Lu Wang, Dayong Xu, Qingyun Zhang et al.

Environmental Science and Pollution Research • 2021

A microbial fuel cell coupled with constructed wetland (CW-MFC) was built to remove heavy metals (Zn and Ni) from sludge. The performance for the effects of substrates (granular activated carbon (GAC), ceramsite) and plants ( Iris pseudacorus , water hyacinth ) towards the heavy metal treatment as well as electricity generation was systematically investigated to determine the optimal constructions of CW-MFCs. The CW-MFC systems possessed higher Zn and Ni removal efficiencies as compared to CW. The maximal removal rates of Zn (76.88%) and Ni (66.02%) were obtained in system CW-MFC based on GAC and water hyacinth (GAC- and WH-CW-MFC). Correspondingly, the system produced the maximum voltage of 534.30 mV and power density of 70.86 mW·m −3 , respectively. Plant roots and electrodes contributed supremely to the removal of heavy metals, especially for GAC- and WH-CW-MFC systems. The coincident enrichment rates of Zn and Ni reached 21.10% and 26.04% for plant roots and 14.48% and 16.50% for electrodes, respectively. A majority of the heavy metals on the sludge surface were confirmed as Zn and Ni. Furthermore, the high-valence Zn and Ni were effectively reduced to low-valence or elemental metals. This study provides a theoretical guidance for the optimal construction of CW-MFC and the resource utilization of sludge containing heavy metals.

M. Abdelkareem, S. Alshathri, M. S. Masdar et al.

Water • 2023

Due to their toxicity, Cr(VI) levels are subject to strict legislation and regulations in various industries and environmental contexts. Effective treatment technologies are also being developed to decrease the negative impacts on human health and the environment by removing Cr(VI) from water sources and wastewater. As a result, it would be interesting to model and optimize the Cr(VI) removal processes, especially those under neutral pH circumstances. Microbial fuel cells (MFCs) have the capacity to remove Cr(VI), but additional research is needed to enhance their usability, increase their efficacy, and address issues like scalability and maintaining stable operation. In this research work, ANFIS modeling and artificial ecosystem optimization (AEO) were used to maximize Cr(VI) removal efficiency and the power density of MFC. First, based on measured data, an ANFIS model is developed to simulate the MFC performance in terms of the Cu(II)/Cr(VI) ratio, substrate (sodium acetate) concentration (g/L), and external resistance Ω. Then, using artificial ecosystem optimization (AEO), the optimal values of these operating parameters, i.e., Cu(II)/Cr(VI) ratio, substrate concentration, and external resistance, are identified, corresponding to maximum Cr(VI) removal efficiency and power density. In the ANFIS modeling stage of power density, the coefficient-of-determination is enhanced to 0.9981 compared with 0.992 (by ANOVA), and the RMSE is decreased to 0.4863 compared with 16.486 (by ANOVA). This shows that the modeling phase was effective. In sum, the integration between ANFIS and AEO increased the power density and Cr(VI) removal efficiency by 19.14% and 15.14%, respectively, compared to the measured data.

Elif DURNA PİŞKİN, N. Genç

Environmental Technology • 2023

ABSTRACT Microbial fuel cell technology draws attention with its ability to directly recover electrical energy from various organic materials. In this study, the operating conditions affecting the oxidation–reduction and electricity generation efficiency of MFC were optimized using the Taguchi Experimental Design model. Optimization was carried out for maximum power density, coulombic efficiency, azo dye removal, and COD removal. With the determined optimum conditions (cathode pH of 3.0, cathode oxygen status of anaerobic, anode substrate of pre-treated, external resistance of 100 Ω, cathode electrode type of plain carbon, cathode electrode surface of 22 cm2, cathode conductivity of 20 µs/cm), 177.03 mW/m2 power density, 7.50% coulombic efficiency, 91.26% azo dye removal efficiency and 21.61% COD removal efficiency were obtained. By Pareto analysis, it was determined that the power density, coulombic efficiency and COD removal efficiency were most affected by the substrate type at the anode, and the azo dye removal was most affected by the catholyte pH. The maximum power density and internal resistance of the MFC operated under optimum conditions were determined as 145.11 mW/m2 and 243.30 Ω, respectively by the polarization curve. Cyclic voltammetry was also performed for the electrochemical characterization of MFC operated under optimum conditions. An anodic peak at −183.2 mV and a cathodic peak at −181.2 mV was visible in the CV curve. GRAPHICAL ABSTRACT

Mary-Rafunzel P. Bandoquillo, Hanna Patricia M. Labrador, K. Pamintuan et al.

2024 2nd International Conference on Power and Renewable Energy Engineering (PREE) • 2024

Plant microbial fuel cell (PMFC) is a bioelectrochemical system developed to generate energy from plant bacteria through photosynthesis without disrupting the soil and plants. In this study, a new design of the PMFC model was introduced using 3D printing technology. Its electricity generation potential was observed using C. comosum as a sample plant for the PMFC set-up. Nine different systems of PMFC stake design with varying numbers and lengths of cathode were examined to determine the optimum surface area ratio of the cathode to the anode and its effect on the power generation of the PMFC design. System 7, with the highest cathode-to-anode surface area ratio, generates the highest power and power density of 0.2879 μW and 22.79 μW/ m2, respectively. It was found that a ratio of approximately 2.829:1 gives the highest average daily power density. Overall, the result of this study shows that the surface area ratio has been found to affect the performance of the PMFC stake design greatly and, with accurate design and material, can serve as an alternative renewable energy source.

A. Netsch, Shaswata Sen, Harald Horn et al.

Biosensors • 2025

Industrially applied bioelectrochemical systems require long-term stable operation, and hence the control of biofilm accumulation on the electrodes. An optimized application of biofilm control mechanisms presupposes on-line, in-situ monitoring of the accumulated biofilm. Heat transfer sensors have successfully been integrated into industrial systems for on-line, non-invasive monitoring of biofilms. In this study, a mathematical model for the description of the sensitivity of a heat transfer biofilm sensor was developed, incorporating the hydrodynamic conditions of the fluid and the geometrical properties of the substratum. This model was experimentally validated at different flow velocities by integrating biofilm sensors into cylindrical pipes and planar mesofluidic flow cells with a carbonaceous substratum. Dimensionless sensor readings were correlated with the mean biovolume measured gravimetrically, and optical coherence tomography was used to determine the sensors’ sensitivity. The biofilm sensors applied in the planar flow cells revealed an increase in sensitivity by a factor of 6 compared to standard stainless steel pipes, as well as improved sensitivity at higher flow velocities.

