三种无机萃取剂去除土壤中PbCd的条件研究

通过对重金属污染土壤的萃取实验，比较了HCl、Na2S2O3、CaCl2 3种常用无机萃取剂对重金属Ph和cd的萃取效果，并通过改变萃取条件（萃取剂浓度、时间、固液比、萃取次数和温度），以期找到各种萃取剂达到最大萃取效率时所需的萃取条件。结果表明，萃取剂浓度对于萃取效率的影响最大，随着浓度的提高，3种萃取剂对Ph、Cd的去除作用增强；固液比和萃取次数对Ph、Cd的去除率也有较大的影响；时间对两金属的去除率也有一定的影响，但在本实验条件下，达到萃取平衡所需时间很短；温度对萃取效率的影响很小。本实验中，HCl去除Pb、Cd的能力远远大于其他两种萃取剂。对Cd进行萃取时，需增加萃取次数才能达到较好的萃取效果。

Extraction Conditions for Pb and Cd Removal from a Heavy Metal Contaminated Soil by Using Three Inorganic Extractants

In order to investigate removal efficiency of soil Pb and Cd by using three common extractants, such as HCl, Na2S2O3 and CaCl2, an extraction experiment was conducted in a soft which had been contaminated by heavy metals. Extraction conditions, including extractant concentration, extracting time length, solid-liquid ratios, times of extracting and temperature, were changed to get the condition combinations which the maximum extraction rate was reached for three extraetants. The results showed that extractant concentration was the most important influential factor. With increase in extractant concentration, removal efficiency of soil Pb and Cd increased significantly. Solid-liquid ratio and times of extraction also had a great impact on removal efficiency of Pb and Cd. Extracting time length could affect removal efficiency of the two metals; in this experiment, however, the time length of reaching extraction equilibrium was very short. Temperature had little impact on removal of Pb and Cd. For all three extractants, the extraction condition combinations for removal of soil Pb and Cd in this experiment were as follows ：extractant concentration was 100 mmol·L^-1, temperature was 30℃, extracting time was 1 h, solid-liquid ratio was 1：10, and times of extraction were two or three times consecutively. In the experiment, HCl was much more effective than the other two extractants. The removal efficiencies of HCl for soil Pb and Cd were 53.6% and 83.2%, respectively, under the conditions described above. For Cd, increasing extracting times could have a higher removal efficiency.