Waste Disposal & Sustainable Energy最新文献

Intensive land use has several detrimental effects on land function and imposes an undue burden on the environment. Continuous farming and pollution by heavy metals have negatively influenced many soils. Biochar is now gaining attention as a major research subject in the areas of agriculture, environment, and energy as an eco-friendly soil conditioner. The use of biochar for agricultural and environmental purposes has been widely studied and reviewed. Unfortunately, there are few reviews on biochar structures and other biochar uses. This review presents an overview of current developments in the effects of numerous biochar physicochemical properties and biochar uses, such as utilization as a soil microbial activity, contaminant adsorbent, ion exchange, soil amendment, gas storage and water retention. The physical, chemical and biological properties have been discussed following amendments to the soil and conditions of preparation. However, scientific observation and research are required to identify the negative effects of biochar in preparations and applications. It is envisaged that further in-depth studies of biochar amendment will lead to a deeper understanding of biochar's relationships with soils and that reviews of the negative impacts of biochar could reveal ways in which they might be mitigated.

Microwave steam pyrolysis (MSP) is an innovative thermochemical approach to converting biomass into high-quality biochar using steam to improve the dielectric heating of microwave radiation. Biochar shows high fixed carbon and carbon contents at a maximum temperature of 550 °C in 10 min. The MSP achieved a heating rate of 112 °C/min from 200 °C to 400 °C to produce biochar effectively. Furthermore, the thermal properties of biochar in microwave heating were investigated in this study to explore its potential as a microwave heat-absorbent material. Microwave is able to perform volumetric and controllable heating to the biochar. Moreover, biochar shows good microwave heat absorbency, storing and transferring heat effectively. The temperature profile of three different sizes of biochar was investigated to examine the efficiency of biochar in heat absorption from microwave radiation. It was found that the powder form of biochar showed a higher heat transfer rate of 40 °C/min and a low cooling rate of 7.5 °C/min. The presented results are useful for evaluating the application of biochar as a promising medium for heat storage systems.

Alum sludge is a typical by-product of drinking water treatment processes. Most sludge is disposed of at landfill sites, and such a disposal method may cause significant environmental concern due to its vast amount. This paper assessed the feasibility of reusing sludge as a supplementary cementitious material, which could efficiently exhaust stockpiled sludge. Specifically, the pozzolanic reactivity of sludge at different temperatures, the reaction mechanism of the sludge–cement binder, and the resistance of sludge-derived mortar to microbially induced corrosion were investigated. The obtained results indicated that 800 °C was the optimal calcination temperature for sludge. Mortar containing sludge up to 30% by weight showed comparable physical properties at a curing age of 90 days. Mortar with 10% cement replaced by sludge can significantly improve the resistance to biogenic corrosion due to the formation of Al-bearing phases with high resistance to acidic media, e.g., Ca₄Al₂O₇·xH₂O and strätlingite.

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A novel selective catalytic reduction (SCR) catalyst with high catalytic activity on chloroaromatic organics at lower temperatures (160–180 ℃) is critical for municipal solid waste incineration (MSWI) plants. This study prepares a series of honeycomb-type VO_x/TiO₂ catalysts and finally develops a new low-temperature catalyst with high catalytic activity in eliminating chloroaromatic organics. Based on the conversion efficiency (CE) of 1,2-dichlorobenzene (1,2-DCB) and CO₂ selectivity, the optimal VO_x content of 4.06% (in weight) in VO_x/TiO₂ catalyst is first confirmed. By modifying CeO_x and WO_x, a novel honeycomb-type catalyst of VO_x–CeO_x–WO_x/TiO₂ achieves the highest CE (93.1%–93.6%) and CO₂ selectivity (40.9%–60.7%) at 150–200 ℃. It was found that the CeO_x and WO_x can improve the catalytic activity by enriching the surface content of V and O, increasing the proportion of V⁵⁺ and O_surf, enlarging the supply source of reactive oxygen species and their storage capacity, and accelerating the redox cycle of VO_x, CeO_x, WO_x, and reactive oxygen species. This study can guide the development of monolithic low-temperature catalysts with high catalytic activity in eliminating chloroaromatic organics in MSWI flue gas.

Hydrothermal carbonization (HTC) of food waste can produce hydrochar for further utilization as high-quality fuel or carbon materials, but the by-product of liquid effluent, named HTC wastewater, has a high chemical oxygen demand (COD) content and other organic pollutants. This study focused on the feasibility of Fenton oxidation combined with activated carbon (AC) to reduce COD in HTC wastewater. The effects of different parameters including pH, dosage of hydrogen peroxide, molar ratio of Fe²⁺/H₂O₂, and reaction time were tested and discussed. Eventually, through the optimized Fenton oxidation (pH = 3, H₂O₂ dosage = 1.5 mol/L, Fe²⁺/H₂O₂ = 1:15, reaction time = 60 min) combined optimized AC adsorption process (AC dosage = 30 g/L), the COD value reduced from 42,000 mg/L to 3075 mg/L, indicating a COD removal efficiency of 92.7% and a color removal ratio of 91.9%, respectively. The comparison of GC/MS (gas chromatography mass spectrometer) and FTIR (Fourier transform infrared spectrometer) of liquid residual from different treatment methods also indicated that the types of organic substances in HTC wastewater were significantly reduced through Fenton oxidation and AC adsorption.

