化学淋洗法对铀污染土壤的修复效果研究

采用振荡淋洗方法对三种粒径(+2mm、-2mm+0.15mm、-0.15mm)某尾矿库周边铀污染土壤进行去污试验,选用盐酸、硝酸、柠檬酸、草酸为淋洗剂,通过控制淋洗浓度、液固比、时间、温度、混合淋洗等因素来确定较优的淋洗条件。结果表明:各淋洗剂对铀污染土壤的去污效果为草酸盐酸硝酸柠檬酸;当淋洗浓度大于0.5mol/L、淋洗时间大于8h或液固比大于10∶1时,其淋洗效果都逐渐趋于稳定;提高淋洗温度可显著提升淋洗效果;选用草酸+盐酸和草酸+硝酸两组较优混合淋洗组合对全粒径土壤进行淋洗时,土壤中铀去除率均达50%以上,总含铀量分别降至27.15、24.32mg/kg,均达到土壤修复目标(40mg/kg)。

Study on Remediation Effect of Uranium Contaminated Soil by Chemical Elution

Oscillation leaching method was applied to conduct decontamination experiment for three kinds of particle size (+2 mm, -2 mm+0.15 mm, -0.15 mm) of contaminated soils surrounding uranium tailings. The optimum leaching conditions were obtained by single factor test through selection of hydrochloric acid, nitric acid, citric acid, and oxalic acid as eluting agent, and by controlling elution concentration, L/S, time, temperature, and mixture elution. The results show that removal effect of leaching agent on uranium contaminated soil is oxalic acid > hydrochloric acid > nitric acid > citric acid. When leaching concentration is 0.5 mol/L above and leaching time is 8 h above or L/S>10/1, elution effect gradually tends to be stable. Elution effect can be significantly improved by increasing leaching temperature. When two groups of oxalic acid + hydrochloric acid and oxalic acid + nitric acid are selected for elution agent, uranium removal rate in soil with full grain size is 50% above, and total uranium content drop to 27.15 and 24.32 mg/kg respectively, all of which reaches the soil remediation target (40 mg/kg).