Abstract
Adsorption operations are widely used in the process industry for the purification and bulk separation of gaseous and liquid mixtures. In the last decades, such separation processes also played an important role in renal and liver replacement therapy. This chapter presents a short overview of the main aspects related to adsorption processes. In consideration of the specific scope of this book, only purification of liquid diluted systems, i.e. adsorption of one or more diluted species from a liquid solution, are covered. Furthermore, since in most applications adsorption is carried out in fixed bed columns, the chapter is focused on this operating mode. A particular emphasis is put on the use of mathematical models as a tool for gaining a deeper insight into the working principles and operation of adsorption units embedded in artificial organs.
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Notes
- 1.
For adsorption from gases, partial pressures are rather used.
- 2.
Though very common, the shape of the isotherm reported in Fig. 4.1 is not the only one that can observed experimentally. Lyklema [19] reports six possible classes of adsorption isotherms for dilute liquid solutions; however, the observed shape of the experimental adsorption isotherm depends also on the concentration range considered.
- 3.
The reference concentration could be the maximum solute concentration found in the considered process.
- 4.
A similar procedure can be applied also by considering the wider class of approximate solutions
$$\begin{aligned} q(r,t)=A(t)+B(t)\, F(r) \end{aligned}$$(4.16)where F(r) is an arbitrary monotonous function that satisfies the condition
$$ \left. \frac{\partial F}{\partial r}\right| _{r=0}=0 $$In this case, a different expression of \(k_{LDF}\) is obtained [23].
- 5.
A thorough treatise with specific applications to fixed-bed adsorption columns is proposed in [25].
- 6.
The linear and Langmuir isotherms satisfy this condition. The following results are applicable also for the rectangular isotherm, even if this isotherm is not differentiable for \(C=0\).
- 7.
That is by setting the amount of solute introduced in the column with the feed until breakthrough time to be equal to the overall amount of solute present in the column at that time
$$ vSC_{in}\tau _{BT}^{*}=[\varepsilon C_{in}+(1-\varepsilon )f(C_{in})]SL. $$ - 8.
A third differential equation, namely Eq. 4.9, must be included if the mass transfer model used accounts for intraparticle diffusion resistance.
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Annesini, M.C., Marrelli, L., Piemonte, V., Turchetti, L. (2017). Adsorption. In: Artificial Organ Engineering. Springer, London. https://doi.org/10.1007/978-1-4471-6443-2_4
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DOI: https://doi.org/10.1007/978-1-4471-6443-2_4
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