Adsorption Kinetics in Aqueous Systems

Adsorption kinetics in aqueous systems describes the rate at which solute molecules accumulate at the surface of a solid phase from a liquid medium. This field bridges fundamental transport phenomena with practical applications in water treatment, resource recovery and environmental remediation. Key processes include external film diffusion, intraparticle diffusion and surface reaction steps that collectively govern the overall uptake rate. Empirical kinetic models such as pseudo-first-order and pseudo-second-order are widely used to fit experimental data, yet these often mask the underlying transport mechanisms. Advances in phenomenological modelling have shown that macropore diffusion and shrinking-core concepts yield physically meaningful parameters, enabling predictions across different reactor configurations. Recent efforts have also highlighted the importance of initial time-point accuracy, statistical rigour and stochastic approaches that account for experimental variability. Together, these developments have refined our understanding of rate-limiting steps and facilitated the design of more efficient adsorbents and reactors. Global challenges such as removal of emerging contaminants, heavy metals and radionuclides underscore the societal importance of accurate kinetic descriptions and the integration of mechanistic models into scale-up protocols.

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Adsorption Kinetics in Aqueous Systems publication trend

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Technical terms

Adsorption kinetics: The study of rates at which solute species accumulate on a solid adsorbent surface from a liquid phase.

Pseudo-first-order model: An empirical kinetic expression assuming the rate is proportional to the difference between equilibrium and instantaneous adsorption.

Pseudo-second-order model: An empirical kinetic model that assumes the adsorption rate is proportional to the square of the difference between equilibrium and current uptake.

Intraparticle diffusion: Transport of adsorbate molecules within the pores of a solid phase, often a rate-limiting step in adsorption.

Macropore diffusion: Diffusion of solute through large pores or channels in an adsorbent, described by Fick’s laws at the macroscopic scale.

Shrinking-core model: A mechanistic framework where adsorption proceeds inward from the outer surface, leaving an unreacted core that diminishes over time.

References

1. Modeling of sorption kinetics: the pseudo-second order equation and the sorbate intraparticle diffusivity. Adsorption (2013).
2. Kinetics of liquid phase batch adsorption experiments. Adsorption (2020).
3. Applying Linear Forms of Pseudo-Second-Order Kinetic Model for Feasibly Identifying Errors in the Initial Periods of Time-Dependent Adsorption Datasets. Water (2023).
4. A Stochastic Model for Adsorption Kinetics. Adsorption Science & Technology (2021).