Decomposition of polycarbonate/acrylonitrile-butadiene-styrene blends in e-waste packaging resin and recovery of debrominated carbon materials by supercritical water oxidation process

Abstract

Polycarbonate/acrylonitrile-butadiene-styrene blends (PC/ABS) has become one of the most common polymer insulation materials as packaging resin in electronics industry, due to its excellent mechanical, flame retardant and insulating properties. Once electronic products are eliminated and discarded, refractory PC/ABS will become a huge obstacle to e-waste recycling. Conventional solid waste treatment methods may lead to the release of toxic organobromine compounds and endocrine interferons, posing a threat to the environment and human health. In this study, supercritical water oxidation (SCWO) process was applied to decompose PC/ABS as e-waste packaging resin. The results showed that waste PC/ABS could be environmentally friendly and efficiently decomposed and debrominated during SCWO process. The decomposition mechanism could be proposed as depolymerization, generation of free radicals, conjugation of free radicals and carbonization. The debrominated products such as carbon materials, small molecular weight hydrocarbons, carbon dioxide and water were obtained and could be recycled as chemical feedstocks. The optimum SCWO parameters were temperature of 500 °C, holding time of 90 min, pressure of 23 MPa, and excess oxygen of 100%, respectively. The maximum weight loss rate and debromination rate of waste PC/ABS were 78.57% and 99.62%. Thus, the process developed in this study provided a green and sustainable approach for disposal of e-waste packaging resin.