Studies on the removal of arsenate from water through electrocoagulation using direct and alternating current

Using alternating current in an electrocoagulation process offers an alternative to conventional electrocoagulation processes, where the direct current is used. The main objective of the present investigation is to study the effects of alternating current (AC) and direct current (DC) on the removal efficiency of arsenate by electrocoagulation using magnesium as anode and cathode. The effect of current density, solution pH, temperature, co-existing ions, adsorption isotherm and kinetics has been studied. The optimum removal efficiency of 98.3% and 97.9% was achieved with the energy consumption of 0.724 and 1.035 kWh/m(3) at a current density of 0.2 A/dm(2), at pH of 7.0 for AC and DC, respectively. The adsorption of arsenate preferably fitting the Langmuir adsorption isotherm suggests monolayer coverage of adsorbed molecules for both AC and DC. The adsorption process follows second-order kinetics model with good correlation coefficient. Temperature studies showed that adsorption was endothermic and spontaneous in nature.