A modified alkaline dissolution route of monazite was used to separate the hydrous oxide cake containing uranium, thorium, and rare earth elements from the phosphate matrix. It was found that uranium can be selectively leached by a mixture of sodium carbonate, sodium hydroxide, and hydrogen peroxide leaving thorium and rare earth elements as insoluble hydrous oxides. The factors affecting the extraction of uranium from the alkaline solution containing sodium carbonate and hydrogen peroxide were separately studied. Experimental results showed that tricarbonato uranium complexes are selectively extracted by Aliquat-336 diluted in kerosene from alkaline leach solution. Based on these results, uranium was purified from the leach solutions by extraction with Aliquat-336 diluted in kerosene with purity not less than 99%. (c) 2004 Elsevier B.V All rights reserved.