Electrode Reactor Research Articles

Quantifying Transport and Reaction Electrocatalytic Processes in a Gastight Rotating Cylinder Electrode Reactor Via Integration of Computational Fluid Dynamics Modeling and Experiments

Quantifying Transport and Reaction Electrocatalytic Processes in a Gastight Rotating Cylinder Electrode Reactor Via Integration of Computational Fluid Dynamics Modeling and Experiments

Efficient degradation of naproxen in a three dimensional biofilm electrode magnetism reactor (3DBEMR): Removal performance and microbial community

A three-dimensional biofilm electrode magnetism reactor (3DBEMR) was constructed to removal naproxen (NPX). This study evaluated 3DBEMR performance in removal of refractory NPX, while also discussing the effect of the electro-magnetic superposition on microbial community by high throughput sequencing. Results indicated that 3DBEMR’s average removal rate for NPX stood at 88.36%, representing an increase by 75.24%, 65.03% and 12.36%, respectively, compared to 3DBR (Three-Dimensional Biofilm Reactor), 3DBMR (Three-Dimensional Biofilm Magnetism Reactor) and 3DBER (Three-Dimensional Biofilm Electrode Reactor). This was attributed to the influence of electro-magnetic adsorption, electro-oxidaton/catalysis, and electro-magnetic biodegradation. Another major contributing factor to NPX removal was the presence in 3DBEMR of high-abundance genera such as Rhodobacter, Porphyrobacter, Methyloversatilis, Sphingopyxis,Bosea, Singulisphaera, Sphingomonas. Therefore, the 3DBEMR was successfully demonstrated to be a flexible and effective technique in NPX degradation, which would help to better understand the effect of superposition of electric and magnetic fields on microbial community.

Cathodic generation of hydrogen peroxide sustained by electrolytic O2 in a rotating cylinder electrode (RCE) reactor

This investigation reports the electrosynthesis of H2O2 from the two-electron reduction of dissolved O2, provided by anodic water oxidation, in a rotating cylinder electrode (RCE) reactor. O2 evolved at six surrounding Ti|IrO2 anode plates, whereas the oxygen reduction reaction (ORR) occurred at a (C-PTFE)-coated carbon cloth covering a rotating steel cathode. The mass transport characterization of the cathodic ORR to yield H2O2 was carried out through limiting current measurements (-0.65 ≤ E ≤ -0.3 V vs. SHE). Peripheral velocities (U) between 11.9 and 79.6 cm s−1 (i.e., Reynolds (Re) numbers of 4537 ≤ Re ≤ 30243) were employed to ensure turbulent flow conditions. An apparent plateau was obtained in the studied potential range, in agreement with mass transport-controlled ORR. From the limiting current values obtained, the mass transport correlation kma=bUc, which describe the transport considering the geometrical aspects of the cell and the hydrodynamic regime, were obtained. Additionally, bulk electrolyses were executed to accumulate H2O2, with no O2 feeding from any air pump. These trials were performed under mass transport control at a cathode potential of -0.46 V vs. SHE. Both, mass transport studies and bulk H2O2 electrogeneration, were performed in the presence and absence of atmospheric air on top of the RCE reactor to evaluate the potential contribution of additional O2 dissolution promoted by the electrolyte velocity and pressure gradients imposed by the RCE. Its contribution to H2O2 production depended on U. The best conditions for the self-sustained electrolytic H2O2 synthesis were U = 79.6 cm s−1 and cathode potential of -0.46 V, achieving 177.2 mg L−1 H2O2 with current efficiency and energy consumption of 23.3% and 0.013 kW h (g H2O2)−1 after 180 min. The potential application of this RCE reactor to the degradation of organic pollutants is thus envisaged.

