Biochar Electrodes Research Articles

Sustainable capacitive deionization process for enhanced chromium reclamation using functionalized biochar electrode

Water pollution, driven by urbanization and industrial growth, poses a significant threat, with chromium (Cr(VI)) discharge from industries like electroplating and tanneries. To address this issue, capacitive deionization (CDI) is explored for its low energy consumption and efficient removal of ionic contaminants. However, CDI faces challenges related to electrode costs and internal resistance. So, it is necessary to find a low-cost sustainable, functional electrode for the hazardous Cr(VI) reclamation without conventional additives to prevent internal resistance. Industrial Biochar, a product of pyrolysis enriched with carbon content, replaces conventional activated carbon and possesses better physicochemical properties. Similarly, Chitosan is a natural derived functional material enriched with functional groups that can adsorb the Cr(VI) ions. Apart from their functionality, they also improve the electrochemical stability and capacitance of the electrode. In response, the present study focuses on developing cost-effective functional electrodes using a biochar/chitosan (BC-CS) composite. The utilization of the chitosan enriches the physico-electrochemical properties and replaces the requirement of binder for the electrode development. The crosslinked BC-CS composite demonstrates a three-fold increase in specific capacitance compared to biochar electrode. Optimizing the ratio, the 1:1 BC-CS composite achieves a remarkable 96.7% chromium removal from a 100 ppm Cr(VI) solution in 3 h at 2 V. The composite also exhibits promising regeneration capabilities and shows potential in treating real-time chrome wash effluent from electroplating industries, indicating its viability for chromium water reclamation.

KOH Activated Walnut Shell Biochar Electrode of Capacitive Deionization and Its Desalination Performance

Abstract The flake biochar electrode materials with fast ion transport function were prepared by KOH activation walnut shell used as raw material. The effects of carbonization temperature and KOH-to-biochar ratio were systematically evaluated using physicochemical characterization and electrochemical performance testing. The optimized walnut shell biochar (WSC800-2), produced at 800℃ with a KOH-to-biochar ration of 2∶1, exhibited an exceptional specific surface area (2,287 m2 g-1), the highest porosity (0.824 cm3 g-1), and an excellent specific capacitance (369.51 F g-1, 10 mV s-1). Furthermore, in desalination experiments, WSC800-2 achieved a high salt adsorption capacity of 15.70 mg g-1 at 1.2V, 500 mg L-1 NaCl solution. The electrode also exhibited outstanding cycling stability, retaining 97.0% of its performance after 10 adsorption/desorption cycles. These findings highlight the potential of walnut shell-derived biochar as an effective material for capacitive deionization and future desalination technologies.

Glycerol conversion and power generation in microbial fuel cells: insect exuviae biochar as electrodes and insect frass as biostimulants

Abstract Insects are a suitable raw material for refinement into biodiesel owing to their high fat content, but the refining process produces large amounts of insect waste and glycerol as a byproduct. Biochar electrodes were produced from insect waste for application in microbial fuel cells (MFCs), and experiments were performed to evaluate the electrochemical performance and glycerol conversion efficiency. The biochar was characterized by rich functional groups (O–H, O=C=O, C=C, C=O) and high microporosity, which favored the colonization of microbes. Among the electrode configurations considered, the optimal configuration was a biochar anode and carbon cloth cathode (B-MFC), showing the highest glycerol conversion efficiency (>95%). The B-MFC also exhibited the highest power density (122.3 mA/m3), 1.46-2.34 times that of the other MFCs tested. Adding Nitrogen-rich insect frass to the anode tank further stimulated microbial growth and increased power production, with the highest voltage output of 443.2 mV at 10 mg/L nitrogen concentration, 1.18 times higher than without addition. This study is the first to utilize insect exuviae as biochar electrodes in an MFC to solve the problems of excessive insect waste from biodiesel refinement and converting glycerol into a renewable energy source.

Opportunities and Threats for Supercapacitor Technology Based on Biochar—A Review

This review analyzes in detail the topic of supercapacitors based on biochar technologies, including their advantages, disadvantages, and development potential. The main topic is the formation of precursors in the process of pyrolysis and activation, and the possibility of the application of biochar itself in various fields is brought closer. The structure, division, and principle of operation of supercondensates are discussed, where their good and bad sides are pointed out. The current state of the scientific and legal knowledge on the topic of biocarbon and its applications is verified, and the results of many authors are compared to examine the current level of the research on supercapacitors based on biochar electrodes created from lignocellulosic biomass. Current application sites for supercapacitors in transportation, electronics, and power generation (conventional and unconventional) are also examined, as is the potential for further development of the technology under discussion.

