Analysis of factors influencing on Electro-Fenton and research on combination technology (II): a review

The principle of Fenton reagent is to produce ·OH by mixing H2O2 and Fe2+ to realize the oxidation of organic pollutants, although Fenton reagent has the advantages of non-toxicity and short reaction time, but there are its related defects. The Fenton-like technology has been widely studied because of its various forms and better results than the traditional Fenton technology in terms of pollutant degradation efficiency. This paper reviews the electro-Fenton technology among the Fenton-like technologies and provides an overview of the homogeneous electro-Fenton. It also focuses on summarizing the effects of factors such as H2O2, reactant concentration, reactor volume and electrode quality, reaction time and voltage (potential) on the efficiency of electro-Fenton process. It is shown that appropriate enhancement of H2O2 concentration, voltage (potential) and reaction volume can help to improve the process efficiency; the process efficiency also can be improved by increasing the reaction time and electrode quality. Feeding modes of H2O2 have different effects on process efficiency. Finally, a considerable number of experimental studies have shown that the combination of electro-Fenton with ultrasound, anodic oxidation and electrocoagulation technologies is superior to the single electro-Fenton process in terms of pollutant degradation.

Flow-Through Electrochemical Membrane Reactor with a Self-Supported Carbon Membrane Electrode for Highly Efficient Synthesis of Hydrogen Peroxide

In situ electroreduction of O2 to H2O2 by using electrons as reagents is known as a green process, which is highly desirable for environmental remediation and chemical industries. However, the development of a cost-effective electrode with superior H2O2 synthesis rate and stability is challenging. A self-supported carbon membrane (CM) was prepared in this study from activated carbon and phenolic resin by carbonization under a H2 atmosphere. It was employed as the cathode to build a flow-through electrochemical membrane reactor (FT-ECMR) for electrosynthesis of H2O2. The results showed that the CM had a small pore size (34 nm), a high porosity (42.3%), and a high surface area (450.7 m2 g-1). In contrast to most of the state-of-the-art self-supported carbon electrode reported in the previous works, the FT-ECMR exhibited a high concentration of continuous and stable H2O2 electrosynthesis (1042 mg L-1) as well as a H2O2 synthesis rate of 5.21 mg h-1 cm-2. It had also demonstrated a high oxygen conversion (0.37%) and current efficiency (88%). The outstanding performance of the FT-ECMR for H2O2 synthesis was attributed to the enhanced mass transfer of the reactor, the existence of a relatively high surface area of CM, and the abundant disordered carbon structures (sp3-C, defects, and edges). In conclusion, our work highlighted using the FT-ECMR with the CM to synthesize H2O2 efficiently and cost-effectively.

A microbial electro-fenton cell for removing carbamazepine in wastewater with electricity output

High electrical energy is required for the electro-Fenton process to remove pharmaceuticals and personal care products (PPCPs) in wastewater. The aim of this study was to develop a novel and more cost-effective process, specifically a microbial electro-Fenton cell (MeFC), for treating PPCPs in wastewater. Acetylene black was selected as the catalyst for H₂O₂ electrogeneration and Fe-Mn binary oxide for hydroxyl radical production. In addition to lowering energy needs, the MeFC produced a maximum power density of 112 ± 11 mW/m² with 1 g/L acetate as a representative substrate and 10 mg/L carbamazepine (CBZ) as a typical PPCP. Comparing with electro-Fenton process, the CBZ removal in the MeFC was 38% higher within 24 h operation (90% vs. 62%). Furthermore, the CBZ removal rate in the MeFC was 10-100 times faster than that in other biological treatment processes. Such enhanced degradation of CBZ in the MeFC was attributed to the synergistic reactions between radical oxidation of CBZ and biodegradation of degradative intermediates. The MeFC provides a promising method to remove PPCPs from wastewater coupling with efficient removal of other biodegradable organics.