Unraveling overlapping processes in the sorption and in the release dynamics of DMSO vapor in paper

Abstract The sorption and release of gases in complex porous materials often involves multiple simultaneous processes. It is difficult to distinguish the dynamics of individual processes from experiments that only allow access to the combined overall dynamics of all processes taking place. This works shows for the case of dimethyl sulfoxide (DMSO) vapor interacting with paper as a porous matrix that it is possible to distinguish experimentally the dynamics of the sorption and release processes of two populations of differently sorbed DMSO molecules, even though the temporal evolution of the sorbed concentration shows no evidence of multiple processes. The key to separating the processes lies in the release behavior. DMSO release from paper saturated with DMSO is a superposition of short- and long-term processes, with release rates of 3 $$\times$$ 10 $$^{-4}$$ s $$^{-1}$$ and 1.1 $$\times$$ 10 $$^{-6}$$ s $$^{-1}$$ , respectively. Such different rates indicate the presence of two types of sorbed populations with distinct release dynamics. This inspires a strategy to separate the sorption dynamics of the two populations as well. A sorption experiment was designed to determine the concentration of DMSO sorbed in the paper at a certain exposure time, and again after the short-term release was complete. This procedure yields the concentration of each sorbing species as a function of time. Successfully separating the process dynamics is important for clarifying the nature of the processes, such as determining activation energies, and for correctly describing the temporal evolution of sorption and release mathematically. This strategy may help reveal the dynamics of simultaneous, mutually obscuring processes in other systems as well. Graphical Abstract