铁盐类复合稳定剂对砷钙渣中As的稳定化作用及机理
Stabilization treatment of arsenic calcium residue using Fe-containing compound stabilizers
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摘要: 本实验以砷含量为5.09%的砷钙渣为对象,结合浸出毒性测试、XRD、SEM和砷形态分析,研究铁盐类复合稳定剂对砷钙渣中砷的稳定化处理效果及机理.结果表明,在铁盐类复合稳定剂用量30%、浓硫酸用量6.0 mL/100 g渣和水渣比4.5:10条件下,养护180 d内,处理后砷钙渣能够达到《危险废物填埋污染控制标准》(GB 18598-2019)的要求,且增重比和增容比分别为1.31和1.12.通过化学稳定化+胶凝固化实现As的稳定化,在稳定化处理过程中,有效态As向无定形铁铝氧化物结合态As的转变是As稳定化的主要机理;而稳定的砷酸钙化合物-毒石的生成和石膏结构中砷酸盐的掺入是As稳定化的辅助机理.同时,改性后的反应性矿物材料可生成水化硅酸钙凝胶,通过物理包封作用进一步抑制As的释放.Abstract: In this study, Fe-containing compound stabilizers were used to stablize arsenic calcium residue (ACR) with high arsenic (As) content (5.09%), and their stabilizing effects were evaluated by leaching toxicity test. The stabilization mechanism was discussed based on XRD, SEM and sequential extraction analysis. The results showed that at the parameters of 30 wt% Fe-containing compound stabilizers, 6.0 mL H2SO4 per 100 g ACR and water-to-slag ratio of 4.5:10, the treated ACR can meet the "Hazardous Waste Landfill Pollution Control Standard" (GB 18598-2019) within 180 curing days. And the weight gain ratio and the capacity increase ratio were 1.31 and 1.12, respectively. The stabilization of ACR was successfully achieved through by chemical stabilization and cementation solidification. During the stabilization process, the conversion of available As to amorphous Fe/Al hydroxides bonded As was the main mechanism of As stabilization. The formation of a stable calcium arsenate compound (Pharmacolite) and the incorporation of arsenate in the gypsum structure were the auxiliary mechanism of As stabilization. The modified reactive mineral material can generate calcium-silicate-hydrates gel, and further suppressed the release of As by physical encapsulation effect.
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Key words:
- arsenic calcium residue /
- compound stabilizers /
- stabilization /
- speciation
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