%0 Journal Article %T A Comparison of the Solubility Products of Layered Me(II)每Al(III) Hydroxides Based on Sorption Studies with Ni(II), Zn(II), Co(II), Fe(II), and Mn(II) %A Evert J. Elzinga %A Lasita Bhattacharya %J - %D 2018 %R https://doi.org/10.3390/soilsystems2020020 %X Abstract The precipitation of mixed metal每aluminum-layered double hydroxides (Me(II)每Al(III)-LDH)) may be an important control of the solubility of Mn(II), Fe(II), Ni(II), Zn(II), and Co(II) in soils, but assessment of this process is hindered by a lack of thermodynamic data. Here, we determined the solubility products (Ksp) of the Me(II)每Al(III)-LDHs formed by these metals based on long-term Me(II)每污Al 2O 3 sorption studies complemented with X-ray absorption spectroscopy (XAS) measurements. The LDH phases had the chemical formula Me(II) 2/3Al 1/3(OH) 2Cl 1/3. Solubility products were derived as Ksp = (Me 2+) aq 2/3(Al 3+) aq 1/3(OH ˋ) aq 2(Cl ˋ) aq 1/3, where brackets represent aqueous activity values determined from the equilibrium solution chemistry of the sorption samples. The Ksps are metal-dependent, with values increasing by two orders of magnitude in the order Ni(II) < Zn(II) < Co(II) < Fe(II) < Mn(II). Comparison to the solubility of 汕-Me(OH) 2 suggests considerable thermodynamic preference of Me(II)每Al(III)-LDH over 汕-Me(OH) 2 in soil environments and reveals a linear relation between the log-transformed Ksp values of Me(II)每Al(III)-LDH and 汕-Me(OH) 2. Solubility plots suggest that Ni(II)每, Zn(II)每, and Co(II)每Al(III)-LDH may form in metal-polluted soils. Fe(II)每Al(III)-LDH may occur in riparian soils undergoing reduction, but precipitation of Mn(II)每Al(III)-LDH appears unlikely as it requires [Mn 2+] aq much higher than commonly encountered in reducing soils. Additional thermodynamic and field studies are needed to further assess the importance of Me(II)每Al(III)-LDHs in soils and related geochemical systems. View Full-Tex %K trace metals %K layered double hydroxides %K sorption %K precipitation %K solubility %K aluminum %U https://www.mdpi.com/2571-8789/2/2/20