Absorption behavior of CO₂ was studied in different hollow fiber membrane modules fabricated using Celgard (polypropylene) and poly(4-methylpentene-1) microporous hollow fibers. Pure water, aqueous solutions of poly(amidoamine) (PAMAM) dendrimer of generation zero and monoethanolamine (MEA) were used as the absorbent; the absorbent solution flowed through the fiber bore, the gas mixture of C02 and N2 flowed countercurrently on the shell side. The system consisted of absorption in one module and stripping with Helium in another module of the same fibers. The absorption characteristics of the dendrimer solution and the MEA solution were studied in the modules built of Celgard fibers and poly(4-methylpentene-1) fibers respectively. The overall CO₂ mass transfer coefficients were calculated for the above-mentioned cases and compared. Experiments were carried out for a long period of time to study the stability of the system and hence the wettability of the membranes by the absorbents. The permeation of the absorbents through the pores of the fiber from the tube side to the shell side of the module was also studied especially in the case of MEA.

From the experimental observations, it was concluded that the pores in the Celgard membrane were not wetted at all by the aqueous dendrimer solution; the MEA was found to permeate through the pores of the poly(4-methylpentene-1) fiber. WA present in the pores while permeating may have reduced the membrane resistance slightly and hence, increased the absorption rate.