Investigation of CO2 removal by silica and CNT nanofluids in microporous hollow fiber membrane contactors

In this study, nanofluids of nanosilica and carbon nanotube have been applied as absorbents in a gas–liquid hollow fiber membrane contactor for CO2 separation. A gas mixture of air and CO2 was fed into the shell side in contact with pure water or nanofluid which was fed into the fibers. Effects of different parameters including the type of nanofluid, nanoparticle concentration, liquid and gas flow rates, liquid temperature and CO2 inlet concentration were investigated experimentally on the removal efficiency of CO2. The results showed that the injection of 0.5 wt% silica nanofluid increased the removal efficiency up to 20% at low liquid flow rates (compared to distilled water) while the increase is about 9% at high rates. Nanofluid of carbon nanotube showed much better separation than the silica and it enhanced the removal efficiency up to 40% and 20% at low and high liquid rates respectively. The CO2 removal efficiency of pure water and silica nanofluids slightly decreased with increasing CO2 inlet concentration which is possibly due to the saturation of these fluids. However the removal efficiency of carbon nanotube was nearly constant and even enhanced in some flow rates with increasing CO2 inlet concentration.

► Nanofluids of silica and CNT were applied in a membrane contactor for CO2 removal.
► Silica nanofluid increased the removal efficiency of CO2 up to 20%.
► Nanofluid of CNT increased the removal efficiency of CO2 up to 40%.
► Effects of different parameters were studied on the removal efficiency of CO2.
► CNT nanofluid can be proposed as an alternative absorbent in membrane contactors.