Purification of Boric Acid by Washing

HORACIO R. FLORES; SILVANA K. VALDEZ

Handbook on Borates: Chemistry, Production and Applications

Nova Science Publishers

Lugar: Nueva York; Año: 2009; p. 399 - 408

Argentina produces boric acid from ulexite and sulphuric acid as raw materials. All the boric acid produced is exported, mainly to Brazil. It has become one of the most important commodities for economy of the northwestern region of the country in the last ten years. Boric acid market price depends on the impurities contained. Sanctioned impurities include chlorides, sulphates, iron, calcium and arsenic. Therefore, raw material quality, the obtaining method and the solvent used are of main importance to obtain high quality crystals and, as a consequence, a better market price. Moreover, pollution has become an important matter to be considered. Lately, it has become extremely important to improve methods tending to get the best quality at minimum cost, considering not only the economy of the process but also the environmental preservation. Sodium chloride and sodium sulphate are water soluble. So, they can be lessened by washing the crystals with fresh water. This chapter shows the economic advantages involved in the high quality boric acid market, and the results of washing boric acid by “displacement” and by “repulpation”. It is demonstrated that the choice of the method depends on the way that the pollutant is presented (superficial or ocluded). The influence of the amount of washing water and the washing method chosen over the  washing efficiency and the crystal composition are analyzed. The results show a possibility to obtain better boric acid quality and then better market price, which would represent a considerable source of income for the boronic South American region.