Remediation of contaminated soils with cadmium and copper using dicalcium phosphate

At the present time، contamination of water and soil resources is an important environmental challenge. Therefore، decontamination of such soils is a prerequirement of using these resources. The stabilization/solidification is cost effective remediation method that prevents spreading of heavy metals in soil and water resources. In this process، contaminated soil reacts with amendments such as phosphate materials to form low soluble or non-soluble stable materials. In this research the performance of dicalcium phosphate (DCP) in stabilizing and immobilizing of two ubiquitous metals Cd and Cu through soil was investigated. To understand the mobility of these metals within coarse textured soil، 12 leaching column tests were conducted. Four soil samples were contaminated with 500 mg/kg Cu while four others were contaminated by 500 mg/kg Cd. One of the specimens was left blank، while the other three were mixed with 0. 1، 0. 2 and 0. 5% (by weight) DCP stabilizer. In addition، four other samples were simultaneously contaminated with both metals and the same amount of additive. The results indicated in the case of Cu contaminated samples، application of 0. 1% DCP reduces 93% of this metal in the first pore volume of effluent. For Cd، this amount was 80%. Increasing in the amount of stabilizer (0. 2 and 0. 5%) neglects the metal in effluent. In simultaneous contamination using 0. 1% DCP، 90 and 92% of Cu and Cd was reduced، respectively. Therefore، immobilizing of Cd performed better than Cu when both were present. This study shows that DCP is an effective additive for stabilizing Cd and Cu to protect groundwater from contamination leached out of polluted coarse textured soil.