复合材料对砷污染土壤稳定化处理及机理研究

通过投加FeS、电石渣、菌渣及其复配组合对砷污染土壤进行稳定化处理,根据稳定效率对稳定材料进行筛选,并分析处理前后土壤中砷的生物有效性、赋存形态及土壤物相成分,探索稳定机理.结果表明:单因素实验中,FeS对砷的稳定效率最高,当FeS投加量为n(Fe)/n(As)=20时,砷的稳定效率达84.69%;复配实验中,FeS投加量为n(Fe)/n(As)=15,电石渣投加量为0.5%(质量分数),菌渣投加量为6%(质量分数)时,砷的稳定效率高达90.53%.机理研究表明:稳定处理后,土壤中有效态砷和有机体内砷的可给量分别降低80.14%和92.86%;土壤中易溶态砷占总砷的比例降低了18.61%,铁型砷和钙型砷占总砷的比例分别提高了10.36%和5.81%,易溶态砷主要转化为铁型砷和钙型砷;稳定处理后土壤中矿物成分新增了Ca Al_2Si_2O_8·4H_2O(斜方钙沸石)、Ca_3Fe_4(AsO_4)_4(OH)_6·3H_2O(菱砷铁矿)、Fe_2(AsO_4)(SO_4)OH·5H_2O(砷铁矾矿)、(Al,Fe~(3+))_3AsO_4(OH)_6·5H_2O(砷铁铝矿)4种矿物,稳定处理使土壤中的砷生成了难溶性铁-砷、钙-砷矿物质.

Stabilization treatment to As-contaminated soil and its mechanism by composite materials

Three kinds of stabilization reagents, including FeS, carbide slags, and mushroom wastes and their complex mixture were used to stabilize arsenic in the contaminated soil, and the stabilization efficiency of arsenic was evaluated. In addition, the bio-availability, morphology and mineral compositions of the soil before and after treatment were analyzed to explore stabilization mechanism. The results showed that FeS had the best stabilization efficiency (84.69%) with molar raio of 20:1 (n(Fe):n(As)) in the single-element experiments. In the complex-element experiment, stabilization efficiency reached up to 90.53% with the molar raio of 15:1(n(Fe):n(As)), and mass ratio of carbide slags and mushroom wastes of 0.5%(w/w) and 6%(w/w), respectively. After stabilization treatment, effective arsenic and organic-available arsenic reduced by 80.14% and 92.86%, respectively. AE-As reduced by 18.61%, while Fe-As and Ca-As increased by 10.36% and 5.81%, respectively. Arsenic was mainly transformed from AE-As into Fe-As and Ca-As. The new minerals of CaAl₂Si₂O₈·4H₂O, Ca₃Fe₄(AsO₄)₄(OH)₆·3H₂O, Fe₂(AsO₄)(SO₄)OH·5H₂O and (Al,Fe³⁺)₃AsO₄(OH)₆·5H₂O were generated in the contaminated soils after stabilization treatment. Stabilization treatment helped to improve arsenic mineralization.