3. VANADIUM SEPARATION AND STREAM PURIFICATION
In this section, solvent extraction process was used for concentrating and purifying the
vanadium-containing stream obtained from Section 3.2. Sequential washing process was used as
26
an alternative washing process with less water consumption to achieve the goal of concentrating
vanadium in washing streams.
Many studies had used an organic solvent to extract vanadium from various sources.
Depending on the working conditions, different solvents could be applied at various pH levels.
Quaternary ammonium salts are commonly used for extracting vanadium from a basic condition.
Due to the high alkalinity of the vanadium-rich stream obtained from the water washing step
after chemical activation, a commercialized organic solvent, Aliquat® 336, which is a mixture of
C8 and C10 long-chain quaternary ammonium salts (Trioctylmethylammonium chloride and
Tridecylmethylammonium chloride), was selected to concentrate vanadium under an alkaline
condition (pH=13). The information of materials involved in this chapter is tabulated and shown
in Table 7.
Table 7 The Information of Materials Involved in Section 3.3
The State of
Chemicals at Room
Temperature
Material Purity Supplier
Solid
Potassium Hydroxide Pellet ≥85% Sigma-Aldrich Canada
Silver Nitrate ≥99% Sigma-Aldrich Canada
Potassium Orthovanadate 99.9% metals basis Alfa Aesar
Liquid
Aliquat® 336 75% Sigma-Aldrich Canada
Kerosene 99.8% VWR Canada
Nitric Acid 70%, ≥99.99%
trace metal basis Sigma-Aldrich Canada
27
1-Octanol 98% VWR Canada
Milli-Q Water 18.2 MΩ•cm Millipore
In El-Nadi, Awwad and Nayi’s study, the author also stated the importance of performing
pretreatment using 1 M KOH solution. Also, some of the experimental parameters such as
mixing time were not examined by experiments. Potassium orthovanadate salt was purchased to
perform a primary research.
3.3.1. Solvent Extraction
According to the study conducted by El-Nadi, Awwad, and Nayi for extracting vanadium
aqueous lechant obtained from spent catalyst, due to the high viscosity of Aliquat® 336,
kerosene and 1-octanol were added to obtain a 0.5 M Aliquat® 336 solvent with 10 vol% of 1-
octanol was used as phase modifier (2009). The composition of a 500 mL designated solvent is
listed in Table 8 and its calculation is present in Appendix 5.
Table 8 Chemical Composition of 0.5 M Aliquat® 336 Solvent (500 mL)
Chemical Species Volume (mL) Volume Fraction
Aliquat® 336
Kerosene
1-Octanol
280 56%
170 34%
50 10%
Another key point mentioned by El-Nadi, Awwad, and Nayi indicated that the chloride
ions present in the organic solvent would reduce the effectiveness of the solvent during
extraction. The author suggested a pretreatment process prior to extraction performed with an
alkaline solution. In the pretreatment, an equal volume of freshly prepared 1 M KOH was mixed
with the solvent and shaken for five minutes. The pretreatment was repeated several times “till
28
free of chloride ions” (2009). In this case, alkaline pretreatment was carried out 7 times. Then,
solvents with and without pretreatment were used to identify the effect of chloride ion on
vanadium extraction. The chloride ion concentration in the pretreatment raffinate was determined
by 0.1 M silver nitrate titration addressed by ASTM method (D512-12).
Solvent extraction was carried out using separation funnels; the total fluid volume was
ensured to be less than 2/3 of the total volume of the separation funnel. The solvent extraction
procedure was also modified from El-Nadi’s article. As the author stated, 15 minutes of mixing
time were sufficient. The mixing time was confirmed using synthetic feed solution of 1.1×10-2 M
K3VO4 with 0.1 M NaOH for one extraction stage with 10, 15, and 30 minutes which is shown in
Appendix 5.
As the author presented, the partition coefficient for extracting vanadium in an alkaline
medium is around 5.25 (the calculation of partition coefficient is in Appendix 6). Therefore, after
one extraction stage with an organic to aqueous ratio of 2, more than 98% of the total vanadium
in feed solution was extracted into the organic phase. The 50-hour water washing solution from
Section 3.2.2. was used to study the effect associated with the chloride ion on the separation of
vanadium (detailed results are shown in Appendix 6). Due to the low concentration of non-
hydroxide anions in the real washing solution, 0.5 M Aliquat® 336 solvent was capable of
providing more than enough positive ion sites at a 1 to 1 organic to aqueous volume ratio for a
complete extraction of vanadium anions. Therefore, the increase of organic to aqueous volume
ratio of 1 to 4 was studied. The samples of the raffinate obtained from solvent extraction with
different parameters were acidified into 5 vol% HNO3 solutions for ICP-AES analysis. Due to
the reaction of metallic alkali metal with water, alkali metal hydroxide was formed in the
washing process. The pH value of the real washing solution was about 13, which mimics the
ideal alkaline condition concluded by El-Nadi and et al for the extraction (0.1 M NaOH solution
background). However, under the high alkalinity, other elements from fluid coke that were
leached along with vanadium are likely to participate in the solvent extraction as well. Therefore,
when preparing samples for ICP analysis, trace metal basis HNO3 was used to prevent the
introduction of contaminants.
29
3.3.2. Sequential Washing Using Water
Optimization of the water usage in the washing process mentioned in section 3.2.2. was
another method used to concentrate the vanadium-containing stream. To achieve the maximal
vanadium leaching with the use of minimal amount of water, a twelve-stage sequential washing
with each stage lasting for 4 hours was conducted to ensure washing duration was identical to the
procedure presented in section 3.2.2. The washing was also carried out by another twelve stages
of 1-hour washing to determine the limiting parameter of the direct leaching. In each washing
stage, 400 mL fresh Milli-Q water was added to the activation product. Upon a completion of
one stage of washing, the solid portion was collected by vacuum filtration. The 400 mL washing
solution was transferred to a 500-mL volumetric flask. The container was then rinsed with
approximately 20 mL Milli-Q water for three times. The rinsing solutions were transferred to the
same volumetric flask. Followed by adding Milli-Q water to reach the mark of 500 mL and
stored for ICP sample preparation. The soild was then put into fresh 400-mL Milli-Q for the next
stage washing. The sequential washing was carried out at room temperature and atmospheric
pressure with a magnetic stirring bar stirring at 350 rpm. Sequential washings with different
washing durations were performed on the activation products obtained by a 0.5 sodium
hydroxide-to-carbon molar ratio.
