Achieved advanced wastewater phosphate removal via improved ionic interference resistance in a migration-electric-field assisted electrocoagulation (MEAEC) system with modified-biochar pseudocapacitor electrode

The capacitive deionization-assisted electrocoagulation system has promising application potential in advanced phosphate removal of its low electricity consumption and sacrificial anode material. Phosphate removal in wastewater is crucial since excess phosphate might lead to eutrophication. However, the complex ion composition in raw wastewater can influence the effective phosphate removal by competing with the precipitable metal ions during electrocoagulation. In this study, a novel migration electric-field assisted electrocoagulation (MEAEC) with an assisted capacitive electrode made of N-doped and Fe-La co-modified biochar (LFNB) to achieve specific phosphate electro-adsorption for effective advanced phosphate removal. The LFNB-MEAEC achieved ultrahigh phosphate removal with the effluent of 0.1 mg/L in synthetic and raw municipal wastewater and met the first Grade A standard of total phosphate in the discharge standard of pollutants for municipal wastewater treatment plant (DSPMWTP) in China. The commonly observed coexisting ions in wastewater and a pH range of 2–12 did not significantly fluctuate the phosphate removal of LFNB-MEAEC. Cyclic voltammetry and charging-discharging tests confirmed the high phosphate affinity and excellent durability of LFNB in ion-interference circumstances. The MEAEC assisted with selective-adsorption capacitive electrodes and provided an effective and practical method for advanced phosphate removal from low-phosphorus-contaminated wastewater. The MEAEC with a selective-adsorbed capacitive electrode improved phosphate removal by 21 % (from 74 ± 1.7% to 95 ± 1.0%), reduced the energy consumption by 65.7% (0.012 kWh m⁻³-wastewater), and saved the sacrificial anode material by 67.5% (from 200 to 65 g m⁻³-wastewater) than those of MEAEC without phosphate-selective electrode in the same period (Sacrificial anode working time 200 s).