Electrokinetic Remediation Of Chromium Contaminated Soil

This study aims to select functional materials to build bipolar electrode and analyze the effects that the bipolar electrode and humid acid have on the Ph?Eh and the transferring and transforming of chromium during the electrokinetic remediation process.The main conclusion is as follows:On the condition that no reducing agents exist in the soil,at the low voltage time,still a part of Cr 6+ is reduced in the remediation reaction process,but the amount of reduction of chromium is relatively small,which accounts for 4.0-12.1% of total chromium in the soil.As the voltage is increased,the transferring of Cr 6+ in the soil is improved,which enhances the effect of the removal of total chromium in the soil and the reduction of Cr 6+.When humid acid is added to the soil,the amount of reduction of Cr 6+ increases significantly.The reduction rate is up to 16.2%-27.3%;After adding humid acid,the content of Cr6+ in the soil decreases significantly,which improves the removal of Cr6+ in the soil;With a voltage of 1.0-2.0V/cm,humid acid increases the removal rate of total chromium in a certain way,but not significantly.When activated carbon is used to build bipolar electrode,the massive surface area and the excellent adsorption of the bipolar activated carbon electrode can be used to make the Cr6+ transferred to the anode area adsorb quickly to the surface of activated carbon and redox reaction takes place,which produces Cr3+,decreases the density of Cr3+ in the anode area and promotes the continuous transferring of Cr6+ from cathode to anode;In the meanwhile,the activated carbon in the bipolar electrode reacts with H+ produced in water electrolysis,which effectively slows down the speed of the decrease in pH in the soil of the anode area and the increase in the electric potential of redox reaction.When iron chips are used to build bipolar electrode,the great reduction ability of the bipolar electrode can be used to make the Cr6+ transferred to the anode area react quickly with the iron chips,producing Cr3+,thus decreases the density of Cr3+in the anode area and promotes the continuous transferring of Cr6+ from cathode to anode,in the meanwhile consumes the H+ produced in water electrolysis,which effectively slows down the speed of the decrease in pH in the soil of the anode area and the increase in the electric potential of redox reaction.Through building bipolar electrode,the removal effect can be improved significantly.With a voltage of 1.0-2.0V/cm,the removal rates of total chromium and Cr6+ both show that: treatment with the activated carbon bipolar electrode > treatment with the iron chips bipolar electrode > treatment with ordinary bipolar electrode.