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4. MODERN TECHNOLOGIES OF PURE LEAD PRODUCTION
 
4.1. Fire refining of blister lead 
 
In flame refining of lead, the process of decoppering by liquation is first carried 
out. Liquation cleaning is based on low solubility of copper, nickel, cobalt in lead at 
low temperature. When lead is cooled, copper and its compounds with arsenic and 
antimony crystallize at a density of about 9 g/cm
3
.
These crystals are lighter and float 
to the surface of the bath, forming copper slips. 
The process of fire refining of rough lead is a very complex process, which 
includes several stages, such as copper removal, tellurium removal, removal of tin, 
arsenic and antimony, silver removal, zinc removal, bismuth removal. Therefore, crude 
lead is subjected to electrolytic refining after flame purification from non-ferrous 
metals. 

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4.2. Electrolytic refining of blister lead 
Lead electrolysis is used not only for de-bismuthizing lead, but also for cleaning 
lead from all its impurities, including rare metals. The normal electrode potential of 
lead is -0.126 V. An electrode is prepared by pouring the crude lead from the flame 
treatment into anode molds. The main processes of lead electrolysis: 
- At the anode: Pb – 2e = Pb
2+ 
(lead oxidizes and dissolves); 
- At the cathode: Pb
2+ 
+ 2e = Pb
0 
(dissolved lead is reduced). 
As an electrolyte, a mixture of fluorosilicic acid - H
2
SiF
6 
(8-10%) and lead 
fluorosilicate - PbSiF
6 
(6-8%) is added to the solution. 
Electrolysis is carried out in concrete or reinforced concrete baths covered with 
vinyl plastic or acid-resistant tiles. Electrolysis indicators: 
1) current density - 130-180 A/m
2 
; 
2) voltage in the bath - 0.4-0.7 V; 
3) electrolyte temperature - 35-50 °C; 
4) current yield - 90-96%; 
5) electricity consumption - 110-150 kWh/t of lead. 
At the anode, a slime (clay) containing 12-20% lead, 4-5% silver, 6-15% copper, 
up to 30% antimony and up to 10% arsenic is formed in the form of a loose shell. After 
3-6 days, the slurry (mud) is cleaned and sent for processing. Anodes are 70-80% 
recycled.