Synthesis of Co(OH)2/poly(MMA-St-APEG) mixed matrix membranes by in-situ microemulsion polymerization for pervaporation separation of benzene/cyclohexane mixture

Abstract

Aiming to construct mixed matrix membranes (MMMs) with high performance for separating benzene/cyclohexane hydrocarbons, small-sized Co(OH)2 nanoparticles (less than 10 nm of size) were first prepared in reverse microemulsion micelles by using allyloxypolyethyleneglycol(APEG) as a surfactant and methyl methacrylate-styrene (MMA-St) mixture as an oil phase. Next, Co(OH)2/Poly(MMA-St-APEG) MMMs were fabricated via in-situ microemulsion polymerization. Scanning electron microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy were employed to explore the morphology and structure of Co(OH)2 nanoparticles and their resulting MMMs. Results showed that the protection of micelles during polymerization caused Co(OH)2 nanoparticles to have good distribution in the polymeric matrix. The well-distributed Co(OH)2 nanoparticles in MMMs could interact with benzene molecules by π-π combination, which enhanced the separation performance of MMMs for benzene in the swelling and pervaporation experiments. The activation energy required for benzene to pass through MMMs, including well-distributed Co(OH)2 nanoparticles, was significantly less than that for cyclohexane. Introducing more well-distributed Co(OH)2 nanoparticles further improved the benzene separation performance of MMMs. However, the improvement on the benzene separation performance was weakened when serious agglomeration of nanomaterials occurred in MMMs. The best membrane flux and separation factor of Co(OH)2/poly(MMA-St-APEG) MMMs were approximately 800 g·m−2·h−1 and 12.5, respectively.