nanoscale analysis for designing nanomaterials for ... · tem, xps, xrd, mossbauer) experiments:...
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Nanoscale Analysis for Designing
Nanomaterials for Environmental Applications
John Crittenden1, Yongsheng Chen1,
Xiaoyang Meng1, Yue Peng1, Jinming Luo1, Guangshan Zhang1,
Wen Zhang2, Junfeng Niu3, Qizhou Dai4
1. Brook Byers Institute for Sustainable Systems, School of Civil and Environmental Engineering, Georgia Institute of Technology
2. John A. Reif, Jr. Department of Civil and Environmental Engineering, New Jersey Institute of Technology
3. State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University
4. College of Biological & Environmental Engineering, Zhejiang University of Technology
Frontiers of Chemical Science and Engineering Conference Feb 24 – 26, 2016 Beijing, China
Nanomaterial
Design
Adsorbent,
Catalyst
Design
Reactor
Design
Process
Design
Microcalorimetry:
Heat of adsorption,
Coverages, Desorbing
species
Spectroscopy:
(e.g., infrared for
surface species,
TEM, XPS, XRD,
Mossbauer)
Experiments:
• Kinetics (e.g., activity,
selectivity, stability,
oxidation efficiency)
• ROS identification for
nanoscale oxidation:
• ESR (Electron Spin
Resonance) detection
of (HO∙), 1O2 and (O2∙-)
• Voltammetry
• Hg & N2 porosimetry
Thermodynamics:
Evaluate Reaction
Possibilities
Crystallinity and band
gap engineering
Theoretical methods:
• Quantum-chemical studies electronic
structure of stable species,
intermediates and transition state.
• DFT (e.g., band gap calculations,
binding energy).
• CFD: DFT to CFD.
Nanomaterial Design Cases
Fabricate metal doped PbO2 anodes for electrochemical
oxidation of organic contaminates.
Fabricate visible light responsive photocatalyst for selective
reduction of chlorinated organic contaminates in water.
Fabricate visible light photocatalysts with tunable band gaps
and small crystallite sizes to produce H2.
Fabricate ZrO2 impregnated carbon nanofibers to adsorb
Antimony from aqueous solution.
Fabricate selective catalytic reduction Sr-doped LaMnO3
catalyst for removal of NOx from power plants and understand
their fouling and regeneration mechanisms.
3
1. Electrooxidation Processes
Fabricate metal doped PbO2 anodes for electrooxidation of organic
contaminants
Anodes Doping Metal Elements
Band Gap Engineering & DFT
Anode Fabrication Characterization
(e.g., XRD, XPS)
Experimental Verification
Electrochemical Oxidation Fabricate Gd, La-doped PbO2 anode for oxidation of
p-toluenesulfonic acid (p-TSA)
Abundance of the chemical elements http://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements
Gd La
6
Band Gap Engineering
Objective:
Hydroxyl radical (HO∙) production by electrochemical oxidation.
Procedures:
1.Use DFT calculation to calculate the Projected Density Of Function (PDOS) of
suspect material candidates and determine the band gap.
2.Convert PDOS results (vacuum scale) to normal hydrogen electrode (NHE)
scale and compare with the reduction potential of hydroxyl radical (HO∙), 2.8 V.
3.Use the proper material as the anode to create (HO∙) and minimize byproducts,
e.g., O2, O3, H2O2.
Ideally, we want every electron create one HO∙!
7
Band Gap Engineering
Half reactions:
O2:
H2O2 :
O3 :
SO4·-:
HO:
h+:
2 22 4 4H O O H e
2 2 22 2 2H O H O H e
2 2 3 2 2O H O O H e
2
4 2 82SO S O e
E°(V)
-1.23
-2.07
-1.77
-2.43
-2.80
>3.00
2H O HO H e
h e Anode
Geometry
optimization for
electrodes
(1)PbO2,
(2)(2) La-PbO2,
(3)(3) Gd-PbO2
O: red balls,
Pb: gray balls,
La:blue ball,
Gd:green ball
DFT & Band Gap Engineering
0
1
2
0
1
-10 -5 0 50
1
d oribitals
p orbitalsPbO
2 (110)
(a)
(c)
(b)
Gd-PbO2 (110)
La-PbO2 (110)
PD
OS
(sta
tes/e
V)
Energy (eV)
Projected density of states of surface Pb atom on (a) PbO2 (110),
(b) La-PbO2 (110) and (c) Gd-PbO2 (110) planes
Fermi Level
Bottom of Conduction Band Top of Valence Band
4 V
7 V
6 V
Characterization: XRD, All Peaks are Beta-PbO2
20 30 40 50 60 70 80
0
1000
2000
3000
4000
5000
6000
700020 30 40 50 60 70 80
0
1000
2000
3000
4000
5000
6000
7000
(400)(321)(301)
(310)
(220)(211)
(200)
(101)
(110)
(b) La-Gd-PbO2
co
un
ts
(A)
(400)(321)
(301)
(220)
(310)
(211)
(200)
(101)(110)
2(o)
2(o)
(a) PbO2
co
un
ts
X-ray diffraction patterns of (a) PbO2, (b) La-Gd co-doped PbO2
Doped PbO2 have greater
crystalinity. Size=34.42 nm
and more active sites.
