Boron elimination by chemical adsorption on magnesium hydroxide from a brine from the Salar de Diablillos

AGUSTINA ORCE; SILVANA VALDEZ

Congreso; Congreso Internacional ?Prospectiva, Retos y Desafíos de la Ingeniería Industrial; 2020

In the South American Puna, lithium is found in brines that besides NaCl also contain other ions such as K+, Ca2+, Mg2+, B4O72-, SO42-, HCO3-. In order to obtain lithium salts according to technical specifications, brines must undergo different concentration and purification stages. Of the purification operations, the one corresponding to the removal of magnesium is critical, since this element interferes with the precipitation of lithium salts as carbonate or phosphate. In general, magnesium is removed from brine by chemical precipitation using lime as a precipitating agent, so the operation does not involve the use of high cost reagents or technology. On the other hand, boron is usually removed from the brine in specific stages involveing the use of ion exchange resins and/or liquid-liquid extraction; consequently, the operating cost of these stages is high. Since boron present in brine can react with lime to form an insoluble calcium borate, it is expected that it can be removed by chemical precipitation, thus reducing the operating costs. In this work, the joint removal of magnesium and boron by chemical precipitation using lime as a precipitating agent was studied. We worked with a brine coming from the Salar de Diablillos located in the province of Salta in Argentina. It was demonstrated that boron is eliminated by adsorption on the surface of the hydroxide and an operation criterion was established according to the pH value reached by the brine, which allows precipitating approximately 100% of the magnesium and up to 70% of the boron.