Investigation on species distribution and EXAFS structure of aqueous rubidium pentaborate solutions

Abstract Based on the measured pH data and reported equilibrium constants, the main polyborate species formation existing in solution was investigated using the Newton iteration method at 298 and 333 K, and checked by the method of 11 B nuclear magnetic resonance (NMR) spectroscopy. The neighboring structure of rubidium ion was studied at room temperature, which the structural parameters, including the coordination number, interatomic distance of Rb-O and Debye-Waller factor, were determined by the synchrotron radiation extended X-ray absorption fine structure (EXAFS). The results show that the average interatomic distance of Rb-O is 2.93 ± 0.004 A and coordination number is 7.7 ± 0.9 in the first hydration shell around rubidium ion.