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| Analysis of Iron Impurity and Its Occurrence Form in Red Clay of Guangdong Province |
| QIU Bo-xin1, LUO Hong-jie2*, WANG Fen1, ZHU Jian-feng1, LIU Yi-jun3, HAO Yao-rui1 |
1. Shaanxi Key Laboratory of Green Preparation and Functionalization for Inorganic Materials, School of Material Science and Engineering, Shaanxi University of Science and Technology, Xi’an 710021，China
2. Fundamental Science Institute of Cultural Heritage Conservation, Shanghai University, Shanghai 200444, China
3. Monalisa Group Co., Ltd.，Foshan 528211，China |
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Abstract The centuries of development of fine white porcelain in China has made the shortage of high-quality clay mineral resources increasingly serious. How to remove impurities of low-/medium-quality clay minerals and effectively utilize them have been attracted many attentions from potters, artists and material researchers. Iron, as a common impurity in minerals, plays a key harmful role in ceramic productions. One of the key technologies of improvement of low-/medium-quality clay minerals is to remove iron impurities. However, the unclear understanding of occurrence forms of iron in clay minerals limits the development of purification technology. The red clay in Guangdong province has a wide distribution and large storage. However, the high iron content restricts its further utilization as a high-quality resource. In this work, the occurrence forms of iron impurities in the red clay from Meizhou city, Guangdong province were investigated. Three types of impurities (red, yellow and gray green, respectively) in the red clay were selected and separated elaborately via washing and sieving processes. X-ray fluorescence spectrometer, scanning electron microscope equipped with energy disperse spectroscopy, transmission electron microscope equipped with selected area electron diffraction, visible-near infrared spectroscopy and first derivative spectra of visible absorption spectra were exploited to analyze the mineral assemblages, chemical composition, microstructure and spectral characteristics of the separated clay minerals. The occurrence forms of iron were identified. The results showed that iron was the key element that affected the appearance of the red clay. The clay minerals in the three samples were mainly composed of kaolinite and illite. In the red and yellow impurities, iron was absorbed or clamped on the surfaces of laminated clay minerals in the forms of hematite-goethite aggregate. In gray-green impurity, the iron was in the form of ions locked in Fe-Mg muscovite structure. The results also found that during the separation of red clay minerals, iron impurities were separated together with clay minerals from the red clay in the forms of both free and structural irons. This work is helpful for the selection of purification methods for southern red clay and for improving the processing efficiency and quality of low-grade clay.
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Received: 2020-05-15
Accepted: 2020-09-26
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Corresponding Authors:
LUO Hong-jie
E-mail: hongjieluo@shu.edu.cn
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