A biochar electrode based on conductive straw for Cd removal and recovery from wastewater by DC electrochemical deposition

Biomass-derived charcoal, possessing high surface area, temperature resistance, and stability, has diverse applications. Traditional methods overlook its conductivity. In this work, a new approach was devised. By controlling the pyrolysis temperature and preparation atmosphere, rice straw was converted into biochar electrodes at 1000 °C in a N₂-containing environment. The temperature effect on the conductivity of biochar made from rice straw was elucidated through methods such as resistivity measurement, XRD, and Raman spectroscopy. Furthermore, the biochar electrode material was employed as the cathode and the electro-deposition method was employed to treat wastewater containing Cd. The results indicated that the treatment efficiency of simulated Cd wastewater can reach a maximum of 88.96 % in 7 h at relatively low power consumption. After the reaction, a simple acid washing step effectively separated the electrode and Cd, which allowed the Cd to be recovered and the electrode to be used again. This method offers a innovative low-cost, high-efficiency technique for preparing biochar electrodes from rice straw, achieving sustainable waste conversion while providing new techniques and novel solutions for electro-deposition in heavy metal wastewater treatment. Therefore, the research hold significant practical a significance and scientific value.

Machine learning modeling of the capacitive performance of N-doped porous biochar electrodes with experimental verification

N-doped porous biochar is considered as a promising carbon material for supercapacitor electrodes application. However, the intrinsic relations and effect mechanisms of the pore structure and N-doping to the capacitive performance are still inscrutable, giving rise to the challenges for enhancing the capacitive performance by regulating the physicochemical properties of N-doped biochar. In this study, various machine learning models were established to predict the specific capacitance of N-doped biochar electrodes based on the pore structure and N-doping properties. The effect mechanisms of pore structure and N-doping to the specific capacitance were also explored. Results showed that Random Forest model predicted the specific capacitance most accurately. The generalization performance of the model was verified to be quite well with our experiments. It is suggested that developing pore structure with abundant micropores plays more important role than N-doping in enhancing the specific capacitance. The optimal interval of each physiochemical property of N-doped biochar were also determined to maximize the specific capacitance. Furthermore, synergistic effects of pore structure and N-doping to the specific capacitance were revealed. This study provides a useful guideline for N-doped porous biochar production with the aim of capacitive performance enhancement.

Straw-derived macroporous biochar as high-performance anode in microbial fuel cells

Large-scale application of MFCs is limited by the high cost of electrode and low power density. In this study, the electrochemical structure and power output performance of three novel straw-derived biochar are discussed and characterized by scanning electron microscope, specific surface area, cyclic voltammetry, Raman spectrum, electrochemical impedance spectroscopy etc. Compared with the common carbon felt electrode, the optimal electricity generation ability and electrochemical affinity are obtained in corn straw biochar electrode: the rough surface with macroporous structure and high degree of graphitization facilitates the attachment of electroactive bacteria; the maximum output voltage, open circuit voltage, power density and coulombic efficiency reach 662.64±4.03 mV, 798.24±3.65 mV, 1.54±0.18 W m−2 and 50.39±1.68 %, respectively; the maximum COD removal efficiency of 77.45±1.69 % is achieved; exchange current density (4.6142×10−4 A cm−2) in corn straw electrode presents the better electrochemical activity than that of carbon felt electrode. These implies that corn straw-derived biochar is a competitive raw material for MFC anode.

Multi-walled carbon nanotubes modified corn straw biochar as high-performance anode in microbial fuel cells

In this study, the feasibility of multi-walled carbon nanotubes in modifying corn straw biochar electrode and the subsequent enhancement in electrical conductivity of the modified electrode and reactor performance were investigated in this study. The Layer-by-Layer self-assembly method was used as the modification method. The electrochemical activity, power output capacity and pollutant removal performance of the Microbial fuel cell with modified corn straw biochar anode. The characterization techniques included scanning electron microscope, electrochemical impedance spectroscopy, Tafel analysis and polarization curve. The successful adhesion of multi-walled carbon nanotubes onto the surface of corn straw biochar was revealed by scanning electron microscope analysis. The microbial fuel cell with multi-walled carbon nanotubes modified corn straw biochar anode achieved the lowest solution resistance of 9.86 Ω and charge transfer resistance of 3.56 Ω. Compared with the MFC with unmodified electrode, power density (2.68 W m−2) and coulombic efficiency (70.52 %) were demonstrated to increase by 58.6 % and 24.6 % in the MFC with modified electrode, respectively.

