Affiliations: Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China | Department of Applied Geology, Karlsruhe University, Karlsruhe, Germany
Abstract: This report examined electrochemical remediation of copper contaminated kaolinite by controlling electrolytes' pH for both of anolyte and catholyte simultaneously. Results showed that electrokinetic process and remediation efficiency varied obviously when different buffer systems, including citric acid (test 1), nitric acid + EDTA (test 2) and nitric acid (test 3), were used to control catholyte pH and Na2CO3 was used at the same time to control all anolyte one. It was found that under such pH condition soil's pH in soil column kept at 3.0–7.0 successfully, and correspondingly no copper precipitation and decrease of soil electroconductivity appeared, which are usually observed in electrokinetic process due to OH- introduction into soil column by electrochemical reaction occurred in cathode. Electroosmosis flow rates were almost equal for these three tests, indicating that these buffers did not affect Zeta-potential of kaolinite within the examined duration. More acid and basic solution was added into electrokinetic cell when nitric acid was used as buffer than when nitric acid + EDTA and then citric acid were used. Due to introduction of large amounts of ions into soil column, significant higher current was observed for test 3 than other two. Analysis of copper speciation and total quantity in kaolinite indicated that 55.65%, 22.5% and 23.74% Cu were removed from kaolinite for test 1, test 2 and test 3 respectively after only 10 days' electrokinetic remediation.