Learn all about the lead nitrate action mechanism

Lead nitrate is a major component during ore leaching and the Merrill Crowe process.

Learn more about the action mechanism for this additive during these procedures.
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Leaching action mechanism 

Globally, cyanidation is the most widely used method for gold and silver leaching. There are several kinds of ores with gold and silver. Some are refractory, meaning that the gold and silver passivate during the process.

Poor cyanidation results occur frequently when sulfides are present in ore. Lead nitrate counters the negative effects of sulfides.

Lead nitrate works as follows:

• Lead binds with sulfide ions, creating lead sulfide and preventing a sulfide layer from building up around the gold and silver. This, in turn, prevents the extraction of the gold and silver.
  
  
• Lead reacts with AuS and Au₂S films/coatings which build up around the Au particles, encouraging Au dissolution.
  
  
• If ore contains Cu, lead nitrate prevents CuS film build-up, which is very harmful to gold dissolution.
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Merrill Crowe action mechanism

Merrill Crowe is a widely used technology for precious metal deposition from cyanide solutions.

Cementation is the resulting process, whereby the metal ions in solution (Au⁺ and Ag⁺) are reduced to metal state while another, more electronegative metal (Zn°) is oxidized.

The Zn powder reaction rate is slow, because Zn is quickly passivated.
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Lead nitrate works as follows:

• The lead nitrate Pb²⁺ ion acts as a reaction initiator/accelerator.
  
  
• It is reduced as metallic Pb on the Zn surface and causes negatively charged Au and Ag ions to deposit.
  
  
• Lead serves as a nucleation center, i.e. promoting solid particle formation with voids between them, thus preventing zinc passivation.
  
  
• Lead removes sulfide ions, preventing zinc sulfide formation.
  
  

Lead nitrate is an essential additive to promote gold and silver leaching. For any further questions please contact us for reviewing your process or request.

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