Koleszár, Péter

Kozák, Miklós

Papp, István

University of Debrecen Electronic Archive

ACTA GGM DEBRECINA Geology, Geomorphology, Physical Geography Series DEBRECEN Vol. 4-5, 7–11             2010 
 7
Chemical composition and zinc leaching test of dust from electric arc furnace emissions from 
the Steelwork of Ózd, Hungary 
Az Ózdi Acélművek füstgázából leválasztott por kémiai összetételének és oldható cinktartalmának vizsgálata 
 
István Papp1 — Péter Koleszár1 — Miklós Kozák1 
 
University of Debrecen, Department of Mineralogy and Geology, 4032 Debrecen, Egyetem tér 1., Hungary; e-mail: papis@citromail.hu 
 
Abstract – The recycling of metallurgical by-products is vital for both economical or environmental reasons. Electric arc furnace dusts are 
considered as secondary raw materials for zinc production. In this paper we investigated the chemical composition of the EAF dusts of 
the Steelwork of Ózd, Hungary. The total zinc content of the EAF dust is 24-25 (m/m)%, and 16-17 (m/m)% is leachable with an 
ammonium carbonate solution. The EAF dust of Ózd Steelwork should be considered as a potential raw material for hydrometallurgical 
Zn production. 
 
Összefoglalás – A fémipari hulladékok újrahasznosítása környezetvédelmi és gazdaságossági szempontból is lényeges. Az acélgyártás 
során a füstgázokból leválasztott porok másodlagos nyersanyagokként elsősorban a cinktermelésben jöhetnek szóba. Jelen cikkünkben az 
Ózdi Acélművek ívkemencéjének füstgázaiból leválasztott por kémiai összetételét vizsgáltuk. A leválasztott por cinktartalma átlagosan 24-
25 (m/m)%, melyből 16-17 (m/m)%-nyi mennyiség kioldható ammónium-karbonáttal. Véleményünk szerint a füstgázból leválasztott por 
hidrometallurgiai módszerekkel újrahasznosítható másodlagos nyersanyag. 
 
Keywords – steal production, furnace dust, secondary raw material, Ózd 
Tárgyszavak – acélgyártás, füstgáz por, másodlagos nyersanyag, Ózd 
 
 
Introduction 
 
Electric arc furnace dust (EAF dust) is a by-product of 
the EAF-type steel-making technology. Since EAF dusts 
are characterized by high concentrations of leachable heavy 
metals (e.g. Zn, Pb, Cu, Cd, As), they are classified as 
hazardous wastes. Due to the large quantity of EAF dust 
(10-20kg per ton of steel) and its toxic nature, the safe 
disposal of the dust is a major challenge of the secondary 
steel industry. According to modern environmental 
protection and technological principles, the cost-effective 
recycling of by-products is desirable as well. To achieve 
these objectives, one must know the chemical and 
mineralogical composition of EAF dusts, and the variability 
of these properties. 
 
The chemical composition of EAF dusts 
The Ózd Steelwork Ltd uses large quantities of scrap 
steel as a source material. The scrap metal may contain a 
significant amount of volatile elements (e.g. Cd, Zn, Pb and 
Cl), which are enriched in the fumes and fly dusts. 
 
