Immobilization of Cadmium and Lead Compound Contaminated Soil Using New Porous Material Combined with Phosphate

Abstract

The effect of new porous material and its compound treatments with phosphate on immobilization of cadmium and lead in contaminated soil was studied using a pot-culture experiment, and the immobilization mechanism of these amendments was clarified through analysis of heavy metal fractions. The single treatments of porous material could not significantly promote growth of rape, while the compound treatments of porous material and phosphate markedly increased dry biomass of shoots and roots, with maximal increases of 59.8 % and 109.6 %, respectively. The immobilization treatments could significantly reduce Cd and Pb concentrations in shoots, with maximal reductions of 62.7 % and 43.4 %, respectively, and the treatments of porous material combined with phosphate appeared more efficient than the single amendment treatments in reducing Pb uptake by rape. Addition of porous material could markedly decrease soil pH values. The immobilization treatments could significantly decrease concentrations of available Cd and Pb in soils, with maximal reductions of 45.9 % and 46.8 %, respectively, and the compound porous material treatments appeared more effective than the single treatments in reducing availability of Pb. Through special adsorption of chemistry and formation of mineral precipitation, porous material and phosphate could promote transformation of acid-extractable Cd and Pb into residual fraction, resulting in significant reduction of heavy metals' bioavailability and mobility and then fixing remediation of contaminated soil. In summary, the compound treatments of porous material and phosphate are the most effective treatments for immobilization of Cd and Pb in contaminated soils.