FT-IR spectroscopic study of phase transformation of chloropinnoite in boric acid solution at 303 K.

The dissolution and transformation of chloropinnoite in boric acid solution at 303 K has been studied using FT-IR difference spectroscopic technique. After equilibrium was reached, liquid and solid phases were separated and FT-IR spectra of each phase were recorded, FT-IR spectroscopic analysis of solid phases indicated that the transformation products, with the increase of boron-concentration in solution, were 2MgO x 3B2O3 x 15H2O (inderite), 2MgO x 3B2O3 x 15H20 (kumakovite), MgO x 3B2O3 x 7.5H2O, and MgO x 3B2O3 x 7H2O, respectively. The main polyborate anions and their interaction in each borate saturated aqueous solution have been proposed according to the FT-IR difference spectra of borate in liquid phase, and some assignments were tentatively given firstly. The relations between the existing forms of polyborate anions and the crystallizing solid phases have been gained.