Separation of CO2 from hydrogen using membrane gas absorption with PVDF/PBI membrane

•Membrane gas absorption was tested for CO2 separation from H2.•PVDF membrane with 20 wt% PBI loading showed higher CO2 flux than PVDF membrane.•41% of CO2 in a gas mixture of H2 and CO2 could be reduced using water only.

Biohydrogen contains carbon dioxide that requires efficient separation at low pressure and temperature. In this work, the feasibility of membrane gas absorption (MGA) in the separation of CO2 from hydrogen was investigated. The blending of amorphorus polybenzimidazole (PBI) and semicrystalline polyvinylidene fluoride (PVDF) resulted in a nearly superhydrophobic and microporous membrane, showing its great potential to be applied in membrane gas absorption (MGA) for CO2 capture from biohydrogen. The presence of hydrogen bonding in the polymer blend due to donor (–NH–) and proton acceptor (–N=) of PBI encouraged the formation of miscibility blend. The hydrophobicity of PVDF membrane was only slightly affected even the loading of PBI was increased to 20 wt%. The incorporation of PBI into PVDF membrane also enhanced the melting temperature (Tm) to increase from 166 °C to 171 °C. The membrane pore size was greatly improved after blending. In a MGA system with water absorbent, the PVDF/PBI membrane with 20 wt% of PBI showed the highest CO2 flux of 4.16 × 10−4 mol/m2s. More importantly, 67 % of the CO2 in a gas mixture of H2 and CO2 could be removed using diethanolamine only.

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