The effect of crop exudates and EDTA on cadmium adsorption by agricultural podsolic soil: implications on groundwater

Sorption studies were conducted to investigate the effect of the presence of organic acids or exudates released by crops [acetic acid (AA), citric acid (CA) and oxalic acid (OA)] and ethylenediaminetetraacetic acid (EDTA) on the adsorption of carcinogenic cadmium (Cd) by an agricultural podsolic soil acting as a natural adsorbent. Powder X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy and cation exchange capacity were used to characterize the soil. The effect of pH and changing concentration of the organic acids and Cd on the adsorption was investigated. PHREEQC (short for pH, REdox and EQuilibrium in C language) geochemical modeling was used to determine the speciation of Cd. The podsolic soil was effective as a natural clay adsorbent in capturing Cd, thus preventing mobility to groundwater. In the presence of crops organic acids and EDTA, the adsorption capacity decreased at all initial concentrations of Cd and the extent of reduction followed the sequence: OA