Trace metal redistribution during extraction of model soils by acetic acid/sodium acetate

A number of model soils synthesized with various known amounts of natural minerals and humic acid were employed to study copper and lead redistribution during extraction by 1 M HOAc/NaOAc. The adsorption intensities of the individual constituent phases were measured from adsorption isotherms, and the redistribution behavior was studied by the standard additions method. Humic acid and pyrolusite are found to exhibit the highest binding affinity for Cu and Pb, respectively, and their relative importance relies upon both their binding ability and their abundance. The extractable concentrations of the metals and the extent of recovery depend largely upon the composition of the model soils, owing to different binding strength presented in the various systems investigated. The presence of dissolved humic acid during extraction has a significant influence on metal redistribution, as evidenced by the increase in the adsorption of Cu and decrease in the adsorption of Pb. In view of the diverse compositions and various competing reactions involved, it is recognized that redistribution behavior will vary widely among both natural soil systems and given metals.