عنوان

Adsorption and photocatalysis of Pb(II)-ligand complexes in TiO(2) suspensions

Number

TLpq304433649

.Language of Text, Soundtrack etc

انگلیسی

Title Proper

Adsorption and photocatalysis of Pb(II)-ligand complexes in TiO(2) suspensions

General Material Designation

[Thesis]

First Statement of Responsibility

M. S. Vohra

Subsequent Statement of Responsibility

A. P. Davis

Name of Publisher, Distributor, etc.

University of Maryland, College Park

Date of Publication, Distribution, etc.

1998

Specific Material Designation and Extent of Item

185

Dissertation or thesis details and type of degree

Ph.D.

Body granting the degree

University of Maryland, College Park

Text preceding or following the note

1998

Text of Note

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.

Adsorption

Applied sciences

Lead

Photocatalysis

Titanium oxide

Wastewater treatment

A. P. Davis

M. S. Vohra

Electronic name

p

[Thesis]

276903

a

Y