景德镇地区高岭石红外光谱分析

采用红外光谱实验结合氢氟酸化学处理方法深入研究景德镇地区高岭石结构特征。通过解析红外光谱图确定该区高岭石为无序高岭石范畴,其结构中含有似地开石结构BCBCBC的八面体空位取代。通过对比氢氟酸处理前后的红外图谱,分析出该地区高岭土不含有地开石和珍珠石这两种多型。实验表明红外光谱分析对高岭土中存在的次要矿物伊利石不灵敏,而利用氢氟酸处理可以有效地鉴别,因而提出了一种利用红外光谱鉴定高岭石-伊利石混合物相的新方法。

An IR spectroscopy study of kaolinite from Jingdezhen area

Kaolinite is an important kind of ceramic and chemical raw material, with its name derived from the Gaoling Mountain of Jingdezhen area in Jiangxi Province. The physical and chemical properties of kaolinite can be affected by the changes of the stacking structure and crystal defects between its unit layers. These variations in structure can be sensitively reflected in Infrared (IR) spectroscopy, and the high frequency range of IR, in particular, can be effectively used to analyze the OH stretching vibration in kaolinite. The sample studied was collected from the Gaoling deposit in the middle of Ehu granite, east of Jingdezhen. The residual kaolin was derived from the hydrolysis and weathering of granite and pegmatite in a hot and humid environment.The structural characteristics of kaolinite from the Gaoling deposit were studied by means of hydrofluoric acid (HF) treatment and infrared (IR) spectroscopy analysis. According to the Stockes' Law, the authors concentrated the frictions of kaolin in <4 μm, and mixed 200 mg of them with 16 mL and 8 mL hydrofluoric acid (12 mol/L) for 5 minutes, respectively. The residual clay JDZ-8HF-1 and JDZ-8HF-2 were studied by IR.In view of the very weak bands ν_2 and ν_3 of the IR spectrum in the high frequency range of the untreated sample JDZ-8HF(<4 μm), the authors hold that kaolinite from this area is in the range of disorder. This disorder is mainly caused by the decreasing of the angle between c~* axis and O-H axis within the kaolinite crystal and the increasing of the interlayer cohesive energy. Based on analyzing the characteristics of four bands in the high frequency range, the authors also consider that the structure of kaolinite has a dickite-like displacement of BCBCBC octahedral vacancy. From the low IR frequency range of JDZ-8HF (<4 μm), the characteristic peaks of kao- linite and quartz could be identified, but other phases within the sample could not be found. After 16 mL (12 mol/L) HF treatment, the IR spectrum of JDZ-8HF-1 displays a typical illite IR. From the intensity and pattern of 830 and 744 cm-1 bands, this illite can be determined as the 1Md polytype and possesses disorder structure. The authors failed to find any band related to kaolinite from the IR spectrum of JDZ-8HF-1, and the 3 weak bands 797, 779 and 372 cm~(-1) suggest that there exists a very small amount of quartz. The JDZ-8HF-1 IR spectrum suggests that 16 mL HF could dissolve some quartz and all kaolinite within kaolin from Jingdezhen area. The IR spectrum of JDZ-8HF-2, which was treated by 8 mL HF (12 mol/L), also shows the characteristic bands of 1Md illite and possesses more feature peaks related to quartz than JDZ-8HF-1. This means that less quartz within kaolin was dissolved by 8 mL HF.Based on a comparison between the IR spectra before and after the treatment with hydrofluoric acid, it is concluded that the kaolin from the Gaoling Mountain does not contain the polytypes of dickite and nacrite. The IR experiment results suggest that IR spectra may be insensitive to minor illite mixed in kaolinite. Through HF treatment, however, illite can be identified effectively. A new method is proposed in this paper for identifying the kaolinite-illite mixture.