Papers by Author: M. Ranjbar

Abstract: In this paper, a central composite design was applied to optimize the bioleaching of iron from a kaolin sample containing 2.2% iron impurity by Aspergillus niger isolated from pistachio shell. The strains were inoculated into 500 ml flasks containing 100 ml media consisted of (g/l): sucrose 120; NH4NO3 0.45; KH2PO4 0.1; MgSO4.7H2O 0.3; FeSO4.7H2O 10-4; ZnSO4.7H2O 25×10- 5. The effects of initial pH, sugar and spore concentrations on iron removal extent were investigated. The two-level factorial design points were pH 2 and 5, sugar conc. 70 g/l and 130 g/l, spore conc. 9×107 and 35×107 spores/l. Also, the increase of dissolved iron, oxalic acid concentration, changes in pH value, and sugar concentration were registered. Consequently, after 10 days, the iron concentration of the best condition reached to 179.3 ppm that means 38.8% of the total iron content is removed. Furthermore, the data analysis showed that all the factors are significant, and the iron removal extent increases by increasing the initial pH to 4.4, sucrose content to 93.8 g/l, and spore concentration to 305.5 spores/μl, but further increase in each factor value has negative effect on the response.

Abstract: In this work, bioleaching of iron from a kaolin sample was carried out using two different strains of Aspergillus niger, and the effects of strain type, pulp density, and addition time of clay on the iron removal were investigated using a full factorial design. It is concluded that strain type has the most significant effect on the iron removal. Also, the highest removal extent was 42.8% that was achieved by using the strain isolated from pistachio shell at the pulp density of 20 g/l, when the clay was added at the beginning of the experiments. The results showed that for the experiments in which the clay was added in the first day of cultivation, the average organic acids concentration (citric acid: 5.6 g/l, and oxalic acid: 4.54 g/l) were higher in comparison to those experiments in which the clay was added in the third day (citric acid: 5.25 g/l, and oxalic acid: 2.87).

Abstract: Several studies and different successful commercial applications had demonstrated that bioleaching can be an innovative approach that is capable to provide mining industry opportunities for essential growth in the medium term[2-18]. To identify the commercial application potential of bioleaching in Iranian copper industry, a research program was initiated. The objective of the main part of this program was to evaluate bacterial leaching processes for copper recovery from (i) high grade ores and flotation concentrates and (ii) low grade ores and flotation tailings. The latest results of these studies indicates the general operability of the bioleaching in both cases. At optimum conditions, the copper extraction from low grade materials was more than 80% and that from high grade ores and flotation concentrates about 95%, which should be high enough to justify the process economically.