Studies on Dissolution Mechanism of Ulexite in Sulphuric Acid

Abstract

There is the largest fraction of the world's boron reserves in Turkey. Ulexite, which is one of the most widely available boron minerals, has the chemical formula Na2O center dot 2CaO center dot 5B(2)O(3)center dot 16H(2)O and triclinic crystal structure and is used usually in the production of boric acid. The present study concerns an investigation of the dissolution mechanism of ulexite in H2SO4 solution for high solid to liquid ratios and the effect of acid concentration, the effect of SO42- on the dissolution process, using H2SO4, HCl + H2SO4 and H2SO4 + Na2SO4 solutions. The analysis of the experimental data show that increasing SO42- concentration reduced dissolution rate because of the precipitation of a solid film of CaSO4 and CaSO2 center dot H2O, but increasing H3O+ acid concentration increased the dissolution rate.