Three chambered fuel cell for desalination coupled urea oxidation and hexavalent chromium remediation

Abstract

Proof-of-concept of a fuel cell type electrochemical cell is demonstrated for simultaneous wastewater treatment and desalination. The electrochemical desalination cell (EDC) utilized the potential difference and concentration gradient between three chosen waste streams to convert their inherent chemical energy into electrical energy. Urea/cow urine was chosen as a potential electron donor, Cr(VI) was an electron acceptor, and synthetic NaCl/seawater solution (in the middle chamber) established a three-compartment EDC. The effect of a wide range of brine (5 to 35 g/L) and Cr(VI) concentrations (200 to 1000 mg/L) on desalination performance and Cr(VI) reduction were comprehensively investigated. When fed with urea, Cr(VI) reduction of 96.2 ± 0.4 % (with an initial concentration of 1000 mg/L) and salt removal of 63.1 ± 0.2 % (with brine concentration of 35 g/L) were observed (in 4 h) with a maximum power of 15.2 mW (for 21 cm2 electrode). A 12 L benchtop prototype with six anode-cathode configurations was demonstrated. Cr(VI) reduction of 95.2 ± 2 % and desalination of 70.7 ± 0.2 % (in 20 h) with power generation of 55.2 mW was recorded. The economic analysis projection of the EDC presents a significant step toward the application of this technology in real systems.