Adsorption characteristics of metal-EDTA complexes onto hydrous oxides

Bowers, Alan R.; Huang, Chihpin

doi:10.1016/0021-9797(86)90410-8

Cited by 136 publications

(78 citation statements)

References 16 publications

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“…Since hydrogen bonding does not directly involve the metal atoms of the oxide substrate, a third conclusion is that all of the above conclusions should hold for sorption on oxides with similar charging behavior. This conclusion is consistent with the results of Bowers andHuang (1986) andGirvin et al (1993). A fourth conclusion regards the dramatically lower sorptive capacity of Fe(III)-and Al(III)-oxides for Co(III)EDTA as compared to Co(II)EDTA (Girvin et al, 1993;Nowack and Sigg, 1996).…”

Section: Pb(ii) 2nd Coordination Shellsupporting

confidence: 83%

“…5) Nowack and Sigg (1996) showed Pb(II)EDTA uptake on goethite at pH 8 (the highest pH for which they measured Pb(II)) compared to a pH PZC of 7.4. Bowers and Huang (1986) showed Pb(II)EDTA uptake on γ-Al 2 O 3 up to pH 10 vs. a reported pH PZC of 9.0 to 9.7. Ni(II)EDTA and Co(II)EDTA uptake isotherms are nearly identical to that of Pb(II)EDTA, all other conditions being equal (Bowers and Huang, 1986;Nowack and Sigg, 1996).…”

Section: Pb(ii) 2nd Coordination Shellmentioning

confidence: 99%

“…Others (e.g., Bowers and Huang, (1986) and Girvin et al (1993)) have proposed that Me(II)/(III)EDTA complexes may hydrogen bond to oxide surface sites. Given the donor capacity of the carboxylate oxygens (in adsorbed Pb(II)EDTA complexes) not bonded to Pb(II), it is plausible that hydrogen bonds could form between them and surface (hydr-)oxo groups.…”

Section: Pb(ii) 2nd Coordination Shellmentioning

confidence: 99%

“…Since Pb(II)EDTA uptake is correlated with the density of protonated surface functional groups (Bowers and Huang, 1986) Bargar et al (1996).…”

Section: Pb(ii) 2nd Coordination Shellmentioning

confidence: 99%

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Outer-sphere adsorption of Pb(II)EDTA on goethite

Bargar

Persson

Brown

1999

Geochimica et Cosmochimica Acta

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FTIR and EXAFS spectroscopic measurements were performed on Pb(II)EDTA adsorbed on goethite as functions of pH (4-6), Pb(II)EDTA concentration (0.11 µM -72 µM), and ionic strength (16 µM -0.5M). FTIR measurements show no evidence for carboxylate-Fe(III) bonding or protonation of EDTA at Pb:EDTA = 1:1. Both FTIR and EXAFS measurements suggest that EDTA acts as a hexadentate ligand, with all four of its carboxylate and both amine groups bonded to Pb(II). No evidence was observed for inner-sphere Pb(II)-goethite bonding at Pb:EDTA = 1:1. Hence, the adsorbed complexes should have composition Pb(II)EDTA 2-. Since substantial uptake of PbEDTA (II) 2-occurred in the samples, we infer that Pb(II)EDTA 2-adsorbed as outer-sphere complexes and/or as complexes that lose part of their solvation shells and hydrogen bond directly to goethite surface sites. We propose the term "hydration-sphere" for the latter type of complexes because they should occupy space in the primary hydration spheres of goethite surface functional groups, and to distinguish this mode of sorption from common structural definitions of inner-and outer-sphere complexes. The similarity of Pb(II) uptake isotherms to those of other divalent metal ions complexed by EDTA suggests that they too adsorb by these mechanisms. The lack of evidence for inner-sphere EDTA-Fe(III) bonding suggests that previously proposed metal-ligand -promoted dissolution mechanisms should be modified, specifically to account for the presence of outer-sphere precursor species.

