| Soil washing is considered as one of the most suitable and functional techniques for removing heavy metal. In this paper, contaminated soils by the heavy metals of Pb, Zn, Cu, Cd were collected from the surroundings of a lead-zinc dressing plant in Shuikou Hill，Hunan Province. And the removal effects of the organic acid on heavy metal as a function of concentration, time and liquid-solid ratio by soil washing were studied. The results showed that the citric acid and the tartaric acid had a sound effectiveness, whereas the removal rate of oxalic acid was very low. The Cd removal rate by the citric acid and the tartaric acid were the best, with the removal rate 61.5% and 55.25% respectively. The removal efficiency was gradually improved as a function of time. Best effect was obtained in 8 hours. The removal capacity order of the citric acid and the tartaric acid was：Cd>Zn>Pb>Cu, for the citric acid, the removal rate was 59.5%, 49.33%, 43.48% and for the tartaricacid, the removal rate was 58.75%, 46.4%, 35.86% and 34.4%, separately. Meanwhile, it was also found that solid-liquid ratio had little influence on the removal rate of heavy metal. |
