Degradation of p-nitrophenol in a BES-Fenton system based on limonite

Bio-electro-fenton system assisted with metal-organic framework for degradation of bis-phenol S in wastewater as an emerging contaminant

The bio-electro-fenton (BEF) system is a novel technology that can be utilized to degrade both emerging and persistent pollutants while producing clean, green, and sustainable energy. Various catalysts that have a high active surface area are employed in these systems to enhance the oxygen reduction reaction (ORR) efficiency. In this study, the Nickel/Cobalt metal-organic framework (Ni/Co BTC-MOF) as heterogeneous catalyst was synthesized and deposited by the cathodic electrochemical deposition method on the carbon felt (CF) and graphite plate (GP) electrodes. The results of FT-IR, Field Emission Scanning Electron Microscopy (FE-SEM), X-ray Diffraction (XRD), and Energy Dispersive X-ray spectroscopy (EDS) analysis proved that the synthesis of Ni/Co-BTC MOF successfully carried out. The performance and positive effect of the modified electrodes in ORR were investigated and compared in electrical energy generation. Finally, bio-electro-degradation of bisphenol-S (BPS) as one of the endocrine-disrupting compounds (EDCs) was studied by the optimal modified electrode. According to the results of electrochemical experiments, the highest maximum power density is equal to 133.6 mW/m2, which is related to Ni/Co-BTC@CF, and the highest production voltage is related to Ni/Co-BTC@CF, Ni/Co-BTC@GP, CF, and GP, respectively. The removal efficiency levels of bisphenol S in this system at different concentrations of 1.0, 5.0, and 10.0 mg/l after 24 h were 98.0%, 84.0%, and 41.0%, respectively. Based on the obtained results, the improved BEF system with Ni/Co-BTC@CF catalyst can be a suitable technology to achieve more electricity flow and at the same time have a positive effect on the decomposition of bisphenol S pollutant.

Elimination of pharmaceuticals from wastewater using microbial fuel cell-based bio-electro-Fenton process

This study highlights the potential of the microbial fuel cell (MFC)-based bio-electro-Fenton (BEF) process as an efficient and highly adaptable strategy for wastewater treatment. The research aims to optimize the pH of the cathodic chamber (3-7) and catalyst doses (Fe) (0-18.56%) on the graphite felt (GF) cathode, and examine the effect of operating parameters on chemical oxygen demand (COD) removal, mineralization efficiency, pharmaceuticals (ampicillin, diclofenac, and paracetamol) removal, and power generation. The study found that lower pH and higher catalyst dosage on the GF led to better performance of the MFC-BEF system. Under neutral pH, mineralization efficiency, paracetamol removal, and ampicillin removal were enhanced by 1.1 times, and power density improved by 1.25 times as catalyst dosage increased from 0 to 18.56%. Additionally, employing full factorial design (FFD) statistical optimization, the study identifies the optimized conditions for maximum COD removal, mineralization efficiency, and power generation, which are determined to be a pH of 3.82 and a catalyst dose of 18.56%.

Degradation of p-Nitrophenol by activated persulfate with carbon-based materials

The removal of p-nitrophenol (PNP) from wastewater was evaluated by the activated persulfate process using different materials - carbon xerogels (XG), carbon nanotubes (CNT), and activated carbon (AC) -, and also using such materials doped with nitrogen (XGM, CNTM and ACM). These carbon materials were impregnated with 2 wt.% of iron and tested in the oxidative process to assess the influence of their textural and surface chemical properties. The carbon-based materials' properties influence the efficiencies of the adsorption and oxidative processes; in adsorption, the materials with higher specific surface areas (S_BET), i.e. AC (824 m²/g) and Fe/AC (807 m²/g), have shown to be the most promising (having achieved a PNP removal of about 20%); on the other hand, in the activated persulfate process the carbon or iron-containing carbon materials with the highest mesoporous areas (S_meso) were the preferential ones - XG and Fe/XG, respectively - reaching removals of 47.3% and 75.7% for PNP and 44.9 and 63.3% for TOC, respectively. Moreover, the presence of nitrogen groups on the samples' surface benefits both processes, being found that PNP degradation and mineralization increase with the nitrogen content. The stability of the best materials (XGM and Fe/XGM) was evaluated during four cycles, being noticed that while XGM lost catalytic activity, the Fe/XGM sample remained stable without leaching of iron. The quantification of intermediate compounds formed during persulfate oxidation was performed, and only oxalic acid was detected, in addition to PNP, being that their contribution to the TOC measured was higher than 99%. Experiments carried out in the presence of radical scavengers proved that only the sulfate radical is present under the acidic conditions used. Complete PNP oxidation and TOC removal of ∼96% were reached for the activated persulfate process, proving to be more attractive than the Fenton one.

