Persulfate enhanced electrochemical oxidation of phenol with CuFe2O4/ACF (activated carbon fibers) cathode

Electrochemically enhanced activation of Co3O4/TiO2 nanotube array anode for persulfate toward high catalytic activity, low energy consumption, and long lifespan performance

Advanced oxidation processes (AOPs) can directly degrade and mineralize organic pollutants (OPs) in water by generating reactive oxygen species with strong oxidizing ability. The development of advanced electrode materials with high catalytic performance, low energy consumption, no secondary pollution, and long lifespan has become a challenge that must be addressed in this field. A heterojunction catalyst loaded with Co3O4 on TDNAs (Co3O4/RTDNAs) was designed and constructed by a simple and efficient pyrolysis (Co3O4/TDNAs) and electrochemical reduction. Co3O4 can be uniformly distributed on the inner wall and surface of the TiO2 nanotubes, enhancing the specific surface area while forming a tight conductive interface with TiO2. This facilitates rapid transmission of electrons, thereby assisting Co3O4 in quickly activating PS to form reactive oxygen species. The Ti3+ and Ov generated in Co3O4/RTDNAs can significantly improve the electrocatalytic degradation of OPs. Also, the interface formed by Co3O4 and RTDNAs will effectively suppress Co2+ leakage, thereby reducing the risk of secondary pollution. When the reaction conditions were 1 mM PMS (PDS) and a current density of 5 mA/cm2 in the EA-PMS (PDS)/Co3O4/RTDNA system, 30 mg/L TC can achieve 83.24 % (81.89 %) removal in 120 min, with very low cobalt ion leaching, while the energy consumption was reduced significantly. Therefore, EA-PS/Co3O4/RTDNA system has strong stability and a high potential for treating the OPs in AOPs.

Electro-catalytic adsorption mechanism of acetonitrile in water using a ME-ACFs system

Acetonitrile wastewater is difficult to treat due to its high salinity and toxicity to microorganisms. In this paper, a micro electro-activated carbon fiber coupled system (ME-ACF) was established to treat simulated acetonitrile wastewater. In the 200 ml system, the concentration of acetonitrile adsorbed by ACF was 91.3 mg/L, while that of acetonitrile adsorbed by ME-ACF was 150.6 mg/L, and the removal efficiency was increased by 65 % in comparison. The activated carbon fibers before and after the reaction were subjected to a series of characterization, and it was found that the SABET decreased from 1393.48 m2/g to 1114.93 m2/g and 900.23 m2/g, respectively, but the oxygen on the surface of the activated carbon fibers was increased, and the effect of the micro electrolytic system on the activated carbon fibers was then analyzed. The possible reasons for the formation of acetic acid contained in the products were also discussed using DFT simulations. The removal mechanism of acetonitrile by ME-ACF was considered to be electrically enhanced adsorption and electro-catalytic hydrolysis.

Application of Electrochemical Oxidation for Water and Wastewater Treatment: An Overview

In recent years, the discharge of various emerging pollutants, chemicals, and dyes in water and wastewater has represented one of the prominent human problems. Since water pollution is directly related to human health, highly resistant and emerging compounds in aquatic environments will pose many potential risks to the health of all living beings. Therefore, water pollution is a very acute problem that has constantly increased in recent years with the expansion of various industries. Consequently, choosing efficient and innovative wastewater treatment methods to remove contaminants is crucial. Among advanced oxidation processes, electrochemical oxidation (EO) is the most common and effective method for removing persistent pollutants from municipal and industrial wastewater. However, despite the great progress in using EO to treat real wastewater, there are still many gaps. This is due to the lack of comprehensive information on the operating parameters which affect the process and its operating costs. In this paper, among various scientific articles, the impact of operational parameters on the EO performances, a comparison between different electrochemical reactor configurations, and a report on general mechanisms of electrochemical oxidation of organic pollutants have been reported. Moreover, an evaluation of cost analysis and energy consumption requirements have also been discussed. Finally, the combination process between EO and photocatalysis (PC), called photoelectrocatalysis (PEC), has been discussed and reviewed briefly. This article shows that there is a direct relationship between important operating parameters with the amount of costs and the final removal efficiency of emerging pollutants. Optimal operating conditions can be achieved by paying special attention to reactor design, which can lead to higher efficiency and more efficient treatment. The rapid development of EO for removing emerging pollutants from impacted water and its combination with other green methods can result in more efficient approaches to face the pressing water pollution challenge. PEC proved to be a promising pollutants degradation technology, in which renewable energy sources can be adopted as a primer to perform an environmentally friendly water treatment.

