Hydroxide modified activated alumina as an adsorbent for CO2 adsorption: Experimental and modeling

Activated alumina (AA) was modified with sodium hydroxide and potassium hydroxide solutions to enhance carbon dioxide adsorption capacity. The process optimization was carried out using response surface methodology (RSM) based on central composite design (CCD) with two variables, the temperature and pressure in the range of (20-80 degrees C) and (2-10 bar), respectively. In addition, the effect of operating parameters including adsorbent amount, percentage of hydroxide solution, temperature and pressure on the CO2 adsorption process were investigated. The optimum CO2 adsorption capacities for modified activated alumina adsorbents with 30% NaOH and KOH at temperature of 20 degrees C and pressure of 6 bar were found to be 146.70 and 130.84 mg/g(adsorbent), respectively. The Freundlich isotherm model was showed the best accordance with the experimental data and the kinetic modeling results indicated that the Elovich model is well-fitted for adsorption process by modified activated alumina. As well as thermodynamic parameters revealed that the adsorption process for the studied three adsorbents is exothermic and spontaneous.