Vibration Spectroscopic Analysis Of Aqueous Solution Of Borate

In crystal and aqueous solution,boron exist as a polyborate.Their existing forms and interaction among these different polyborate anions mainly depend on the pH, temperature of solution,concentration of boron in solution and concentration and existing forms of cation ion in solution.So,the structure of aqueous solution of borate is more complex than that of general salt. Vibration spectroscopy has been used to study the aqueous solution structure of borate of high boron concentration. But, the characteristic frequercies of ions can be obtained when the borates have the large solubility.Raman spectrum is more advantageous to inspect the characteristic frequencies of borate containing high boron-concentration.Because solvent water has a smaller influence on it. But, FT-1R spectrum technology can used to study the aqueous solution structure of borates of high boron-concentration. In this paper,we have studied existing forms of polyborate anions and their interaction in serval borate aqueous solutions by FT-IR difference spectroscopy and Raman spectra.(1) FT-IR difference spectroscopy and Raman spectra have been used to study the existing forms of polyborate anions in saturated aqueous borates solution in the system of the reaction of CS2CO3 with H3BO3 aqueous solution.The relations between the existing forms of polyborate anions and the crystallizing solid phases, Cs2B4O7.5H2O and CsB5O8.4 H2O have been gained.(2) Using the method of increasing solubility of borates which result from the acid effect of HCl or H3BO3 in solution,the FT-IR difference spectroscopy and Raman spectra of saturated borates solution in the dissolution and transformation of chloropinnoite have been studied. The influence of H3BO3 concentration, cation ions,temperature and pH in solution on the transformation products have been investigated. Therelations between the existing forms of polyborate anions and the crystallizing solid phases have been gained.(3) Supersaturated aqueous solution of MgO.B2O3-32%MgCl2-H2O which contain high concentration of MgCh have been prepared. And the Raman spectra of this solution during acidification/alkalization and dilution have been studied.The main existing forms of polyborate anions and their interaction in borate aqueous solution have been proposed through spectroscopic analysis.The important conclusion can been gotten through the above experimental results as follows:(1)The characteristic peaks of FT-IR difference spectra for certain polyborate ions in solution are diffrernt from those of Raman spectra .(2) Higher boron concentration and lower pH value of solution are helpful in the formation of polyborate anions with higher polymerization degree,respectively.(3) Higher concentration of cation are beneficial not only to the dissolution of H3BO3 but also to the polymerization of polyborate anions.(4) The dilution of borate is different from that of general salt.During dilution of borate,the pH value of solution usually not only gradually increase but also probably exceeds 7.