Coal fly ash (CFA) is the main combustion residue of fine ground coal in the process of coal-fired thermal power generation, and crude glycerol (CG) is the byproduct of biodiesel production. The novel polyurethane/CFA (PU/CFA) foam composites were prepared from CFA and CG. Two kinds of CFA, CFAI and CFAII were used as fillers for the property enhancement of PU/CFA composites, and the effects on foaming behavior and the reinforcement for the PU/CFA composites were investigated. It was found that the addition of CFA can prolong the rising time and tack-free time, and the maximum rising time and tack-free time increased to 40 s and 42 s. Meanwhile, the maximum compressive strength of PU/CFAI and PU/CFAII increased to 0.2186 MPa and 0.2284 MPa with the addition of CFA. The thermogravimetric analysis showed that the PU/CFA composites underwent three stages of thermal decomposition, and the amount of carbon residue increased from 23.11% to 67.91% with increasing CFA dosage. Moreover, the values of the limit oxygen index increased from 21.5% to 23.7% with the incorporation of CFA into the PU foam matrix, indicating that CFA improved the thermal stability and flame retardant performance of the composites. This study provided a new method for the recycling and high-value utilization of CG and CFA.

The production of biohydrogen from biological processes is cleaner and more sustainable than that of fossil fuel-based hydrogen. The drive for cleaner and sustainable energy sources is an important facet of the bioeconomy. Based on these findings, this paper aimed to examine the significance and impact of biohydrogen on the bioeconomy. These bioprocessing strategies are primarily biophotolysis, fermentation and bio-electrolytic systems. Considering that biological processes are slow compared to other thermochemical production processes, production volumes cannot match that of the latter. The inherently slow nature of biochemical reactions taking place in living organisms is a challenge that puts biohydrogen at a disadvantage. Biological processes are also very sensitive to temperature and pH, thereby requiring more intricate process monitoring and control. To obtain equivalent volumes of biohydrogen compared to production strategies, larger and more intricate facilities would be needed, implying more cost implications. It is surmised that biohydrogen will continue to play an important role in the drive for a sustainable bioeconomy despite the current challenges it faces.

Metal recovery from bottom ash was deemed to be significant to achieve a higher stability of bottom ash and recycle valuable extractable metals. In China, the existing rugged industrial production ignores the actual metal distribution and thus fails to exploit the utilization potential of recoverable metals in bottom ash. Based on these findings, this work was proposed to obtain a comprehensive and in-depth study on the recoverability of metals in bottom ash. First, the particle size distribution and elemental composition of the bottom ash were analyzed. Then, complete information on the recoverable metals in bottom ash fractions with different sizes was obtained by washing, sorting, crushing, density separation and XRF (X Ray Fluorescence) analysis. The results showed that the smaller than 5 mm fraction accounted for up to 60% of the bottom ash, and the 5–20 mm fractions accounted for about 15%. The material characterization revealed that the contents of recoverable Fe, stainless steel, Al and Cu in bottom ash were averagely 9.01%, 0.136%, 0.78% and 0.08%, respectively. About 50% of Fe, 68% of Al, 61% of Cu, and 22% of stainless steel were distributed in smaller than 10 mm fraction. Particularly, Fe was evenly distributed among 0–2 mm, 2–5 mm, 5–10 mm fractions, and the content was between 5.41% and 7.5%. Non-magnetic stainless steel was mainly distributed in 20–40 mm and larger than 40 mm fractions. The highest share of Al was present in the fractions between 5 mm and 20 mm, accounting for 48% of the total aluminum. About 45.6% of the Cu was enriched in the 5–10 mm fraction. However, the Zn content was less than 0.01%. This work provides an in-depth understanding and information on metal recovery as well as promisingly guide ash utilization.

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The challenges in the current energy consumption patterns and demand–supply gap are driving the need to develop commercially viable and sustainable alternative fuels that are eco-friendly and efficient. Given the existing alternatives, hydrogen is regarded as the ultimate carbon-less clean and green fuel with high energy density. Considerable efforts are being made to develop catalysts/photo-catalysts for the efficient production of hydrogen from abundantly available water resources via water-splitting process. In this review, the photocatalytic activity of tin oxide-based hybrid photocatalytic materials for increased hydrogen production has been studied. The existing bottlenecks and proposed solutions have also been discussed.

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