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·2CaO· 5B₂O₃·16H₂O 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 SO₄^2- on the dissolution process, using H₂SO₄, HCl + H₂SO₄ and H₂SO₄ + Na₂SO₄ solutions. The analysis of the experimental data show that increasing SO₄^2- concentration reduced dissolution rate because of the precipitation of a solid film of CaSO₄ and CaSO₂·H₂O, but increasing H₃O⁺ acid concentration increased the dissolution rate.