Effects of CaCl2 on concentration and speciation of soil Cd around a Pb-Zn mine

Abstract

Abstract Remediation of Cd contaminated soil around mines is still the current academic focus. In order to discuss the activation and extraction effects of CaCl2 on concentration and speciation of soil Cd around a Pb-Zn mine, field investigation and soil sample collection were conducted. Batch experiment was used to study the influence of concentration and time on Cd activation and extraction. Cd contents were analysed. And Cd species were extracted by sequential extraction procedures. Results show that there are obvious concentration effect and time effect for Cd extraction by CaCl2. The best choice of CaCl2 concentration is 0.1 mol/L. And the best extraction time is 4h. Results also show that the percentage and content of exchangeable Cd is the lowest with the value of 9.1% and 0.16 mg/kg when the CaCl2 content is 0.1 mol/L. And the percentage and content of exchangeable Cd is the lowest with the value of 10.5% and 0.18 mg/kg when the extraction time is 4h. It is found that transformation of Cd species such as exchangeable, carbonates bound and Fe-Mn oxides bound should be the main reasons of concentration effect and time effect. And the extraction of soil Cd around a Pb-Zn mine by CaCl2 is a complex coupling process of dissolution, ion exchange, desorption, acidolysis, oxidation-reduction and complexation, etc. All of these above will aid to provide a basis for the research, development and application of remediation technology for Cd contaminated soil around this and other Pb-Zn mines.