Carbon Particle Electrode Research Articles

Nitrogen-doped iron-manganese porous carbon particle electrodes for electrocatalytic degradation of tetracycline: Interfacial reaction mechanisms

In this study, nitrogen-doped porous carbon-supported iron-manganese microspheres (FeMn@NC-700) were successfully synthesized and employed as three-dimensional particle electrodes (3DPE) for electro-oxidative of tetracycline (TCH) in water. FeMn@NC-700 exhibited stable catalytic activity and effective TCH removal capabilities under complex water quality conditions and varying pH levels. Under optimized conditions, the 3D/FeMn@NC-700 system reduced the TCH concentration from an initial 20 mg/L to 0.96 mg/L within 60 min, achieving a 95.23 %removal efficiency with an energy consumption of only 10.05 kWh/m3. The outstanding electrocatalytic activity of the 3D/FeMn@NC-700 system was attributed to the dynamic redox cycling between the Fe and Mn species on the 3DPE surface. Radical quenching experiments and electron paramagnetic resonance (EPR) analysis identified the predominant role of singlet oxygen (1O2), effectively removing TCH with the assistance of hydroxyl radicals (·OH) and superoxide anions (O2·-). The degradation pathways of major intermediate products of TCH were proposed, along with a toxicity assessment. In conclusion, the 3D/FeMn@NC-700 system represents a reliable and cost-effective technology for TCH wastewater treatment.

Degradation of 2,4-dinitrotoluene from aqueous solutions by three-dimensional electro-Fenton with magnetic activated carbon particle electrodes (GAC/Fe3O4)

Abstract 2,4-Dinitrotoluene (2,4-DNT) is a broadly applied nitroaromatic compound with multiple applications, and its simple production has resulted in its extensive utilization in producing explosives, dyes, and rubber. This substance is hazardous and induces genetic mutations in humans, fish, and microorganisms. Thus, this research was done to assess the effectiveness of the three-dimensional electro-Fenton (3D/EF) process employing magnetic activated carbon particle electrodes (GAC/Fe3O4) in eliminating 2,4-dinitrotoluene from water-based solutions. In this experimental investigation, Fe3O4 nanoparticles were created using the chemical co-precipitation technique. The G/β-PbO2 anode was fabricated by electrochemically depositing PbO2 layers on graphite sheets. G/β-PbO2 and stainless steel were utilized as the anode and cathode, respectively. The structure, particle size, and properties of the GAC/Fe3O4 nanocomposite were analyzed using FESEM, XRD, and EDX. The morphology of the G/β-PbO2 electrode was also examined using SEM. The Taguchi experimental design method was employed to identify the optimal conditions. The outcomes demonstrated that higher reaction time and current density, as well as lower pH and pollutant concentration, resulted in improved 3D/EF efficiency. Accordingly, the optimum values of parmeters were identified to be a concentration of 2,4-DNT = 50 mg/L, pH = 3, electrolysis time = 100 min, and current density = 8 mA/cm2. With these parameters, the degradation efficiency of 2,4-DNT through the examined system was 98.42 %, alongside removal efficiencies of 84.69 % for COD and 79.67 % for TOC. Additionally, the results indicated an increase in the average oxidation state (AOS) (from 1.27 to 1.95) and carbon oxidation state (COS) (from 1.27 to 2.75) in the 3D/EF process, along with a decrease in the COD/TOC ratio (from 1.81 to 1.36), indicating the effectiveness of the 3D/EF system in enhancing the biodegradability of 2,4-DNT. Overall, the combined 3D/EF process with a G/β-PbO2 anode has relatively high efficiency in degrading solutions containing DNT and can be considered a viable treatment option for wastewater containing substances such as 2,4-DNT.

