Non-noble metal catalyst with high catalytic activity and stability towards oxygen reduction reaction (ORR) is critical for durable bioelectricity generation in air-cathode microbial fuel cells ...(MFCs). Herein, nitrogen-doped (iron-cobalt alloy)/cobalt/cobalt phosphide/partly-graphitized carbon ((FeCo)/Co/Co2P/NPGC) catalysts are prepared by using cornstalks via a facile method. Carbonization temperature exerts a great effect on catalyst structure and ORR activity. FeCo alloys are in-situ formed in the catalysts above 900 °C, which are considered as the highly-active component in catalyzing ORR. AC-MFC with FeCo/Co/Co2P/NPGC (950 °C) cathode shows the highest power density of 997.74 ± 5 mW m−2, which only declines 8.65% after 90 d operation. The highest Coulombic efficiency (23.3%) and the lowest charge transfer resistance (22.89 Ω) are obtained by FeCo/Co/Co2P/NPGC (950 °C) cathode, indicating that it has a high bio-electrons recycling rate. Highly porous structure (539.50 m2 g−1) can provide the interconnected channels to facilitate the transport of O2. FeCo alloys promote charge transfer and catalytic decomposition of H2O2 to •OH and •O2−, which inhibits cathodic biofilm growth to improve ORR durability. Synergies between metallic components (FeCo/Co/Co2P) and N-doped carbon energetically improve the ORR catalytic activity of (FeCo)/Co/Co2P/NPGC catalysts, which have the potential to be widely used as catalysts in MFCs.
Display omitted
•Residual cornstalks as the recycling carbon source are environmental-friendly.•FeCo alloy anchored in N-doped carbon improves ORR catalytic activity in AC-MFCs.•Porous carbon structure with doped N-species facilitates the O2 transport for ORR.•AC-MFC with FeCo/Co/Co2P/NPGC (950 °C) cathode has higher power output than Pt/C.•FeCo/Co/Co2P/NPGC catalyst shows a good durability for long-time AC-MFCs operation.
Agricultural waste biomass (AWB) is becoming a significant sustainable alternative for fossil fuels. Emergy analysis (EmA) is a promising methodology that provides a uniform standard to assess ...simultaneously the environmental load and economic returns of a system. Relevant studies on the assessment of AWB energy-oriented utilization by EmA are attracting researchers' attention worldwide. Therefore, this paper aimed to comprehensively review state-of-the-art applications of the EmA for AWB energy-oriented utilization systems. Results indicated that there were limitations and challenges in the application of single EmA. Importantly, the boundary of AWB energy-oriented utilization systems in the application of EmA was not unified, leading to poor comparability of the impact results. Although the effect of policies has a significant influence on the application and promotion of AWB energy-oriented utilization, the EmA method can hardly reflect the effect of policies. Therefore, there is a need in combination with other methods to optimize the EmA, thus providing comprehensive guidance for decision-makers. Finally, based on these, some feasible suggestions especially to (1) further promote the application and (2) development of this research field were presented. It is hoped that this work could support the proper evaluation and further optimization of AWB energy-oriented utilization systems.
Display omitted
•State-of-the-art studies on EmA of AWB energy-oriented utilization were reviewed.•The EmA of AWB energy-oriented utilization is still in its infancy.•EmA can provide suggestions for energy-oriented sustainable utilization of AWB.•Collaboration with other methods is found to improve the performance of EmA.•Suggestions on the EmA of AWB energy-oriented utilization were presented.
A novel preparation protocol for synthetic, look-a-like humic substances (i.e., fulvic and humic acids) simulating geochemical processes through hydrothermal reaction is presented, with crude waste ...biomass as an omnipresent and universal precursor. The chemical nature of the organic scaffold and the type and abundance of oxygen-containing functional groups of the synthetic humic substances (A-FA and A-HA) are revealed by a series of examinations. Results from EA, XPS analyze, FTIR spectra and NMR technology matched well each other, suggesting high similarity on chemical structure (abundant aromatic frameworks) and contents (e.g. N and S elements) in both humic acids. Pyrolysis-gas-chromatography/mass spectrometry (Py-GC/MS) analysis is employed on the organic structure and is directly compared to extracted natural humic matter from black soils (Harbin, China). Dehydrated carbohydrates and their condensates with low molecular weight that are rich in oxygen are the main structural components of the artificial fulvic acids, while aromatic structures and aliphatic side chains are almost absent. Aromatics (7.43%) and in some cases long-chain aliphatics (7.15%) are more prominent in the A-HA sample. The combination of the diverse analytical techniques not only allows a better understanding of artificial fulvic and humic acids, but also supports the high similarity to natural humic substances in structure and morphology. As the technology can be easily scaled and is comparable cheap, the as obtained products can be discussed to rehabilitate used up farm land.
Display omitted
•Novel artificial humic substances simulating geochemical processes are presented.•High similarity between artificial- and natural humic substances is demonstrated.•Plausible schemes for preparation under hydrothermal conditions are presented.
