Separation of hazardous polyvinyl chloride from waste plastics by flotation assisted with surface modification of ammonium persulfate: Process and mechanism

Yingshuang Zhang; Hongru Jiang; Hui Wang; Chongqing Wang

doi:10.1016/j.jhazmat.2019.121918

Separation of hazardous polyvinyl chloride from waste plastics by flotation assisted with surface modification of ammonium persulfate: Process and mechanism

J Hazard Mater. 2020 May 5:389:121918. doi: 10.1016/j.jhazmat.2019.121918. Epub 2019 Dec 19.

Authors

Yingshuang Zhang¹, Hongru Jiang¹, Hui Wang², Chongqing Wang³

Affiliations

¹ College of Chemistry and Chemical Engineering, Central South University, Changsha, 410083, China.
² College of Chemistry and Chemical Engineering, Central South University, Changsha, 410083, China. Electronic address: huiwang1968@163.com.
³ School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou, 450001, China. Electronic address: zilangwang@126.com.

PMID: 31879107
DOI: 10.1016/j.jhazmat.2019.121918

Abstract

Plastic separation becomes an effective method to improve the plastic recycling by concentrating a single component from complex plastic mixtures. Based on advanced oxidation process, surface modification assisted by ammonium persulfate ((NH₄)₂S₂O₈) was applied to selectively wet plastic surface, achieving the separation of hazardous polyvinyl chloride (PVC) from acrylonitrile butadiene styrene (ABS), polystyrene (PS), and polycarbonate (PC) in forth flotation. The mechanisms were investigated through contact angle, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), as well as scanning electron microscope (SEM). The floatability of PS, PC, and ABS reduces owing to the introduction of carbonyl (O = CO), hydroxyl (-OH), and amide (O = C-NH₂) on plastic surfaces, which is the result of the oxidation by sulfate radical (SO₄^∙-) and the hydrolysis of nitrile group (CN) and butadiene (CC). Then, available reaction equations of ABS, PS, and PC were established to supplement the mechanisms of surface modification. The optimal conditions for flotation separation of PVC are (NH₄)₂S₂O₈ concentration 0.2 M, temperature 70 °C, pretreatment time 30 min, pH 10, flotation time 4 min, terpineol dosage 20 mg/L, and particle size 3-4 mm. The recovery and purity of PVC reach 100 % and 99.7 ± 0.2 % respectively, favoring the reuse of separated waste plastic.

Keywords: Advanced oxidation; Ammonium persulfate; Hazardous plastic; Plastic flotation; Surface modification.