An Efficient Strategy Based on Hyperspectral Imaging for Brominated Plastic Waste Sorting in a Circular Economy Perspective

Plastic is one of the materials mostly used in many industrial sectors, as those of packaging, construction, agriculture, etc. Furthermore, polymers are also extensively used in electrical and electronic equipment (EEE) manufacturing. Plastic waste originating from EEE (WEEE) is a challenge for recycling due to presence of various hazardous elements (i.e. additives) representing a polluting source for the environment and a risk factor for the human health. Among these, there are those containing brominated flame retardants (BFRs), largely utilized to increase fire resistance, avoiding or delaying the flames, thus allowing to the plastics-based-manufactured-products to respect safety requirements. However, plastics with high BFRs levels cannot be recycled and therefore must be removed from the recycling stream. In a circular economy perspective, it is thus necessary to develop a system able to efficiently separate plastic waste into homogeneous fractions based on the BFRs content. To improve the circularity of plastics, it is thus essential to recover and recycle bromine-free plastics to avoid the loss of available secondary raw materials. The aim of this study was to develop an efficient, reliable and sustainable approach based on hypeispectral imaging (HSI) operating in SWIR range (1000-2500 nm) coupled with chemometrics, specifically addressed to identify plastics containing BFRs. In order to investigate the possibility of reliable sorting, plastic scraps from cathode ray tube with different contents of BFRs were investigated. The concentration of bromine per scrap was preliminary measured by X-ray fluorescence in order to validate the results obtained by HSI. The recyclable low-bromine fraction was successfully identified using the developed strategy based on HSI.