氯化钙-腐殖酸活化作用下土壤Cd的电动脱除性能

为了提高稻田土壤Cd的去除率,同时减小对土壤pH值的影响,采用氯化钙-腐殖酸复合活化液增强土壤Cd的可移动性,基于电动土工合成材料(EKG)电动排水脱除土壤Cd,重点考察了不同活化剂浓度和活化时间下,土壤有效态Cd含量以及土壤pH值的变化,研究了活化-电动排水后土壤Cd的电动脱除量、土壤全Cd含量、有效态Cd含量、土壤pH值的变化。研究结果表明:0.5%氯化钙-1%腐殖酸对土壤Cd的活化效果最佳,土壤有效态Cd含量可从0.30 mg/kg提高至0.44 mg/kg,而活化处理后的土壤pH值仅降低约0.4;排尽上覆水后,通过电动排水可进一步脱除土壤Cd,土壤Cd的电动脱除量为上覆水中Cd含量的3倍左右;活化-电动排水后,土壤全Cd含量从1.72 mg/kg降低至1.20 mg/kg左右,土壤有效态Cd含量降至0.27~0.31 mg/kg,各截面土壤pH值较为均一且变化不明显,介于5.45~6.30之间。研究所提出的方法可最大限度地脱除土壤Cd,提高稻田土壤Cd的去除率,同时减小对土壤pH值的影响,一定程度上保证了农作物的安全生产。

Performance of Electrokinetic Removal of Cadmium from Contaminated Soil Treated with CaCl2-Humic Acid

In an attempt to enhance the removal of Cadmium(Cd) from paddy field soil and meanwhile alleviate the influence on soil's pH value, we conducted electrokinetic removal test with CaCl₂-humic acid solution activating the mobility of Cd in soil. We observed the changes in the content of available Cd and the pH value of soil by changing the concentration of CaCl₂-humic acid and the time of activation. In addition, we examined the changes in the removed content of Cd, the total concentration of Cd , the concentration of available-state Cd, and the pH value of soil after activation and electrokinetic drainage. Results manifest that the solution with 0.5% CaCl₂ and 1% humic acid has an optimum activation effect on the Cd in soil, by raising the available-state Cd from 0.3 mg/kg to 0.44 mg/kg and cutting the pH value by only 0.4. After the drainage of the overlying water, Cd can be further removed by electrokinetic drainage. The electrokinetic removal content of Cd was about three times that in the overlying water. After both activation and electrokinetic drainage, the total content of Cd dropped from 1.72 mg/kg to about 1.20 mg/kg, the content of available-state Cd declined to 0.27-0.31 mg/kg, while the pH value of each section of the soil was relatively uniform and barely changed, ranging between 5.45 and 6.30. The present research method could maximize the removal of Cd in soil while reducing the impact on pH value, which ensures the safe production of crops.