Fractal-like kinetics of adsorption on heterogeneous surfaces in the fixed-bed column

Abstract

Abstract The rate constant was independent of time in classical reaction kinetics. However, it has been found to be unsatisfactory when the reactants were spatially constrained by either walls or phase boundaries. In this study, the adsorption kinetics at the solid/solution interface was investigated by the fractal-like approach. The fitting performance of the fractal-like Bohart–Adams, Thomas and Yoon–Nelson models was validated by different adsorption systems. The fractal-like breakthrough models with larger Adj. R2 and smaller χ2 values could better describe the selected fixed-bed adsorption systems. Moreover, this work discussed the mathematical relationships between the breakthrough models, revealed the physical meanings of the corresponding parameters and explained the rate profiles. The Bohart–Adams, Thomas and Yoon–Nelson models represented the identical fitting curves. The terms q0m/vc0 and a0x/uc0 were the operating time required to reach 50% breakthrough. The shape of the rate profiles was analogous to the Gaussian distribution. Some mistakes and inconsistencies with respect to application of the Bohart–Adams model were specially pointed out. This work may help readers to better understand the adsorption process in the fixed-bed column and provide useful information for the design of adsorption systems.