BIR-Herbsttagung, 25. - 26- Oktober 2010 in Brüssel - Metall-web.de

METALL-FORSCHUNG
Fig. 2: Dependence of Zn yield from the time
granularity of zinc ash No.3 in 10% and 15%
HCl at ambient temperature
the copper recovery decreases. The
reason for that is cementing out with
zinc. By the leaching of the same fraction
of ash in 10% and 15% HCl the
maximum yield of zinc was obtained
after 20 minutes. Under these conditions
practically all zinc was leached.
Based on these results the most appropriate
concentration of the leaching
solution was set to 10% HCl; the
use of higher concentrations has no
practical meaning. The choice of 10%
HCl concentration for the leaching
of zinc ash is in accordance with the
concentration of the leaching solution
in the experiments of Dvořák and Jandová
[6]. The highest yield of Zn using
different concentrations of HCl (5%,
10%, 15%) is shown in fig. 4.
Effect of particle size on zinc
recovery
Based on the previous results, 10%
HCl was selected to assess the impact
Fig. 3: Dependence of Zn, Fe, Cu, Cd yield,
from the time, the grain size of zinc ash No. 3
in 5% HCl, at ambient temperature
602
of the ash grain size on the zinc yield.
To assess the impact of the grain size
on the zinc yield four fractions with
grain size 1 – 4 have been leached.
The leaching period was 180 minutes.
No significant effect of particle size
on the yield of zinc was found, with
the exception of the finest fractions
(d < 0.125 mm), where the leaching
reached a higher yield compared to
the other fractions. Recoveries of zinc
above 90% were reached in individual
fractions [10].
Conclusion
Zinc ash generated in hot batch galvanizing
due to the high zinc content
(70 - 96% Zn) is a valuable secondary
raw material. It can be processed by
hydrometallurgical and also pyrometallurgical
methods. The work was
focused on the hydrometallurgical
processing. We have focused especially
on the leaching in acid with the
aim to leach zinc. Based on the results
of the experiments it was determined
that the most appropriate concentration
of the leaching solution is 10%
hydrochloric acid.
Using a higher concentration is not
important from the practical standpoint.
The monitoring of the time dependence
of the yield of zinc showed
that the maximum yield is achieved
after 20-30 minutes. When assessing
the impact of the zinc ash particle
size on the zinc yield no significant
effect was observed in the range of
these fractions. On the basis of the
results, as well as the observation
with the eye, a higher yield was detected
in the finest grain size fraction
with d < 0.125 mm than in other fractions.
In that fraction almost all zinc
is leached. The extracted extract with
the high zinc content is suitable for
further processing in order to obtain
zinc. A suitable method is the electrolytic
extraction after taking steps
of the refinery and zinc carbonate
precipitation.
Acknowledgment
This work was supported by Slovak
Grant Agency for Science VEGA
1/0134/09.
Fig. 4: The highest yield of Zn in 5, 10, 15 %
HCl during leaching time of 60 min with grain
of ash No. 3, at ambient temperature
References
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(1) Technical University of Knosice,
Fakulty of Metallurgy, Department
of Non-Ferrous Metals and
Waste Treatment, Letná 9, 042 00
Košice, Slovensko
12/2010 | 64. Jahrgang | METALL