碱溶液对As污染土壤的化学萃取修复

Study on the remediation effect of alkali solution on the arsenic-contaminated soil

通过实验室浸泡试验,研究了0～200 mmol/L的NH_3·H_2O和KOH溶液对As污染土壤的化学萃取修复效果,同时分析了碱溶液萃取导致的土壤pH值变化以及土壤组分Ca、Mg、Fe、Al、Si的溶出情况。结果表明,NH_3·H_2O溶液仅能去除很少的土壤As,KOH溶液对土壤As的去除效果则较好。5～200 mmol/L的NH_3·H_2O和KOH溶液对土壤As的去除率分别为1.47%～4.44%和2.32%～23.33%。碱溶液能有效去除土壤As是由于OH-的作用。NH_3·H_2O和KOH溶液萃取导致土壤pH值增加,以及土壤中Fe、Al和Si不同程度地溶出,而KOH溶液导致土壤pH值增加和Al、Si溶出的作用明显大于NH_3·H_2O溶液。研究表明,采用KOH溶液萃取能有效修复As污染土壤,但应密切关注KOH溶液对土壤的负面影响。

The present paper intends to report our study results on the remediation effect of alkali solution on the amenic-contaminated soil through our laboratory immersion experiments. The other specific goals of our experiments are aimed at evaluating negative effects of the two alkali solutions on the variations of soil pH value and dissolution of soil components, namely, Ca, Mg, Fe, AI and Si. The operational parameters of the immersion experiment we have gained can be shown as follows： the concentration of alkali solutions was 0 - 200 mmol/L, the ratio of alkali solution volume （mL） to the soil mass （g） was 10：1 whereas the operational temperature was （20 ±0.5） ℃ with the reaction time being 6 h. The results show that NH3· H2O solution helps to remove As from the soil insignificantly, but KOH solution is effective in removing As from it. With the increase of the concentration of alkali solution, the removal rate of As tends to increase. For example, under the concentration of 5 - 200 mmol/L, NH3·H2O and KOH solutions may reach 1.47% - 4.44% and 2.32% - 23.33% of As removal rate, respectively. The effectiveness of alkali solution in removing As could be attributed to its function as a donor of OH- . However, in the immersion experiments, these two alkali solutions turned to result in increasing the soil＇s pH value and dissolution of some soil components. 5 - 200 mmol/L NH3 · H2O and KOH solutions result in less dissolution of Ca and Mg and more dissolution of Fe, Al and Si. Therefore, it is more significant to increase the soil pH value and dissolution of Al and Si by using KOH solution than that using NH3·H2O solution. In conclusion, KOH solution proves to be effective in removing As from soil, while the negative effects of KOH on soil should be given close attention to.