Consideration of fractal and ion–water cooperative interactions in aqueous Na2SO4 and K2SO4 solutions by dielectric relaxation spectroscopy

• The mesoscopic water cluster shrinks and water transfers to hydration shells of aqueous Na2SO4 and K2SO4 solutions.
• The density of the water molecules perturbed by ions in the hydration shell almost linearly increases with salt concentrations.
• The number of water perturbed by ions is well beyond the first hydration shell.

This paper presents the analysis of the fractal and the ion–water cooperative interactions in aqueous Na2SO4 and K2SO4 solutions underlying the Cole–Cole symmetrical broadening and depicts the Cole–Cole relaxation process. Fractal analysis with α(ln(τ))α(ln(τ)) diagram from dielectric relaxation spectroscopy (DRS) draws a consistent microscopic picture of ion–water cooperative interactions in aqueous Na2SO4 and K2SO4 solutions. The density of the water molecules perturbed by ions in the hydration shell almost linearly increases with salt concentrations. The water molecules network perturbed by ions contributing to dielectric constant beyond the first hydration shell is obtained.