[Screening of the Reduction/Stabilization Reagent for Cr(Ⅵ) Contaminated Soil in a Planting Site and Reaction Process Monitoring].

There are lots of problems in the domestic remediation of Cr (Ⅵ) contaminated soil field,such as lack of the key processing parameters,poor long-term effect and so on.The Cr (Ⅵ) heavy polluted surface soil was sampled from an electroplating site in North-China,and then treated with five different reducing reagents.At the same time,the on-line ORP probes and interval sampling test were chosen to monitor the reaction process,and to explore the reaction rate and effect.The results showed that No.4 reagent had the highest Cr (Ⅵ) reduction effect,reaching up to 99.5%,and the minimum soil Cr (Ⅵ) concentration could reach 2.4 mg·kg-1.The No.1 and No.4 reagents had relatively faster reducing rates.There were obvious difference in ORP and pH monitoring values between different reductants,for example,the No.1 reagent kept the ORP value stable at around -400 mV.The No.4 reagent gradually increased the value from -200 mV to 100 mV since 30h,and then kept stable.According to the pH difference among different reductants,the No.4 reagent was the best and kept the pH value at around 7.Taking together the final effect and process key parameters,the No.4 reagent was the best.The scale-up experiment was operated with process monitoring,and the ORP and conductivity values showed that the reduction reaction took about 160 h.This work would provide theoretical basis for controlling the maintenance condition and reaction process in soil Cr (Ⅵ) remediation.