P. Gotovtsev

Applied Sciences • 2020

There are a number of significant changes taking place in modern city development and most of them are based on the number of recent technological progress. This paper provides a review and analysis of recent approaches of biotechnology that can find a place in today’s cities and discusses how those technologies can be integrated into a city’s Internet of Things (IoT). Firstly, several biotechnologies that focus on rain gardens, urban vertical farming systems, and city photobioreactors are discussed in the context of their integration in a city’s IoT. The next possible application of biofuel cells to the sensor network’s energy supply is discussed. It is shown that such devices can influence the low-power sensor network structure as an additional energy source for transmitters. This paper shows the possibility of bioelectrochemical biosensor applications, discusses self-powered biosensors, and shows that such a system can be widely applied to rainwater monitoring in rain gardens and green streets. Significant attention is paid to recent approaches in synthetic biology. Both cell-based biosensors and bioactuators with synthetic genetic circuits are discussed. The development of cell-based biosensors can significantly enhance the sensing possibilities of a city’s IoT. We show the possible ways to develop cyber-physical systems (CPSs) with the systems mentioned above. Aspects of data handling for the discussed biotechnologies and the methods of intelligent systems, including those that are machine learning-based, applied to the IoT in a city are presented.

Rong Cai, Chiagoziem Ngwadom, Ravindra Saxena et al.

Nature Communications • 2024

Point-of-care sensors, which are low-cost and user-friendly, play a crucial role in precision medicine by providing quick results for individuals. Here, we transform the conventional glucometer into a 4-hydroxytamoxifen therapeutic biosensor in which 4-hydroxytamoxifen modulates the electrical signal generated by glucose oxidation. To encode the 4-hydroxytamoxifen signal within glucose oxidation, we introduce the ligand-binding domain of estrogen receptor-alpha into pyrroloquinoline quinone-dependent glucose dehydrogenase by constructing and screening a comprehensive protein insertion library. In addition to obtaining 4-hydroxytamoxifen regulatable engineered proteins, these results unveil the significance of both secondary and quaternary protein structures in propagation of conformational signals. By constructing an effective bioelectrochemical interface, we detect 4-hydroxytamoxifen in human blood samples as changes in the electrical signal and use this to develop an electrochemical algorithm to decode the 4-hydroxytamoxifen signal from glucose. To meet the miniaturization and signal amplification requirements for point-of-care use, we harness power from glucose oxidation to create a self-powered sensor. We also amplify the 4-hydroxytamoxifen signal using an organic electrochemical transistor, resulting in milliampere-level signals. Our work demonstrates a broad interdisciplinary approach to create a biosensor that capitalizes on recent innovations in protein engineering, electrochemical sensing, and electrical engineering.

Jiwon Woo, E. Y. Lee, Hyo-Suk Park et al.

Journal of Visualized Experiments • 2018

Since the development of CLARITY, a bioelectrochemical clearing technique that allows for three-dimensional phenotype mapping within transparent tissues, a multitude of novel clearing methodologies including CUBIC (clear, unobstructed brain imaging cocktails and computational analysis), SWITCH (system-wide control of interaction time and kinetics of chemicals), MAP (magnified analysis of the proteome), and PACT (passive clarity technique), have been established to further expand the existing toolkit for the microscopic analysis of biological tissues. The present study aims to improve upon and optimize the original PACT procedure for an array of intact rodent tissues, including the whole central nervous system (CNS), kidneys, spleen, and whole mouse embryos. Termed psPACT (process-separate PACT) and mPACT (modified PACT), these novel techniques provide highly efficacious means of mapping cell circuitry and visualizing subcellular structures in intact normal and pathological tissues. In the following protocol, we provide a detailed, step-by-step outline on how to achieve maximal tissue clearance with minimal invasion of their structural integrity via psPACT and mPACT.

Guiping Ren, Yuan Sun, Manyi Sun et al.

Minerals • 2017

Exploring the interplay between sunlight, semiconducting minerals, and microorganisms in nature has attracted great attention in recent years. Here we report for the first time the investigation of the interaction between a hematite photoelectrode and Pseudomonas aeruginosa PAO1 under visible light irradiation. Hematite is the most abundant mineral on earth, with a band gap of 2.0 eV. A hematite electrode was electrochemically deposited on fluorine-doped tin oxide (FTO). It was thoroughly characterized by environmental scanning electron microscopy (ESEM), Raman, and UV–Vis spectroscopy, and its prompt response to visible light was determined by linear sweep voltammetry (LSV). Notably, under light illumination, the hematite electrode immersed in a live cell culture was able to produce 240% more photocurrent density than that in the abiotic control of the medium, suggesting a photoenhanced extracellular electron transfer process occurring between hematite and PAO1. Different temperatures of LSV measurements showed bioelectrochemical activity in the system. Furthermore, I–t curves under various conditions demonstrated that both a direct and an indirect electron transferring process occurred between the hematite photoanode and PAO1. Moreover, the indirect electron transferring route was more dominant, which may be mainly attributed to the pyocyanin biosynthesized by PAO1. Our results have expanded our understanding in that in addition to Geobacter and Shewanella it has been shown that more microorganisms are able to perform enhanced extracellular electron transfer with semiconducting minerals under sunlight in nature.

E. Cook, Yeowon Kim, N. Grimm et al.

Proceedings of the National Academy of Sciences • 2025

Nature-Based Solutions for Urban Sustainability provides comprehensive insights on existing technologies and up-to-date advances in the field of water, wastewater and waste treatment using nature-based approaches and systems. This book highlights: Process fundamentals of nature-based solutions, including hydrodynamics, media, bacteria/media interactions and phytoremediation for pollution control, resource recovery and energy generation.Critical insights on the status, major challenges and modern engineering solutions in nature-based solutions for the treatment of rainwater, storm water, wastewater and solid waste.Advanced methods for valorisation using nature-based solutions through integration with other technologies, such as composting, anaerobic digestion and bioelectrochemical systems.Up-to-date information on modern approaches for deriving value-added operation, by combining nature-based solutions with agricultural practices such as fish farming or protein production.Case studies of nature-based solutions from countries in transition including Thailand, Vietnam, Indonesia and Philippines.This reference textbook is recommended reading for both undergraduate and graduate students pursuing degrees in environmental sciences, technologies, or engineering. It is equally useful for a broader audience including researchers, engineers, and policy makers interested in the field of nature-based solutions for urban sustainability. It is also tailored to be used as an advanced manual for practitioners and consultancies working in the field of diffuse pollution and climate change mitigation. ISBN: 9781789065008 (paperback) ISBN: 9781789065015 (eBook) ISBN: 9781789065022 (ePub)

Natalia Tyszkiewicz, J. Truu, Piotr Młynarz et al.

