Lead Immobilization from Aqueous Solutions and Contaminated Soils Using Phosphate Rocks

This research investigated the effectiveness of phosphate rocks in immobilizing Pb from aqueous solutions and contaminated soils. Different amounts of phosphate rocks were reacted with aqueous solutions containing Pb or with Pb-contaminated soils. The results show that phosphate rocks were effective in immobilizing Pb from aqueous solutions with a minimum Pb removal of 38.8-100%. The reaction time had less effect on Pb immobilization than the quantity of phosphate rocks used. Selected phosphate rocks reduced water-soluble Pb from a contaminated soil by 56.8-100%. The primary mechanism of Pb immobilization was via dissolution of phosphate rocks and precipitation of a fluoropyromorphite-like mineral. Different methods of mixing phosphate rocks and soil and incubation time had little effect on Pb immobilization. Our results strongly demonstrate that phosphate rocks may provide a cost-effective way to remediate Pb-contaminated water, soils, and wastes.