Electrospun PAN-PS membranes with improved hydrophobic properties for high-performance oil/water separation

Abstract

In this study, pure polyacrylonitrile (PAN) and waste polystyrene (PS) foams were used together for the production of membranes. Fumed silica (FS) was added to the prepared electrospinning solutions to increase the surface hydrophobicity, and the hydrophobic properties of the obtained membranes were confirmed by water contact angle (WCA) measurements. The surface hydrophobicity of the membranes increased with the addition of FS (0.5–1.5 % wt.) to the polymer solution, and the WCA increased from 104° to 128°. Scanning electron microscopy (SEM) and Fourier Transform Infrared (FTIR) analyses were carried out to define the structural and morphological characteristics of the produced membranes, while Gel permeation chromatography (GPC) analysis was carried out to determine the molecular weight of the employed waste PS foam. SEM analysis revealed that the produced membranes had an almost bead-free structure and were quite homogeneous with a fiber structure extended into each other. In the tests carried out to compare the oil removal performance of the membranes, the permeability flux of the PAN/PS/FS-0 membrane was calculated as 534.96 Lm−2h−1 in the system where only gravity is effective. On the other hand, the permeability flux value for canola oil–water mixtures in the forced system using PAN/PS/FS-1.5 membrane was calculated as 613.43 Lm−2h−1. FS added to the membrane structure did not affect the separation by gravity, while the addition of FS to the membrane structure in the mechanical system increased the separation performance. The PAN/PS/FS-1.5 membrane, which has a very good separation performance in harsh conditions, showed a permeability value of 6369 Lm−2h−1 in the separation of dichloromethane (DCM) from water. However, while the PAN/PS/FS-1.5 membrane had a separation efficiency of 98 % in the gravimetric method, this value was > 99.0 in the forced separation process. In the reusability test, no physical deformation was observed in the membrane after a total of 30 cycles and a 33 % loss in permeability flux occurred.