A Revised Pseudo-Second Order Kinetic Model for Adsorption, Sensitive to Changes in Sorbate and Sorbent Concentrations
JAY BULLEN
Sarawud Saleesongsom
Dominik Weiss
10.26434/chemrxiv.12008799.v1
https://chemrxiv.org/articles/preprint/A_Revised_Pseudo-Second_Order_Kinetic_Model_for_Adsorption_Sensitive_to_Changes_in_Sorbate_and_Sorbent_Concentrations/12008799
<p>Much
contemporary research considers the development of novel sorbents for the
removal of toxic contaminants. Whilst these studies often include experimental
adsorption kinetics, modelling is normally limited to application of the pseudo-second
order (PSO) rate equation, which provides no sensitivity towards changes in
experimental conditions and thus no predictive capability. We demonstrate a
relatively simple modification of the PSO model, with the final form dqt/dt =
k’C<sub>t</sub>(1-(q<sub>t</sub>/q<sub>e</sub>))^2 where k’=k<sub>2</sub>*(q<sub>e</sub>*^2)/C<sub>0</sub>*.
We demonstrate that unlike the PSO model, this new rate equation provides first-order
dependence upon initial sorbate concentration (observed experimentally as x̄=0.829±0.417),
whilst rate constant k’ is significantly less sensitive to changes in C<sub>0</sub>
and C<sub>s</sub> than PSO rate constant k<sub>2</sub>. We demonstrate that
this model improves predictive capacity towards changes in C<sub>0</sub> and C<sub>s</sub>,
particularly when q<sub>e</sub> is calculated using the Langmuir or Freundlich
adsorption isotherm. Finally, we explore
how the new rate constant, k’, responds to changes in sorbent morphology,
identifying that particle radius is a better constraining parameter than
surface area. In this new equation, the conditionality of the rate constant
upon experimental conditions is significantly decreased, facilitating better comparison
of new results with the literature.<sup></sup></p>
2020-03-20 09:49:52
adsorption kinetics
kinetic model
kinetic modelling
kinetic modeling
largergren
ho and mckay
intraparticle diffusion
particle size
pseudo-second order
modelling