Mixed matrix membranes based on polysulfone and rice husk extracted silica for CO₂ separation

Mesoporous silica particles after extraction from rice husk ash were used as fillers in polysulfone based mixed-matrix membranes (MMMs). The fillers were functionalized with 4-aminophenazone (4-AMP) to enhance the CO₂-philic properties. The attractive feature of this research was the utility of extracted silica from a biological waste-the rice husk ash. A good dispersion and adhesion of the filler within the polymer matrix were confirmed by the gas permeation results, SEM images and FTIR analysis. The results revealed that all MMMs showed high permeabilities in comparison to pristine polysulfone membrane. The higher gas permeabilities were attributed to the presence of large mesopores in the filler that led to faster diffusion of the penetrant gas. The functionalized silica showed significantly higher CO₂/CH₄ and CO₂/N₂ selectivities. The highest ideal selectivities obtained for CO₂/N₂ and CO₂/CH₄ at a maximum of 40% filler loading, were 32.79 and 33.31 respectively. All synthesized membranes were tested at various operating temperatures and their activation energies were also calculated. The highly ordered structures with short and straight pore channels and improved gas permeation properties warrant the silica extracted from rice husk as promising filler for industrial gas separation under varying conditions of temperature.