The influence of cathode material, current density and pH on the rapid Cr(III) removal from concentrated tanning effluents via electro-precipitation

The Cr(III) removal (3585 mg L−1) from real tanning discharges is herein conducted using an electro-precipitation process in a rotating cylinder electrode (RCE) reactor. A 1018-type carbon steel anode and two different cathodes (TiO2/RuO2 or 316L stainless steel, 316L SS) are tested within this process, using three current densities (10, 20 and 30 mA cm−2), and two initial pH values for the real solution. A synthetic solution is initially evaluated to analyze more ideal conditions in the reactor. The Cr(III) electroprecipitation is not favorable in the original pH of the real tannery wastewater (∼3.55) unlike the synthetic solution (pH 2.8), presumably since the Fe-Cr interaction is hindered by impurities in the solution, whereby the pH of the real discharge needs to be modified to pH 5 or 6. Residence times of 4800 (80 min) and 3600 s (60 min) using 30 mA cm−2 are enough to remove all the Cr concentration at pH 5 and 6, respectively. Energy consumptions of 10 and 7.5 kWh m−3 are calculated for these treatments, respectively. The precipitates are mainly comprised of Cr2FeO4(s) (Chromite) regardless of the experimental condition used in the removal process, followed by minor traces of Cr(OH)3(s) and CrO(OH)(s). A reaction mechanism is proposed for the Cr(III) electro-precipitation relying on the thermodynamic diagrams, and characterizations of the precipitates.

Volcanic rock: A new type of particle electrode with excellent performance, which can efficiently degrade norfloxacin

In this work, volcanic rocks were used as particle electrodes to construct a volcanic rock three-dimensional (3D) electrode reactor. In a wide pH range (3 ~ 11), volcanic rocks can degrade norfloxacin (NOR) at low voltage (4 V) within 40 min. In acidic environment, the NOR removal was greater than 85%. Volcanic rock also showed excellent electrocatalytic activity when treating ofloxacin, methylene blue and other pollutants. After six cycles, the weight loss rate of volcanic rocks was 3.87%. Volcanic rocks had high mechanical strength stability. There were hydroxyl radicals (OH) and superoxide radical (O2−) produced in the volcanic rock 3D system. The volcanic rock surface was the main location of NOR degradation. The possible degradation mechanism and the degradation pathway of NOR were proposed. In addition, volcanic rock also showed excellent effects in actual surface water treatment.

Is Hydroxide Just Hydroxide? Unidentical CO2 Hydration Conditions during Hydrogen Evolution and Carbon Dioxide Reduction in Zero-Gap Gas Diffusion Electrode Reactors

The implementation of gas diffusion electrodes is a prerequisite to achieving industrially relevant reaction rates in gas-phase electrochemical CO2 reduction (CO2RR). In the state-of-the-art anion exchange membrane flow electrolyzers, however, there is a substantial loss of reactants due to a nonelectrochemical CO2 consumption at the cathode and the transport of its products to the anode. Our detailed analysis of CO2 crossover in a zero-gap CO2-to-CO flow electrolyzer showed a change in the chemical nature of the transported ionic species through the membrane. With the increasing reaction rate, a continuous shift from HCO3– to CO32– conduction was found to be similar to pure carbonate conduction in the high current density region (>100 mA cm–2). As competing hydrogen evolution takes over the cathodic reaction in a CO2-rich environment, hydroxide conduction becomes more pronounced. This reveals an alteration in the chemical CO2 consumption, the so-called CO2 hydration (CO2 + OH– ↔ HCO3– + OH– ↔ CO32–), implying an unidentical environment for the hydroxide ions generated in CO2RR and hydrogen evolution reaction under a CO2 atmosphere. Our work draws attention to the incomplete description of CO2 hydration at the confined cathode/membrane interface in membrane electrode assembly-type zero-gap CO2 electrolyzers.

An integrated biological-electrocatalytic process for highly-efficient treatment of coking wastewater

Coking wastewater is typically refractory, mainly due to its biological toxicity and complex composition. In this study, a novel integrated biological-electrocatalytic process consisting of two three-dimensional electrochemical reactors (3DERs), two biological aerated filters (BAFs), and a three-dimensional biofilm electrode reactor (3DBER) is developed for the advanced treatment of coking wastewater. 73.21% of chemical oxygen demand (COD), 38.02% of ammonium nitrogen (NH4+-N) and 91.46% of nitrate nitrogen (NO3–-N) are removed by 3DERs. BAFs mainly convert NH4+-N to NO3–-N through microbial nitrification. The 3DBER removes the residual NO3–-N by bio-electrochemical denitrification. The integrated system can eliminate 74.72–83.27% of COD, 99.38–99.74% of NH4+-N, and 69.64–99.83% of total nitrogen from coking wastewater during the continuous operation, as well as significantly reducing the toxicity of the wastewater. The superiorities of the integrated 3DERs/BAFs/3DBER system recommend the application of such biological-electrocatalytic technology in the treatment of highly toxic wastewater.

