Effect of biochar on bio-electrochemical dye degradation and energy production

Application of biochar on soil bioelectrochemical remediation: behind roles, progress, and potential

Bioelectrochemical systems (BESs) that combine electrochemistry with biological methods have gained attention in the remediation of polluted environments, including wastewater, sludge, sediments, and soils. The most attractive advantage of BESs is that the solid electrode is used as an inexhaustible electron acceptor or donor, and biocurrent directly converted from organics can afford the reaction energy of contaminant breakdown, crossing the internal energy barrier of endothermic degradation, which achieves a continuous biodegradation process without the simultaneous use of exogenetic chemicals and bioelectricity recovery. However, soil BESs are hindered by expensive electrode materials, difficult pollutant and electron transfer, low microbial competitive activity, and biocompatibility in contamination remediation. Fortunately, introducing biochar into soil BESs could reveal a high potential in addressing these BES inadequacies. The characteristics of biochar, e.g., conductivity, transferability, high specific surface area, high porosity, large functional groups, and biocompatibility, can improve the performance of soil BESs. In fact, biochar not only carries electrons but also transfers nutrients, pollutants, and even bacteria by facilitating transmission in the bioelectric field of BESs. Consequently, the abilities of biochar make for better functionality of BESs. This review collates information on the roles, application, and progress of biochar in soil BESs, and future prospects are given. It is beneficial for environmental researchers and engineers to extend BES application in environmental remediation and to assist the progress of carbon sequestration and emission reduction based on the inertia of biochar and the blocking of electron flow to form methane.

Green metal oxides coated biochar nanocomposites preparation and its utilization in vertical flow constructed wetlands for reactive dye removal: Performance and kinetics studies

Major causes of water pollution in the ecosystem are pollutants such as dyes which are noxious. The present study was based on the synthesis of the green nano-biochar composites from cornstalk and green metal oxide resulting in Copper oxide/biochar, Zinc oxide /biochar, Magnesium oxide/biochar, Manganese oxide/biochar, biochar for removal of dyes combined with the constructed wetland (CW). Biochar Augmentation in constructed wetland systems has improved dye removal efficiency to 95% in order of copper oxide/biochar > Magnesium oxide/biochar > Zinc oxide/biochar > Manganese oxide/biochar > biochar > control (without biochar) respectively in wetlands. It has increased the efficiency of pH by maintaining pH 6.9-7.4, while Total Suspended Solids (TSS) removal efficiency and Dissolved oxygen (DO) increased with the hydraulic retention time of about 7 days for 10 weeks. Chemical oxygen demand (COD) and colour removal efficiency increased with the hydraulic retention time of 12 days for 2 months and there was a low removal efficiency for total dissolved solids (TDS) from control (10.11%) to Copper oxide /biochar (64.44%) and Electrical conductivity (EC) from control (8%) to Copper oxide /biochar (68%) with the hydraulic retention time of about 7 days for 10 weeks. Colour and chemical oxygen demand removal kinetics followed second and first-order kinetic. A significant growth in the plants were also observed. These results proposed the use of agricultural waste-based biochar as part of a constructed wetland substratum can provide enhanced removal of textile dyes. That can be reused.

Recent advancements in microbial fuel cells: A review on its electron transfer mechanisms, microbial community, types of substrates and design for bio-electrochemical treatment

The development in urbanization, growth in industrialization and deficiency in crude oil wealth has made to focus more for the renewable and also sustainable spotless energy resources. In the past two decades, the concepts of microbial fuel cell have caught more considerations among the scientific societies for the probability of converting, organic waste materials into bio-energy using microorganisms catalyzed anode, and enzymatic/microbial/abiotic/biotic cathode electro-chemical reactions. The added benefit with MFCs technology for waste water treatment is numerous bio-centered processes are available such as sulfate removal, denitrification, nitrification, removal of chemical oxygen demand and biological oxygen demand and heavy metals removal can be performed in the same MFC designed systems. The various factors intricate in MFC concepts in the direction of bioenergy production consists of maximum coulombic efficiency, power density and also the rate of removal of chemical oxygen demand which calculates the efficacy of the MFC unit. Even though the efficacy of MFCs in bioenergy production was initially quietly low, therefore to overcome these issues few modifications are incorporated in design and components of the MFC units, thereby functioning of the MFC unit have improvised the rate of bioenergy production to a substantial level by this means empowering application of MFC technology in numerous sectors including carbon capture, bio-hydrogen production, bioremediation, biosensors, desalination, and wastewater treatment. The present article reviews about the microbial community, types of substrates and information about the several designs of MFCs in an endeavor to get the better of practical difficulties of the MFC technology.

