On the comparison of pseudo-first order and pseudo-second order rate laws in the modeling of adsorption kinetics

Abstract

In most works in the current literature about liquid/solid adsorption kinetics, the respective abilities of pseudo-first order and pseudo-second kinetics for describing the data are compared. In nearly all cases, it is concluded that the latter surpasses the former. The aim of this work is to point out that more caution should be exercised in this comparison. Indeed, it appears that the method generally used is flawed and that it unfairly favors pseudo-second order kinetics. A different method is proposed to analyze experimental results. It is employed here to reexamine experimental data taken from the literature.

Hierarchical Fe3O4‐derived organic/inorganic hybrids constructed by modified bio‐inspired functionalization: efficient adsorbents for water‐soluble methylene blue and mechanism

“…Finally, the adsorption reaches equilibrium in 2 h. Owing to the steric hindrance between solution phase and MB molecules adhering to the absorbent surface, the remaining adsorption sites are hard to occupy. Furthermore, the MB adsorption kinetics of our adsorbent is investigated by pseudo‐first‐order and pseudo‐second‐order models, as shown by the following two equations: …”

Development of a Novel Mixed Titanium, Silver Oxide Polyacrylonitrile Nanofiber as a Superior Adsorbent and its Application for MB Removal in Wastewater Treatment

“…Since the adsorbate residence time and reactor dimensions were controlled by the kinetics of the system, it is important to know the rate of adsorption during contaminant removal from wastewater. At this point, three kinetic models were used to analyze and simulate the adsorption data which are: pseudo first-order equation (PFO), 37 pseudo-second-order equation (PSO) 38 and intra-particle diffusion equation (IPD). 39 A linear form of pseudo-first order model is given by the equation:…”

Enhanced adsorption and slow release of phosphate by dolomite–alginate composite beads as potential fertilizer

“…The kinetics of phosphate uptake was investigated by measuring the time‐dependent SAC of the DA beads with both pure phosphate solution (Figure a) and synthetic wastewater (Figure b). All the time‐dependent SAC curves are best fitted with a pseudo‐first‐order model (Supporting Information Table ), which suggests that the adsorption is diffusion controlled in our DA composite system (Simonin, ). Previous studies using dolomite as the adsorbent have shown pseudo‐second order adsorption kinetics, which suggests the binding of the molecules onto the adsorbent surface to be the rate‐limiting step, that is, the adsorption onto dolomite was reaction‐limited (Yuan et al., ).…”