Crud in solvent extraction processing — a review of causes and treatment

An overview is presented on the various aspects affecting solvent loss through crud formation, encountered in many hydrometallurgical plants that employ solvent extraction processing. This crud, or stable emulsion mixed with solids, can be caused by properties of the feed solution, the solvent and its composition, the type of contactor selected and the method of operation. Cruds differ between plants and therefore treatment schemes and preventative measures are impossible to define without actual testing and evaluation. A summary of items for consideration in solving crud problems is given.