The most important methods of EAF dust treatment are 
the following: 
(a) Disposal as landfill. This is the least effective method, 
since the dust is not recycled, and the leachable toxic 
metals may pose an environmental threat (NYIRENDA 
& LUGTMEIJER 1993; PICHTEL & BRADWAY 2008). 
(b) Glassification by thermal treatment to prevent the 
leaching of toxic metals (CHENG 2003). 
(c) Treatment with alkaline solid materials, such as lime, 
portland cement or blast furnace slags (the latter is a 
by-product of iron smelting). The pH of the alkaline 
media should be adjusted to minimize the solubility of 
heavy metals (LAFOREST & DUCHESNE 2007; 
SALIHOGKU & PINARLI 2008). EAF dusts are used by 
the construction industry as a component of portland 
cements. The high chloride and sulphate content of 
the dust limits the dust:cement ratio, since these 
anions have an undesirable effect on the characteristics 
of the cement. 
(d) Recycling by pyrometallurgical methods (DONALD & 
PICKLES 1996). The major objective of this method is 
the recovery of zinc. From an economical point of 
view, this method requires high zinc concentration of 
the EAF dust. 
(e) Recycling by hydrometallurgical methods (NYIRENDA 
& LUGTMEIJER 1993; DUTRA et al. 2006; RUIZ et al. 
2007). The objective of these treatments is the 
recovery of heavy metals, especially zinc. The two 
major zinc-bearing phases in EAF dusts are franklinite 
(ZnFe2O4) and zincite (ZnO) (DUTRA et al. 2006; 
LECLERC et al. 2003). Franklinite is a resistant mineral 
with spinel-type crystal structure and is soluble only in 
concentrated strong acids, while zincite is soluble 
under mild conditions, e.g. in dilute acidic or alkaline 
solutions or in the presence of complexing agents. For 
the same reason, franklinite is considered non-toxic. In 
several hydrometallurgical processes dilute acids are 
used as solvents to recover zinc (HLAVÍK et al. 2006; 
ASADI ZEYDABADI et al. 1997). A disadvantage of 
using acids is that other metallic elements dissolve as 
well, and their separation may significantly increase the 
cost of such methods. A more practical method is the 
leaching of Zn by using alkaline media, such as NaOH 
or ammonium carbonate solutions. A major advantage 
of alkaline leaching is that the iron oxides remain in 
the solid phase, therefore some degree of separation is 
achieved. Besides zinc, ammonium carbonate leaching 
will dissolve the cadmium, copper and lead 
compounds as well, and the remaining solid (mostly 
composed by iron oxides and franklinite) is non-toxic 
(NYIRENDA & LUGTMEIJER 1993; RUIZ et al. 1997). 
The latter three metals may be separated by reduction 
with metallic Zn. Thus, high-grade ZnO can be 
prepared, and the toxic heavy metals are concentrated 
in metallic form. 
 
ACTA GGM DEBRECINA Geology, Geomorphology, Physical Geography Series Vol. 4-5                2010 
 
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The technology of EAF dust separation in the Steelwork of Ózd 
The fumes of the electric arc furnace are conducted 
into a post-combustion unit, where the larger particles (few 
millimetres in diameter) are removed. Then the fume is 
cooled below 120°C through a heat exchanger, and the fine 
dust is removed by bag filters. The EAF dust is deposited 
as specific landfill near the village of Sajókaza. 
 
Aims 
 
In this paper we investigated the recycling possibilities 
of the EAF dust of the Steelwork of Ózd. The 
investigation concerned the following: 
 
(i) determination of the chemical composition of the 
EAF dust;  
(ii) investigation of the compositional changes during a 
charge-time. Since zinc is more volatile than iron, one 
might expect that zinc is enriched in the fumes during 
the early stages of the steelmaking process. If so, the 
early-stage EAF dusts may be collected separately in 
order to obtain an economically more valuable raw 
material for zinc production. 
(iii) Determination of the ammonium-carbonate-soluble 
fraction of the total Zn content of the EAF dusts. 
  
Materials and methods 
 
Sampling 
The sampling of the EAF dust was carried out at 6th 
February, 2008. Samples were taken from the bag filter of 
the steelwork in 3-minute intervals during a charge. One 
charge of the steelmaking process lasts for cca. 80 minutes, 
thus we took 25 samples. The mass of each sample was 
about 200g. Due to the fine grain size, homogenization and 
grinding was not necessary. 
 
