Zeolite X Adsorbent with High Stability Synthesized from Bauxite Tailings for Cyclic Adsorption of CO₂

Abstract

A CO2 adsorbent of zeolite X with high crystallinity, regular octahedron morphology, and a large Brunauer–Emmett–Teller (BET) surface area of 736 m2 g–1 was synthesized from bauxite tailings at 110 °C for 16 h with n(SiO2/Al2O3) fixed at 3.2. The CO2 adsorption capacities at 273 and 303 K of zeolite X were 7.3 and 6.1 mmol g–1, respectively. Moreover, multiple CO2 adsorption cycles at 298 K were conducted to investigate the stability and lifetime of the synthesized zeolite X. The result showed that CO2 capture could reach up to 6.3 mmol g–1 after 11 adsorption–desorption cycles, which was dropped by only 1.6% compared to that after the first cycle. Furthermore, 11 N2 adsorption cycles at 77 K on zeolite X were subsequently measured to detect the microstructure of zeolite X in each cycle; it possessed excellent stability and regenerability with a stable BET surface area and micropore volume after multiple adsorption cycles. In addition, the original zeolite X and the zeolite X after multiple cycles of adsorption were successively characterized with X-ray diffraction, scanning electron microscope, and Fourier transform infrared measurements and the results demonstrate that microstructures of zeolite X after 6 and 11 CO2 adsorption cycles were not destroyed, respectively. Hence, the low-cost zeolite X synthesized from solid waste bauxite tailings could be widely used for large-scale industrial greenhouse gas capture. Moreover, it as a promising adsorbent is urgently needed for the cyclic adsorption processes in view of its extremely stable performance.