Electrochemical removal of levofloxacin using conductive graphene/polyurethane particle electrodes in a three-dimensional reactor

An overview of the recent advances and future prospects of three-dimensional particle electrode systems for treating wastewater

Three-dimensional (3D) electrochemical technology is considered a very effective industrial wastewater treatment method for its high treatment efficiency, high current efficiency, low energy consumption, and, especially, ability to completely mineralize nonbiodegradable organic contaminants. Particle electrodes, which are the fundamental components of 3D electrochemical technology, have multiple functions in the electrochemical reaction process. Various types of particle electrodes have been created and applied for wastewater treatment. Herein, we present a thorough analysis of the research and development of particle electrodes used for electrocatalyzing pollutants. Initially, reactor designs, factors affecting the removal efficiency of pollutants and degradation mechanisms are introduced. In particular, a detailed investigation is conducted into the selection of particle electrode materials and the roles they play in the 3D electrochemical treatment of wastewater. Subsequently, the degradation efficiency and energy consumption associated with 3D electrochemical technology for different pollutants are investigated. Finally, the directions and outlook for further studies on particle electrodes are discussed. We believe that this review will offer a useful perspective on the development and application of particle electrodes for wastewater purification.

A new attempt to remove toluene using nickel-iron bimetallic particle electrode reactor

A new attempt of removing toluene waste gas using a three-dimensional electrode reaction device with nickel-iron bimetallic particle electrode is presented in this paper. The particle electrode was prepared by a simple liquid phase reduction method. Through bimetal modification, the particle electrode mass transfer rate is increased to 1.29 times, and the degradation efficiency of the reactor is increased by nearly 40%, which makes it possible to remove toluene waste gas by other electrochemical methods in addition to plasma method. The removal efficiency of the particle electrode can be stabilized at more than 80% after 5 cycles (50 h). At the same time, the relationship between independent working parameters and dependent variables is analyzed using the central composite design, and the operating parameters are optimized. Based on this study, the removal mechanism and possible degradation pathway of toluene were investigated. This study provides a supplement to the possibility and theoretical basis of new technology application for electrocatalytic oxidation removal of VOCs.

Electrochemical treatment of malachite green dye wastewater by pulse three-dimensional electrode method

Water pollution is becoming more and more serious nowadays, and water resources are in shortage. As an environmentally friendly wastewater treatment technology without secondary pollution, the three-dimensional electrode method has received more and more attention. However, the conventional direct current (DC) three-dimensional electrode method has the disadvantages of high energy consumption and low current efficiency. Based on this, this work investigated the treatment of malachite green (MG) dye wastewater by pulse three-dimensional electrode method. The influences of pulse duty cycle, pulse period, electrolysis voltage, initial pH, aeration rate and Na2SO4 concentration on MG degradation were investigated. The results showed that under the optimal operating conditions of pulse duty cycle of 0.4, pulse period of 15 s, electrolysis voltage of 15 V, initial pH of 5, aeration rate of 0.5 L/min, Na2SO4 concentration of 0.10 mol/L, the removal rates of MG and COD reached 96.2% and 80.5%, respectively, the current efficiency reached 93.4%, and the energy consumption was 24.2 kWh/kg COD after 150 min. Compared with DC power supply mode, the MG removal rate, COD removal rate and current efficiency were enhanced, and the energy consumption was reduced by 83.9%. Moreover, the generation capacity of ·OH was increased under pulse power supply mode. Finally, a possible degradation pathway of MG in pulse power supply mode was inferred using UV-vis and GC-MS analysis. This study indicates that the pulse three-dimensional electrode method is an efficient and low-energy-consumption wastewater treatment method with stable degradation performance for MG dye wastewater.

Recent progress of particle electrode materials in three-dimensional electrode reactor: synthesis strategy and electrocatalytic applications

With the complete promotion of a green, low-carbon, safe, and efficient economic system as well as energy system, the promotion of clean governance technology in the field of environmental governance becomes increasingly vital. Because of its low energy consumption, great efficiency, and lack of secondary pollutants, three-dimensional (3D) electrode technology is acknowledged as an environmentally beneficial and sustainable way to managing clean surroundings. The particle electrode is an essential feature of the 3D electrode reactor. This study provides an in-depth examination of the most current advancements in 3D electrode technology. The significance of 3D electrode technology is emphasized, with an emphasis on its use in a variety of sectors. Furthermore, the particle electrode synthesis approach and mechanism are summarized, providing vital insights into the actual implementation of this technology. Furthermore, by a metrological examination of the research literature in this sector, the paper expounds on the potential and obstacles in the development and popularization of future technology.

