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Functionalization of silica nanoparticles to reduce membrane swelling in CO
 2
 absorption process

BACKGROUND: Membrane gas absorption (MGA) is an attractive alternative to conventional absorption for carbon dioxide (CO₂) removal, but the performance can be severely retarded due to membrane wetting issues. In order to overcome this, silica nanoparticles functionalized with low‐density polyethylene (LDPE) were added into polyvinylidene fluoride (PVDF) membrane matrix to increase the membrane hydrophobicity and avoid changes in membrane morphology caused by membrane swelling. RESULTS: The incorporation of LDPE‐functionalized silica inside the membrane enhanced the contact angle and LEPw values from 73.2° to 109.1° and 5.98 bar to 9.25 bar, respectively. These increments indicate an improvement in hydrophobicity for the LDPE‐silica/PVDF composite membrane, thus, enhanced membrane anti‐wetting ability. Furthermore, Fourier transform infrared (FTIR) analysis, field emission scanning electron microscope (FESEM) and swelling tests indicated that prolonged exposure to amine absorbent caused the serious degradation and swelling of the neat PVDF membrane with surface coated LDPE. By contrast, the wetting effects were insignificant for the LDPE‐silica/PVDF composite membrane, which led to a stable MGA performance using 2‐amino‐2‐methyl‐1‐propanol as the reactive absorbent. CONCLUSION: The ability of the composite membrane to resist wetting, swelling and chemical degradation is attributed to the restriction PVDF chain movement by its intermolecular interactions with LDPE‐functionalized silica. These improvements led to the fabrication of a hydrophobic, chemically stable composite membrane that was able to show a consistent CO₂ absorption flux of 8.7 × 10⁻⁴ mol m⁻² s–¹ over 120 h of MGA operation. © 2019 Society of Chemical Industry