Sodium sulfate recovery from boric acid liquors

VALDEZ, SILVANA; ORCE, AGUSTINA; FLORES, HORACIO RICARDO; E MATTENELLA, LILIAN

INTERNATIONAL JOURNAL OF MINERAL PROCESSING

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2014 p. 23 - 28

0301-7516

Boric acid has multiple uses in several industries, the pharmaceutical, glass and ceramic industries being some of them. Its obtaining involves the addition of sulfuric acid to slurry of calcium?sodiumborate at 70 °C and, after the removal of insoluble undesiredmaterial, the crystallization of boric acid by cooling the clear solution to 15-25 °C. The residualmother liquor containsmainly sodiumsulfate, sodium chloride and boric acid in concentrations depending on the composition of the borate ore and the temperature at which the boric acid is recovered. The addition of methanol or ethanol to these liquors is proposed to recover selectively most of the sodium sulfate by salting-out. This separation of themain component of the solution would not only produce amore easily disposable liquidwaste but it would also reduce its over-all volume as it could be recycled into the main process. 98% of the sodiumsulfate can be recovered with a 7:3 volume to volume ratio of alcohol to mother liquor. The recovery is improved when the concentration of boric acid is reduced before the salting-out. Ethanol proved to be 35% more efficient for the selective precipitation process than methanol. Sodium chloride and boric acid do not coprecipitate with the sodium sulfate.