Use of Biochar-Based Cathodes and Increase in the Electron Flow by Pseudomonas aeruginosa to Improve Waste Treatment in Microbial Fuel Cells

In this paper, we tested the combined use of a biochar-based material at the cathode and of Pseudomonas aeruginosa strain in a single chamber, air cathode microbial fuel cells (MFCs) fed with a mix of shredded vegetable and phosphate buffer solution (PBS) in a 30% solid/liquid ratio. As a control system, we set up and tested MFCs provided with a composite cathode made up of a nickel mesh current collector, activated carbon and a single porous poly tetra fluoro ethylene (PTFE) diffusion layer. At the end of the experiments, we compared the performance of the two systems, in the presence and absence of P. aeruginosa, in terms of electric outputs. We also explored the potential reutilization of cathodes. Unlike composite material, biochar showed a life span of up to 3 cycles of 15 days each, with a pH of the feedstock kept in a range of neutrality. In order to relate the electric performance to the amount of solid substrates used as source of carbon and energy, besides of cathode surface, we referred power density (PD) and current density (CD) to kg of biomass used. The maximum outputs obtained when using the sole microflora were, on average, respectively 0.19 Wm−2kg−1 and 2.67 Wm−2kg−1, with peaks of 0.32 Wm−2kg−1 and 4.87 Wm−2kg−1 of cathode surface and mass of treated biomass in MFCs with biochar and PTFE cathodes respectively. As to current outputs, the maximum values were 7.5 Am−2 kg−1 and 35.6 Am−2kg−1 in MFCs with biochar-based material and a composite cathode. If compared to the utilization of the sole acidogenic/acetogenic microflora in vegetable residues, we observed an increment of the power outputs of about 16.5 folds in both systems when we added P. aeruginosa to the shredded vegetables. Even though the MFCs with PTFE-cathode achieved the highest performance in terms of PD and CD, they underwent a fouling episode after about 10 days of operation, with a dramatic decrease in pH and both PD and CD. Our results confirm the potentialities of the utilization of biochar-based materials in waste treatment and bioenergy production.

One-Step Preparation of Biochar Electrodes and Their Applications in Sediment Microbial Electrochemical Systems

Biochar is a kind of carbon-rich material formed by pyrolysis of biomass at high temperature in the absence or limitation of oxygen. It has abundant pore structure and a large surface area, which could be considered the beneficial characteristics for electrodes of microbial electrochemical systems. In this study, reed was used as the raw material of biochar and six biochar-based electrode materials were obtained by three methods, including one-step biochar cathodes (BC 800 and BC 700), biochar/polyethylene composite cathodes (BP 5:5 and BP 6:4), and biochar/polyaniline/hot-melt adhesive composite cathode (BPP 5:1:4 and BPP 4:1:5). The basic physical properties and electrochemical properties of the self-made biochar electrode materials were characterized. Selected biochar-based electrode materials were used as the cathode of sediment microbial electrochemical reactors. The reactor with pure biochar electrode (BC 800) achieves a maximum output power density of 9.15 ± 0.02 mW/m2, which increases the output power by nearly 80% compared with carbon felt. When using a biochar/polyaniline/hot-melt adhesive (BPP 5:1:4) composite cathode, the output power was increased by 2.33 times. Under the premise of ensuring the molding of the material, the higher the content of biochar, the better the electrochemical performance of the electrodes. The treatment of reed powder before pyrolysis is an important factor for the molding of biochar. The one-step molding biochar cathode had satisfactory performance in sediment microbial electrochemical systems. By exploring the biochar-based electrode, waste biomass could be reused, which is beneficial for the environment.

Insight to nitrification during cattle manure-maize straw and biochar composting in terms of multi-variable interaction

This study investigated nitrification process during cattle manure-maize straw (CM) and biochar (CMB) composting in terms of multi-variable interaction (MVI) among environmental parameters, ammonia-oxidizing archaea (AOA) and bacteria (AOB) community structure, nitrogen-related enzymes as well as substrates using structural equation model (SEM). Results showed that adding biochar significantly reduced potential ammonia oxidation rates. SEM analysis revealed that AOB was affected by temperature and pH, which stimulated the release of urease, increased NH4+-N concentration and finally exerted influence on nitrification in CM. Temperature (0.755) and NO2--N (-0.994) were identified as the main factors mediating nitrification in CM and CMB, respectively. Moreover, MVI analysis indicated that nitrification and denitrification occurred simultaneously. Mutual verification of SEM and quantitative analyses (RNA level) confirmed that AOB predominated nitrification. The above results indicated that nitrification could be better explained by MVI using SEM during composting.

