Journal of Hazardous Materials 192 (2011) 1100–1107 Contents lists available at ScienceDirect Journal of Hazardous Materials j our na l ho me p age: www.elsevier.com/locate/jhazmat Acidic leaching both of zinc and iron from basic oxygen furnace sludge Zuzana Hoang Trung, Frantisek Kukurugya, Zita Takacova, Dusan Orac, Martina Laubertova, Andrea Miskufova, Tomas Havlik ∗ Technical University of Kosice, Faculty of Metallurgy, Department of Non-ferrous Metals and Waste Treatment, Letna 9, 042 00 Kosice, Slovak Republic a r t i c l e i n f o Article history: Received 2 February 2011 Received in revised form 6 June 2011 Accepted 7 June 2011 Available online 12 June 2011 Keywords: Basic oxygen furnace dust and sludge Hydrometallurgy Leaching Zinc Iron Sulphuric acid a b s t r a c t During the steel production in the basic oxygen furnace (BOF), approximately 7–15 kg of dust per tonne of produced steel is generated. This dust contains approximately 1.4–3.2% Zn and 54–70% Fe. Regarding the zinc content, the BOF dust is considered to be highly problematic, and therefore new technological processes for recycling dusts and sludge from metallurgical production are still searched for. In this study the hydrometallurgical processing of BOF sludge in the sulphuric acid solutions under atmospheric pressure and temperatures up to 100 ◦ C is investigated on laboratory scale. The influence of sulphuric acid concentration, temperature, time and liquid to solid ratio (L:S) on the leaching process was studied. The main aim of this study was to determine optimal conditions when the maximum amount of zinc passes into the solution whilst iron remains in a solid residue. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The generation of steelmaking dusts is an integral part of melting in steelmaking plants. Steelmaking dusts are waste oxide materi- als, whose major components are iron oxides. These steelmaking dusts are obtained either in the form of dust, from dry dust sepa- ration, or in the form of sludge from wet dust separation. Due to the zinc content in the steelmaking dusts and sludge they cannot be recycled, hence they are deposited in landfills. Large grain size scattering as well as varied chemical and min- eralogical composition are typical features of steelmaking dusts. Table 1 shows the percentage of zinc and iron in BOF dust and sludge according to various authors. Both BOF dust and sludge are categorized as hazardous wastes [14]. Several methods for the processing of steelmaking dusts have been already designed; however, there is still not enough infor- mation about how to process BOF dust. This is probably caused by relatively low content of zinc compared with electric arc furnace dust. The steelmaking dust can be processed by pyrometallurgical methods, hydrometallurgical methods or by combination of both [15]. Each of these methods has its advantages as well as disad- vantages. The advantage of hydrometallurgical processes is their higher flexibility in plants. Hydrometallurgical processes are also more economical because of lower capital and operating costs. In ∗ Corresponding author. Tel.: +421 55 602 24 28; fax: +421 55 602 24 28. E-mail address: tomas.havlik@tuke.sk (T. Havlik). addition, hydrometallurgy offers the possibility of getting valuable metals from the dust or sludge. There are also environmental ben- efits in comparison with pyrometallurgy because of no problems associated with off-gases, dust nuisance and noise. However, hydrometallurgy does not offer a solution to the steel- making waste processing by only one versatile way. The leaching methods are individual and depend not only on the type of the pro- cessed waste but on the physical, physico-chemical, chemical and mineralogical properties as well. Research in the field of hydromet- allurgical processing is becoming more and more intensive. It is mainly because of the need to process complex raw materials, environmental aspects and also due to the legislative pressure for environmental protection. This work focuses on a study of the influence of the tempera- ture and sulphuric acid concentration on zinc extraction into the solution as well as the determination of the optimal conditions under which the maximum amount of zinc passes into the solution and iron remains in solid residue. The aim is to design a recycling method for BOF sludge. 2. Experimental 2.1. Material The sample of BOF sludge was dried and homogenized before the leaching experiments. The chemical analysis was performed by atomic absorption spectrometry (AAS). The chemical composition of dust from converter gas treatment is shown in Table 2. 0304-3894/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2011.06.016