30
CHAPTER 4. RESULTS AND DISCUSSIONS
4.1. DETERMINATION OF TOTAL VANADIUM CONTENT IN
OIL-SANDS FLUID COKE
4.1.1. Direct Leaching of Raw Fluid Coke
The direct leaching results on 150-212 µm oil-sands fluid coke using various leaching
agents are shown in Figure 8.
Figure 8 Comparison of Leaching Effect of Various Agents over 48 hours
Figure 8 shows the extracted amount of vanadium with three acids and one base. The
percentage vanadium extracted was calculated based on the assumption that total vanadium
content in the coke was 0.135 wt%. Among all the leaching agents, Aqua Regia was the most
effective in dissolving vanadium in fluid coke. However, only 0.0081 wt% of vanadium (6% of
Vtotal) was extracted even with Aqua Regia. Overall, this limited dissolution is consistent with the
existing knowledge that vanadium in coke is predominantly in the form of vanadyl porphyrins
which is a complex of vanadyl ion (VO2+) and porphyrins. In porphyrins, organic vanadium is
locked in carbon structure and unlikely to be extractable by inorganic acids.
31
The vanadium content extracted using 1 M KOH was 0.0005 wt% (0.4% of Vtotal). The
result suggests that among the inorganic fraction of vanadium, 0.0005wt% (6% of inorganic
vanadium) is associated with Si and Al. Crystals consisting of V, S, Si and Fe were discovered in
fluid coke recently (Zuliani et al, 2016). Even though there were significant amounts of Si and Al
in fluid coke, they were not the reason behind the limited dissolution of vanadium in inorganic
acid. It is interesting that both HCl and HNO3 alone were able to dissolved about 2% of
vanadium in the coke, suggesting the possibility of multiple oxidation states of inorganic
vanadium. Aqua Regia has the highest oxidation power and dissolved the greatest amount of
vanadium. In summary, vanadium in OSFC was mainly in organic forms that were not
extractable with Aqua Regia. The fraction of inorganic vanadium that was exacted via Aqua
Regia is about 6% of the total vanadium. Less than 10% of inorganic fraction was associated
with Si and Al.
4.1.2. Acid Dissolution of Ashed OSFC Using Aqua Regia
This set of experiments was carried out to determine the total vanadium content in fluid
coke. The results for Aqua Regia dissolution of ashed oil-sands fluid coke with different solid to
liquid ratios and durations are plotted in Figure 9; the error bars represent one standard deviation.
0.120 0.121 0.126 0.131
0.000
0.020
0.040
0.060
0.080
0.100
0.120
0.140
0.160
Van
ad
ium
Co
nte
nt
[wt%
]
150-212 µm
Effect of Leching Time and Solid Liquid Ratio
2ml-24hr
4ml-24hr
2ml-48hr
4ml-48hr
Figure 9 Aqua Regia Dissolution of Vanadium in Ashed OSFC with Different Solid-Liquid
Ratios and Durations
32
The highest amount of vanadium was found with 4ml of Aqua Regia after 48 hours -
0.131 wt%. Even after 48 hours with 4 ml of Aqua Regia, there was still some un-dissolved ash,
most likely silicon compounds. It is possible that some vanadium was trapped in the residual.
Therefore, it is concluded that fluid coke contained at least 0.13 wt% of vanadium. Given the
uncertainties indicated by error bars, the effects of solid/liquid ratio and duration seemed
insignificant, which was further confirmed by a T-test on 2ml-48h and 4ml-48h experiments.
4.1.3. XRF Analysis on Ashed OSFC
XRF analysis was carried out to determine the distribution of vanadium in coke particles
of different sizes. To do so, the ash content was determined following ASTM standard (D4422-
13). As shown in Table 9, the finest particles (53-106 µm) contained slightly more ash, while the
ash content of coke particles between (106 – 150 µm) and (150 - 212 µm) was insignificant.
Table 9 Ash Content of Fluid Coke Particles of Different Particle Sizes
Ash Content Particle Size Range (µm)
53-106 106-150 150-212
Avg. 3.975% 3.870% 3.850%
Std. 0.028% 0.022% 0.006%
R.Std. 0.704% 0.568% 0.156%
Figure 10 gives vanadium contents of fluid coke particles of different sizes. The
vanadium content values were calculated based on ash contents shown in Table 9 and ash
vanadium content obtained using XRF (Appendix 2).
33
Figure 10 Vanadium Contents of Fluid Coke Particles of Different Sizes
As shown in Figure 10, there seems an increasing trend in vanadium content with coke
particle size. T-test confirmed that the difference in vanadium content between 53-106 µm and
150-212 µm was statistically significant. It was noted that vanadium content values obtained
using XRF (~ 0.17 wt%) were significantly greater than those determined using ICP-AES (at
least 0.13 wt%). The discrepancy can be explained with the differences between two instruments.
XRF is a surface technique; any uneven distribution of vanadium in ash particle would result in
systematic bias. Most of the vanadium in coke is in organic form as porphyrins. During ashing
when carbon is removed by combustion, vanadium in porphyrins would likely condense or
nucleate on the surface of inorganic mineral particles. Consequently, surface vanadium
concentration would be higher than that of the bulk. This theory is consistent with the
observation that the finest particles had the greatest ash content and the lowest vanadium content
obtained with XRF. More work is needed to verify this theory. It has been reported that
nucleation, particles growth, coagulation and agglomeration could cause element enrichment on
solid sample surface (Lind, 1999).
34
4.2. VANADIUM RECOVERY USING CHEMICAL ACTIVATION
4.2.1. Activation Yield and Characteristics of Activated Coke
As shown in Table 10, yields of KOH and NaOH activation were similar. The average
yield of three KOH activations was 59%, whereas the average yield of three NaOH activations
was 61%.
Table 10 Yield of Chemical Activation and Ash Content of Activated Coke after Washing
with Water
Activating
Agent
Batch
Number
Yield
(%)
Avg. Yield
(%)
R.S.D.