Frontiers in Microbiology • 2024

Bioelectrochemical systems offer unique opportunities to remove recalcitrant environmental pollutants in a net positive energy process, although it remains challenging because of the toxic character of such compounds. In this study, microbial fuel cell (MFC) technology was applied to investigate the benzene degradation process for more than 160 days, where glucose was used as a co-metabolite and a control. We have applied an inoculation strategy that led to the development of 10 individual microbial communities. The electrochemical dynamics of MFC efficiency was observed, along with their 1H NMR metabolic fingerprints and analysis of the microbial community. The highest power density of 120 mW/m2 was recorded in the final period of the experiment when benzene/glucose was used as fuel. This is the highest value reported in a benzene/co-substrate system. Metabolite analysis confirmed the full removal of benzene, while the dominance of fermentation products indicated the strong occurrence of non-electrogenic reactions. Based on 16S rRNA gene amplicon sequencing, bacterial community analysis revealed several petroleum-degrading microorganisms, electroactive species and biosurfactant producers. The dominant species were recognised as Citrobacter freundii and Arcobacter faecis. Strong, positive impact of the presence of benzene on the alpha diversity was recorded, underlining the high complexity of the bioelectrochemically supported degradation of petroleum compounds. This study reveals the importance of supporting the bioelectrochemical degradation process with auxiliary substrates and inoculation strategies that allow the communities to reach sufficient diversity to improve the power output and degradation efficiency in MFCs beyond the previously known limits. This study, for the first time, provides an outlook on the syntrophic activity of biosurfactant producers and petroleum degraders towards the efficient removal and conversion of recalcitrant hydrophobic compounds into electricity in MFCs.

E. Martínez, A. Sotres, Cristian B Arenas et al.

Energies • 2019

The effect of hydrogen pulse addition on digestion performance of sewage sludge was evaluated as a means for studying the increase in efficiency of methane production. Microbial communities were also evaluated to get an insight of the changes caused by the operational modifications of the digester. An energy evaluation of this alternative was performed considering the theoretical process of coupling bioelectrochemical systems (BES) for the treatment of wastewater along with hydrogen production and the subsequent anaerobic digestion. The addition of hydrogen to sewage sludge digestion resulted in an increase of 12% in biogas production over the control (1353 mL CH4 d−1 at an injection flow rate of 1938 mL H2 d−1). The liquid phase of the sludge reactor and the H2 supplemented one did not show significant differences, thus indicating that the application of hydrogen as the co-substrate was not detrimental. High-throughput sequencing analysis showed slight changes in archaeal relative abundance after hydrogen addition, whereas eubacterial community structure and composition revealed noteworthy shifts. The mass and energy balance indicated that the amount of hydrogen obtained from a hypothetical BES can be assimilated in the sludge digester, improving biogas production, but this configuration was not capable of covering all energy needs under the proposed scenario.

Libin Zhang, Hongling Zhang, Xinbai Jiang et al.

Desalination and Water Treatment • 2018

Cost-effective treatments of recalcitrant pollutants in wastewaters are required. The coupling degradation of p-nitrophenol (PNP) reduction in cathode and p-aminophenol (PAP, reduction product of PNP) oxidation in anode was studied in a bioelectrochemical system (BES) solely catalyzed by bacteria consortia, with no power input. In the cathode chamber, 50 mg L–1 PNP was reduced by 96.2 ± 2.4% within 96 h. PNP reduction efficiency was notably improved than that (63.8 ± 2.6%) in the abiotic cathode control. In the anode chamber, 20 mg L–1 PAP was removed by 94.0 ± 0.6% within 30 h. The reduction and oxidation peaks in cyclic voltammetry curves of the cathode and anode verified the coupled degradation process. Illumina Mi-seq sequencing revealed similar predominant bacteria with different percentages on the cathode and anode. The bacteria composition was more diverse on the anode. At the phylum level, higher prevalence of Chlorobi, Bacteroidetes, Thermi and Actinobacteria on the cathode than that on the anode were discovered. Meanwhile, Thiobacillus, Methanomethylovorans, Sphingobium and Geobacter were superior on the anode than the cathode at the genus level. Coupling treatment of PNP reduction in cathode and PAP oxidation in anode was realized in a bio-catalyzed BES. Enhanced degradation in a self-powered BES is an economical and efficient strategy for the treatment of nitroaromatic pollutants.

T. Kuleshova, P. Zhelnacheva, Z. Gasieva et al.

Russian Journal of Biological Physics and Chemisrty • 2024

The work considers the effect of the nutrient solution composition on the potential difference formation in the root environment. Identification of possible potential-generating ions in bioelectrochemical systems based on electactive plant and microbial interactions was carried out. The electropotential difference in the root environment was measured when growing lettuce with a nutrient solution with a double increased content of magnesium sulfate, potassium chloride and potassium dihydortophosphate. Changes in the electrical conductivity of nutrient solutions in the process of lettuce growing and the differences in the pH and concentrations of calcium, potassium, ammonium, nitrate ions in the upper and lower electrode areas of bioelectrochemical systems are analyzed. An increase in the concentration of potassium chloride and potassium dihydortophosphate in a nutrient solution led to a decrease in both biomass and the average voltage value to 221 mV and 188 mV, respectively, relatively characteristic of the control option with a classic solution of the potential difference 213 mV. The doubling of the magnesium sulfate concentration, on the contrary, caused an increase in the potential difference to an average value of 263 mV and an increase in biomass by more than 30% relative to control. Probably, magnesium sulfate plays a potential role in the formation of electogenic reactions in the root environment.

Fu-neng Tan

2024 International Seminar on Artificial Intelligence, Computer Technology and Control Engineering (ACTCE) • 2024

In recent years, sensors made of chitosan have become a research hotspot due to their advantages of low cost, simple preparation process, rapid response and high sensitivity. In this paper, the preparation method of chitosan sensor and its application in bioelectrochemical sensors are introduced, and its application prospect is prospected.

