https://orcid.org/0000-0002-5932-6932
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ABSTRACT
Coal gangue (CG) is one of the main solid wastes emitted by coal mining. It causes severe damage to the environment. CG contains high levels of valuable elements (Al, Si) and has the potential for utilization and clean disposal. Here, an environment-friendly process for separating valuable components from CG was proposed: the closed-loop system of activation-leach-separation. The results show that the decarbonization rate was close to 100% under the optimum conditions of CG particle size of 0.075 mm to 0.15 mm and activated at 800°C for 120 min. Subsequently, it was transformed into a mixed-acid system with a hydrochloric acid (HCl) concentration of 4.5 mol/L, hydrofluoric acid (HF) volume fraction of 15%, and the liquid-solid ratio of 10:1, which achieved excellent separation efficiency. The residual rate of Al in the solution was only 0.7%, and the extraction rate of Si can reach 71.6%. Further, industrial-grade AlF3 products were also recovered. By adding saturated KCl solution and reacting at 33°C for 15 min, Si was further recovered in K2SiF6, and the yield was 85.83%. Particularly, the leaching solution maintained good extraction efficiency in the subsequent three cycles, the yield of K2SiF6 was 88.29%, confirming the feasibility of the closed-loop system. This treatment embodied the environmental-friendly properties of low acid consumption and low effluent discharge, providing a feasible method for clean treatment and resource utilization of CG.
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No potential conflict of interest was reported by the author(s).
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Supplemental data for this article can be accessed online at https://doi.org/10.1080/15567036.2024.2334921
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Notes on contributors
Fanghong Xu
Fanghong Xu, Master, studying in the School of Metallurgy and Environment, Central South University. His main research direction is the recycling and resource utilization of solid hazardous waste.
Jin Xiao
Dr. Jin Xiao, postdoctoral, second-level professor, doctoral supervisor, Deputy director of the National Engineering Research Center of Low-carbon Nonferrous Metallurgy, member of the Light Metals Committee of the Chinese Nonferrous Metals Society, Director secretary of the Carbon Professional Committee, member of the American TMS Society. His research interests are light metal smelting, carbon materials and powder materials. He participated in the compilation and publication of 1 academic monograph, applied for and authorized more than 20 patents, and published more than 60 papers in high-level academic journals such as Carbon, Hydrometallurgy, Energy fuel, etc. He has presided over more than 20 National Natural Science Foundation, National Science and Technology Support Plan and school-enterprise cooperative research projects, and won first prizes of provincial and ministerial science and technology progress.
Shengchao Ye
Shengchao Ye, Master, graduated from School of Metallurgy and Environment, Central South University. His main research interest is the high-value application of solid waste.
Wei Liu
Wei Liu, Professor, Director of Engineering Technology Research Center for Aluminum electrolytic Carbon Materials in Guizhou Province. His main research direction is the recycling of aluminum electrolytic carbon materials and industrial solid waste. He has published 2 monographs, 65 papers, 2 authorized patents, won second prize of China Nonferrous Metal Industry Science and Technology Award and First Prize of Gansu Province Metallurgical Nonferrous Industry Science and Technology Progress Award.
Minge Yang
Minge Yang, Ph.D., Postdoctoral Fellow. He graduated from the School of Metallurgy and Environment, Central South University. His main research interests are modern hydrometallurgy technology and extraction and separation of valuable metal elements.
Zhen Yao
Zhen Yao, Associate professor, Deputy Director of the Engineering Technology Research Center for Aluminum electrolytic Carbon Materials in Guizhou Province. His main research direction is the preparation of high performance carbon-based electrode materials and the recycling of industrial solid waste. He has published 37 papers and authorized 1 invention patent.
Qifan Zhong
Dr. Qifan Zhong, Professor, Central South University, was selected into the Young Elite Scientists Sponsorship Program of the China Association for Science and Technology, the Hunan Provincial Science Fund for Excellent Young Scholars, the first Xiaomi Young Scholars, and the Hunan Provincial Hundred Excellent Doctoral Thesis etc, and was approved for 4 provincial Science and Technology Progress Awards. The main research area is new theories and technologies for comprehensive carbon reduction. Innovatively developed a closed-loop material genetic engineering research technology system of “experiment-modeling-calculation”, and proposed new underlying theoretical research technologies in the theoretical research on the complex microstructure of metallurgical electrode raw materials. He led the industrialization of two technologies and solved the core technology of integrated circuits. He has published 46 papers as the first or corresponding author in high-level international journals such as EnSM, CEJ, JHM, and Carbon, and has 33 authorized patents.