Hydrometallurgical solvent extraction methods

A hydrometallurgical solvent extraction method for preventing or mitigating crud within a solvent extraction circuit, the method comprising

• mixing, within a mixing vessel or extraction column of a solvent extraction circuit, an aqueous metal ion solution with an organic solution of metal extraction reagent capable of binding with metal ions and transferring the metal ions from the aqueous solution to the organic solution to form a mixture, and
• allowing the aqueous metal ion solution and organic solution to phase separate from the mixture;
• wherein prior to mixing the aqueous metal ion solution and the organic solution, and prior to or during crud formation, a water-soluble or water-dispersible polymer comprising pendant sulfonic acid or sulfonate salt groups selected from the group consisting of sulfonated polystyrene;
• an addition polymer comprising at least one of styrene-4-sulfonic acid and 2-acrylamido-2-methylpropane sulfonic acid;
• naphthalene sulfonic acid-formaldehyde condensate;
• lignosulfonate;
• salts thereof;
• and mixtures thereof, is added to the aqueous metal ion solution, the organic solution, or to both the aqueous metal ion solution and the organic solution to prevent or mitigate crud formation within the mixing vessel, the extraction column and/or a settler after the mixing vessel, of the solvent extraction circuit.