Leaching characteristics of lead-contaminated clay stabilized by phosphate rock

An investigation of leaching characteristics of phosphate rock (PR) stabilized Pb-contaminated clay is presented under different initial Pb concentrations and phosphate rock contents via a series of toxicity characteristic leaching procedure (TCLP) at curing time of 1, 3, 7, 1, and 28 days. The designed initial Pb concentrations are 500, 1000, 5000, and 10000 mg/kg (dry soil weight basis), and phosphate rock contents are 5%, 8%, 12%, 15%, 20% and 30%. The results show that Pb concentrations of leachate decrease with the increase of the phosphate rock content and curing time. Furthermore, the variation between the Ca and Pb concentrations of leachate is negatively correlated. The pH values of specimen and leachate are influenced by the initial Pb concentration and increase with the phosphate rock content and curing time. It is found that the variation between Pb and Ca concentrations of leachate is mainly influenced by the initial Pb concentration. A proposed fitting equation based on the value of the initial Pb concentration is adopted to evaluate the variation between the Pb and Ca concentrations of leachate.