Spectroscopic and Modeling Study of Lead Adsorption and Precipitation Reactions on a Mineral Soil

摘要

This study investigated the adsorption reactions of lead (Pb) on a well-characterized soil and examined the Pb adsorption complex using several techniques. Traditional Pb batch adsorption experiments (adsorption isotherms and envelopes), X-ray absorption spectroscopy (XAS), and surface complexation modeling were used. In addition, comparisons were made of the Pb adsorption behavior on soil with Pb adsorption experiments performed on individual soil minerals. The effects of pH on Pb adsorption revealed that the two mechanisms controlling Pb solubility in the presence of soils and soil minerals are adsorption on mineral surfaces and pH-dependent precipitation of a poorly crystalline Pb solid phase (probably Pb(OH)_2). The results from EXAFS analysis revealed a possible Pb inner-sphere adsorption mechanism that was used in conjunction with a surface complexation model to quantitatively describe Pb binding to soil.