Flotation separation of acrylonitrile-butadiene-styrene and polystyrene in WEEE based on oxidation of active sites

Abstract

This work accomplished flotation separation of acrylonitrile–butadienestyrene (ABS) and polystyrene (PS) as well as further elaborating the mechanism of ABS hydrophilization under a novel modification by ClO2, with the help of contact angles, scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), high-resolution X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (NMR). All acrylonitrile, butadiene, and styrene were involved in a surface modification in the process of oxidation. The nitrile (CN) was hydrolyzed to the amide (OCNH2) and carboxyl (OCO). Mono-addition of hydroxyl groups (OH) introduced hydroxyl groups into monomers of butadiene and styrene. This work proposed that ABS oxidation was dependent on the active sites on the ABS surface rather than oxidizing agents. The active sites on the ABS surface were nitrile groups in acrylonitrile, carbon-carbon double bonds in butadiene, and α-hydrogen in styrene. The optimal pretreatment conditions for flotation separation of PS and ABS were the temperature of 70 °C, ClO2 dosage of 0.5 g/L, and treatment time of 60 min. The flotation percentage of ABS and PS were 3.3% and 96.4% with outstanding flexibility.