Waste management最新文献

Recycling waste glass (WG) can be time-consuming, costly, and impractical. However, its incorporation into concrete significantly reduces environmental impact and carbon emissions. This paper introduces machine learning (ML) to civil engineering to optimise WG utilisation in concrete, supporting sustainability objectives. By employing a dataset of 471 experimental samples of waste glass concrete (WGC), various ML algorithms are applied, including Gradient Boosting Regressor (GBR), Random Forest (RF), Support Vector Regression (SVR), Adaptive Boosting (AdaBoost), Deep Neural Network (DNN), and k-Nearest Neighbours (kNN), to predict properties containing compressive strength (CS), alkali-silica reaction (ASR), and saved carbon credits (SCC). The proposed models achieve outstanding prediction performance with Coefficient of determination (R²) values of 0.95 for CS, 0.97 for ASR, and 0.99 for SCC using GBR and SVR, demonstrating high prediction accuracy with Root mean square error (RMSE) values of 3.31 MPa for CS, 0.03 % for ASR, and 0.11 for SCC. The SHapley Additive exPlanations (SHAP) analysis is utilised to interpret the model results, ensuring transparency and interpretability of the proposed ML models. The results reveal that the incorporation level of WG is a more significant influencing factor for these properties than the mean size of WG (MSWG).

This study employed a lab-scale fluidized bed steam gasification setup to perform the co-gasification experiments with blast furnace dust (BFD) and petcoke (PC) - wastes from the steel and refining industries, respectively. Multiple experiments were conducted at the optimized conditions to decipher the effects of the mineralogical content of the feed samples on the gasification performance parameters. With the addition of iron and zinc-abundant BFD sample to PC, an effective enhancement in the ability of the gasifier to produce hydrogen-rich synthesis gas was observed, attributed to an increase in surface active sites for gasification reactivity. An increase of almost 3% and 12 % in cold gas and carbon conversion efficiencies, respectively, was attributed to the catalytic effect of iron and zinc-containing phases in the product ash, resulting in a positive surge in the heating values and the product gas yields. To decipher the catalytic effect, the feed and product samples were characterized by employing analytical techniques of XRF, XRD, TGA, FTIR, SEM techniques with EDX analysis. The co-gasification product ash sample showed the formation of different zinc and iron dominating minerals, such as franklinite (ZnFe₂O₄), zincite (ZnO), hematite (Fe₂O₃), and magnetite (Fe₃O₄), to cater the needs of the growing world mineral demands, as a secondary mineral resource. This work exhibited a novel method to utilize industry wastes with the simultaneous removal of toxic substrates. Overall, potential energy recovery from industrial by-products was highlighted, providing insights towards developing a sustainable waste management technology with scalable prospects of a circular industrial economy.

Large scale production of insect larvae is considered a sustainable way to upcycle various organic waste- and by-products into more valuable food and feed products. The sustainability of insect larvae production depends on the substrates and species being used, but comparative studies that include both growth and efficiency are lacking. Here we compare larval fitness, including survival, development time, weight, substrate conversion efficiency, substrate reduction, and metabolic parameters across different combinations of densities and waste- and by-product-based substrates on the two fly species, the house fly (Musca domestica) and the black soldier fly (Hermetia illucens). The waste- and by-product-based substrates were a brewer's spent grain-based substrate, a digested sludge-based substrate, and a wheat bran/deproteinized grass-based substrate all highly abundant and of low value. Substrate and density significantly impacted on most larval growth and metabolic performance traits, but dependent on species. The brewer's spent grain-based substrate generally gave the highest performance in terms of larval weight, larval yield, and substrate conversion efficiency for both species, while a high density gave a higher larval yield and substrate conversion efficiency, but lower larval weight. Generally, black soldier fly larvae showed lower metabolic costs and higher net growth efficiency than house fly larvae. Altogether, our results demonstrate that both larval species, substrate, and larval densities affect larval growth and metabolic performance, and subsequently the scope for valorizing waste- or by-products to achieve a sustainable production of food and feed.

