Properties And Applications Of The Electro-Fenton-like System Based On FeOOH/AC Catalysts

With the characteristics of high organic concentration, high colority, poor biodegradability and biotoxicity of dye wastewater, the traditional biological methods are not always sufficient to complete remove all the pollutants, and therefore, many studies have focused on the search for novel and effective technologies.In recent years, advanced oxidation processes (AOPs) which make use of various combinations of ozone, hydrogen peroxide, UV, ultrasound, supercritical water, pulsed corona discharges, electron beam irradiation, etc. are becoming more and more important technologies for wastewater treatment. Among the most promising AOPs for wastewater treatment, electrochemical advanced oxidation processes (EAOPs) such as electro-Fenton reactions are particularly attractive. The homogeneous electro-Fenton process is greatly effective because reactions between hydroxyl radicals (·OH) formed in the medium and organics are usually very fast, which leads to the complete mineralization of organic pollutants forming the end clean-product of CO2 and H2O. However, the homogeneous Fenton process has significant disadvantages such as narrow working pH range, iron sludge treatment and iron ions deactivation. To overcome these drawbacks, some efforts have been made to develop different heterogeneous (photo-)Fenton-like catalysts.In this paper, the activated carbon (AC)-supported nano iron oxyhydroxide (FeOOH) catalyst was prepared by air oxidation of ferrous hydroxide (Fe(OH)2) suspension method. Characterization was performed using Brunauer-Emmertt-Teller (BET) specific surface analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), Fourier transform infrared spectrum (FT-IR) and inductively coupled plasma (ICP) technique to investigate the structural and surface properties of the resulting solid catalysts. The results indicated that the heterogeneous FeOOH/AC catalyst consists of goethite (α-FeOOH) and lepidocrocite (γ-FeOOH) mixed crystals. The adsorptive and electrochemically assisted oxidation properties of the solid FeOOH/AC catalysts were investigated by constructing the heterogeneous electrocatalytic wet H2O2 oxidation system for the degradations of RhB, amaranth azo dyes and actual pharmaceutical wastewater. The effects of temperature, FeOOH/AC catalyst dosage, solution pH, H2O2 dosage and adding method on the degradation efficiencies of model organic pollutants were investigated in detail and then the optimal operation parameters were determined. Furthermore, the stability and regeneration of the heterogeneous FeOOH/AC catalysts were also investigated under the optimum reaction conditions.