Applying a new pomelo peel derived biochar in microbial fell cell for enhancing sulfonamide antibiotics removal in swine wastewater

A sequential anode-cathode double-chamber microbial fuel cell (MFC) is a promising system for simultaneously removing contaminants, recovering nutrients and producing energy from swine wastewater. To improve sulfonamide antibiotics (SMs)'s removal in the continuous operating of MFC, one new pomelo peel-derived biochar was applied in the anode chamber in this study. Results demonstrated that SMs can be absorbed onto the heterogeneous surfaces of biochar through pore-filling and π-π EDA interaction. Adding biochar to a certain concentration (500 mg/L) could enhance the efficiency in removing sulfamethoxazole, sulfadiazine and sulfamethazine to 82.44-88.15%, 53.40-77.53% and 61.12-80.68%, respectively. Moreover, electricity production, COD and nutrients removal were improved by increasing the concentration of biochar. Hence, it is proved that adding biochar in MFC could effectively improve the performance of MFC in treating swine wastewater containing SMs.

New applications of quinone redox mediators: Modifying nature-derived materials for anaerobic biotransformation process

Due to their wide-distribution, high-biocompatibility and low-cost, nature-derived quinone redox mediators (NDQRM) have shown great potential in bioremediation through mediating electron transfers between microorganisms and between microorganisms and contaminants in anaerobic biotransformation processes. It is obvious that their performance in bioremediation was limited by the availability of quinone-based groups in NDQRM. A sustainable solution is to enhance the electron transfer capacity and retention capacity by the modification of NDQRM. Therefore, this review comprehensively summarized the modification techniques of NDQRM according to their multiple roles in anaerobic biotransformation systems. In addition, their potential applications in greenhouse gas mitigation, contaminant degradation in anaerobic digestion, contaminant bioelectrochemical remediation and energy recovery were discussed. And the problems that need to be addressed in the future were pointed out. The obtained knowledge would promote the exploration of novel NDQRM, and provide suggestions for the design of anaerobic consortia in biotransformation systems.

Waste-derived biochar: Applications and future perspective in microbial fuel cells

Application of microbial fuel cell (MFC) is coming to the forefront as a dual-purpose system for wastewater treatment and energy recovery. Future research should emphasize on developing low-cost field-scale MFCs for removal of organic matter, nutrients, xenobiotic and recalcitrant compounds from wastewaters and powering low energy devices. For achieving this, low-cost electrodes, low-cost yet efficient cathode catalysts and proton exchange membrane (PEM) should be developed from waste-based resources to salvage the waste-derived material as much as possible, thereby reducing the fabrication cost of this device. Biochar is one such low-cost material, which has wide range of applications. This review discusses different applications of biochar in MFC, viz. in the form of standalone electrodes, electrocatalyst and material for PEM in light of different characteristics of biochar. Further emphasis is given on the future direction of research for implementation of biochar-based PEMs and electrodes in field-scale MFCs.

A Review of Non-Soil Biochar Applications

Biochar is the solid residue that is recovered after the thermal cracking of biomasses in an oxygen-free atmosphere. Biochar has been used for many years as a soil amendment and in general soil applications. Nonetheless, biochar is far more than a mere soil amendment. In this review, we report all the non-soil applications of biochar including environmental remediation, energy storage, composites, and catalyst production. We provide a general overview of the recent uses of biochar in material science, thus presenting this cheap and waste-derived material as a high value-added and carbonaceous source.

Adsorption of an Anionic Azo Dye Using Moringa oleifera Seed Protein-Montmorillonite Composite

In this study, Moringa oleifera seed protein-montmorillonite (MOSP-MMT) composite was synthetized using the impregnation method. The MOSP-MMT adsorbent was characterized using scanning electron microscope, X-ray diffraction, infrared spectroscopy, surface area analysis, and thermogravimetric analysis. The removal of water-soluble reactive red 2 (RR-2) from artificial wastewater by the MOSP-MMT composite was carried out in a batch system. The results indicated that RR-2 adsorption increased with contact time, and the pseudo-second-order equation was best to describe the adoption process among the three models. The RR-2 adsorption decreased from 7.60 to 5.92 mg/g as pH increased from 3.2 to 9.1 and increased from 15.2 to 17.1 mg/g as NaCl concentration increased from 0 to 30 g/L. The Freundlich isotherm model provided the better fit of the experimental data than the Langmuir model. The result showed that the MOSP-MMT composite could be a potential adsorbent for the treatment of wastewater containing RR-2.