Investigation of Chemical and Microbial Leaching of Iron ore in Sulphuric acid

Investigations on the chemical and microbial leaching of a Nigerian Iron-ore in sulphuric acid have been carried out. The influence of physico-chemical parameters such as acid concentration, temperature, particle size and stirring speed on the chemical dissolution of the ore was investigated. The dissolution rates are significantly influenced by the temperature and acid concentration while the increase of percentage dissolved with stirring speed and particle size was very moderate. The rate of the reaction based on reaction-controlled process was found to conform with the shrinking core model: 1-(1-α)^1/3 = kt. With 12M H2SO4 and at a temperature of 80°C with a stirring speed of 36orpm and particle size 0.04-0.05mm, about 76.80% of iron-ore was dissolved within 120min. The activation energy of 38.29kJ/mole was calculated for the process. The reaction is first order with respect to H^+ ion concentration. An attempt to dissolve the ore via microbial action of thiobacillus ferroxidans was not successful. This has been attributed probably to very low sulphur content of the mineral.