Prediction of half-life for adsorption kinetics in a batch reactor.

Abstract

Besides adsorption rate constant, the half-life was also a basic factor that described the characteristics of adsorption kinetics. However, the direct prediction of the half-life was still a problem to be addressed urgently. In this work, the parameter τ was introduced into the pseudo-first-order (PFO), pseudo-second-order (PSO), pseudo-nth-order (PNO), and the corresponding fractal-like kinetic models (fractal-like PFO, fractal-like PSO, and fractal-like PNO) to directly predict the half-life by changing the boundary condition, i.e., the replacement of qt = 0, t = 0 by qt = qe/2, t = τ. The fitting performance of these kinetic models after modification was evaluated by nitrate adsorption on polyaniline-modified activated carbon (PAN/AC) and phosphate adsorption on zirconium-loaded Ca-montmorillonite. The results indicated that this type of model modifications did not influence the fitting performance and that the half-life was easily obtained only by the curve fitting. The practical significance of this work was to simultaneously predict the adsorption rate constant and half-life using the modified kinetic models.