Adsorption of Pb(II), EDTA, and Pb(II)-EDTA onto TiO{sub 2}
- Univ. of Maryland, College Park, MD (United States). Dept. of Civil Engineering
The adsorption of aqueous Pb(II), EDTA, and Pb(II)-EDTA complexes onto TiO{sub 2} were studied at both stoichiometric and non-stoichiometric Pb(II)/EDTA concentrations. For Pb(II)-TiO{sub 2} and ECTA-TiO{sub 2}, a typical cationic and anionic-type of adsorption was noted, respectively. For 10{sup {minus}3} and 10{sup {minus}4} M Pb(II)-EDTA systems, near-equal adsorption of Pb(II) and EDTA indicated that the complex adsorbs as a single species. Also, a ligand-type Pb(II)-EDTA adsorption, i.e., decreasing adsorption with an increase in the pH, was noted. Systems with EDTA greater than Pb(II) showed near-zero lead removal; competitive adsorption of EDTA and Pb(II)-EDTA onto TiO{sub 2} was suggested to cause this effect. For Pb(II) concentrations (5 {times} 10{sup {minus}4} and 10{sup {minus}3} M) higher than EDTA (10{sup {minus}4} M), significantly higher EDTA adsorption at high pH as compared to individual 10{sup {minus}4} EDTA and 10{sup {minus}4} M Pb(II)-EDTA systems was noted. Adsorption modeling was completed employing the geochemical speciation model MINTEQA2 employing the diffuse layer model. Inner-sphere complexation was considered to occur between Pb(II), EDTA, Pb(II)-EDTA, and the TiO{sub 2} surface sites. Surface complexes used in the modeling included Ti-O-Pb{sup +}, Ti-EDTAH{sup 2{minus}}, Ti-EDTA-Pb{sup {minus}}, and Ti-O-Pb-EDTA{sup 3{minus}}. The cationic-type complexation, Ti-O-Pb-EDTA{sup 3{minus}}, was postulated to explain and model the anomalous EDTA adsorption as noted for Pb(II) > EDTA studies. Results from the present study show that the adsorption behavior in aqueous metal/EDTA systems will change with any variation in the contaminant concentration ratios.
- OSTI ID:
- 605717
- Journal Information:
- Journal of Colloid and Interface Science, Vol. 198, Issue 1; Other Information: PBD: 1 Feb 1998
- Country of Publication:
- United States
- Language:
- English
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