Some aspects on the froth flotation process of ultrafine kaolin

This paper aims to upgrade an Egyptian kaolin by the conventional froth flotation technique to reduce Its anatase impurities (TiO₂ %) to be suitable for paper coating and fine ceramic industries. The flotation tests were carried out on a kaolin preconcentrate sample of about 80 wt. % below 1.95 μn. The tests were performed using sodium silicate as a depressant and oleic acid as a collector. The different operating parameters were studied. The results showed that the mechanical factors, such as the speed and time of conditioning, played the vital role in determining the efficiency of the flotation process for such ultrafine particles. For example, changing the dosage of collector or the pH of the medium have no influence on the grade of the produced concentrates when the flotation process was performed at low conditioning speed or for short conditioning time. However, the reverse trend was noticed when the flotation tests were carried out at high conditioning speed and after long conditioning time. Meanwhile, the presence of an activator or raising the conditioning temperature to about 40°C can reduce further the TiO₂ content. At the optimum operating conditions a concentrate of about 0.63 % TiO₂ with a % removal of 77.5 was obtained from a feed containing 1.52% TiO₂. Also, the whiteness degree was significantly improved to 79 in comparison with 56 for the flotation feed.