Feasibility of using waste polystyrene as a membrane material for gas separation

Abstract

An alternate reuse route for recycling plastic solid waste (PSW) was successfully developed in this study. Polystyrene (PS) waste was directly re-used as a material for gas-separation membranes using a solution-casting method. The waste materials comprise three types: (1) oriented polystyrene (OPS), (2) expandable polystyrene (EPS), and (3) high-impact polystyrene (HIPS); these were investigated through proximate analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The waste materials have the same composite and thermal properties as the raw materials except for waste EPS, which contains a partially broken molecular chain. Thus, besides the waste EPS, the waste PS-derived membranes were homogenous and symmetrical. The gas permeation performances of the membranes were measured using the time-lag method at different operating pressures. The results showed that the performances of the waste PS- and raw PS-derived membranes are similar. Meanwhile, a HIPS membrane containing butadiene rubber exhibited high CO2 plasticization resistance at high pressure with a CO2 permeability of 67Barrer and CO2/N2 selectivity of 10–11 at an operating pressure of 5atm. Therefore, the novel reuse route of PS waste is feasible as an economically and environmentally friendly method for disposing PSW.