China Nonferrous Metallurgy

An extraction-stripping process was used in a hydrometallurgical refinery to recover rhenium (Re) from waste acid. However, the separation of impurities was not thorough, and the Re recovery was low. The test study explored the technical challenges in the extraction process, and compared the process test results of extracting-stripping Re with and without pre-treating waste acid. The test results indicate that: when the extractants (N235: sec-caprylic alcohol: kerosene) are mixed at a ratio of 20∶20∶60, the Re recovery reaches 88.42%; that washing the loaded organic phase with water or acid does not prevent the yielding of large amounts of Re-bearing crud during stripping with ammonium; that washing the stripping residue with hot water or acid does not produce favorable results, with low Re leaching efficiency and difficulty in separating Re and Bi; that adding the waste acid pre-treatment procedure brings about the best result in removing main impurities and concentrating rhenium; and that extracting and stripping the pre-treated Re solution can produce high quality ammonium rhenate, with extraction efficiency at 98%, and stripping efficiency at 99%.