查看更多>>摘要：The combinatorial effects of slag composition and O-2-blowing conditions on silicon (Si) and iron (Fe) removal as well as gold (Au) and silver (Ag) enrichment from waste printed circuit boards (WPCBs) were investigated to optimize pyrometallurgical WPCBs recycling process. Regardless of the experimental conditions, the removal rate for Si and Fe was approximately 100%, except in slag-free operation. The Si removal rate was generally higher than the Fe removal rate at a given reaction time irrespective of experimental variables because the O-2 affinity of Si is higher than that of Fe in molten copper, thermodynamically. The removal rate of impurities was clearly dependent on blowing conditions and slag composition, and a combinatorial operation of bottom-blowing and highly fluid slag favored the efficient removal of impurities. The maximum enrichment ratio of Au and Ag (C-Au,Ag(Max)) was about 10% and the possession rates of Au and Ag, R-Au,R-Ag at C-Au,Ag(Max) were greater than 96%. The loss of Au and Ag can be minimized, i.e., R-Au,R-Ag can be maximized by stopping O-2-blowing before metal droplets are physically entrapped by molten slag, because metal droplet's entrainment is affected by slag viscosity, which contributes to the settling velocity of metal droplets. Consequently, it is very critical to appropriately control not only the slag composition but also O-2-blowing conditions for both impurities removal and maximizing precious metals enrichment and possession.
查看更多>>摘要：Urban symbiosis (UrS) is an innovative application of circular economy focusing on municipal solid waste (MSW). However, few studies have been conducted to forecast the impact of UrS on climate change under different MSW sorting policies such as four-category/two-category MSW separation standards and high/low sorting rates from a long-term and dynamic perspective. This study develops a system dynamics model to simulate the greenhouse gas (GHG) emission reduction potential and the energy saving potential of UrS under different MSW sorting modes in Shanghai for the period of 2020-2050. The results show that UrS with four-category MSW separation and a high sorting rate (scenario S1) has the highest energy saving and GHG reduc-tion potential at both annual level and accumulative level, approximately 10.75 times the energy saving and 146.30% of the GHG emission reduction compared with the Business-As-Usual (BAU) scenario in 2050. Mean-while, the scenario of two-category MSW sorting and a high sorting rate (S3) can further help reduce 12.84% GHG emissions than the scenario of four-category MSW sorting and low sorting rates (S2) in 2050. Among all the UrS measures, waste plastic recovery can contribute the most GHG emission and energy consumption reductions, with figures of approximately 2.15 Mt and 17.28 Mtce, respectively. Finally, policy recommendations on strengthening implementation of four-category MSW separation, making efficient two-category MSW separation as a backup plan, and promoting reutilization of waste plastic and Refuse Plastic & Paper Fuel technology are proposed.
查看更多>>摘要：The aim of this research was using a new chemical devulcanizing agent (i.e. VitaX) in devulcanization of NR/SBR blend as a model compound of tire rubber by microwave (MW) irradiation. For this purpose, the rubber com-pounds were prepared at different natural rubber (NR) to styrene butadiene rubber (SBR) ratios (40:60, 50:50, 60:40, 70:30 and 80:20). The rubbers were cured and then ground to particles with different mesh sizes (3, 4, 8, 16 and 30). The effect of irradiation time, stirring speed and particle size on sol/gel fractions, crosslink density (CLD) and devulcanization percent (DP) of the microwave irradiated samples was evaluated. Thereafter, effects of using VitaX and its content (0.3, 0.6, 1, 2, 3 and 4 phr) on devulcanized samples was evaluated. Results showed that using VitaX along with microwave irradiation caused decrease in the CLD and increase in the DP (from 9.51 to 34.85%) compared to the microwave assisted devulcanized samples. Finally, the raw NR/SBR rubber compound were replaced by different contents (10, 20 and 30 phr) of the chemical-microwave assisted devulcanized sample. The mechanical and curing properties of the samples were evaluated by tensile test and Oscillating Disk Rheometer (ODR), respectively. The results showed that at replacing content of 10 wt.%, decrement in the curing time and increment in the scorch time, cure rate index (CRI) and CLD was occurred in the re-vulcanized compound. The chemical-MW irradiation based devulcanization method was found to be a promising method for effective recycling of NR/SBR based rubbers such as tire rubbers.
