Method for the Selective Recovery of Bismuth From Solid Impurity Streams Generated During the Primary Production of Copper

Abstract

A method for recovering bismuth (Bi) from a solid impurity stream generated during the pyrometallurgical production of copper, wherein the method includes the steps of leaching the solid impurity stream in an acid medium at a pH under 0.5 to obtain a Bi-rich leachate; and titrating the Bi-rich leachate at a pH between 1.0 and 3.5 by using a strong base to obtain a precipitate of bismoclite (BiOCl). In a related aspect, the invention also relates to a method for the recovery of valuable materials and for the safe disposal of toxic contaminants from a solid impurity stream generated during the pyrometallurgical production of copper.

1 . A method for recovering bismuth (Bi) from a solid impurity stream generated during the pyrometallurgical production of copper, wherein the solid impurity is dust from a Cu converter source consisting of dust collected in an electrostatic precipitator (ESP), and wherein the method comprises the steps of:
 a) Leaching the solid impurity stream in an acid medium at a pH under 0.5 to obtain a Bi-rich leachate, wherein the acid medium is HCl or a combination of HCl and H 2 SO 4 ;   b) Titrating the Bi-rich leachate at a pH between 1.0 and 3.5 by using a strong base to obtain a precipitate of bismoclite (BiOCl).   
     
     
         2 . The method according to  claim 1 , wherein the HCl is 10-16% HCl, preferably 16% HCl, or wherein the combination of HCl and H 2 SO 4  is 10-16% HCl, preferably 16% HCl, and 5-15% H 2 SO 4 , preferably 5% H 2 SO 4 . 
     
     
         3 . The method according to  claim 1  wherein the method comprises, prior to step (a), a step (a1) of leaching the solid impurity stream in a first acid medium at a pH between 1 and 4 to obtain a first Cu-rich leachate and a first Bi-rich solid, wherein the first Bi-rich solid is then leached in place of the solid impurity stream of step (a). 
     
     
         4 . The method according to  claim 3 , wherein the first acid medium is H 2 SO 4 , preferably wherein the first acid medium is 5-15% H 2 SO 4  or 50% H 2 SO 4 . 
     
     
         5 . The method according to  claim 1 , wherein the method comprises, prior to step (a) but after step (a1), a step (a2) of washing the solid impurity stream in step (a) or the first Bi-rich solid obtained in step (a1) in water, preferably MilliQ water. 
     
     
         6 . The method according to  claim 1 , wherein the method comprises, after step (b), a further step (c) of washing the precipitate of BiOCl obtained in step (b) in water, preferably MilliQ water. 
     
     
         7 . The method according to  claim 1 , wherein the method comprises, after step (b) or after step (c), a further step (d) of calcinating the precipitate of BiOCl at a temperature between 300-400° C. 
     
     
         8 . A method for the recovery of valuable materials and for the safe disposal of toxic contaminants from a solid impurity stream generated during the pyrometallurgical production of copper, wherein the solid impurity is dust from a Cu converter source consisting of dust collected in an electrostatic precipitator (ESP), and wherein the method comprises the steps of:
 a) Leaching the solid impurity stream in a first acid medium at a pH between 1 and 4 to obtain a first Cu-rich leachate and a first Bi-rich solid, wherein the first acid medium is H 2 SO 4 ;   b) Optionally, washing the first Bi-rich solid obtained in step (a) in water, preferably MilliQ water, to obtain a second Cu-rich leachate and a second Bi-rich solid;   c) Leaching the first Bi-rich solid obtained in step (a) or the second Bi-rich solid obtained in step (b) in a second acid medium at a pH under 0.5 to obtain a Bi-rich leachate and a Pb-rich solid, wherein the second acid medium is HCl or a combination of HCl and H 2 SO 4 ;   d) Titrating the Bi-rich leachate at a pH between 1.0 and 3.5 by using a strong base to obtain a precipitate of bismoclite (BiOCl) and an As-rich liquid;   e) Optionally, washing the precipitate of bismoclite (BiOCl) obtained in step (d) in water, preferably MilliQ water;   f) Optionally, calcinating the precipitate of BiOCl obtained in step (e) or the washed precipitate of BiOCl obtained in step (f) at a temperature between 300-400° C.;   g) Contacting the As-rich liquid with iron sulphate (Fe 2 (SO 4 ) 3 ) to precipitate scorodite (FeAsO 4 ·2H 2 O).   
     
     
         9 . The method according to  claim 1 , wherein the strong base is NaOH. 
     
     
         10 . The method according to  claim 1 , wherein the dust from a Cu converter source comprises, as elements present at a concentration ≥1%, Cu, Zn, S, Pb, As, and Bi, wherein:
 Cu is present at a concentration of 20-24%, preferably 21%; 
 S is present at a concentration of 10-14%, preferably 12%; 
 Zn is present at a concentration of 10-14%, preferably 12%; 
 Pb is present at a concentration of 6.0-8.0%, preferably 6.9%; 
 As is present at a concentration of 3.0-5.0%, preferably 3.8%; 
 Bi is present at a concentration of 1.0-2.0%, preferably 1.5%.