Investigations on the microwave absorption properties and thermal behavior of vanadium slag: Improvement in microwave oxidation roasting for recycling vanadium and chromium

Kangqiang Li; Qi Jiang; Lei Gao; Jin Chen; Jinhui Peng; Sivasankar Koppala; Mamdouh Omran; Guo Chen

doi:10.1016/j.jhazmat.2020.122698

Investigations on the microwave absorption properties and thermal behavior of vanadium slag: Improvement in microwave oxidation roasting for recycling vanadium and chromium

J Hazard Mater. 2020 Aug 5:395:122698. doi: 10.1016/j.jhazmat.2020.122698. Epub 2020 Apr 14.

Authors

Kangqiang Li¹, Qi Jiang¹, Lei Gao², Jin Chen³, Jinhui Peng⁴, Sivasankar Koppala⁵, Mamdouh Omran⁶, Guo Chen⁷

Affiliations

¹ Key Laboratory of Unconventional Metallurgy, Ministry of Education, Kunming University of Science and Technology, Kunming 650093, PR China.
² Key Laboratory of Green-Chemistry Materials in University of Yunnan Province, Kunming Key Laboratory of Energy Materials Chemistry, Yunnan Minzu University, Kunming 650500, PR China.
³ Key Laboratory of Unconventional Metallurgy, Ministry of Education, Kunming University of Science and Technology, Kunming 650093, PR China. Electronic address: jinchen@kust.edu.cn.
⁴ Key Laboratory of Unconventional Metallurgy, Ministry of Education, Kunming University of Science and Technology, Kunming 650093, PR China; Key Laboratory of Green-Chemistry Materials in University of Yunnan Province, Kunming Key Laboratory of Energy Materials Chemistry, Yunnan Minzu University, Kunming 650500, PR China.
⁵ Panjin Institute of Industrial Technology, Dalian University of Technology, Panjin 124221, Liaoning, PR China.
⁶ Process Metallurgy Research Group, Faculty of Technology, University of Oulu, Finland.
⁷ Key Laboratory of Unconventional Metallurgy, Ministry of Education, Kunming University of Science and Technology, Kunming 650093, PR China; Key Laboratory of Green-Chemistry Materials in University of Yunnan Province, Kunming Key Laboratory of Energy Materials Chemistry, Yunnan Minzu University, Kunming 650500, PR China; Panjin Institute of Industrial Technology, Dalian University of Technology, Panjin 124221, Liaoning, PR China. Electronic address: guochen@kust.edu.cn.

PMID: 32334279
DOI: 10.1016/j.jhazmat.2020.122698

Abstract

Vanadium slag contains high contents of vanadium and chromium with complex and dense structures, hence microwave heating instead of conventional methods is expected to destroy the dense structure and further to improve the extraction rate of vanadium and chromium, and exploring its dielectric properties is the prerequisite work. Microwave absorption properties and thermal behavior of vanadium slag were investigated. Results indicated that vanadium slag endowed excellent microwave absorption properties, with minimum ε_r' value of 34.447 (F/M). Dielectric properties of vanadium slag varied with temperature, which changing trend was matched to the three stages of microwave heating characteristics identified by heating rates. Meanwhile, the changing process of dielectric properties also corresponded to the three processes of thermogravimetric characteristics: dehydration stage (30 °C-280 °C), oxidation decomposition of olivine phase and normal spinel phase (280 °C-650 °C), and oxidation decomposition of vanadium chromium spinel (650 °C-950 °C). Moreover, the maximum dielectric constant and highest microwave heating rate of vanadium slag both appeared at the temperature regime of 500 °C-550 °C, which was also the main temperature regime for oxidation decomposition of olivine phase and normal spinel phase in vanadium slag, demonstrating the appropriate process temperature for microwave heating technology to recycle vanadium slag.

Keywords: Chromium; Microwave absorption properties; Microwave oxidation roasting; Thermal behavior; Vanadium slag.