With the exponential growth of global photovoltaic (PV) installed capacity, the quantity of discarded PV modules continues to rise. This study innovatively explored the sustainable recovery and utilization of raw materials from discarded solar panels, focusing on the transformation of recycled silicon into microporous silica nanoparticles (MSN). Low toxic organic solvent ethyl acetate (EA) was for the first time utilized to reduce the viscosity of ethylene-vinyl acetate (EVA) and facilitated its removal. A simple combination of nitric acid (HNO₃) and sodium hydroxide (NaOH) at low temperatures (225 min HNO₃ etching at room temperature followed by 40 min NaOH etching at 70 °C) completely removed the deep blue anti-reflective coating SiN_x and successfully removed metallic impurities such as silver (Ag), aluminum (Al). Removal efficiencies for Ag and Al electrodes both reached 99 %, with recovery rates of 92 % and 99 % for Ag and Al, respectively. The recycled Ag and Si had a purity of 99 % and 93.2 %, respectively. The recycled pure Si was then dissolved in a NaOH solution to prepare a sodium silicate (Na₂SiO₃) solution. Under acidic conditions, the non-ionic surfactant Triton X-100 and cationic surfactant cetyltrimethylammonium bromide (CTAB) were used to transform the Na₂SiO₃ solution to the MSN. The specific surface area of the MSN measured by BET was 855.30 m²/g, with a pore size of 1.85 nm and a pore volume of 0.3963 cm³/g. This study highlights the innovative utilization of recovered silicon to fabricate advanced microporous materials, paving the way for high-value applications and promoting a sustainable photovoltaic industry.

Biofiltration is an important method for composting off-gas treatment. Compost-based materials are widely used as the filling media for biofilter. To expand the application of compost from different composting materials in off-gas control for organic waste aerobic composting, the NH₃ removal efficiency, N₂O generation, and microbial communities of ammonia monooxygenase (amoA functional gene was selected) and nitrite reductase (nirS functional gene was selected) were investigated using the animal manure compost (AMC) and sludge compost (SC) as filling materials. AMC showed a higher NH₃ removal efficiency (average 82.9 ± 12.1 %) than SC (average 58.9 ± 21.9 %). Achieving stable NH₃ removal took longer with the AMC biofilter than with the SC biofilter. More N₂O was emitted from the AMC than from the SC. The ammonia-oxidizing bacteria (AOB) community composition in the AMC changed significantly after 30 days, whereas the denitrifying bacterial communities changed minimally. The AOB community structure in the SC was more stable than that in the AMC; however, the community compositions in the AMC and SC gradually converged with the extension of operation. These results indicate that the AMC is more suitable than the SC as biofilter filling material for NH₃ control. This study provides a significant reference for optimizing the application of compost-based biofilter off-gas control technology.

There are hazardous substances such as chloride salts and heavy metals in the municipal solid waste incineration fly ash (WIFA). During thermal treatment, the concentrated chlorides promote the volatilization of heavy metals, increasing the ecological risk. The water washing method is also employed as a pre-treatment for WIFA, but a substantial volume of wastewater with high chloride content is produced that poses challenges for effective treatment. This study integrates chemical stabilization with heat treatment method and suggests the utilization of a calcium aluminum oxide-mayenite (CA) for the solidification of chloride salts and heavy metals in WIFA. The experimental results indicate that adding CA for heat treatment has a significant solidification effect on chlorides. Under the conditions of WIFA: CA mass ratio of 1: 1 and temperature of 1200 °C, the chloride ions were solidified by forming Ca₁₂Al₁₄O₃₂Cl₂, with a fixation efficiency of up to 85 %, and most of the chlorides in WIFA became insoluble instead of soluble. Most of the heavy metals in WIFA were immobilized and doped into the crystal structure of CA, forming the catalytic metal-rich Ca₁₂Al₁₄O₃₂Cl₂ phase, which was subsequently applied to the degradation of chlorobenzene. Under an initial concentration of 512 ppm, the degradation efficiency of chlorobenzene reached 50.4 %. Through the introduction of CA, not only the solidification of chloride and heavy metals is achieved, but the high-value resource utilization of the final heat treatment product is also realized, providing a new method for the disposal of fly ash.

This study demonstrates the potential of secondary aluminum dross (SAD) to enhance the vitrifying hazardous waste incineration fly ash (FA) and bottom slag (BS). Based on the CaO-SiO₂-Al₂O₃ ternary phase diagram, a liquid phase can be achieved at relatively low temperatures by carefully adjusting the Al₂O₃ content, particularly when the CaO to SiO₂ ratio is around 0.66. Theoretical melting temperature calculations indicate that substituting Al₂O₃ reagent with SAD enables the vitrification of FA and BS at temperatures below 1300 °C. TG-DSC results confirm this theoretical prediction, showing that the mixed system of FA, BS, and SAD lowers the liquid-phase formation temperatures compared to FA, BS, and SAD individually. Vitrification experiments, employing a composition of 55 wt%-60.5 wt% FA, 34 wt%-39 wt% BS, and 0.5 wt%-11 wt% SAD, achieved successful vitrification at 1350 °C for 2 h. This resulted in a high-quality vitrified product with a vitreous content exceeding 87.38%, an acid dissolution loss ratio below 2.32%, and heavy metals leaching toxicity below 0.15 mg/L. The exothermic nature of aluminum in SAD during the melting process contributes to enhance vitrification, making SAD a promising alternative to Al₂O₃ reagent.

