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

Abstract

In this work, a novel porous-structure electrochemical PbO₂ filter (PEF-PbO₂) was developed to achieve the reuse of bio-treated textile wastewater. The characterization of PEF-PbO₂ 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-PbO₂ possesses a larger electroactive area (4.09 times) than the conventional electrochemical PbO₂ filter (EF-PbO₂) 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, Na₂SO₄ 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-PbO₂ was durable and energy-efficient in practical applications. Mechanism study by simulation calculation illustrated that the part of the pore of the PEF-PbO₂'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.

Keywords: Electric energy consumption; Electrochemical filter; Electrochemical treatment; Reuse; Simulation calculation; Textile wastewater.