Piperazine-modified activated alumina as a novel promising candidate for CO2 capture: experimental and modeling

In this research, the CO2 adsorption process was studied using modified activated alumina with a piperazine solution as a novel sorbent. Activated alumina was modified with a piperazine solution concentration in the range of 1-4 wt%. Adsorption experiments were performed to evaluate the operating parameters, including CO2 pressure in the range of 2-8 bar, adsorbent dosage in the range of 0.5-2 g, temperature in the range of 25-85 degrees C and adsorbent mesh in the range of 200-800 micron. Maximum adsorption capacity (222.01 mg CO2/g modified activated alumina) was determined at a temperature of 25 degrees C, pressure of 8 bar, and adsorbent dosage of 0.5 g, with a piperazine solution of 2 wt%. The results of the experiments showed that the rate of CO2 adsorption increases with increasing pressure and decreasing temperature. The Freundlich isotherm model with correlation coefficient of 0.999 was found to be the best for fitting the CO2 adsorption isotherm data. The kinetic study also indicated that the Elovich model fits the experimental kinetic data well. The negative values of Gibbs free energy change (Delta G degrees) and enthalpy change (Delta H degrees) show that the reaction is spontaneous in nature and exothermic. The negative value of entropy change (Delta S degrees) shows a reduction in the irregularity of the adsorption process. (c) 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.