Waste Disposal & Sustainable Energy最新文献

Biochar, derived from the waste pyrolysis process, is a promising class of functional materials for environmental remediation owing to its large surface area, abundant surface functionalities and redox properties. This review focuses on the compositions, structures and electron transfer abilities of biochar and their roles in pollutant transformation in environmental remediation. First, the redox properties of biochar are systemically introduced, and the influencing factors are thoroughly discussed. Furthermore, biochar-involved redox reactions for pollutant reduction are distinctly classified on the basis of the different oxidants and reaction conditions. The reactive species in each system are comprehensively introduced, while the roles of biochar are adequately analyzed. This review aims to address the growing need for a comprehensive understanding of the role of biochar in pollutant transformation. Moreover, it also seeks to guide future research and the design of biochar materials for advanced water purification, highlighting the need for precise control of redox properties to achieve improved environmental outcomes.

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Freshwater sludge (FS), a by-product of drinking water treatment, is produced in large quantities globally but remains underutilized, predominantly ending up in landfills. As landfill space becomes increasingly scarce and environmental regulations tighten, there is an urgent need for sustainable management strategies for FS. By adopting circular economy principles that emphasize reuse and recycling, potential solutions can be found. This study analyzed the chemical and mineral compositions as well as leaching behavior of ten FS batches collected from various Singapore waterworks. It explored the potential applications of FS, addressing challenges and proposing solutions for its repurposing. The results revealed that FS primarily consists of aluminum oxide (34.94%–57.2%), sulfur trioxide (5.56%–8.98%), and silicon dioxide (1.24%–6.85%). FS also contains minerals such as aluminum sulfate, bayerite, kaolinite, and quartz. The primary variation among different batches of FS was the organic content (28.89%–52.3%), which mainly consisted of carbon, hydrogen, and oxygen. The leaching test indicated that the heavy metal concentrations in FS were within safe limits, suggesting its safety for various applications, especially in high pH environments. The substantial organic content of FS makes it a candidate for conversion into biochar and hydrochar for soil amendment. The rich aluminum content in FS opens avenues for its application in construction material fabrication, soil enhancement, and the remediation of heavy metal-laden wastes, soils, and wastewater.

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The rational pore structure and abundant surface functional groups of hierarchical porous carbons (HPCs) are important for their practical application in supercapacitors. The liquid linoleic acid and solid melamine were thoroughly mixed and subjected to carbonization under autogenic pressure at elevated temperatures (CAPET), followed by KOH activation, to produce uniformly N-doped HPCs. The structure and surface chemical properties are controlled by adjusting the N-doped ratio. This adjustment results in high conductivity, abundant ion-accessible surfaces, hierarchical porosity with appropriate micro-mesoporous channels, as well as the presence of N and O heteroatoms. The addition of melamine markedly increased the surface area to 3474.1 m² g⁻¹ and the mesopore volume proportion to 72.9%‒77.3% in the HPCs. The crystal structure and functional groups of the HPCs were revealed by X-ray diffractometer, Raman spectrometry, and X-ray photoelectron spectrometry, indicating that LA-HPCs-N0.5 is a promising electrode material for supercapacitors. This material presented excellent capacitance storage performance and cycling stability, with a specific capacitance of 430.2 F g⁻¹ at 1 A g⁻¹ in a 6 mol L⁻¹ KOH electrolyte system, and the capacitance retention rate was 86.5% after 2000 cycles of charging and discharging at 10 A g⁻¹. This study has successfully demonstrated that the template-free preparation of N-doped HPCs from waste oil is feasible, economical, and sustainable.

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In this study, acrylic fibers waste blended with different ratios of nanochitosan (0.5%, 1%, 2% and 4%, in weight) were converted into antifouling ultrafiltration nanocomposite membranes using a phase separation technique for the remediation of Congo red (CR) and crystal violet (CV) dyes from water. The fabricated nanocomposite membranes were investigated using Fourier Transform Infrared (FTIR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscope (SEM). The membrane hydrophilicity was estimated using contact angle measurements, which revealed that the 4% loaded nanochitosan had the highest hydrophilicity. Additionally, the water uptake, porosity, water contact angle and water flux of the nanocomposite membranes were assessed. The membrane filtration performances were explored for the removal of CR and CV as anionic and cationic dyes, respectively, at different concentrations and various applied pressures (1 bar to 4 bar). The experimental data revealed a high rejection (R) performance for CR (R≃100%) with a high water flux of about 150 L/(m²·h) to 183 L/(m²·h) for the optimized membrane with 2% nanochitosan at an applied pressure of 4 bar. The rejection for CV showed a variant rejection (70%–99%) at different dye concentrations with fluxes ranging from 93.6 L/(m²·h) to 149.5 L/(m²·h) for the same composite membrane. The composite membrane showed enhanced flux recovery after fouling by bovine serum albumin and was resistant to widespread gram-positive (Staphylococcus aureus) bacteria.

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Iron element is known to be an effective additive for accelerating the anaerobic digestion (AD) process for treating organic wastes. However, the effects of different kinds of iron additives on food waste (FW) and sewage sludge of co-digestion process have not been yet investigated thoroughly. This study aimed to elucidate how different kinds of iron components affect methane production during FW and sewage sludge anaerobic co-digestion (co-AD) process and to investigate the possible mechanism of Fe amendment. Experimental results revealed that Fe amendment could effectively promote the substrate degradation and methane production, and FeCl₃ amended group presented the best digestion performance, boosting the methane production from 465.9 mL to 2650.4 mL. The results of the excitation-emission matrix fluorescence spectra analysis further supported that Fe supplements facilitated the waste hydrolysis with a higher concentration of dissolved organic matters and thereby more substrates can be used for methane generation. In addition, the activity of coenzyme F420 and direct interspecies electron transfer in FeCl₃ group were 5.82 and 5.89 times higher than those in the control group, respectively, indicating that electron transfer, particularly the interspecies one, was enhanced by Fe amendment. As compared to that in the control group, the increased cytochrome c concentration in Fe amended groups also proved it. Therefore, this study will provide a reference regarding Fe amendment in the co-AD process for FW and sewage sludge.

