Method for treating waste containing precious metals and device for implementing said method

Abstract

The application relates to a method for treating waste containing precious metals, said method comprising the following successive steps: the waste is brought into contact with a composition based on molten lead; the mixture obtained is skimmed; and the skimmed mixture is refined by electrolysis in such a way as to recover the precious metals. The application also relates to a waste treatment installation for implementing said method.

1 . A method for treating waste containing precious metals, comprising the following successive steps:
 contacting the waste with a molten lead-based composition;   skimming the obtained mixture in order to recover supernatant materials; and   refining the skimmed mixture by electrolysis so as to recover the precious metals.   
   
   
       2 . The method according to  claim 1 , wherein, in the skimming step, residues are recovered which are treated by:
 contacting the residues with a second molten lead-based composition;   skimming the obtained mixture; and   recovering the skimmed mixture in order to provide at least one portion of the molten lead-based composition of  claim 1 .   
   
   
       3 . The method according to  claim 1 , wherein the step of refining the skimmed mixture comprises the following sub-steps:
 casting the skimmed mixture into anodes;   electrolysis of a fluorosilicic acid solution by using said anodes; and   recovering anodic sludges containing the precious metals.   
   
   
       4 . The method according to  claim 3 , comprising before, simultaneously or after the step of recovering anodic sludges, the step of:
 recovering lead and optionally tin cathode deposits in order to provide at least one portion of the molten lead-based composition and/or of the second molten lead-based composition.   
   
   
       5 . The method according to  claim 3 , wherein the step of refining the skimmed mixture comprises, after the sub-step of recovering anodic sludges, the following additional sub-steps:
 melting the recovered anodic sludges in the presence of oxygen;   skimming the molten anodic sludges; and   casting the molten and skimmed anodic sludges into ingots.   
   
   
       6 . The method according to  claim 1 , wherein each molten lead-based composition comprises from 0 to 50% of tin. 
   
   
       7 . The method according to  claim 1 , comprising, prior to the step of contacting the waste with a molten lead-based composition, the step of:
 extracting copper from the waste by selective dissolution.   
   
   
       8 . The method according to  claim 7 , wherein the copper extraction step comprises the following sub-steps:
 selectively dissolving the waste in the presence of sulfuric acid, iron sulfate and oxygen;   treating the obtained solution by filtration and/or electrolysis and/or precipitation;   recovering copper on the one hand and other metal impurities on the other hand.   
   
   
       9 . The method according to  claim 7 , comprising, prior to the copper extraction step, the following steps:
 combustion of the waste by pyrolysis, producing carbonaceous gases; and optionally   post-combustion of the carbonaceous gases.   
   
   
       10 . The method according to  claim 1 , further comprising a preliminary step of milling the waste and/or analyzing the milled waste. 
   
   
       11 . The method according to  claim 1 , wherein the precious metals comprise one or more metals selected from gold, silver, platinum, palladium, rhodium, ruthenium, iridium, osmium and mixtures thereof. 
   
   
       12 . The method according to  claim 1 , wherein the waste is selected from catalytic exhaust mufflers and electronic waste such as electronic cards. 
   
   
       13 . The method according to  claim 1 , wherein more than 90% by mass of the precious metals contained in the waste are recovered. 
   
   
       14 . The method according to  claim 1 , wherein the supernatant materials comprise ceramics, glass fibers and/or ferrite. 
   
   
       15 . An installation for treating waste containing precious metals, the installation comprising:
 at least one lead covering container;   a molten lead-based composition feed line, connected to the inlet of the lead covering container;   a pre-treated materials feed line, connected to the inlet of the lead covering container;   a skimmer associated with the lead covering container;   a skimmed mixture withdrawal line connected to the outlet of the lead covering container;   a refiner operably refining the skimmed mixture by electrolysis fed by the skimmed mixture withdrawal line; and   a precious metals withdrawal line, connected to the outlet of the refiner.   
   
   
       16 . The treatment installation according to  claim 15 , further comprising:
 a skimming residues withdrawal line, connected to the outlet of the skimmer;   at least one additional lead covering container, fed by the skimming residues withdrawal line on the one hand and by an additional molten lead-based composition feed line on the other hand;   an additional skimmer associated with the additional lead covering container; and   an additional skimmed mixture withdrawal line, connected to the outlet of the additional lead covering container and feeding the molten lead-based composition feed line.   
   
   
       17 . The treatment installation according to  claim 15 , wherein the refiner of the skimmed mixture by electrolysis further comprises:
 means for casting anodes;   Betts electrolysis means; and   means for recovering anodic sludges.   
   
   
       18 . The treatment installation according to  claim 17 , wherein the refiner of the skimmed mixture by electrolysis further comprises:
 means for recovering lead-tin, feeding the additional molten lead-based composition feed line.   
   
   
       19 . The treatment installation according to  claim 15 , further comprising:
 a copper extractor, one outlet of which is connected to the pre-treated materials feed line, and   a primary materials feed line, connected to the inlet of the copper extractor.   
   
   
       20 . The treatment installation according to  claim 19 , wherein the copper extractor further comprises:
 at least one selective dissolution container, fed by the primary materials feed line;   a depleted electrolyte feed line, connected to the inlet of the selective dissolution container;   electrolysis means;   means for transferring rich electrolyte, connecting the selective dissolution container to the electrolysis means;   means for stripping the cathodes; and   means for recycling depleted electrolyte, connected to the outlet of the electrolysis means.   
   
   
       21 . The treatment installation according to  claim 19 , further comprising:
 a pyrolysis oven acting on the waste, connected to the outlet of the primary materials feed line;   a waste feed line feeding the pyrolysis oven and optionally   a gas exhaust line at the outlet of the pyrolysis oven and feeding a post-combustion chamber.   
   
   
       22 . The treatment installation according to  claim 15 , further comprising:
 milling and analysis means fed by a raw waste feed line and feeding the waste feed line.