788
M. Maccagni and E. Guerrini
The EZINEX ® Process
The EZINEX
® Process, described through the block diagram shown in Fig. 2, is
a chloride-based leaching and electrowinning system able to process oxidized zinc
bearing materials. We have modified a little bit of the process and we are submitting
a patent to protect these new modifications that, for these reasons, we are not going
to be introduced in this paper.
The process now consists of four main operations:
• Leaching of Zn bearing materials
• Solution purification
• Zinc electrowinning
• Evaporation/crystallization.
We will now go into more detail on each operating unit, discuss the chemistry,
and define the potential issues.
The Leaching
The leaching solution, the zinc depleted electrolyte returning from electrolysis, is
a neutral pH solution of alkali and alkaline-earth chlorides containing significant
concentrations of ammonium chloride. In the leaching reactor, Zn oxide and other
heavy metal oxides and chlorides are taken into solution together with alkali chlorides
and a portion of the alkali earth salts. In the leaching reactor, the following reactions
take place:
Cementation
Evaporation &
Crystallization
Leaching
CZO
Chemicals
Residue
Cement
Zinc
powder
Plating
additives
Zinc
cathodes
Electrolysis
NH 3
NaCl/KCl
Fig. 2 The EZINEX® Process—block diagram
M. Maccagni and E. Guerrini
The EZINEX ® Process
The EZINEX
® Process, described through the block diagram shown in Fig. 2, is
a chloride-based leaching and electrowinning system able to process oxidized zinc
bearing materials. We have modified a little bit of the process and we are submitting
a patent to protect these new modifications that, for these reasons, we are not going
to be introduced in this paper.
The process now consists of four main operations:
• Leaching of Zn bearing materials
• Solution purification
• Zinc electrowinning
• Evaporation/crystallization.
We will now go into more detail on each operating unit, discuss the chemistry,
and define the potential issues.
The Leaching
The leaching solution, the zinc depleted electrolyte returning from electrolysis, is
a neutral pH solution of alkali and alkaline-earth chlorides containing significant
concentrations of ammonium chloride. In the leaching reactor, Zn oxide and other
heavy metal oxides and chlorides are taken into solution together with alkali chlorides
and a portion of the alkali earth salts. In the leaching reactor, the following reactions
take place:
Cementation
Evaporation &
Crystallization
Leaching
CZO
Chemicals
Residue
Cement
Zinc
powder
Plating
additives
Zinc
cathodes
Electrolysis
NH 3
NaCl/KCl
Fig. 2 The EZINEX® Process—block diagram