Waste management最新文献

Although diamond wire saw silicon powder (DWSSP) represents a valuable silicon resource, its high-purity recovery is significantly hindered by a surface oxide layer (SiO₂) and metallic contaminants (Al, Fe, Ni). Current recycling strategies face challenges in achieving high silicon recovery percentage while simultaneously eliminating multiple impurities. In this study, a chlorination refining process utilizing a BaCO₃-NaCl system is proposed to simultaneously eliminate SiO₂, Al, Fe, and Ni. Thermodynamic calculations were performed to predict the reaction behaviors of impurities, followed by experimental validation to assess the impurity removal efficiencies and silicon recovery percentage. Thermodynamic analysis indicates that BaCO₃ initiates the reaction with SiO₂ at 600 K, making the removal of the oxide layer theoretically feasible. As the temperature increases to 1100 K, BaCl₂ and Na₂O are formed as intermediate products of the interaction between BaCO₃ and NaCl, and at 1800 K, BaCO₃ decomposes into BaO. SiO₂ can react with Na₂O and BaO respectively, while Al₂O₃ can react with BaCO₃, Na₂O, and BaO respectively. Experimental results demonstrate that under the optimal weight ratio of DWSSP : BaCO₃ : NaCl 100: 7.38: 10, the silicon recovery percentage reaches 93.10%. Simultaneously, significant removal efficiencies for Al, Fe, and Ni impurities are achieved at 75.00%, 91.01%, and 78.66%, respectively. This study confirms that the proposed BaCO₃-NaCl refining strategy effectively facilitates the simultaneous deep removal of oxide and metallic impurities. It offers a technically feasible and high-recovery solution for the value-added recycling of DWSSP waste.

While applying animal manure remain widespread agricultural practices for resources recycling, it risks unintentionally transferring antibiotic-resistant bacteria and antibiotic resistance genes (ARGs) from manure to soils. Despite the recognized environmental implications, limited research has systematically investigated the risk characteristics of ARGs linked to the combined application of manure as base fertilizer and routine irrigation practices. The question of which practice, fertilization or irrigation, more significantly contributes to the spread of ARGs remains unresolved. To bridge the gap, this study comprehensively investigates the characteristics and dissemination risks of ARGs in agricultural soils treated with chicken/cattle manure fertilization alongside groundwater irrigation. The characteristics, differences, and interactions among the resistome, microbiome, mobilome, and virulome across irrigation systems are systematically analyzed and compared. A novel non-negative matrix factorization-based microbial source tracking approach, NMF-SourceID, with superior accuracy in tracking low-abundance sources is used to quantify the source-sink relationship of ARGs in irrigated agroecosystems. The results revealed that combined fertilization and irrigation significantly enhanced both the abundance and diversity of ARGs in agricultural soils (p < 0.05). Importantly, these practices increased environmental risks by introducing emerging ARGs, mobile genetic elements, opportunistic human pathogens, virulence factors, and promoting their ecological co-occurrence. Comparative analysis showed no significant difference (p > 0.05) in ARG levels between chicken manure-treated strawberry soils and cattle manure-amended wheat cultivation soils. Source apportionment indicated that irrigation contributed 16-26% of ARGs while manure contributed 2.7-3.8%, suggesting the impact of base fertilizer on the dissemination of ARGs is much smaller than that of irrigation. The findings of this study provide essential theoretical groundwork for guiding agricultural fertilization and irrigation practices to mitigate environmental risks associated with antibiotic resistance dissemination in agroecosystems.