Enhanced self-powered system with graphene oxide modified electrode for simultaneous remediation of nitrate-contaminated groundwater and river sediment

Simultaneous in situ remediation of malodorous organic sediment and nitrate-contaminated groundwater was achieved with a novel, enhanced, self-driven three-chamber bio-electrochemical system with Graphene Oxide (GO) modified electrodes. It has been successfully improving the electron transfer efficiency and self-purification ability by the special configuration combining surface water, sediment with underground water. The upper part can be regarded as a Sediment Microbial Fuel Cell (SMFC). The organic sediment serves as available carbon source to provide electrons for the microbes coated on the anode instead of potential pollutants. The lower part is the Biofilm Electrode Reactor (BER). Electrons were synchronously obtained from the loaded biofilm to reduce nitrate. The electricity generated from the upper part was applied directly to the lower part as electrical stimulation to enhance bacterial denitrification of the system. The electron conduction efficiency was further improved by graphene oxide modifying. With a maximum power density of 14.21 W/m2, as well as the voltage outputs ranging from 700 mV to 900 mV, nitrate removal was accelerated with less accumulation of intermediates compared with the controls without graphene oxide. The maximum output power was increased by 1.5 times and the nitrate removal efficiency (in 10 h) was increased from 89.13 ± 1.4% to 99.9 ± 0.1% after the modification. The organic matter in the sediment decreased by 78% after 270 days simultaneously. Sequencing of the microbial community showed that Geobacter and Anaerolinina were enriched in the anode. And theα-proteobacteria were enriched in the four experimental groups and had a good effect on nitrate removal especially in the C-GO-SSG system (Carbon felt anode-Graphene Oxide Modified cathode equipped Surface-water Sediment and Groundwater System) after 270 days operation. These results demonstrate that the C-GO-SSG system can be further used to remediation of sediment and groundwater with improved efficiency.

Particle electrode materials dependent tetrabromobisphenol A degradation in three-dimensional biofilm electrode reactors

The completely biological degradation of Tetrabromobisphenol A (TBBPA) contaminant is challenging. Bio-electrochemical systems are efficient to promote electrons transfer between microbes and pollutants to improve the degradation of refractory contaminants. In particular, three-dimensional biofilm electrode reactors (3DBERs), integrating the biofilm with particle electrodes, represent a novel bio-electrochemical technology with superior treatment performances. In this study, the electroactive biofilm is cultured and acclimated on two types of particle electrodes, granular activated carbon (GAC) and granular zeolite (GZ), to degrade the target pollutant TBBPA in 3DBERs. Compared to GZ, GAC materials are more favorable for biofilm formation in terms of high specific surface area and good conductivity. The genus of Thauera is efficiently enriched on both GAC and GZ particles, whose growth is promoted by the electricity. By applying 5 V voltage, TBBPA can be removed by over 95% in 120 min whether packing GAC or GZ particle electrodes in 3DBERs. The synergy of electricity and biofilm in TBBPA degradation was more significant in GAC packed 3DBER, because the improved microbial activity by electrical stimulation accelerates debromination rate and hence the decomposition of TBBPA. Applying electricity also promotes TBBPA degradation in GZ packed 3DBER mainly due to the enhanced electrochemical effects. Roles of particle electrode materials in TBBPA removal are distinguished in this work, bringing new insights into refractory wastewater treatment by 3DBERs.

Performance and mechanism of a novel woodchip embedded biofilm electrochemical reactor (WBER) for nitrate-contaminated wastewater treatment

In this study, a woodchip biofilm electrode reactor (WBER) with woodchips embedded anode and cathode was developed, and its denitrification mechanism was analyzed by investigating the denitrification performance, organic matter change, redox environment and microbial community. The results show that the WBER with a carbon rod as anode (C-WBER) had a higher denitrification efficiency (2.58 mg NO- 3-N/(L·h)) and lower energy consumption (0.012 kWh/g NO- 3-N) at 350 mA/m2. By reducing the hydroxyl radical and dissolved oxygen concentrations, anode embedding technology effectively decreased the inhibition on microorganisms. Lignin decomposition, nitrification and aerobic denitrification were carried out in anode. Additionally, hydrogen autotrophic denitrification and heterotrophic denitrification were occurred in cathode. The WBER effectively removed nitrate and reduced the cost, providing a theoretical basis and direction for further develop BERs.