(%)
Ash Content
(%)
Avg. Ash
Content
(%)
RSD
(%)
KOH
1st 61 59 2.1 0.60 0.60 20.60
2nd 59 0.73
3rd 58 0.46
1st 61 61 0.0
2.12 1.74 18.48
NaOH 2nd 61 1.85
3rd 61 1.26
The specific surface area and pore size distribution of both KOH-activated and NaOH-
activated coke were determined and shown in Figure 11 and Figure 12. The pore size distribution
results (Figure 11) show that KOH-activated coke had more micropores than NaOH-activated
coke, suggesting a stronger intercalation effect of K. Consequently, despite of the similar yield,
the SSA of KOH-activated fluid coke (1610 m²/g) was much greater than that of NaOH-activated
35
fluid coke (890 m²/g), which is consistent with the work conducted by Linares-Solano and Lillo-
Ródenas (2005).
Figure 11 Pore Size Distribution of KOH- and NaOH Activated Coke
Figure 12 Cumulative Specific Surface Area of KOH and NaOH Activated Coke
Ash contents of activated coke after washing were determined. More ash was found with
NaOH-activated coke (1.74 wt%) than KOH-activated coke (0.60 wt%), substantially lower than
36
that in the raw coke (~ 6 wt%). The low ash content in KOH-activated, water-washed coke may
be due to a greater solubility of potassium compounds in water or a deeper penetration of K that
could result in a more complete reaction with inorganic components in the raw coke.
4.2.2. Fate of Vanadium During Chemical Activation and Subsequent
Washing
OSFC was activated with KOH or NaOH and subsequently washed with Milli-Q water
for 32 to 50 hours and 20 vol% diluted HCl for 20 hours afterwards. After chemical activation
followed by water and acid washing, vanadium in coke was distributed among the four
categories: 1. washed activated coke, 2. fine particles collected in washing solution, 3. water-
washing solution: water-washable, 4. acid-washing solution: acid-extractable. The sum of parts 2
to 4 was termed “extractable vanadium content”. The sum of parts 1 to 4 is the total vanadium
recovered. The total V content (in wt%) was the total recovered vanadium amount divided by the
amount of raw coke (25 g). To determine V in washed activated coke and insoluble fines, the
washed activated coke samples were ashed, and then the ash was dissolved in Aqua Regia. All
the aqueous solutions were analyzed using ICP-AES. Table 11 and Table 12 summarizes the
amount of vanadium recovered under different activation and washing conditions.
Table 11 Fate of Vanadium after Chemical Activation and during Water and Diluted HCl
Washing (based on 25 g of Dried OSFC)
Activating
Agent
Duration
of Water
Washing
(hr)
(1) (2) (3) (4)
V in
Washed
Activated
Coke (g)
V in
Insoluble
Fines in
Washing
Solution
(g)
V in
Water-
Washing
Solution
(g)
V in
Acid-
Washing
Solution
(g)
Extractable
V(g)
Total
Recove
red
V(g)
Total
Recovered
Vanadium
Content
(wt%)
NaOH
32 0.018 0.0022 0.0062 0.0041 0.013 0.031 0.12
41 0.0084 0.00042 0.027 0.0011 0.029 0.037 0.15
50 0.00061 5.1E-05 0.036 0.000 0.036 0.037 0.15
KOH
32 0.0025 0.00013 0.011 0.023 0.034 0.037 0.15
41 0.00023 0.00016 0.022 0.015 0.037 0.037 0.15
50 5.0E-05 4.1E-05 0.036 0.000 0.036 0.036 0.14
37
Table 12 Vanadium Distribution in Each Activated Product Category in a Percentage Basis
Activating
Agent
Duration
of Water
Washing
(hr)
(1) (2) (3) (4) (2)+ (3)+ (4)
V in
Washed
Activated
Coke (%)
V in
Insoluble
Fines in
Washing
Solution
(%)
V in Water-
Washing
Solution (%)
V in
Acid-
Washing
Solution
(%)
Extractable
V (%)
NaOH
32 59.0 7.2 20.3 13.4 41.0
41 22.8 1.1 73.1 3.0 77.2
50 1.7 0.1 98.2 0.0 98.3
KOH
32 6.8 0.4 30.0 62.8 93.2
41 0.6 0.4 58.8 40.1 99.4
50 0.1 0.1 99.7 0.0 99.9
Data in Table 11 is presented as percentages in Table 12. The data above shows that
chemical activation was able to convert organic vanadium into water dissoluble inorganic species
–likely as alkali metal vanadate. At a 0.5 hydroxide-to-carbon molar ratio, NaOH and KOH were
equally capable of converting organic vanadium into inorganic vanadium. Total vanadium
extracted from OSFC was up to 0.15 wt% of OSFC. As indicated earlier, OSFC contains at least
0.13 wt% of vanadium. It is concluded that OSFC contains 0.15 wt% of vanadium. After
chemical activation, water washing alone was able to extract over 98% of vanadium in OSFC.
However, water washing was a slow process; 50 hours were needed to completely (>98%)
dissolve vanadium.
38
4.3. VANADIUM SEPARATION AND STREAM PURIFICATION
4.3.1. Solvent Extraction with Aliquat® 336
Effectiveness of the solvent is adversely affected by its chloride content. To lower the
chloride content, the solvent was pretreated with 1 M KOH up to 7 times. The raffinates
produced within the 7 pretreatments were titrated with 0.1 M silver nitrate (AgNO3) solution.
Chloride content in the solvent was determined from the cumulative amount of chloride ion in
the aqueous raffinate. The dependence of chloride removal on the number of pretreatment stages
was plotted in Figure 13.
Figure 13 Dependence of Chloride Removal from Raffinate on Number of Pretreatment
Stages
As shown in Figure 13, the cumulative amount of chloride removed increased with the
number of stages increased. After pretreating the solvent for 7 times, over 77% of total chloride
was removed from the 500 mL solvent, resulting a 0.115 M of chloride left in the solvent. Effect
of chloride content on solvent extraction efficiency was studied.
Solvent extractions were performed on the 50-hour water washing solution with
pretreated and raw solvents. The A/O volume ratio varied from 1 to 4. The result tabulated in
39
Table 13 showed that the solvent was effective in extracting vanadate from the aqueous solution
(> 90%), and less Cl- did enhance the extraction efficiency on vanadium. However, comparing
the pretreated solvent with the raw solvent, the improvement in vanadium extraction efficiency
of the pretreated solvent was rather limited, from 91% to 95%. It should be noted that lower
chloride content in the solvent is desirable in order to minimize the amount of chloride that
enters the aqueous solution during solvent extraction. As the aqueous solution after solvent
extraction needs to be recycled and reused for subsequent activation.
