Investigation of Effective parameters for Talc Recovery from Talc-Carbonate Schist of Swat Area by Flotation and Leaching

Abstract

Talc is hydrated magnesium silicate with chemical formula Mg3Si4O10(OH)2. Pure talc is an extreme rarity and it is mostly associated with undesired minerals, in its natural form. This work is an endeavor to investigate the effective parameters for talc recovery from talc carbonate schist of Swat, Pakistan by flotation and leaching techniques. Detailed characterization of carbonatic talcose rock was first carried out followed by the beneficiation studies. Thorough, investigations were made to find grain size of talc in original rock, petrography, chemical composition, talc content in the original rock and the nature of associated mineral impurities. XRF spectrometer analysis revealed the chemical composition and presence of carbonate minerals, Quartz and muscovite as elemental impurities. Similarly, the existence of detrimental elements in the phases and talc content in the rock was determined through phase analysis using heavy media. Grinding optimization study indicated -45 microns as talc liberation size. This was a pre requisite to investigate and devise beneficiation techniques. Froth flotation and leaching techniques were used in the beneficiation studies to separate talc from associated impurities. Multiple tests were conducted at different parameters. Two step flotation using AF65 (Cyanamid) as frother, Sodium hexametaphosphate as depressant for carbonates, equal mixture of oleic acid and kerosene oil as collector gave encouraging results. It was found that talc can be separated as float at pH (6.0±0.2) in rougher flotation, frother dosage 0.10kg/ton, and in cleaning flotation at collector dosage of 1.2kg/ton. Talc concentrate at recovery of 60% with a grade of 92.50% from an ore containing 55-68% talc was obtained. The concentrate from flotation was further upgraded by leaching with acids to improve its whiteness. Mixture of HCl and SnCl2 as leaching agent was effective and gave better results. It reduced iron content from 3.05% in the concentrate to 2.51% in the final leached product and whiteness also improved up to 82% from 51% of original talcose rock. The process developed through this research would be utilized not only for the up gradation of low-grade talc of swat area emerald mines deposits, but also for the indigenous deposits of such nature anywhere in Pakistan.