Chitosan Fibers Loaded with Limonite as a Catalyst for the Decolorization of Methylene Blue via a Persulfate-Based Advanced Oxidation Process

Wastewater generated from industries seriously impacts the environment. Conventional biological and physiochemical treatment methods for wastewater containing organic molecules have some limitations. Therefore, identifying other alternative methods or processes that are more suitable to degrade organic molecules and lower chemical oxygen demand (COD) in wastewater is necessary. Heterogeneous Fenton processes and persulfate (PS) oxidation are advanced oxidation processes (AOPs) that degrade organic pollutants via reactive radical species. Therefore, in this study, limonite powder was incorporated into porous regenerated chitosan fibers and further used as a heterogeneous catalyst to decompose methylene blue (MB) via sulfate radical-based AOPs. Limonite was used as a heterogeneous catalyst in this process to generate the persulfate radicals (SO₄^-·) that initiate the decolorization process. Limonite-chitosan fibers were produced to effectively recover the limonite powder so that the catalyst can be reused repeatedly. The formation of limonite-chitosan fibers viewed under a field emission scanning electron microscope (FESEM) showed that the limonite powder was well distributed in both the surface and cross-section area. The effectiveness of limonite-chitosan fibers as a catalyst under PS activation achieved an MB decolorization of 78% after 14 min. The stability and reusability of chitosan-limonite fibers were evaluated and measured in cycles 1 to 10 under optimal conditions. After 10 cycles of repeated use, the limonite-chitosan fiber maintained its performance up to 86%, revealing that limonite-containing chitosan fibers are a promising reusable catalyst material.

Efficient degradation of organic compounds in landfill leachate via developing bio-electro-Fenton process

Efficient and harmless disposal of landfill leachate has attracted increasing attention. In this study, the bio-electro-Fenton method was investigated and developed to degrade the organic compounds in landfill leachate by hydroxyl radical oxidation. The optimal operational parameters (i.e., pH and external voltage) of the bio-electro-Fenton system were detected. Under the conditions of pH 2, 0.6 V, the highest total chemical oxygen demand (COD) decrement efficiency was obtained (about 70%), with apparent removal constant at 6 h (k_app-6h) of about 0.12 h^-1. Subsequently, to further increase the degradation efficiency, functionalized carbon black and functionalized carbon nanotube (FCNT) were prepared as catalysts for the cathode electrode modification. With 0.4 mg/cm² FCNT coated on the cathode electrode, 91.3% of the organic compounds were degraded, remaining only 84 mg/L COD (k_app-6h = 0.24 h^-1). In all the reactors, the COD was mainly decreased in 0-6 h, contributing to over 68% of the total degradation efficiency. In the bio-electro-Fenton system, the bio-anode electrode could enhance H₂O₂ production and the conversion between Fe²⁺ and Fe³⁺ by strengthening electrons generation and transportation via the oxidation of organics by biofilms (dominant with Geobacter) covered on the carbon brush.

