EFFECT OF ORGANIC MATTER ON REMOVAL OF HEAVY METALS IN SOIL WITH ELECTROCHEMICAL PROCESS

Abstract

Abstract

This research presents the effect of organic matter (humic acid) as a surfactant on the electrochemical process for removal of Pb, Cd and Zn from mine tailing soil. The soil contained high concentrations of the target metal contaminants (Pb = 13365 mg kg⁻1, Cd = 15742 mg kg⁻¹ and Zn = 19565 mg kg⁻¹). The electrochemical tests were carried out in a specially designed electrokinetic reactor with two intermediate aqueous collection locations within the soil chamber using tap water and organic matter. Humic acid was added in soil as a surfactant in order to enhance the removal of lead, cadmium and zinc and it was applied at five percent. Humic acid was used with tap water as the pre-mixing agents of the contaminated soil. A constant DC voltage of 20 V (0.625 V/cm) was applied across the working electrodes in all the experiments for a treatment time of 48 h. The concentration accumulation of the metal species in the anode, cathode and the intermediate collection chambers were measured over time, as well as pH, conductivity and ORP. The removal efficiency was reported in percentage as the summation of the cumulative metal mass removed into all collection chambers in aqueous form, normalized to the initial mass of the metal in the soil.

Demir et al. [1] studied the effect of in situ electrochemical remediation in order to remove heavy metals from contaminated-soil by using only tap water. Their experimental results have indicated that total electrochemical removal of lead, cadmium, and zinc from soil using tap water was 35.59%, 78.09% and 55.09% respectively.

In this study, the total removal efficiency of the metal ions from soil mixed with tap water and humic acid were determined 20.07%, 68.47% and 49.61% for Pb, Cd and Zn, respectively. Comparing the results for two separate experiments, it can be concluded that the addition of humic acid results in the decline of metals mobility. When humic acid is added into soil, removal efficiencies of metals decrease about 15 percent for Pb, 10 percent for Cd and 6 percent for Zn.