广东省红粘土中铁杂质及其赋存形式分析

中国细白瓷历经数百年的发展，使得优质粘土矿物资源的紧缺形势日益严峻，对中低品质矿物的提纯和利用越来越受到关注。其中，劣质矿产的除杂即是提高其品质要解决的重点问题。铁杂质是陶瓷生产中最主要的有害物质，对Fe的赋存方式进行探究可为除杂技术的应用建立相关基础。目前，对中低品质的粘土矿物中铁杂质赋存形式的研究仍较少。广东省红粘土分布广、储存量大，但其较高含量的Fe降低了其使用价值，限制其作为优质资源进一步利用。该研究对中国广东省梅州市的低品质红粘土中铁杂质和其赋存形式进行分析。Fe在矿物中的赋存形式复杂，结晶程度较低，采用传统的测试方法难以对其进行有效地分析。因此，通过拣选红粘土原矿中红、黄、灰绿三种杂质组分，并分别进行淘洗和过筛法分离粘土矿物。采用X射线荧光光谱、扫描电镜和能谱、透射电镜和选区电子衍射、可见光-近红外吸收光谱仪及可见光一阶导数光谱法对其矿物组成、化学成分、显微结构及谱学特征进行测试分析，探讨Fe元素的赋存形式。结果表明：Fe元素是影响该红土矿外观颜色的最主要元素。所有样品中粘土矿物主成分为高岭石和伊利石。红色和黄色杂质组分中，Fe元素主要以赤铁矿-针铁矿的自由团聚体夹杂或附着于片状粘土矿物表面；灰绿组分中Fe元素主要以Fe-Mg云母的结构铁形式存在。研究发现，在对红粘土矿物的分离过程中，Fe杂质以自由铁和结构铁的形式随着粘土矿物一同被选出。该研究结果有助于南方红粘土提纯方法的选择，并有助于提高低品位粘土的处理效率和质量。

Analysis of Iron Impurity and Its Occurrence Form in Red Clay of Guangdong Province

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.