A new photoelectrochemical cell coupled with the Fenton reaction to remove pollutant and generate electricity under the drive of waste heat

The water and energy crises are becoming increasingly serious with rapid population and economic development. It is urgent to develop new wastewater treatment technologies with high efficiency and low energy consumption. Herein, a solar-salinity nexus cell (called PRC) integrated by a photocatalytic fuel cell and reverse electrodialysis was combined with the Fenton reaction. The PRC-Fenton process can extract electrons from organic wastewater driven by salinity gradient energy for power generation and wastewater remediation in two chambers. The Fenton cathode MOF(2Fe/Co)-GO/GF with good electrocatalytic and photocatalytic activity was developed and optimized in a three-electrode system. GO doping obviously enhanced the catalytic activity and stability of the Fenton cathode. The pollutant (ampicillin, AMP) was simultaneously removed in both anode and cathode chambers of the PRC-Fenton system. AMP removal by the MOF(2Fe/Co)-GO/GF cathode remained above 95% in a wide range of pH values (3.0-7.0). The output current of the PRC-Fenton process was 1.7-2.4 mA. Compared to similar systems, PRC-Fenton is suitable for treating toxic and refractory organic pollutants with green energy in two chambers and generating electricity.

Recent progress in treatment of dyes wastewater using microbial-electro-Fenton technology

Globally, textile dyeing and manufacturing are one of the largest industrial units releasing huge amount of wastewater (WW) with refractory compounds such as dyes and pigments. Currently, wastewater treatment has been viewed as an industrial opportunity for rejuvenating fresh water resources and it is highly required in water stressed countries. This comprehensive review highlights an overall concept and in-depth knowledge on integrated, cost-effective cross-disciplinary solutions for domestic and industrial (textile dyes) WW and for harnessing renewable energy. This basic concept entails parallel or sequential modes of treating two chemically different WW i.e., domestic and industrial in the same system. In this case, contemporary advancement in MFC/MEC (METs) based systems towards Microbial-Electro-Fenton Technology (MEFT) revealed a substantial emerging scope and opportunity. Principally the said technology is based upon previously established anaerobic digestion and electro-chemical (photo/UV/Fenton) processes in the disciplines of microbial biotechnology and electro-chemistry. It holds an added advantage to all previously establish technologies in terms of treatment and energy efficiency, minimal toxicity and sludge waste, and environmental sustainable. This review typically described different dyes and their ultimate fate in environment and recently developed hierarchy of MEFS. It revealed detail mechanisms and degradation rate of dyes typically in cathodic Fenton system under batch and continuous modes of different MEF reactors. Moreover, it described cost-effectiveness of the said technology in terms of energy budget (production and consumption), and the limitations related to reactor fabrication cost and design for future upgradation to large scale application.

Microbial fuel cell coupled Fenton oxidation for the cathodic degradation of emerging contaminants from wastewater: Applications and challenges

Urbanization and industrialization have resulted in the escalation of the occurrence of emerging contaminants (EC) in the wastewater and ultimately to the receiving water bodies due to their bio-refractory nature. The presence of ECs in the water bodies adversely affects all three domains of life, viz. bacteria, archaea and eukaryotes, and eventually the ecosystem. Fenton oxidation is one of the most suitable method that is capable of degrading a variety of ECs by employing a strong oxidizing agent in the form of •OH. The coupling of Fenton oxidation with microbial fuel cell (MFC) offers benefits, such as low-cost, minimal requirement of external energy, and in-situ generation of oxidizing agents. The resulting system, termed as bio-electro-Fenton MFC (BEF-MFC), is capable of degrading the ECs in the cathodic chamber, while harvesting bioelectricity and simultaneously removing oxidizable organic matter from wastewater in the anodic chamber. This review discusses the applications of BEF-MFC for the treatment of dyes, pharmaceuticals, pesticides, and real complex wastewaters. Additionally, the effect of operating conditions on the performance of BEF-MFC are elaborated and emphasis is also given on possible future direction of research that can be adopted in BEF-MFC in the purview of up-scaling.

