Study on Extraction Valuable Metal Elements by Co-Roasting Coal Gangue with Coal Gasification Coarse Slag

Jincheng Zhao; Tao Yu; Huan Zhang; Yu Zhang; Lanting Ma; Jinling Li; Chengtun Qu; Te Wang

doi:10.3390/molecules29010130

Study on Extraction Valuable Metal Elements by Co-Roasting Coal Gangue with Coal Gasification Coarse Slag

Molecules. 2023 Dec 25;29(1):130. doi: 10.3390/molecules29010130.

Authors

Jincheng Zhao^{1

2

3}, Tao Yu^{1

2

3}, Huan Zhang¹, Yu Zhang¹, Lanting Ma^{1

3}, Jinling Li^{2

3}, Chengtun Qu^{1

2}, Te Wang^{2

3}

Affiliations

¹ Yan'an Key Laboratory of Low Carbon Synergistic Control Technology and Reservoir Protection for Oil and Gas Field Environmental Pollution, Shaanxi Fuquan Environmental Protection Technology Co., Ltd., Yan'an 727500, China.
² State Key Laboratory of Petroleum Pollution Control, College of Chemistry and Chemical Engineering, Xi'an Shiyou University, Xi'an 710065, China.
³ Shaanxi Oil and Gas Pollution Control and Reservoir Protection Key Laboratory, College of Chemistry and Chemical Engineering, Xi'an Shiyou University, Xi'an 710065, China.

Abstract

Coal gangue (CG) and coal gasification coarse slag (CGCS) possess both hazardous and resourceful attributes. The present study employed co-roasting followed by H₂SO₄ leaching to extract Al and Fe from CG and CGCS. The activation behavior and phase transformation mechanism during the co-roasting process were investigated through TG, XRD, FTIR, and XPS characterization analysis as well as Gibbs free energy calculation. The results demonstrate that the leaching rate of total iron (TFe) reached 79.93%, and Al³⁺ achieved 43.78% under the optimized experimental conditions (co-roasting process: CG/CGCS mass ratio of 8/2, 600 °C, 1 h; H₂SO₄ leaching process: 30 wt% H₂SO₄, 90 °C, 5 h, liquid to solid ratio of 5:1 mL/g). Co-roasting induced the conversion of inert kaolinite to active metakaolinite, subsequently leading to the formation of sillimanite (Al₂SiO₅) and hercynite (FeAl₂O₄). The iron phases underwent a selective transformation in the following sequence: hematite (Fe₂O₃) → magnetite (Fe₃O₄) → wustite (FeO) → ferrosilite (FeSiO₃), hercynite (FeAl₂O₄), and fayalite (Fe₂SiO₄). Furthermore, we found that acid solution and leached residue both have broad application prospects. This study highlights the significant potential of co-roasting CG and CGCS for high-value utilization.

Keywords: Al; Fe extraction; H2SO4 leaching; co-roasting; phase transformation.

Grants and funding

The work was supported financially by the Shaanxi Provincial Department and Municipal Linkage Key Project: Key Technology Development and Engineering Demonstration of Coal-Based Waste Co-utilization in Extremely Thin Coal Seam (No. 2022GD-TSLD-69), the Special Program for Serving Localities of Shaanxi Provincial Department of Education: Research on Reuse Technology of Return Fluid from Oil and Gas Field Measures in North Shaanxi Region(No. 22JC054), the open subject of State Key Laboratory of Petroleum Pollution Control (PPC2019001), and the Xi’an Shiyou University Postgraduate Innovation and Practical Ability Training Project (No. YCS23113051).