| 摘要 |
<p>PCT No. PCT/JP98/02479 Sec. 371 Date Jan. 15, 1999 Sec. 102(e) Date Jan. 15, 1999 PCT Filed Jun. 4, 1998 PCT Pub. No. WO98/58089 PCT Pub. Date Dec. 23, 1998A method for refining noble metals has a silver treating process including a nitric acid leaching step of silver, a purification step of the leaching solution, an electrolytic decomposition step of silver, and a recycling step after the electrolytic decomposition, wherein in the purification step, lime is added in order to precipitate the metallic impurities, such as selenium, tellurium, bismuth, and copper, by neutralization of the leaching solution, and in the recycling step, sulfuric acid is added to the solution after electrolytic decomposition to regenerate nitric acid for recycling use by precipitation of calcium in the solution as gypsum. Preferably, the refining method has a gold recovery process, as well as the silver treating process, wherein the residue of the nitric leaching of the crude silver is dissolved by chlorination and gold is recovered from the leaching solution by solvent extraction or reductive precipitation. High purity gold and silver can be readily obtained, and the refining time for gold is significantly shorter than that in conventional methods.</p> |