Exploring the mechanism of removing Cd from polluted soil using electrochemical leaching with straw carbon film electrode

The study presents a novel approach to remediating heavy metal-contaminated soil using electrochemical technology and chemical leaching. The researchers developed a new electrode material from waste straw and an environmentally friendly leaching agent using straw fermentation liquid. Combining electrochemical technology with chemical leaching provides a powerful remediation solution for heavy metal-contaminated soil, demonstrating efficiency and thoroughness. However, challenges include developing recyclable electrode materials and environmentally friendly leaching agents. This study addresses these challenges by pioneering a biochar-based electrode material and an eco-friendly leaching agent. Waste straw undergoes pyrolysis at 1000 °C to produce a conductive biochar, which is then combined with ethyl cellulose to form a film, creating biochar electrode materials. The developed straw fermentation solution, an environmentally friendly leaching agent, is used for Cd-contaminated soil remediation through combined electrochemical-chemical leaching. Results show soil Cd removal efficiency peaking at 59.5% with a singular chemical leaching agent. The combined method increases the Cd removal rate to a maximum of 91%. Furthermore, the study elucidate the potential mechanism of cadmium removal through techniques such as XRD, SEM, and infrared spectroscopy. To evaluate the efficacy of our approach, the study conducted Chinese cabbage pot-cultivation experiments. Remarkably, the physicochemical properties of soil remained largely unchanged after the reaction, while Chinese cabbage growth in treated soil surpassed that of the control group. This study not only removes Cd from the soil, reducing secondary pollution, but also establishes electrode recyclability, offering a prospective solution for large-scale soil heavy metal pollution remediation.

Study on the performance of biochar prepared from walnut shell and traditional graphene electrode plate in the treatment of domestic sewage in microbial fuel cells.

As a new pollutant treatment technology, microbial fuel cell (MFC) has a broad prospect. In this article, the devices assembled using walnut shells are named biochar-microbial fuel cell (B-MFC), and the devices assembled using graphene are named graphene-microbial fuel cell (G-MFC). Under the condition of an external resistance of 1,000 Ω, the B-MFC with biochar as the electrode plate can generate a voltage of up to 75.26 mV. The maximum power density is 76.61 mW/m2, and the total internal resistance is 3,117.09 Ω. The removal efficiency of B-MFC for ammonia nitrogen (NH3-N), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) was higher than that of G-MFC. The results of microbial analysis showed that there was more operational taxonomic unit (OTU) on the walnut shell biochar electrode plate. The final analysis of the two electrode materials using BET specific surface area testing method (BET) and scanning electron microscope (SEM) showed that the pore size of walnut shell biochar was smaller, the specific surface area was larger, and the pore distribution was smoother. The results show that using walnut shells to make electrode plates is an optional waste recycling method and an electrode plate with excellent development prospects.

Graphite-N reinforced sludge biochar electrode: A experimental and DFT theoretical analysis of efficient evolution and in-situ utilization of H2O2

Rational reuse of municipal sludge to produce electro-Fenton electrode can not only save resources, but also produce superior peroxide and degradation pollutants simultaneously. Herein, a novel electro-Fenton electrode derived from sludge biochar loaded on Ni foam (SBC@Ni) was constructed via high temperature pyrolysis and chemical coating for efficient H2O2 evolution and pollutant degradation. Systematic experiments and density functional theory calculations (DFT calculation) explained that the production of graphite C and graphite N during high-temperature pyrolysis of municipal sludge can greatly enhance the oxygen reduction reaction of SBC@Ni electrode and promote the evolution of H2O2. And the hybrid heterojunctions, such as FeP, also played a key role in electrocatalytic processes. Notably, the electrode still exhibited excellent performance after 1000 linear scans and 12 h of continuous current stimulation, which demonstrated the excellent stability of the electrode. Moreover, SBC@Ni electrode can not only effectively oxidize 4-chlorophenol through the electro-Fenton effect, but also fully mineralize organic matter, indicating promising environmental application. The free radical quenching experiment also revealed that the ·OH is the main active species for 4-CP degradation in SBC@Ni electro-Fenton system.

