A continuous electrocoagulation system with pH auto-adjusting by endogenous products to treat Cr(VI)-contaminated soil flushing solution

摘要

Graphical abstractDisplay OmittedHighlights?An on-site application-oriented continuous electrocoagulation system.?pH auto-adjusting simplifies the operation and maintenance of the system.?Adjust pHs of reduction region and precipitation region with endogenous products.?The treated SFS complies with environmental legislation for discharges.?Treated SFS demonstrated better flushing effectiveness than fresh tap water.AbstractSoil flushing solution (SFS) from Cr(VI)-contaminated soil flushing remediation is a kind of non-industry-sourcing Cr(VI)-containing wastewater. The requirement of on-site treatment of SFS proposes high level requirements for the operational simplicity and transportability. This paper exhibits an on-site application-oriented continuous electrocoagulation (EC) system for SFS treatment. By a novel design, the products of a series of electrochemical, redox and precipitation reactions were used to create an acidic region for Cr(VI) reduction by Fe2+and a basic region for CrxFey(OH)zprecipitation. The concentrations of Cr(VI), total Cr and total suspended solids in the treated SFS were less than 0.03mg·L?1, 0.16mg·L?1and 39mg·L?1respectively, complying with the typical environmental legislation for discharges. Experiments of stirring intensity effect shows that stirring is necessary to decrease Cr(VI)/TCr in sediments. Comparison of desorption kinetics between treated SFS and tap water shows that the Cr(VI) desorption efficiency with treated SFS is slightly higher than with fresh tap water, meeting the requirement for the reuse of SFS. Compared with other continuous EC systems, this continuous EC system eliminates the requirement of pH monitoring and adjusting and improves operational simplicity and transportability.]]>