A review on bio-electro-Fenton systems as environmentally friendly methods for degradation of environmental organic pollutants in wastewater

Bio-electro-Fenton (BEF) systems have been potentially studied as a promising technology to achieve environmental organic pollutants degradation and bioelectricity generation. The BEF systems are interesting and constantly expanding fields of science and technology. These emerging technologies, coupled with anodic microbial metabolisms and electrochemical Fenton's reactions, are considered suitable alternatives. Recently, great attention has been paid to BEFs due to special features such as hydrogen peroxide generation, energy saving, high efficiency and energy production, that these features make BEFs outstanding compared with the existing technologies. Despite the advantages of this technology, there are still problems to consider including low production of current density, chemical requirement for pH adjustment, iron sludge formation due to the addition of iron catalysts and costly materials used. This review has described the general features of BEF system, and introduced some operational parameters affecting the performance of BEF system. In addition, the results of published researches about the degradation of persistent organic pollutants and real wastewaters treatment in BEF system are presented. Some challenges and possible future prospects such as suitable methods for improving current generation, selection of electrode materials, and methods for reducing iron residues and application over a wide pH range are also given. Thus, the present review mainly revealed that BEF system is an environmental friendly technology for integrated wastewater treatment and clean energy production.

A novel bio-electro-Fenton process for eliminating sodium dodecyl sulphate from wastewater using dual chamber microbial fuel cell

The frequent occurrence of surfactants in urban wastewaters represents a multifaceted environmental concern. In this investigation, bio-electro-Fenton-microbial fuel cell (BEF-MFC) was developed for the degradation of sodium dodecyl sulphate (SDS) from wastewater. The synthesised cathode catalyst (powdered activated carbon and iron oxide) facilitated the Fenton reaction in the cathodic chamber of the MFC, concurrently generating a maximum power density of 105.67 mW m-2. The overall performance of the BEF-MFC for SDS removal and power generation excelled the control MFC (C-MFC) having carbon black coated cathode under similar operating conditions. Although, the rate of SDS degradation was favourable in acidic pH, under neutral pH, 70.8 ± 6.4% of SDS degradation was achieved in 120 min in BEF-MFC. A comparison of environmental impacts of BEF-MFC with up-flow MFC and electrochemical oxidation using life cycle assessment tool suggests that BEF-MFC can be one of the promising technologies for the tertiary treatment of wastewater.

TBO Degradation by Heterogeneous Fenton-like Reaction Using Fe Supported over Activated Carbon

This study reports on the synthesis, immobilization, and stabilization of iron (Fe) particles in activated carbon (AC) from date stem material for the heterogeneous Fenton-like removal of hazardous pollutants from water. AC-Fe was synthesized through a simple and sustainable chemical reaction using and resulting in an environmentally friendly material (AC-Fe). X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray analyses (EDX) were used to characterize the synthesized samples. XRD, FTIR and XPS results showed the successful incorporation of iron particles onto AC. SEM images indicated smooth surfaces with clearly visible Fe particles. Compared to pure AC, AC-Fe showed higher degradation rates of toluidine blue O (TBO) dye. The effects of the initial pH and TBO and H2O2 concentrations on TBO degradation were investigated. The AC-Fe catalyst proved highly efficient in the Fenton-like degradation of TBO (50 ppm), with the removal of up to 99% in 3 min. This catalyst was used efficiently for up to four repeated cycles. The improved catalytic activity of AC-Fe was related to Fe particles for the generation of HO•. These results prove that date stems—a waste product from agriculture—are a suitable precursor for preparing an appropriate AC and catalyst and for eliminating dyes from an aqueous solution by a heterogeneous Fenton-like reaction. The above results open an interesting avenue for the development of functional green catalysts based on AC-Fe for pollution removal.

