Separating isopropanol from its diluted solutions via a process of integrating gas stripping and vapor permeation

Abstract

Considering environmental pollution, disposal costs, the high-value of isopropanol (IPA) and other factors, recovering isopropanol from industrial effluent is considered to be attractive, practical and cost-effective. However, the separation techniques including gas stripping, distillation, and pervaporation often yield low selectivity and high energy consumption. In this paper, a process of integrating gas stripping and vapor permeation was conducted for separating isopropanol from dilute solutions. A PDMS (polydimethylsiloxane) membrane was prepared by using a green method. The effects of gas flow rate, membrane model temperature, feed solution temperature, and feed solution concentration on the performance of the separation system were investigated. The results in this study showed that the optimized separation performance (isopropanol flux 437.8 g m⁻² h⁻¹, separation factor 125.8) was obtained for separating 3 wt% isopropanol solution at 75 °C, which were 1.48 times and 7.4 times of those obtained in the PV process. The energy consumption of evaporation was only 1.28 MJ kg⁻¹; this was 26% and 30% of the evaporation energy needed for the PV process and the distillation process at the same conditions. Additionally, a comparison of separation performance with other separation techniques was also conducted in the study.