Effect of ethanol concentration in water coagulation bath on pore geometry of PVDF membrane for Membrane Gas Absorption application in CO2 removal

In this study, polyvinylidenefluoride (PVDF) flat sheet membranes were fabricated by immersing into various concentrations of ethanol in water (M-1:0%, M-2:25%, M-3:50% and M-4:75% respectively) as the coagulation bath via a non-solvent induced phase-inversion (NIPS) method. It was observed that the presence of ethanol affected the properties of the membranes. Low concentration of ethanol improved the hydrophobicity of the membranes. It also caused the formation of smaller pore size with more uniform, narrower pore distribution. Hydrophobicity of the fabricated membranes increased when the concentration of ethanol was raised. The absorption of carbon dioxide, CO2 in 2-amino-2-methyl-1-propanol (AMP), 1 M was also studied in a Membrane Gas Absorption (MGA) system where membranes M-2 and M-4 had better mass transfer and higher CO2 fluxes. CO2 removal efficiency, η generally decreased with time for all membranes and had the highest value for M-2. The increasing trend of CO2 removal efficiency for all membranes was as follows: M-1 < M-3 < M-4 < M-2 which indicates membrane with higher porosity has higher absorption rate. Stability of membranes was tested for 150 min of operation. Membrane wettability was observed to be dependent on hydrophobicity of each membrane. Smaller pore size with higher hydrophobicity eliminates penetration of liquid into the pores.

► Increasing concentration of ethanol in water coagulation bath increased the hydrophobicity.
► Increasing concentration of ethanol in water coagulation bath produce smaller pore size.
► Raising the ethanol concentration in water coagulation bath decreased the porosity.
► Membrane with smaller pore size with higher hydrophobicity has lower wettability rate.
► Higher CO2 removal in Membrane Gas Absorption using smaller pore size, high hydrophobicity and porosity membrane.