Preparation and kinetics study of silica adsorbent derived from geothermal waste impregnated with chitosan for gas separation of CO2 and CH4

Abstract

Gas separation of CO2 from mixed gas has been implemented in several methods, such as adsorption using activated carbon, zeolite, and silica adsorbents. This study aims to investigate the use of silica as an adsorbent by impregnating it with chitosan and using cetyltrimethylammonium bromide (CTAB) as a surfactant. A kinetics analysis was carried out using the modified silica from mixed gas, and the artificial composition of CO2 and CH4 was conducted using a volume ratio of 30:70. The adsorbent was characterized by fourier-transform infrared spectroscopy, scanning electron microscope-energy dispersive X-ray, and Brunauer–Emmett–Teller analysis before and after adsorption. The CO2 adsorption capacity (qt) was obtained at 61.334 mg/g with 60.6% CO2 removal using a mass ratio of CTAB:sodium silicate at 3% w/w, volume ratio of HCl:sodium silicate at 2% v/v, and mixed gas flow rate of 130 mL/min at room temperature and ambient pressure of 25 °C, and 1 atm. The kinetics was observed using a pseudo-first- and second-order model with kf and R2 of 0.1591/min and 0.7339, and 0.0019 g/mg.min and 0.9979, respectively. The results showed that the pseudo-second-order kinetic model represents the CO2 adsorption on chitosan-modified silica adsorbent. However, the rate constant is lower than that of the pseudo-first-order kinetic model.