Iron ternary adsorption

To date, only the second form of ternary adsorption has been observed for iron oxides. Davis and Leckie (1978 a) found that thiosulphate adsorbed on ferrihydrite in acid media with adsorption decreasing to zero as the pH rose to ca. 7, whereas the adsorption edge of silver lay between pH 7 and 8. In the presence of thiosulphate, adsorption of silver was enhanced in the pH range 4-6.5 (Fig. 10.10), i. e. 

Reductive dissolution may be more complex than the two previous mechanisms in that it involves electron transfer processes. Formation of Fe" via reductive dissolution can be effected by adsorption of an electron donor, cathodic polarization of an electrode supporting the iron oxide and by transfer of an electron from within a ternary surface complex to a surface Fe ". Addition of Fe" to a system containing a ligand such as EDTA or oxalate promotes electron transfer via a surface complex and markedly accelerates dissolution. 

Bonneviot L, Clause O, Che M, Manceau A, Dexpert H (1989b) EXAFS characterization of the adsorption sites of nickel ammine and ethyldiamine complexes on a silica surface. Catalysis Today 6 39-46 Bomebusch H, Clausen BS, Steffensen G, Liitzenkirchen-Hecht D, Frahm R (1999) A new approach for QEXAFS data acquisition. J Synchrotron Rad 6 209-211 Bostick BC, Fendorf S, Barnett MO, Jardine PM, Brooks SC (2002) Uranyl surface complexes formed on subsurface media from DOE facilities. Soil Sci Soc Am J (2002) 66 99-108 Bottero JY, Manceau A, Villieras F, Tchoubar D (1994) Structure and mechanisms of formation of iron oxide hydroxide (chloride) polymers. Langmuir 10 316-319 Bourg ACM, Joss S, Schindler PW, (1979) Ternary surface complexes 2. Complex formation in the system silica-Cu(II)-2,2 bipyridyl . Chimia 33 19-21... 

In an another stndy related to the additivity rule (Alessi and Fein 2010), the sorption of Cd(II) in mixtures of kaolinite. Bacillus subtilis bacterial cells, and iron oxy-hydroxide (HFO) was performed in the absence and presence of an organic ligand, acetate. The resnlts indicate that for systems containing B. subtilis, HFO, and kaolinite, the component additivity approach is a reasonable predictor of metal distribution, with the accuracy limited by the accuracy of the stability constants of the important surface complexes. However, in systems including acetate, the additivity rule predictions significantly nnderestimate the extent of adsorption above pH 5, likely due to the formation of ternary Cd-acetate surface complexes on each surface. 

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