Crystal size=60.97 nm
147 145 143 141 139 137 135
(B)(a) PbO2
(b) La-Gd-PbO2
Binding energy (eV)
Characterization: Binding Energy
XPS separation spectrum of Pb 4f in PbO2 electrode and La-Gd-doped PbO2 electrode
the ratio of Pb2+/Pb4+
for La-Gd-PbO2
electrode was 3.53,
which was slightly
larger than that of
PbO2 (2.78),
More redox couples
for
Doped PbO2
Electrochemical Experiment Results
Influence of the different PbO2 electrodes on the removal of p-TSA.
(Initial p-Toluenesulfonic acid concentration=500 mg L-1, current density=30 mA cm-2, electrolyte
concentration (Na2SO4)=0.1 mol L-1)
0 20 40 60 80 100 120 140 1600
20
40
60
80
100
Pb:Gd:La=200:0:0
Pb:Gd:La=200:4:0
Pb:Gd:La=200:3:1
Pb:Gd:La=200:2:2
Pb:Gd:La=200:1:3
Pb:Gd:La=200:0:4
C/C
0 1
00
(%
)
Time (min)
13
Characterization: Spectroscopy
TiO2-based SnO2-Sb/Polytetrafluoroethylene
Resin (FR)-PbO2 anode
SEM of (a). TiO2-NanoTubes Substrate, (b). SnO2-Sb intermediate
layer, (c). FR/PbO2 electrode
a)
100
nm
b)
20
µm
c)
10
µm
Linear sweep voltammetry (LSV) of the TiO2-based SbO2-Sn/FR PbO2 electrode for a 0.5 M
H2SO4 solution. Scan rate is 10 mV/s. The standard reduction potentials (pH=0) for O2, H2O2,
S2O82-, O3 SO4·-, and HO· are +1.23 V, +1.77 V, +2.01 V, +2.07 V, +2.60 V and +2.74 V.
Band Gap Engineering
(a) ofloxacin destruction for various current densities (b)
pseudo-first-order rate constants (c) EE/O. Anode surface
area 10 cm2, electrode spacing 1 cm, fluid velocity 0.033
m/s, initial ofloxacin concentration 20 mg/L, voltage 3.5-
8.6 V, electrolyte concentration is 0.05 M Na2SO4, pH
value 6.25 and temperature is 25 ℃.
Energy efficiency per order:
Electrochemical Experiment Results
16
Electron efficiency:
The oxidation efficiency for 20
mg/L ofloxacin with TiO2-based
SnO2-Sb/Polytetrafluoroethylene
Resin (FR)-PbO2 anode at current
density 30 mA/cm2 is 88.45%.
Electrochemical Experiment Results
17
Differential Column Batch Reactor (DCBR)
• The solution flows through the reactor.
• Due to recirculation of the solution, the reactor acts like a batch reactor.
• Reaction models can be used for fitting the kinetic curves and evaluating
the mass transfer coefficients.
19
Mass Transfer Studies
Effectiveness factor in different fluid velocity and the best
fitted model. Anode surface area 10 cm2, electrode spacing 1
cm, electrolyte 0.05 M Na2SO4 solution, current density 30
mA/cm2, initial ofloxacin concentration 20 mg/L, voltage
6.3-6.4 v, pH value 6.25, temperature 25 ℃.
l
d u
20
Full Scale Reactor Design
Rough Design of Reactor (top view):
1 2 3 4 5 6 7 8 9 10
10.5 meters
long
10 meters
electrodes
10 meters
2 meters deep
Reactor Channel
1 meter
…......
5 cm 95 cm
Bench Scale to Pilot Scale: CapEx & OpEx
The total costs (capital costs + energy costs) as a function of different electrode spacing for different theoretical
reaction rate. In here, the treatment objective is 99% removal, flow rate is 1000 m3/day and the fluid velocity is
0.0116 m/s. The flow channel has eddy promoter and its electrode spacing and obstacle distance ratio is 1/3. The
electricity price is $0.0512/kWh and the pumping power is 8.53 kW. The electrode price is $300/m2 and its lifetime
is 2000 h.
