Synthesis, crystal structure and dehydration kinetics of NaB(OH)4·2H2O

다국어 초록 (Multilingual Abstract)

Sodium metaborate tetrahydrate (NaB(OH)4·2H2O) was synthesized by reaction of anhydrous borax (Na2O·
2B2O3) with sodium hydroxide (NaOH) under conditions at 90 oC for 150 min. The structure was characterized by Xray
diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscope (SEM) and Thermogravimetric
(TG) analyses. Moreover, dehydration kinetics of NaB(OH)4·2H2O was carried out under non-isothermal
conditions and the Coats-Redfern method was applied to analyze the TG data for calculation of activation energies
(Ea) and pre-exponential factors (ko) for different heating rates. It was determined that dehydration of sodium metaborate
tetrahydrate occurred in five steps. According to the Coats-Redfern non-isothermal model, Ea and ko were calculated
as 50.89 kJ/mol and 26×104 min−1 for region I, 18.51 kJ/mol and 0.87×103 min−1 for region II, 15.72 kJ/mol and 0.52×
103 min−1 for region III, 4.37 kJ/mol and 0.04×103 min−1 for region IV and 37.42 kJ/mol and 8.56×103 min−1 for region V, respectively.

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