Complexation at the edges of hydrotalcite: The cases of arsenate and chromate

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:393

Article

Jobbagy, Matias¹  Regazzoni, Alberto E.^2,3 

[1] Univ Buenos Aires, Fac Ciencias Exactas & Nat, INQUIMAE, Buenos Aires, DF, Argentina

[2] Comis Nacl Energia Atom, Ctr Atom Constituyentes, San Martin, Argentina

[3] Univ Nacl Gen San Martin, Inst Tecnol Jorge A Sabato, San Martin, Argentina

关键词: Layered double hydroxides;    Hydrotalcite;    Arsenate;    Chromate;    Adsorption;    Surface complexation;   

DOI  :  10.1016/j.jcis.2012.10.069

来源: Elsevier

【 摘 要 】

Sorption of CrO42- and HAsO42- by hydrotalcite, in its chloride form, was studied as a function of anion concentration. In both cases, the shape of the isotherms is langmuirian. The maximum uptake of CrO42- equals the ion-exchange capacity of the solid, whereas sorption of HAsO42- saturates at a higher value. Chloride ions inhibit the uptake of both anions, the amount of sorbed CrO42- declining rapidly to zero. The uptake of HAsO42-, however, attains a constant value at high chloride concentrations. The excess of arsenate uptake follows, at constant pH, a langmuirian dependence with equilibrium concentration and decreases with increasing pH, depicting a marked change in slope at pH approximate to pQ(a3). CrO42- and HAsO42- have notable, albeit different, effects on the electrophoretic behavior of hydrotalcite; the positive particle charge is screened almost completely by CrO42-, whereas sorption of HAsO42- produces charge reversal. These results reflect the formation of inner-sphere arsenate surface complexes at the edges of hydrotalcite particles. The underlying rationale is discussed in terms of the crystal structure of hydrotalcite surfaces. (C) 2012 Elsevier Inc. All rights reserved.

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