A novel bio-electro-Fenton system with dual application for the catalytic degradation of tetracycline antibiotic in wastewater and bioelectricity generation

In this new insight, the potential application of the eco-friendly Bio-Electro-Fenton (BEF) system was surveyed with the aim of simultaneous degradation of tetracycline and in situ generation of renewable bioenergy without the need for an external electricity source. To shed light on this issue, catalytic degradation of tetracycline was directly accrued via in situ generated hydroxyl free radicals from Fenton's reaction in the cathode chamber. Simultaneously, the in situ electricity generation as renewable bioenergy was carried out through microbial activities. The effects of operating parameters, such as electrical circuit conditions (in the absence and presence of external resistor load), substrate concentration (1000, 2000, 5000, and 10 000 mg L⁻¹), catholyte pH (3, 5, and 7), and FeSO₄ concentration (2, 5, and 10 mg L⁻¹) were investigated in detail. The obtained results indicated that the tetracycline degradation was up to 99.04 ± 0.91% after 24 h under the optimal conditions (short-circuit, pH 3, FeSO₄ concentration of 5 mg L⁻¹, and substrate concentration of 2000 mg L⁻¹). Also, the maximum removal efficiency of anodic COD (85.71 ± 1.81%) was achieved by increasing the substrate concentration up to 2000 mg L⁻¹. However, the removal efficiencies decreased to 78.29 ± 2.68% with increasing substrate concentration up to 10 000 mg L⁻¹. Meanwhile, the obtained maximum voltage, current density, and power density were 322 mV, 1195 mA m⁻², and 141.60 mW m⁻², respectively, at the substrate concentration of 10 000 mg L⁻¹. Present results suggested that the BEF system could be employed as an energy-saving and promising technology for antibiotic-containing wastewater treatment and simultaneous sustainable bioelectricity generation.

In this new insight, the potential application of the Bio-Electro-Fenton system was surveyed with the aim of simultaneous degradation of tetracycline and in situ generation of renewable bioenergy without the need for an external electricity source.

An approach to the photocatalytic mechanism in the TiO2-nanomaterials microorganism interface for the control of infectious processes

The approach of this timely review considers the current literature that is focused on the interface nanostructure/cell-wall microorganism to understand the annihilation mechanism. Morphological studies use optical and electronic microscopes to determine the physical damage on the cell-wall and the possible cell lysis that confirms the viability and microorganism death. The key parameters of the tailoring the surface of the photoactive nanostructures such as the metal functionalization with bacteriostatic properties, hydrophilicity, textural porosity, morphology and the formation of heterojunction systems, can achieve the effective eradication of the microorganisms under natural conditions, ranging from practical to applications in environment, agriculture, and so on. However, to our knowledge, a comprehensive review of the microorganism/nanomaterial interface approach has rarely been conducted. The final remarks point the ideal photocatalytic way for the effective prevention/eradication of microorganisms, considering the resistance that the microorganism could develop without the appropriate regulatory aspects for human and ecosystem safety.

Rapid degradation of 2,4-dichloronitrobenzene in single-chamber microbial electrolysis cell with pre-acclimated bioanode: A comprehensive assessment

2,4-dichloronitrobenzene (DClNB) as a typical refractory pollutant, exists in multifarious industrial wastewater widely and poses a serious threat to the environment. An ion exchange membrane (IEM)-free microbial electrolysis cell (MEC) with pre-acclimated bioanode was built and evaluated systematically for treatment of DClNB containing wastewater. Results showed that compared with the non-acclimated or IEM-equipped MECs, the pre-acclimated IEM-free MECs had the best DClNB removal efficiency of 91.3% under COD and DClNB loading rates of nearly 1000 kg m^-3 d^-1 and 100 g m^-3 d^-1. Both of anode pre-acclimation and IEM removal reduced the electron transfer resistance by 71.1 and 194.5 Ω, respectively. Compared to the pre-acclimated IEM-equipped MEC, the cathode current efficiency of pre-acclimated IEM-free MEC increased by 13.7%. Analysis of live/dead cell staining indicated that a higher proportion of live cells was observed in the acclimated anode biofilm (66.1% vs. 47.3%), and the detoxification of DClNB in the pre-acclimated IEM-free MECs was significantly better (p < 0.05) than those of non-acclimated or IEM-equipped MECs. This study contributes to the performance improvement of the MEC process for treatment of toxic industrial wastewater.

