Abstract:
Fluoride is an element closely related to the health of organisms. Sodium fluoride is the most common fluoride salt in nature. The study of its speciation in solution plays an important role in evaluating the migration and conversion of fluorine in groundwater and the treatment of fluorine−containing wastewater. In this paper, using classical molecular dynamics, the potential of mean force (PMF) of Na
+−F
− ions pair was calculated by Umbrella Sampling. The association type and association constant at 25 ℃ were determined with the calculated PMF. The results show that there are three association types of CIP, SSHIP and SSIP in NaF solution, among which CIP and SSHIP are the two most stable types. However, in terms of relative content, the association type of sodium fluoride solution is mainly SSHIP and SSIP, and CIP only accounts for 4.2%. The calculated equilibrium constant of NaF is 2.271, which is in good agreement with the experimental results. The NaF concentration has a great influence on the radial distribution function and coordination number of Na
+−F
−, but a little effect on the relative content.