Application of nickel foam cathode modified by single-wall carbon nanotube in electro-Fenton process coupled with anodic oxidation: Enhancing organic pollutants removal

Abstract

Herein, an electro-Fenton process combined with anodic oxidation was proposed to remove organic contaminants from water sources. Methylene blue (MB) was selected as the target contaminant for removal optimization of the system. Furthermore, to find the effectiveness of the system for pollutant degradation, some micro-pollutants were tested under optimum conditions. PbO2@Ti was used as the anode, and different types of carbonaceous materials such as single-wall carbon nanotube (SWCNT), multi-wall carbon nanotube (MWCNT), carbon black (CB), graphitic carbon nitride, and expanded graphite were coated on nickel foam cathode. FESEM, EDS, and XRD analyses were conducted for surface characterization of the electrodes. CB covered by SWCNT was observed on the surface of the optimally modified cathode. The amount of hydrogen peroxide generated in the system with both SWCNT and CB was 3.3, 7.3, and 11.5 times greater than in the system with just SWCNT, MWCNT, and CB, respectively. The effect of different parameters, such as initial pH, ferrous ion, and current density was investigated. After the degradation of the contaminant, the solution pH was adjusted to 7, and a significant amount of by-products was precipitated. Under the optimum conditions (pH: 3.0, Fe(Ⅱ): 0.5 mmol/L, and current density: 10 mA cm−2), 94.1 % of MB and 80.0 % of TOC were removed within an hour. Also, under the optimal conditions, removal efficiencies of 63.1, 70.2, 76.4, 84.0, and 97.3 % were obtained for tetracycline, phenol, bisphenol A, 4-chlorophenol, and amoxicillin, respectively, indicating that the proposed system is also able to remove other organic pollutants efficiently.