Download - Synthesis of Polyoxometalates
SYNTHESIS OF KEGGIN AND SANDWICH-TYPE POLYOXOMETALATES FOR ENVIRONMENTAL APPLICATIONS
Katherine Aldrich
Hang Zuo
Northeastern University, Boston MA
Chemical Engineering
NORTHEASTERN SUMMER EXCHANGE Previous Internships at Genzyme Corporation and Waters Corp.
Genzyme-Biologics and Biological Engineering
Waters-Process Engineering
New in-sight into a different area of Chemical Engineering
Upon returning to Boston, internships at Alkermes and Henkel
Use experience gained at NTU in Material Science to apply in industrial
setting
ENVIRONMENTAL CONCERN: WASTE WATER1,2
River polluted with red dye1 Clean Lake2
ENVIRONMENTAL CONTAMINANTS3
Phenol
Azo Dyes
Sulfur containing compounds
WET AIR OXIDATION (WAO)
Oxygen oxidizes organic compounds into carbon dioxide and water
High Temperatures and Pressures
High Operating Costs
Used for waste streams that cannot be burned or undergo
biological treatment4
CATALYTIC WET AIR OXIDATION (CWAO)
Addition of a catalyst
Reaction takes place under milder temperatures and pressures
Two types of heterogeneous catalysts
-Transition Metal Oxides (Fe, Sn, Mn)
-Supported Nobel Metals (Pt, Pd, Ru)
Major advantages of CWAO are lower operating costs and
increased degradation of organic pollutants4
PROBLEMS WITH CWAO
Three Major Problems
1. High Cost of Noble Metals
2. Incomplete Oxidation of Phenols to Carbon Dioxide
-Intermediate products can be more toxic than original pollutant
3. Catalyst Deactivation
These three problems have prevented successful implementation of CWAO
Need for stable and recyclable catalyst4
POLYOXOMETALATES AS A CATALYST
Transition metal oxide clusters in the highest
state of oxidation
Includes Mo (VI), W (VI), and V (V)
Well-defined structures
-Keggin Type POM
-Sandwich Type POM4
Keggin Structure of (H5PV2Mo10O40 )5
PROBLEMS WITH POMS AS CATALSYTS
Low surface area
High solubility in water
Results in
-Low Efficiency
-Inability to recycle catalyst
-Toxic Waste Generation
Goal: Generate an efficient and recyclable catalyst using POMs6
SURFACTANTS AND MICELLES
Spontaneously form micelles
Water concentration decreases from the
surface to the core
Completely hydrophobic core
Surfactant outer layer and POM core
POM is in a completely water free zone6
Water concentration decreases from the outer layer to the core7
PURPOSE1. Synthesis Polyoxometalates H5PV2Mo10O40 and Na12[WZn3(H2O)2(ZnW9O34)2]
2. Addition of surfactant CTAB to H5PV2Mo10O40
3. Characterization using SEM, XRD, FTIR, UV-VIS, TGA and GC-MS.
Scanning Electron Microscope (SEM)
SYNTHESIS OF POLYOXOMETALATES Molybdovanadophosphoric acid (H5PV2Mo10O40)
Zinc(II)-Substituted POM (Na12[WZn3(H2O)2(ZnW9O34)2])
Simple procedure, but difficult to synthesize
NaZnW POM was synthesized multiple times
H5PV2Mo10O40 NaZnW POM
SYNTHESIS OF H5PV2MO10O40
1. Sodium Metavanadate
2. Disodium Phosphate
3. Sulfuric acid
4. Sodium molybdate dihydrate
Extracted using ethyl ether
Washed, filtered and allowed to crystalize8
Extraction Flask for POM using Ethyl Ether
SEM IMAGE AND EDX OF H5PV2MO10O40
FTIR ANALYSIS OF H5PV2MO10O40
• Band at1060 is the P-O vibration• 958 is M-O• 866 is inter-octraheral M-O-M• 784 is the intra-octrahedral M-O-M• Water bands at 3400cm-1 and 1620cm-14
THERMOGRAVIMETRIC ANALYSIS (TGA)
From 50-100°C, most of the water evaporated
Very little water attached to the crystal
XRD OF H5PV2MO10O40
XRD From Literature4
Experimental XRD
ADDITION OF CTAB TO H5PV2MO10O40
Cetyltrimethyl ammonium bromide(CTAB)
Micelles trap environmental contaminants
High concentration of substrate near the POM
FTIR OF CTAV2
Note the lack of water band at 3400cm-1