Environmental pollution remains a constant challenge due to the indiscriminate use of fossil fuels, mining activities, chemicals, drugs, aromatic compounds, pesticides, etc. Many emerging pollutants ...with no fixed standards for monitoring and control are being reported. These have adverse impacts on human life and the environment around us. This alarms the wastewater management towards developing materials that can be used for bulk water treatment and are easily available, low cost, non-toxic and biodegradable. Waste biomass like pectin is extracted from fruit peels which are a discarded material. It is used in pharmaceutical and nutraceutical applications but its application as a material for water treatment is very limited in literature. The scientific gap in literature review reports is evident with discussion only on pectin based hydrogels or specific pectin derivatives for some applications. This review focuses on the chemistry, extraction, functionalization and production of pectin derivatives and their applications in water treatment processes. Pectin functionalized derivatives can be used as a flocculant, adsorbent, nano biopolymer, biochar, hybrid material, Metal-organic frameworks, and scaffold for the removal of heavy metals, ions, toxic dyes, and other contaminants. The huge quantum of pectin biomass may be explored further to strengthen environmental sustainability and circular economy practices.Environmental pollution remains a constant challenge due to the indiscriminate use of fossil fuels, mining activities, chemicals, drugs, aromatic compounds, pesticides, etc. Many emerging pollutants with no fixed standards for monitoring and control are being reported. These have adverse impacts on human life and the environment around us. This alarms the wastewater management towards developing materials that can be used for bulk water treatment and are easily available, low cost, non-toxic and biodegradable. Waste biomass like pectin is extracted from fruit peels which are a discarded material. It is used in pharmaceutical and nutraceutical applications but its application as a material for water treatment is very limited in literature. The scientific gap in literature review reports is evident with discussion only on pectin based hydrogels or specific pectin derivatives for some applications. This review focuses on the chemistry, extraction, functionalization and production of pectin derivatives and their applications in water treatment processes. Pectin functionalized derivatives can be used as a flocculant, adsorbent, nano biopolymer, biochar, hybrid material, Metal-organic frameworks, and scaffold for the removal of heavy metals, ions, toxic dyes, and other contaminants. The huge quantum of pectin biomass may be explored further to strengthen environmental sustainability and circular economy practices.
Biochar has shown a unique electrochemical property being involved in various redox reactions in soil and water. In this study, the electron donating capacities (EDCs) of biochar pyrolyzed at ...200–800 °C from pine wood, barley grass and wheat straw were investigated by using the mediated electrochemical oxidation method. The EDC values for all biochar were in the range of 0.18–1.83 mmol e− (g biochar)−1, showing the increase as the temperature increased from 200 °C to 400 °C, the decrease from 400 °C to 650 °C, and then increase from 650 °C until to 800 °C. At low and intermediate temperatures of 200–650 °C, the EDCs were mainly attributed to the phenolic hydroxyl groups, while the conjugated π-electron system associated with aromatic structure dominated the EDCs of biochar at the high temperatures of over 650 °C. The barley grass- and wheat straw-derived biochar had higher EDCs than the pine wood-derived biochar, resulting from the higher phenolic hydroxyl groups in the former samples than the latter one. In conclusion, the reductive property of biochar was mainly attributed to both phenolic hydroxy group and conjugated π-electron system associated with aromatic structure, depending on the pyrolytic temperature and feedstock source. The results will help us to obtain a complete view on the role of biochar in biogeochemical redox reactions and consider developing biochar with controlled redox properties for specific environmental applications such as electron shuttle and catalyst material.
•Quantification of the relationship between EDCs and phenolic groups and conjugate π-electron system were reported.•At low and intermediate temperatures, the EDCs were mainly attributed to the phenolic groups.•At high temperatures, the conjugated π-electron system associated with aromatic structure dominated the EDCs of biochar.•Developing biochar with controlled redox properties was proposed for specific environmental applications.
Display omitted
•Carbon nanofiber supported hydrothermal carbon and fiber is fabricated by straw.•Carbon coating preserved the fiber strength during the growth process of nanofibers.•The all-solid ...product exhibits a high energy density and power density.
The development of high-performance flexible supercapacitor using biomass wastes as raw materials to overcome the high manufacturing cost has attracted excellent interest. Herein, a hierarchical structure of carbon nanorods supported hydrothermal carbons and carbon fibers (CNR/HTC/CFs) with superior electrochemical performance as well as high strength is successfully designed for the first-time using waste straw as a sustainable and economic carbon resource. The straw pyrolysis gases after purification are introduced to support the formation of high specific surface area CNRs via a simple vapor phase growth process. The CNR/HTC/CFs exhibit high mass specific capacitance of 269.47 F g−1 under the scan rate of 3 mV s−1 in three-electrode system. A high energy density of 15.54 Wh kg−1 with the power density of 0.49 kW kg−1 was obtained in the as-assembled all solid-state supercapacitor device with gel electrolyte, whose value retains as high as 6.99 Wh kg−1 with the power density of 10.01 kW kg−1. The tensile strength of the finally fibers can reach up to 2743 ± 467 MPa, which is sufficient for many practical industrial applications. This work provides a feasible synthetic strategy using sustainable biomass waste as raw materials to prepare high strength and capacitance energy storage devices.