Silvia Bolognesi, Lluís Bañeras, Elisabet Perona-Vico et al.

Sustainable Energy & Fuels • 0

<jats:p>A novel biorefinery approach, combining microbial electrosynthesis and heterotrophic microalgae, aimed at producing a biodiesel compatible oil from CO<jats:sub>2</jats:sub>.</jats:p>

Sara Díaz-Rullo Edreira, Silvia Barba, Ioanna A. Vasiliadou et al.

Microorganisms • 0

<jats:p>Bioelectrochemical systems are a promising technology capable of reducing CO2 emissions, a renewable carbon source, using electroactive microorganisms for this purpose. Purple Phototrophic Bacteria (PPB) use their versatile metabolism to uptake external electrons from an electrode to fix CO2. In this work, the effect of the voltage (from −0.2 to −0.8 V vs. Ag/AgCl) on the metabolic CO2 fixation of a mixed culture of PPB under photoheterotrophic conditions during the oxidation of a biodegradable carbon source is demonstrated. The minimum voltage to fix CO2 was between −0.2 and −0.4 V. The Calvin–Benson–Bassham (CBB) cycle is the main electron sink at these voltages. However, lower voltages caused the decrease in the current intensity, reaching a minimum at −0.8 V (−4.75 mA). There was also a significant relationship between the soluble carbon uptake in terms of chemical oxygen demand and the electron consumption for the experiments performed at −0.6 and −0.8 V. These results indicate that the CBB cycle is not the only electron sink and some photoheterotrophic metabolic pathways are also being affected under electrochemical conditions. This behavior has not been tested before in photoheterotrophic conditions and paves the way for the future development of photobioelectrochemical systems under heterotrophic conditions.</jats:p>

Wei Li, Xiaohong Chen, Linshen Xie et al.

Water • 0

<jats:p>Due to the deficiency of fresh water resources and the deterioration of groundwater quality worldwide, groundwater remedial technologies are especially crucial for preventing groundwater pollution and protecting the precious groundwater resource. Among the remedial alternatives, bioelectrochemical systems have unique advantages on both economic and technological aspects. However, it is rare to see a deep study focused on the information mining and visualization of the publications in this field, and research that can reveal and visualize the development trajectory and trends is scarce. Therefore, this study summarizes the published information in this field from the Web of Science Core Collection of the last two decades (1999–2018) and uses Citespace to quantitatively visualize the relationship of authors, published countries, organizations, funding sources, and journals and detect the research front by analyzing keywords and burst terms. The results indicate that the studies focused on bioelectrochemical systems for groundwater remediation have had a significant increase during the last two decades, especially in China, Germany and Italy. The national research institutes and universities of the USA and the countries mentioned above dominate the research. Environmental Science &amp; Technology, Applied and Environmental Microbiology, and Water Research are the most published journals in this field. The network maps of the keywords and burst terms suggest that reductive microbial diversity, electron transfer, microbial fuel cell, etc., are the research hotspots in recent years, and studies focused on microbial enrichment culture, energy supply/recovery, combined pollution remediation, etc., should be enhanced in future.</jats:p>

Milena do Prado Ferreira, S. Yamada-Ogatta, César Ricardo Teixeira Tarley

Biosensors • 2023

Rapid transmission and high mortality rates caused by the SARS-CoV-2 virus showed that the best way to fight against the pandemic was through rapid, accurate diagnosis in parallel with vaccination. In this context, several research groups around the world have endeavored to develop new diagnostic methods due to the disadvantages of the gold standard method, reverse transcriptase polymerase chain reaction (RT-PCR), in terms of cost and time consumption. Electrochemical and bioelectrochemical platforms have been important tools for overcoming the limitations of conventional diagnostic platforms, including accuracy, accessibility, portability, and response time. In this review, we report on several electrochemical sensors and biosensors developed for SARS-CoV-2 detection, presenting the concepts, fabrication, advantages, and disadvantages of the different approaches. The focus is devoted to highlighting the recent progress of electrochemical devices developed as next-generation field-deployable analytical tools as well as guiding future researchers in the manufacture of devices for disease diagnosis.

Christopher Moß, Niklas Jarmatz, Janina Heinze et al.

ChemSusChem • 2020

<jats:title>Abstract</jats:title><jats:p>In this study, the performance of electroactive bacteria (EAB), cultivated inside tubular electrode ducts, is systematically investigated to derive predictions on the behavior of EAB under conditions limited by electrochemical losses. A modeling approach is applied to assess the influence of the electrochemical losses on the electrochemical performance and scaling characteristics of complex 3D structures, such as sponges and foams. A modular flow reactor is designed that provides laminar and reproducible flow conditions as a platform for the systematic electrochemical and bioelectrochemical characterization of 3D electrodes in bioelectrochemical systems (BES). The bioelectrochemical experiments are carried out in a set of reactors incorporating cylindrical electrodes exhibiting ducts of 1 cm length and different diameters ranging from 0.1 cm up to 1 cm. Single duct calculations are extrapolated to three dimensions through geometrical considerations; trends in 3D bioanode performance are demonstrated using the resulting simplified 3D structure. The combined experimental and modeling approach constitutes a framework for future studies on systematic electrode design.</jats:p>

S. Ishii, H. Imachi, K. Kawano et al.

Frontiers in Energy Research • 2019

In subsurface anoxic environments, microbial communities generally produce methane as an end-product to consume organic compounds. This metabolic function is a source of biogenic methane in coastal natural gas aquifers, submarine mud volcanoes and methane hydrates. Within the methanogenic communities, hydrogenotrophic methanogens and syntrophic bacteria are converting volatile fatty acids to methane syntrophically via interspecies hydrogen transfer. Recently, direct interspecies electron transfer (DIET) between fermentative/syntrophic bacteria and electrotrophic methanogens has been proposed as an effective interspecies metabolite transfer process to enhance methane production. In this study, in order to stimulate the DIET-associated methanogenic process at deep biosphere-aquifer systems in a natural gas field, we operated a bioelectrochemical system (BES) to apply voltage between an anode and a cathode. Two single-chamber BESs were filled with seawater-based formation water collected from an onshore natural gas well, repeatedly amended with acetate, and operated with 600 mV between electrodes for 21 months, resulting in a successful conversion of acetate to methane via electrical current consumption. One reactor yielded a stable current by ~200 mA/m2 with a coulombic efficiency (CE) of >90%; however, the other reactor, which had been incidentally disconnected for 3 days, showed less electromethanogenic activity with a CE of only ~10%. The 16S rRNA gene-based community analyses showed that two methanogenic archaeal families, Methanocalculaceae and Methanobacteriaceae, were abundant in cathode biofilms that were mainly covered by single-cell-layered biofilm, implicating them as key players in the electromethanogenesis. In contrast, family Methanosaetaceae was abundant at both electrodes and the electrolyte suspension only in the reactor with less electromethanogenesis, suggesting this family was not involved in electromethanogenesis and only activated after the no electron flow event. On anodes covered by thick biofilms with filamentous networks, family Desulfuromonadaceae dominated in the early stage of the operation, while family Geobacteraceae (mainly genus Geoalkalibacter) increased their frequencies during the longer-term operation, which indicates that these families were correlated with electrode-respiring reactions. These results indicate that the BES reactors with voltage application effectively activated a subsurface DIET-related methanogenic microbiome in the natural gas field, and specific electrogenic bacteria and electromethanogenic archaea were identified within the anode and/or cathode biofilms.

