Hydroxyl-Sulfate Exchange Stoichiometry on γ-Al2O3 and Kaolinite

He, Dong; Zelazny, L. W.; Martens, D. C.; Baligar, V. C.; Ritchey, K. D.

doi:10.2136/sssaj1996.03615995006000020015x

Cited by 26 publications

(29 citation statements)

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“…1). These experimental findings indicate that SO 4 retention proceeds primarily through an outer-sphere surface complexation mechanism, an interpretation that is supported by the available literature (Goldberg, 2010;He et al, 1996He et al, , 1997. Sulfate adsorption by gibbsite was successfully modeled by considering only outersphere complexation and the formation of ºAlOH 2 + -SO 4 2− data (log K int = 9.48; V Y = 1.53) (Table 3; Fig.…”

Section: Resultssupporting

confidence: 77%

Adsorption of Antimonate by Gibbsite: Reversibility and the Competitive Effects of Phosphate and Sulfate

Essington

Stewart

2016

Soil Science Soc of Amer J

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Antimony (sb) is a potential environmental contaminant of emerging concern that occurs in soils in the sb(V) oxidation state as the antimonate species sb(OH) 6 -. In soils, metal oxyhydroxides play an important role in the immobilization of contaminants and in restricting bioaccessibility. One such mineral is gibbsite, which bears the reactive aluminol surface functional group. Both inner-and outer-sphere surface complexation mechanisms have been inferred from conflicting sb(V) adsorption findings involving aluminol-bearing minerals. The objectives of this research are to characterize sb(V) adsorption by gibbsite and to use the macroscopic findings to develop mechanistic adsorption models. Antimonate adsorption envelopes were developed using two equilibrium techniques: continuous pH titration and batch. The adsorption of sb(V) decreases with increasing pH and increasing ionic strength, suggesting that outer-sphere surface complexation is an important adsorption mechanism. However, sb(V) retention is irreversible at pH <6 but is reversible in pH >7 systems, suggesting that inner-sphere species may be significant in acidic environments. Adsorbed sb(V) also generates a downward shift in the gibbsite isoelectric point, further supporting the formation of inner-sphere sb(V) surface complexes. Both PO 4 and sO 4 decrease adsorbed sb(V) concentrations: PO 4 throughout the pH 3 to 10 range and sO 4 in pH <7 systems. The triple-layer surface complexation model successfully predicts sb(V) adsorption by using both outer-sphere and inner-sphere surface species. The triple-layer model also predicts ligand adsorption in the competitive systems without the need for reoptimization.Abbreviations: BET, Brunauer-Emmett-Teller; ICP-AES, inductively coupled argon plasma-atomic emission spectroscopy; IEP, isoelectric point; SCM, surface complexation model; TLM, triple layer model; XRD, x-ray diffraction.A ntimony is one of the least abundant elements in soils, having a median concentration in uncontaminated soils from around the world of 1 mg kg −1 (range, <0.2-10 mg kg −1 ) (Bowen, 1979;Filella et al., 2002;Helmke, 2000). However, anthropogenic activities can result in elevated soil Sb levels (Crecelius et al., 1975;Filella et al., 2002;Li and Thornton, 1993;Nriagu, 1989;Nriagu and Pacyna, 1988;Scheinost et al., 2006). Soils that are particularly affected by Sb are those at military and civilian shooting ranges. Antimony is a hardening agent in lead bullets, which contain ~5% Sb (Carlin, 2000;Johnson et al., 2005;Kilgour et al., 2008). As bullets and bullet fragments corrode, Pb and Sb are released to the soil environment (Clausen and Korte, 2009;Kilgour et al., 2008). The resulting Sb concentrations can far exceed native soil levels. Antimony concentrations in military and civilian shooting range soils have been reported to range from <517 to <17,500 mg kg −1 (Basunia and Landsberger, 2001;Johnson et al., 2005;Kilgour et al., 2008;Knechtenhofer et al., 2003;Mitsunobu et al., 2006;Okkenhaug et al., 2013;Spuller et al., 2007), alth...

