Effect of non-solvent additive concentration on CO2 absorption performance of polyvinylidenefluoride hollow fiber membrane contactor

Membrane contactor for post-combustion carbon dioxide (CO2) capture is a promising alternative to conventional gas-liquid absorption systems. In order to improve the polyvinylidenefluoride (PVDF) hollow fiber membrane structure for CO2 absorption via membrane contactor, the effect of non-solvent additive concentration on the membrane structure and CO2 absorption performance was investigated. Lithium chloride (LiCl), phosphoric acid (PA) and their mixture over a range of concentrations (0-8 wt%) were used as non-solvent additives. The morphological cross sections of the prepared membranes included four segments from the inner to outer surface, which were successively termed the nodule-like zone, transitional zone, porous zone and skin layer. Increasing the concentration of non-solvent additives increased sponge-like structures, decreased finger-like structures in the porous zone, and decreased mean pore size on the membrane outer surface. CO2 membrane contact absorption tests showed a positive correlation between the CO2 absorption flux and the non-solvent additive concentration. The highest CO2 absorption flux of 1.31 × 10−3 mol m−2 s−1 was obtained at an inlet gas (CO2/N2 = 19/81, v/v) flowrate of 130 mL/min and an absorbent liquid (distilled water) flowrate of 70 mL/min by adding 8 wt% of PA in the PVDF dope solution.