Hydration structure and ion transport in nitrate solutions for controlling water impurities in molten salts

Abstract Molten salts are crucial in heat transfer and storage when concentrating solar power; however, water impurities compromise thermal stability and accelerate corrosion. This study investigated the hydration structures and transport properties of KNO 3 , NaNO 3 , and their mixed salt (36:64) in aqueous solutions at 313.15 K by combining molecular‐dynamics simulations with single‐droplet drying experiments. Radial distribution functions, coordination numbers, ionic hydration radii, diffusion coefficients, and activation energies were analyzed across varying concentrations. The results indicate that above 5.0 mol/kg H 2 O, intensified ion competition disrupts the hydration shell; the Na–O w and K–O w coordination numbers decrease from 5.576 to 4.628 and 6.428 to 5.617, respectively; the diffusion coefficients decrease by >50%, restricting ion mobility and destabilizing the local structure; and the hydration competition index (ratio of Na–O w to K–O w coordination numbers) decreases from 0.87 to 0.78. These findings provide quantitative insights for reducing water impurities and improving molten‐salt formulations.