Sample preparation 
To determine the total concentrations of the 
investigated elements (Ca, Cd, Fe, K, Na, Pb, Zn), 0.1mg 
EAF dust samples were measured with a precision of 
0.0001g, and the samples were boiled with 15ml of aqua 
regia. The solutions were evaporated to cca. 1ml, then 
diluted to 50ml in volumetric flasks with deionised water. A 
small amount of black solid residue was observed after the 
acid digestion. We identified this residue as carbon, since it 
was not present in those samples which were heat treated 
at 1000°C prior to aqua regia digestion.  
In order to examine the possibility of re-using the 
EAF dust as a raw material for zinc production, we leached 
the dust samples with ammonium carbonate. 0.2g dust 
samples were leached with 9ml 10 (m/m)% ammonium 
carbonate solution. The pH of the leaching solution was 
adjusted to 10.5 with 25 (m/m)% ammonia solution. The 
leaching time was 2 hours, and the suspensions were 
thoroughly shaked every 30 minutes. The suspensions were 
left to settle for 12 hours. 0.5ml of the clear supernatant 
liquid was taken with a pipette and diluted to 250ml in a 
volumetric flask. The zinc concentrations of these solutions 
were determined. 
 
 
Analysis 
The concentrations of Cd, Fe, K, Pb and Zn were 
measured by using flame atomic absorption spectroscopy. 
Concentrations of Ca, K and Na were determined by flame 
atomic emission method. The calibrating solutions were 
made by using commercial single-element 1000mg/l stock 
solutions. The measurements were carried out on a Zeiss-
Jena AAS-1 spectrometer. The sample solutions were 
diluted when it was necessary. 
 
Results and discussion 
 
Results of aqua regia digestion 
The results of the chemical analyses are shown in Table 
1, and the plots are shown in Figure 1. According to the 
practice of the laboratory of the Steelwork of Ózd, 
concentrations of Ca, K and Na are given as oxides in 
(m/m)%, while the heavy metals are given as elements in 
(m/m)%. Data for Cd is given in mg/kg. 
The pseudo-total concentrations of the observed 
elements did not show significant changes with charge-
time. The concentrations of the observed elements were 
fairly constant with time. The outlying values may be 
associated with the possible inhomogeneities of the 
samples. The relative standard deviations (RSD) of the 
concentrations were between 3 and 12%. The lowest RSD 
value was found in the case of Fe, while the highest was in 
the case of Ca. 
The results suggest that the bulk chemistry of the EAF 
dusts does not change significantly with the charge-time, 
and the dust can not be separated into fractions with 
different chemical compositions. 
 
Results of ammonium carbonate leaching 
The alkaline ammonium carbonate solution dissolved 
15-18 (m/m)% Zn from the EAF dust samples. The 
average leachable Zn content was 16.6 (m/m)%. The total 
Zn varied between 22.5-27 (m/m%), the average was 25.5 
(m/m)%. The average dissolved fraction was 65% of the 
total Zn, which is equal to 16.6% Zn content. The fraction 
of ammonium carbonate soluble zinc slightly decreased 
with charge-time from cca. 70% soluble fraction (18% Zn) 
to 60% soluble (15% Zn).  
On the basis of the total and ammonium carbonate 
soluble zinc concentrations, the amount of major zinc-
bearing minerals (franklinite and zincite) were calculated as 
follows: 
 
Zincite % = (Znsoluble%)*(AZn + AO)/AZn 
 
Franklinite % = (Zntotal%-Znsoluble%)*(AZn + + 2AFe + 
4AO)/AZn 
 
where Znsoluble% is the ammonium carbonate soluble Zn 
content, given as (m/m)%; Zntotal% is the aqua regia soluble 
zinc content, (m/m)%; AZn = 65.37g/mol; AO = 
16.0g/mol; AFe = 55.85g/mol. 
 
The most abundant Zn-bearing mineral phase was 
franklinite (ZnFe2O4) with an average concentration of 
32.7 (m/m)%. The average concentration of zincite (ZnO) 
was 20.7 (m/m)%. However, only 30-40% of the total zinc 
Papp et al.: Chemical composition and leaching test         MINERALOGY, GEOCHEMISTRY 
 
 9
content is present in franklinite, the remaining 60-70 
(m/m)% of the total zinc is in zincite form. 
The fraction of zincite slightly decreased (from 72% to 
64%), while the fraction of franklinite increased (from 28% 
to 36%) with charge-time. This may be due to the 
increasingly oxidative properties of the fume gases, which 
cause the oxidation of Fe(II) minerals to Fe(III) oxides. 
Ferric oxides can react with ZnO and form franklinite. 
 