Table 13 Vanadium Concentrations in the Aqueous Phase upon Completion of Solvent
Extraction with Pretreated and Non-pretreated Sovlents (0.5M, A/O=1)
Samples V Concentration
(ppm)
Extraction Efficiency
(%)
Combined Water Washing Solution 0.58 -
After Extraction with Pretreated Solvent (7
times) 0.03 95
After extraction with Non-treated Solvent 0.05 91
Effects of solvent strength and A/O on the extraction efficiency were also studied.
Solvents used were 0.5 M Aliqua®t 336 in kerosene and 0.1 M Aliquat® 336 in kerosene. Both
included 10 vol% of 1-octanol and were pretreated with 1 M KOH for 7 stages. A/O volume
ratio was changed from 1 to 4. The results are shown in Table 14 and Table 15 below. As
expected, vanadium extraction efficiency decreased with the increase of A/O ratio, regardless of
solvent strength. And 0.5 M Aliquat® 336 was more effective than 0.1 M Aliquat® 336.
Interestingly, both Fe and Ni species had a greater affinity towards the organic solvent. Anions
such as vanadate and ferrate in the aqueous solution exchange with OH- in the organic solvent.
With 0.5 M Aliquat® 336 and an A/O of 1, over 90% of V, Fe and Ni was extracted into the
organic solvent. Solvent extraction with 0.1M Aliquat® 336 and an A/O ratio of 4 would retain
the bulk amount of V (94%) in the aqueous phase with 100% of Fe and 100% of Ni extracted in
the organic phase, thereby completely separating V from Fe and Ni.
40
Table 14 Concentration and Extraction Efficiency of 0.5 M Aliquat® 336 in Kerosene with
Different A/O Ratios
Concentration (ppm) Extraction Efficiency (%)
Samples V Al Ca Fe Ni Si V Al Ca Fe Ni Si
Combined Water Washing
Solution 0.58 1.21 0.09 3.85 0.13 3.32 - - - - - -
0.5M, A/O=1 0.03 0.78 0.06 0.00 0.00 0.72 94 36 25 100 100 78
0.5M, A/O=2 0.13 0.88 0.04 0.00 0.00 1.12 77 27 50 100 100 66
0.5M, A/O=3 0.23 0.88 0.08 0.00 0.00 1.19 59 28 2 100 100 64
0.5M, A/O=4 0.30 0.89 0.05 0.00 0.00 1.25 48 26 38 100 100 62
Table 15 Concentration and Extraction Efficiency of 0.1 M Aliquat® 336 in Kerosene with
Different A/O Ratios
Concentration (ppm) Extraction Efficiency (%)
Samples V Al Ca Fe Ni Si V Al Ca Fe Ni Si
Combined Water Washing
Solution 0.58 1.21 0.09 3.85 0.13 3.32 - - - - - -
0.1M, A/O=1 0.41 1.05 0.03 0.00 0.00 1.30 29 13 64 100 100 61
0.1M, A/O=2 0.48 0.99 0.07 0.01 0.00 1.30 17 18 24 100 100 61
0.1M, A/O=3 0.53 1.08 0.08 0.02 0.00 1.38 8 11 7 100 100 58
0.1M, A/O=4 0.55 1.07 0.06 0.00 0.00 1.45 6 11 29 100 100 56
4.3.2. Sequential Washing Using Water
12-stage sequential water washing of activated OSFC was carried out with two different
durations per stage (4 hours and 1 hour). The purpose of this study was to determine the
feasibility of increasing vanadium concentration and reducing water usage. Vanadium
concentrations in washing water and recovery percentages were tabulated in Table 16 and Table
17, respectively. In the tables, BDL means “below detection limit”. The recovery percentage was
calculated based on 0.15 wt% vanadium in OSFC which is equivalent to 37.5 mg of vanadium in
25 g of OSFC. The amount of water used in each washing stage was 16 mL per gram of OSFC.
41
Table 16 Vanadium Concentration and Recovery Percentage in 4-hour per Stage
Sample Concentration
(ppm)
Mass in each stage
(mg)
Recovery
percentage (%)
Stage 1 25.29 12.65 38.9
Stage 2 38.41 19.20 59.1
Stage 3 1.00 0.50 1.5
Stage 4 0.15 0.08 0.2
Stage 5 BDL BDL BDL
Stage 6 BDL BDL BDL
Stage 7 BDL BDL BDL
Stage 8 BDL BDL BDL
Stage 9 BDL BDL BDL
Stage 10 BDL BDL BDL
Stage 11 BDL BDL BDL
Stage 12 BDL BDL BDL
Total 32.43 99.8
Table 17 Vanadium Concentration and Recovery Percentage in 1-hour per Stage
Sample Concentration
(ppm)
Mass in each
stage (mg)
Recovery
Percentage (%)
Stage 1 9.70 4.95 13.2
Stage 2 58.09 29.64 79.0
Stage 3 1.13 0.58 1.5
Stage 4 0.21 0.11 0.3
Stage 5 0.12 0.06 0.2
Stage 6 BDL BDL BDL
Stage 7 BDL BDL BDL
Stage 8 BDL BDL BDL
Stage 9 BDL BDL BDL
Stage 10 BDL BDL BDL
Stage 11 BDL BDL BDL
Stage 12 BDL BDL BDL
Total 35.33 94.2
The results showed that with 4 stages of 4-hour water washing, over 99 % of total
vanadium was extracted into the aqueous phase. When the washing duration was shortened to 1
hour, the first 5 stages was able to extract over 94 % of vanadium from activated OSFC. In both
cases, most vanadium was extracted in the first two stages: 98% for 4-hour per stage and 92% for
1-hour per stage. The total amount of water used in the first two stages was 32 mL per gram of
42
raw fluid coke, whereas the water amount in previous section was 224 mL per gram of raw fluid
coke. This suggests that both the washing duration (50 hours) and the water amount (224 mL per
gram of OSFC) in previous section were excessive. The results also confirmed that acid washing
is not needed for vanadium extraction. When the washing duration per stage was shortened to 1
hour, the first five stages were able to extract over 94 % of the total vanadium from activated
OSFC. It is important to note that the first stages extracted less vanadium than the second stages,
38.9% versus 59.1% in the first two 4-hour stages and 13.2% versus 79.0% in the first two 1-
hour stages. This unusual observation might be caused by the dissolution of larger quantities of
other elements. Table 18 shows compositions of washing solutions and recovery percentage of
multiple elements during the first two washing stages (1 hour per stage). The recovery
percentage was calculated based on the corrected XRF results (Appendix 4). The results show
that the first washing stage extracted more Al, Ca, Fe, Ni and Si than the second stage, unlike V.
