Carbon dioxide adsorption by raw and modified diatomite

Abstract

Biogas is type of renewable energy which could replace the natural gas. Biogas consist of methane (CH4), carbon dioxide (CO2) and trace amounts of impurities. CO2 and impurities in biogas can cause corrosion and poor combustion of CH4. Hence, the removal of CO2 is necessary to enhance the biogas. This study examines, the possibility of using raw and modified diatomite to adsorb CO2. Diatomite was modified using water treatment, acid treatment and a combination of the both treatment methods. Water hydration was done at different temperature (30°C, 70°C and 100°C), whereas for acid treatment it was done at various concentration of sulphuric acid (3 M, 5 M and 7 M). The samples were then tested for CO2 adsorption in a fixed bed reactor using 11% of CO2 in nitrogen gas as balance. The results showed that acid treated diatomite has the highest adsorption capacity (189.96 mg/g) compared to raw, water and combination samples. 5 M was found to be the optimum concentration of acid to be used. It was concluded that combination of water and acid treatment did not improve further the performance of the diatomite. The diatomite structure and their function in adsorption were proven by characterization study such as SEM, EDX, BET and FTIR. Diatomite can be a potential adsorbent for CO2 removal in biogas purification process.