Influence of Solution Composition on Sorption of Zinc by Soils

Abstract

AbstractThe effect of soil solution composition on Zn sorption was investigated in nine soils of varying physical and chemical properties. Most of Zn applied in 0.01 N CaCl2 solution was strongly sorbed by the soils and desorption by 0.01 N CaCl2 solution was negligible even after five desorption cycles. At initial Zn solution concentrations of ⩽ 10 ppm, sorption could be described by the Freundlich sorption isotherm equation. Deviations from this equation were observed at higher concentrations, suggesting the presence of more than one type of site or mechanism for Zn sorption in the soils.The effects of anion species (Cl‐, NO‐3, and SO2‐4) and ionic strength on Zn sorption were examined at anion concentrations of 0.005, 0.02, and 0.1M. Complexation of Zn (as ZnSO04) in the SO2‐4 system was higher than in either the NO‐3 [Zn(NO3)+] or Cl‐ [Zn(Cl)+] system. However, under the experimental conditions examined, neither ionic strength nor anion complex formation significantly affected Zn sorption.The presence of EDTA (Ethylenediaminetetraacetic acid) in the soil suspension significantly decreased Zn sorption by the three soils investigated. Only a slight difference in Zn sorption was observed whether EDTA was added to the (Zn containing) soil solution before or after contact with soil.The influence of Ni and Cu on Zn sorption was significant only when metal concentration in the soil solution was in excess of the sorbing capacity of the soil. In this case, Cu was more effective than Ni in decreasing Zn sorption.