Abstract
This paper describes a study for waste of electrical and electronic equipment (WEEE) to characterise the plastic composition of different mixed plastic fractions. Most of the samples studied are currently excluded from material recycling and arise as side streams in state-of-the-art plastics recycling plants. These samples contain brominated flame retardants (BFR) or other substances of concern listed as persistent organic pollutants or in the RoHS directive. Seventeen samples, including cathode ray tube (CRT) monitors, CRT televisions, flat screens such as liquid crystal displays, small domestic appliances, and information and communication technology, were investigated using density- and dissolution-based separation processes. The total bromine and chlorine contents of the samples were determined by X-ray fluorescence spectroscopy, indicating a substantial concentration of both elements in density fractions above 1.1 g/cm3, most significantly in specific solubility classes referring to ABS and PS. This was further supported by specific flame retardant analysis. It was shown that BFR levels of both polymers can be reduced to levels below 1000 ppm by dissolution and precipitation processes enabling material recycling in compliance with current legislation. As additional target polymers PC and PC-ABS were also recycled by dissolution but did not require an elimination of BFR. Finally, physicochemical investigations of recycled materials as gel permeation chromatography, melt flow rate, and differential scanning calorimetry suggest a high purity and indicate no degradation of the technical properties of the recycled polymers.
Highlights
Besides design for recycling and design from recycling, collection, sorting, and recycling of plastics are major pillars to move our current value chains towards a circular economy of waste of electrical and electronic equipment (WEEE) plastics [1,2]
More than 72% end up in density fractions 3 and 4. This demonstrates that an effective separation of halogenated and nonhalogenated plastics is possible via density separation
Three target polymers were recovered in our study from different WEEE sources by a combination of density separation and subsequent dissolution
Summary
Besides design for recycling and design from recycling, collection, sorting, and recycling of plastics are major pillars to move our current value chains towards a circular economy of WEEE plastics [1,2]. Density-based technologies, have great potential in separating BFR containing plastics but show limitations when dealing with different polymers with similar densities, such as ABS and HIPS. A great share of WEEE plastics ends up in the high-density rejects of such separation plants They contain multiple polymer types and BFRs, including PBDE and TBBPA, making this material a hazardous waste and suggesting thermal destruction. There is no known single process technology that tackles both challenges In our study, these fractions were subjected to the dissolution-based CreaSolv® Process to extract target polymers like PS, ABS and PC/ABS and to separate BFRs. The study is part of the European NONTOX project (www.nontox.eu [accessed on 2 May 2021]) and has been supported by industrial project partners operating WEEE plastics plants. They provided us with a large number of 17 different samples from WEEE, ICT, SDA, CRT, and flat screens
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