Removal of Impurities from Sepiolite by Gravity/Sizing Methods for Better Viscosity Development

Sepiolite, a natural strategic clay mineral within the phyllosilicate group, is utilized in numerous applications because of its physical, and rheological properties. In particular, outstanding rheological properties are utilized in areas including drilling mud, paint, cosmetics, adhesives, etc. Several studies have been performed for the purification of clays, such as air classification, calcination, hydrocyclone, and flotation, for different purposes. In this study, relatively easy physical upgrading methods involving hydroxyclone, Falcon, and shaking table have been tested with the aim of obtaining a high-viscosity sepiolite product for rheological applications. It is shown that dispersion time, particle size, and pH are the most critical parameters in the viscosity development of sepiolite. The results indicate that, depending on the dispersion time of the raw HS1 sepiolite sample used in this study, the highest quality rheological material remains in the size range of – 2 mm to + 1 mm. Below – 0.1 mm, the viscosity value of the sepiolite sample decreased to its lowest value of 6000 cP. The pH-dependent viscosity measurements of a raw HS1 sepiolite sample exhibited the highest viscosity value of 13,000 cP at its natural pH of 8.5. Polyacrylic acid sodium salt (PAA) is the most effective dispersing agent in the decantation process for the enrichment of HS1 sepiolite samples. Among the three gravity/sizing beneficiation techniques tested, the middlings product of the shaking table achieved the highest quality sepiolite product of 17,000 cP with 49.2 wt.% using the size range of – 2.83 mm to + 1 mm; this material is suitable for high-grade rheological applications.