查看更多>>摘要：In this study, the extraction of Cu2+ ions was carried out by the MDLM system, which is one of the bulky membrane techniques. The MDLM technique was used to investigate the transport of Cu2+ ions from an aqueous donor phase to an organic phase, and then from an organic phase back to an aqueous acceptor phase. D2EHPA dissolved in kerosene was used as a carrier. Determination concentration of Cu2+ metal ions in the donor and acceptor phases in the MDLM system was analysed using UV-vis spectrophotometer. The effects of the membrane's flow velocity, stripping solution concentration, and temperature on the transport of Cu2+ have been investigated, respectively. Under the optimum conditions, the transport percentage of Cu2+ was up to >99% during the transport time of 200 min when the initial concentration of Cu2+ was 280-300 mgL(-1). Kinetic parameters have also been calculated in order to identify the phenomena of extraction. The activation energy was calculated as 2.92 kcalmol(-1), which indicates that the extraction process for Cu2+ ions is controlled by diffusion. Experiments have shown that D2EHPA ligand dissolved in kerosene is a good carrier for the transport and extraction of Cu2+ metal ions using the MDLM technique in the study.
Roe, Brian E.Qi, DanyiBeyl, Robbie A.Neubig, Karissa E....
10页
查看更多>>摘要：There is growing concern whether pro-environmental behavioral interventions can generate sufficient reductions in carbon emissions to address climate change. While many have suggested enhanced tailoring of interventions to increase effect sizes, and while individual tailoring is common among health interventions, little is known about how individual tailoring may impact effect sizes for pro-environmental behavioral interventions. Using a novel technology-aided delivery and measurement approach, we conduct a randomized controlled trial featuring an individually tailored intervention focused on reducing the amount of food wasted by participants over approximately one week in their normal living conditions. We find large significant effects for the focal area of food wasted during dining (a 79% reduction), a null effect on food wasted over all household stages (preparation, dining and clean outs), and desirable or null effects for critical antecedent (e.g., waste during preparation, continued purchases of fresh produce), concurrent (e.g., food selection and consumption), and attendant behaviors (e.g., waste from storage clean outs, avoiding waste deposits in landfills).
查看更多>>摘要：The construction industry is facing a shortage issue of river sand, therefore broadening new sources of fine aggregate is imminent. This paper demonstrates the feasibility of a recycled sand from sandstone waste in mortar manufacturing by comprehensive assessment of workability, mechanical properties, water absorption, alkali silica reaction (ASR). The recycled sandstone sand (S-sand) has a smoother microscopic morphology and better particle size distribution than river sand (R-sand). Fine particles smaller than 150 mu m in R-sand usually contain a large amount of impurities (such as clay) and are considered harmful. However, the S-sand containing similar to 15.7% mu m quartz grains <150 mu m significantly improves the mortar performance in terms of compressive strength and ASR property. At the same water to binder ratio, the mortar using the S-sand shows worse workability than that using R-sand but a slight increase of water to binder ratio or adding water reducer improves not only the workability but also mechanical properties. For the ASR test, the S-sand shows potential uncertain risk as per ASTM C 1260. Using calcined clay or fly ash to replace 25% cement can effectively inhibit expansion risk. The compressive strength is reduced due to ASR, however, as the ASR progresses, it is somehow restored. This study also finds the good linear relationship between length change of mortar bar and mass change, which can be used to predict the sand ASR property. The results showed that S-sand produced by waste sandstone by-products can be used as high-quality fine aggregate.
Root, AndrewZamani, AkramWijayarathna, E. R. Kanishka B.Mohammadkhani, Ghasem...
11页
查看更多>>摘要：Food waste and fashion pollution are two of the most prominent global environmental issues. To alleviate the problems associated with food waste, while simultaneously contributing to sustainable fashion, the feasibility of making an alternative textile material with leather-like properties from fungal biomass cultivated on bread waste was investigated. The filamentous fungus, Rhizopus delemar, was successfully grown on waste bread in a submerged cultivation process, and fungal biomass was treated with vegetable tannin of chestnut wood. NMR and FTIR confirmed interactions between tannin and fungal biomass, while OM, SEM and AFM visualised the changes in the hyphae upon the tannin treatment. Thermal stability was assessed using TGA analysis. The wet-laid technique commonly utilised for paper-making was used to prepare sheets of hyphae. Some of the sheets were treated with glycerol and/or a biobased binder as post-treatment. Overall, three of the produced materials exhibited leather-like properties comparable to that of natural leather. Sheets from untreated biomass with only glycerol post-treatment showed a tensile strength of 7.7 MPa and an elongation at break of 5%. Whereas sheets from untreated biomass and tannin treated biomass with both glycerol and binder treatments led to tensile strengths of 7.1 MPa and 6.9 MPa, and the elongation at break of 12% and 17%, respectively. The enhancement of hydrophobicity after the binder treatment, helped to preserve the absorbed glycerol within the sheet and thereby the flexibility was retained when in contact with moisture. These findings demonstrate that bread waste derived fungal sheets have great potential as environmentally friendly materials with leather-like properties.