Capacitive deionization chloride and fluoride removal by amine and titania-modified biochar electrodes

Capacitive deionization chloride and fluoride removal by amine and titania-modified biochar electrodes

Packing blockage and power generation of constructed wetland coupled microbial fuel cell systems using biochar as electrode and filler with different ratios

This article investigated the electrochemical performance, water purification capacity and packing clogging of constructed wetland-microbial fuel cells coupled reactors (CW-MFCs). The CW-MFCs-B (B = 100 % biochar filler) reactor performed the best under intermittent conditions, with a power density of up to 33.7 mW/m2. Regarding TOC removal, CW-MFCs-G (G = no biochar filler) was the least effective when the system was in continuous flow. The effect of the other two reactors with biochar filler addition (BG = 50 % and B = 100 %) was similar, indicating that the biochar functioned well as the CW filler to remove organic matter. Regarding NH4+-N removal, removal rates varied at different HRTs: HRT = 2 days > intermittent flow > HRT = 0.5 days. Among them, CW-MFCs-B was the most effective, with a maximum of 65.10 %. The clogging index Φb of the three reactors were 2.83 (B), 1.77 (BG), and 0.72 (G). The CW-MFCs-B reactor showed good effluent treatment and had the best electricity production but the most severe clogging. There may be a certain connection between H2O2 concentration and the degree of CW clogging. CW-MFC with biochar electrode and gravel filler may be suitable for long-term operation.

Simultaneous removal of sulfamethazine and sulfate via electrochemical oxidation and capacitive Deionization: Mechanisms of in-situ activation and strategies of the hybrid system

Electrochemical oxidation (EO) is a well-established method for pollutants removal. However, excessive addition of oxidant during EO may cause secondary pollution. Moreover, the unprocessed ions in the wastewater can cause further contamination. This research introduces a hybrid process that combines EO with capacitive deionization (CDI), in situ catalytically utilizing sulfate (SO42-) and removing sulfamethazine (SMZ). This process realized by layered porous MXene-modified biochar electrodes (BCM) that demonstrate electrocatalytic and adsorption properties. The electrochemical oxidation system, constructed using BCM cathode and boron-doped diamond anode, harnesses in situ generation of oxidants from SO42-, leading to the complete degradation of 30 mg/L sulfamethazine in 30 min through adsorbed radicals and metastable active species at the biphasic interface. Subsequently, the BCM-2 exhibits excellent CDI performance at 1.2 V, achieving a desalination capacity of 15.40–65.97 mg/g in 100–1000 mg/L Na2SO4 solution. By combining EO with CDI, BCM simultaneously removes sulfamethazine and sulfate, resulting in a 60 % reduction in total organic carbon and a 14.4 % decrease in electrical conductivity after one process cycle. Moreover, BCM exhibits favorable cytocompatibility.

Sludge dewaterability improvement with microbial fuel cell powered electro-Fenton system (MFCⓅEFs): Performance and mechanisms

Throughout the entire process of sludge treatment and disposal, it is crucial to explore stable and efficient techniques to improve sludge dewaterability, which can facilitate subsequent resource utilization and space and cost savings. Traditional Fenton oxidation has been widely researched to enhance the performance of sludge dewaterability, which was limited by the additional energy input and the instabilities of Fe2+ and H2O2. To reduce the consumption of energy and chemicals and further break the rate-limiting step of the iron cycle, a novel and feasible method that constructed microbial fuel cell powered electro-Fenton systems (MFCⓅEFs) with ferrite and biochar electrode (MgFe2O4@BC/CF) was successfully demonstrated. The MFCⓅEFs with MgFe2O4@BC/CF electrode achieved specific resistance filtration and sludge cake water content of 2.52 × 1012 m/kg and 66.54 %. Cellular structure and extracellular polymeric substances (EPS) were disrupted, releasing partially bound water and destroying hydrophilic structures to facilitate sludge flocs aggregation, which was attributed to the oxidation of hydroxyl radicals. The consistent electron supply supplied by MFCⓅEFs and catalytically active sites on the surface of the multifunctional functional group electrode was responsible for producing more hydroxyl radicals and possessing a better oxidizing ability. The study provided an innovative process for sludge dewaterability improvement with high efficiency and low energy consumption, which presented new insights into the green treatment of sludge.

Selective Capacitive Removal of Pb2+ from Wastewater over Biochar Electrodes by Zinc Regulation.

