Study On The Collecting, Recycling And Pollutants Release Of Typical Waste Home Appliances

Waste electrical and electronic equipment?WEEE?is an important part of solid waste.From the viewpoint of resource reuse,WEEE is considered as"urban mine"possessing the important value for recycling,as it can provide generous amounts of reusable metal,plastics,glass and other secondary resources;from the viewpoint of environmental protection,WEEE contains different kinds of hazardous substances,including heavy metals and brominated flame retardants,and so on.The recycling process will lead to the release and migration of the contaminants,and cause environmental pollution in and around the plant.Therefore,it is of practical significance and theoretical value to study the collecting system with high efficiency,recycling technologies and pollution release characteristics during recycling process for WEEE.Firstly,in view of the scattered sources,wide distribution and hard collecting of WEEE,based on the intelligent service platform for recycling bins,mobile terminal and recycling branches,the networking information sensing technologies such as radio frequency identification and bar code management,combining with the logistics tracking and visualization for transporting goods and vehicle,are used to construct the intelligent logistics system for WEEE,achieving the intelligent collecting of WEEE.Secondly,according to the properties of material in various types of waste household appliances,several production lines consisting of crushing,separating and purifying facilities and equipmente were installed for separation and resourecs recovery in the scrap TV,waste refrigerators,waste cathode ray tube?CRT?display and waste printed circuit board?WPCB?,through the combination of manual disassembly,mechanical crushing,and composite separation?wind,eddy current,high-voltage electrostatic separation,etc.?.Thirdly,the collected household appliances were recycled by mechanical-physical method,and the pollution characteristics(concentration levels,distribution characteristics and migration and releasing mechanisms of noise,atmospheric particulate matter?PM?,heavy metals and polybrominated diphenyl ethers?PBDEs?during the recycling process.The main results are as follows:?1?the mechanical crushing and cutting processes of WEEE were the main sources of noise pollution.Through the installation of acoustic hood outside the equipment,the noise,dust and other pollutants CFC-11 can be blocked effectively by the acoustic hood;?2?the recycling processes for waste household appliances caused the PM pollution in different workshops,and the mass concentrations of PM₁₀ and TSP in the TV dismantling workshop were the highest.The characteristics of heavy metals in PM varied in different workshops,and related with the particle size of PM,the components of dismantling or processing objects.The content of Pb in PM_2.5,PM₁₀ and TSP were relatively high,and the concentration of Pb in the CRT processing workshop was highest;?3?the concentrations of Pb and Cu in the floor dust of workshops and internal dust insides the household applicances were relatively high,followed by Ni>Cr>Cd.The Pb concentration of floor dust in the WPCB heating pretreatment workshop,and Cu concentration of floor dust in the WPCB recycling workshops were the highest;?4?PBDEs pollution was generated during the WEEE recycling processes,including TV manual disassembly,WPCB heating processing,WPCB crushing-separating and plastic crushing.The?₁₂PBDEs concentration in air samples?both particulate and gaseous phases?in the plastic crushing workshop was the highest,and BDE-209 was the main BDE congener.The?₇PBDEs in gaseous phase in the WPCB heating pretreatment workshop was the highest,and BDE-28,-47 and-99 were the main congeners;?5?a large number of penta-BDE were released during the WPCB artificial baking and mechanical baking processes.The PBDEs concentration of dust collected from the cyclone extractor in the mechanical baking production line were the highest.For artificial baking process,fume generated from WPCB baking were discharged after treatment treated,and the?₆PBDEs concentrations were reduced from 7440 pg/m³?inside the hood?to 416pg/m³?discharge gas?.It was estimated that the emission factor for WPCB artificial baking process was 47.3 ng·?₆PBDEs/kgWPCB.?6?PBDEs heating simulation experiments:the release characteristics of PBDEs from the heating of dust samples collected from cyclone extractor?CE-Dust?were affected by the temperature.The higher the temperature was,the faster the PBDE emission rate was.At the temperature of 300°C,the PBDEs emission from dust mainly occurred within the first 5 min,and the emission rate of PBDEs decreased dramatically after 15 min.The release amounts of BDE congeners were BDE-47>BDE-99>BDE-28.The trends of PBDEs emission from WPCB fragments had a linear increase,and the accumulated PBDEs from WPCB fragments was less than from CE-Dust during the initial 1-h period.Finally,environmental risk assessment showed that the hazard index?HI?for Pb in PM from the TV dismantling workshop,WPCB recycling workshop and CRT recycling workshop were higher than 1,and the exposure pathways was:ingestion>dermal contact>inhalation,suggesting the existence of non carcinogenic risk.There was no non-carcinogenic and carcinogenic risk for Cr,Ni and Cd in PM.The exposure of BDE-47and-99 in the WPCB heating pretreatment workshop were the highest,reaching 0.118 and0.0544?g/kg/day,which were higher than or close to the reference dose of 0.1?g/kg/day.The exposure of BDE-209 in the plastic crushing workshop was the highest?0.744?g/kg/day?,but less than the reference dose?7?g/kg/day?.