Molecular Dynamics Simulations and Spectroscopic Investigation of the Hydration, Dynamic, and Dielectric Properties of the {Na 2 CO 3 –H 2 O} System at 298.15 K across Various Concentrations

Sodium carbonate {Na 2 CO 3 } is a critical adjuvant in many industrial processes, such as glass production, papermaking, water treatment, and food and beverage processing. Although it has wide ranging applications, a comprehensive molecular-level understanding of its aqueous behavior is still scarce. An understanding of Na 2 CO 3 ’s interaction with water, especially concerning hydration, ion transport, and dielectric response, is critical to enhancing its effectiveness in real-world applications. In this study, we investigate the structural, dynamic, and dielectric properties of aqueous Na 2 CO 3 solutions in the concentration range from 0.11 to 1.07 mol kg –1 at 298.15 K. We apply both classical molecular dynamics simulations and experimental techniques, i.e., Fourier transform infrared (FTIR) and 13 C nuclear magnetic resonance (NMR) spectroscopy. Via the simulations, carried out using the CHARMM36 force field and SPC/E water model, we obtain accurate data regarding hydration shells, coordination numbers, self-diffusion coefficients, and ion pairing. Structural analysis revealed the presence of contact ion pairs and solvent-separated ion pairs, whose proportions changed as a function of concentration. Experimental spectroscopic data verified the computational findings. FTIR spectra indicated concentration-dependent alteration in O–H and C–O vibrational frequencies, reflecting alteration in the hydrogen-bond network. Similarly, NMR analysis indicated a systematic downfield shift of carbonate signals, reflecting alteration in hydration states. Together, these results highlight the concentration-sensitive nature of Na 2 CO 3 ’s structural and transport properties and underscore the value of merging molecular modeling with spectroscopy for interrogating the behavior of electrolytic systems in solution. These molecular-level insights provide valuable guidance for optimizing Na 2 CO 3 ’s function in diverse industrial applications, ranging from glass production and pulp delignification in papermaking to alkalinity control in water treatment and stabilization of food and beverage formulations.