A three-dimensional electrode bioelectrochemical system for the advanced oxidation of p-nitrophenol in an aqueous solution

Three-dimensional electrodes serve as more efficient cathodes for the in situ generation of H₂O₂ in microbial fuel cells (MFCs) than two-dimensional electrodes and possess significant electric potentials in the advanced oxidation of organics. In this study, we investigated the performance of a three-dimensional MFC-Fenton system in degrading p-nitrophenol (PNP) in an aqueous solution with the objective of optimizing the operating parameters, including the initial pH, iron dosage, and loading resistance. A corresponding reaction pathway for PNP in the system was also proposed. The results showed that the three-dimensional electrode bioelectrochemical system efficiently oxidized PNP and removed total organic carbon over a short period (64 h). In addition, experiments showed that a lower initial pH enhanced the removal of PNP by the system. The highest removal efficiency of PNP was achieved with an initial iron concentration of 0.025 mol L⁻¹, and a lower or higher iron concentration resulted in decreased PNP degradation. Furthermore, the treatment capacity of the system was remarkably enhanced at a low loading resistance of 20 Ω. Under optimal conditions, the three-dimensional MFC-Fenton system achieved 95.7% PNP removal (within 8 h). Furthermore, the system showed a stable high treatment efficiency of approximately 90% for low PNP concentrations in wastewater over as long as 96 h.

PNP absorbed in and surrounded by GPEs has kinetic favorability in the degradation process by a three-dimensional electrode MFC-Fenton system.

Enhanced Bio-Electro-Fenton degradation of phenolic compounds based on a novel Fe-Mn/Graphite felt composite cathode

Phenolic compounds are problematic byproducts generated from lignocellulose pretreatment. In this study, the feasibility degradation of syringic acid (SA), vanillic acid (VA), and 4-hydroxybenzoic acid (HBA) by Bio-Electro-Fenton (BEF) system with a novel Fe-Mn/graphite felt (Fe-Mn/GF) composite cathode were investigated. The nano-scale Fe-Mn multivalent composite catalyst with core shell structure distributed more evenly on GF surface to form a catalyst layer with higher oxygen reduction reaction performance. Accordingly, the maximum power density generated with Fe-Mn/GF cathode was 48.1% and 238.9% higher than Fe/GF and GF respectively, which further enhanced the in situ generation of H₂O₂ due to the superiority of nano-scale core shell structure and synergistic effect of Fe and Mn species. The degradation efficiency of the three phenolic compounds in the BEF system could reached 100% after optimization of influencing parameters. Furthermore, a possible SA degradation pathway by BEF process in the present system was proposed based on the detected intermediates. These results demonstrated an efficient approach for the degradation of phenolic compounds derived from lignocellulose hydrolysates.

A study of the coupled bioelectrochemical system-upflow anaerobic sludge blanket for efficient transformation of 2,4-dichloronitrobenzene

Coupled bioelectrochemical system-upflow anaerobic sludge blanket (BES-UASB) was utilized for wastewater treatment containing 2,4-dichloronitrobenzene (DClNB). The results indicated that a proper voltage enhanced the DClNB reduction, however, over high voltage presented a negative impact (2.0 V). Synergistic effect of external voltage and anaerobic sludge was observed, and dechlorination efficiency reached 57.8 ± 5.4% in the coupled BES,  which was higher than the sum of anaerobic sludge and electric system (48.2%). Moreover, the coupled system was more tolerant of high salinity and pollutant concentration. Dehydrogenase activity (DHA) was related to microbial electron transfer activity and DHA reached a maximum 453 ± 33 μgTF g^-1VSS h^-1 in the coupled reactor which was 1.6-fold that of the control, meanwhile, extracellular polymeric substances (EPS) content was significantly enhanced in the presence of external voltage. In summary, the coupled BES-UASB systems could be an alternative for removal of recalcitrant pollutants such as DClNB.

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.

