Energy-efficient reuse of bio-treated textile wastewater by a porous-structure electrochemical PbO2 filter: Performance and mechanism

In this work, a novel porous-structure electrochemical PbO 2 filter (PEF-PbO 2 ) was developed to achieve the reuse of bio-treated textile wastewater. The characterization of PEF-PbO 2 confirmed that its coating has a variable pore size that increases with depth from the substrate, and the pores with a size of 5 μm account for the largest proportion. The study on the role of this unique structure illustrated that PEF-PbO 2 possesses a larger electroactive area (4.09 times) than the conventional electrochemical PbO 2 filter (EF-PbO 2 ) and enhanced mass transfer (1.39 times) in flow mode. The investigation of operating parameters with a special discussion of electric energy consumption suggested that the optimal conditions were a current density of 3 mA cm −2 , Na 2 SO 4 concentration of 10 g L −1 and pH value of 3, which resulted in 99.07% and 53.3% removal of Rhodamine B and TOC, respectively, together with an MCE TOC of 24.6%. A stable removal of 65.9% COD and 99.5% Rhodamine B with a low electric energy consumption of 5.19 kWh kg −1 COD under long-term reuse of bio-treated textile wastewater indicated that PEF-PbO 2 was durable and energy-efficient in practical applications. Mechanism study by simulation calculation illustrated that the part of the pore of the PEF-PbO 2 's coating with small size (5 μm) plays an important role in this excellent performance which provides the advantage of rich ·OH concentration, short pollutant diffusion distance and high contact possibility.