Sustain. Environ. Res., 22(2), 85-89 (2012)
Shu-Fen Cheng, Chin-Yuan Huang and Min-Siou Lin
Soil, cation exchange capacity, cadmium, remediation
Ion exchange is commonly adopted to measure the cation-exchange capacity (CEC) of soil and to remediate soil that is contaminated by heavy metals. The sodium acetate-method is the most common method for determining soil CEC in Taiwan. Based on ion exchange theory, Na+ is not an ion with high exchange potential, which in fact raises a question regarding the effectiveness of the sodium acetate method to determine the CEC of soils that are contaminated by heavy metals. This investigation utilizes the chlorides and acetates of metal ions Na+, K+, NH4+, Mg+2, Ca+2, Al+3 and Fe+3 to extract cadmium from Cd-contaminated soils. The results indicate that sodium acetate extracts only 55% of exchangeable Cd, whereas FeCl3 and AlCl3 extract 86 and 83% respectively. These results indicate that a method in which FeCl3 is used to determine the Cd-contaminated soil CEC outperforms the sodium acetate method. For contaminated soils with a large amount of Cd that are bound to a fraction of Fe-Mn oxides, preliminary results suggest the use of AlCl3 and CaCl2 for sequential washing remediation can provide a high washing efficiency and avoid soil acidification.