Removal of phenolic contaminants from water by pervaporation

Abstract

The removal of phenolic compounds from water streams is of great importance due to their high toxicity, carcinogenicity, and bioaccumulation in food chains. In this study, the separation of four representative phenolic compounds (including phenol (PhOH), p-cresol (MePhOH), p-chlorophenol (ClPhOH), and p-nitrophenol (O2NPhOH)) from aqueous solutions by pervaporation using poly(ether-b-amide) (PEBA) membrane was studied. The effects of feed concentration (up to 0.6 wt%) and operating temperature (30–70 °C) on the separation performance were investigated. While the permeation fluxes of phenolic compounds increased at higher feed concentrations, the increase in the flux was less than proportional, leading to a decrease in the enrichment factor. It was also shown that both the permeation flux and the enrichment factor increased with an increase in temperature. However, the permeabilities of the phenolic compounds in the membrane were impacted differently. Of particular interest were the coupling effects of co-existing phenolic compounds due to permeant-permeant interactions, which were found to be significant in permeation of multiple phenolic compounds that were relevant to practical applications. The permeation of PhOH, MePhOH and ClPhOH was all affected adversely by the presence of additional phenolic compounds in the feed solution, while the opposite was true for the permeation of slow-permeating O2NPhOH. Depending on the specific phenol solute, high-purity phenol crystals could be produced from the phenol-enriched permeate via de-sublimation in the cold trap, which was of particular interest for practical applications.