Version 2 2024-02-29, 22:08Version 2 2024-02-29, 22:08
Version 1 2024-02-28, 23:08Version 1 2024-02-28, 23:08
journal contribution
posted on 2024-02-29, 22:08authored byJosé
C. Díaz, Jenny Park, Alyssa Shapiro, Harsh Patel, Lisby Santiago-Pagán, David Kitto, Jovan Kamcev
Membranes capable of differentiating between similarly
charged
ions could enable applications such as resource
recovery from naturally occurring waters and industrial wastewaters.
Understanding the factors that govern ion transport in these materials
is crucial for designing such membranes. This study investigates the
impact of membrane water content on the diffusion of monovalent cations
in negatively charged membranes by using absolute reaction rate theory.
The ion activation energy and entropy of diffusion in the membrane
both increase substantially when most of the water is structurally
bound. The increase in activation energy of diffusion is predicted
by a model incorporating Coulombic interactions between the membrane
fixed charges and counter-ions. The activation entropy of diffusion
in the low water content membranes increases with increasing size
of the hydrated cations, suggesting possible rearrangement in the
primary hydration shells of strongly hydrated cations, such as Li+ and Na+, during diffusion. These results suggest
that polymer tortuosity, Coulombic interactions, and water structure
govern monovalent cation diffusion in negatively charged membranes.