South African Journal of Chemical Engineering (Jul 2023)
A new PERVAPTM membrane to enhance the dehydration of isopropanol by pervaporation
Abstract
The performance of a new commercial polyvinyl alcohol (PVA) membrane (PERVAPTM 4100HF) was investigated and compared with a standard membrane (PERVAPTM 4100) for the dehydration of isopropanol (isopropyl alcohol) with an azeotropic point using pervaporation process. Both membranes were also characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, and contact angle (CA) goniometer. The results showed that the PERVAP™ 4100HF was thinner (1–1.5 μm) and had a lower degree of cross-linking than the PERVAP™ 4100HF (2–3 μm). The effect of the feed water concentration and operating temperature on the membranes separation performance in terms of the permeation flux, separation factor, selectivity, and permeance was investigated. The water permeates in the PERVAP™ 4100HF (∼3350 GPU) was seven times higher than that in PERVAP™ 4100 (∼463 GPU) at 70 °C and for 7 wt.% of water concentration in the feed. The water/isopropanol selectivity of the new membrane under these operating conditions was very high (∼17,000). The total permeation flux of water and isopropyl alcohol (IPA) was increased with the feedwater concentration (0.0690–1.0275 and 0.0079–0.6384 kg/m2.hr) for PERVAP™ 4100HF and PERVAP™ 4100, respectively with feed water concentration increased from 7 to 18 wt.%. The temperature dependence of the pervaporation behaviors was investigated in detail in terms of the Arrhenius activation energy. The effect of the feedwater concentration on the Arrhenius activation energy was also studied to evaluate the mass transfer across the membrane under other operating conditions, such as high temperatures and low feedwater concentrations. The new membrane PERVAP™ 4100HF exhibited the best dehydration properties at water concentrations in the azeotropic region and below, making it possible to pervaporate even at low feedwater concentrations.
