In situ immobilization of zinc polluted soil using thermal-activated serpentine

Abstract

ABSTRACTIn situ immobilisation zinc (Zn) in simulated polluted soil was conducted by using the thermal-activated serpentine prepared via heating natural serpentine at different temperatures as amendments. The effects of the amendments on the form of Zn in soil and the potential immobilisation mechanisms were investigated. After Zn polluted soil incubated with serpentine at rates of 3% by weight for 60 d, the pH value of the soil could be obviously increased, and then resulting in reducing the content of TCLP-Zn (toxicity characteristic leaching procedure extractable Zn) in soil. Furthermore, the addition of serpentine, especially the serpentine activated at 700 °C, could promote significantly the transformation from bioavailable Zn speciation to a much less bioavailable speciation, and the ratio of exchangeable and carbonate form of Zn decreased by 34.5%, and the proportion of residual form of Zn increased by 28.5% compared with CK (no-amendment control) treatment. The formation of Zn5(NO3)2(OH)8·2H2O and Zn(NO3)(OH)·H2O as well as surface adsorption were the main immobilisation mechanisms. These results indicated that thermal-activated serpentine had the great potential for immobilisation of Zn in soil, and it would lay a foundation for the construction of high performance amendments of heavy metal.