22
Electrochemical Oxidation Technology Case
Coking Waste Water
Capacity: 3600 m3/day
Influent Effluent OpEx
COD (mg/L) 90 ~ 180 < 50
5 – 8 kWh/m3
NH3-N (mg/L) 4.8 < 1
Total CN- (mg/L) 0.85 0.02
pH 8.35 7.8
23
Chemical Plant
Capacity:600 m3/day
Influent Effluent OpEx
COD (mg/L) 360-400 < 50
15 kWh/m3 NH3-N (mg/L) 1.86 < 0.5
TOC 110-137 < 17
pH 8.7 8.0
CASE STUDY: RO CONCENTRATE
24
Chemical Plant
Capacity:1200 m3/day
Influent Effluent OpEx
COD (mg/L) 60 < 30
4 kWh/m3
pH 8.5 8.1
CASE STUDY: RO CONCENTRATE
25
Chemical Plant in Hebei
capacity:800m3/day
Influent Effluent OpEx
COD (mg/L) 120~150 < 50
6 kWh/m3 NH3-N (mg/L) 5.2 < 1
Total CN-
(mg/L)
0.08 < 0.01
pH 9.12 7.2
CASE STUDY: COKING WASTE WATER
REUSE
26 Kingboard Chemical Holdings Ltd. (Heibei Provence, China)
Full Scale Reactor in the Field Coking and Char Waste Water Treatment
COD: influent ~150 mg/L
effluent < 50 mg/L Flow rate: 432 cu. meters/day
27
Influent Effluent OpEx
COD (mg/L) 128 < 50
6 kWh/m3
pH 8.12 7.8
BENCH SCALE: REFINERY RO
CONCENTRATE
Daqing Petrochemcial Plant, China
2. Photocatalytic Reduction Processes
Design of visible light responsive photocatalysts for selective reduction
of chlorinated organic compounds in water
Adsorption Potential Photoabsorptivity Photoreactivity
DFT & Band Gap
Engineering
Experimental
Verification
β-Bi2O3 Photocatalyst
Pentachlorophenol (PCP)
using Ti-β-Bi2O3
Trichloroethylene (TCE)
using Sr-β-Bi2O3
γ-Hexachlorocyclohexane(HCH)
using Zr-β-Bi2O3
32 doping elements
3. Photocatalytic Hydrogen Gas (H2) Production
Photocatalytic H2 Production Processes
Fabricate visible light photocatalysts with tunable band gaps and small
crystallite sizes to produce H2
Photocatalyst (CuAg)xIn2xZn2(1-2x)S2
Band Gap > 1.23 eV
Characterization(e.g., XRD)
Experimental Verification
Suitable Band Levels High Crystallinity
Photocatalyst Fabrication Theoritical Calculation
Mechanisms of H2 Evolution
Ru
IO3‾ or I3‾
I‾
H2
H+
e-
h+
1.9 eV
(CuAg)0.15In0.3Zn1.4S2
(Photocatalyst)
V.B.
C.B.
hν
Two potential oxidation half-reaction pathways:
(2)
+ -
22H +2e H
Reduction half-reaction:
Overall reaction (a and b are variables and ≥0):
(pH>9)
(pH<5) (1) +
33I +2h I
+
23 3H OI +6OH 6h IO
2 23 33 +2 )H O ( ) (3 + )H( +3 )I ( ( )IO I (2 )OHa b b a ba b a b
Proposed reaction mechanism for H2 production using the
Ru/(CuAg)0.15In0.3Zn1.4S2 photocatalyst and KI as the electron donor.
Guangshan Zhang, Wen Zhang, Yongsheng Chen, and John Crittenden. pH effects on kinetics of H2 production by the photocatalyst
((CuAg)0.15In0.3Zn1.4S2) in aqueous solution under visible light irradiation. International Journal of Hydrogen Energy. Accepted.
Characterization: Different Band Structures at Different Molecular Ratios
Band structures of the (CuAg)xIn2xZn2(1-2x)S2
photocatalysts in contact with aqueous solution at
pH 2.0. The lower edge of ECB (red) and upper
edge of EVB (blue) are presented along with the
band gap in eV. On the right side the redox
potentials of redox couples (H+/H2 and I−/I2) are
presented.
The CB edge potential (ECB) of the obtained
(CuAg)xIn2xZn2(1-2x)S2 in relation to the
normal hydrogen electrode potential (NHE)
can be calculated by
where X is the absolute electronegativity of a pristine
semiconductor, x is the electronegativity of a neutral
atom, A is the atom electron affinity, I is the first
ionization energy, E0 is the energy of a free electron
on the hydrogen scale (~4.5 eV), and Eg is the
semiconductor band gap energy (eV).