MgMnxOy-GAC particle electrode for effective peroxone oxidation: High salinity organic wastewater treatment with synergistic electrocatalytic ozonation

A three-dimensional electro-peroxone (3D-EP) system achieved efficient degradation of high salinity organic wastewater and showed significant implications for potential application. Herein, an MgMn-granule-activated carbon (GAC) particle electrode was developed through impregnation calcination and applied in multipollutant removal. The integration of electrolysis, ozone application, and MgMn-GAC in the 3D-EP system manifested strong synergy, leading to successful elimination of all phenol within 30 min due to ample hydroxyl radical production. The energy consumption of MgMn-GAC was 1.86 kWh·m−3 and the specific energy consumption was 0.033 kWh·g−1 COD, exhibiting high electrical energy utilization efficiency under low applied current and low O3 exposure conditions. After six consecutive reaction experiments, COD removal reached 95.6 %, demonstrating remarkable catalytic activity and cycling stability. The study findings indicate that this material could be used as a low-cost particle electrode for practical wastewater treatment.

Pretreatment of hypersaline and high-organic wastewater with a three-dimensional electrocatalytic system: a pilot-scale study.

The three-dimensional electrocatalytic oxidation (3DEO) is a promising electrochemical system in the treatment of refractory wastewater, but still far from large-scale applications. In this work, we prepared 146.5 Kg Ti-Sn-Sb@γ-Al2O3 particle electrodes to construct a 3DEO system for the pretreatment of hypersaline and high-organic wastewater in an industrial park sewage plant, with activated carbon particle electrodes as a comparison. The average COD removal rates of Ti-Sn-Sb@γ-Al2O3 and activated carbon-based 3DEO systems were 24.43 and 48.73%, respectively, and the energy consumption of the two 3DEO systems were 102.8 and 31.4 kWh/Kg COD, respectively. However, compared to the negligible enhancement of wastewater biodegradability in the activated carbon 3DEO system, the Ti-Sn-Sb@γ-Al2O3 3DEO system greatly improved the biochemical index (B/C) from 0.021 to 0.166 (by 690.5%). Due to its superior catalytic capacity, Ti-Sn-Sb@γ-Al2O3 outperforms activated carbon in improving biodegradability as the latter relies mainly on adsorption. The results of this work provide a 3DEO engineering practice experience on the pretreatment of hypersaline and high-organic wastewater.

Study on 3D electrochemical degradation of tetracycline hydrochloride by using Fe/Cu/Mn trimetal-doped granular activated carbon: Reactor, mechanism and regeneration

In this study, Fe/Mn/Cu trimetal-doped activated carbon particle electrodes (FMC-AC) were filled into a novel three-dimensional electrochemical reactor (N3D-FMC-AC) for the degradation of tetracycline hydrochloride (TCH). It was derived from different doping experiments that trimetallic doping was preferred over bimetallic and monometallic doping and that there were synergistic effects between Fe, Mn, and Cu. The optimal ratio of trimetallic doping was determined by orthogonal experiments, which could obtain 97.03% TCH degradation in 80 min. EPR analysis and radical quenching effect experiments revealed the presence of ·OH and ·SO4−. Compared with the common 3D electrochemical reactor filled with FMC-AC (C3D-FMC-AC), the novel 3D electrochemical reactor filled with activated carbon (N3D-AC),and the 2D electrochemical reactor (2D), it was found that N3D-FMC-AC can activate the production of more ·OH and ·SO4−, while OH was the dominant reactive species for TCH degradation. Besides, various degradation routes of TCH were proposed, and the toxicity of intermediates was evaluated. The characterizations by SEM, XRD, and XPS indicated that the cathodic reduction reaction could facilitate electron transfer to Fe(III), Mn(III), and Cu(II), triggering the sustainable Fe(II)/Fe(III), Mn(I)/Mn(III)/Mn(IV), or Cu(I)/Cu(II) redox cycles. The above results suggested that the N3D-FMC-AC process was an efficient and sustainable technology for TCH wastewater treatment and provided a reference for the treatment of tetracycline-type wastewater.

