USE OF SULFONIUM SALTS IN LIQUID/LIQUID METAL EXTRACTION

摘要

A metal is separated from a solution of its salt by contacting an acidic halide ion-containing aqueous solution of at least one metal salt with a liquid that contains at least one sulphonium salt and which mixes partly or not at all with the aqueous phase, after which the extracted metal may be removed from the extract phase. The sulphonium salt has an "effective chain length" (the number of atoms that participate in the longest chain) of at least 9, and preferably 15 to 25 atoms and the salt may contain a single sulphonium group or be a tertiary sulphonium salt. The sulphonium salt may be the chloride, such as di-n-dodecyl methyl sulphonium chloride, diisoamyl methyl and n-hexadecyl n-dodecyl methyl sulphonium chloride, C10- 18-alkyl dimethyl sulphonium methyl sulphate or di-n-octylmethylsulphonium chloride, and the solvent liquid may be chloroform, 1,2-dichloroethane, 1,2-dichloropropane and di (2-chloroethyl) ether. The halide ions may be chloride ions, and hydrochloric acid may be present. The starting material contains salts of Fe, Cu, Co, Cr, Ni, Zn and/or Mn, and may be an aqueous solution resulting from the leaching of ores, to which HCl has been added. Cobalt may for instance be separated from a solution to which 4-8N HCl has been added, or iron from one to which 1-4N HCl has been added. The aqueous and organic phases are brought into contact and stirred vigorously until equilibrium between the two phases is achieved, and then the extract phase treated with water or dilute HCl to extract the metal and regenerate the sulphonium salt. The extraction may be effected in a continuous phase or countercurrently: iron and/or copper may be extracted from cobalt and nickel; iron may be separated from copper; cobalt may be separated from nickel.