Thermal treatment of Municipal Solid Waste in Energy-from-Waste (EfW) facilities enables energy recovery and landfill reduction but generates hazardous air pollution control residues (APCr). This study characterised 42 APCr samples from 22 UK EfW facilities, integrating compositional, mineralogical, leaching organic fraction and microstructural analyses to assess environmental implications. Scanning Electron Microscopy - Energy Dispersive X-Ray Spectroscopy (SEM-EDS) identified major elements (>0.1 wt%): O, Ca, Cl, Si, Al, Mg, Fe, K, Na, P, S and Zn. Inductively Coupled Plasma - Optical Emission Spectroscopy quantified total metal concentrations (mg/kg): Zn (>1,000), Cu and Pb (>100), As, Ba, Cd, Cr, Ni and Sb (< 1,000) and Mo (<100). X-Ray Diffraction identified 45 mineral phases, including 21 newly reported in APCr. Dominant phases comprised CaSO₄, CaCO₃, CaOHCl, Ca(OH)₂, NaCl, KCl and SiO₂, alongside Si-bearing phases, such as clinotobermorite (Ca₅H₈O₂₁Si₆) and sanidine (KAlSi₃O₈). Leaching tests showed environmental risks from Pb, Ba, Mo, Cr, Zn, Cu, chlorides and sulphates, with Pb and chlorides mostly exceeding hazardous Waste Acceptance Criteria (WAC). Organic indices showed Total Organic Carbon predominantly undetected, Loss on Ignition mostly below hazardous WAC and Dissolved Organic Carbon absent in most leachates, indicating that organics largely remain within the solid phase. SEM imaging revealed fine-grained material (0.1-1 µm), diverse particle morphologies and inclusions of unburnt organics, carbon and metals. Findings inform APCr treatment strategies for safe handling, recycling and resource recovery.

This study presents a techno-economic assessment of Hydrothermal Carbonisation (HTC) and Struvite Precipitation (STR) for dairy processing sludge (DPS), focusing on energy and cost performance across five system scales (2500-50,000 t/year). A dual approach was employed: a deterministic analysis using fixed input values, and a stochastic Monte Carlo simulation to assess uncertainty in key market and operational parameters. The results demonstrate that larger systems benefit from economies of scale, with lower per-unit costs. However, diminishing returns at larger scales highlight the need to balance technology design, processing scale, product valorisation, operational costs, and logistics. A sensitivity analysis reveal that gate fees, market prices for bio-based fertilisers and thermal energy fluctuations are critical variables influencing profitability. For Scale 3 (10,000 t/year) a reasonable balance between energy efficiency, cost-effectiveness, and logistical feasibility was observed. Still, the model showed susceptibility to market volatility, underlying the importance of adaptable strategies to mitigate financial risks and ensure system resilience in HTC systems. This research contributes to the circular economy literature, providing a transparent and adaptable framework for evaluating bio-based technologies under operational and market uncertainties. Future work should explore different reactor configurations, regional feedstock availability, and site-specific conditions to further validate and refine the system feasibility.

CO₂ mineralization technology provides a technically feasible strategy to achieve the high-value recycling of waste concrete as a carbon sink, aiming to achieve the carbon neutrality goal in the construction sector. In this study, CO₂ mineralization technology was harnessed to enhance recycled aggregate (RA) and recycled powder (RP) to fully replace natural aggregate (NA) and partially replace cement, thereby developing carbonated recycled aggregate concrete incorporating carbonated RP (CRAC-CRP). The results show that the physical and mechanical properties of RA were enhanced after CO₂ mineralization due to the reduction of porosity and the refinement of pore size. Furthermore, CRAC-CRP achieved 90-day compressive strength within ∼7% of natural aggregate concrete, together with a ∼16% strength gain from 28 to 90 days. Additionally, CRAC-CRP showed 4.5% lower water absorption and 24.7% lower chloride migration coefficient than recycled aggregate concrete at 90 days. Under chloride exposure, CRAC-CRP maintained more positive open-circuit potential and higher polarization resistance for 200 days, whereas depassivation occurred after 105-180 days in mixes without carbonated constituents. A cradle-to-gate life cycle assessment indicated up to a ∼33% reduction in CO₂ emissions and ∼28% lower carbon intensity, together with ∼25% reduced production cost, confirming both environmental and economic advantages of this approach.

