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Title: Competitive adsorption of Cu(II)-EDTA and Cd(II)-EDTA onto TiO{sub 2}

Abstract

Cu(II), EDTA, Cu(II)-EDTA, Cd(II)-EDTA, and Cu(II)/Cd(II) and Cu(II)-EDTA/Cd(II)-EDTA competitive adsorption onto TiO{sub 2} has been studied with variation of pH and concentration. For Cu(II) and EDTA, typical cationic and anionic types of adsorption are noted, respectively. Ligand-type adsorption is found for Cu(II)-EDTA and Cd(II)-EDTA under both single and competitive conditions. Surface complexation modeling considered inner-sphere complexation and the diffuse layer model employing MINTEQA2; surface complexes used include Ti-(OH{sub 2})O-Cu{sup +}, Ti-(OH)EDTAH{sub 2}{sup {minus}2}, Ti-(OH)EDTA-Cu{sup {minus}2}, and Ti-(OH)EDTA-Cd{sup {minus}2}. Experimental and model predictions suggest no competitive adsorption between Cu(II) and Cd(II) at 5 {times} 10{sup {minus}5} M. On the other hand, adsorption data and model predictions indicate that Cd(II)-EDTA adsorption is favored over that of Cu(II)-EDTA with some competition for adsorption sites. Cd(II)-EDTA Adsorption was only slightly affected by the presence of Cu(II)-EDTA; however, Cu(II)-EDTA adsorption was strongly influenced by the presence of Cd(II)-EDTA, especially as the molar ratio of Cd(II)-EDTA/Cu(II)-EDTA increased. A modified surface complexation constant for Cd(II)-EDTA is required to explain the competitive data, suggesting surface site heterogeneity.

Authors:
;  [1]
  1. Univ. of Maryland, College Park, MD (United States). Dept. of Civil and Environmental Engineering
Publication Date:
OSTI Identifier:
680106
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Colloid and Interface Science; Journal Volume: 216; Journal Issue: 1; Other Information: PBD: 1 Aug 1999
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; COPPER; CADMIUM; ADSORPTION; TITANIUM OXIDES; SORPTIVE PROPERTIES; EDTA; MATHEMATICAL MODELS; ENVIRONMENTAL TRANSPORT

Citation Formats

Yang, J.K., and Davis, A.P. Competitive adsorption of Cu(II)-EDTA and Cd(II)-EDTA onto TiO{sub 2}. United States: N. p., 1999. Web. doi:10.1006/jcis.1999.6278.
Yang, J.K., & Davis, A.P. Competitive adsorption of Cu(II)-EDTA and Cd(II)-EDTA onto TiO{sub 2}. United States. doi:10.1006/jcis.1999.6278.
Yang, J.K., and Davis, A.P. 1999. "Competitive adsorption of Cu(II)-EDTA and Cd(II)-EDTA onto TiO{sub 2}". United States. doi:10.1006/jcis.1999.6278.
@article{osti_680106,
title = {Competitive adsorption of Cu(II)-EDTA and Cd(II)-EDTA onto TiO{sub 2}},
author = {Yang, J.K. and Davis, A.P.},
abstractNote = {Cu(II), EDTA, Cu(II)-EDTA, Cd(II)-EDTA, and Cu(II)/Cd(II) and Cu(II)-EDTA/Cd(II)-EDTA competitive adsorption onto TiO{sub 2} has been studied with variation of pH and concentration. For Cu(II) and EDTA, typical cationic and anionic types of adsorption are noted, respectively. Ligand-type adsorption is found for Cu(II)-EDTA and Cd(II)-EDTA under both single and competitive conditions. Surface complexation modeling considered inner-sphere complexation and the diffuse layer model employing MINTEQA2; surface complexes used include Ti-(OH{sub 2})O-Cu{sup +}, Ti-(OH)EDTAH{sub 2}{sup {minus}2}, Ti-(OH)EDTA-Cu{sup {minus}2}, and Ti-(OH)EDTA-Cd{sup {minus}2}. Experimental and model predictions suggest no competitive adsorption between Cu(II) and Cd(II) at 5 {times} 10{sup {minus}5} M. On the other hand, adsorption data and model predictions indicate that Cd(II)-EDTA adsorption is favored over that of Cu(II)-EDTA with some competition for adsorption sites. Cd(II)-EDTA Adsorption was only slightly affected by the presence of Cu(II)-EDTA; however, Cu(II)-EDTA adsorption was strongly influenced by the presence of Cd(II)-EDTA, especially as the molar ratio of Cd(II)-EDTA/Cu(II)-EDTA increased. A modified surface complexation constant for Cd(II)-EDTA is required to explain the competitive data, suggesting surface site heterogeneity.},
doi = {10.1006/jcis.1999.6278},
journal = {Journal of Colloid and Interface Science},
number = 1,
volume = 216,
place = {United States},
year = 1999,
month = 8
}
  • The adsorption characteristics of a variety of divalent and trivalent metal-EDTA complexes on to goethite ({alpha}-FeOOH) were examined in aqueous solution. Uncomplexed EDTA is adsorbed as a binuclear complex at low pH and as a mononuclear complex at high pH. Adsorption is ligand-like with a high extent of adsorption at low pH. The process can be described by formation of inner-sphere complexes by the surface complexation model with constant capacitance. The EDTA complexes of the divalent metals Ca, Zn, Ni, Cu, Co(II), and Pb, which are quinquedentate in solution (free donor atoms bound to the metal ion), all showed themore » same ligand-like adsorption behavior. Their adsorption as a function of pH and concentration can be described by the formation of one type of ternary surface complex and can be fitted with the same equilibrium constant. Pd(II) EDTA, which is bidentate or quadridentate in solution, is adsorbed more strongly, but also in a ligand-like manner. The EDTA complexes of the trivalent metals LaEDTA and BiEDTA are adsorbed very strongly over the whole pH range. The sexidentate complex of Co(III) is weakly adsorbed at low pH outer-spherically, i.e., by electrostatic interaction only. Fe(III) EDTA is weakly adsorbed over the whole pH range with a predominant nonspecific surface complex at low pH and a specific complex at high pH.« less
  • 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 causemore » 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.« less
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  • The addition of 0.1 M EDTA increases the sensitivity of the transfection of Acholeplasma laidlawii cells by mycoplasmavirus DNA, indicating that a nuclease activity may be present in this system. Both single- and double-stranded DNAs compete with the infectious DNA, so the cell has no specificity for the DNA strandedness.