Summary 
 
Our results suggest that the EAF dusts of the Ózd 
Steelwork contain a high fraction of leachable Zn, thus may 
be economically used as a raw material for 
hydrometallurgical Zn production. The leaching tests might 
be used as useful tool for the mineralogical investigations 
of EAD dusts and other metallurgical by-products.  
 
Acknowledgements 
 
The authors would like to thank for the help of the 
Steelwork of Ózd Ltd., Furol-Analitika Ltd., and the 
accurate careful work of the reviewers.   
 
References 
 
ASADI ZEYDABADI, B., MOWLA, D., SHARIAT, M.H., FATHI 
KALAJAHI, J. (1997): Zinc recovery from blast furnace 
flue dust. Hydrometallurgy, 47, 113–125. 
BRUCKARD, W.J., DAVEYA, K.J., RODOPOULOSA, T., 
WOODCOCKA, J.T., ITALIANO, J. (2005): Water 
leaching and magnetic separation for decreasing the 
chloride level and upgrading the zinc content of EAF 
steelmaking baghouse dusts. Int. J. Miner. Process. 75, 1–
20. 
CHENG, T.W. (2003): Combined glassification of EAF dust 
and incinerator fly ash. Chemosphere, 50, 47–51. 
DONALD, J.R., PICKLES, C.A. (1996): Reduction of electric 
arc furnace dust with solid iron powder, Canadian 
Metallurgical Quarterly, 35(3), 255–267. 
DUTRA, A.J.B, PAIVA, P.R.P., TAVARES, L.M. (2006): 
Alkaline leaching of zinc from electric arc furnace steel 
dust. Minerals Engineering,19, 478–485. 
HAVLÍK, T., VIDOR, E SOUZA, B., BERNARDES, A.M., 
SCHNEIDER, I.A.H., MIŠKUFOVÁ, A. (2006): 
Hydrometalurgické spracovanie úletu zo spracovania 
odpadu uhlíkových ocelí v elektrických oblúkových 
peciach. Acta Metallurgica Slovaca,12(1), 42–53. 
LAFOREST, G., DUCHESNE, J. (2007): Investigation of 
stabilization/solidification for treatment of electric arc 
furnace dust: Dynamic leaching of monolithic 
specimens. Cement and Concrete Research, 37, 1639–1646. 
MARTINS, F.M., DOS REIS NETO, J.M., DA CUNHA, C.J. 
(2008): Mineral phases of weathered and recent electric 
arc furnace dust. Journal of Hazardous Materials, 154, 17–
425. 
NYIRENDA, R.L., LUGTMEIJER, A.D. (1993): Ammonium 
carbonate leaching of carbon steelmaking dust. 
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PICHTEL, J, BRADWAY, D.J. (2008): Conventional crops and 
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RUIZ, O., CLEMENTE, C., ALONSO, M., ALGUACIL, F.J. 
(2007): Recycling of an electric arc furnace flue dust to 
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Materials, 153, 1110–1116. 
 
ACTA GGM DEBRECINA Geology, Geomorphology, Physical Geography Series Vol. 4-5                2010 
 
