Speciation of borate in aqueous solutions studied experimentally by potentiometry and Raman spectroscopy and computationally by DFT calculations

The speciation of borate has been studied by potential titration in 0.5 M NaClO4 and Raman spectroscopic titration at 25?. Five borate species including B(OH)(4)(-), B3O3(OH)(4)(-), B5O6(OH)(4)(-), B3O3(OH)(5)(2-), and B4O5(OH)(4)(2-) along with boric acid, H3BO3, are identified, and the corresponding formation constants are determined accordingly in the solutions with initial boron concentrations between 0.01 and 0.7 M. The attributions for the Raman shifts of the spectra at 874 cm(-1) to the ?(1) vibrational mode of B(OH)(3), 741 cm(-1) to ?(1) of B(OH)(4)(-), 610 cm(-1) to ?(1) of B3O3(OH)(4)(-), 525 cm(-1), 760 cm(-1), 915 cm(-1), and 994 cm(-1) to ?(1), ?(2), ?(4), and ?(3) of B5O6(OH)(4)(-), 612 cm(-1) to ?(1) of B3O3(OH)(5)(2-), and 563 cm(-1) (?(1a)) and 938 cm(-1) (?(1b)) to B4O5(OH)(4)(2-) are made by combining the speciation from potential titrations and deconvolution of Raman spectra with DFT calculations.

Automated summary

The speciation of borate species in 0.5 M NaClO4 solution is identified using potential titration and Raman spectroscopic titration. Five borate species and boric acid are determined and their formation constants are calculated. The vibrational modes and attributions of different borate species are determined using deconvolution of Raman spectra combined with DFT calculations.