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Metals 2017, 7(8), 321; doi:10.3390/met7080321

Crystallization and Beneficiation of Magnetite for Iron Recycling from Nickel Slags by Oxidation-Magnetic Separation

1,2
,
1,2,* , 1,2
,
1,2
and
1,2
1
State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China
2
School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, China
*
Author to whom correspondence should be addressed.
Received: 22 June 2017 / Revised: 11 August 2017 / Accepted: 18 August 2017 / Published: 22 August 2017
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Abstract

The iron resources in nickel slag were recycled by oxidation and magnetic separation. The effects of holding time, temperature, air flow rate and basicity on the crystallization of magnetite were investigated systematically. Moreover, the influence of particle size and magnetic flux density on the recovery and grade of iron during the magnetic separation was also explored. Results showed that the magnetite particles were significantly influenced by holding time, and the average diameter size reached about 20 μm after holding for 20 min at 1623 K. The holding temperature obviously affected the microstructure of magnetite phases: with the increase in holding temperature, the shapes of the magnetite particles changed from polyhedral form to skeletal particles. As the air flow rate was increased to 170 mL/min, the magnetite developed into tiny spherical particles due to the strong stirring. It was also found that the crystallization of magnetite was slightly effected by basicity. The iron recovery reduced with the decrease of particle size, while the iron grade first increased to a maximal value of 38 μm, and then decreased. As the magnetic flux density increased, the iron recovery initially increased rapidly, reaching a maximal value at 120 mT, while the iron grade remained almost constant. The final iron recovery and grade were 75.99% and 54.08%, respectively, via multi-step magnetic separation instead of single magnetic separation. Iron in concentrate mainly exists in the form of magnetite and magnesium ferrite, and contents of siderophile elements (Ni, Co) in final concentrate were also higher than that of raw slags. View Full-Text
Keywords: nickel slag; oxidation; crystallization; beneficiation; magnetite; magnetic separation nickel slag; oxidation; crystallization; beneficiation; magnetite; magnetic separation
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Ma, Y.; Du, X.; Shen, Y.; Li, G.; Li, M. Crystallization and Beneficiation of Magnetite for Iron Recycling from Nickel Slags by Oxidation-Magnetic Separation. Metals 2017, 7, 321.

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