Degradation of azo dye wastewater by the combination process of 3D BER and CW-MFC

The treatment of azo dye wastewater has become a hot issue in the area of water pollution control. In this paper, a novel combined process of constructed wetland-microbial fuel cell (CW-MFC) and three dimensional biofilm electrode reactor (3D BER) was carried out for treatment of reactive brilliant red X-3B dye wastewater. Decolorization rate, COD removal and electricity generation in the combination process were studied, and the main factors affecting the system’s performance were also investigated. The results showed that the decolorization rate of combination process (3D BER-CW-MFC) was over 96%, and closed-circuit CW-MFC had better decolorization effect than open-circuit CW-MFC. COD removal rate of the combination process was far higher than the 3D BER and CW-MFC operated alone (78.9%∼90.8% and 50.6%∼66.2%, respectively). With the increase of influent dye concentration in the 3D BER, Cell voltages of the CW-MFCs all increased firstly and then decreased. The cell voltage reached the maximum at influent dye concentration of 600 mg L-1, and then decreased by 6.42%∼14.34% after the dye concentration increased to 1000 mg L-1. In addition, cell voltage could be enhanced by increasing the cathode area of CW-MFCs, due to improved cathode potential and reduced total internal resistance of the system.

Study on degradation of reactive brilliant red X-3B by three-dimensional biofilm electrode reactor

The treatment of azo dyes by three-dimensional biofilm electrode reactor (3D-BER) has the characteristics of fast decolorization, high mineralization efficiency and less sludge production and has broad application prospects. The 3D-BER was constructed by filling granular activated carbon (GAC) as a third bipolar electrode in the cathode chamber of conventional BER, and it greatly improved the degradation property of reactive brilliant red (RBR) X-3B. The effects of dye concentration, operating voltage, hydraulic retention time (HRT) and nitrate content on the stability of the experiment were investigated. The results reveal that azo dyes were first decomposed into aromatic amines such as aniline at the cathode, however, the amine substance was difficult to be biodegraded in the anaerobic cathode area, and then the decomposition products of aromatic amines reached the anode region and were further metabolized. Moreover, the water samples were analysed by FTIR and UV-Vis analysis. It was noted that the double bond of the azo dye was broken and degraded into aromatic amines, which were further effectively degraded.

Highly Efficient Removal of Nitrate from Agricultural Runoff in a Biochar Electrode-Based Biofilm Electrode Reactor

Highly Efficient Removal of Nitrate from Agricultural Runoff in a Biochar Electrode-Based Biofilm Electrode Reactor

Efficient Use of Electrons in a Double-Anode Microbial Fuel Cell–Biofilm Electrode Reactor Self-Powered Coupled System for Degradation of Azo Dyes

Efficient Use of Electrons in a Double-Anode Microbial Fuel Cell–Biofilm Electrode Reactor Self-Powered Coupled System for Degradation of Azo Dyes

고농도 유기성 산업폐수 처리를 위한 복극층 전극반응기의 적정처리조건 탐색

고농도 유기성 산업폐수 처리를 위한 복극층 전극반응기의 적정처리조건 탐색

Electrocoagulation treatment of industrial tannery wastewater employing a modified rotating cylinder electrode reactor

The removal of highly concentrated pollutants, presented in a wastewater mixture from industrial tannery effluents by electrocoagulation, was examined. All experiments were carried out in a rotating cylinder electrode reactor with six aluminum anodes and two sedimentation tanks. The influence of the applied current density and rotational speed on the removal efficiency of an electrocoagulation reactor was studied. Chemical oxygen demand was diminished at 70%, while total suspended solids, chromium (III) and turbidity were almost eliminated (>90%) with 6 mA cm−2 of the applied current density. Additionally, a homogeneous cathodic deposit was obtained at the end of each test. Those cathodic deposits and flocs were analyzed by SEM-EDS. Calculations of the cell energy consumption and the produced aluminum cost were estimated for 6 mA cm−2 and 100 rpm, obtaining 1.98 kWh m−3 and $0.7 USD m−3, respectively.

