Structure of aqueous potassium metaborate solution

• Study shows that the main borate species in aqueous KB(OH)4 solutions is B(OH)4−.
• The average hydration number of the first hydration shells of K+ is 8.1 and the hydration distance is ∼0.294 nm.
• The B–O(H2O) distance in hydrated anion B(OH)4− is about 0.37 nm with an average hydrated number of 2.3.
• Contact ions KB(OH)40 exist in KB(OH)4 solutions, the distance of K–B is about 0.34 nm.
• Concentration and temperature also effect the hydration structure of B(OH)4.

The structure of aqueous potassium metaborate solutions has been confirmed by X-ray scattering, Raman spectra and species distribution calculation. The optimized structure of B(OH)4− was obtained by density functional theory calculation. The hydration distance and hydration number of K+ in aqueous potassium metaborate solution were given by X-ray scattering. The B–O(H2O) distance in hydrated anion B(OH)4− were determined to be 0.37 nm with the hydration number of 2.3 per hydroxyl(–OH). The K–B distance of the contact ions KB(OH)40 was measured to be 0.34 nm.