Successive Uranium and Thorium Separation from Leach Liquor of Ore Deposit of 5th Anomaly of Saghand by Solvent Extraction

The present work deals with successive uranium and thorium recovery from the sulfate leach liquor of the ore deposit of the 5th Anomaly of Saghand using liquid-liquid extraction technique, where trioctylamine (TOA) and di-(2-ethylhexyl) phosphoric acid (D2EHPA) were used. The solvent extraction of uranium by trioctylamine in kerosene was investigated using Taguchi method. The extraction parameters were pH, extractant concentration, contact time and aqueous/organic volume ratio. The optimum conditions were determined as the extractant concentration of 5%, aqueous/organic volume ratio of 1, pH=1.6 and the contact time of 3 minutes. Under these conditions, the uranium extraction percent was 98.7% in a single step extraction process. For a deeper investigation of the achieved results by Taguchi method, the effect of different parameters such as contact time, temperature, concentration of extractant, and pH were considered. Thorium extraction from uranium extraction raffinate was performed by D2EHPA 4% in kerosene at pH=1.5-2 in a three step extraction process. The kinetic studies showed that the extraction follows a second order  kinetics. The optimium conditions for the selective stripping (back extraction) of uranium and thorium from the loaded organic phases were obtained when 5.0 M nitric acid and 1 M sulfuric acide were used, respectively.