Structure of aqueous potassium tetraborate solutions by X-ray scattering

摘要

The borate species in aqueous potassium tetraborate solution were obtained according to the chemical species distribution diagram and the Raman spectrum. X-ray scattering is used to study the solutions with salt-water molar ratios of 1: 25, 1: 20 and 1: 15 at 298 and 323 K. The model calculation and model refinement programmes are used to calculate the structure parameters r_(i-j), b_(i-j) and n_(i-j). It manifests that the first hydration distance of K~+is ~0.29 nm, with an average hydrated number of 8.0. The hydration bond peak is around 0.278 nm and the coordination number is from 1.9 to 2.4. Borate anions coordinate with K~+ ions in the mono-dentate form, the average distance of K-B is 0.38 nm. The distance of B-H_2O in hydrated anion is from 0.37 to 0.38 nm with the hydrated number 4-9. The other interaction such as water shared pair interaction is also discussed.