In the first stage, 96% of Al, 91% of Si, 76% of Ni, 42% of Fe, and 16% of Ca were found in the
aqueous solution. It is hypothesized that the lower concentration of vanadium in the first stage
washing water is due to the high Ca2+ concentration. Calcium vanadate is rather insoluble in
water and has a Ksp = 4.9 × 10−4 at 80 °C (Li, et al., 2010). Using OLI – a thermodynamic
software package, it is confirmed that calcium vanadate is the least soluble vanadium compound
and would precipitate from the washing solution if enough calcium is introduced into the
aqueous phase. Another factor that could limit the dissolution of vanadium in the first washing
stage is high concentrations of anionic species of Al, Si, Fe and Ni. The removal of other
elements in the first stage may have accelerated vanadium dissolution in the second stage and
shortened the overall washing process. More work is needed to verify this hypothesis.
Table 18 Compositions of Washing Solution and Recovery Percentage during First Two
Washing Stages (1 Hour per Stage)
1st Stage Element Recovery
Mass
(mg)
Corrected Total Amount of Element from XRF
(mg)
Recovery Percentage
(%)
V 4.95 37.50 13.20
Al 90.02 94.21 95.55
Ca 4.52 28.88 15.65
Fe 23.62 56.76 41.61
43
Ni 10.23 13.39 76.40
Si 127.38 140.03 90.97
2nd Stage Element Recovery
Mass
(mg)
Corrected Total Amount of Element from XRF
(mg)
Recovery Percentage
(%)
V 29.64 37.50 79.04
Al BDL 94.21 0.00
Ca 1.53 28.88 5.30
Fe 8.37 56.76 14.75
Ni 0.67 13.39 5.00
Si 2.14 140.03 1.53
44
CHAPTER 5. PROPOSED PROCESS OF VANADIUM
RECOVERY VIA CHEMICAL ACTIVATION ON OSFC
Based on the knowledge described in the previous chapters and the on-going work on
vanadium precipitation with Ca(OH)2 which was carried by other members of the Green
Technology Lab (Ellen Li, personal communication, Jan 4, 2017), a process of vanadium
recovery from OSFC was proposed. As shown in Figure 14, the proposed process consisted of
three main steps – 1. chemical activation with KOH or NaOH, 2. sequential water washing, and
3. calcium precipitation of dissolved vanadium.
The condition for chemical activation was described previously. After chemical
activation, all vanadium in OSFC became water soluble. Sequential water washing at ambient
temperature and atmospheric pressure would be able extract all vanadium into aqueous solution.
Over 92 % of vanadium exists in aqueous solution from first two stages of water washing.
Additional stages (the third and subsequent) might be required to further lower the impurity in
the activated OSFC. The aqueous solution from the third and subsequent stages could be
recycled for the subsequent first two stages.
In calcium precipitation step, Ca(OH)2 slurry was added into the aqueous solution from
first two stages of water washing. Upon the addition of Ca(OH)2, anionic vanadate combined
with cationic calcium to form calcium vanadate precipitates. Sufficient addition of Ca(OH)2
would allow precipitation of other anionic species of Ni, Fe, Al and Si (Ellen Li, personal
communication, Jan 4, 2017). Calcium ion addition also precipitated out carbonate and sulphate
in water washing solution. Consequently, KOH or NaOH was regenerated and reused for
chemical activation of OSFC.
45
Figure 14 Proposed Process of Vanadium Recovery from OSFC via Chemical Activation,
Sequential Water Washing and Calcium Precipitation
More work is clearly needed to determine the process conditions for vanadium separation
from the solid mixture of various calcium salts such as carbonate and sulfate. Calcium carbonate,
once purified, can be thermally converted into calcium oxide – a precursor of Ca(OH)2.
With the current production of oil-sands fluid coke (7.3 M ton per year), vanadium from
oil-sand fluid coke can be produced in 10 K ton annually, which is equivalent to an annual 0.7 M
USD value-added byproduct in bitumen refinery.
46
CHAPTER 6. CONCLUSIONS AND FUTURE RESEARCH
Conclusions drawn from this study are listed below:
1. Oil sands fluid coke (OSFC) studied contained 0.15 wt% of vanadium is predominantly in the
form of organic vanadyl porphyrins. Aqua Regia extractable, inorganic fraction of vanadium is
about 6% of the total vanadium amount. Less than 10% of the inorganic fraction is likely
associated with Si and Al.
2. During chemical activation, NaOH and KOH are equally capable of converting un-leachable
organic vanadium into water-dissoluble inorganic species-likely alkali metal vanadate. After
chemical activation, water washing alone is able to dissolve over 98% of vanadium in OSFC.
3. Sequential washing is able to shorten the duration of washing process and reduce the water
usage. First two stages of washing extracted over 92 % of vanadium in activated OSPC. Unlike
other elements (Fe, Ni, Al, Si, Ca), vanadium extraction in the first washing stage is less than
that in the second stage. This unusual behavior is tentatively attributed to the effective extraction
of Ca, Al, Si, Fe and Ni in the first stage. The dissolution of those other elements in the first
stage had limited vanadium dissolution in the first stage but enhanced vanadium dissolution in
the second stage, hence shortened the overall washing process.
4. Aliquat® 336-based organic solvent is capable of extracting vanadium from aqueous solution.
Solvent extraction efficiency increased with the strength of organic solvent and the
solvent/aqueous solution ratio. Removal of chloride from Aliquat® 336-based solvent resulted in
a small increase in extraction efficiency. Anionic species of Fe and Ni have a greater affinity
towards Aliquat® 336-based solvent. Consequently, Fe and Ni can be extracted completely from
the aqueous solution prior to the complete extraction of vanadium.
5. It is technically feasible to recover vanadium from OSFC as calcium vanadate via a multi-step
process that consists of alkali metal hydroxide chemical activation, sequential water washing and
calcium precipitation of vanadium. This process allows the recycle and reuse of KOH or NaOH
for chemical activation and produce an activated OSFC product that is highly porous (> 1500
m2/g SSA with KOH and > 850 m2/g SSA with NaOH).
