Migration electric-field assisted electrocoagulation with sponge biochar capacitive electrode for advanced wastewater phosphorus removal.

Migrating electric field-assisted electrocoagulation (MEAEC) is a three-electrode electrochemical system, including waste flour-derived sponge biochar (SBC) as an adsorption electrode for efficient phosphorus removal from wastewater. The SBC was applied in the MEAEC system as a pseudo capacitance electrode with low energy consumption and reached an excellent effluent level (0.12 mg/L) with a 200-s treatment time in 1 mg/L phosphate synthetic wastewater. The SBC adsorption electrode had a total charge capacitance of 1.14 F/g with abundant micropores. Continuous charging and discharging at a constant voltage over 100 cycles demonstrated the excellent durability of the biochar electrodes. The energy demand of SBC-MEAEC was only 0.0058 kWh/m3 for 90% phosphate removal, which was 65% less than that of the control. The use of SBC in the MEAEC system greatly enhanced phosphate removal at low concentrations. In the SBC-MEAEC system, the electro-desorption synchronous electrocoagulation process demonstrated efficient concentration and release of ions after electro-adsorption. These results indicate that MEAEC with an SBC electrode could achieve a high level of phosphate removal with a much lower energy consumption than in previous studies. The recovered concentrated phosphorus flocs also contained fewer metal impurities than those in previous electrochemical approaches. The proposed desorption synchronous electrocoagulation utilizing waste-derived SBC electrodes provides a cost-effective pathway to treat low phosphorous-containing wastewater.