Degradation of Levofloxacin by a green zero-valent iron-loaded carbon composite activating peroxydisulfate system: Reactivity, products and mechanism

In this study, a green zero-valent iron-loaded carbon composite (ZVI-SCG) was synthesized using coffee grounds and FeCl3 solution through two-steps method, and the synthesized ZVI-SCG was used in the activation of peroxydisulfate (PDS) to degrade Levofloxacin (LEX). Results revealed that ZVI-SCG exhibited a great potential for LEX removal by adsorption and catalytic degradation in the ZVI-SCG/PDS system, and 99% of LEX was removed in the ZVI-SCG/PDS system within 60 min. ZVI-SCG/PDS system showed a high reactivity toward LEX degradation under realistic environmental conditions. Also, the ZVI-SCG/PDS system could effectively degrade several quinolone antibiotics including gatifloxacin, ciprofloxacin and LEX in single and simultaneous removal modes. A potential reaction mechanism of LEX degradation by ZVI-SCG/PDS system was proposed, SO4•-, HO•, O2•- and 1O2 involved in radical and non-radical pathways took part in catalytic degradation of LEX by ZVI-SCG/PDS system, but HO• might be the main reactive species for LEX degradation. The possible degradation pathway of LEX was also proposed based on the identified ten intermediate products, LEX degradation was successfully achieved through decarboxylation, opening ring and hydroxylation processes. The potential toxicity of LEX and its oxidation products decreased significantly after treatment. This study provides a promising strategy of water treatment for the antibiotics-containing wastewater.

Differentiating the reaction mechanism of three-dimensionally electrocatalytic system packed with different particle electrodes: Electro-oxidation versus electro-fenton

Recently, there are still some controversial mechanisms of the 3D electrocatalytic oxidation system, which would probably confound its industrial application. From the conventional viewpoint, the Ti₄O₇ material may be the desired particle electrodes in the 3D system since its high oxygen evolution potential favors the production of ^•OH via H₂O splitting reaction at the anode side of Ti₄O₇ particle electrodes. In fact, the incorporation of Ti₄O₇ particles showed phenol degradation of 88% and COD removal of 51% within 120 min, under the optimum conditions at energy consumption of 0.668 kWh g^-1 COD, the performance of which was much lower than those in many previous literatures. In contrast, the prepared carbon black-polytetrafluoroethylene composite (CB-PTFE) particles with abundant oxygen-containing functional groups could yield considerable amounts of H₂O₂ (200 mg L^-1) in the 3D reactor and achieved a complete degradation of phenol and COD removal of 80% in the presence of Fe²⁺, accompanying a low energy consumption of only 0.080 kWh g^-1 COD. It was estimated that only 20% of Ti₄O₇ particles near the anode attained the potential over 2.73 V/SCE at 30 mA cm^-2 based on the potential test and simulation, responsible for the low yield of ^•OH via the H₂O splitting on Ti₄O₇ (1.74 × 10^-14 M), and the main role of Ti₄O₇ particle electrodes in phenol degradation was through direct oxidation. For the CB-PTFE-based 3D system, current density of 10 mA cm^-2 was sufficient for all the CB-PTFE particles to attain cathodic potential of -0.67 V/SCE, conducive to the high yield of H₂O₂ and ^•OH (9.11 × 10^-14 M) in the presence of Fe²⁺, and the ^•OH-mediated indirect oxidation was mainly responsible for the phenol degradation. Generally, this study can provide a deep insight into the 3D electrocatalytic oxidation technology and help to develop the high-efficiency and cost-efficient 3D technologies for industrial application.

