Chitosan-bleaching earth clay composite as an efficient adsorbent for carbon dioxide adsorption: Process optimization

In this study, chitosan-bleaching earth clay composite (Chi-BE) was prepared in three different ratios (1:0.4, 1:0.6 and 1:0.8) by the alkali gelation method for carbon dioxide (CO2) adsorption in a fixed-bed adsorption system. Chi-BE (1:0.6) with best adsorption capacity was selected through fractional factorial design and characterised through Brunauer-Emmett-Teller, scanning electron microscope and Fourier transform infrared analyses. The CO2 adsorption study was carried out via a central composite design and optimised it using desirability function. Results showed significantly positive roles of temperature, adsorbent loading and CO2 concentration on CO2 adsorption by Chi-BE within the range and individual levels. However, only adsorbent loading and CO2 concentration presented a mutual effect on CO2 adsorption. The optimised factor levels of 38.13 degrees C for temperature, 0.72 g for adsorbent loading and 25% CO2 concentration were obtained, which resulted in the CO2 adsorption capacity of 344.98 mg/g. The regeneration study revealed that the spent Chi-BE was recycled 10 times. This study suggests that Chi-BE is an effective and stable CO2 adsorbent under moderate environment.