Accelerated removal of high concentration p-chloronitrobenzene using bioelectrocatalysis process and its microbial communities analysis

p-Chloronitrobenzene (p-CNB) is a persistent refractory and toxic pollutant with a concentration up to 200 mg/L in industrial wastewater. Here, a super-fast removal rate was found at 0.2-0.8 V of external voltage over a p-CNB concentration of 40-120 mg/L when a bioelectrochemical technology is used comparing to the natural biodegradation and electrochemical methods. The reduction kinetics (k) was fitted well according to pseudo-first order model with respect to the different initial concentration, indicating a 1.12-fold decrease from 1.80 to 0.85 h^-1 within the experimental range. Meanwhile, the highest k was provided at 0.5 V with the characteristic of energy saving. It was revealed that the functional bacterial (Propionimicrobium, Desulfovibrio, Halanaerobium, Desulfobacterales) was selectively enriched under electro-stimulation, which possibly processed Cl-substituted nitro-aromatics reduction. The possible degradation pathway was also proposed. This work provides the beneficial choice on the rapid treatment of high-concentration p-CNB wastewater.

Efficient treatment of aniline containing wastewater in bipolar membrane microbial electrolysis cell-Fenton system

Aniline-containing wastewater can cause significant environmental problems and threaten the humans's life. However, rapid degradation of aniline with cost-efficient methods remains a challenge. In this work, a novel microbial electrolysis cell with bipolar membrane was integrated with Fenton reaction (MEC-Fenton) for efficient treatment of real wastewater containing a high concentration (4460 ± 52 mg L^-1) of aniline. In this system, H₂O₂ was in situ electro-synthesized from O₂ reduction on the graphite cathode and was simultaneously used as source of OH for the oxidation of aniline wastewater under an acidic condition maintained by the bipolar membrane. The aniline was effectively degraded following first-order kinetics at a rate constant of 0.0166 h^-1 under an applied voltage of 0.5 V. Meanwhile, a total organic carbon (TOC) removal efficiency of 93.1 ± 1.2% was obtained, revealing efficient mineralization of aniline. The applicability of bipolar membrane MEC-Fenton system was successfully demonstrated with actual aniline wastewater. Moreover, energy balance showed that the system could be a promising technology for removal of biorefractory organic pollutants from wastewaters.

Bio-Electron-Fenton (BEF) process driven by microbial fuel cells for triphenyltin chloride (TPTC) degradation

The intensive use of triphenyltin chloride (TPTC) has caused serious environmental pollution. In this study, an effective method for TPTC degradation was proposed based on the Bio-Electron-Fenton process in microbial fuel cells (MFCs). The maximum voltage of the MFC with graphite felt as electrode was 278.47% higher than that of carbon cloth. The electricity generated by MFC can be used for in situ generation of H₂O₂ to a maximum of 135.96μmolL^-1 at the Fe@Fe₂O_3(*)/graphite felt composite cathode, which further reacted with leached Fe²⁺ to produce hydroxyl radicals. While 100μmolL^-1 TPTC was added to the cathodic chamber, the degradation efficiency of TPTC reached 78.32±2.07%, with a rate of 0.775±0.021μmolL^-1h^-1. This Bio-Electron-Fenton driving TPTC degradation might involve in SnC bonds breaking and the main process is probably a stepwise dephenylation until the formation of inorganic tin and CO₂. This study provides an energy saving and efficient approach for TPTC degradation.

Efficient treatment of azo dye containing wastewater in a hybrid acidogenic bioreactor stimulated by biocatalyzed electrolysis

