Surface treatment using potassium ferrate for separation of polycarbonate and polystyrene waste plastics by froth flotation

A novel surface treatment method, potassium ferrate (K2FeO4) treatment, was developed to induce surface modification of plastics and facilitate separation of polycarbonate (PC) and polystyrene (PS) waste plastics by froth flotation. Contact angle measurements suggest the decrease in the floatability of PC is attributed to the increase of surface wettability. FT-IR and XPS analysis confirm that hydrophilic oxygen-containing groups are introduced on PC surface. SEM measurements indicate that the surface roughness of PC is also enhanced obviously. Evaluation of reusing of treatment effluent and flotation effluent was also investigated. Concerning on flotation separation of PC and PS, optimum conditions of potassium are ferrate concentration 10 mM/L, treatment time 20 min, temperature 60 degrees C, stirring rate 200 rpm, frother concentration 15.8 mg/L, flotation time 1 min and airflow rate 7.2 mL/L. Under optimum conditions, plastic mixtures of PC and PS with different mixing ratios can be separated efficiently. The purity of PC and PC reaches 100% and 99.54%; the recovery of PC and PS reaches 99.78% and 100% respectively. Reusing of treatment effluent and flotation effluent is feasible, indicating this method is cheap and environmentally friendly. (C) 2018 Elsevier B.V. All rights reserved.