Simultaneous removal of nitrate and sulfate using an up-flow three-dimensional biofilm electrode reactor: Performance and microbial response

Nitrate removal from low carbon water is a problem in the water treatment, especially in the presence of high sulfate. In this work, an up-flow three-dimensional biofilm electrode reactor (3D-BER) was established to remove nitrate and sulfate from low organic carbon water. Results indicated that sulfate negatively affected nitrate removal. Moreover, high electric current and short hydraulic retention time deteriorated the performance of nitrate and sulfate removal. When the influent of SO42− was 150 mg/L, the removal efficiency of NO3−-N and SO42− was 88.49 ± 4.5% and 29.35 ± 5.5%, respectively. The high-throughput sequencing revealed that denitrifying bacteria dominated in the lower part of the reactor while sulfate reducing bacteria dominated in the upper part of the reactor. It was speculated that oxidation products of sulfide could serve as supplementary electron donors to enhance nitrate removal in the 3D-BER.

Cleaner production on electrochemical removal of sulphonamide from wastewater using three-dimensional electrode system: characterisation and kinetics

ABSTRACT In the examination of increasing interest in emerging pollutants, advanced technologies for emerging pollutants have been focused in the environmental science field. This study focuses on the sulphonamide removal from aqueous phase using designed three-phase three-dimensional electrode reactor. The parameters such as pH, particle electrode concentration, initial concentration of sulphonamide and the applied voltage have been studied using batch experiments. Sulphonamide was removed in 60 min at 12 V, pH 3 and 15 g of particle electrode in an electrochemical cell. From fact-finding, it was concluded that the efficiency of the electrochemical reactor increases with a decrease in pollutant concentration with optimum voltage (12 V). SEM-EDS and FTIR have been used for the characterisation of Sulphuric acid-activated Strychnos potatorum particle electrodes (SASP). The removal of sulphonamide using this reactor followed the pseudo-second-order (R2 > 0.96) and Langmuir–Hinshelwood kinetics (R2 = 0.9504). This newly designed three-dimensional reactor is an effective system for the complete removal of toxic pollutants from wastewater and this can be an alternative to the existing system.

Electrochemical degradation of ibuprofen using an activated-carbon-based continuous-flow three-dimensional electrode reactor (3DER)

We developed a continuous-flow three-dimensional electrode reactor (3DER) to remove ibuprofen (IBP) from water. The effects of the operating parameters on the 3DER performance were investigated. The 3DER was constructed by filling a conventional two-dimensional electrode reactor with granular activated carbon, which acted as particle electrodes. The IBP removal efficiency of the 3DER was 98% in 4 h, which was 2.5 times higher than the removal efficiency for the two-dimensional electrode reactor. IBP removal kinetics tests indicated that the current density (1–20 mA/cm2) correlated better than the other operating parameters with the first-order rate constant (k). The flow rate affected the IBP removal kinetics to a small degree. Chloride and sulfate supporting electrolyte concentrations between 17 and 100 mM affected the IBP removal kinetics in opposite ways. Increasing the chloride concentration increased k, but increasing the sulfate concentration decreased k. Radical quenching experiments indicated that much more IBP degradation occurred through both indirect and direct oxidation mechanisms in the 3DER than in the two-dimensional electrode reactor. The particle electrodes caused hydroxyl radicals to form when the 3DER treatment was started, but the particle electrodes later acted as third electrodes and favored direct oxidation of IBP.

Ultrasound-assisted enhanced electroxidation for mineralization of persistent organic pollutants: A review of electrodes, reactor configurations and kinetics

Discharge of toxic and hazardous pollutants in the aquatic bodies is dangerous for the human being and aquatic life. Nowadays, novel methods need to be developed to increase the treatment efficiency of such types of pollutants. Among the electrochemical technologies, electroxidation coupled with power ultrasound, so-called sonoelectroxidation, has gained attention because of its ability to remove a wide range of ubiquitous pollutants. The use of power ultrasound, in combination with electroxidation, provides the synergistic effect by virtue of chemical and physical effect of ultrasound for degradation of compounds. This review presents a critical analysis of studies (1996–2020) on the treatment of various synthetic and real wastewater using the sonoelectroxidation process. An overview of current advancement in electrode material and reactor geometry has been deliberated. Coupling these two techniques increased the mineralization degree in a remarkable way. This review critically evaluates various types (batch and continuous) of sonoelectro reactors used in the sonoelectrochemical process. Kinetics of the degradation process has been reviewed in detail. Challenges associated with these technologies and sluggish development in reactor geometries have been identified with the foremost application in wastewater treatment.