The widespread utilization of plastic materials across various industrial sectors drives a continuous increase in global polymer demand. The exponential production growth generates severe environmental challenges regarding municipal solid waste management, as substantial fractions of post-consumer residuals enter landfills due to limited recycling infrastructure. Mitigating the global environmental burden requires the implementation of advanced recovery strategies to transition polymer waste into viable secondary feedstocks. Consequently, deploying efficient sorting techniques constitutes a fundamental requirement to integrate plastic materials into formal waste management protocols and optimize recycling yields. Technological innovations currently drive the transition from traditional manual segregation towards highly sophisticated automated sensor-based sorting architectures, maximizing separation efficiency. In this context, the present study comprehensively reviews pretreatment classification techniques engineered to fractionate heterogeneous waste streams into high-purity material flows. Rather than restricting the analysis to polyolefins, this review encompasses a broad spectrum of commodity polymers predominantly found in urban solid waste environments.

The widespread utilization of plastic materials across various sectors has led to significant increase of plastics demand over the decades. This growth has been accompanied by a mounting challenge related to managing of generated plastic waste, as substantial portions of the plastic residual end up in landfills due to limited recycling efforts. Addressing this global concern demands the development of innovative strategies to better assess and recover polymer waste, which should be treated as a different feedstock. In order to do that, efficient sorting techniques are crucial to integrate valuable materials like plastics into municipal solid waste management and improve recycling outcomes. As a matter of fact, technological innovations in this area have given rise to more sophisticated sorting methods, exploring automated sorting techniques to enhance recycling efficiency. Nevertheless, among traditional and modern sorting approaches, manual strategies are still used to perform plastic waste segregation. In this context, the present study aims to comprehensively review and assess pre-treatment classification techniques employed to transform waste streams into valuable compounds, specifically focusing on polyolefin materials present in large quantities in urban solid waste treatment environments.

This study investigated the chemical recycling of poly(ethylene terephthalate) (PET) fiber residues from two sources—high-molar mass mooring ropes and low-molar mass textile-grade fibers—to produce functional oligomers. Glycolysis was carried out using polyethylene glycol (PEG400) as the depolymerizing agent, and two catalysts were assessed, zinc acetate and lithium octoate, with the latter reported on for the first time in this application. Reactions were performed for 180 min under mechanical stirring, inert atmosphere, reflux, and controlled heating. The resulting oligomers were characterized by Fourier-transform infrared spectroscopy (FTIR), hydroxyl and acidity indices, and thermogravimetric analysis (TGA). Both PET feedstocks showed high reactivity toward glycolysis. Monitoring the reactions by acidity index indicated that conversion reached equilibrium at approximately 120 min. ATR-FTIR confirmed the formation of ester and hydroxyl groups, consistent with oligomer structures. Glycolysis of PET derived from mooring ropes produced oligoesters with hydroxyl values of 228 and 242 mgKOH/g for zinc acetate and lithium octoate, respectively, and molar masses of 1296 and 1338 g/mol for zinc acetate and lithium octoate, respectively. These values are suitable for subsequent syntheses such as polyester polyol production.