RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

Sorption of Cd²⁺, Pb²⁺ and Cu²⁺ to kaolinite from landfill leachate-contaminated groundwater, artificial groundwater (same major-ion concentrations as groundwater) and NaNO₃ (same ionic strenght as the groundwater) was studied. Complexation of Cu²⁺ and Cd²⁺ by dissolved organic matter (DOM) in the groundwater was also studied. There was less sorption of all three metals from groundwater than from NaNO₃ for large pH ranges. Sorption of Cd²⁺ and Pb²⁺ seemed to be due to a combination of ion exchange and surface complexation. This hypothesis was suppored by agreement between an ion exchange/surface complexation model and the sorption data. There was less Cu²⁺ sorption from groundwater than from the NaNO₃ for pH-values > 5, but Cu²⁺ sorption from artificial groundwater was the same as from NaNO₃. Sorption of Cu²⁺ was apparently by surface complexation only. For fixed pH and variable total Cu, there was less Cu²⁺ sorption from groundwater than from NaNO₃, which is consistent with the formation of nonsorbing soluble complexes with DOM. A soluble complexation/surface complexation model reproduced the trends in the data, which supports the hypothesis of nonsorbing Cu complex formation.