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 333K, 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 Å and coordination number is 7.7±0.9 in the first hydration shell around rubidium ion.

Hydrolysis mechanism of the cyclohexaborate anion: Unraveling the intricacies

“…Compared with pathway A, the hydrolysis reaction process of pathway B is relatively simple. In pathway B, the dissociated hydroxyl groups O ( 26) H (28) and H (27) of water molecules form bonds with B (10) and O ( 6 6 undergoes ring opening, so A is an ideal hydrolysis direction. In the existing research on the hydrolysis of double six-membered ring pentaborate ions, 35 Zhou compared two different hydrolysis reaction pathways at the same boron atom and discarded the one hydrolysis pathway that did not undergo ring opening after hydrolysis.…”

“…Studies have shown that the main factors affecting the distribution and interconversion of boron-containing species in borate solutions include temperature, pH, total boron concentration, and coexisting ions. 9,[17][18][19][20][21][22] On the other hand, x-ray diffraction [23][24][25][26] and extended x-ray absorption fine structure (EXAFS) 27,28 methods are also used to study the structure of borate solutions, giving the hydration number of anions and cations, hydration distance and ion pairs. These studies show that changes in the hydration configuration of cations affect the hydration structure and association structure of borate ions, and changes in the hydration and association structures of borate ions further affect the direction and progress of the hydrolysis, condensation, and depolymerization processes of borate species.…”