Preparation of silica xerogel with high silanol content from sodium silicate and its application as CO2 adsorbent

In this study, silica xerogels with high silanol content were synthesized by using sodium silicate as low-cost silica source in the presence of hydrochloric acid and acetic acid via sol–gel process for CO2 adsorption purpose. The effect of amount of acetic acid on the surface and structural properties of silica xerogel was investigated. Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA) revealed that the silanol groups existed on the surface of silica xerogel products and their concentration increased with increasing the amount of acetic acid. The BET surface area and total pore volume of the silica xerogel prepared using 6 mL of acetic acid (MMS-6) were found to be 1021 m2/g and 0.72 cm3/g, respectively. The pore structure of silica xerogel products consisted of the interparticle voids between the nanoparticles aggregates, and the interconnected wormhole microporous structure. The latter pore structure was more uniform on increasing the amount of acetic acid. CO2 adsorption/desorption measurements were carried out using TGA unit with high purity CO2 (99.999%). The highest CO2 sorption capacity (83.6 mgCO2/gsorbent) was obtained with MMS-6 product. Thermal swing adsorption studies showed that the silica xerogel products exhibited strongly reversible CO2 adsorption capacity and stable during 5-repeated cycle of adsorption/desorption experiment at 35 °C.