Hierarchically bread-derived carbon foam decorated with defect engineering in reduced graphene oxide/carbon particle nanocomposites as electrode materials for solid-state supercapacitors

The rational design of defective sites and atomic structure of electrode materials for energy storage devices still remains a challenge. Herein, hierarchically activated carbon foam (ACF) from bread has been developed. The density functional theory (DFT) calculation reveals that oxygen defects can form in the reduced graphene oxide/carbon particle (rGO/CP) derived from graphene oxide frameworks (GOFs) by adding the reducing agent. The synergistic effects of the internal porous architecture of ACF and external interface coupling formed by the defect-rich rGO/CP nanocomposites can provide more electrons to adsorb -OH anions resulting in superior electrochemical energy storage performance. Therefore, the ACF-rGO/large-scale carbon particle (ACF-rGO/LCP) electrodes show ultrahigh specific capacitance (521 F g−1) at a current density of 0.5 A g−1 and outstanding cycling stability with capacitance retention of 96.4 % over 12,000 cycles. Furthermore, the assembled binder-free supercapacitor using KOH/polyvinyl alcohol (PVA) as a gel electrolyte, displays a high energy density of 27.5 W h kg−1 with a power density of 472 W kg−1, and a capacitance retention of 95.2 % after 12,000 cycles. This work provides a novel pathway to prepare high-performance supercapacitors via the treatment of food waste and the recycling of carbohydrate resources.

Preparation of Granular Activated Carbon Particle Electrode Loaded with Co3O4 and its Effect on Amoxicillin Wastewater Treatment

In this work, granular activated carbon (GAC) loaded with Co3O4 catalyst (Co3O4/GAC) was used as a particle electrode for three-dimensional (3D) electrochemical treatment of amoxicillin (AMX) wastewater. The morphology, crystal structure, surface chemical bonds, specific surface area, and pore structure of the particle electrodes were characterized. Considering AMX and TOC removal rates and electrical energy consumption (EEC), the optimal manufacturing conditions of the Co3O4/GAC were determined as the calcination temperature of 700 °C, the calcination time of 5 h, and the impregnation time of 3 h, respectively. The measurement of electrochemical impedance spectroscopy showed that the interfacial electron transfer property of Co3O4/GAC was much improved compared with GAC. AMX removal rate (96.0%, 40 min), TOC removal rate (84.4%, 2 h), and EEC (87.2 kWh kg−1 TOC) of the 3D-Co3O4/GAC system were all significantly improved compared to the 3D-GAC system (77.9%, 40.3%, 232.9 kWh kg−1 TOC) and the 2D system (66.4%, 3.9%, 2080.3 kWh kg−1 TOC) under the same operating conditions. It was confirmed that Co3O4/GAC catalytically generates ·OH and H · radicals and increases the conductivity inside the reactor. The degradation of AMX was confirmed using ultraviolet-visible spectroscopy and the degradation mechanism of AMX in the 3D-Co3O4/GAC system was proposed.

Nano α-Fe2O3 Self-Assembled Hybrid Biofilm Boosts Hydrogen Autotrophic Denitrification in a Three-Dimensional Biofilm Electrode Reactor

The performance of three-dimensional biofilm electrode reactors (3D-BERs) in hydrogen autotrophic denitrification is determined by electroactive biofilms. Herein, a self-assembled hybrid biofilm (SAHB) is developed on granular activated carbon particle electrodes by incorporating nano α-Fe2O3. The influences of operating parameters such as current, influent concentration, and hydraulic retention time (HRT) on denitrification are investigated as well as the mechanisms of SAHB-improved denitrification. The results indicate that SAHB achieves a high autotrophic denitrification rate of 4.20 mg TN/L/h under 40 mA current, 100 mg/L nitrate, and 26 h HRT, outperforming the naturally formed biofilm by 23.53%. SAHB contains more microorganisms than naturally formed biofilms, revealing that nano α-Fe2O3 is conducive to trapping free microorganisms on particle electrodes. SAHB enriches denitrification-related genes and increases corresponding enzyme activities (particularly nitrite reductase). According to metagenomic sequencing, nano α-Fe2O3 addition at a current level of 40 mA appears to favor denitrification via the nirS-dependent pathway probably due to its high affinity for cytochrome C. Metagenomic binning reveals that the microorganism associated with Zoogloeaceae (Rhodocyclales order) in SAHB may play a pivotal role in hydrogen autotrophic denitrification. This work develops a novel denitrification system, furthering our understanding of hydrogen autotrophic denitrification in 3D-BERs.

