Flotation separation of acrylonitrile-butadienestyrene (ABS) and high impact polystyrene (HIPS) from waste electrical and electronic equipment (WEEE) by potassium permanganate surface modification

Abstract

The wasted acrylonitrile–butadienestyrene (ABS) and high impact polystyrene (HIPS) have a great potential for recycling. However, it is difficult to recycle them due to the absence of an effective separation method. Permanganate oxidation is a kind of environmental protection process and plays an important role in green chemistry. In this study, the polymer surface modification by potassium permanganate was utilized to separate ABS and HIPS from waste electrical and electronic equipment (WEEE) by flotation. Attenuated total internal reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) results showed that potassium permanganate can oxidize butadiene and nitrile groups in ABS to form oxygen-containing hydrophilic groups. Butadiene in HIPS can also be oxidized to form oxygen-containing hydrophilic groups, but the increase is less than that of ABS. Scanning electron microscope (SEM) results show that the surface roughness of ABS is improved, but HIPS has no obvious change, which indicates that the surface wettability of ABS can be further improved with the improved surface roughness. The contact angle test results show that the contact angle decrease of ABS after surface modification is significantly higher than that of HIPS. The results showed that the optimum modification conditions are as follows: the concentration of potassium permanganate solution is 50 mM/L, modification temperature of 60 °C, and the modification time 30 min. The recovery and purity of ABS are 97.64% and 95.41%, respectively, and the recovery and purity of HIPS are 95.40% and 97.64%, respectively. This research provides a technical support for the high-value recycling of WEEE waste plastic.