(301f) Novel Polytriazole Ion Exchange Membranes for Bioseparations

Authors: 
Boi, C., University of Bologna
Chisca, S., King Abdullah University of Science and Technology (KAUST)
There is a need for processes of membrane manufacture using solvents, which are not associated with hazards, which would be safer and greener than those used so far in industrial processes. Ionic liquids (IL) and dimethyl carbonate (DMC) are considered environmentally friendly solvents, because are non-toxic, relatively inert and safe under ambient conditions.

This work presents a new green process for manufacture of polytriazole ion exchange membranes for protein separation. This involves the solubilization at room temperature of a polytriazole with free OH groups in ionic liquids such as, 1-ethyl-3-methylimidazolium acetate (IL) and dimethyl carbonate (DMC). The interesting fact is that the polytriazole polymer is not soluble in pure IL or DMC, but it is soluble in different ratios mixture of these two solvents. We experimentally evaluated the solvent ratios leading to one phase solution, delimitating the phase diagram for this system. The membranes were obtained by phase inversion, using water as precipitation bath or mixture of water â?? methanol and water â?? ethanol. We studied by SEM how the ratio of the solvents and how different precipitation baths influence the membrane morphology. The membranes were activated for lysozyme adsorption by grafting sulfonic groups. Two sultone structures were used as grafting agents: 1,3 propane sultone and 1,4-butane sultone. The modification of the membranes took place by ring opening mechanism. The activation was done by immersion in 5%wt solution of grafting agent in water, containing small amount of NaOH, at 65 °C. The grafting sulfone groups on the membrane were confirmed by FTIR, NMR and TGA, and the membranes morphology was investigated by SEM.

The ion-exchange membranes were preliminary characterized in bind and elute mode using pure lysozyme solutions. The Tris buffer, chosen for equilibration and adsorption, was optimized in terms of molarity and pH. The membranes modified with 1,4-butane sultone showed higher adsorption than the membranes modified with 1,3-propane sultone. Indeed, the values of static binding capacity obtained are promising and comparable to that of commercial ion-exchange membrane adsorbers used for polishing steps in antibody manufacturing.

Acknowledgement

This research was supported by King Abdullah University of Science and Technology (KAUST)