LEAD RECOVERY FROM LEAD-SILVER RESIDUES OF ZINC REFINERIES

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Anglesite

By: Adolfo Ríos Pita G.

 

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Lead is present as sulfate in " lead-silver " residues of zinc refineries working with the jarosite method.We succeded in extracting lead as pigment grade lead sulfate using a wet extraction procedure

Leaching these residues with 3 times the stoichiometric amount of sodium hydroxide, at room temperature. This operation obtains a soluble compound of lead: Sodium orthoplumbate and a solid residue containing Silver.

( 120 oz/st, starting with a head of about 40 oz/st ) and SiO2 ( silicon dioxide ). Solid residue is filtered and the lead solution is precipitated using sulphuric acid, obtaining pigment grade lead sulfate and a solution of sodium sulfate which can be used in the plant for the precipitation of iron 3+ as jarosite.

 

 

 

 

 

TREATMENT

 

Lead extraction

a)PbSO4 + 4 NaOH = Na2Pb ( OH) 4 + Na2 SO4

Lead sulfate precipitation

b)Na2Pb ( OH )4 + 2H2SO4 = PbSO4 + Na2SO4 + 4H2O

Sodium Sulphate is used to obtain jarosite as follows:.

c)3Fe2( SO4 )3 + Na2SO4 + 12 H2O = 2 NaFe3( SO4 )2( OH )6 + 6 H2SO4

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