Patent ID: 7666372

Claim:
A method of recovering valuable metals from a quantity of furnace dust comprising the steps of: a first leaching step wherein the furnace dust is leached at atmospheric pressure in a first leaching solution to produce a first leach liquor and a first leach residue, the first leaching solution comprising an aqueous mineral acid solution; separating the first leach liquor from the first leach residue alter the first leaching; a second leaching step wherein the first leach residue is atmospherically leached in a second leaching solution to form a second leach liquor and a second leach residue, the second leaching solution comprising a solution of aqueous HCl with a reductant; separating the second leach liquor from the second leach residue after the second leaching, and a zinc precipitation step wherein zinc is precipitated from the second leach liquor by treating the second leach liquor with a quantity of alkali, the quantity of alkali selected to adjust the pH of the second leach liquor sufficiently to precipitate out the zinc in the form of a zinc salt in a third residue leaving a third liquor and then separating the third residue containing zinc from the third liquor.