TRACE-METAL REDISTRIBUTION DURING EXTRACTION OF MODEL SOILS BY ACETIC-ACID SODIUM-ACETATE

A number of model soils synthesized with various known amounts of natu ral minerals and humic acid were employed to study copper and lead red istribution during extraction by 1 M HOAc/NaOAc. The adsorption intens ities of the individual constituent phases were measured from adsorpti on isotherms, and the redistribution behavior was studied by the stand ard additions method. Humic acid and pyrolusite are found to exhibit t he highest binding affinity for Cu and Pb, respectively, and their rel ative importance relies upon both their binding ability and their abun dance. 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 invest igated. The presence of dissolved humic acid during extraction has a s ignificant influence on metal redistribution, as evidenced by the incr ease in the adsorption of Cu and decrease in the adsorption of Pb. In view of the diverse compositions and various competing reactions invol ved, it is recognized that redistribution behavior will vary widely am ong both natural soil systems and given metals.