A review on three-dimensional electrochemical technology for the antibiotic wastewater treatment

The potential genotoxicity and non-biodegradability of antibiotics in the natural water bodies threaten the survival of various living things and cause serious environmental pollution and destruction. Three-dimensional (3D) electrochemical technology is considered a powerful means for antibiotic wastewater treatment as it can degrade non-biodegradable organic substances into non-toxic or harmless substances and even completely mineralize them under the action of electric current. Therefore, antibiotic wastewater treatment using 3D electrochemical technology has now become a hot research topic. Thus, in this review, a detailed and comprehensive investigation was conducted on the antibiotic wastewater treatment using 3D electrochemical technology, including the structure of the reactor, electrode materials, the influence of operating parameters, reaction mechanism, and combination with other technologies. Many studies have shown that the materials of electrode, especially particle electrode, have a great effect on the antibiotic wastewater treatment efficiency. The influence of operating parameters such as cell voltage, solution pH, and electrolyte concentration was very significant. Combination with other technologies such as membrane and biological technologies has effectively increased antibiotic removal and mineralization efficiency. In conclusion, the 3D electrochemical technology is considered as a promising technology for the antibiotic wastewater treatment. Finally, the possible research directions of the 3D electrochemical technology for antibiotic wastewater treatment were proposed.

Efficient and recyclable Ni-Ce-Mn-N modified ordered mesoporous carbon electrode during electrocatalytic ozonation process for the degradation of simulated high-salt phenol wastewater

In this study, an efficient and stable NiO/CeO₂/MnO₂-modified nitrogen-doped ordered mesoporous carbon (NOMC) particle electrode was developed, in which the metal oxides were mosaicked within the pore channels by one-pot skeleton hybridization, and the comodification of NiO/CeO₂/MnO₂/N was found to improve the electrocatalytic activity and stability of the particle electrode. The improved stability of the ordered mesoporous carbon towards pore collapse was applied to the degradation of simulated high-salt phenol wastewater by an electrocatalytic ozonation process using simple binder pelletization. The modified ordered mesoporous carbon shows a specific surface area of 269.7 m² g^-1 and a pore size of 3.17 nm, and SEM and TEM were used to show that the mesoporous structure is well maintained and the metal nanoparticles are well dispersed. The electrochemically active area of the Ni_2%/Ce_0.5%/Mn_2.5%-NOMC particle electrode reaches 224.65 mF cm^-2, which indicates that NiO improves the capacitance of the ordered mesoporous carbon and accelerates the electron transfer efficiency. Encouragingly, the phenol removal efficiency is found to reach up to 93.0% for 60 min over a wide range of pH values, with an initial phenol concentration of 150 mg L^-1, low current (0.03 A) and fast reaction rate (0.0895 min^-1), and the presence of CeO₂ ameliorates the low activity of the particle electrode under acidic conditions. These results indicate that the presence of pyridine-N and β-MnO₂ effectively mitigates carbon corrosion and improves electrode stability, as the accumulation of large amounts of ·OH at 20 min and the maintenance of a degradation efficiency of more than 90% after eight cycles provides a viable solution for the widespread practical application of ordered mesoporous carbon particle electrodes.

A review on the landfill leachate treatment technologies and application prospects of three-dimensional electrode technology

With the expansion of urbanisation, the total amount of solid waste produced by urban residents has been increasing, and the problem of municipal solid waste disposal has also been aggravated. Landfill leachate treatment technologies could be divided into three categories: biological, physical and advanced oxidation treatment technology. Among them, advanced oxidation treatment technology has a good effect on the treatment of landfill leachate with little secondary pollution and has excellent application potential. Three-dimensional (3D) electrode technology, as a new type of advanced oxidation technology, could remove refractory pollutants in water and has attracted considerable attention. This article aims to (1) compare existing landfill leachate treatment technologies, (2) summarise 3D electrode technology application scenarios, (3) discuss the advantages of 3D electrode technology in landfill leachate treatment and (4) look ahead the future directions of 3D electrode technology in landfill leachate treatment. We hope that this article will be helpful to researchers who are interested in the field of landfill leachate treatment.

