Removal of Chromium (VI) ions from Aqueous Solutions using Electrocoagulation System

Access to freshwater resources has been dwindling in recent years, owing in part to the rising population, industrial expansion, and the uncontrolled discharge of various contaminants into waterways. Chromium-containing wastewater, in particular, is one of the major environmental contaminants; it is an exceedingly hazardous metal in the form of Cr(VI) that causes serious environmental and health issues. As a result, the goal of this study was to remove chromium ions from an aqueous solution utilizing cost-effective and environmentally friendly electrocoagulation technology with iron and aluminium electrodes, as well as to assess its treatment capacities under a variety of parametric conditions. Under identical conditions, the chromium removal efficiency of iron and aluminium electrodes were evaluated. First, the results shows that removal efficiency improves with increasing agitation in the reaction tank and at an optimum electrode distance of 2 cm under both acidic and basic conditions. At optimum conditions (chromium concentration of 25 mg/L, electrode distance of 2 cm, 1.5 g electrolyte (NaCl), 9 V, and stirring speed of 400 rpm); an iron electrode removed 95% of the chromium ion at pH 8, while an aluminium electrode removed ~100% of the chromium ion at pH 3 in 60 minutes. To treat 200 mL of the aqueous solution containing 25 mg/L of chromium ions, the Fe and Al electrodes demonstrated 81.5% and 92.4% Faraday electrode efficiencies and consumed 7.2 kWh and 13.5 kWh electrical energy, respectively. The operating costs to treat an aqueous solution containing 200 mL of chromium ion were $ 1.26 per m3 for Al and $ 0.68 per m3 for Fe electrode, when considering the electrical energy consumed and the cost of electrodes. When the removal efficiencies, treatment duration, and treatment cost are considered, it can be stated that the electrocoagulation approach used here is efficient, cost effective, and simple to manage and maintain. In addition, using the adsorption approach, the sludge produced can be reconditioned and utilized as an adsorbent for water treatment.