CO₂ capture performance of bi-functional activated bleaching earth modified with basic-alcoholic solution and...

CO₂ capture performance of bifunctional activated bleaching earth (ABE) was investigated at atmospheric pressure. The sorbents were characterized by means of X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Caron-Hydrogen-Nitrogen analysis (CHN), Fourier transform infrared (FT-IR) and thermal gravimetric analysis (TGA). The CO₂ capacity was enhanced via basic-modification and monoethanolamine (MEA) loading of the ABE sorbent to obtain a bifunctional surface property. Here, basic-modified calcined ABE with a 30wt.% MEA loading (SAB-30) showed the highest CO₂ capture capacity, but this was decreased with excess MEA loading (>30wt.%). At a 10% (V/V) initial CO₂ concentration feed, the maximum capacity of SAB-30 increased from 2.71mmol/g at 30°C (without adding moisture to the feed) to 3.3mmol/g at 50°C when adding 10% (V/V) moisture to the feed. Increasing the moisture concentration further reduced the maximum CO₂ capacity due to the blocking effect of the excess moisture on the sorbent surface. However, SAB-30 could completely capture CO₂ even in a 100% (V/V) initial CO₂ concentration feed. A maximum CO₂ capacity of 5.7mmol/g for SAB-30 was achieved at 30°C. Varying the ratio of sorbent weight to total flow rate of the gas stream had no discernible effect on the equilibrium CO₂ capture capacity. Avrami's equation and Toth's isotherm model provided a good fitting for the data and suggested the presence of more than one reaction pathway in the CO₂ capture process and the heterogeneous adsorption surface of SAB-30. Thermodynamics studies revealed that CO₂ capture on the bifunctional SAB-30 is feasible, spontaneous and exothermic in nature.