Work-up of waste materials from barium or strontium sulfide leaching

A process for processing a waste leaching residue from barium sulfide leaching or strontium sulfide leaching to recover barium or strontium from said residue in the form of a solid containing barium sulfate or strontium sulfate, said process comprising reacting said waste leaching residue with

• a) an acid mixture formed by adding to a hydrochloric acid containing approximately 25 to 32% by weight of HCl a sulfuric acid containing approximately 80 to 100% by weight of H.sub.2 SO.sub.4 ;
• or
• b) an initial hydrochloric acid containing approximately 25 to 32% by weight of HCl, and then subsequently adding to the initial hydrochloric acid a sulfuric acid containing approximately 80 to 100% by weight of H.sub.2 SO.sub.4,
• at a temperature in the range from 60.degree. C. to the boiling point of the reaction mixture to form an acid solution and a solid, whereby the hydrochloric acid is used in at least the quantity required to dissolve any calcium and any iron contained in said waste leaching residue;
• and separating said acid solution from said solid.