Different Photocatalytic Activity at Different Molecular Ratio
(a) Time course of H2 production (b) the photocatalytic H2 production rate over
(CuAg)xIn2xZn2(1-2x)S2 (x = 0–0.5) photocatalysts under visible-light irradiation.
X=0.15 were chosen as the optimized value for
(CuAg)xIn2xZn2(1-2x)S2 photocatalyst with the highest H2 production yield.
Good
46
4. Antimony Adsorption Processes
Fabricate ZrO2 impregnated carbon nanofibers to adsorb Antimony from
aqueous solution
Zirconium Dioxide (ZrO2) 23.45mg/g for Sb(III)
22.64mg/g for Sb(V)
Carbon Nanofibers
Adsorbent Characterization
(e.g., XRD, XPS, DFT
calculation)
Adsorbent Properties Analysis
(e.g., kinetic, isotherm)
Zirconium Dioxide Carbon Nanofibers 70.83mg/g for Sb(III)
57.17mg/g for Sb(V)
49
tetrahedral-ZrO2 (111)
monoclinic-ZrO2 (111)
Ead=1.13 eV
Ead=0.76 eV
Sb(III) absorbed
Sb(III) absorbed
Adsorption Energy via DFT Calculation
51
Adsorption Energy via DFT Calculation
t-ZrO2 (111)
m-ZrO2 (111) Ead=3.35 eV
Sb(V) absorbed
Sb(V) absorbed
Ead=6.07 eV
SEM SEM-Mapping
Adsorption Isotherms
Adsorption Isotherm for a. Sb (III) b. Sb (V)
56
Selective Catalytic Reduction(SCR)
Diesel engine Power Plant NOx
N2
NH3
catalysts
5. Selective Catalytic Reduction (SCR) for Removal of NOx
Fabricate selective Ce-doped catalytic reduction catalyst for removal of NOx from
power plants and solve catalyst poisoning from alkali metals.
N. Topsoe Science 1994, 265, 1217.
Summary
An rational design approach for nanomaterial
fabrication has been proposed and its utility has
been shown.
Three case studies have illustrated its application
for designing electrodes and catalysts.
Theoretical calculation (e.g. DFT) is useful to
guide material selection.
Acknowledgment
• Georgia Tech College of Computing, Office of Information
Technology and CEE IT Services for high computational
resources.
• Georgia Tech CEE Daniel Laboratory colleagues.
• Brook Byers Institute for Sustainable Systems.
• High Tower Chair and Georgia Research Alliance at Georgia
Tech.
• New Jersey Institute of Technology department of civil &
environmental engineering.
• Beijing Normal university State Key Laboratory of Water
Environment simulation.
• Zhejiang University of Technology college of biological &
environment engineering.
References
• Yue Peng, Kezhi Li, and Junhua Li, 'Identification of the Active Sites on Ceo2–Wo3 Catalysts for
Scr of Nox with Nh3: An in Situ Ir and Raman Spectroscopy Study', Applied Catalysis B:
Environmental, 2013. 140-141 483-92.
• Dai, Q., et al., Catalytic ozonation for the degradation of acetylsalicylic acid in aqueous solution
by magnetic CeO2 nanometer catalyst particles. Applied Catalysis B: Environmental, 2014. 144:
p. 686-693.
• Nickson, R., et al., Arsenic poisoning of Bangladesh groundwater. Nature, 1998. 395(6700): p.
338-338.
• Peng, Y., et al., Alkali metal poisoning of a CeO2-WO3 catalyst used in the selective catalytic
reduction of NOx with NH3: an experimental and theoretical study. Environ Sci Technol, 2012.
46(5): p. 2864-9.
• Peng, Y., et al., Experimental and DFT studies on Sr-doped LaMnO3catalysts for NOxstorage and
reduction. Catal. Sci. Technol., 2015. 5(4): p. 2478-2485.
• Zhang, G., et al., Effects of inorganic electron donors in photocatalytic hydrogen production over
Ru/(CuAg)0.15In0.3Zn1.4S2 under visible light irradiation. Journal of Renewable and
Sustainable Energy, 2014. 6(3): p. 033131.
• Zhang, W., et al., Photogeneration of reactive oxygen species on uncoated silver, gold, nickel, and
silicon nanoparticles and their antibacterial effects. Langmuir, 2013. 29(15): p. 4647-51.
• Zhang, G., et al., pH effects on kinetics of H2 production by the photocatalyst
((CuAg)0.15In0.3Zn1.4S2) in aqueous solution under visible light irradiation. International
Journal of Hydrogen Energy. 2013. 38, 27: 11727-11736.