Solar powered electrokinetic remediation of Cu polluted soil using a novel anode configuration

• A novel approach (Two Anode Technique (TAT)) is used to enhance electrokinetic remediation of soil contaminated with copper.
• A secondary electrode is used in TAT and placed near the cathode.
• The role of the secondary anode is to generate hydrogen ions in the vicinity of the cathode.
• The hydrogen ions generated by the secondary anode neutralized the hydroxyl ions formed at the cathode.
• High copper removal was observed in the tests using TAT set up compared to conventional method setup (Anode cathode).
• Solar panels were used to generate power for the remediation process.

This study investigated a novel approach, two anodes technique (TAT), to hinder the base front advancement during electrokinetics in order to enhance the removal of copper (Cu) from a contaminated soil. Four series of tests were carried out using energy consumptions of 500, 750, 1000, and 1250 Whr. The tests were performed with continuous and intermittent currents. Three identical electrokinetic cells were used to carry out the TAT tests as well as tests with conventional anode-cathode (CAC) configuration for comparison. Copper was used to artificially contaminate the soil (355 mg copper per kg of dry soil) due to the abundance of copper pollution sites and its ease of handling. Solar cell panels were used to generate the electric field required for the electrokinetic remediation process. At the end of each test, the soil was extruded from the cell and divided into four equal sections. Soil from each section was tested for water content, pH, and copper concentration. Part of the soil was squeezed and the pore fluid was collected and analyzed for pH and copper concentration. The results show that solar cells can provide electric field sufficient for electrokinetic remediation of Cu-contaminated soil. Tests conducted using intermittent current showed lower pH values in the soil sections along with higher copper removal compared to tests performed with a continuous current for the same energy consumption. Higher copper removal was observed in TAT tests compared to CAC tests. It was found that the position of the secondary anode influenced the outcome of TAT test. Placing the secondary anode at 15 mm from the cathode was found to achieve higher copper removal than placing it at 50 mm from the cathode. The TAT technique was successful in removing the copper from 75% of the soil with the highest removal of 92% occurring near the anode. A comparison of copper removal from the TAT and CAC tests clearly showed that TAT was effective in combating the advancement of the base front and therefore minimizing premature copper precipitation.