Recovery of uranium from enriched solution by a membrane separation process

We claim a method for concentrating uranium material from uranium enriched solution mining lixiviant containing uranium and calcium, comprising the steps of: (A) contacting the enriched lixiviant with a substance effective to alter the pH of the lixiviant, resulting in a change of the solubility of calcium in the lixiviant solution so that it may be conveniently removed, (B) removing any precipitate which may have formed in step A, (C) having the pH adjusted, enriched lixiviant contact a separation system, containing at least one semipermeable, ultrafiltration membrane having the characteristic of NaCl rejection, at 300 psi and 2 000 ppm salt concentration, of about 5 percent to about 20 percent capable of concentrating uranium, to concentrate uranium and pass a substantial portion of the lixiviant, to provide a uranium concentrate stream and a uranium barren stream containing low molecular weight cations, anions, and impurities