47
Following recommendations are made for future research:
1. The role of solvent extraction in vanadium recovery needs to be better understood by
investigating the conditions for vanadium recovery from the spent solvent and for solvent
regeneration.
2. More work is needed to better understand the dissolution kinetics of vanadium from activated
OSFC as well as the solution chemistry. This information is needed for verifying the hypothesis
that the presence of other elements such as Ca hinders vanadium dissolution. This work could be
carried out experimentally and using thermodynamic software packages such as OLI.
3. Although an alkali metal hydroxide/carbon molar ratio of 0.5 iss able to result in a complete
vanadium recovery, a lower ratio shall be tested. A lower ratio will lead to a lower activating
agent usage and a higher yield of activated OSFC.
4. There is a need for better understanding of the formation of calcium vanadate during calcium
precipitation, for exploring options of source of calcium ions, and calcium vanadate separation
from precipitation products.
48
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53
CHAPTER 8. APPENDICES
APPENDIX 1 CALIBRATION CURVES
There were two vanadium-containing ICP standard stock solutions used throughout the
study. In Chapter 3 and Chapter 4, a single-element ICP standard solution was used for the
generation of the calibration curve. In Chapter 5, a customized multi-element ICP stock solution
was used to generate the calibration curves. The information of the calibrations are tabulated
below and the calibration curves are plotted as well.
Single-element ICP Standard Vanadium Calibration
Table 19 A Sample of Calibration for Vanadium on ICP-AES
Labels Concentration (mg/L)
Wavelength (nm)
290.88 309.31 311.837
Blank 0 14563 2099 5015.9 Standard 1 0.5 17445.5 36919 85607.9 Standard 2 1 24587 69036 161000 Standard 3 5 66001 345472 840936 Standard 4 10 117239 654642 1636856 Standard 5 20 214699 1346982 3267696
54
Figure 15 A Sample of Calibration for Vanadium on ICP-AES
Multi-element ICP Standard Vanadium Calibration
Table 20 A Sample of Calibration for Vanadium on ICP-AES
Labels Concentration (mg/L) Wavelength (nm)
290.88 309.31 311.837
Blank 0 1940.04 3148.52 13367.8
Standard 1 0.496 32748.1 20449.9 84101.8
Standard 2 0.992 66024.5 29137.6 162145
Standard 3 2.976 194763 60682.9 487340
Standard 4 9.92 646483 149251 1625358
55
Figure 16 A Sample of Calibration for Vanadium on ICP-AES
Table 21 A Sample of Calibration for Aluminum on ICP-AES
Labels Concentration (mg/L) Wavelength (nm)
308.215 394.401 396.153
Blank 0 1498.05 418.072 478.227
Standard 1 0.497 5488.85 16455.3 38335.7
Standard 2 0.994 11984.2 35799.6 79147.7
Standard 3 2.982 33856.1 102836 222406
Standard 4 9.94 107343 329581 686760
56
Figure 17 A Sample of Calibration for Aluminum on ICP-AES
Table 22 A Sample of Calibration for Calcium on ICP-AES
Labels Concentration (mg/L) Wavelength (nm)
315.887 317.933 393.366
Blank 0 -12536 4199.42 261791
Standard 1 0.505 35780.1 100706 6005296
Standard 2 1.01 81125.3 223993 1.3E+07
Standard 3 3.03 218185 608515 3.4E+07
Standard 4 10.1 677423 1895595 Sat'd
57
Figure 18 A Sample of Calibration for Calcium on ICP-AES
Table 23 A Sample of Calibration for Iron on ICP-AES
Labels Concentration (mg/L) Wavelength (nm)
238.204 239.562 259.939
Blank 0 870.437 891.843 1104.49
Standard 1 0.501 39590.9 46972 42462
Standard 2 1.002 79484.1 94314.6 84724.4
Standard 3 3.006 232140 275289 246779
Standard 4 10.02 750863 885466 799435
58
Figure 19 A Sample of Calibration for Iron on ICP-AES
Table 24 A Sample of Calibration for Potassium on ICP-AES
Labels Concentration (mg/L) Wavelength (nm)
766.49
Blank 0 10099.2
Standard 1 0.501 225920
Standard 2 1.002 608117
Standard 3 3.006 1487620
Standard 4 10.02 5311219
59
Figure 20 A Sample of Calibration for Potassium on ICP-AES
Table 25 A Sample of Calibration for Nickel on ICP-AES
Labels Concentration (mg/L) Wavelength (nm)
221.648 231.604 232.003
Blank 0 -57.36 -41.151 -434.22
Standard 1 0.4983 14224.2 17313.6 7336.16
Standard 2 0.9966 28603.9 34560.2 14659.4
Standard 3 2.9898 83288.6 99940.4 42900.9
Standard 4 9.966 268490 321870 140129
60
Figure 21 A Sample of Calibration for Nickel on ICP-AES
Table 26 A Sample of Calibration for Silicon on ICP-AES
Labels Concentration (mg/L) Wavelength (nm)
212.412 251.611 288.158
Blank 0 437.358 265.047 1567.2
Standard 1 0.503 3687.92 11816.7 5495.68
Standard 2 1.006 7072.08 22712.6 10538.6
Standard 3 3.018 19780.6 63364.2 29279.7
Standard 4 10.06 69551.6 223173 103136
61
Figure 22 A Sample of Calibration for Silicon on ICP-AES
62
Figure 23 Calibration curve for multielement standards on ICP-AES
63
APPENDIX 2 XRF RAW DATA
The XRF data is not suitable for calculating the sulfur content as sulfur can react with
oxygen involved in the ashing process and escape as a gas phase.
