Hydrometallurgical extraction of Al and Si from kaolinitic clays

Abstract

Herein is presented the results of a study on the hydrometallurgic extractionand recovery of aluminum and silicon by leaching of kaolinitic clays with HF. Thestudied extraction parameters were: temperature, reaction time, solid/liquid ratio,concentration, and precipitating agent mass. In the leaching process, mineraldissolutions near 100% were obtained when working at 348 K, solid/liquid ratio2% w/v, HF 12% v/v, for 120 minutes. The HF leach liquor generated from thedissolution of kaolinitic clays contains H2SiF6 and H3AlF6. Studies were conductedto recover the two valuable fluorides as K2SiF6 and Na3AlF6 by precipitation withalkaline salts from the leach liquor. Phases of precipitated fluorides were identifiedby XRD and surface morphology by SEM. The purity of the K2SiF6 precipitate was98.8%, whereas for Na3AlF6, it was 89.3%. Also, both synthesized solids are ofhigh commercial value due to their industrial applications.