Magnesium hydroxide recovery from brines in the argentine pune

Abstract

Exploitation of brines in Argentina with economical content of lithium generates magnesium hydroxide as a residue of the purification operations by chemical precipitation. This paper deals with the recovery of magnesium from brine samples, from salar de Pozuelos (Salta), concentrated by evaporation. The precipitation tests were carried out at room temperature (20 ºC), using calcium oxide as precipitator agent in stoichiometric quantities and in excess of 2 000 mL. The reaction progress was determined in a reactor of 2,5 L capacity; the agitation speed was constant and equal to 200 rpm. Samples of 100 mL were taken after 5, 15, 30, and 60 minutes; the solids were immediately separated by vacuum filtration and the magnesium content in the liquids was determined by atomic absorption spectrophotometry. The reaction progress degree is independent from the initial concentration of magnesium but dependent on the pH value reached after adding the precipitating agent. Brines with high magnesium content (> 5 000 ppm) generate pulps with low degrees of filterability after purifying, a characteristic that does not vary even with the addition of flocculants to facilitate the filtration operation.

Keywords

• salmueras
• recuperación de hidróxido de magnesio
• salar de Pozuelos
• precipitación química
• sedimentación, filtración, floculante.