Effects of pectin and temperature on the diffusion of ions and water in saltwater membranes

In this study, we investigate the structural and dynamical characteristics of the biopolymer pectin, exploring its impact on ion transport, diffusion activation energy, and relaxation timescales within a saltwater environment (100 mM NaCl (aq.)) using classical molecular dynamics (MD) simulations. Our analysis of radial distribution functions (g(r)) reveals a notable preference of Na+ ions to interact more extensively with pectin compared to Cl- ions. Moreover, we observe slight variations in the strength of inter-ion interactions, with a modest decrease in ion-pectin interaction strength with increased pectin loading. Additionally, our findings indicate that sodium exhibits the lowest diffusion coefficient due to the presence of significant energy barriers among Na+, Cl-, and water molecules, following the sequence: D(water) > D(Cl-) > D(Na+) at any pectin loading and temperature conditions within pectin-saltwater membranes. Furthermore, our study demonstrates that viscosity, ion-pair relaxation timescales and ion-cage relaxation timescales exhibit monotonic increases with pectin loading while displaying the opposite trend with temperature. Overall, our simulations strongly endorse the use of biopolymer pectin as a highly promising and innovative option for a wide range of industrial applications, including flexible hydrogel electrolytes and saline water treatment.