Temperature-dependent structure of 3.5 wt.% NaCl aqueous solution: Theoretical and Raman investigation

Abstract

In the laboratory, the 3.5 wt.% NaCl aqueous solution is commonly used to simulate the seawater environment. The thermodynamic and kinetic research on the aqueous solution structure is intriguing, and it would aid in explaining the initial mechanism of the seawater-related physical and chemical phenomena. In this paper, the solution structure and evolution of the hydrogen bond network at the temperature range of the marine environment were obtained using classical molecular simulation and in-situ Raman spectroscopy. Specifically, the tetrahedral hydrogen bond structure was decomposed into two types: DDAAa affected by ions and DDAAn unaffected by ions. Furthermore, the enthalpy and entropy change of hydrogen bond evolution in the temperature range were calculated to be 14.05 ± 0.75 J·mol−1 and 53.38 ± 2.49 J·mol−1·K−1. This work lays the groundwork for preliminary mechanism research of life phenomena, physical properties, and chemical reactions in the marine environment.