(593g) Engineering Enzymatic Hydrogel Membranes for CO2 Capture Via Melt Coextrusion

CO₂ capture from flue gas is an extremely important gas separation, as the effects of atmospheric CO₂ on global average temperature are well documented. Polymer membranes have been identified as a useful technology to improve the energy efficiency of this separation. This talk will focus on a specific form of polymer membrane, referred to as an enzymatic membrane. These enzymatic membranes are a class of catalytic membrane reactors that can combine high rates of mass transport seen in traditional polymer membranes, with additional reaction selectivity provided by enzymes fine-tuned for specific reaction pathways. Carbonic anhydrase is of particular interest due to its incredibly high turnover rate converting CO₂ to useful bicarbonate ions, making it valuable in CO₂ capture applications. This presentation will cover design and formation of these membranes via melt coextrusion. Hot melt extrusion is an established manufacturing technique known for its ability to process large amounts of polymer quickly and produce products with controlled geometries. By combining lyophilized bovine carbonic anhydrase with a low melting-point thermoplastic, (polyethylene oxide), and a crosslinking agent in a twin-screw extruder and melt-processing the mixture, we can take advantage of the existing technology’s benefits to produce polymer films at scale. These films can then be crosslinked and swollen with water to form enzymatic hydrogel membranes.

This talk will specifically focus on processing considerations, examining the effects of extrusion temperature, shear rate, polymer molecular weight, and crosslinker content for ensuring good enzymatic activity post-melt processing, as well as good hydrogel properties post-crosslinking and post-swelling. Interestingly, enzyme activity assays and spectroscopic measurements demonstrate that significant percentages of carbonic anhydrase survive melt-processing conditions, with additional input being provided on the mechanism controlling enzyme stability. Additionally, control of hydrogel swelling behavior can be achieved by changing crosslinker concentration before extrusion as well as by controlling crosslinking conditions after extrusion. Lastly, the interplay between enzyme activity, hydrogel swelling behavior, and their relationship to good membrane performance will be discussed.