PREPARATION AND CHARACTERIZATION OF CHITOSAN-BASED ACTIVATED CARBONS FOR POST-COMBUSTION CARBON DIOXIDE CAPTURE

Abstract

Humanity and the environment are at risk due to the growing dependence on fossil fuels, which is causing climate change and global warming. One promising method for reducing CO2 emissions is post-combustion capture (PCC), particularly when it relies on activated carbons. This study aims to synthesize potential naturally nitrogen-doped chitosan-based activated carbon adsorbents for capturing CO2 from flue gas streams (PCC) by utilizing a thermogravimetric analyzer (TGA) to investigate the adsorption performance. Herein, a methodology outstandingly dependent on a low KOH weight ratio (from (1:1 KOH) to (1:0.05 KOH)) for chemical activation, followed by hydrothermal carbonization, and thermal carbonization was employed. The synthesized adsorbents underwent characterization analysis tests, including BET, SEM/EDX, TGA, XPS, and Raman. Moreover, the adsorption performance and adsorption kinetics (linearized and non-linearized) were examined by utilizing a thermogravimetric analyzer (TGA) under the operation of different adsorption temperatures (30 ˚C, 40 ˚C, and 50 ˚C), and CO2 feed concentrations (15%, and 10%). Also, the adsorption cyclic performance was analyzed through multiple adsorption/desorption cycles, where the adsorption was at 30 ˚C, 1 bar, using 15% CO2 feed concentration, and the desorption at 110 ˚C, 1 bar, using N2 pure stream. The results showed that the synthesized adsorbents were characterized by relatively high yields, the mesoporous type of pores, a high nitrogen surface composition (9.54%, EDX), significant enhancement in thermal stability compared to the raw material, a wide range of nitrogen functionalities (Pyridinic N, Pyrrolic N, Graphitic N, and Oxidized N++O-), and an acceptable degree of disorder. Furthermore, the highest adsorption capacity was owned by low weight ratio KOH-chemically activated adsorbent (1:0.1 KOH) with a value of 35.93 mg/g (0.82 mmol/g) at 30 ˚C, 1 bar, and 15% CO2 feed concentration (𝑃𝐶𝑂2= 0.15 bar). The adsorption kinetics of all adsorbents at the different adsorption conditions employed showed to be more fitted to pseudo-second order (PSO), confirming the chemisorption type of adsorption. The best-performing adsorbent showed excellent regeneration cyclic stability over 8 consecutive adsorption/desorption cycles.