The hindering effect of experimental strategies on advancement of alkaline front and electroosmotic flow during electrokinetic lake sediment treatment

Abstract

The current study focused on the hindering of alkaline front during electrokinetic copper migration in artificially contaminated lake sediments and the effect of several experimental strategies on electroosmotic flow. Fourteen laboratory scale experiments in triplicates were performed using plastic container where the distance between electrodes was 30 cm at 40 mA, 60 mA and 120 mA electric currents (under density of 0.15 mA cm −2, 0.23 mA cm −2 and 0.53 mA cm −2, respectively) with different Cu concentrations (500 mg kg −1, 1000 mg kg −1, 1500 mg kg −1, 2000 mg kg −1 and 2500 mg kg −1) for 14 days. Tests were conducted with/without electric current and with/without the employment of membranes or barriers. Selected membranes and barriers proved to be efficient in hindering the alkaline front and thus improving copper migration in the sediments. During electrokinetic treatment and the use of the nylon membrane 85% of Cu was removed from sediments. Additionally, 80% and 70% of Cu was removed when cation exchange membrane and filter paper barrier were used. During the electrokinetic treatment Cu as well as the electroosmotic flow was always directed towards the cathode. The highest electroosmotic flow was observed with the lowest (500 mg kg −1) Cu concentration. Moreover, the electroosmotic flow and electrical gradient increased with the increase in electric current and was found to be the highest at 120 mA. When there were no membranes, barriers or acid used, severe pH jump was observed at a normalized distance of 0.5–0.6 from the anode. However, when membranes or barriers were employed, there was no pH jump present in the sediments.