Electrochemical advanced oxidation processes (EAOPs) are promising technologies for the elimination of organic pollutants in water, but the high cost of the catalysts and treatment process restrict their large-scale application. Herein, highly efficient carbon-based catalysts for EAOPs were obtained by directly pyrolyzing low-cost sewage sludge, over which the elimination rates were up to 98% for methyl orange (MO) and 88% for tetracycline (TC). A precise electrochemical testing system demonstrated that the S-9/Ti electrode with 1.2 g catalyst loading owns the specific energy consumption value for 98% MO (5 mg/L) degradation was only 0.0112 kWh/g, and the value for 88% TC (1*10 -4 M) degradation was only 0.0039 kWh/g, in 8 h. Furthermore, active species capture experiments demonstrated that the •OH and •O 2 – radicals produced over the catalysts were the main oxidants for the elimination of pollutants. This study broadens the horizon for the resource utilization of sewage sludge and provides a strategy to realize the concept of “treating pollution with waste”.
Anode materials are crucial to anodic oxidation for wastewater treatment. In this regard, stable boron and cobalt co-doped TiO 2 nanotube (B, Co-TNT) was prepared for the first time, and its lifetime was found increased significantly while electrocatalytic activity decreased with the increase of Co(NO 3 ) 2 in preparation from 1 to 10 mM. Characterized by scanning electron microscope (SEM), X-Ray Diffraction (XRD) and X-ray Photo-electronic Spectroscopy (XPS), B and Co content were optimized and successfully doped on TNT, which was more smooth without ripple with Co content of 0.038 mg/cm 2 in a valence of +2, and B atomic content of 2.17 at.% in form of Ti-B-O. This optimized anode enhanced electrode lifetime 122.8 times while the electrochemical activity decreased slightly when compared to the undoped TNT. The effects of current density, initial pH and initial 2,4-dichlorophenoxyacetic acid (2,4-D) concentration were investigated, and the mainly responsible radical for degradation was confirmed to be the surface OH on B, Co-TNT anode. This anode had better performance on the TOC removal, mineralization current density (MCE) and energy consumption (Ec) when compared with BDD, PbO 2 , DSA and Pt anodes, and it also presented a very stable degradation for 10 cycles oxidation of 20 mg/L 2,4-D with allowable Co leaching. Therefore, B, Co-TNT anode is a promising, stable, safety and cost-effective anode for application in electrochemical advanced oxidation processes (EAOPs).
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