Enhanced norfloxacin degradation by three-dimensional (3D) electrochemical activation of peroxymonosulfate using Mn/Cu co-doped activated carbon particle electrode

In this study, Mn/Cu co-doped activated carbon (MCAC) particle electrodes were applied in the three-dimensional (3D) electrical activation of peroxymonosulfate process (E-PMS-MCAC) for norfloxacin (NOF) degradation. Several comparative experiments demonstrated a significant synergy between catalytic and electric activation of PMS in the E-PMS-MCAC process, which could obtain 90.81 % of NOF removal within 60 min. Quenching experiments and EPR analyses revealed thatSO4·-, •OH, 1O2, and reactive Mn(III) were all involved in the E-PMS-MCAC process, while •OH was dominant reactive species for NOF degradation. The different generation ways of reactive species were also explored. Besides, multiple degradation pathways of NOF were proposed, and the toxicity of intermediates was assessed as well. The characterizations of SEM, XRD, and XPS indicated that the cathodic reduction reaction could facilitate electron transfer to Mn(IV), Mn(III), and Cu(c), triggering the sustainable Mn(I)/Mn(III)/Mn(IV) or Cu(I)/Cu(II) redox cycle. It was noted that the addition of Cl- enhanced the NOF removal, while the presence of HCO3-, NO3-, and H2PO4- inhabited it. Finally, the removal efficiencies of other contaminations including p-nitrophenol (PNP), carbamazepine (CBZ), sulfamethoxazole (SMX), and tetracycline hydrochloride (TCH) were also investigated in the E-PMS-MCAC process. All above results suggested that the E-PMS-MCAC process was a high-efficiency and sustainable technology for organic wastewater treatment.

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 269.7m2g-1 and a pore size of 3.17nm, 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 Ni2%/Ce0.5%/Mn2.5%-NOMC particle electrode reaches 224.65mFcm-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 60min over a wide range of pH values, with an initial phenol concentration of 150mgL-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 20min 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.

Treatment of wastewater containing methyl orange dye by fluidized three dimensional electrochemical oxidation process integrated with chemical oxidation and adsorption

The integrated high-efficiency treatment technology for dye industry wastewater is one of the current research hot topic in industrial wastewater treatment area. This article reports a new fluidized three-dimensional electrochemical treatment process integrating activated carbon adsorption, direct electro-oxidation and ·OH oxidation. In the process, activated carbon is polarized in a fluidized bed electrochemical reactor to enhance the direct electro-oxidation and ·OH oxidation, and there is a synergistic effect of effective adsorption and electrochemical oxidation to strengthen the treatment efficiency. When 200 mg/L methyl orange is processed, its removal rate reaches 99.9% in 30min, and the synergistic efficiency is 57.3%. After 8 cycles of activated carbon reusage in the process, the removal rate of methyl orange still kept at 89.2%. It is also founded that the activated carbon maintains 64.5% of its original adsorption capacity during the cycle. These results shows its interesting application potential in the fields of high-efficiency, low-cost and green treatment of various industrial organic wastewaters. Further improvements should focus on the development of continuous operation model and the improvement of the activated carbon electro-catalytic performance and the practical regeneration ways of the activated carbon particle electrodes.

The degradation of sulfamilamide wastewater by three-dimensional electrocatalytic oxidation system composed of activated carbon bimetallic particle electrode

