Determination of arsenic, lead and mercury in contaminated water via electrokinetic process

Abstract

Electrokinetic remediation is a method to remove heavy metals such as arsenic (As), lead (Pb) and mercury (Hg) by application of a constant direct current connected to the cathode and anode in the electrolyte solution. This experiment is conducted to remove the heavy metals in contaminated water under controlled time, types of electrodes, distance between electrodes and voltage applied in a laboratory scale. The parameters considered in electrokinetic experiments were zinc (Zn), aluminium (Al) and stainless steel as types of electrodes, electrodes spacing of 3 cm, 7 cm, and 9 cm, and the applied voltage of 30 V, 60 V, and 90 V in one hour treatment. The heavy metals were then extracted with several series of electrokinetic experiments to obtain the maximum removal of the metals. Heavy metal depositions in both electrodes were analysed using X-ray fluorescence (XRF) spectroscopy. The concentrations of heavy metals in the simulated contaminated water were analysed using inductively coupled plasma - optical emission spectroscopy (ICP-OES). It was found that the stainless steel as electrode, 5 cm for the distance between electrodes and 90 V for the voltage provide the optimal condition. When the optimal parameters were applied to contaminated water of Sungai Masai, Johor, the study found the presence of As and Hg at 4.46 ppm and 2.08 ppm concentration, respectively, but Pb was not detected. Later, all Hg was removed in the electrokinetic remediation experiment. In summary, voltage, spacing and type of electrode affect the heavy metals removal in contaminated water.