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 (q_t) 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 k_f 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.

Keywords:

• Silica
• chitosan
• adsorption
• biogas
• CO₂ adsorption kinetics

Acknowledgements

The authors gratefully acknowledge the Advanced Material Laboratory (AMaL), Diponegoro University, Indonesia, for all support in this study.

Conflicts of interest

The authors declare that there is no conflict of interest regarding the publication of this paper.

Data availability

The data used to support the findings of this study are available from the corresponding author upon request.

Funding statement

The authors declare that they have no known institutional funding, competing financial interest, or personal relationship to influence the work reported.