An Effective Method to Improve the Performance of Fixed Carrier Membrane Via Incorporation of CO2-Selective Adsorptive Silica Nanoparticles

Fixed carrier membrane exhibits attractive CO₂ permeance and selectivity due to its transport mechanism of reaction selectivity (facilitated transport), however, its performance still has to be improved to meet CO₂ capture cost targets. This study makes a first attempt to develop membranes with multiple permselective mechanisms in order to enhance CO₂ separation performance of fixed carrier membrane. A novel membrane with multiple permselective mechanisms of solubility selectivity and reaction selectivity was developed by incorporating CO₂-selective adsorptive silica nanoparticle in situ into the tertiary amine containing polyamide membrane formed by interfacial polymerization (IP). LUDOX^® HS-30 and Cabosil TS-530, two types of commercial silica nanoparticles, were dispersed in aqueous phase and in organic phase during the IP process, respectively. Gas adsorption experiments showed that both LUDOX^® silica and TS-530 silica had good CO₂ adsorption capacity and CO₂/N₂ adsorption ratio. Furthermore, various techniques (XPS, EDX, ATR-FTIR, SEM and TGA) were employed to characterize the polyamide and polyamide-silica composite membranes. A conceptual model was proposed to explain the potential impacts of silica particles during the polyamide interfacial polymerization. In addition, gas permeation experiments showed that both nanocomposite membranes had larger CO₂ permeance than that of pure polyamide membranes. An increase in CO₂/N₂ selectivity was also observed in LUDOX silica-containing membranes in comparison to polyamide membrane. The enhanced CO₂/N₂ separation performance for nanocomposite membranes was mainly due to the thin film thickness, and multiple permselective mechanisms of solubility selectivity and reaction selectivitiy. Moreover, the nanocomposite membranes exhibit superior thermal stability than pure polyamide membranes. Therefore, CO₂-selective adsorptive silica offers a potential use to effectively improve the performance of fixed carrier membranes.