Display omitted
•Thermo-chemical and biological technologies for tea waste biomass conversion are reviewed.•Tea waste derived biochar is an ideal bio-adsorbent on pollutants adsorption.•Composting ...can enhance the nutrients of the bio-fertilizer derived from tea waste.
Along with the increasing consumption of tea and its extracts, the amount of tea waste grows rapidly, which not only results in huge biomass loss, but also increases environmental stress. In past years, interest has been attracted on utilization of tea waste biomass, and a lot of work has been carried out. This review summarized the progress in conversion of tea waste by thermo-chemical and biological technologies and analyzed the property of the derived products and their performance in applications. It was found that biochar derived from tea waste had relatively large surface area, porous structures, and abundant functional groups, and could be used as bio-adsorbents and catalysts and electrochemical energy storage, while the cost of its largescale production should be evaluated. Profoundly, biological conversion, including ensiling and composting, was suggested to be an effective way to develop the tea waste biomass in practice due to its low-cost and specific functions.
Display omitted
•Renewable non-edible seeds were used for pyrolysis.•Seven models were used to determine kinetic parameters.•Kinetic reaction data showed good agreement with experimental data.•VZ and ...DAEM methods produce minimal error compared with others.
The present study addressed the kinetics characteristics and pyrolysis behaviour of waste biomass Azadirachta indica (NM) and Phyllanthus emblica kernel (AM) in a thermogravimetric analyzer. Six model-free techniques such as Kissinger-Akahira-Sunose, Distributed Activation Energy Model, Friedman, Coats-Redfern, Ozawa-Flynn-Wall, Vyazovkin and Criado method were employed to evaluate the kinetic parameters at five varying heating rates (10–50 °C min−1). The physicochemical inspection directed that both the biomass had excellent prospects to produce energy and finest chemicals. FTIR study pointed strong evidence of moisture, protein, acid, and aromatics. The average apparent activation energy was found to be 176.66, 193.67, 196.06, 177.32 and 204.23 kJ mol−1 for NM and 184.77, 195.10, 189.95, 186.46, 184.57 kJ mol−1 for AM for KAS, OFW, FM, DAEM and VZ respectively. Further, master plot and thermodynamic study of AM and NM revealed that pyrolysis went through various reaction mechanisms at the time of pyrolysis.
•First of its kind attempt on kinetic analysis of waste sawdust biomass.•Five model-free methods were adopted in the present study.•Kinetic data show good agreements with experimental data.•Pine ...sawdust is more reactive than sal sawdust and areca nut husk.•Activation energy increases with increase in temperature and heating rate.•Burnout temperature increases with increase in heating rates.
The present study reports pyrolysis behavior of three waste biomass using thermogravimetric analysis to determine kinetic parameters at five different heating rates. Physiochemical characterization confirmed that these biomass have the potential for fuel and energy production. Pyrolysis experiments were carried out at five different heating rates (5–25 °C min−1). Five model-free methods such as Kissinger-Akahira-Sunose (KAS), Ozawa-Flynn-Wall (OFW), Friedman, Coats-Redfern, and distributed activation energy (DAEM) were used to calculate the kinetic parameters. The activation energy was found to be 171.66 kJ mol−1, 148.44 kJ mol−1, and 171.24 kJ mol−1 from KAS model; 179.29 kJ mol−1, 156.58 kJ mol−1, and 179.47 kJ mol−1 from OFW model; 168.58 kJ mol−1, 181.53 kJ mol−1, and 184.61 kJ mol−1 from Friedman model; and 206.62 kJ mol−1, 171.63 kJ mol−1, and 160.45 kJ mol−1 from DAEM model for PW, SW, AN biomass respectively. The calculated kinetic parameters are in good agreement with other reported biomass.
Unusual sheets-like primary activated carbon particles interconnected into three-dimensional micrometer-level large pores were prepared from a novel biomass named willow catkins (WCs) by KOH chemical ...activation process and used as electrode materials for supercapacitors. The pore structures, surface area and chemical properties could be facilely adjusted by changing the activation temperature. When the activation temperature increased from 600 to 800°C, the specific surface area of the porous carbon product increased remarkably while the contents of nitrogen and oxygen co-doped decreased, which significantly affected the electrochemical properties of the porous carbon-based supercapacitors. The activated carbons from 600°C activation possesses despite moderate specific surface area (645m2g−1), concentrated pore size distribution of 0.77nm, but high nitrogen (2.51wt.%) and oxygen (13.28wt.%) contents, high graphitization degree as well as good electrical conductivity. The supercapacitors with the carbon electrode reached maximal specific capacitances of 340Fg−1 and high specific surface capacitance of 52.7μFcm−2 at the current density of 0.1Ag−1, good rate capability (231Fg−1 at 10Ag−1) and good cycling stability (92% capacitance retention over 3000 cycles). The favorable capacitive performances make the waste biomass WCs act as a new resource of carbonaceous materials for high performance supercapacitors.
PDF
