Iron recovery from the coarse fraction of basic oxygen furnace sludge. Part I: optimization of acid leaching conditions
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RESEARCH ARTICLE
Iron recovery from the coarse fraction of basic oxygen furnace sludge. Part I: optimization of acid leaching conditions Luisa Cardoso Maia 1
&
Grazielle Rocha dos Santos 1 & Leandro VinÃcius Alves Gurgel 2 & Cornélio de Freitas Carvalho 2
Received: 18 January 2020 / Accepted: 26 June 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this study, a new reuse process of the coarse fraction of basic oxygen furnace (BOF) sludge based on iron recovery by the ferrous sulfate production was proposed. This study was based on three main steps: (i) characterization of the steel waste, (ii) evaluation and optimization of the recycling process, and (iii) characterization of ferrous sulfate produced. Acid leaching was used to solubilize the iron for obtaining ferrous sulfate heptahydrate. The ferrous sulfate crystallization was performed by adding anhydrous ethanol (EtOH). A multivariate optimization for iron leaching and ferrous sulfate precipitation in the same solution was employed. This optimization consisted of screening steps using a full factorial design followed by optimization. The coarse fraction of BOF sludge was predominantly composed of iron in metallic form (82.5%, dry weight). The sulfuric acid concentration and leaching time had significant effects on Fe(II) solubilization. The desirability function predicted the following optimized conditions: 20% (v/v) sulfuric acid solution, 200 min of leaching time, 7.00 g of waste, and 110 mL of anhydrous EtOH, producing 19.60 g of ferrous sulfate heptahydrate (yield of 70.8%). The characterization of ferrous sulfate was performed by X-ray diffraction, scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The characterization of the ferrous sulfate produced evidenced the effectiveness of the optimized process condition. Keywords Steel waste . Basic oxygen furnace sludge . Acid leaching . Recycling . Ferrous sulfate . Multivariate optimization
Introduction The significant increase in the industrial waste generation led to an adjustment in the perception of industry concerning its production pattern (Freeman 1998). Thus, the cleaner Responsible editor: Weiming Zhang Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-020-09910-x) contains supplementary material, which is available to authorized users. * Luisa Cardoso Maia [email protected]; [email protected] 1
Graduate Program in Environmental Engineering, Department of Environmental Engineering, School of Mines, Federal University of Ouro Preto, Campus Morro do Cruzeiro, Bauxita, Ouro Preto, Minas Gerais 35400-000, Brazil
2
Department of Chemistry, Institute of Biological and Exact Sciences (ICEB), Federal University of Ouro Preto, Campus Morro do Cruzeiro, Bauxita, Ouro Preto, Minas Gerais 35400-000, Brazil
production approach emerged in 1989, which was proposed by the United Nations Environment Programme and adop
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