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" Adsorption and photocatalysis of Pb(II)-ligand complexes in TiO(2) suspensions "
M. S. Vohra
A. P. Davis
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Latin Dissertation
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English
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| Record Number
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1113475
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| Doc. No
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TLpq304433649
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| Main Entry
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A. P. Davis
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M. S. Vohra
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| Title & Author
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Adsorption and photocatalysis of Pb(II)-ligand complexes in TiO(2) suspensions\ M. S. VohraA. P. Davis
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| College
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University of Maryland, College Park
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| Date
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1998
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| student score
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1998
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| Degree
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Ph.D.
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| Page No
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185
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| Abstract
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Industries such as nuclear and electroplating often generate wastewater containing toxic metals such as lead and organic ligands such as EDTA. Complexed aqueous metal species, such as Pb(II)-EDTA, are difficult to treat employing conventional metal removal methods. The present work investigated the adsorption and photocatalysis of lead-ligand complexes in TiO2 suspensions. Results from the Pb(II)-only and EDTA/NTA-only adsorption studies showed a cationic- and an anionic-type adsorption, respectively. Adsorption modeling results predicted similar trends. The 10 and 10 M Pb(II)-EDTA studies indicated an anionic-type Pb(II)-EDTA adsorption, i.e., Ti-EDTA-Pb. However, the Pb(II)-NTA adsorption studies showed an increasing lead and decreasing NTA removal with an increase in pH. For the EDTA > Pb(II) studies, insignificant metal adsorption was noted between pH 2 and 10, whereas some EDTA adsorption occurred. Studies completed at Pb(II) > EDTA/NTA showed significant ligand adsorption even at high pH, which was not noted for the ligand-only adsorption studies. Additional surface species, i.e., Ti-O-Pb-EDTA, and Ti-O-Pb-NTA, were invoked to explain and successfully model such an enhanced ligand adsorption. These results indicate that adequate adsorption modeling of metal-ligand species needs to consider both anionic- and cationic-type surface complexation. Also, sub-surface transport modeling of such contaminants would also need to incorporate both surface species. Pb(II)-EDTA photocatalysis was completed at several Pb(II)/EDTA concentrations and pH 4 to 6. 10 M Pb(II)-EDTA photocatalysis studies showed complete complex destruction within 20-min, and 10 M Pb(II)-EDTA systems within 1-hr. Acetate, formate, formaldehyde, ammonia, and nitrate were detected as reaction intermediates and products. CO2 production was also noted. Results from stoichiometric studies showed no significant pH effects on Pb(II)-EDTA photocatalysis. However, Pb(II) > EDTA studies at pH 6 showed decreased CO2 formation compared with the studies at pH 4 due to Pb(II) adsorption. Trends from the stoichiometric and non-stoichiometric studies indicated that Pb(II)-EDTA photocatalysis is both a surface and solution process. Generally, results from the present study indicate that TiO2-assisted photocatalysis can be employed to treat contaminated waters containing lead-ligand species.
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Adsorption
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Applied sciences
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Lead
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Photocatalysis
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Titanium oxide
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Wastewater treatment
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