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This post was last edited by Confide in the wind on 2022-9-12 21:12. Question: **Okay, I’ve been studying the theory of pressure swing adsorption recently, and I came across information regarding the latest developments in mass transfer. Question 1: Assume that there is no mass transfer resistance within the adsorbent bed, meaning that the adsorption rate is infinite; in this case, the adsorbate moves in the direction of gas flow at its initial concentration of C0, similar to a piston moving in a cylinder, as shown in Figure 2-3(a). My view is that if there were no mass transfer resistance and the adsorption rate were infinite, the adsorbate would be completely adsorbed immediately, resulting in a concentration of 0 for the adsorbate. That is, along the height of the adsorption tower, the concentration of the adsorbate should be 0. The curve should be Y=0, rather than y=C0. Question 2 ； In fact, due to the presence of mass transfer resistance, as well as the effects of factors such as fluid velocity, adsorbent phase equilibrium, and adsorption mechanisms, the situation is not like that. When a gas mixture with an adsorbate concentration of CO passes through the adsorption bed, an S-shaped curve is first formed at the inlet of the bed; this curve is known as the adsorption front (or mass transfer front). Why is it an S-shaped curve? The text states that an S-shaped curve is formed first at the inlet of the adsorption bed – is there a time factor involved in this? It must have taken some time to form, right? ? Does this curve mean that the concentration is highest at C0 near the gas inlet, and is 0 at the farthest end? Is this a test measurement? Are there any reference articles? Thank you