| 摘要 |
<p>1,125,348. Extraction of metal values. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. 27 Feb., 1967, No. 9127/67. Heading C1A. [Also in Division C2] Metal values are selectively separated from an aqueous medium by liquid-liquid extraction, wherein an acidic aqueous medium containing halide ions and three or more metal values in solution and/or suspension is contacted with a cationic extracting agent to extract at least one of the metal values, whereupon the phases are separated from each other, and the raffinate phase is contacted with an anionic extracting agent to separate at least one further metal value from the aqueous phase, one or more of the respective metal values being subsequently recovered, if desired, from one or both of the extract phases and/or from the remaining raffinate phase. The mutual miscibility of the extracting liquid with the aqueous phase in each case is below 1%, and the contact between the aqueous and organic phases during the extractions is promoted by vigorous stirring until equilibrium between the phases is attained. Co-current or counter-current liquid-liquid extraction techniques may also be used. The cationic extracting agent may be a salt derived from an organic base, e.g. the onium compounds: sulphonium, ammonium and phosphonium salts in the halide or sulphate form having an " effective chain length " as defined of at least 9 atoms, used as a solution in an organic solvent, preferably chloroform. The normality of the acidic aqueous medium is not more than 2N, and the halide ions are preferably chloride ions, particularly in the form of NaCl. The cationic extraction agent is used to remove mainly Fe(ITI) from the aqueous medium which may be an acidic leach from ores containing the metal values as sulphates in dilute H 2 SO 4 . The anionic extracting agent may be a carboxylic acid and/or a salt thereof, e.g. " Versatic " acid (Trade Mark) and is applied as a solution in an organic solvent, preferably kerosene. The extraction of the raffinate phase with the anionic extracting agent is effected at a pH substantially at or above the pH of hydrolysis of the metal value to be extracted, but below the pH of hydrolysis of the other metal value(s) present. The pH is adjusted by neutralization with a base, the preferred technique consisting of simultaneous neutralization and extraction. Cu(II) is extracted in a pH range of 3.5 to 4À5 and Co(II) and/or Ni(II) in a pH range of 5À5 to 6À5. The organic extracts may be backwashed in each case with a dilute mineral acid, and the cationic and anionic extracting agents recovered can be used again.</p> |