Biochar materials have shown great potential for broad catalytic application. However, using these materials in the capacitive deionization technology (CDI) system for heavy metal removal still faces a significant challenge due to their low specific capacity and removal capability. Here, a comprehensive regulation on the interfacial/bulk electrochemistry of biochar by Zn doping is reported, which suggests a high renewable capacity (20mgg-1) and outstanding selective capacitive removal ability (SCR) of Pb2+ from leachate. The SCR efficiency of Pb2+ is as high as 99% compared to K+ (8%), Na+ (13%), and Cd2+ (37%). This work proves that the doped Zn on the biochar can combine with OH- generated by water splitting to form M─OH bonds, which is beneficial for improving the specific capacity. Significantly, the relationship between double-layer capacitance and pseudo-capacitance can also be optimized by regulating the content of Zn, leading to different removal abilities of heavy metals. Therefore, this work offers insights into charge-storage kinetics, which provide valuable guidelines for designing and optimizing the biochar electrode for broader environmental applications.

Naturally manufactured biochar materials based sensor electrode for the electrochemical detection of polystyrene microplastics

In recent times, microplastics have become a disturbance to both aquatic and terrestrial ecosystems and the ingestion of these particles can have severe consequences for wildlife, aquatic organisms, and even humans. In this study, two types of biochars were manufactured through the carbonization of naturally found starfish (SF-1) and aloevera (AL-1). The produced biochars were utilized as sensing electrode materials for the electrochemical detection of ∼100 nm polystyrene microplastics (PS). SF-1 and AL-1 based biochars were thoroughly analyzed in terms of morphology, structure, and composition. The detection of microplastics over biochar based electrodes was carried out by electrochemical studies. From electrochemical results, SF-1 based electrode exhibited the detection efficiency of ∼0.2562 μA/μM∙cm2 with detection limit of ∼0.44 nM whereas, a high detection efficiency of ∼3.263 μA/μM∙cm2 was shown by AL-1 based electrode and detection limit of ∼0.52 nM for PS (100 nm) microplastics. Process contributed to enhancing the sensitivity of AL-1 based electrode might associate to the presence of metal-carbon framework over biochar's surfaces. The AL-1 biochar electrode demonstrated excellent repeatability and detection stability for PS microplastics, suggesting the promising potential of AL-1 biochar for electrochemical microplastics detection.

Hydrothermal synthesis and electrochemical properties of Sn-based peanut shell biochar electrode materials.

Using activated-carbon-based electrodes derived from waste biomass in super-capacitor energy technologies is an essential future strategy to achieve sustainable energy and environmental protection. Biomass feed-stocks such as bamboo and straw have been used to prepare activated carbon-based electrodes. This experiment used peanut shells (waste biomass) as carbon precursors. Peanut shell-activated biochar materials were prepared using KOH activation and heat treatment, and SnO2@KBC-CNTs, a composite electrode material of biochar loaded with tin oxide. It was produced through hydrothermal synthesis, utilizing SnCl4-5H2O as the tin precursor. The application of KOH activators during pyrolysis markedly enhanced the porosity and specific surface area of the resultant activated biochar, due to effective dispersion and degradation of pyrolytic products. Characterized by a micro-mesoporous structure, the composite's pores boasted a specific surface area of 158.69 m2 g-1. When tested at a density of current of 0.5 A g-1, the specific capacitance of SnO2@KBC-CNTs reached 198.62 F g-1, nearly doubling the performance of the KBC electrode material alone. Moreover, the composite demonstrated a low ion transfer resistance of 0.71 Ω during charge-discharge cycles.

Development of biochar electrode materials for capacitive deionization: Preparation, performance, regeneration and other challenges

Development of biochar electrode materials for capacitive deionization: Preparation, performance, regeneration and other challenges

Improving electro-fenton degradation performance using waste biomass-derived-modified biochar electrodes: A real environment textile water treatment

In this study, catalytically efficient biochar electrodes were obtained by pyrolysis and thermal modification from waste biomass. The effect of the gas type, temperature and time on the thermal modification was investigated in the designed Electro-Fenton system. Firstly, the most effective biochar electrode (CO2-700–1 h) was determined by evaluating the TOC, dye removal efficiencies and peroxide production. Then, the process parameters (pH, time, potential, catalyst-electrolyte concentration, electrolyte type) were examined to determine optimum wastewater treatment conditions. In the next step, the economic results of the study were analyzed in the optimum conditions by comparing 3 electrodes. The treatment cost obtained with the CO2-700–1 h was 34.9% and 8.64% lower than the raw biochar (N2-350–4 h) electrode and its nitrogen gas-modified counterpart (N2-700–1 h). Dye and TOC removal efficiency increased up to 2.12 and 4.65 times, respectively. The TOC efficiency of the regenerated electrode decreased by only 9.94% at the end of 10 cycles.