Surface modified hollow fiber membrane contactor for carbon dioxide absorption and desorption

Abstract

Porous asymmetric polysulfone (PSf) and polyvinyliden flouride (PVDF) hollow fiber membranes were structurally developed using surface modifying macromolecules (SMMs) as additives to improve hydrophobicity, wetting resistance and carbon dioxide (CO2) absorption/desorption flux in hollow fiber membrane contactor. The membrane structure was examined in terms of gas permeation, critical water entry pressure, overall porosity, contact angle and mass transfer resistance. The morphology of membrane was studied by scanning electron microscopy (SEM) instrument. The CO2 absorption and desorption performance of both surface modified membranes were investigated in a hollow fiber membrane contactor system and compared against the unmodified membranes. Pore size, overall porosity and contact angle of fabricated membranes increased significantly by surface modification. Surface modified PVDF and PSf membranes showed higher CO2 absorption and stripping flux compared to plain PVDF and PSf membranes. Results of long-term study demonstrated that after an initial CO2 flux reduction the surface modified membranes performance maintained constant over 130 h operation. By increasing SMM concentration in spinning dope to 6 wt.%, CO2 absorption and stripping flux increased. However, by increasing SMM concentration to 8 wt.% both CO2 absorption and stripping flux decreased, considerably. Thus, it can be concluded that for surface modification of PVDF and PSf hollow fiber membrane contactor 6 wt.% of SMM as additive is an optimum concentration. From CO2 stripping experiments it was found that liquid absorbent temperature played an important role on CO2 stripping flux but gas flow rate had no significant effect. Generally, it was found that the porous surface modified membrane can be a promising alternative for CO2 removal and stripping process.