Enhanced H2O2 formation and norfloxacin removal by electro-Fenton process using a surface-reconstructed graphite felt cathode: New insight into synergistic mechanism of defective active sites

The efficient catalytic activity and strong durability possibility of carbon-based three-dimensional fiber materials remains an important challenge in Electro-Fenton advanced oxidation technology. Graphite felt (GF) is a promising electrode material for 2-electron oxygen reduction reaction but with higher catalytic inertia. Anodizing modification of GF has been proved to enhance it electro-catalytic property, but the disadvantages of excessive or insufficient oxidation of GF need further improved. Herein, the surface reconstituted graphite felt by anodizing and HNO₃ ultrasonic integrated treatment was used as cathode to degrade norfloxacin (NOR) and the substantial role of different modification processes was essentially investigated. Compared with the single modification process, the synergistic interaction between these two methods can generate more defective active sites (DASs) on GF surface and greatly improved 2-electron ORR activity. The H₂O₂ can be further co-activated by Fe²⁺ and DASs into •OH_{(ads and free)} and •O₂^- to efficiently degrade NOR. The treated GF with 20 min anodizing and 1 h HNO₃ ultrasound had the highest electrocatalytic activity in a wide electric potential (-0.4 V to -0.8 V) and pH range (3-9) in system and the efficient removal rate of NOR was basically maintained after 5 cycles. Under optimal reaction conditions, 50 mg L^-1 NOR achieved 93% degradation and almost 63% of NOR was completely mineralized within 120 min. The possible NOR degradation pathways and ecotoxicity of intermediates were analyzed by LC-MS and T.E.S.T. theoretical calculation. This paper provided the underlying insights into designing a high-efficiency carbon-based cathode materials for commercial antibiotic wastewater treatment.

Electrochemical-assisted ultraviolet light coupled peroxodisulfate system to degrade ciprofloxacin in water: Kinetics, mechanism and pathways

The persulfate advanced oxidation is an emerging and efficient pollutant treatment method, but usually requires the help of other materials or energy to catalyze and produce highly oxidizing active substances. In this paper, electrochemical-assisted ultraviolet light coupled peroxodisulfate system (E-UV-PDS) was used to degrade ciprofloxacin (CIP), and it was determined that electrolysis and ultraviolet photolysis were synergistic by calculation. The effects of initial pH, voltage, peroxodisulfate dosage, CIP concentration and coexisting anions on the degradation process were explored. The quenching experiments showed that ¹O₂, ⋅OH and SO₄^-⋅ were the main active oxygen species. Under the following conditions, ultraviolet light = 6 W, voltage = 4 V, [peroxodisulfate] = 20 mM, [pH]₀ = 7 and [CIP] = 100 mgL^-1, the degradation rate of CIP reached about 100% after 120 min, and the influence of inorganic anions was also discussed. Several intermediate products were identified by LC-MS, and three degradation pathways were speculated for CIP degradation. Finally, economic evaluation of the E-UV-PDS system was made, and it was useful to construct environmentally friendly and low-cost catalytic processes for the efficient degradation of organic pollutants.

Application of sulfate radicals-based advanced oxidation technology in degradation of trace organic contaminants (TrOCs): Recent advances and prospects

The large amount of trace organic contaminants (TrOCs) in wastewater has caused serious impacts on human health. In the past few years, Sulfate radical (SO₄^•-) based advanced oxidation processes (SR-AOPs) are widely recognized for their high removal rates of recalcitrant TrOCs from water. Peroxymonosulfate (PMS) and persulfate (PS) are stable and non-toxic strong oxidizing oxidants and can act as excellent SO₄^•- precursors. Compared with hydroxyl radicals(·OH)-based methods, SR-AOPs have a series of advantages, such as long half-life and wide pH range, the oxidation capacity of SO₄^•- approaches or even exceeds that of ·OH under suitable conditions. In this review, we present the progress of activating PS/PMS to remove TrOCs by different methods. These methods include activation by transition metal, ultrasound, UV, etc. Possible activation mechanisms and influencing factors such as pH during the activation are discussed. Finally, future activation studies of PS/PMS are summarized and prospected. This review summarizes previous experiences and presents the current status of SR-AOPs application for TrOCs removal. Misconceptions in research are avoided and a research basis for the removal of TrOCs is provided.