查看更多>>摘要：In the UK, half a million tonnes of spent coffee ground (SCG) waste are generated annually. Current SCG management practices of landfill and energy-from-waste (EfW) facilities either underutilise its valuable constituents or have negative environmental impacts. This study investigates the prospects of SCG-based biorefineries by assessing the impact of biorefinery size, location and products on economic and environmental performances. Two biorefinery design configurations are proposed. Configuration I produces biodiesel and electricity whilst Configuration II produces biodiesel and high-value chemicals. From these configurations, four biorefinery scenarios are analysed at a 10% discount rate with 2019 as the reference year. Configuration I using SCG from London coffee establishments yields a negative net present value (NPV) of -3.9 pound million and 22% greater greenhouse gas (GHG) emissions than conventional rapeseed biodiesel production. Changing the SCG source to a coffee factory increases biorefinery size by 2.3 times but still produces a negative NPV. Using Configuration II to process SCG from coffee shops significantly improves NPV. However, without on-site energy generation, its GHG emissions are greater than those from conventional production methods of the high-value chemicals. An on-site Configuration I using SCG from the coffee factory yields the best performance. It produces a NPV of 3.1 pound million and GHG emissions 85% and 13% lower than that of SCG landfilling and conventional biodiesel. Overall, these findings demonstrate the potential of extracting value from SCG waste using a biorefinery approach, revealing a strong likelihood that future SCG biorefineries will be large scale and on-site of SCG production.
查看更多>>摘要：Corporate social responsibility (CSR) has been touted as an important agenda among construction practitioners. Hitherto, the nexus between CSR and organizational performance is still a lack of investigation in the CSR in construction knowledge. This study explores the capabilities of various CSR practices toward achieving productive business benefits among construction firms. Firstly, a two-stage variable formulation procedure results in a list of practices and the perceived benefits of CSR. Then, we collected data from ninety extra-grade construction firms through an online questionnaire survey and analyzed data using a two-mode social network analysis approach. The results of the centrality analysis show that, with the highest centrality scores in the network, (i) the most influential CSR practices include such as "implement safety production management system" and "constrain consumption of materials and reduce material waste"; and (ii) the top key perceived benefits of CSR include such as "local and overseas business opportunities," "brand, image, and reputation," and "reduction of supply risk of building materials." The developed CSR practice-perceived benefit network presents a core periphery structure, with 26 practices and five perceived benefits situate in the core positions and have intensive relationships. Drawing upon the integrated stakeholder theory and the contingency resource-based view of firms, the demystified novel CSR resource collaboration network enriches the theoretical discourses of CSR by recognizing stakeholder salience and the need for relationship management. Practically, the findings of this study provide a helpful reference for practitioners to collaborate corporate resources, optimize their current CSR strategies, and improve business performance for sustainable development.
查看更多>>摘要：An innovative modelling framework and metrics are developed to assess the economic and environmental performances of regional incentives in the wood energy sector. Our approach is based on the coupling between a partial equilibrium economic model of the forest sector with Life Cycle Assessment (LCA). Its originality relies on the computation of regional eco-efficiency ratios while taking account of diverse direct and indirect spatial and market interactions. Several adaptations were implemented to ensure consistency between the two modelling approaches in terms of process yields and flow balances. These adaptations make it possible to produce both economic and environmental indicators with a consistent perimeter. Finally, we used two kinds of eco-efficiency indicators to compare bioenergy policies. On the one hand, Partial Eco-Efficiency (PEE) combines the economic surplus induced by an incentive on the energy wood sector with its potential environmental impacts. On the other hand, Full Eco-Efficiency (FEE) adds the environmental impacts avoided by substitution between wood energy and fossil fuels, compared to a business-as-usual (BAU) scenario. The proposed adaptations were applied to a case study in the French Grand Est region that compared the eco-efficiency of scenarios with or without a subsidy to wood energy consumption. Results show that subsidy increases the eco-efficiency of the forest-based sector using both PEE and FEE while keeping competition with the other regions to a minimum. However, most benefits come from the consideration of avoided impacts, with FEE far exceeding PEE. Using FEE, the scenario with the subsidy is 5% to 50% more eco-efficient than the BAU despite an increased consumption of wood products, due to economic gains and avoided impacts. These outcomes show the importance of considering potential trade-offs when assessing the economic and environmental performance of regional policies in favour of the bioeconomy.
NSTL
Elsevier