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

Kanturk A. , Sari M. , Piskin S.

Korean Journal of Chemical Engineering, vol.25, pp.1331-1337, 2008 (Journal Indexed in SCI Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 25
  • Publication Date: 2008
  • Doi Number: 10.1007/s11814-008-0218-8
  • Title of Journal : Korean Journal of Chemical Engineering
  • Page Numbers: pp.1331-1337
  • Keywords: Sodium Metaborate, Sodium Borohydride, Synthesis, Crystal Structure, TG/DTG, Coats-Redfem, SODIUM-BOROHYDRIDE, THERMOGRAVIMETRIC DATA, THERMAL-DECOMPOSITION, HYDROGEN

Abstract

Sodium metaborate tetrahydrate (NaB(OH)(4)center dot 2H(2)O) was synthesized by reaction of anhydrous borax (Na2O center dot 2B(2)O(3)) with sodium hydroxide (NaOH) under conditions at 90 degrees C for 150 min. The structure was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscope (SEM) and Thermogravimetric (TG) analyses. Moreover, dehydration kinetics of NaB(OH)(4)center dot 2H(2)O was carried out under non-isothermal conditions and the Coats-Redfem method was applied to analyze the TG data for calculation of activation energies (E-a) and pre-exponential factors (k(o)) 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, E-a and k(o) were calculated as 50.89 kJ/mol and 26x10(4) min(-1) for region 1, 18.51 kJ/mol and 0.87x10(3) min(-1) for region II, 15.72 kJ/mol and 0.52x10(3) min(-1) for region III, 4.37 kJ/mol and 0.04x10(3) min(-1) for region IV and 37.42 kJ/mol and 8.56x10(3) min(-1) for region V, respectively.