ACS Omega. 2022 May 19;7(22):18409-18426. doi: 10.1021/acsomega.2c00673. eCollection 2022 Jun 7.
A volumetric system was used to assess carbon-based adsorbents for evaluation of the gas separation, equilibrium, and kinetics of oxygen (O2), nitrogen (N2), and carbon dioxide (CO2) adsorption on granular activated carbon (GAC) and functionalized GAC at 298, 308, and 318 K under pressures up to 10 bar. The effects of ZnCl2, pH, arrangement of the pores, and heat-treatment temperature on the adsorptive capabilities of O2, N2, and CO2 were evaluated. High-performance O2 adsorption resulted with a fine sample (GAC-10-500) generated with a 0.1 wt % loading of ZnCl2. The optimal sample structure and morphology were characterized by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, and powder X-ray diffraction. On the basis of the adsorption-desorption results, the fine GAC provides a surface area of 719 m2/g. Moreover, it possessed an average pore diameter of 1.69 nm and a micropore volume of 0.27 m3/g. At 298 K, the adsorption capacity of the GAC-10-500 adsorbent improved by 19.75% for O2 but was not significantly increased for N2 and CO2. Isotherm and kinetic adsorption models were applied to select the model best matching the studied O2, N2, and CO2 gas uptake on GAC-10-500 adsorbent. At 298 K and 10 bar, the sip isotherm model with the highest potential adsorption difference sequence and gas adsorption difference compared with pure GAC adsorbent as O2 > N2 > CO2 follows well for GAC-10-500. Eventually, the optimal sample is more effective for O2 adsorption than other gases.