Antibiotics remaining in wastewater can lead to serious environmental problems, such as bacterial drug resistance and biological toxicity. Electrocatalytic oxidation is becoming an effective method to degrade antibiotics. In this study, we simply synthesized bimetallic oxide activated carbon particle electrode (GAC-Co-Mn) by impregnation method and designed a bench-scale electrocatalytic reaction tank for the first time. Then, a three-dimensional electrocatalytic oxidation system composed of GAC-Co-Mn particle electrode and electrocatalytic reaction tank was used to degrade sulfanilamide antibiotic wastewater. The removal efficiency and mechanism of sulfanilamide (SA) were studied by UV spectrophotometry and ultra-performance liquid chromatography/triple quadrupole mass spectrometry. TOC-L analyzer was used to determine the contents of total organic carbon (TOC) and total nitrogen (TN) of SA wastewater before and after degradation. Electron paramagnetic resonance spectroscopy was used to confirm the production of hydroxyl radicals (•OH). The electrocatalytic activity of the materials was investigated by electrochemical workstation. In addition, we found that this three-dimensional electrocatalytic oxidation system not only has good degradation efficiency for SA, but also has good degradation efficiency for 2,4-dinitrophenol, p-nitroaniline and p-aminobenzenesulfonic acid. Moreover, GAC-Co-Mn still has good degradation efficiency after 6 cycles, indicating that GAC-Co-Mn has good structural stability. Therefore, we believe that the method has good application potential in the field of water treatment.

Improved degradation of diuron herbicide and pesticide wastewater treatment in a three-dimensional electrochemical reactor equipped with PbO2 anodes and granular activated carbon particle electrodes

The electrocatalytic performance of porous carbon felt/PbO2 and planar titanium/PbO2 anodes in a three-dimensional electrochemical reactor (3DER) equipped with granular activated carbon (GAC) particle has been studied for synergistic degradation of diuron herbicide (DIU) and treatment of pesticide wastewater. The results showed that porous carbon felt/PbO2 anode in addition to high stability can provide around three times more surface area than titanium/PbO2 for degradation reactions. Optimization of DIU degradation in 3DER system with carbon felt/PbO2 anode was performed by a five-level rotatable central composite design. The TOC mineralization rate under optimal conditions (pH = 4.7, current density = 13.5 mA cm−2, Na2SO4 concentration = 0.04 M and DIU concentration = 40 mg L−1) for the 3ٍِDER system with carbon felt/PbO2 and titanium/PbO2 anodes after 50 min were 100% and 63.8%, respectively. However, the electrocatalytic efficiency of carbon felt/PbO2 and titanium/PbO2 anodes in the absence of GAC particles to remove TOC was 85.5 and 42.7%, respectively. The energy consumed in the 3DER system equipped with carbon felt/PbO2 anode was 2.28 times less than the 3DER system with titanium/PbO2. The contribution of direct and indirect oxidation of DIU in 3DER degradation systems was determined by radical scavenging technique. The safety of the anodes was evaluated for Pb2+ leakage. The DIU degradation pathway was proposed based on the intermediates identified by LC-MS. The performance of optimized 3DER systems was evaluated for treatment of real pesticide wastewater. The chemical oxygen demand (COD) removal efficiency after 300 min of reaction in the 3DER system with carbon felt/PbO2 and titanium/PbO2 electrodes was 95% and 62.5%, respectively.

Three-dimensional Electro-Fenton degradation for fulvic acids with Cu-Fe bimetallic aerogel-like carbon as particle electrode and catalyst: Electrode preparation, operation parameter optimization and mechanism

In this study Cu-Fe bimetallic aerogel-like carbon based on sodium alginate (SA) was prepared as catalytic particle electrode by freeze-drying and carbonization process. The characterization indicates that Cu and Fe were loaded on the surface and inside SA-based biomass carbon (SAC) in the form of a zero-valent copper-iron alloy to form a Cu-Fe/Sodium alginate Carbon (Cu-Fe/SAC) particle electrode. After using a three-dimensional Electro-Fenton (3D-EF) system with the prepared particle electrode, the optimal experimental operating parameters for removal of fulvic acid (FA) were obtained as follows: voltage 2.5 V, pH 5.4, and catalyst dosage 4 g/L. A removal efficiency from 82.9% to 74.4% for FA was achieved in a wide pH range of 3–7. Comparison experimental results indicate that the 3D-EF system with bimetallic Cu-Fe/SAC as the catalytic particle electrode (CPE) has higher FA degradation rate and mineralization efficiency than two-dimensional Electro-Fenton (2D-EF) system, even higher than the 3D-EF system with Cu/SAC or Fe/SAC. Hydroxyl radicals (·OH) trapping experiments showed that the main contribution to FA degradation and mineralization in the 3D-EF system would be the ·OH radical produced by a heterogeneous Fenton-like reaction. The comparison and trapping experiment results indicate that the possible mechanism of the 3D-EF with Cu-Fe/SAC as CPE for FA degradation may involve adsorption, anode oxidation, heterogeneous and homogeneous Fenton-like reactions.

