石膏钙源微生物固化/稳定化锌污染粉土试验研究

Experimental investigation on microbial solidification/stabilization of zinc-contaminated silt using gypsum calcium source

微生物固化/稳定化重金属污染土时,反应速率过快和高浓度盐离子对细菌活性的抑制作用是阻碍单次搅拌工艺应用的关键问题。采用低溶解度的石膏(二水硫酸钙)作为钙源,以钙盐掺量和锌污染浓度为控制变量,进行微生物单次搅拌固化/稳定化锌污染粉土试验,研究固化/稳定化锌污染粉土的强度、锌离子浸出浓度和形态的变化规律。试验结果表明,锌污染浓度为500 mg/kg的污染粉土固化强度较处理前提高了77.3%,锌离子浸出浓度较处理前降低了87.3%;固化/稳定化后,锌污染粉土强度大幅提升,重金属锌迁移性明显降低;固化/稳定化锌污染粉土中有碳酸钙、碳酸锌和碱式碳酸锌生成,碳酸盐晶体聚集形成多孔簇状团聚体。研究结果表明,基于石膏钙源的单次搅拌微生物矿化处理能够有效固化/稳定化锌污染粉土,具有良好的应用潜力。

In the process of microbial solidification and stabilization of heavy metal contaminated soil,the rapid reaction rate and the inhibition of high concentration of salt ions on bacterial activity are the key problems that hinder the application of single stirring process.The solidification and stabilization tests of zinc-contaminated silt were carried out by using the single-stage microbial stirring method.In the tests,low-solubility gypsum(calcium sulfate dihydrate) was used as the calcium source for the microbially induced mineralization reaction,and the calcium salt content and zinc pollution concentration were adopted as the control variables to investigate the changes in soil strength,zinc ion leaching concentration and chemical forms.The results show that the solidification strength of 500 mg/kg zinc-contaminated silt is 77.3% higher than that of untreated zinccontaminated silt.Meanwhile,the concentration of zinc ion leaching is 87.3% lower than that of untreated zinccontaminated silt.After solidification and stabilization,the strength of zinc-contaminated silt dramatically improved and the migration of heavy metal zinc in soil significantly decreased.Calcium carbonate,zinc carbonate and basic zinc carbonate are formed in the solidified and stabilized zinc-contaminated silt,and carbonate crystals aggregate to form porous clusters.The single stirring method microbial mineralization treatment based on gypsum calcium source can effectively solidify and stabilize zinc-contaminated silt.This technique has potential application in solidifying/stabilizing zinc-contaminated silty soil site.