Microwave treatment combined with wetting agent for an efficient flotation separation of acrylonitrile butadiene styrene (ABS) from plastic mixtures

Abstract

Acrylonitrile butadiene styrene (ABS), as a main component of plastics of waste electrical and electronic equipment (WEEE), shows high potential for recycling, which is restricted by the absence of an efficient separation method. Herein, a novel surface treatment method, microwave treatment combined with a wetting agent, was proposed to selectively change the hydrophilicity of the mixed waste plastics, which efficiently separated ABS from the WEEE plastics by flotation. The results of this approach provided the following optimal conditions, i.e., microwave power 700 W, microwave irradiation time 3 min, concentration of wetting agent carboxymethylcellulose sodium (CMC) 25 mg/L, treatment time with CMC 5 min, stirring rate 1800 rpm, frother concentration 40 mg/L, and flotation time 4 min. Under these optimal conditions, the recovery and the purity of ABS reached 97.70% and 99.86%, respectively. The mechanism of the surface treatment was examined by means of contact angle, Fourier transform infrared spectroscopy (FT-IR), and adsorption kinetics. The results showed that the selective wetting mechanism can be attributed to the physisorption of CMC on the surface of plastics. In conclusion, this surface treatment method is expected to provide technological insights for the separation and recovery of waste ABS from WEEE plastics.