Rengasamy Karthikeyan, Rajesh Singh, Arpita Bose

Journal of Industrial Microbiology and Biotechnology • 2019

<jats:title>Abstract</jats:title> <jats:p>Microbial electron uptake (EU) is the biological capacity of microbes to accept electrons from electroconductive solid materials. EU has been leveraged for sustainable bioproduction strategies via microbial electrosynthesis (MES). MES often involves the reduction of carbon dioxide to multi-carbon molecules, with electrons derived from electrodes in a bioelectrochemical system. EU can be indirect or direct. Indirect EU-based MES uses electron mediators to transfer electrons to microbes. Although an excellent initial strategy, indirect EU requires higher electrical energy. In contrast, the direct supply of cathodic electrons to microbes (direct EU) is more sustainable and energy efficient. Nonetheless, low product formation due to low electron transfer rates during direct EU remains a major challenge. Compared to indirect EU, direct EU is less well-studied perhaps due to the more recent discovery of this microbial capability. This mini-review focuses on the recent advances and challenges of direct EU in relation to MES.</jats:p>

Chen Yang, Yiheng Cao, Chuanping Feng

Water • 0

<jats:p>Excessive nitrogen fertilizer use has resulted in growing nitrate contamination of groundwater. In this study, an in situ bioelectrochemical reactor (isBER) reinforced with woodchips was developed for the treatment of actual nitrate-contaminated groundwater. During the 75-day experiment, the denitrification performance, grid permeability, and microbial community structure were investigated under different flow rates and current densities. The reactor achieved a remarkable nitrate removal efficiency of 97.6% ± 0.4% and a rate of 2.09 ± 0.14 mg-N/(L·h). These results were obtained at a temperature of 18.5 ± 0.8 °C, a current density of 350 mA/m2, and a flow rate of 10 cm/d. Notably, the reactor can adapt to a wide flow-rate range of 5~20 cm/d and the operation proceeded smoothly without any blockages. Furthermore, the cathode module demonstrated enrichment of hydrogen autotrophic denitrifying bacteria (Pseudomonas, Stenotrophomonas) and heterotrophic denitrifying bacteria (Brucella, Enterobacteriaceae). Conversely, the anode module exhibited relatively high enrichment levels of aerobic microorganisms and lignin-degrading bacteria (Cellvibrio). The research results can provide novel insights and technical support for in situ remediation of groundwater nitrate contamination.</jats:p>

Raúl Mateos, Raúl Alonso, Adrián Escapa et al.

Materials • 0

<jats:p>The development and practical implementation of bioelectrochemical systems (BES) requires an in-depth characterisation of their components. The electrodes, which are critical elements, are usually built from carbon-based materials due to their high specific surface area, biocompatibility and chemical stability. In this study, a simple methodology to electrochemically characterise carbon-based electrodes has been developed, derived from conventional electrochemical analyses. Combined with classical electrochemical theory and the more innovative fractal geometry approach, our method is aimed at comparing and characterising the performance of carbon electrodes through the determination of the electroactive surface and its fractal dimension. Overall, this methodology provides a quick and easy method for the screening of suitable electrode materials to be implemented in BES.</jats:p>

Bonyoung Koo, S. Jung

Journal of Korean Society of Environmental Engineers • 2022

Currently, gray hydrogen and blue hydrogen are widely recognized as renewable energy, but in reality, they are made from fossil fuels. The most important task to achieve the hydrogen-based society is the development of economic green hydrogen production technology. Microbial electrolysis cell (MEC) is a next-generation energy-producing wastewater treatment technology that treats renewable organic wastewater and simultaneously produces the ultimate green hydrogen. For hydrogen production in MFC, it is necessary to input electrical energy into MEC. However, that energy is all covered by the energy produced by the MEC. Therefore, hydrogen production in MEC can be defined as the ultimate green hydrogen. This review contains an in-depth summary and analysis of the principles and feasibility of MEC technology, the composition and shape of MEC, electrode materials, and practical application cases in various types of wastewaters. Furthermore, compatibility and scalability with other environmental systems were reviewed at the pilot scale. Based on this, the technical limitations of MEC were diagnosed and future research directions for the practical application of MEC technology were suggested.

Kuanchang He, Wei Li, Longxiang Tang et al.

Environmental Science &amp; Technology • 2022

Hydrogen gas (H2) is an attractive fuel carrier due to its high specific enthalpy; moreover, it is a clean source of energy because in the combustion reaction with oxygen (O2) it produces water as the only byproduct. The microbial electrolysis cell (MEC) is a promising technology for producing H2 from simple or complex organics present in wastewater and solid wastes. Methanogens and non-archaeal methane (CH4)-producing microorganisms (NAMPMs) often grow in the MECs and lead to rapid conversion of produced H2 to CH4. Moreover, non-archaeal methane production (NAMP) catalyzed by nitrogenase of photosynthetic bacteria was always overlooked. Thus, suppression of CH4 production is required to enhance H2 yield and production rate. This review comprehensively addresses the principles and current state-of-the-art technologies for suppressing methanogenesis and NAMP in MECs. Noteworthy, specific strategies aimed at the inhibition of methanogenic enzymes and nitrogenase could be a more direct approach than physical and chemical strategies for repressing the growth of methanogenic archaea. In-depth studies on the multiomics of CH4 metabolism can possibly provide insights into sustainable and efficient approaches for suppressing metabolic pathways of methanogenesis and NAMP. The main objective of this review is to highlight key concepts, directions, and challenges related to boosting H2 generation by suppressing CH4 production in MECs. Finally, perspectives are briefly outlined to guide and advance the future direction of MECs for production of high-purity H2 based on genetic and metabolic engineering and on the interspecific interactions.

