HOU Long-chao¹, WANG Zhe-hao¹, WANG Ling^1,2*, ZHOU Dong-xiao²

(1. College of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, Chengdu 610059, China;
2. College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China)

Abstract: In order to provide a scientific basis for the evaluation and utilization of coal gangue used for the calcined kaolin in the northern Shanxi, the applied mineralogical characteristics of the coal gangue have been studied in this paper by using modern analytical and testing techniques such as XRD, XRF, SEM, and whiteness meter. The results show that according to the China national standard of the calcined kaolin for papermaking and coatings, coal gangue samples in the northern Shanxi can be mainly classified into three types of raw materials including the qualified raw material, basically qualified raw material, and unqualified raw material. Compared with the qualified and basically qualified raw materials, the unqualified raw materials have relative obviously different contents of SiO2, Al2O3, Fe2O3, alkali metals, and alkaline earth metals. The qualified and basically qualified raw materials are mainly composed of kaolinite (85%－94%). However, the unqualified coal gangue is composed of kaolinite (30%－60%) + quartz (23%－38%) + illite (14%－26%), with a small amount of impurity minerals such as pyrite and dolomite. Impurity minerals such as quartz and iron-containing minerals mainly resulted in the unqualification of calcined products in terms of the chemical composition and whiteness. In the qualified raw materials, kaolinite which has relatively good crystallinity mainly occurred in forms of micro-sized irregular, book-like, and curved sheets which have smooth surfaces and sizes mainly ranging from 0.05 μm to 51.22 μm with average size of 2.80 μm and the size/ thickness ratio of 41.24.

Keywords: Coal gangue; calcined kaolin; kaolinite; quartz; mineral materials

ACTA MINERALOGICA SINICA Vol. 40, No.2, 2020, page 149-154