Polyvinyl alcohol membrane incorporated with amine-modified silica nanoparticles and ionic liquid for facilitated transport of CO2

Abstract

The application of polymeric membranes in post-combustion carbon capture is limited by solution-diffusion. In this work, polyvinyl alcohol (PVA) membranes with facilitated transport of carbon dioxide (CO2) were improved by incorporating the fixed carrier, amine-modified silica nanoparticles (SiO2) and the mobile carrier [bmim][Tf2N] ionic liquid. The BET surface area of diethanolamine (DEA)-modified SiO2 nanoparticles decreased from 150.14 m2/g to 22.68 m2/g, but they improved the surface hydrophilicity of PVA membranes more significantly than the unmodified SiO2 nanoparticles due to the existence of secondary amine groups. Fourier transform infrared spectra confirmed the incorporation of secondary amine and anion of IL that can facilitate CO2 permeation. The thermogravimetric analysis also revealed that the thermal stability of PVA membranes was improved by incorporating inorganic nanoparticles and ionic liquid. The thickness of the dense PVA layer coated on polyethersulfone support increased by incorporating SiO2 and DEA-modified SiO2 nanoparticles, as shown by scanning electron microscope images. The positive effects of SiO2 nanoparticles on the CO2 separation performance of PVA membranes were enhanced by reducing the particle size and increasing particle loading. DEA elevated the enhancement through the Zwitterion mechanism. [bmim][Tf2N] IL also improved the CO2 separation performance of PVA membranes. Hence, the PVA membrane containing 2 wt% of DEA-modified SiO2 nanoparticles (15-20 nm) and 0.4 M of [bmim][Tf2N] IL in ethanol attained a CO2 permeance of 3016 GPU and CO2/N2 selectivity of 62.08.