Yanhui Liu, Xingkun Wang, Bolin Zhao et al.

Chemistry – A European Journal • 2019

Nonprecious-metal-based electrocatalysts with low cost, high activity, and stability are considered as one of the most promising alternatives to Pt-based catalysts for the oxygen reduction reaction (ORR). Herein, an economical and easy-to-fabricate catalyst is developed, that is, Fe/Fe3 C embedded in N-doped hollow carbon spheres (Fe/Fe3 C/NHCS), which gave the half-wave potential of 0.84 V in 0.1 m KOH, similar to the commercial Pt/C catalyst. Surprisingly, the favorable ORR performance of the as-prepared catalyst was obtained in both acidic and neutral conditions with almost a four-electron pathway and low H2 O2 yield, which desirable the development of the proton exchange membrane (PEM) and microbial electrolysis cell (MEC) technology. Additionally, the obtained catalyst demonstrated better long-term stability and high methanol tolerance over a wide range of pH. These features could be mainly attributed to the synergistic effect between Fe/Fe3 C and Fe-Nx sites, the hollow structure with mesopores, and the well-dispersed Fe/Fe3 C nanoparticles owing to the existence of the abundant hydrophilic groups within the HCS precursor. As such, designing an efficient and cheap ORR catalyst that can operate at alkaline, acidic, and neutral solutions is highly desirable, yet challenging.

L. F. Leon-Fernandez, X. Dominguez-Benetton, J. Villaseñor Camacho et al.

Environmental Microbiology Reports • 2023

Abstract This work proves the feasibility of dechlorinating 2,4‐D, a customary commercial herbicide, using cathodic electrocatalysis driven by the anodic microbial electrooxidation of sodium acetate. A set of microbial electrochemical systems (MES) were run under two different operating modes, namely microbial fuel cell (MFC) mode, with an external resistance of 120 Ω, or microbial electrolysis cell (MEC) mode, by supplying external voltage (0.6 V) for promoting the (bio)electrochemical reactions taking place. When operating the MES as an MFC, 32% dechlorination was obtained after 72 h of treatment, which was further enhanced by working under MEC mode and achieving a 79% dechlorination. In addition, the biodegradability (expressed as the ratio BOD/COD) of the synthetic polluted wastewater was tested prior and after the MES treatment, which was improved from negative values (corresponding to toxic effluents) up to 0.135 in the MFC and 0.453 in the MEC. Our MES approach proves to be a favourable option from the point of view of energy consumption. Running the system under MFC mode allowed to co‐generate energy along the dechlorination process (−0.0120 kWh mol−1), even though low removal rates were attained. The energy input under MEC operation was 1.03 kWh mol−1—a competitive value compared to previous works reported in the literature for (non‐biological) electrochemical reactors for 2,4‐D electrodechlorination.

G. Antonopoulou, Ilias Apostolopoulos, George Bampos et al.

Global NEST International Conference on Environmental Science &amp; Technology • 0

In the present study two identical two-chamber microbial electrolysis cells (MECs), fed with an acetate synthetic medium, were used for hydrogen production, using different anodic materials, i.e. commercial carbon fiber paper (CP) and graphite granules (GG). The effects of the applied voltage (i.e. 0.7 and 0.9 V) and of the acclimation procedure (direct potentiostatic operation as MEC or galvanostatic as microbial fuel cell, MFC) were assessed and the performance of both MECs was compared in terms of their biochemical and electrochemical characteristics.

Nuzahat Habibul, Y. Hu, Yunkun Wang et al.

Environmental Science &amp; Technology • 2016

Plant-microbial fuel cell (PMFC) is a renewable and sustainable energy technology that generates electricity with living plants. However, little information is available regarding the application of PMFC for the remediation of heavy metal contaminated water or soil. In this study, the potential for the removal of heavy metal Cr(VI) using PMFC was evaluated, and the performance of the PMFC at various initial Cr(VI) contents was investigated. The Cr(VI) removal efficiency could reached 99% under various conditions. Both the Cr(VI) removal rates and the removal efficiencies increased with the increasing initial Cr(VI) concentration. Furthermore, the long-term operation of the PMFC indicated that the system was stable and sustainable for Cr(VI) removal. The mass balance results and XPS analysis results demonstrate that only a small amount of soluble Cr(III) remained in the PMFC and that most Cr(III) precipitated in the form of the Cr(OH)3(s) or was adsorbed onto the electrodes. The PMFC experiments of without acetate addition also show that plants can provide carbon source for MFC through secrete root exudates and bioelectrochemical reduction of Cr(VI) was the main mechanism for the Cr(VI) removal. These results extend the application fields of PMFC and might provide a new insight for Cr(VI) removal from wastewater or soil.

Mirna Valdez-Hernández, L. N. Acquaroli, J. Vázquez-Castillo et al.

Energy Sources, Part A: Recovery, Utilization, and Environmental Effects • 2022

ABSTRACT Plant and soil microbial fuel cells (PMFCs and SMFCs, respectively) are bioelectrochemical systems that produce energy using microorganisms as catalysts. This energy can be harvested; however, its impact on biological activity has seldom been explored. To reveal the main characteristics of this impact, we monitored four experimental designs for 20 days under open-sky conditions. The effect of PMFC/SMFC start-up on metabolism was evaluated by photosynthesis of Codiaeum variegatum and heterotrophic soil respiration to determine the short-term effects. To compare the results, a normalized parameter of power density, which considered the PMFC/SMFC configurations, solar irradiance, and soil temperature, was introduced. The highest energy was obtained for the PMFC configuration. The energy harvesting stimulated the photosynthetic rate of C. variegatum up to two times with respect to its normal values, while the heterotrophic soil respiration decreased 30%. Thus, in the PMFC and SMFC start-up operations, the increase in soil temperature due to energy harvesting suggests that soil temperature is the most relevant parameter influencing plant metabolism and energy generation. These results open a new pathway for understanding the bioregulation of plants/soil when subjected to energy harvesting.

Till Siepenkoetter, Urszula Salaj‐Kosla, Xinxin Xiao et al.

