Removal mechanism for chromium (VI) in groundwater with cost-effective iron-air fuel cell electrocoagulation

Metal-air fuel cell electrocoagulation is one of the most cost-effective and innovative treatment options for metals in water. Here, the removal mechanism of chromium (Cr(VI)) was assessed using an iron-air fuel cell electrocoagulation (IAFCEC) system. Simultaneously, the effects of such treatment were also investigated with respect to a list of parameters controlling groundwater quality. During the IAFCEC operation, in-situ production of stable iron hydroxides (e.g., maghemite, hematite, and goethite) was experienced due to the sacrificial oxidation of the iron anode electrode. Therefore, these iron hydroxides were responsible for direct co-precipitation of aqueous Cr(VI). The removal efficiency of the system was assessed by varying the initial concentrations of Cr(VI) such as 1, 5, and 10 mg L-1). The IAFCEC, when operated with low concentrations of competing anions (e.g., silicate, phosphate, magnesium, and calcium), was capable of treating 6 L of water containing 1 mg L-1 Cr(VI) per day with an operating cost of 0.2 USD m(-3). This study demonstrates the IAFCEC as one of the most cost-effective treatment methods for Cr(VI) removal based on evaluation of performance relative to other options commonly available.