Influence of feed flow rate, temperature and feed concentration on concentration polarization effects during separation of water-methyl acetate solutions with high permeable hydrophobic pervaporation PDMS membrane

Abstract

A novel and efficient method is proposed to evaluate the concentration polarization (CP) effect in pervaporation process. The novelty of the method results from the approach towards the CP phenomenon, that proposes the calculation algorithm on the basis of permeate fluxes and feed/permeate compositions as a function of the feed flow velocity only. The main advantage of the method over the approaches available in the literature is that the intrinsic enrichment factor is calculated directly from the experimental data instead of being found as one of the regression parameters. To prove this approach, pervaporation experiments were carried out using commercial hydrophobic composite PDMS based membrane Pervatech for the recovery of methyl acetate (MeAc) from diluted aqueous solutions (0–1.5 wt% MeAc in feed mixture). Pervaporation performance of PDMS membrane was investigated at various feed flow rates in the range 4.8–70 dm3 h−1 and at three different temperatures of feed mixture (i.e. 30 °C, 40 °C, and 50 °C). It was shown that the intrinsic enrichment factor changes noticeably when the process parameters are altered and this change is one of the key factors affecting the concentration polarization modulus value during pervaporative removal of organic compounds from diluted aqueous solutions. With increasing temperature and feed flow rate, the concentration polarization modulus increases, reaching the value close to 1 at temperature of 50 °C and at the average feed flow rate equal to 1.34 cm s−1. Moreover, under these conditions, the thickness of the boundary layer tends to zero.