Electrochemistry-flushing Remediation Of Chromium-Contaminated Soil

Heavy metal contamination of soils has become a serious environmental problem in our country. Remediation of heavy metal-contaminated soil has attracted extensive attention. Current remediation technologies are difficult to achieve the goal of soil remediation, therefore, the high efficient remediation technology is the research direction of soil remediation. In this paper, a new technology using electrochemistry principles to remediate Cr(VI)-contaminated soil, electrochemistry-flushing(E-flushing) technology, is proposed. And Cr(VI) desorption kinetics experiments, soil flushing experiments and E-flushing experiments were conducted to study the feasibility of E-flushing technology for remedying historically Cr(?)-contaminated soil from a real contaminated site.The hexavalent chromium desorption kinetics experiments showed that the raise of pH and temperature significantly improved the efficiency of desorption of hexavalent chromium in the soil(pH=8.5~11.0?T=28?~90?). Temperature and pH are the important factors in hexavalent chromium desorption kinetics experiments.Flushing experiments showed that the hexavalent chromium removal in Flushing(S)(15 min), Flushing(M)(30 min) and Flushing(L)(60 min) were 13.5 ±1.9%, 16.0 ± 4.8% and 16.8 ± 2.9% respectively. Compared with the Cr(VI) desorption kinetics, only about half of desorpable Cr(VI) were removed from the soil. Parts of trivalent chromium was removed in flushing.E-flushing experiments showed that the hexavalent chromium removal in E-flushing(S)(15 min), E-flushing(M)(30 min) and E-flushing(L)(60 min) were 30.5±3.2 %, 36.0±3.8% and 37.9±1.9 % respectively, more than double of flushing experiments. Compared with the Cr(VI) desorption kinetics, most of desorpable Cr(VI) were removed from the soil. The removal rates of total chromium in those three groups were 41.6 ±11.3%, 42.9 ± 19.5% and 18.2 ± 5.9%, respectively. It means that a large quantity of trivalent chromium was washed out of the soil as well.In E-flushing technology, all electrode reaction products, electrochemistry process(electromigration)_and electrochemistry effect(joule heating) are positively to enhance the removal of Cr(VI). This study demonstrates that the E-flushing technology is feasible to remedy Cr( ?)-contaminated soil and features high efficiency and remediation rate. So E-flushing technology is worth further development.