Energy & Fuels, Vol.33, No.7, 6641-6649, 2019
Zeolite X Adsorbent with High Stability Synthesized from Bauxite Tailings for Cyclic Adsorption of CO2
A CO2 adsorbent of zeolite X with high crystallinity, regular octahedron morphology, and a large Brunauer-Emmett-Teller (BET) surface area of 736 m(2) g(-1) was synthesized from bauxite tailings at 110 degrees 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 N-2 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.