چكيده به لاتين
Numerous researches have been conducted on the extraction of TiO2 from Ilmenite with Hydrometallurgy method that the majority of these researches were based upon the usage of inorganic acids for acid leaching. Using inorganic acids such as Hydrochloric acid and Sulfuric acid can cause many environmental problems. As a result, researchers have tried to find alternative methods for extraction of TiO2 from Ilmenite. Investigations show that using Alkali roasting of Ilmenite and leaching by organic acids can reduce the amount of waste produced during the process of TiO2 extraction from Ilmenite. The aim of this research is to use Alkali roasting of Ilmenite and acid leaching with Oxalic acid as a method for extraction of TiO2. The steps of each experiment include Ilmenite roasting with Alkali salt for 4 hours at given temperature; leaching of roasted Ilmenite with distilled water for 1 hour at room temperature and leaching with a mixture of Oxalic acid, Ascorbic acid and Ethanol at given temperature and calcination of the final product. At first, 12 experiments, called determining conditions, were performed by using a mixture of Oxalic acid, Ascorbic acid and Ethanol on the product of Alkali roasted Ilmenite with sodium carbonate. The proper conditions for acidic leaching of the main experiments were selected as 0.5 molar Oxalic acid, 0.005 molar Ascorbic acid and 48% Ethanol, 6 hours leaching time and leaching temperature of 75˚C. Results showed that using Ethanol caused an increase in the amount of recovery and using Ascorbic acid caused increases in the purity of extracted Titanium Dioxide. Next, 16 experiments of Alkali roasting by 4 Alkali Hydroxides and Carbonates salts of Sodium and Potassium at temperatures 800˚C and 900˚C, by the amount of salts equal to 1.1 and 1.5 times of reaction stoichiometric were conducted for 4 hours. Furthermore, in order to extract TiO2 from the product of these 16 experiments, the acidic leaching with constant conditions (which was a product of the condition determining experiments), was applied to each of them with assuming that a constant acid leaching, may be provided to compare the purity and recovery of products. The final results showed that if the roasting is performed at a temperature of 800˚C, the highest purity and recovery equal to 90.7% and 76.7% and by using potassium carbonate salt is obtained. Also, with roasting at 900˚C, highest purity and recovery of extracted TiO2 was related to potassium carbonate salt and equal to 93.5% and 78.8%, respectively.
Keywords: Alkali roasting, Ilmenite, Titanium dioxide, Oxalic acid, Ascorbic acid, Ethanol