In this study, a novel scaled-up hybrid acidogenic bioreactor (HAB) was designed and adopted to evaluate the performance of azo dye (acid red G, ARG) containing wastewater treatment. Principally, HAB is an acidogenic bioreactor coupled with a biocatalyzed electrolysis module. The effects of hydraulic retention time (HRT) and ARG loading rate on the performance of HAB were investigated. In addition, the influent was switched from synthetic wastewater to domestic wastewater to examine the key parameters for the application of HAB. The results showed that the introduction of the biocatalyzed electrolysis module could enhance anoxic decolorization and COD (chemical oxygen demand) removal. The combined process of HAB-CASS presented superior performance compared to a control system without biocatalyzed electrolysis (AB-CASS). When the influent was switched to domestic wastewater, with an environment having more balanced nutrients and diverse organic matters, the ARG, COD and nitrogen removal efficiencies of HAB-CASS were further improved, reaching 73.3%±2.5%, 86.2%±3.8% and 93.5%±1.6% at HRT of 6 hr, respectively, which were much higher than those of AB-CASS (61.1%±4.7%, 75.4%±5.0% and 82.1%±2.1%, respectively). Moreover, larger TCV/TV (total cathode volume/total volume) for HAB led to higher current and ARG removal. The ARG removal efficiency and current at TCV/TV of 0.15 were 39.2%±3.7% and 28.30±1.48 mA, respectively. They were significantly increased to 62.1%±2.0% and 34.55±0.83 mA at TCV/TV of 0.25. These results show that HAB system could be used to effectively treat real wastewater.

p-Nitrophenol degradation and microbial community structure in a biocathode bioelectrochemical system

The biocathode bioelectrochemical system (bioc-BES) was used forp-nitrophenol (PNP) degradation with sodium bicarbonate as the carbon source.

Pilot-scale bioelectrochemical system for efficient conversion of 4-chloronitrobenzene

4-Chloronitrobenzene (4-CNB) is one of the highly toxic contaminants that may lead to acute, chronic or persistent physiological toxicity to ecology and environment. Conventional methods for removing 4-CNB from aquatic environment may be problematic due to inefficiency, high cost and low sustainability. This study develops a pilot-scale bioelectrochemical system (BES, effective volume of 18 L) and examines its performance of bioelectrochemical transformation of 4-CNB to 4-chloroaniline (4-CAN) under continuous operation. The results demonstrate that the initial 4-CNB concentration in the influent and hydraulic retention time (HRT) has a significant impact on 4-CNB reduction and 4-CAN formation. Compared with the conventional anaerobic process in the absence of external power supplied, the 4-CNB conversion efficiency can be enhanced with power supplied due to microbial-mediated electron transfer at the negative cathode potential. At a voltage of 0.4 V and HRT of 48 h, the 4-CNB reduction and 4-CAN formation efficiency reached 99% and 94.1%, respectively. Based on a small external voltage applied, the pilot-scale BES is effective in the conversion of 4-CNB to 4-CAN, an intermediate that is of less toxicity and higher bioavailability for subsequent treatment. This study provides a new strategy and methods for eliminating 4-CNB, making wastewater treatment more economical and more sustainable.

Microbial fuel cell-based biosensors for environmental monitoring: a review

The microbial fuel cell (MFC) is an innovative technology that was initially designed to harness energy from organic waste using microorganisms. It is striking how many promising applications beyond energy production have been explored in recent decades. In particular, MFC-based biosensors are considered to be the next generation biosensing technology for environmental monitoring. This review describes recent advances in this emerging technology of MFC-based biosensors, with a special emphasis on monitoring of biochemical oxygen demand and toxicity in the environment. The progress confirms that MFC-based biosensors could be used as self-powered portable biosensing devices with great potential in long-term and remote environmental monitoring.

Removal of 17β-estrodial in a bio-electro-Fenton system: contribution of oxidation and generation of hydroxyl radicals with the Fenton reaction and carbon felt cathode

A bio-electro-Fenton (BEF) system equipped with a Fe@Fe₂O₃/non-catalyzed carbon felt (NCF) cathode was optimized, and the generation of hydroxyl radicals was confirmed for E2 removal.

A novel hybrid anion exchange membrane for high performance microbial fuel cells

A novel titanium dioxide (TiO₂)–quaternized poly(vinyl alcohol) (QAPVA) hybrid anion exchange membrane (T membrane) is prepared, and its feasibility for use in microbial fuel cells (MFCs) is investigated in this study.