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.

Enhanced organics degradation by three-dimensional (3D) electrochemical activation of persulfate using sulfur-doped carbon particle electrode: The role of thiophene sulfur functional group and specific capacitance

For further enhancing the electrochemical oxidation performance, sulfur-doped carbon particle electrode was employed in the three-dimensional (3D) electro-assisted activation of persulfate process (ACS/PS/EC). Herein, an in situ S-doped activated carbon (ACS) was prepared and applied as the particle electrode as well as catalyst in ACS/PS/EC system. Several carbon particle electrodes with different annealing temperature were prepared and characterized via EA, BET, XPS and Raman spectra. Cyclic voltammetry (CV) was perform to obtain the specific capacitance and investigate the interfacial electron transfer of ACS particle. The results of comparative experiments showed significant synergy between electric and catalytic activations of PS. Especially, the as-prepared sample treated at 850 °C (ACS-850) exhibited an outstanding catalytic performance, and the phenol degradation rate was greatly improved by nearly 100% with the application of electric field. By comparing of several carbon particle electrodes with different functional groups and specific capacitances, it is revealed that thiophene sulfur functional group is the mainly active site for both electric and catalytic activation of PS, and the specific capacitance acts as assistant factor. Quenching experiments proved that the 3D electro-assisted activation of PS proceeded through both radical and non-radical pathway. Possible mechanism for ACS/PS/EC electrochemical process was proposed.

Comparative Study on Electrochemical Treatment of Cyanide Wastewater.

The electrochemical treatment of wastewater is widely used for cleaning due to its efficiency. In this paper, two-dimensional (2D) and three-dimensional (3D) electrochemical systems were used to treat cyanide wastewater. The effect of the applied voltage and the material of the main electrode on the removal of various ions and the characteristics of chemical reactions were mainly studied. The results show that the applied voltage was the key effect of the electrochemical treatment process. The removal of ions from the wastewater at 2 V is mainly due to the effect of electro adsorption and enrichment precipitation, while at 4 V, it is mainly due to anodization and cathodic deposition. The treatment effect of the 3D electrode system was significantly better than the 2D system. The 3D electrode system by used granular activated carbon as the particle electrode, with the carbon filled stainless mesh (CM) and coal based electrode (CB) as the main electrode, the treatment effect were better than main electrode of stainless steel mesh (M). The 3D system with CB as the main electrode had an applied voltage of 4 V, a treatment time of 5 h, plate spacing of 10 mm, and the dosage of activated carbon particles was 2 g. The removal rates of CNT, Cu, Zn, CN−, and SCN− were 94.14, 94.53, 98.14, 98.55, and 93.13%, respectively. The main reaction in anode was the electroly oxidation of CN− and SCN−, while the electrolytic deposition of Cu, Zn, and other metal ions in the cathode surface. There were not only adsorption and electric adsorption of various ions, but also an electrolytic deposition reaction of Cu, Zn, and other metal ions on the surface of the activated carbon particle electrode. During the electrochemical reaction, the concentration of hydrogen ions near the anode increases locally, which produces the precipitation of CuSCN, Cu2Fe(CN)6, and Zn2Fe(CN)6, etc. in the solution, which are helpful for the removal of cyanide and heavy metal ions in cyanide wastewater.

