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Zinc recovery from acidic aqueous streams
| Details |
Inventors: Baucom, Everett Ira;
Assignee: E. I. Du Pont de Nemours and Company (Wilmington, DE)
Primary Examiner: Vertiz; Oscar R.
Assistant Examiner: Hearn; Brian E.
Attorney, Agent or Firm:
A process for the recovery of metal values, principally zinc and copper, from an aqueous acidic purge stream in a hydrometallurgical process by contacting the stream containing the iron, copper and zinc sulfates, along with trace amounts of other metallic sulfates with calcium oxide to bring the pH in the range 3.0-4.0, thence with sufficient ammonia to form the soluble tetrammine sulfates of copper and zinc, then separating the copper from the zinc, e.g. by hydroxy oxime-solvent extraction and thereafter recovering the zinc as zinc oxide by converting the zinc tetrammine sulfate to the hydroxide and removing ammonia from the complex. |
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DETAILED DESCRIPTION OF THE INVENTION The recovery or separation process of the present invention is particularly useful in the separation of zinc and copper ions from other ions, e.
g.
iron, aluminum and magnesium with trace amounts of cobalt, manganese, molybdenum, bismuth, antimony, nickel and arsenic being present.
Typically these metal ions are obtained in acidic aqueous solution from conventional hydrometallurgical processes which leach metal values from ores or ore concentrates using acids at elevated temperature.
More particularly, the present process separates zinc and copper from iron and recovers zinc as zinc oxide from a leach solution obtained by countercurrently contacting an ore concentrate, e.
g.
chalcopyrite, with an aqueous solution of nitric and sulfuric acids at a temperature in the range 100.
degree.
-110.
degree.
C.
In a typical process the leach solution initially contains, based upon the iron and copper in the chalcopyrite, about 1.
4-1.
7 parts of sulfuric acid per part of copper, about 2.
0-3.
0 parts of sulfuric acid per part of iron, and about 2.
0-4.
0 parts of nitric acid per part of copper and water to produce a final solution containing about 4-9 parts of copper per 100 parts of solution.
After the leaching, the nitrate in the solution is then reduced to less than about 10 grams per liter in the presence of fresh concentrate and ferrous ion is generated.
After separating the liquid and solids from the leaching step, the liquid which contains at least 2.
7 parts of ferrous ion per part of nitrate ion is then heated to a temperature in the range 160.
degree.
-180.
degree.
C.
wherein the ferrous and nitrate ions react with the result that the nitrate concentration is reduced to less than about one gram per liter.
The resultant solution is contacted with ammonia and a molecular oxygen containing gas at a temperature in the range 160.
degree.
-180.
degree.
C.
to precipitate iron as ammonojarosite.
After the precipitate is removed the solution now containing less than about 5 grams/liter of iron is directed to electrolytic cells where 40-75% of the copper is recovered
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Heat Accumulators 
