The Role of Hydrolysis in the Reaction of Heavy Metals with Soil‐Forming Materials

Abstract

AbstractThe proposition that hydrolysis may account for the selective adsorption of heavy metals by clay surfaces is compared with an alternate explanation of specific exchange of the metal with weakly dissociable H+. It is shown that past evidence offered in support of the two hypotheses is somewhat ambiguous. Theoretical treatment is presented for the competition of ions in adsorption reactions which provides a means of distinguishing between the two alternatives through the effect of H+ on the metal‐clay reaction in the presence of a competing ion. Experimentally, the effect of H+ on the reaction of Co2+ with montmorillonite is studied in the presence and absence of Mg2+, a weakly competing ion. Ionic strength is held constant, and nonspecific reactions are minimized with an excess of CaCl2. The results are interpreted as favoring the hydrolysis hypothesis. Inherent assumptions are considered.