Titanium and iron dissolutions from ilmenite by acid leaching and microbiological oxidation techniques

Abstract

This research was concerned with the solubility of ilmenite (Tin Tailing) in acids (sulfuric, hydrochloric, oxalic and citric) and bioleaching by Aspergillus niger, Penicillium citrinum and Bacillus megaterium. Ilmenite concentrate was soluble in 1.5 M sulfuric acid and 1.5 M hydrochloric acid solutions at 90 °C. However, improved leaching was obtained with 8 and 12 M sulfuric acid solutions. The chemical leaching results for different stirring speeds showed that a speed of 750 rpm was favourable to iron and titanium dissolutions. Metal dissolution rate can be enhanced with increasing leaching time. The optimum percentages of iron and titanium extraction occurred at 750 rpm for 6 h leaching in 8 M sulfuric acid solution and amounted to 64 and 57%, respectively. However, the optimum condition of chemical extraction was 1 M citric acid, which is considered weak, 750 rpm for 20 h extraction time at 90 °C. This led to the maximum titanium concentration of 63% that was comparatively very high compared with low iron dissolution of only 11%. Spores of A. niger and P. citrinum solutions were individually transferred at the culture ratio of 1: 0, 0: 1 and 1: 1 in a shake flask containing Sabouraud dextrose medium. The flasks were incubated in a rotary shaker at 30 °C and 200 rpm. The bioleaching experiments after 35 days gave the highest iron extraction of 0.45% in the presence of pure culture (A. niger) and mixed culture (A. niger and P. citrinum), whereas the titanium dissolution was observed to be very low (<0.28% extraction). For the bioleaching, B. megaterium was subcultured in solution in a shake flask containing nutrient broth. The flasks were incubated in a rotary shaker at 30 °C and 200 rpm. The bioleaching experiments after 3 days gave the highest iron and titanium extraction of 0.2 and 0.4%, respectively. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.