Recovery of lead and indium from glass, primarily from electronic waste material

Abstract

Lead and/or Indium cam be recovered from cullet containing indium and/or lead, such as cullet from CRTs and flat panel displays. A chloride salt melt including AlCl3 is used to dissolve the cullet. The melt may be electrolyzed and the lead and/or indium and other metals may be selectively electro-deposited from the salt melt. The two steps may be combined in a continuous process. The salts in the salt melt are not consumed but can be recycled, with exception of the flux due to formation of chlorine gas and alumina. It is also possible to recover lead and/or indium and other metals from the salt melt by vaporizing the respective chlorides and condensing them, or by leaching the salt phase in water and extracting the metals as hydroxides by hydrometallurgy methods.

1 . A process, for recovering lead and/or indium from glass containing PbO and/or indium oxide, primarily from electronic waste material, comprising:
 f) crushing the glass to produce a cullet,   g) forming a mixture consisting of by weight % of the mixture;
 60-95 of chloride salt composition consisting of at least two metal chlorides selected from the group consisting of alkali metal chlorides and alkaline earth metal chlorides, 
 5-30 of AlCl 3 , and 
 optionally 0-10 of halides, additional chlorides, sulfides and/or oxides, h) heating said mixture to form a salt melt, 
   i) dissolving the cullet in the salt melt, and   j) recovering at least one of lead and indium from the salt melt.   
     
     
         2 . The process as claimed in  claim 1 , wherein the salt composition consists of at least two of the salts selected from the group: NaCl, KCl, LiCl, CaCl 2 . 
     
     
         3 . The process as claimed in  claim 1 , wherein the salt composition essentially consists of by weight % of the salt composition, 3-20 Na, 30-70 KCl, 20-60 LiCl. 
     
     
         4 . The process as claimed in  claim 1 , wherein the salt composition essentially consists of by weight % of the salt composition, 10-50 NaCl, 2-20 KCl, 50-80 CaCl 2 . 
     
     
         5 . The process as claimed in  claim 1 , wherein the salt composition essentially consists of by weight % of the salt composition, 5-20 NaCl, 20-40 LiCl, 40-70 CaCl 2 . 
     
     
         6 . The process as claimed in  claim 1 , wherein the salt composition essentially consists of by weight % of the salt composition, 35-65 KCl, 20-50 LiCl, 5-20 CaCl 2 . 
     
     
         7 . The process as claimed in any one of  claim 1  or  6 , wherein the amount of AlCl3 is in the range of 5-20% by weight of the mixture. 
     
     
         8 . The process as claimed in  claim 1 , wherein the salt composition is selected to have a liquidus temperature below 700° C. 
     
     
         9 . The process as claimed in  claim 1 , wherein a weight ratio between the flux and cullet is on the order of 0.25 up to 1.5. 
     
     
         10 . The process as claimed in  claim 1 , further comprising holding the temperature for a time on the order of 4-8 hours during the dissolution step. 
     
     
         11 . The process as claimed in  claim 1 , wherein the recovery of at least one of lead and indium from the melt includes:
 electrolyzing the melt; and   selectively electrodepositing at least one of lead and indium.   
     
     
         12 . The process as claimed in  claim 11 , further comprising holding the melt at a temperature of at least 500° C. during the dissolution of the cullet and the electrolysis of the melt and at most 900°. 
     
     
         13 . The process as claimed in  claim 11 , further comprising electrolyzing the melt for a time on the order of 2 to 8 hours. 
     
     
         14 . The process as claimed in  claim 1 , further comprising collecting chlorine gas evolved during the electrolysis. 
     
     
         15 . The process as claimed in  claim 1 , further comprising vaporizing metal chlorides from the melt and condensing them for subsequent recovery of the metals of the condensed chlorides. 
     
     
         16 . The process as claimed in  claim 1 , further comprising leaching metal chlorides from the melt in water and extracting the metals as hydroxides by a hydrometallurgical method. 
     
     
         17 . The process as claimed in  claim 1 , further comprising recycling the chloride salts of the melt. 
     
     
         18 . The process as claimed in  claim 1 , further comprising recovering a processing residue consisting essentially of Al 2 O 3  and SiO 2  and using it for landfill, building construction, or as a raw material for refractory industry. 
     
     
         19 . The process as claimed in  claim 1 , wherein the glass contains PbO and comes from a funnel-shaped part and/or a neck part of a cathode ray tube of a computer screen or a television set. 
     
     
         20 . A process for recovering lead and/or indium from glass containing PbO and/or indium oxide, primarily from electronic waste material, said process including the steps of:
 i) crushing the glass to produce a cullet,   j) providing a crucible containing a chloride salt melt, at least one cathode and an anode connected to the salt melt, heating means for heating the salt melt, and an aluminum melt present at the bottom of the crucible, said aluminum melt forming the anode or a part of the anode,   k) providing an initiating chlorine donor to the salt melt for starting the reactions in the salt melt, said initiating chloride donor being aluminum chloride and/or at least one metal chloride that can be electrolyzed in step g) to form aluminum chloride,   l) holding the temperature of the salt melt and the temperature of the aluminum melt at a temperature where both are in liquid phase,   m) introducing said cullet into the liquid salt melt,   n) reacting the aluminum chloride as a chlorine donor with the cullet to form at least one of lead chloride and indium chloride being dissolved in the salt melt,   o) electrolyzing the salt melt and selectively depositing at least one of lead and indium at the cathode, optionally using a cathode bag, and in situ forming aluminum chloride at the contact surface between the aluminum melt and the salt melt, and   p) recovering at least one of lead and indium from the salt melt.   
     
     
         21 . The process according to  claim 20  wherein the initiating chloride donor includes aluminium chloride added to the mixture before heating it or to the salt melt, said aluminium chloride being added up to 20% by weight of the chloride salt mixture. 
     
     
         22 . The process as claimed in  claim 20 , wherein the salt melt and the aluminium melt is held at a temperature above 660° C. 
     
     
         23 . The process as claimed in  claim 20 , wherein the process is partly or wholly self-supporting during steady state by the aluminum chloride formed during the electrolyzing.