Surface adsorption of divalent metals onto metal-oxides may lead to the formation of mixed layered metal hydroxide (LDH) phases. In aqueous geochemical environment these phases can be considered a significant product of sequestration for various divalent metals, including Ni(II), Zn(II), Co(II), Fe(II) and Mn(II). Here, detailed kinetic studies were conducted to monitor the sorption of these divalent metals onto γ-Al2O3. The experiments were performed in an anaerobic chamber to exclude CO2 and O2, and covered a time range of 2-3 months in order to achieve sorption equilibrium. For each metal, a range of different pH values were used, which generally fell in the near-neutral to alkaline range (&gt;6.5). Ionic strength was set at 0.1 M with NaCl. Samples were taken at regular intervals to monitor the progress of the sorption process, and to assess the time required to achieve equilibrium. After equilibrium was attained, the aqueous metal concentrations were used to calculate the solubility products (Ksp) of the Me(II)-Al(III)-LDH phases for the aqueous chemical equilibrium described by: Me(II)2/3Al(III)1/3(OH)2Cl1/3(s) ↔ 2/3 Me(II)(aq) + 1/3 Al(III) (aq) + 2OH- (aq) +1/3 Cl- (aq) For a given Me(II), similar value of Ksp derived from sorption studies conducted at different pH values confirm the formation of similar Me(II)-Al(III)-LDH. Comparison of the different Ksp values of different Me(II)-Al(III)- LDHs give us better understanding of the solubility of respective metals during these sorption studies. In addition, comparison of the Ksp values of these phases with those of their corresponding Me(OH)2 phases help to predict a relationship between the two.

Comparing the solubility products of layered Me(II)-Al(III)-hydroxides based on sorption studies with Ni(II), Zn(II), Co(II), Fe(II), and Mn(II)

251st National Meeting (2016)

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