(371e) Separation of n-Butanol From Dilute Solution by Pervaporation Using Composite PDMS Membrane

Butanol has attracted increasing attention as an alternative to the fossil fuel. Before we can use butanol as a liquid fuel, it is necessary to refine the low-concentration butanol produced in fermentation. Pervaporation, as one of the membrane separation technologies, has high selectivity and low energy consumption compared to other separation techniques. Pervaporation can be used to separate azeotropic mixtures and other kind of mixtures, which are usually difficult to separate by conventional techniques like distillation.  Poly(dimethyl siloxane) (PDMS) membrane is the most effective and widely used membrane for separating butanol from an aqueous solution. However, butanol flux and selectivity of PDMS membranes vary with fabrication methods and process conditions, and need further improvements for economical applications. In this work, different membrane fabrication techniques were explored, including plasma treatment, dipping, and electrospinning. The effects of membrane supporting materials, including poly(vinylidene fluoride) (PVDF), polysulfone (PS), and poly(tetrafluoroethylene) (PTFE), on the pervaporation performance of PDMS membrane were also studied. Further improvements in butanol selectivity and flux by the addition of hydrophobic fillers to the PDMS membrane were also investigated. Among the membranes studied, the PDMS membrane with a thickness of ~70 µm, supported by plasma treated PTFE and filled with 20 wt% CBV28014, gave the best separation performance, with a separation factor of 27 and a butanol flux of 48 g/m²·h. The PTFE-supported PDMS membrane can concentrate a 15 g/L butanol solution to a 290 g/L butanol solution, and is promising for use in pervaporation for butanol recovery from dilute fermentation broth.