Deeper Insights into the Bohart-Adams Model in a Fixed-Bed Column.

The Bohart-Adams model was one of the most widely used breakthrough models in column experiments. However, it usually provided a poor fit for the modeling of an asymmetric breakthrough curve. This work proposed the -order Bohart-Adams and fractal-like Bohart-Adams models. The former indicated a nonlinear decay process of the concentration of the adsorbate or residual capacity of the adsorbent, while the latter reflected a diffusion-limited process on the heterogeneous surfaces. The Bohart-Adams and modified Bohart-Adams models were mathematically equivalent. The applicability of the -order Bohart-Adams and fractal-like Bohart-Adams models was validated by norfloxacin and Cu(II) adsorption in a fixed-bed column. Compared with the Bohart-Adams model, the two new models had better fitting performance with higher and lower χ values, and all of the residuals were randomly distributed. The fractal-like Bohart-Adams and modified dose-response models provided the best fitting quality for the adsorption of Cu(II) ( = 0.9956 and χ = 7.56 × 10) and norfloxacin ( = 0.9991 and χ = 1.37 × 10), respectively. This work may provide a practical method for the modeling of the asymmetric breakthrough curves.