Selective separation of low concentration CO sub(2) using hydrogel immobilized CA enzyme based hollow fiber membrane reactors

This paper reported the results of developing a novel hollow fiber membrane reactor contained immobilized enzyme for selective separation of low concentration CO sub(2) from mixed gas streams. In the reactor, two bundles of poly(vinylidene fluoride) (PVDF) hollow fiber membranes were aligned staggered parallel in a tube module, and lab-made poly(acrylic acid-co-acrylamide)/hydrotalcite (PAA-AAm/HT) nanocomposite hydrogel was filled between fibers, in which carbonic anhydrase (CA enzyme) was immobilized. The effects of CA concentration, buffer concentration, the flow rate of sweep gas, operational temperature, and CO sub(2) concentration on separation performance were investigated in detail. The results showed that the transport resistance was mainly from the hydrogel layer, and decreased greatly with immobilization of carbonic anhydrase in hydrogel. Moreover, immobilized CA could retain over 76% enzymatic activity and thermal stability was also improved. The data showed that this enzyme-based membrane reactor could effectively separate CO sub(2) at low concentration from mixed gas streams. For the feed with 0.1% (v/v) of CO sub(2), the selectivity of CO sub(2)/N sub(2) was 820, CO sub(2)/O sub(2) was 330, and CO sub(2) permeance was 1.65x10 super(-8) mol/m super(2) s Pa. Prolonged runs lasting 30 h showed that separation performances of the membrane reactor were quite stable.