Performance of Polybenzoxazine membrane for water–ethanol separation

Abstract

In this research, polybenzoxazine (PBZ) membrane, NaA-PBZ double layered membrane, and NaA-PBZ mixed matrix membrane were prepared on tubular α-Al₂O₃³ support by dip-coating technique for separating ethanol-water mixture via pervaporation. Effects of preparation parameters and operating parameters, including PBZ precursor concentrations, number of dipping, type of PBZ precursor, NaA zeolite coating time, amount of NaA zeolite loading, feed ethanol concentration, and operating temperature, on the pervaporation performance were studied and discussed. Swelling tests of each prepared membranes were also conducted to determine the mechanisms involved in pervaporation. The results showed that the PBZ membrane synthesized from bisphenol-A, formaldehyde, and hexa-methylenediamine (HDA) provided the best pervaporation performance with total permeation flux in a range of 23–33 g m-² h-¹ and separation factor more than 10,000. It was also found that the total permeation flux was improved, up to 106 g m-² h-¹ when the NaAPBZ double layered membrane was introduced. Moreover, in the case of NaA-PBZ mixed matrix membrane, both the total permeation flux and the separation factor were increased with increasing amount of NaA zeolite loading. The optimal amount of NaA zeolite loading was to use 15wt% NaA zeolite, providing the highest total permeation flux of 725 g m-² h-¹ with the separation factor of higher than 100,000.