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Kinetics and thermodynamics of SO2 adsorption on metal-loaded multiwalled carbon nanotubes

Abstract To investigate the adsorption kinetics and thermodynamic adsorption mechanism and laws of dry flue gas desulfurization, we prepared a new adsorbent by loading Cr, Cu, and Zn on TiO2-loaded multiwalled carbon nanotubes. Desulfurization experiments were also carried out. In this study, three kinds of samples were used for simulation and diffusion processes in the dynamic adsorption of different SO2 volume fractions in flue gas and thermodynamic model analysis of different temperatures in flue gas. Results show that the diffusion coefficient of SO2 in three kinds of samples ranges from 10−16 to 10−14 m2 s−1, and the diffusion may be dominated by configuration diffusion. The intraparticle diffusion model predicts that the performance improves with an increase in the SO2 volume fraction and a shift of adsorption time. This finding indicates that an increase in SO2 volume fraction and a change in adsorption time increase the Kundsen diffusion specific gravity and decrease the configuration diffusion specific gravity, thereby increasing the SO2 diffusion resistance, which becomes faster than the activation energy barrier resistance in the catalytic oxidation reaction. Thus, the diffusion resistance specific gravity increases in the total resistance of the diffusion reaction. One possible mechanism of the adsorption process is the transition to surface reaction control at the early stage of adsorption to joint control of late diffusion and surface reactions. Adsorption thermodynamics studies show that SO2 adsorption by three adsorbents is a spontaneous, exothermic, and entropic reduction process, and the increase in temperature is inconducive for SO2 adsorption in three samples.