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time CaO  Na2O K2O  Fe Pb  Cd Zntotal Znsoluble Zincite Franklinite 
min % % % % % mg/kg % % % % 
3 2.59 2.20 2.51 24.8 3.49 728 25.5 17.8 22.1 28.6 
6 2.83 2.36 2.49 25.7 3.49 669 28.0 18.0 22.4 36.9 
9 2.66 2.29 2.50 25.4 3.81 699 25.4 17.5 21.7 29.4 
12 2.39 2.47 2.50 24.7 3.39 763 24.2 16.8 21.0 27.1 
15 2.47 2.29 2.46 25.7 3.17 713 22.5 16.5 20.5 22.4 
18 2.64 2.01 2.66 24.9 3.32 685 25.4 18.4 22.9 26.0 
21 2.41 2.38 2.58 25.2 3.36 667 23.9 16.3 20.3 28.0 
24 2.50 2.45 2.43 25.0 3.39 667 25.5 17.0 21.1 31.4 
27 2.63 2.26 2.46 25.3 3.33 705 25.5 17.0 21.1 31.5 
30 2.56 2.27 2.47 24.4 3.36 692 25.7 18.4 22.9 26.9 
33 2.48 2.37 2.22 25.4 3.47 681 26.5 15.0 18.7 42.2 
36 2.73 2.26 2.49 25.6 3.38 723 24.1 15.0 18.6 33.7 
39 3.06 2.26 2.42 23.9 3.53 863 24.7 15.6 19.5 33.3 
42 2.57 2.21 2.41 24.9 3.34 732 25.7 16.6 20.7 33.5 
45 3.73 2.14 2.48 25.9 3.28 694 24.0 15.9 19.8 29.8 
48 2.67 2.18 2.36 26.6 3.43 650 24.5 16.2 20.1 30.8 
51 2.73 2.61 2.50 25.4 3.48 725 25.4 16.7 20.8 32.2 
54 2.50 2.19 2.60 25.7 3.55 698 27.9 15.5 19.3 46.0 
57 2.97 2.27 2.29 25.5 3.40 702 26.3 16.6 20.7 35.6 
60 2.37 2.04 2.48 26.7 3.62 782 25.2 16.7 20.8 31.4 
63 2.69 2.08 2.49 27.1 3.47 634 25.4 17.9 22.3 27.5 
66 2.20 2.39 2.49 24.9 3.45 698 26.7 16.8 20.9 36.6 
69 2.44 2.10 2.50 24.7 3.57 688 26.8 16.7 20.7 37.3 
72 2.56 2.18 2.30 24.3 3.59 673 25.7 15.3 19.1 38.3 
75 2.30 2.32 2.41 24.2 3.59 705 26.9 16.0 19.9 40.4 
Mean 2.63 2.26 2.46 25.3 3.45 705.32 25.5 16.6 20.7 32.7 
RSD % 11.48 6.13 3.88 3.03 3.81 6.56 4.93 5.81 5.81 16.90 
Table 1. Changes in the concentration of the measured elements and zinc-bearing minerals with time during one steelmaking charge. 
1. Táblázat. A vizsgált elemek koncentrációjának változása, valamint a fő cinkásványok mennyisége a szállóporban az adagidő során. 
 
Papp et al.: Chemical composition and leaching test         MINERALOGY, GEOCHEMISTRY 
 
 11
CaO
0
1
2
3
4
0 20 40 60 80time (min)
(m
/m
) %
 
Pb
0
1
2
3
4
5
0 20 40 60 80time (min)
(m
/m
)%
 
Na2O
0
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2
3
0 20 40 60 80
time (min)
(m
/m
) %
 
 
K2O
0
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2
3
0 20 40 60 80
time (min)
(m
/m
)%
 
 
Fe
0
5
10
15
20
25
30
0 20 40 60 80time (min)
(m
/m
) %
 
Cd
0
200
400
600
800
1000
0 20 40 60 80time (min)
m
g/
kg
 
Zn
0
5
10
15
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0 20 40 60 80time (min)
(m
/m
) %
total Zn
soluble Zn
 
 
 dissolved fraction of total Zn
0
20
40
60
80
0 20 40 60 80
time(min)
di
ss
ol
ve
d 
%
 
 
 
Figure 1: Changes of the concentration of the observed components and the soluble fraction of Zn during a charge-time 
1. ábra: A vizsgált komponensek koncentrációinak és a cink oldható hányadának változása az adagidő során 
 
 


Chemical composition and zinc leaching test of dust from electric arc furnace emissions from the Steelwork of Ózd, Hungary

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Chemical composition and zinc leaching test of dust from electric arc furnace emissions from the Steelwork of Ózd, Hungary

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