Selection And Evaluation Of Arsenic/Antimony Solidification Stabilizer For Contaminated Soil In Cold Region

With the rapid development of industry and agriculture,more and more heavy metals enter the soil through metallurgical manufacturing,sewage irrigation,mining and other human production activities,resulting in increasingly serious soil heavy metal pollution.Solidification stabilization technology has good remediation effect and low cost,which is widely used in the remediation of heavy metal contaminated sites in China and abroad.Due to the extensive use of arsenic and antimony in mechanical manufacturing,metallurgical processing and other fields,the pollution problem is also more prominent,but the study of antimony solidification stabilization is relatively less.Therefore,this paper mainly takes antimony contaminated soil as the research object.Firstly,the effective stabilizer for antimony is selected,and the effects of different dosage,curing time and pollution concentration on heavy metal remediation are investigated.The selected stabilizers were compounded with curing agents and antifreeze additives,and the compound combination of curing stabilizers was selected under the condition of freezethaw cycle,and the optimal ratio of the three was explored.The selected reagents were applied to arsenic/antimony composite contaminated soil,providing reference for the research on solidification and stabilization of heavy metal contaminated soil and field practice.The stabilization efficiencies of ferrous sulfate and iron powder for antimony were93.3% and 79.8%,respectively.The leaching concentration of antimony decreased the most at the initial stage of curing,and the stabilization efficiency reached 92.3% and 76.8%after 1d of curing,respectively,which was basically stable after 7d of curing.Under the same pollution concentration,the addition of stabilizer was inversely proportional to the leaching concentration of antimony.The leaching concentration decreased greatly at low addition,and the decrease slowed down when the addition continued to increase.After ferrous sulfate and iron powder were repaired,the content of residual antimony increased by 23.5% and 13.0%,respectively,and the exchangeable state decreased to 1.0%.The bioavailability of antimony was greatly reduced,from 7.5% of the original contaminated soil to 4.4% and 4.0%,respectively,which effectively weakened the harm to human body.The repair effect of curing stabilizers with different combinations is different.The repair effect of curing stabilizer with ferrous sulfate+fly ash+calcium lignosulfonate is the best.After 40 freeze-thaw cycles,the stabilization efficiency of antimony is still as high as 88.1%,the compressive strength is 0.8Mpa,the content of antimony residue increases from 58.2% to 74.4%,and the content of weak crystalline iron increases by 4.5g/kg on average.The response surface experiment and analysis results show that the three factors have a very significant impact on the stabilization efficiency of antimony and the compressive strength of the specimen,and the most suitable ratio is 3.9:6:0.5.The freezethaw cycle promoted the transformation of antimony residual state to active form,promoted the aging of weak crystalline iron,thus promoted the dissolution of antimony and weakened the compressive strength of soil.It was observed by SEM that the solidified stabilizer made the soil structure dense,cemented well and enhanced the freeze-thaw resistance.The selected composite curing stabilizer has significant remediation effect on arsenic/antimony composite contaminated soil.After 40 freeze-thaw cycles,the leaching concentrations of arsenic and antimony can still meet the relevant provisions of groundwater standards and landfill standards.The average strength of soil with three pollution concentrations after remediation reached 1.1Mpa.The residual content of arsenic and antimony increased by 19.2% and 12.3% on average,and the carbonate bound state decreased by 12.3% and 10.3%.The content of other forms also decreased to varying degrees.Bioavailability decreased by 7.7% and 2.7% on average.The same amount of cement has poor repair effect on arsenic and antimony.Moreover,the selected composite curing stabilizer components are cheap and easy to obtain,and the utilization of fly ash reflects the principle of ’ waste control by waste ’ and low carbon.