Surface modification to produce superhydrophobic hollow fiber membrane contactor to avoid membrane wetting for biogas purification under pressurized conditions

This article investigates CO₂ removal from biogas (containing 40% CO₂ and 60% CH₄) using a hollow fiber membrane contactor (HFMC) with K₂CO₃ aqueous solutions as absorbent at elevated pressures up to 10 bar. Superhydrophobic PTFE membrane fibers (with a water contact angle of 158.4° and sliding angle of 1.3°) were fabricated by spraying silica nanoparticles on membrane surface and then used in membrane module for absorption experiments. The modified membrane outperformed the original membrane at elevated absorption pressures, and the highest CO₂ removal efficiency and absorption flux reached 97.1% and 1.85 × 10⁻³ mol m⁻² s⁻¹, respectively. A 2D axisymmetric non-wetted mathematic model was developed to determine the membrane wetness conditions during absorption experiments. The model validation results indicated that when using aqueous K₂CO₃ solutions as absorbent the modified superhydrophobic membrane used in this study was able to prevent membrane wetting even at pressurized conditions up to 10 bar. This work showed that the superhydrophobic membranes modified by spray-deposition technique have great potential for application in HFMC to avoid membrane wetting for biogas purification under pressurized conditions.