Hydroxyapatite nanoparticle functionalized activated carbon particle electrode that removes strontium from spiked soils in a unipolar three-dimensional electrokinetic system

Biohazard performance of Sr radionuclide can be significantly magnified by its release from the contaminated sedimentation. In this study, hydroxyapatite nanoparticle-functionalized activated carbon electrode (AC-HAP) was synthesized and stacked to the cathode compartment of the electrokinetic (EK) system to develop a unipolar three-dimensional (3D) electrochemical process for Sr2+ removal from spiked soils. Sr2+ adsorption by AC-HAP can be fitted by the pseudo-first-order and pseudo-second-order kinetic models and the Langmuir, Freundlich, and Temkin isotherm models. The largest monolayer adsorption capacity of AC-HAP of 69.49 mg g−1 was evaluated in the pH range of 10–12 and at 40 °C. 3D EK further intensified the adsorption process of AC-HAP and the corresponding Sr2+ removal from aqueous environments. Voltage gradients and proposing time had a significant effect on the migration and transmission of Sr2+ in the electrolyzer. The influence of competitive ions on Sr2+ removal in the stock solutions followed Al3+ < Mg2+ < K+ < Na+ < Ca2+ while followed Al3+ < Na+ < K+ < Mg2+ < Ca2+ in 3D EK. The first three cycles for AC-HAP had taken roughly 50% of the reusability percentage. Sr2+ removal from spiked samples in 3D EK was achieved by acid dissolution, electromigration, and selective uptake on particle electrode.

In-situ preparation of biochar-loaded particle electrode and its application in the electrochemical degradation of 4-chlorophenol in wastewater

In order to effectively degrade 4-chlorophenol in wastewater, a biochar-loaded particle electrode was prepared using an in-situ method. The method employed bagasse as the raw material, KOH as the activator, SnCl4·5H2O, MnCl2·4H2O and SbCl3 as the modifiers. Furthermore, X-ray diffraction, scanning electron microscopy and energy dispersive spectrometer were used to characterize the crystal composition, morphology and elemental compositions of the proposed particle electrode. The electrochemical performance of the proposed particle electrode was analyzed using an electrochemical workstation. A three-dimensional packed-bed electrochemical reactor was constructed using the loaded biomass carbon particle electrodes. The effects of different loaded biomass carbon particle electrodes on the electrochemical degradation of 4-chlorophenol were studied, and the mechanism of electrochemical degradation of 4-chlorophenol was discussed. The results showed that the effect of the supported biomass carbon particle electrode on the degradation of 4-chlorophenol was significantly higher than that of the unsupported biomass carbon particle electrode. Additionally, the electrochemical degradation of 4-chlorophenol was greatly influenced by the biomass carbon particle electrode with different loading and concentration. The removal efficiencies of 4-chlorophenol using the electrochemical treatment under the studied experimental conditions were found in the following descending order: Mn/AC > Sn/AC > Sb/AC. Among them, the biomass carbon particle electrode prepared using 150 g L−1 MnCl2·4H2O showed the best treatment effect for 4-chlorophenol. After electrochemical treatment of 500 mg L−1 of 4-chlorophenol-simulated wastewater for 1 h, the removal efficiency of 4-chlorophenol reached 99.93%.

Treatment of Landfill Leachate by Combined Submerged Membrane Bioreactor (SMBR) and Electrochemical Oxidation

To efficiently treat landfill leachate, we prepared a new integrated submerged membrane bioreactor (SMBR) and oxidation technology. Our results, under organic loading rates of 2.0–2.3 kg COD/(m3 ·d), showed that through SMBR we can acquire removal efficiencies of 91.2% and 87.3% for ammonia and chemical oxygen demand (COD), respectively. A Ti/RuO2–IrO2 anode and stainless-steel cathode combination was engaged to carry out electrochemical oxidation of SMBR permeate. Ammonia and COD were removed after 3 h electrochemical oxidation (at 40 mA/cm2 current density), and achieved 93.5% and 66.9% removal efficiency with activated carbon particle electrode introduced in the three-dimensional electrodes, respectively. The higher removal efficiency for ammonia nitrogen than COD can be rendered by excited chloride ions, as they affect the competition between organic matter and ammonia nitrogen. Thus, SMBR combined with electrochemical oxidation possesses good prospects to be applied for efficient reduction of ammonia and COD in landfill leachates.