Electroanalysis • 2016

<jats:title>Abstract</jats:title><jats:p>Nanoporous gold (NPG) fabricated by sputtering is a material of versatile morphology with pores whose size can be tailored to accommodate enzymes. The process of pore formation and the size of the pores in NPG are influenced by the composition of Au and Ag in the alloy used to prepare the electrodes together with the temperature and time period of the dealloying process. On increasing the time from 1 to 60 min and the temperature from 0.5 °C to 60.5 °C in concentrated HNO<jats:sub>3</jats:sub>, significant increases in the average pore diameters from 4.4 to 78 nm were observed with simultaneous decreases in the roughness factor (R<jats:sub>f</jats:sub>). The pores of NPG were fully addressable regardless of the diameter, with R<jats:sub>f</jats:sub> increasing linearly up to an alloy thickness of 500 nm. The influence of the pore size on the bioelectrochemical response of redox proteins was evaluated using cytochrome c as a model system. The highest current densities of <jats:italic>ca</jats:italic>. 30 µA cm<jats:sup>−2</jats:sup> were observed at cytochrome c modified NPG electrodes with an average pore size of ca. 10 nm. The pores in NPG were also tuned for the mediatorless immobilization of <jats:italic>Myrothecium verrucaria</jats:italic> bilirubin oxidase. High current densities of <jats:italic>ca</jats:italic>. 65 µA cm<jats:sup>−2</jats:sup> were observed at <jats:italic>Mv</jats:italic>BOD modified NPG electrodes prepared by dealloying at 0.5 °C for 5 min with an average pore size of 8 nm, which is too small to accommodate the enzyme into the pores, indicating that the response was from enzyme adsorbed on the electrode surface.</jats:p>

Daniel D. Leicester, Jaime M. Amezaga, Andrew Moore et al.

Molecules • 0

<jats:p>Bioelectrochemical systems (BES) have the potential to deliver energy-neutral wastewater treatment. Pilot-scale tests have proven that they can operate at low temperatures with real wastewaters. However, volumetric treatment rates (VTRs) have been low, reducing the ability for this technology to compete with activated sludge (AS). This paper describes a pilot-scale microbial electrolysis cell (MEC) operated in continuous flow for 6 months. The reactor was fed return sludge liquor, the concentrated filtrate of anaerobic digestion sludge that has a high chemical oxygen demand (COD). The use of a wastewater with increased soluble organics, along with optimisation of the hydraulic retention time (HRT), resulted in the highest VTR achieved by a pilot-scale MEC treating real wastewater. Peak HRT was 0.5-days, resulting in an average VTR of 3.82 kgCOD/m3∙day and a 55% COD removal efficiency. Finally, using the data obtained, a direct analysis of the potential savings from the reduced loading on AS was then made. Theoretical calculation of the required tank size, with the estimated costs and savings, indicates that the use of an MEC as a return sludge liquor pre-treatment technique could result in an industrially viable system.</jats:p>

Begüm Şen-Doğan, Meltem Okan, Nilüfer Afşar-Erkal et al.

Micromachines • 0

<jats:p>Microbial Fuel Cells (MFCs) are biological fuel cells based on the oxidation of fuels by electrogenic bacteria to generate an electric current in electrochemical cells. There are several methods that can be employed to improve their performance. In this study, the effects of gold surface modification with different thiol molecules were investigated for their implementation as anode electrodes in micro-scale MFCs (µMFCs). Several double-chamber µMFCs with 10.4 µL anode and cathode chambers were fabricated using silicon-microelectromechanical systems (MEMS) fabrication technology. µMFC systems assembled with modified gold anodes were operated under anaerobic conditions with the continuous feeding of anolyte and catholyte to compare the effect of different thiol molecules on the biofilm formation of Shewanella oneidensis MR-1. Performances were evaluated using polarization curves, Electrochemical Impedance Spectroscopy (EIS), and Scanning Electron Microcopy (SEM). The results showed that µMFCs modified with thiol self-assembled monolayers (SAMs) (cysteamine and 11-MUA) resulted in more than a 50% reduction in start-up times due to better bacterial attachment on the anode surface. Both 11-MUA and cysteamine modifications resulted in dense biofilms, as observed in SEM images. The power output was found to be similar in cysteamine-modified and bare gold µMFCs. The power and current densities obtained in this study were comparable to those reported in similar studies in the literature.</jats:p>

Jiang-Hao Tian, Rémy Lacroix, Asim Ali Yaqoob et al.

Energies • 0

<jats:p>Microbial electrochemical technologies now enable microbial electrosynthesis (MES) of organic compounds using microbial electrolysis cells handling waste organic materials. An electrolytic cell with an MES cathode may generate soluble organic molecules at a higher market price than biomethane, thereby satisfying both economic and environmental goals. However, the long-term viability of bioanode activity might become a major concern. In this work, a 15-L MES reactor was designed with specific electrode configurations. An electrochemical model was established to assess the feasibility and possible performance of the design, considering the aging of the bioanode. The reactor was then constructed and tested for performance as well as a bioanode regeneration assay. Biowaste from an industrial deconditioning platform was used as a substrate for bioanode. The chemical oxygen demand (COD) removal rate in the anodic chamber reached 0.83 g day−1 L−1 of anolyte. Acetate was produced with a rate of 0.53 g day−1 L−1 of catholyte, reaching a maximum concentration of 8.3 g L−1. A potential difference (from 0.6 to 1.2 V) was applied between the bioanode and biocathode independent of reference electrodes. The active biocathode was dominated by members of the genus Pseudomonas, rarely reported so far for MES activity.</jats:p>

Reyhaneh Yousefi, Mohammad Mahdi Mardanpour, Soheila Yaghmaei

Scientific Reports • 0

<jats:title>Abstract</jats:title><jats:p>This study presented the fabrication of macro and micro-scale microbial fuel cells (MFCs) to generate bioelectricity from oxalate solution and monitor the biodegradation in a micro-scale MFC for the first time. The maximum generated power density of 44.16 W m<jats:sup>−3</jats:sup> in the micro-scale MFC elucidated its application as a micro-sized power generator for implantable medical devices (IMDs). It is also worthwhile noting that for the macro-scale MFC, the significant amounts of open circuit voltage, oxalate removal, and coulombic efficiency were about 935 mV, 99%, and 44.2%, respectively. These values compared to previously published studies indicate successful oxalate biodegradation in the macro-scale MFC. Regarding critical challenges to determine the substrate concentration in microfluidic outlets, sample collection in a suitable time and online data reporting, an analogy was made between macro and micro-scale MFCs to elicit correlations defining the output current density as the inlet and the outlet oxalate concentration. Another use of the system as an IMD is to be a platform to identify urolithiasis and hyperoxaluria diseases. As a versatile device for power generation and oxalate biodegradation monitoring, the use of facile and cheap materials (&lt; $1.5 per device) and utilization of human excreta are exceptional features of the manufactured micro-scale MFC.</jats:p>