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Kitchen waste solid residues (KWSR) are secondary organic solid wastes generated from kitchen waste (KW) after oil and slurry separation. In this study, two recycling methods for KWSR were investigated: direct membrane-covered aerobic composting (T1) and a two-stage method combining vermicomposting with membrane-covered aerobic composting (T2). Compared with T1, T2 had a faster increase in pile temperature, a shorter thermal stage, lower greenhouse gas emissions and higher NH₃ emissions. The vermicomposting promoted the formation of humus and shortened the maturation time during aerobic composting, resulting in a shorter treatment period for T2 (18 d) than for T1 (21 d). The initial bacterial communities of T1 and T2 were significantly different, but they became similar as composting progressed. The economic feasibility analysis showed that 1000 kg of KWSR generated a profit of 285 CNY using the T2 method, which was higher than that of T1 (36 CNY). The outcomes of the present study provide an improved strategy for the management of KWSR.

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Extracellular polymeric substances (EPSs) play a crucial role in various applications, especially in wastewater treatment. This review explores the importance of EPS in modern treatment methods, emphasizing its organic polymeric nature and properties that aid in effective pollutant removal and resource conservation. The study focuses on biological strategies utilizing microbial and bacterial communities, as well as electrolyte precipitate systems containing various components such as uronic acids, proteins, and carbohydrates that are essential for treatment processes. This review also describes the complex mechanisms regulating EPS biosynthesis, highlighting the impact of factors such as temperature, light intensity, and carbon to nitrogen ratio on EPS production. These findings emphasizes the influence of carbon supply and nitrogen sources on EPS formation, shedding light on the relationship between environmental conditions and EPS synthesis. In addition, this study discusses the significance of EPS extraction techniques for maintaining material integrity. Furthermore, the review explores the broad applications of EPS beyond wastewater treatment, including soil aggregation, pharmaceuticals, the food industry, and sustainable energy generation through EPS-driven microbial fuel cells. Understanding the diverse functions of EPS has the potential to improve environmental practices, mitigate climate change effects, and enhance industrial processes towards sustainability and efficiency. The versatility of EPS underscores its transformative impact on environmental and industrial practices.

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Pyrolysis kinetics were used in this study to analyze the pore formation mechanism of coal activated with KOH. Experimental derivative thermogravimetry (DTG) curves were fitted using Achar and Coats–Redfern methods to obtain kinetic parameters, such as activation energies. The effects of heating rate and KOH ratio on the activation energy show similar trends. Another attempt was trying to correlate the activation energies with the textural properties. The direct fitting was initially used and the obtained activation energies showed little correlation with textural properties. Two improved methods, namely, single peak fitting and multi peak fitting, were introduced. The former only considered the interaction between KOH and coal, regardless of coal pyrolysis. The activation energies obtained showed linear relation with the total pore volumes/BET (Brunauer–Emmett–Teller) surface areas (R²=0.94/0.99). The latter used Gaussian function to deconvolute the DTG curves, and then, each theoretical DTG peak could be correctly fitted. The positive linear correlation between the summed activation energies derived from surface reactions and metallic K intercalation and micropore volumes/surface areas was obtained (R²=0.993/0.996). Therefore, the proposed methods could be successfully applied to design and analyze the textural properties of specific coals with KOH activation.

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Slum dwellers often fail to expend enough on waste disposal to have a healthy life, and remittances provide funds for a household to expend on the betterment of life conditions. This paper examines the impact of remittances on total monthly waste disposal expenditures and the impact of better waste disposal on monthly health expenditures among slum households in Bangladesh. Propensity score matching was adopted as an identification strategy to reduce selection bias. In this study, remittance includes both remittances received from within and outside Bangladesh. Remittance receipt equals 1 if a household receives remittances from within and/or outside of Bangladesh. Our results show that remittances increase expenditures on waste disposal by 28.77% to 32.74% among slum households in Bangladesh. Waste disposal expenditure is considered as an indicator of better waste disposal. Furthermore, we find that better waste disposal reduces total outpatient expenditures. A reduction in outpatient expenditure indicates that waste disposal results in better health conditions for slum dwellers. The findings of this study can be connected to Sustainable Development Goal 11, which targets sustainable cities and communities and suggests that remittances are a bottom-up financial mechanism for improving waste disposal at the micro level to improve health status.

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This paper reviews recent advances in the use of graphite carbon nitride (g-C₃N₄)-based composite photocatalysts for antibiotic and dye degradation and hydrogen production. It also discusses the structure, synthesis, modification, morphology, doping, preparation, and application of a particular subject and evaluates the advantages and disadvantages of different morphologies and preparation processes. The photocatalysts based on g-C₃N₄-based composites have demonstrated great potential. The g-C₃N₄ has been modified and tailored into various novel structures and morphologies to improve its efficiency in the photocatalytic degradation of pollutants. The techniques such as doping, metal deposition, heterojunction formation, and structural tuning enhance the rate of light absorption, charge transfer, and charge separation of g-C₃N₄. This leads to improved photocatalytic performance for antibiotic and dye degradation and hydrogen production.