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[Objective] In the context of compulsory classification, different source separation and collection methods will change the flow direction of municipal solid waste and the subsequent collection and disposal process, and then affect the life cycle carbon emissions and economic performance of the recycling system. According to the different scenarios of Beijing community garbage source classification and comprehensive treatment system, this study carried out carbon reduction efficiency analysis and optimization, in order to provide a scientific basis for the establishment of garbage classification and collection model according to local conditions. [Methods] The material flow analysis method (MFA) was used to analyze the material flow direction and flow in the whole process of recycling and treatment, and evaluated the carbon footprint and economic cost respectively with life cycle carbon emission accounting (LCCA) and life cycle cost analysis (LCC) methods. On this basis, a carbon reduction efficiency index was put forward and optimized. [Results] The life cycle carbon emissions of the baseline scenario (S1) and the optimization scenario (S2-S5) are -148.14 kgCO2e, -236.44 kgCO2e, -251.25 kgCO2e, -297.06 kgCO2e, -343.51 kgCO2e, respectively. Compared with S1, the four optimization scenarios show positive carbon reduction efficiency, and the carbon reduction efficiency values are S5 (2.20)>S4 (1.66)>S3(1.38)>S2 (1.31). Scenario 5 corresponding to the “garbage sorting station+recyclable intelligent recycling bin+garbage classification instructor” optimization model has the highest carbon reduction efficiency. Under the premise that the comprehensive treatment capacity of domestic waste and the treatment capacity of each component are sufficient, with the increase of the proportion of accurate classification, the carbon reduction efficiency is gradually improved. [Conclusion] The establishment and improvement of the source separation and collection system increases the front-end infrastructure operation cost, labor cost, and environmental impact, but effectively improves the back- end classification and treatment efficiency and the output rate of renewable resources, resulting in the improvement of life cycle carbon emission reduction benefits. With the increasing participation rate and accuracy of domestic waste classification in the future, the cost in the collection stage will be greatly reduced, and the carbon reduction efficiency can be further improved.

Waste light-emitting diodes (LEDs) contain rare and precious metals which have attracted wide attention due to their high resource. In this study, experimental research was conducted on the separation and recycling of Au and Ag from LEDs. Firstly, thermal treatment and sieving were done to separate and enrich the metals in LEDs. With the constant heating rate of 10°C/min to 450°C under air atmosphere, the metals could be effectively separated from organics and the rare metals Au and Ag mainly concentrate in particles with a diameter ≤600 μm, whose concentration is about 1816 and 1429 mg/kg, respectively. Then, a mix-acid system of HCl-CH3COOH was introduced to leach Au and Ag from the enriched sample. The results show that the HCl-CH3COOH system could effectively leach Au and Ag, and the leaching performance of Au and Ag can reach 95.4% and 96.2%, respectively under the recommended conditions (total acid concentration 5 mol/L, HCl:CH3COOH = 4:1, leaching temperature 80°C, solid–liquid ratio 1:100, leaching time 5 h). The study can provide a new option for recycling of waste LEDs, which also provide a more environment-friendly method for Au and Ag leaching from industrial wastes. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are a kind of emerging pollutants, which have diversified sources, wide distribution, high abundance and great potential harm, and have been included in the key control list of emerging pollutants by Shanghai. MPs in water environment can adsorb heavy metals and organic pollutants, and the adsorption capacity is affected by MPs type, particle size, aging degree and environmental conditions. As a carrier, MPs can carry inorganic or organic pollutants into organisms, change the concentration and distribution of pollutants in organisms, and affect the toxic effects of pollutants. The type of combined action between MPs and chemical pollutants varies with the types of pollutants, and its specific mechanism remains to be further investigated. Therefore, this paper reviewed the latest development of domestic and foreign literatures, systematically summarized the sources and current status of MPs pollution in soil and freshwater environment in China, analyzed the adsorption behavior of MPs to chemical pollutants, the influencing factors of adsorption and the combined toxic effects of MPS on organisms, and prospected the future development direction of related researches. [ABSTRACT FROM AUTHOR]

Under the background of waste-sorting, the recycling system of recyclable waste in Shanghai has gradually improved, and the recycling of household plastics has been greatly improved. Based on the on-site research and the statistical data analysis, the current collection status of household plastic and recycling technology in Shanghai was analyzed in this paper. The dominant types of recycled waste plastics were PET and PP, accounting for 45.3% and 30.7% of the total recycling plastics, respectively. Besides, there are nearly 30% of the plastics with recycling value wasn't recovered, which are mainly PP and PET. Thus, to promote the development of plastic recycling from household waste, it is recommended to establish recycling standard and to improve subsidy policies, as well as to promote recycling technology innovation, public education and supervision strengthen in the near future. [ABSTRACT FROM AUTHOR]