Environ Sci Pollut Res DOI 10.1007/s11356-014-3720-z

RESEARCH ARTICLE

Remediation of cadmium- and lead-contaminated agricultural soil by composite washing with chlorides and citric acid Yu-jiao Li & Peng-jie Hu & Jie Zhao & Chang-xun Dong

Received: 17 July 2014 / Accepted: 10 October 2014 # Springer-Verlag Berlin Heidelberg 2014

Abstract Composite washing of cadmium (Cd)- and lead (Pb)-contaminated agricultural soil from Hunan province in China using mixtures of chlorides (FeCl3, CaCl2) and citric acid (CA) was investigated. The concentrations of composite washing agents for metal removal were optimized. Sequential extraction was conducted to study the changes in metal fractions after soil washing. The removal of two metals at optimum concentration was reached. Using FeCl3 mixed with CA, 44 % of Cd and 23 % of Pb were removed, and 49 and 32 % by CaCl 2 mixed with CA, respectively. The mechanism of composite washing was postulated. A mixture of chlorides and CA enhanced metal extraction from soil through the formation of metal–chloride and metal–citrate complexes. CA in extract solutions promoted the formation of metal–chloride complexes and reduced the solution pH. Composite washing reduced Cd and Pb in Fe–Mn oxide forms significantly. Chlorides and CA exerted a synergistic effect on metal extraction during composite washing.

Keywords Soilwashing . Heavy metals . Cd . Pb . Composite washing . Washing mechanism

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