Development of a cost-effective bipolar electrocoagulation system for enhanced hexavalent chromium removal: empirical modeling and statistical optimization

Hexavalent chromium (Cr(VI)) poses a significant threat to aquatic life and human health due to its high toxicity and carcinogenicity. This study develops and optimizes a bipolar electrocoagulation (EC) system using iron electrodes for the efficient and low-cost removal of Cr(VI) from aqueous solutions. Through a series of batch experiments, the effects of key operational parameters—including initial Cr (VI) concentration, pH, electrolysis time, and supporting electrolytes—were systematically investigated. Under optimized conditions (20 mg/L Cr(VI), pH 2, 0.5 g NaCl, 750 rpm stirring, nine iron electrodes, and 43.4 A/m2 current density), nearly complete removal (> 99%) was achieved within 7 min. Energy-dispersive X-ray spectroscopy (EDX) confirmed the formation of Fe(OH)3 flocs responsible for Cr (VI) adsorption. The total operating cost was calculated to be 0.97 US$/m3, indicating the method’s economic viability. Statistical modeling using univariate and multivariate analyses, along with Response Surface Methodology (RSM), identified the most influential parameters and yielded an empirical equation capable of predicting removal efficiency with a regression coefficient R = 0.9366. The process was further validated using real seawater and industrial wastewater, where Cr(VI) removal efficiency remained above 99%. These findings suggest that the proposed EC system offers a practical, scalable, and cost-effective solution for Cr(VI) removal in water and wastewater treatment applications.