Effect of impurities on crystal growth rate of ammonium pentaborate


Sahin Ö. , Ozdemir M., Genli N.

JOURNAL OF CRYSTAL GROWTH, vol.260, no.1-2, pp.223-231, 2004 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 260 Issue: 1-2
  • Publication Date: 2004
  • Doi Number: 10.1016/j.jcrysgro.2003.08.020
  • Title of Journal : JOURNAL OF CRYSTAL GROWTH
  • Page Numbers: pp.223-231
  • Keywords: impurities, mass transfer, growth from solution, seed crystals, borates, CRYSTALLIZATION

Abstract

The effect of sodium chloride, borax and boric acid of different concentrations on the growth rate of ammonium pentaborate octahydrate crystals (APBO) was measured and was found to depend on supersaturation in a fluidized bed crystallizer. The presence of impurities in APBO solution increases the growth rate compared with growth from pure solution. It was found that the presence of sodium chloride, borax and boric acid decreases the reaction rate constant k(r), while it increases the mass-transfer coefficient, K, of APBO crystals. In pure aqueous solution, the crystal growth rate of APBO is mainly controlled by diffusion. However, both diffusion and integration steps affect the growth rate of APBO crystals in the presence of sodium chloride, borax and boric acid. The mass-transfer coefficient, K, reaction rate constant, k(r) and reaction order, r were calculated from general mass-transfer equation by using genetic algorithm method making no assumption. (C) 2003 Elsevier B.V. All rights reserved.