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Section: Pb(ii) 2nd Coordination Shellsupporting

confidence: 83%

Section: Pb(ii) 2nd Coordination Shellmentioning

confidence: 99%

Section: Pb(ii) 2nd Coordination Shellmentioning

confidence: 99%

“…Since Pb(II)EDTA uptake is correlated with the density of protonated surface functional groups (Bowers and Huang, 1986) Bargar et al (1996).…”

Section: Pb(ii) 2nd Coordination Shellmentioning

confidence: 99%

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Outer-sphere adsorption of Pb(II)EDTA on goethite

Bargar

Persson

Brown

1999

Geochimica et Cosmochimica Acta

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“…A similar pattern of adsorption on ~-A1203 was observed for equal molar Co(II)EDTA for pH 5 to 9.5 over a wide range of sorbate concentrations and solid-to-sorbate ratios (Girvin et al 1993). Metal adsorption in equalmolar Cd-, Cu-, Ni-, Pb-and Zn-EDTA suspensions of ~-A1203 (pHpz~ = 9.2), was ligand-like for Ni and Cu and mixed cation-ligand-like for Cd, Pb and Zn (Bowers and Huang 1986). In equal molar Cu-, Ni-, Pb-, Zn-and Cd-NTA suspensions of ~-AI203, only Cu exhibited mixed cation-and ligand-like metal adsorption (Elliott 1979;Elliott and Huang 1979).…”

Section: Introductionmentioning

confidence: 96%

Adsorption of Nitrilotriacetate (NTA), Co and CoNTA By Gibbsite

Girvin

Gassman

Bolton

1996

Clays and clay miner.

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Abstract--Adsorption of Co 2 § nitrilotriacetic acid (NTA) and equal-molar Co 2 § and NTA by a low surface area (LSA) commercial gibbsite (3.5 m 2 g-~) was investigated in batch as a function of pH (4.5 to 10.5), adsorbate (0.5 to 10 txM) and adsorbent (0.5 to 75 g L ~) concentrations and ionic strength (0.01 to 1 M NaC104). The adsorption of Co 2 § (Co-only) and the acid form of NTA (NTA-only) by gibbsite in 0.01 M NaC104 exhibit cation-like and anion-like adsorption edges, respectively. For the equal-molar CoNTA chelate, Co and NTA adsorption edges were similar but not identical to the Co-only and NTAonly edges. Differences suggest the existence of a ternary CoNTA surface complex with the Co in the intact chelate coordinated to surface hydroxyls. NTA-only adsorption was insensitive to ionic strength variation, indicating weak electrostatic contributions to surface coordination reactions. This is consistent with the formation of inner-sphere surface NTA complexes and ligand exchange reactions in which monodentate, bidentate and binuclear NTA surface complexes form. Cobalt adsorption increases (edge shifts to lower pH by 1 pH unit) on LSA gibbsite as ionic strength increases from 0.01 to 1 M NaC104. For the same ionic strength change, a similar shift in the Co-only edge was observed for another commercial gibbsite (16.8 m 2 g 1); however, no change was observed for ~-A1203. Ionic strength shifts in Co 2+ adsorption by gibbsite were described as an outer-sphere CoOH § surface complex using the triplelayer model. Results suggest that, at waste disposal sites where 6~ and NTA have been co-disposed, NTA will not promote ligand-like adsorption of Co for acid conditions, but will reduce cation-like adsorption for basic conditions. Thus, where gibbsite is the dominant mineral sorbent, NTA will not alter 6~ mobility in acidic pore waters and groundwaters; however, NTA could enhance 6~ mobility where alkaline conditions prevail, unless microbial degradation of the NTA occurs.

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Use of red mud for toxic metals removal: The case of nickel

Zouboulis

Kydros

1993

J of Chemical Tech & Biotech

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The presence of red mud was found to remove effectively nickel ions from dilute aqueous solutions (50 mg dm−3). Red mud, being an industrial solid by‐product/waste from alumina production during bauxite processing, was found to act simultaneously as an alkalinity regulator, causing precipitation of nickel as the insoluble hydroxide, as an adsorbent of the formed nickel hydroxide and as a flocculant of the resultant fine particulate matter. Sedimentation was subsequently considered as a possible solid/liquid separation technique. Various parameters, such as dispersion pH, red mud and nickel concentrations and ζ‐potential, were examined and promising results were obtained.

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Adsorption characteristics of metal-EDTA complexes onto hydrous oxides

Cited by 136 publications

References 16 publications

Outer-sphere adsorption of Pb(II)EDTA on goethite

Outer-sphere adsorption of Pb(II)EDTA on goethite

Adsorption of Nitrilotriacetate (NTA), Co and CoNTA By Gibbsite

Use of red mud for toxic metals removal: The case of nickel

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