R. Ivanov, P. Genova

Sustainable Extraction and Processing of Raw Materials • 2023

Sediment microbial fuel cells (SMFCs) are bio-electrochemical systems in which the anode is placed in the anaerobic sediment and the cathode is immersed in the surface layer of water. Natural exoelectrogenic bacteria decompose organic compounds in sediment, producing electrons and protons. The electrons reach the cathode through an external electrical circuit, while the protons pass through the soil layer, which acts as a kind of membrane. Oxygen is in many cases the preferred electron acceptor due to its presence in the cathode region and its high potential. Heavy metal ions and other compounds can also be reduced on the cathode, which will increase the energy generated. Based on the above characteristics, SMFCs would be suitable for application as biosensors for monitoring water pollution with heavy metals. In the present study, the possibility of application of SMFCs as biosensors for water pollution with copper has been studied. A high correlation was found between the concentration of copper ions in the range 0,1 – 100 mg/L and the voltage generated by SMFC. The constructed SMFC based biosensor showed wider detection limits for copper compared to other authors' studies as the coefficient of determination reached 0,9911. Native exoelectrogenic bacteria were represented mainly by Geobacter, Clostridium, Anaeromixobacter and Bacillus.

Yangming Lei, M. Du, P. Kuntke et al.

ACS Sustainable Chemistry &amp; Engineering • 2019

Phosphorus (P) removal and recovery from waste streams is essential for a sustainable world. Here, we updated a previously developed abiotic electrochemical P recovery system to a bioelectrochemical system. The anode was inoculated with electroactive bacteria (electricigens) which are capable of oxidizing soluble organic substrates and releasing electrons. These electrons are then used for the reduction of water at the cathode, resulting in an increase of pH close to the cathode. Hence, phosphate can be removed with coexisting calcium ions as calcium phosphate at the surface of the cathode with a much lower energy input. Depending on the available substrate (sodium acetate) concentration, an average current density from 1.1 ± 0.1 to 6.6 ± 0.4 A/m 2 was achieved. This resulted in a P removal of 20.1 ± 1.5% to 73.9 ± 3.7%, a Ca removal of 10.5 ± 0.6% to 44.3 ± 1.7% and a Mg removal of 2.7 ± 1.9% to 16.3 ± 3.0%. The specific energy consumption and the purity of the solids were limited by the relative low P concentration (0.23 mM) in the domestic wastewater. The relative abundance of calcium phosphate in the recovered product increased from 23% to 66% and the energy consumption for recovery was decreased from 224 ± 7 kWh/kg P to just 56 ± 6 kWh/kg P when treating wastewater with higher P concentration (0.76 mM). An even lower energy demand of 21 ± 2 kWh/kg P was obtained with a platinized cathode. This highlights the promising potential of bioelectrochemical P recovery from P-rich waste streams.

Vibeke B. Karlsen, Carlos Dinamarca

Reviews in Environmental Science and Bio/Technology • 2024

<jats:title>Abstract</jats:title><jats:p>The increased demand for energy worldwide and the focus on the green shift have raised interest in renewable energy sources such as biogas. During biogas production, sulphide (H<jats:sub>2</jats:sub>S, HS<jats:sup>−</jats:sup> and S<jats:sup>2−</jats:sup>) is generated as a byproduct. Due to its corrosive, toxic, odorous, and inhibitory nature, sulphide is problematic in various industrial processes. Therefore, several techniques have been developed to remove sulphide from liquid and gaseous streams, including chemical absorption, chemical dosing, bioscrubbers, and biological oxidation. This review aims to elucidate electrochemical and bioelectrochemical sulphide removal methods, which are gaining increasing interest as possible supplements to existing technologies. In these systems, the sulphide oxidation rate is affected by the reactor design and operational parameters, including electrode materials, anodic potential, pH, temperature and conductivity. Anodic and bioanodic materials are highlighted here, focusing on recent material developments and surface modification techniques. Moreover, the review focuses on sulphide generation and inhibition in biogas production processes and introduces the prospect of removing sulphide and producing methane in one single bioelectrochemical reactor. This could introduce BESs for combined biogas upgrading and cleaning, thereby increasing the methane content and removing pollutants such as sulphide and ammonia in one unit.</jats:p>

Honghong Yuan, Yumeng Huang, Ouyuan Jiang et al.

Frontiers in Microbiology • 0

<jats:p>Arsenate [As(V)] is a toxic metalloid and has been observed at high concentrations in groundwater globally. In this study, a bioelectrochemical system (BES) was used to efficiently remove As(V) from groundwater, and the mechanisms involved were systematically investigated. Our results showed that As(V) can be efficiently removed in the BES cathode chamber. When a constant cell current of 30 mA (<jats:italic>I</jats:italic><jats:sub><jats:italic>cell</jats:italic></jats:sub>, volume current density = 66.7 A/m<jats:sup>3</jats:sup>) was applied, 90 ± 3% of total As was removed at neutral pH (7.20–7.50). However, when <jats:italic>I</jats:italic><jats:sub><jats:italic>cell</jats:italic></jats:sub> was absent, the total As in the effluent, mainly As(V), had increased approximately 2–3 times of the As(V) in influent. In the abiotic control reactor, under the same condition, no significant total As or As(V) removal was observed. These results suggest that As(V) removal was mainly ascribed to microbial electrosorption of As(V) in sludge. Moreover, part of As(V) was bioelectrochemically reduced to As(III), and sulfate was also reduced to sulfides [S(–II)] in sludge. The XANES results revealed that the produced As(III) reacted with S(–II) to form As<jats:sub>2</jats:sub>S<jats:sub>3</jats:sub>, and the residual As(III) was microbially electroadsorbed in sludge. This BES-based technology requires no organic or chemical additive and has a high As(V) removal efficiency, making it an environment-friendly technique for the remediation of As-contaminated groundwater.</jats:p>