Beneficiation studies on a low grade kyanite-sillimanite sample (D3S2) from Dahagaon area, Nagpur

Abstract

A sample of the low grade kyanite-sillimanite designated D3S2 and received from the Director of Geology and Mining, Government of Maharashtra, Nagpur, was subjected to exhaustive beneficiation studies at National Metallurgical Laboratory. The sample assayed 38.40% Al2O3, 52.0% SiO2, 0.35% TiO2, 0.95% MgO, and Quartz were the major gangue minerals followed by minor was fairly free from these minerals at about 100 mesh size. Gravity and flotation methods were employed for removal of the gangue minerals from kyanite. Tabling of the sample after hydro-classification at 65 and 100 mesh sizes did not produce a high grade kyanite concentrate. Tabling of a 65 mesh sample after close sizing also did not produce a satisfactory grade of kyanite concentrate. Air classification was also attempted for the removal of muscovite from kyanite but without much success. An ionic flotation at a pH of 3.0, employing sodium sulfonate as collector for kyanite and citric acid and lactic acid as gangue depressants, followed by repeated cleanings yielded a kyanite concentrate assaying 59.90% Al2O, 36.6% SiO2, 0.71% TiO2, 0.4% MgO, 0.35% Fe2O3, 0.7% CaO. Trace % Na2O + K2O, with a kyanite recovery of 46%. Recirculation of the middlings is expected to improve the final kyanite recovery to about 66% for almost the same grade of concentrate. The concentrate satisfied the grade 'A' of ASTM requirements laid down for its use in refractories. Cationic flotation employing Aeromine 3037 at a pH of 5.5 for removal of muscovite followed by anionic flotation of kyanite using sodium sulfonate, produced a kyanite concentrate assaying 59.61% Al2O3 with a recovery of 52.80% kyanite.