Preliminary studies on mobilisation of copper and lead from contaminated soils and readsorption on competing sorbents

The mobilisation and transfer of copper and lead from polluted soil (sample taken from the vicinity of copper smelter) to five different — mainly clayey — competing sorbents have been studied using a multichamber device. The system consists of a central chamber which contained the soil suspension and six external chambers containing the different sorbents: zeolite, smectite, vermiculite, diatomite and halloysite. The solids in the central and external chambers are separated by 0.45 μm membranes which allow diffusion of the mobilised, dissolved metal constituents. In the central chamber the metals from the soil were mobilised by decrease of pH (< 5). The readsorbed amounts of Cu and Pb were obtained by taking samples after different time periods. The copper is mobilised to a higher degree than lead. The distribution of Cu is dominated by transfer and readsorption on smectite and zeolite, and also on halloysite at higher pH. Lead is mainly readsorbed on zeolite, and, at lower pH, on halloysite and smectite as well. Under the applied experimental conditions no significant transfer of both the Cu and Pb to the vermiculite and diatomite could be observed. These results indicate the higher affinity of lead on zeolite if compared with smectite; however, the latter remains the most effective sorbent of Cu. A mixture of smectite and zeolite is proposed for soil remediation procedures.