Fabrication of polystyrene (PS)/cyclohexanol-based carbon nanotubes (CNTs) mixed matrix membranes for vacuum membrane distillation application

Abstract

In this work, for the first time, carbon nanotubes (CNTs) with hydrophobic nature were used as an appropriate nanofiller to fabricate polystyrene (PS)/CNTs mixed matrix membranes (MMMs) for vacuum membrane distillation (VMD) application, successfully. At first, the effect of PS concentration on performance of the prepared membranes was investigated. As a novelty, the performance of the back of the neat PS membranes was also evaluated. Subsequently, at optimized PS concentration (15 wt%), the effect of CNTs content on the PS/CNTs MMMs performance was investigated. FESEM, FTIR, AFM, Tensile strength and water contact angle analyzes were performed to characterize the prepared MMMs. Increased porosity and average pore size and improved mechanical properties were observed for PS/CNTs MMMs compared to the neat PS membranes. It was found that the cyclohexanol-based CNTs with high hydrophobicity and unique physicochemical properties could improve the prepared MMMs performance in VMD application. On the other hand, the oxygen atom in cyclohexanol structure facilitates dispersion of CNTs in organic solvents and polymeric matrices and also improves the CNTs transport properties. Compared to the optimized PS membrane with water contact angle (WCA) of 80.21° and flux of 2.5 L/m2.h, the performance of the PS/CNTs MMM incorporated with 1 wt% of the raw CNTs (optimum membrane) with WCA of 91.64° and water flux of 34.78 L/m2.h improved, significantly. Also, it was found that liquid entry pressure (LEP) of the PS/CNTs MMMs is higher than that of the neat PS membranes. Finally, to study the influences of some operating parameters on the optimized PS/CNTs MMM performance, Taguchi experimental design method was applied.