Preliminary membrane screening and evaluation for the separation of bioethanol obtained from fermentation of oil palm empty fruit bunch (OPEFB)

Abstract

This study evaluates the effectiveness of some commercial membranes (polytetrafluoroethylene [PTFE], polyvinylidene fluoride [PVDF], polyethersulfone [PES], and nitrocellulose [NC]) in concentrating a binary ethanol-water mixture under different conditions (volumes, temperatures, pressures, and concentrations). Then, the membrane was selected based on its performance for use in ethanol and by-product separation from OPEFB fermentation broth. The optimum result for the binary ethanol-water separation was found in the PVDF membrane with the highest separation factor of 3.03 and flux of 0.015 g.cm−2 s−1 under 10 ml permeate volume, 75 °C temperature, 60 psi pressure, and 20 % (v/v) ethanol concentration. Based on the membrane field emission-scanning electron microscope (FE-SEM) analysis, the PVDF membrane also had the lowest swelling degree. Utilization of the PVDF membrane to separate crude bioethanol resulting from OPEFB fermentation gave a separation factor of 3.66. The initial bioethanol concentration was 7.67 % (v/v), and the ethanol concentration in the permeate was 23.31 % (v/v). In addition, the separation factor of propanol from the crude mixture was 5.44, and the acetic acid rejection factor was 96.7 %. The S.cerevisiae suspension and the cellulase enzyme were also separated and recovered in the retentate phase. Hence, the PVDF membrane can be used to separate bioethanol from the yeast and enzyme suspension while pre-concentrating the bioethanol product. This could eventually help reduce the energy requirement to obtain industrial-grade bioethanol.

Keywords

• Bioethanol
• Membrane
• OPEFB
• Bioethanol preconcentration
• Polyvinylidene fluoride