CATALYTIC ACTIVITY OF CTAB AND H5PV2MO10O40
Structure of Reactive Black 5 Dye
• Measured the catalytic activity of CTAV2
• 9.2E-4M CTAV2 (0.3 g)
• Sulfur-containing Reactive Black 5
• Mixed solid CTAV2 with liquid Reactive Black 5 (25 ppm,
100 mL)
• Samples at 0min, 3 min, 10 min, 20 min, 30 min, 45
min, 60 min, 90 min and 120 min
• Analyzed with UV-VIS Spectroscopy
UV-VIS GRAPH FOR REACTIVE BLACK 5 DYE DEGRADATION
• Blue light has a wavelength of 475
nm
• Red light has a wavelength of 650
nm
• Rapid absorbance of dye into CTAV2
• Within 10 min, absorbance
decreases from 0.45 to 0.17
• No change after 45min
REACTIVE BLACK 5 DYE REMOVAL
At 30 min, 95% of the dye has been removed from solution
Point of catalyst saturation
After 30 min, the percent of dye removal decreases to 85%
Some dye was released from catalysts resulting in a decrease of dye removal
Stabilizes after 90 min
1. Sodium Tungstate Dihydrate
2. Nitric Acid at 80-85°C
3. Zinc Nitrate Hexahydrate
Filtered and allowed to crystalize
Needle-shaped crystals9
Synthesis of NaZnW POM (Na12[WZn3(H2O)2(ZnW9O34)2])
Drop by drop addition of nitric acid
SEM IMAGES
Batch 1 Batch 2 Batch 3
Batch 2 Batch 3
EDX of Zn POM
Batch 2
XRD of
Na12[WZn3(H2O)2(ZnW9O34)2]
)
Batch 3
XRD of
Na12[WZn3(H2O)2(ZnW9O34)2]
)
FTIR ANALYSIS
• Peak at 1384 is NO3
• Batch 2 failed
• Broad peak at 1384cm-1 for
Batch 2
• POM was not fully synthesized
as reactant NO3 is still present
Thermogravimetric Analysis (TGA) of NaZnW POM
9.3%
2.5%
• Between 50-100°C, free water
evaporated
• Between 100-300°C, water that was
bonded to the crystal evaporated
• Sharp drop at 350°C indicates
breakdown on POM structure
CONCLUSIONS
H5PV2Mo10O40 was successfully synthesized and the characterization
aligned to literature results
CTAV2 removed 90% of dye from solution
Temperature and pH greatly effects synthesis of Zinc(II)-Substituted POM
Only Batch 3 Zinc(II)-Substituted POM was successful
ACKNOWLEDGEMENTS
We would like to thank Professor Webster for organizing this exchange with NTU and also Professor Dong Zhili for agreeing to
host us in his lab.
A very special thank you to Yao Lei and Shun Kuang. They were incredibly helpful in running experiments and also in introducing us to the Singapore Culture. The experience would not have been the
same without them.
REFERENCES
1. Daily Mail. “The River That Did Run Red.” 2012. http://www.dailymail.co.uk/news/article-2199800/The-river-DID-run-red-Residents-Chinese-city-left-baffled-Yangtze-turns-scarlet.html
2. US EPA. EPA’s Clean Lake Program. 2013. http://water.epa.gov/type/lakes/cllkspgm.cfm3. Sigma-Aldrich. http://www.sigmaaldrich.com/singapore.html4. Zhao,S. Wang, X. “Catalytic wet air oxidation of phenol with air and micellar molybdovanadophosphoric
polyoxometalates under room condition.” Elsevier Journal. l 97 (2010) 127–1345. Arichi, J. Pereira, M. Synthesis of Keggin-type polyoxometalate crystals. Solid State Sciences. Elsevier Journal. (2010)
1866–18696. Shah,A. Mujahid, A. “Micelle directed synthesis of (C19H42N)4H3(PW11O39)nanoparticles and their catalytic
efficiency for oxidative degradation of azo dye.” J Sol-Gel Sci Technol (2012) 63:194–1997. Centre For Distance Engineering Education Programme. 2013.
http://www.cdeep.iitb.ac.in/nptel/Core%20Science/Engineering%20Chemistry%201/Slide/lect1/1_5.htm
8. TSIGDINOS , G. HALLADA, J. Molybdovanadophosphoric Acids and Their Salts. I. Investigation of Methods of Preparation and Characterization.” Apvil 3, 1967
9. Lai, G. Luo, J. “Zinc-Substituted Polyoxometalate for Oxidative Desulfurization of Dibenzothiophene.” Petroleum Science and Technology. 19 May 2014