生物炭负载铁锰双氧化物固化稳定化土壤中砷

砷(As)在土壤中的赋存形态复杂, 常规固化稳定化材料处理不同形态As时存在局限。针对该问题,通过整合生物炭(bio-char, BC)表面吸附-静电引力-络合螯合与铁锰双氧化物(ferric manganese binary oxides, FMBO)共沉淀-氧化还原作用, 制得负载了FMBO的BC新功能材料BC_FM, 并与硅酸盐水泥复配固化稳定化As, 利用响应面法探讨影响因素对处理效果的影响。结果表明:在BC_FM与硅酸盐水泥配比为9.88%和8.80%、养护20.53 d条件下, As浸出浓度最低为0.055 mg/L, 可交换态含量占比从4%降至0.5%, 残渣态含量占比从77%升至87%, 无侧限抗压强度>50 kPa。推测BC_FM固化稳定化机制为Fe-O(H)-As共沉淀、Mn-O(H)-As氧化和BC功能的联合作用。该研究结果可为长效固化稳定化As提供新的技术方案。

SOLIDIFICATION/STABILIZATION OF As IN SOIL USING BIOCHAR LOADED WITH FERRIC MANGANESE BINARY OXIDES(FMBO)

The chemical forms of arsenic (As) in soil environment were sophisticated, and there was a defect in the treatment of different forms of As with conventional solidification and stabilization materials. We integrated the surface adsorption of biochar (BC), pore filling, electrostatic attraction, complexation and co-precipitation oxidation-reduction of ferric manganese binary oxides (FMBO), then a new functional material BC_FM was prepared and stabilized with Portland cement. The effect of key parameters on treatment effect was discussed by response surface method. The results showed that when the ratio of BC_FM to Portland cement was 9.88% and 8.80%, and the curing time was 20.53 days, the minimum leaching concentration of As was 0.055 mg/L, the exchangeable state proportion was reduced from 4% to 0.5%, the residual state proportion was increased from 77% to 87%, and the unconfined compressive strength exceeded 50 kPa. It was speculated that the curing and stabilization mechanism of BC_FM was the combination of Fe-O(H)-As coprecipitation, Mn-O(H)-As oxidation and BC function. The results of this study provide a new technical scheme for long-term curing and stabilization of As.