Table 27 XRF Analysis Results for Ashed 53-106 µm Fluid Coke
Particle Sizes Compound
Mass Fraction (wt%)
Sample 1 Sample 2 Sample 3
53-106 µm SiO2 36.11% 33.47% 37.30%
Al2O3 21.25% 19.65% 21.95%
Fe2O3 9.70% 9.73% 9.78%
V2O5 7.50% 7.53% 7.75%
SO3 6.67% 6.39% 6.58%
CaO 4.84% 4.47% 4.75%
TiO2 4.72% 4.45% 4.72%
NiO 2.09% 1.90% 2.00%
Na2O 1.98% 1.79% 1.98%
K2O 1.76% 1.68% 1.76%
MgO 1.43% 1.34% 1.51%
P2O5 0.48% 0.41% 0.49%
MnO 0.23% 0.22% 0.21%
SrO 0.17% 0.17% 0.19%
64
BaO 0.16% 0.17% 0.16%
Table 28 XRF Analysis Results for Ashed 106-150 µm Fluid Coke
Particle Sizes Compound
Mass Fraction (wt%)
Sample 1 Sample 2 Sample 3
106-150 µm SiO2 36.30% 36.80% 36.70%
Al2O3 21.41% 21.63% 21.61%
Fe2O3 9.92% 9.90% 9.95%
V2O5 7.97% 7.76% 8.00%
SO3 7.01% 7.23% 6.56%
CaO 4.81% 4.73% 4.99%
TiO2 4.69% 4.85% 4.91%
NiO 1.96% 2.03% 2.09%
Na2O 1.92% 1.87% 2.05%
K2O 1.87% 1.82% 1.78%
MgO 1.46% 1.40% 1.48%
P2O5 0.49% 0.48% 0.49%
MnO 0.21% 0.24% 0.22%
SrO 0.19% 0.21% 0.19%
BaO 0.16% 0.19% 0.14%
65
Table 29 XRF Analysis Results for Ashed 150-212 µm Fluid Coke
Particle Sizes Compound
Mass Fraction (wt%)
Sample 1 Sample 2 Sample 3
150-212 µm SiO2 36.02% 35.81% 36.62%
Al2O3 21.42% 21.37% 21.62%
Fe2O3 9.62% 9.71% 10.04%
V2O5 7.94% 7.97% 8.31%
SO3 7.02% 6.43% 6.89%
CaO 4.82% 4.92% 4.87%
TiO2 4.75% 4.82% 4.85%
NiO 2.01% 2.11% 2.05%
Na2O 1.79% 1.97% 2.03%
K2O 1.76% 1.70% 1.78%
MgO 1.43% 1.43% 1.56%
P2O5 0.48% 0.49% 0.47%
MnO 0.24% 0.26% 0.25%
SrO 0.18% 0.19% 0.20%
BaO 0.16% 0.15% 0.19%
66
APPENDIX 3 SAMPLE PELLETS OF ASHED OSFC FOR XPF ANALYSIS
Figure 24 Briquetted XRF Samples
67
APPENDIX 4 CORRECTED XRF RESULTS
In Chapter 4, the vanadium content present in fluid coke was determined using chemical
activation. The content of other elements was estimated using the factor between the vanadium
content determined by XRF and the vanadium content determined by chemical activation. A
sample calculation is shown below and the corrected contents are tabulated in Table 30.
Table 30 An Estimation of Other Elements Using Vanadium Content to Correct XRF
Results
Averaged
Oxide
Content
in Ash
(%)
Ash
Content
(%)
Element
Fraction
Element
Content
Obtained
by XRF
(%)
Element
Content
Modified
by
Vanadium
Content
(%)
Element
Weight
Present in
25 g of Raw
Coke (mg)
150-212 µm
SiO2 36.15% 3.85% 0.47 0.65% 0.56% 140.03
Al2O3 21.47% 3.85% 0.53 0.44% 0.38% 94.21
Fe2O3 9.79% 3.85% 0.70 0.26% 0.23% 56.76
V2O5 8.07% 3.85% 0.56 0.17% 0.15% 37.50
SO3 6.78% 3.85% 0.40 0.10% 0.09% 22.49
CaO 4.87% 3.85% 0.72 0.13% 0.12% 28.88
NiO 2.06% 3.85% 0.79 0.06% 0.05% 13.39
Na2O 1.93% 3.85% 0.74 0.05% 0.05% 11.85
K2O 1.75% 3.85% 0.83 0.06% 0.05% 12.02
68
APPENDIX 6 DETERMINATION OF KOH AND NAOH PELLET PURITY
Prior to chemical activation, the purity of KOH and NaOH pellets were examined by
acid-base titration. 0.1 M of HCl solution was used as the source of acid, and phenolphthalein
was used as the color indicator in this acid-base titration. The Milli-Q water used to prepare
KOH and NaOH solutions were boiled for 15 min to drive off the carbon dioxide present in the
water and then put the water into a sealed bottle for cooling down to ambient temperature.
Table 31 Purity of KOH Pellet Titration Results
Pellet Mass
(g)
Mass of KOH Calculated from HCl
Consumption (g)
Total
Amount of
Impurities
(g)
Percentage of Total
Impurity (%)
0.0694 0.0560 0.0134 19.36%
0.1080 0.0866 0.0214 19.80%
0.0975 0.0805 0.0170 17.45%
0.0627 0.0506 0.0121 19.24%
0.0398 0.0325 0.0073 18.25%
Average 18.82%
Standard
Dev. 0.85%
Pellet
Purity 81.18%
Table 32 Purity of NaOH Pellet Titration Results
Pellet Mass
(g)
Mass of NaOH Calculated from HCL
Consumption (g) (g)
Total
Amount of
Impurities
(g)
Percentage of Total
Impurity (%)
0.114133 0.1088 0.0053 4.67%
0.063429 0.0599 0.0035 5.56%
0.06039 0.0556 0.0048 7.93%
0.068176 0.0651 0.0031 4.51%
0.053933 0.0497 0.0042 7.85%
Average 6.11%
Standard
Dev 1.50%
Pellet
Purity 93.89%
69
APPENDIX 7 CALCULATION OF SOLVENT PREPARATION
In order to prepare 500 mL 0.5 M Aliquat® 336, the volume of Aliquat® 336 stock
needed is:
The volume of 1-octanol is:
The volume of kerosene is:
70
APPENDIX 8 DETERMINATION OF PARTITION COEFFICIENT AND
MIXING TIME IN SOLVENT EXTRACTION
Methodology
El-Nadi and et al. has used 0.5 M Aliquat® 336 to extract 99% of a relatively high
concentration (synthesized by 1g/L V2O5) vanadium from an alkaline aqueous (0.1 M NaOH
solution). It is mentioned in their study that 15 min is sufficient for ion exchange between two
phases. In order to confirm the mixing time, it was essential to calculate the partition coefficient
for the synthetic vanadium-bearing.
Figure 26 is the published results from El-Nadi and et al. The plot demonstrates the
correlation between the concentration of vanadium transferred to the organic phase and the
concentration of vanadium in the aqueous phase during the solvent extraction using 0.5 M
Aliquat® 336 from 0.1 M NaOH solution.
