NEW SOLVENT EXTRACTION SYSTEM FOR URANIUM RECOVERY FROM LEACH SOLUTIONS USING SEAWATER

摘要

Uranium resource processing using seawater is highly demanded due to the shortage of underground water. Currently there is no solvent extraction (SX) system suitable for uranium recovery from leach solutions containing high chloride concentrations comparable to seawater.In order to develop a suitable solvent extraction system for uranium recovery from leach solutions using seawater, a number of SX systems were studied in terms of uranium extraction and separation from impurities, especially iron(lll). A new SX system has been developed with which >99% uranium was extracted from a synthetic leach solution using seawater, while only about 10% iron(lll) was extracted, leading to the separation factor of uranium over iron(lll) >1000. With the new SX system, uranium was almost completely extracted (>99%) in a pH range of 0.5-1.5 tested. Therefore, no pH adjustment may be needed for uranium extraction. Uranium maximum loading in 1% (v/v) of the organic system was >1.3 g/L. The kinetics of uranium extraction was fast, reaching equilibrium within 3 min. Except for vanadium, all other commonly associated impurities could be readily separated from uranium. After uranium extraction, the discharged raffinate solution can be recycled to the leach step due to the high chloride tolerance of the new SX system. This can significantly reduce the water usage and the environmental concern as well. Scrubbing with 0.5 M H_2SO_4 is efficient to remove the co-extracted iron. In a single contact, uranium stripping was 80% with 4 M H_2SO_4 solution, and almost complete (>98%) with 0.5 M Na_2CO_3 or (NH_4)_2CO_3 solution. A process using the new SX system has been proposed.