Enhancement of coal gangue performance by surface micro-crystalline glaze derived from mineral powder

Fan Yang; Junfan Lv; Yangfan Zheng; Jiayan Cui; Yuandong Huang; Xinde Cao; Hongzhi Liu; Ling Zhao

doi:10.1016/j.scitotenv.2022.159986

Enhancement of coal gangue performance by surface micro-crystalline glaze derived from mineral powder

Sci Total Environ. 2023 Feb 1;858(Pt 2):159986. doi: 10.1016/j.scitotenv.2022.159986. Epub 2022 Nov 8.

Authors

Fan Yang¹, Junfan Lv¹, Yangfan Zheng¹, Jiayan Cui¹, Yuandong Huang¹, Xinde Cao², Hongzhi Liu³, Ling Zhao⁴

Affiliations

¹ School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093, China.
² School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
³ Environmental System Research Laboratory, Faculty of Engineering, Hokkaido University, N13-W8, Sapporo 060-8628, Japan.
⁴ School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China. Electronic address: wszhaoling@sjtu.edu.cn.

PMID: 36356758
DOI: 10.1016/j.scitotenv.2022.159986

Abstract

Coal gangue is a waste derived from coal mining, and its unreasonable disposal usually causes serious land occupation and environmental pollution. Using coal gangue as a substitute for natural aggregate is an effective recycling approach, however, the high water absorption and high crushing rate of coal gangue seriously weaken its performance. This study proposed a novel strategy to decrease the water absorption and crushing rate of coal gangue by co-calcining with mineral powders, including K-feldspar, wollastonite, blast furnace slag and fly ash, meanwhile clarified the improvement mechanisms. Results showed that after calcining with mineral powders, the crushing rate of coal gangue decreased from 16.8 % to 16.1-13.2 %, and water absorption decreased from 5.29 % to 2.74-3.90 %, among which the coal gangue treated by K-feldspar and blast furnace slag had the lowest water absorption (2.74 %), reducing by 48.2 % compared to raw coal gangue. Underlying mechanisms were that during calcination, mineral powders generated micro-crystalline glaze on gangue surface, which improved the pore size distribution of coal gangue and strengthened its hardness. Specifically, as for pores with 1-1000 nm diameter, the pore volume percentage decreased from 88.5 % to 43.2-71.3 %. Vickers hardness of coal gangue increased from 0.29 GPa to 6.37-6.79 GPa, and the fracture toughness increased significantly to 41.9-67.6 MPa m^1/2. Under K-feldspar and blast furnace slag treatment, the approximate thickness of micro-crystalline glaze was about 32 μm. The main component of micro-crystalline glaze was silicate lattice derived from SiO₂ and Al₂O₃, and abundant Fe₂O₃ and Fe₃O₄ crystalline were sealed in the glaze. This study provides an innovative approach to strengthen the performance of coal gangue, which is important to expand the resource utilization of coal gangue and control the environmental pollution.

Keywords: Blast furnace slag; Crushing rate; Pore size distribution; Water absorption.

MeSH terms

Coal* / analysis
Minerals
Powders
Silicon Dioxide*
Water / chemistry

Substances

Coal
feldspar
Powders
Silicon Dioxide
Minerals
Water