The high chlorine content in municipal solid waste incineration (MSWI) fly ash is a key factor restricting its treatment and disposal. In this study, a new treatment method was proposed to enhance the deep dechlorination of fly ash by coupling supercritical CO₂ (SC) treatment with water washing. Simultaneously the alkaline compounds in fly ash can fix CO₂ and achieve CO₂ credits. The results showed that supercritical CO₂ significantly improved the removal of chlorine. The treatment of "double water washing + SC + washing again" reduced the chlorine content in fly ash to 0.83 %, while "SC + double water washing + SC + washing again" reduced the chlorine content to 0.88 %, and the removal rate of chlorine was as high as 96.8 % and 96.5 %, respectively. In addition, supercritical CO₂ promoted the decomposition of insoluble chloride (Friedel's salt) and the removal rate of insoluble chloride salts can reach 89.1 %. On the other hand, after supercritical CO₂ treatment, fly ash can quickly and efficiently absorb CO₂, and the amount of CO₂ absorbed after two supercritical CO₂ treatments was 64 g/kg. Lastly, supercritical CO₂ could significantly stabilize heavy metals in fly ash and reduce the concentrations of Pb and Cr in the washing solution.

To alleviate the energy crisis and control environmental pollution raised by spent lithium-ion batteries (LIBs), the development of efficient and economic methods for their recycling is crucial for sustainable development of new energy industry. Herein, a combined pyro - hydrometallurgical process was adopted for recovery of valuable metal elements for spent LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523). Different from conventional pyrometallurgical methods with high temperature and energy consumption, the NH₄HSO₄ roasting strategy works at 400 °C and achieves remarkable leaching efficiencies of Li, Co, Mn, and Ni achieved 97.5 %, 91.4 %, 91.3 %, and 95.50 %, respectively. Under the ideal conditions, abundant water-soluble metal-ammine-sulfates and metal-sulfates were revolved from NCM523. The process factors, including sulfation-roasting temperature, reagent mass ratio, roasting time, are intensively studied. Furthermore, a plausible reaction mechanism was deeply investigated with assistance of macro-micro scale, thermodynamic and kinetic analysis. Wherein, the Li of the NCM523 first react sufficiently with NH₄HSO₄ owing to higher thermodynamic/kinetic motivation at the primary stage during the sulfation-roasting procedure. Subsequently, the transition metal (Ni, Co, and Mn) from the lithium-depleted NCM523 would revolve to corresponding metal-ammine-sulfates or metal sulfates, and their sulfation-roasting kinetics conformed to the unreacted nuclear model. This study proposed an alternative green route of low energy consumption and acid-free procedure for recovering spent NCM batteries, which is conducive to industrial-scale recycling of waste LIBs in the future.

Recycling of spent lithium-ion batteries has attracted worldwide attention to ensure sustainability of electric vehicle industry. Pretreatment as an essential step for recycling of spent LIBs is critical to ensure the recovery efficiency and quality of black mass which is used for further materials regeneration. Usually, high temperature pyrolysis, at around 600 °C is required during the pretreatment to achieve effective separation of the black mass that is binding on aluminium foils with polyvinylidene fluoride binder. In this research, a low temperature and energy effective method is demonstrated by introducing a controlled frictional granulation in the subsequent step. With heat treatment at below 300 ℃, the oxidation of aluminium foil and generation of fluorine-containing waste gas can be highly supressed. As a consequence, the recovery rate of black mass can be increased to 98.80 % with only 0.05 % Al loss. Compared with the high-temperature pyrolysis and shear crushing methods, the energy consumption was significantly reduced by 48.74 %. Additionally, the proportion of aluminium particles below 75 μm was reduced from 12.6 % to 1.9 % comparing with traditional high temperature pyrolysis, which eliminates the possibility of explosion of aluminium particles. This research provides a low-carbon footprint strategy for treatment of complex electronic waste.