Membrane stripping: Desorption of carbon dioxide from alkali solvents

Membrane stripping of carbon dioxide from an aqueous 30% (w/w) potassium carbonate solvent was achieved using two types of polymeric flat sheet microporous membranes; a polytetrofluoroethylene (PTFE) membrane and an asymmetric polyether sulfone membrane with a proprietary hydrophobic surface coating. Both membranes were tested at stripping temperatures of 60–100 °C. The asymmetric membrane performed well at all temperatures. However, the mass transfer performance of the PTFE membrane was not sustained at higher temperatures, probably as a result of pore wetting by solvent intrusion. Calculations suggested that up to 72% of the membrane was wetted. In industrial applications, the use of higher temperatures could also lead to condensation of water vapour in the membrane support structure.

Research highlights
► Stripping of carbon dioxide from a solvent in a membrane contactor is achievable.
► Performance relates to the extent of solvent intrusion and capillary condensation.
► A PES membrane coated with a hydrophobic surface is compared to PTFE.
► The coated PES membrane gives better performance at a lower price.