Competitive sorption of metal ions onto a north-eastern France soil. Isotherms and XAFS studies

This paper reports on the sorption of Cu(II), Cr(III), and Zn(II) by a north-eastern France soil from single and ternary metal solutions, as a function of pH, time, and metal concentrations. Isothermal sorption batch experiments led to macroscopic and indirect results. The use of extended X-ray absorption fine structure (EXAFS) spectroscopy allowed us to obtain molecular scale information about the species and the structural environment of metals on the soil surface. The sorption capacities for single and ternary metal decreased in the order Cr3+ > Cu2+ > Zn2+. In absence of any interfering metals, the adsorption capacities were 0.22 mmol/g Cr3+, 0.21 mmol/g Cu2+, and 0.08 mmol/g Zn2+. In the case of ternary systems, a decrease in the sorbed amount of 40%, 60%, and 62% for chromium, copper, and zinc, respectively, was observed. EXAFS spectra underlined a metal sorption onto goethite–humate complexes.