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The Effects of Microwave-Assisted Leaching on the Treatment of Electric Arc Furnace Dusts (EAFD)

Laubertova M., Havlik T., Parilak L., Derin B., Trpcevska J.

Archives of Metallurgy and Materials

2020

Vol. 65, iss. 1

321--328

In this study, laboratory-scale experiments were carried out to investigate the effects of microwave-assisted alkaline leaching on the treatment of electric arc furnace dusts to recover zinc and lead. Microwave treatment is a new innovative technology in waste treatment and now is an attractive advanced inter-disciplinary field and also environmental friendly. The highest zinc extraction, 50.3% in 60 minutes using 5 M NaOH at 750 W and L:S ratio 20, and lead extraction up to 92.84% was achieved in these same conditions but in 30 minutes. Compared with conventional leaching, the top extraction rate using MW-assisted leaching was higher by 16% (Zn) and 26% (Pb). Zinc presents in the flue dust in the form of franklinite (ZnFe2 O4 ), its leaching in sodium hydroxide does not occur under the examined conditions, because it is enclosed in a matrix of iron.

Determination of ZnO Amount in Electric Arc Furnace Dust and Temperature Dependence of Leaching in Ammonium Carbonate by Using of X-Ray Diffraction

Havlik T., Maruskinova G., Miskufova A.

Archives of Metallurgy and Materials

2018

Vol. 63, iss. 2

653--658

Zinc is present in electric arc furnace dust (EAFD) mainly in two basic minerals, namely as franklinite ZnFe2O4 and/or zincite ZnO. While zincite is relatively reactive and easily treatable, franklinite is considerably refractory, which causes problems during EAFD processing. In this work EAFD containing 18.53% Zn was leached in water solution of ammonium carbonate. This leaching solution selectively leaches zincite, while franklinite is refractory and stable against leaching in this case. The temperature dependence of zinc leaching from EAFD was studied and the activation energy EA was determined by two methods: 1.) classically based on zinc chemical analyses from the leaching solution and 2.) by using of X-Ray diffraction qualitative phase analyses of leaching residues. The determined values of activation energies 37.41 and 38.55 kJmol-1 match perfectly, which show the excellent possibility of using X-Ray diffraction toward the study of leaching kinetics at properly chosen experimental conditions. The important result is the determination of the amount zincite and franklinite in EAFD, which is not possible by using of classical chemical methods.

Oxidative pressurized acid leaching of waste printed circuit boards

Lundstrom M., Seisko S., Jascisak J., Orac D., Aromaa J., Havlik T., Forsen O.

Physicochemical Problems of Mineral Processing

2017

Vol. 53, iss. 2

781--792

The amount of waste printed circuit board (WPCB) increases continuously. There is an economic and environmental need to recover valuable metals from WPCBs. In this study, the applicability of oxidative pressurized acid leaching of WPCBs rich in copper and tin was investigated. The effect of leaching parameters such as temperature, partial oxygen pressure and chloride concentration on metal dissolution from WPCBs was studied in sulfuric acid media. It was shown that non-metallic elements present in WPCBs initiated gas formation, namely CO2 and CO, during oxidized pressure acid leach. Decomposition of plastic components already started at 90 °C with 1.5 MPa oxygen overpressure in the presence of 1 g/dm3 chlorides. Gas formation was shown to have a negative impact on the process since copper extraction was reduced to 27% compared to 80-90% extraction achieved from anode slimes used as a reference material. It was suggested that gas formation related to plastic components could have a severe impact on metal yields. The highest dissolution of tin equal to 36% was achieved at room temperature. It was found that higher temperature promoted tin hydrolysis.