EXTRACTION OF HIGH QUALITY TALC FROM TALC-CARBONATE ROCK OF MINGORA EMERALD MINES BY FLOTATION AND LEACHING

Abstract

Talc is hydrated magnesium silicate with chemical formula Mg3Si4O10(OH)2. In natural form pure talc is an extreme rarity and it is mostly associated with undesired minerals like magnesite, calcite, dolomite, quartz, muscovite, hlorite, tremolite and iron bearing minerals. These associated minerals determine the quality of talc for industrial purpose and if in access, limits its applications. In present research work, beneficiation studies of carbonatic talcose rock of Mingora emerald mine located in District Swat, Khyber Pakhtunkhwa (KP), Pakistan were conducted to recover high quality talc out of the talc carbonate rock and to develop a technique for up gradation of indigenous non-commercial talc resources from other locations. These rocks host emerald crystals and the debris are dumped after excavation and extraction of emerald crystals. Controll of environmental threat caused by these rock dumps is an additional benefit of the research. Two step froth flotation process with AF65 (Poly propylene Glycol, Cyanamid) as frother, Sodium hexa metaphosphate 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 - 7±0.2 in rougher flotation and 10 - 11±0.2 in cleaning flotation, depressant dosage 0.10kg/ton, and collector dosage of 1.2 kg/ton. Talc concentrate at recovery of about 60 - 70% with a grade of 92.50% from an ore containing about 50 to 70% talc was obtained. The final concentrate was treated with various leaching reagents. Dilute HCl (30%) + stannous chloride (300 ppm) gave better results. It reduced iron content from 4.37% in the concentrate to 2.89% in the final leached product and whiteness also improved up to 80% from about 51% of original talcose rock. Some tests were also conducted to improve whiteness of leached products but with little improvement in results.