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本文研究了钙基蒙脱石吸附Cr~(3+)前后及不同温度热处理后产物的结构变化,运用了X射线荧光光谱法、X射线衍射术、傅利叶变换红外吸收光谱术、电子自旋共振谱术、热重分析和差示扫描量热法(TG-DSC)等手段表征。结果显示Cr~(3+)以[Cr(H_2O)_6]~(3+)的形式替代Ca~(2+)存在于蒙脱石的TOT结构片的层间,在低于500℃的热处理后,d001变小,OH伸缩振动和中波数段向高波数偏移,ESR信号峰强度也有所增加。复水后,与加热的样品相比较,d001值有部分的增加,OH伸缩振动峰也向低波数偏移,ESR信号峰也有变化,表明Cr~(3+)位于六方孔较浅部位。当温度高于500℃时,产物的XRD显示出现绿铬矿(Cr_2O_3),根据XRD图谱以及ESR的g=1.97强度变化,尤其是产物的{001}衍射与TOT结构片高度相近及{060}衍射由尖锐的窄峰变宽的事实,表明蒙脱石沿{010}断裂细化并产生了类似于叶腊石的相,而由于复水后OH伸缩振动区域稍微地向低波数偏移,此时Cr~(3+)处在六方孔的深部。
In this paper, the structural changes of Ca-montmorillonite before and after the Cr (3+) adsorption and heat treatment at different temperatures were studied. X-ray fluorescence spectroscopy, X-ray diffraction, Fourier transform infrared absorption spectroscopy, electron spin resonance Spectroscopy, thermogravimetric analysis and differential scanning calorimetry (TG-DSC) and other means. The results show that Cr ~ (3+) replaces Ca ~ (2+) in the interlayer of TOT structure of montmorillonite [Cr (H_2O) _6] ~ (3+) After d001 becomes smaller, the OH stretching vibration and mid-wave number shift to high wave number, and the peak intensity of ESR signal also increases. Compared with the heated sample, the d001 value increased partially, the OH stretching vibration peak shifted to the low wave number, and the ESR signal peak also changed, indicating that Cr 3+ was located in the shallower part of the hexagonal well. When the temperature is higher than 500 ℃, the XRD of the product shows the green chrome ore (Cr 2 O 3). According to the XRD patterns and ESR g = 1.97 intensity changes, especially the {001} diffraction of the product is highly similar to the TOT structure and {060} The fact that diffraction is broadened by a sharp narrow peak indicates that the montmorillonite is refined along the {010} fracture and produces a phase similar to pyrophyllite, whereas due to rehydration, the OH stretching vibration region slightly shifts to a low wave number, Cr ~ (3+) in the deep six-hole.