Simultaneous removal of phosphorus, chromium (Ⅵ), and antimony (Ⅴ) from textile dye wastewater by electrocoagulation

Concerns have been raised regarding the biological and environmental risks posed by phosphorus (P), chromium (Cr(VI)), and antimony (Sb(V)) in textile dye wastewater. However, achieving the simultaneous removal of P, Cr(VI), and Sb(V) remains challenging, and the interactions among these pollutants are not well understood. We investigated electrocoagulation as a method for the simultaneous removal of these pollutants, utilizing response surface methodology to optimize operating parameters. All pollutants were removed completely under optimal conditions: an initial pH of 3.0, current density of 32.43 A/m², NaCl concentration of 8.0 g/L, and reaction time of 20 minutes, with an energy consumption of 0.187 kWh/m³ -significantly lower than most reported values. The direct precipitation of FePO₄ and the adsorptive co-precipitation of Fe(OH)₃ synergistically contributed to P removal. The presence of Cr(VI) and Sb(V) accelerated Fe(OH)₃ floc agglomeration by oxidizing Fe^2 + to Fe³⁺ and enhancing Fe utilization, respectively, thereby improving P removal efficiency. Internal adsorption co-precipitation by Fe(OH)₃ was the dominant mechanism for Cr(VI) and Sb(V) removal, accounting for 89.97 % and 66.90 %, respectively. However, the presence of P inhibited Cr(VI) and Sb(V) removal by reducing Fe(OH)₃ floc formation due to competition with Fe³ ⁺. These findings elucidate the simultaneous removal mechanisms and mutual interactions of P, Cr(VI), and Sb(V), offering valuable insights for the treatment of textile dye wastewater.