Fabrication of novel three-dimensional Fe3O4-based particles electrodes with enhanced electrocatalytic activity for Berberine removal

Reasonable design of three-dimensional (3D) catalytic particle electrodes (CPEs) is crucial for achieving efficient electrocatalytic oxidation of organic pollutants. Herein, the novel Fe₃O₄/SnO₂/GO (FO/SO/GO) particle electrode has been developed and serviced to the 3D electrocatalytic berberine hydrochloride oxidation system with DSA (RuO₂-IrO₂-SnO₂/Ti) electrode as anode and GDE (gas diffusion electrode) electrode as the cathode. Compared with 2D systems and other CPEs, FO/SO/GO electrode shows excellent electrocatalytic activity and remarkable stability for BH removal, that is, the removal rate of BH is 94.8% within 90 min, and the rate constant is 0.03095 min^-1. More importantly, after five cycles, the ternary composite still maintains a strong ability to oxidize pollutants. The structural characterization and electrochemical measurement further uncover that the electron transfer ability and electrocatalytic oxidation efficiency are highly dependent on the surface structure regulation of CPEs. Furthermore, the quenching experiments show that hydroxyl radicals are the main active species in the 3D electro-Fenton (EF) system, which can oxidize BH molecules adsorbed on the surface of GO to CO₂, H₂O, or other products. The results could potentially provide new insights for designing and fabricating more stable and efficient 3D CPEs electrocatalytic removal of organic pollutants in the future.

Application of a fluidized three-dimensional electrochemical reactor with Ti/SnO2-Sb/β-PbO2 anode and granular activated carbon particles for degradation and mineralization of 2,4-dichlorophenol: Process optimization and degradation pathway

A three-dimensional electrochemical reactor with Ti/SnO₂-Sb/β-PbO₂ anode and granular activated carbon (3DER-GAC) particle electrodes were used for degradation of 2,4-dichlorophenol (2,4-DCP). Process modeling and optimization were performed using an orthogonal central composite design (OCCD) and genetic algorithm (GA), respectively. Ti/SnO₂-Sb/β-PbO₂ anode was prepared by electrochemical deposition method and then its properties were studied by FESEM, EDX, XRD, Linear sweep voltammetry and accelerated lifetime test techniques. The results showed that lead oxide was precipitated as highly compact pyramidal clusters in the form of β-PbO₂ on the electrode surface. In addition, the prepared anode had high stability (170 h) and oxygen evolution potential (2.32 V). A robust quadratic model (p-value < 0.0001 and R² > 0.99) was developed to predict the 2,4-DCP removal efficiency in the 3DER-GAC system. Under optimal conditions (pH = 4.98, Na₂SO₄ concentration = 0.07 M, current density = 35 mA cm^-2, GAC amount = 25 g and reaction time = 50 min), the removal efficiency of 2,4-DCP in the 3DER-GAC system and the separate electrochemical degradation process (without GAC particle electrode) were 99.8 and 71%, respectively. At a reaction time of 80 min, the TOC removal efficiencies in the 3DER-GAC and the separate electrochemical degradation system were 100 and 57.5%, respectively. Accordingly, the energy consumed in these two systems was calculated to be 0.81 and 1.57 kWh g^-1 TOC, respectively. Based on the results of LC-MS analysis, possible degradation pathways of 2,4-DCP were proposed. Trimerization and ring opening reactions were the two dominant mechanisms in 2,4-DCP degradation.

Progress in research and development of particle electrodes for three-dimensional electrochemical treatment of wastewater: a review

A three-dimensional (3D) electrochemical technology is regarded as a very effective industrial wastewater treatment method as it has high treatment efficiency, high current efficiency, and low energy consumption, and especially can completely mineralize nonbiodegradable organic pollutants. The core of the 3D electrochemical technology is a particle electrode, and the particle electrode plays several important roles for removing pollutants during the electrochemical reaction process. Many types of particle electrodes have been developed and used for different types of wastewater treatment. In this paper, a comprehensive review on the research and development of particle electrodes of the 3D electrochemical reactors for wastewater treatment is conducted. Specifically, the role that the particle electrode plays during the 3D electrochemical treatment of wastewater is thoroughly investigated and systematized. In addition, the different types of particle electrodes used in the 3D electrochemical wastewater treatment are classified into several types according to the presence or absence of a catalyst and the main components of the particle electrode or carrier. Also, focusing on the recent research results, the structural characteristics, performance, advantages and defects, and the role of catalyst components of each particle electrodes are evaluated. Finally, the direction and prospect of future research on the particle electrode is presented.