I am currently reading a paper titled "Polystyrene Nanoplastics-Enhanced Contaminant Transport: Role of Irreversible Adsorption in Glassy Polymeric Domain" (link here).
In the paper, the authors mention the term 'desorption hysteresis' as the mechanism of the interaction between nanoplastics and contaminants. Here's the relevant excerpt (from the introduction section):
... at low nanoparticle (i.e., “carrier”) concentrations significant facilitated transport of organic contaminants requires not only strong adsorption of contaminants to the carriers, but also significant desorption hysteresis (a collective term referring to both slow desorption kinetics and thermodynamically irreversible adsorption) of contaminants from the carriers. Desorption hysteresis can either be due to the physical entrapment of contaminants in the complex matrices of the carriers, or strong specific adsorptive interactions that lead to irreversible binding of contaminants to the carriers.
I am having some difficulty in understanding what do they mean by adsorption hysteresis. From what I've read, hysteresis is how the system in its current state is related to some past state, but I don't understand this concept fully.
Could someone please explain what is desorption hysteresis? I couldn't even understand the explanation in parentheses (right after the term in bold above). Is it about the rate of desorption of contaminants from nanoparticles?