Figure 25 . Relation between the concentration of vanadium transferred to the organic
phase to that remained in the aqueous phase through the extraction by 0.5 M Aliquat® 336
71
dissolved in kerosene from 0.1 M NaOH or 3 M HCl media at 25 °C (El-Nadi and et al.,
2009)
Based on the information presented, the partition coefficient associated with their system is:
Based on the partition coefficient calculated, the fraction of vanadium (V) present in the organic
phase after one extraction with an organic to aqueous ratio of 2 is:
Therefore, one complete extraction can reach the efficiency of 91.3%.
The mixing time was confirmed using synthetic feed solution of 0.638 g/L K3VO4 with
0.1 M NaOH for one extraction. The concentration of vanadium in synthetic feed solution was
equivalent to the concentration El-Nadi used in his study with 1g/L V2O5. The synthetic feed
stock was prepared by dissolving 0.31506 g of K3VO4 into a 50-mL volumetric flask and then
diluted by 10 times, due to the difficulties involved in the precise measuring of the small amount
of vanadate salt.
72
Results and Discussions
Table 33 shows the result of a parallel experiments that keep the same of Aliquat® 336
molarity, the pretreatment time, and the organic to aqueous ratio. The result of synthetic V(V)
After one extraction with mixing time of 10 min, 15 min, and 30 min, the aqueous phases were
analyzed by ICP-AES to calculate the extraction efficiency.
Table 33 Determination of the Partition Coefficient of Synthetic System and Mixing Time
(0.5 M, A/O=2, Pretreated 7 Times)
Sample ID Concentration of
V(V) (ppm)
Mass of V
(mg)
Extraction Efficiency
(%)
Synthetic V(V) Solution
630.10 15.75
10min
2.17 0.054 99.43
15min 2.35 0.059 99.63
30min 2.35 0.059 99.63
Upon the completion of extractions, a quick pH measurement was conducted using pH
paper. It was observed that the pH of all raffinate was higher than the synthetic stock solution. In
the synthetic solution, V(V) stayed in the form of VO43- as indicated in the Pourbaix diagram of
vanadium. The VO43- ions were exchanged by OH- in the organic phase, thereby increasing the
concentration of OH- in the aqueous phase upon mixing. Also, it is proved that 15 min of mixing
is sufficient for completing the ion exchange between two phases, because the extraction
efficiency stayed the same with extending the mixing time, which hindered an equilibrium stage
was reached. Moreover, the higher extraction efficiency of one extraction indicated there’s a
larger partition coefficient associated with the system.
73
APPENDIX 9 OTHER ELEMENT CONCENTRATION IN SEQUENTIAL
WASHING
Table 34 Other Element Concentration in Sequential Washing (1hr, 5-stage)
Al Ca
Concentratio
n (ppm)
Mass in each stage
(mg)
Concentration
(ppm)
Mass in each stage
(mg)
Water Washing_Stage 1 180.03 90.02 9.03 4.52
Water Washing_Stage 2 BDL BDL 1.53 0.77
Water Washing_Stage 3 BDL BDL 1.31 0.66
Water Washing_Stage 4 BDL BDL 1.36 0.68
Water Washing_Stage 5 BDL BDL 1.43 0.72
Total 90.02 7.33
Fe Ni
Concentratio
n (ppm)
Mass in each stage
(mg)
Concentration
(ppm)
Mass in each stage
(mg)
Water Washing_Stage 1 47.23 23.62 20.47 10.23
Water Washing_Stage 2 16.75 8.37 1.33 0.67
Water Washing_Stage 3 18.63 9.32 0.35 0.18
Water Washing_Stage 4 23.20 11.60 0.23 0.12
Water Washing_Stage 5 8.41 4.20 BDL BDL
Total 57.11 11.19
Si
Concentratio
n (ppm)
Mass in each stage
(mg)
Water Washing_Stage 1 254.77 127.38
Water Washing_Stage 2 4.28 2.14
Water Washing_Stage 3 0.88 0.44
Water Washing_Stage 4 0.49 0.25
Water Washing_Stage 5 BDL BDL
Total 130.21
74
APPENDIX 10 OLI SIMULATION ON VANADIUM PRECIPITATION
In order to validate vanadium precipitation with sequential washing solution, the software
OLI Electrolyte Simulation (Build 9.3) was deployed to validate the feasibility and to simulate
the precipitation reaction. OLI Studio is capable of predicting any water chemistry mixture with
temperature -50 to 300 °C, pressure o to 1500 bar, and ionic strength 0-30 molal (OLI Systems,
2016).
In this section, both water analysis and stream were used to build the simulation models
based on different assumptions. In water analysis model, species were input in form of ions,
which assuming all input were soluble. Under this condition, the concentration obtained from
ICP were converted into their corresponding cations and anions at pH=14 according to Pourbaix
diagrams associated with each element. However, when considering activation product such as
solid carbonate, the assumption was all the activation products were complete dissolved into
aqueous phase. This assumption can be validate using the reconcile feature in water analysis. By
reconciling the input of species at a given temperature and pressure, the simulation can validate
components present in the aqueous phase. The reconciled results can be exported and used as a
stream for further analysis such as survey and single point calculation (precipitation point, vapor
point, boiling point, etc.).
The amount of carbonate produced within activation was calculated based on the
chemical activation reaction (Equation 9). Using the amount of burn-off to estimate the amount
of carbonate and metallic alkali metal produced within the activation process. In order to
simulate the washing condition at time equals to 0, concentrations of each ICP-detectable
element from first two washing stages were added as the input concentration in the simulation.
Figure 27 shows the interface of reconciliation with input of concentrations of a post-NaOH
activation sequential washing.
75
Figure 26 Interface of OLI Studio on Water Analysis and Input of Species and
Concentrations (NaOH-Activated OSFC)
As there was neither solid phase of Na2CO3 nor NaOH present in the reconciliation
results, it illustrated that the amount of water in a washing stage was sufficient to completely
react and dissolve produced metallic alkali metal and carbonate. The reconciled data was
exported as a stream and used for a simulation of vanadium precipitation shown in Figure 28
below.
76
Figure 27 Simulation Results of Vanadium Precipitation by Addition of Calcium Ion
(NaOH-Activated OSFC)
As the result shows, once 0.56 mol/L of calcium ion was introduced, vanadium would
start to precipitate as calcium vanadate.
77