Pervaporation separation of ethanol/ETBE mixture using poly(lactic acid)/poly(vinyl pyrrolidone) blend membranes

The pervaporation properties of poly lactic acid (PLA), a natural source polymer, were studied in a polar/non-polar case study. PLA/PVP (poly vinyl pyrrolidone) blend membranes were prepared containing different PVP contents and evaluated in ethanol/ethyl tert-butyl ether azeotropic separation. The swelling and mechanical properties of the membranes were investigated. SEM cross-sectional images showed a porous structure at higher PVP concentrations. The degree of swelling as well as the permeation flux (0.05–1.36 kg/m2 h) gradually increased when the PVP amount increased to 21 wt%. On the other hand, the EtOH separation factor initially raised to 16 using 3 wt% PVP and then decreased to 3 using 21 wt% PVP. The continuously decreasing water contact angle from 74° in PLA to 54° confirmed higher hydrophilicity and EtOH affinity at higher PVP contents. However, the more porous morphology and the plasticization effect resulted in selectivity decrease. This was also in agreement with the observed mechanical behavior of the blends. At higher EtOH concentrations and PVP contents, the elastic modulus of the membranes decreased, contrary to the membrane elongation.

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► PLA/PVP blend membranes could be used to separate EtOH/ETBE mixture.
► The morphology of the membranes could be controlled with PVP amount.
► The permeation flux and selectivity increases with PVP up to a certain amount.
► The swelling degree and elasticity increases with PVP while the mechanical strength decreases.