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Section: Resultssupporting

confidence: 77%

Adsorption of Antimonate by Gibbsite: Reversibility and the Competitive Effects of Phosphate and Sulfate

Essington

Stewart

2016

Soil Science Soc of Amer J

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“…The manufacturer provided a BET surface area of 100 ±15 m 2 g −1 with impurities <0.4%. This aluminum oxide material is commonly used in sorption studies (3,7,8,33). Although it is known that oxide surfaces such as γ -Al 2 O 3 are unstable in aqueous systems and react with water to form hydroxide functional groups (34), the effect of transformation processes on the surface mineralogy is commonly ignored in these types of studies.…”

Section: Adsorbentsmentioning

confidence: 99%

“…Sposito (5) suggested that anions with moderate sorption affinity, such as SO 4 and SeO 4 , sometimes sorb as an outer-sphere complex and sometimes sorb as an inner-sphere complex on soil mineral surfaces. The macroscopic observation of decreasing SeO 4 and SO 4 adsorption on metal oxides with increasing concentration of the background electrolyte has commonly been interpreted as an indication for the formation of an outer-sphere surface complex of these anions (6)(7)(8). However, the macroscopic nature of the ionic strength effects on anion adsorption is an indirect technique for evaluation of sorption mechanisms at mineral surfaces (8).…”

Section: Introductionmentioning

confidence: 99%

Vibrational Spectroscopy Study of Selenate and Sulfate Adsorption Mechanisms on Fe and Al (Hydr)oxide Surfaces

Wijnja

Schulthess

2000

Journal of Colloid and Interface Science

253

192

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“…These results suggest that SO 4 was probably adsorbed on the surface charge of the soil colloids through a ligand exchange mechanism or the formation of inner-sphere complexation (Curtin and Syers, 1990;Agbenin, 1997 V Bray P-1 Many researchers have reported that there is a release of hydroxil (OH") ions as a result of ligand exchange between SO 4 and OH" during equilibration of soils with solution containing SO 4 (Chang and Thomas, 1963;Chao et al, 1965, Hasan et al, 1970Hue et al, 1985;He et al, 1996). Curtin and Syers (1990) proposed an alternative mechanism based on diffuse double layer theory, suggesting that SO 4 2 -ions can penetrate the Stern layer, thereby inducing additional positive charge on the surface by OH" release, a mechanism termed low affinity specific anion adsorption (Uehara and Gillman, 1981).…”

Section: Behavior Of Sulfate Adsorptionmentioning

confidence: 99%

Phosphorus retention by tropical soils as influenced by sulfate application

Cajuste

Laird

Cuevas‐G.

et al. 1998

Communications in Soil Science and Plant Analysis

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Soils with variable surface charge are reported to have high affinities for the adsorption of anions and also to selectively retain cations. A laboratory study was conducted to determine the influence of sulfate (SO 4 2-) anion on phosphate (PO 4 3-) sorption/desorption from tropical soils. Duplicate 1.0 g soil samples were shaken with 10 mL portions of varying concentrations of calcium sulfate (CaSO 4 ·2H 2 O) (0.0 to 1.5 x 10 -2 M). Subsequently, the samples were equilibrated with increasing concentrations of monocalcium phosphate [Ca(H 2 PO 4 ) 2 ·H 2 O] in 0.01M calcium chloride (CaCl 2 ) to measure PO 4 sorption and afterwards with 0.01M CaCl 2 for PO 4 desorption. Results showed that PO 4 sorption maxima increased as concentrations of SO 4 in solution increased. In the most acidic soil, SO 4 adsorption from the 0.015M CaSO 4 ·2H 2 O solution increased PO 4 sorption by 93%. There was a decrease in pH in the SO 4 extracts; this would indicate that calcium (Ca) from the SO 4 salt applied to the soils before P addition was specifically adsorbed by the exchange complex and originated new sites for binding PO 4 . On the average, about 20% of the sorbed PO 4 was removed with the CaCl 2 treatment, suggesting that PO 4 was specifically adsorbed by the variable charge soils.

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Hydroxyl-Sulfate Exchange Stoichiometry on γ-Al2O3 and Kaolinite

Cited by 26 publications

References 0 publications

Adsorption of Antimonate by Gibbsite: Reversibility and the Competitive Effects of Phosphate and Sulfate

Adsorption of Antimonate by Gibbsite: Reversibility and the Competitive Effects of Phosphate and Sulfate

Vibrational Spectroscopy Study of Selenate and Sulfate Adsorption Mechanisms on Fe and Al (Hydr)oxide Surfaces

Phosphorus retention by tropical soils as influenced by sulfate application

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