In the European Union, between 14 and 18% of current passenger cars are made of plastic materials. Despite all advantages that plastics bring to the production of vehicle components, there are also decisive disadvantages at the vehicle's end-of-life. Plastics end up as automotive shredder residues and are mainly utilized thermally as refuse-derived fuels. Mechanical recycling of automotive plastics from end-of-life vehicles is not common practice. We assessed the circularity potential of plastics in passenger cars through mechanical recycling of automotive shredder residues. We developed a sensor-based sorting process to separate polypropylene, polyamide, polycarbonate, and acrylonitrile butadiene styrene. Our process yields a 13.3% recovery rate for thermoplastics from end-of-life vehicles. 26.1% polypropylene, 31.2% polycarbonate, 5.3% acrylonitrile butadiene styrene, and 22.1% polyamide were recovered. We developed a dynamic simulation model to theoretically extrapolate those results and calculate the closed-loop recycled content of plastic in new cars from post-consumer end-of-life vehicle waste. We simulated total and polymer-specific closed-loop rates for six scenarios and performed a sensitivity analysis. In our MIX scenario, a closed-loop recycled content rate of 3.1-4.8% can be reached in 2035, based on our study setting. An environmental assessment shows that our developed sorting process results in 29.5% lower greenhouse gas emissions than the usual incineration of the automotive shredder residues sorted. Although additional efforts will be required to effectively close material loops for plastics in the automotive sector, our results indicate the technical potential of concentrating polymers from automotive shredder residue to contribute to meeting closed-loop recycled content quotas.

Under the dual impetus of the sustained improvement of the Chinese economy and the accelerating urbanization process, domestic demand and consumption of coal have maintained a steady growth trend. Consequently, the production and stockpiling of coal combustion byproducts, particularly coal fly ash (CFA), have increased remarkably, while its comprehensive utilization has seen limited improvement in recent years. Containing approximately 30%-60% SiO₂, CFA represents a significant resource for silica recovery and purification to enable high-value applications. This study employed a thermal phase separation-acid leaching method to remove metal oxides and purify SiO₂ from CFA, utilizing B₂O₃ as a phase-separation agent. The research systematically investigated the optimal process parameters for CFA phase separation and metal removal, while elucidating the underlying mechanisms of phase separation and metal migration. Experimental results demonstrated that under optimal conditions (B₂O₃ addition: 25 wt%, temperature: 1100 °C, holding time: 1 h) the removal efficiency of metal oxides exceeded 95%, yielding a high-silica product with a purity of 97.22%. Complementary molecular dynamics (MD) simulations provided atomic-scale insights into the SiO₂-B₂O₃ phase separation process. Analysis of the root mean square deviation (RMSD) of atomic coordinates and radial distribution functions (RDFs) for Si and B atoms confirmed that phase separation occurred rapidly within the high-temperature regime during cooling, following complete melting and homogenization. This work provided a novel approach for the resource utilization of CFA.

The solvent-targeted recovery and precipitation (STRAP™) process separates polymers from contaminants present in the feedstock. In this work, we demonstrate the recyclability of a post-consumer waste (PCW) shrink wrap that contains inks, adhesives, and paper using STRAP. We produced a clear rPE cast film from the PCW shrink wrap with no visual contamination from paper or inks. STRAP decreased the ash content from 0.96 wt% to 0.24 wt%. A techno-economic analysis (TEA) shows that a STRAP plant processing 50,000 metric tons annually of shrink wrap waste (purchased at $0.25/kg) containing 85 wt% PE can achieve an IRR of 16.2% when selling rPE at $1.30/kg, an IRR of 10.7% with an rPE price of $1.00/kg, or an IRR of 3.79% with an rPE price of $0.70/kg. The life cycle assessment (LCA) shows a 64% reduction in global warming potential (kg CO₂ equivalent) when compared to the production of virgin LDPE. This work shows how feedstocks with insoluble impurities can be recycled using STRAP on a large scale.