bluish-white color when freshly cut
11,34g/cm 3 , melting point 327 ° C
(10,69g/cm 3 )
- boiling point 1740 ° C (vaporizes at 550 ° C)
- bad heat and electrical conductor
- very soft, highly malleable

výroba plášťů zemních kabelů
- radiation shields
bullets and shot
lead -acid batteries
- alloys: PbSb, solder - P bSn,an tifriction alloy PbSnSbcompounds: carbonate, oxides

galena - PbS cerussite - PbCO
3 anglesite – PbSO
4
galena is the most important and widely used
- the main impurities: Cu, Zn, Sb, Fe, As, Sn, Ag, Bi a big amount of gangue

only in compounds galena - PbS cerussite - PbCO
3 anglesite – PbSO
4
selective&collective (PbZn) concentrate: 40-70% Pb
- other source(40%): waste batteries etc.

Pb is produced mainly by pyro. way

Roasting:removal of S, conversion of sulphide into oxide
Sintering: coarsening agllomerate
Reduction smelting
Purification of lead bullion

Roasting and sintering
Done together on a (Dwight-Lloyd)sintering machine
providing Pb content under
(mixing raw concentrate with returned agglomerate)
- partial removal of Sn and Sb as As
2
O
3 a Sb
2
O
3
2%

Reduction smelting in lead blast furnace
Obtain as much as possible lead bullion
Dissolve as much as possible noble metals in Pb
Move all gangue and Zn into slag
Separate Cu off Pb in form of matte

Reduction smelting in lead blast furnace
1. zone : under 400 ° C, drying and warming of charge .
2.
zone (reduction) : 400-900 ° C, removal of water, decomposition of carbonate & sulfate, reduction of oxides, sulfidization of Cu 3. zone (melting) : above 900 ° C, streaming down liquid Pb to crucible, dissolution of Au, Ag, Cu, As, Sb,
Sn etc. into lead bullion

Reduction smelting in lead blast furnace
charge: coke, air, sinter, CaO
Main reactions
2
PbO.SiO
2
+ CaO = PbO + CaO.SiO

Reduction smelting in lead blast furnace

Reduction smelting in lead blast furnace continuous taping, the principle of connected vessels
Construction of the furnace

Products of reduction smelting
lead bullion 90-96% Pb, 0,2-2,5% Cu, 0,5-5% Sb, 0,1-0,8%
As, 0,1-1,5% Sn, 0,06-0,5% Ag
slag 25 - 32% SiO
2
, 34 - 40% FeO, 10 - 16% CaO, 5 - 8%
Al
2
O
3
+ MgO, Pb, ZnO ( 30%)
BF gas
CO, CO
2
, SO
2
, vapor, N
2
, dust (3-50 g/m 3 , 40-80% Pb, toxic)

Refining of lead bullion
- removal of dross and Cu- removal of As, Sn, Sb,- removal
(recovery) of noble metals- removal of Bi

Refining of lead bullion removal of dross:
- stirring at 500 ° C
- physical impurities ascending to the surface of lead melt (difference in specific gravity)
- withdrawing as dross

Refining of lead bullion removal of Cu:
limited dissolution of Cu v Pb at low temp., higher affinity of Cu to S than that of Pb
- 1. step: lowering or increasing temperature of the melt just above of melting point of Pb
- 2. step (350 ° C): adding elemental S to form Cu
2
S
(under 0,002%)

Refining of lead bullion removal of Sn, As, a Sb
higher affinity with oxygen, comparing to Pb
- oxidation with air or with sodium nitrate
- oxidation with air:
500 ° C to remove Sn, 700 ° C-800 ° C to remove As, Sb

Refining of lead bullion removal of Sn, As, a Sb
- oxidation with sodium nitrate (Harris’ refining) + fused sodium hydroxide, 500 ° C
+ oxides As, Sb, Sn have acidic character, reaction with oxides of alkli metals to form arsenate, antimonate (V), stannate

Refining of lead bullion removal of Sn, As, a Sb
- oxidation with sodium nitrate (Harris refining) 2NaNO
3
=
Na
2
O +2.5 O
2
+ N
2
SnO
2
2Sb + 2.5 O
2As + 2.5 O
2
= Sb
2
O
5
2
=AsO
5
As
2
O
5
Sn + O
+ 3Na
2
2
=
O =
2Na
3
AsO
4
= Na
2
SnO
3
Sb
2
O
5
+ 3Na
2
O = 2Na
3
SbO
4
SnO
2
+ Na2O

Refining of lead bullion recovery of noble metals (Parkes’ method)
- de-silvering lead by adding metal Zn to form intermetallic
(higher melting point, lower specific gravity) compound
500C, stirring, cooling almost to consolidation, formation of foam containing noble metals (Ag, Au..)
- removal of Zn by vacuum

Refining of lead bullion removal of Bi atd1.) KrollBetterr’s method (under1%Bi)
- adding Pb-Ca (3- 4% Ca) and Mg metal
- slow cooling from 400 ° C to 360 ° C, foam forming atd2.) electrolytic refining (Bi >1%)
electrolyte : PbSiF
6
+ H
2
SiF
6
(fluorosilicate and fluorosilic acid)
- Pb cathodes
- Bi and noble metals report into do anode slugde