红外和拉曼光谱的煤灰矿物组成研究

Characterization of Mineral Matter in Coal Ashes with Infrared and Raman Spectroscopy

研究煤灰中矿物质的性质通常从矿物组成的表征入手。为了分析两种高硅铝煤灰的矿物成分,采用傅里叶变换红外光谱(FTIR)、拉曼光谱和X射线衍射(XRD)技术对煤灰样进行了测试和综合表征,将FTIR和拉曼光谱的分析结果与XRD进行了比较。FTIR结果表明,在1 100~1 000cm^(-1)范围内高硅铝煤灰出现最强的特征峰,例如石英峰(1 089cm^(-1))和偏高岭石峰(1 042cm^(-1)),它们都归属于Si—O伸缩振动。对原始红外谱图进行二阶导数处理后,可获得重叠峰的峰位,有助于更完整的解析矿物吸收峰,从而获得更丰富的矿物组成信息。煤灰中硬石膏的红外和拉曼光谱发现,在1 157,1 126和674cm^(-1)的拉曼光谱峰与在1 151,1 120和678cm^(-1)的红外光谱峰振动模式分别相同且峰位接近,还存在一些完全不同的拉曼光谱与红外光谱峰,表明这两种光谱存在互补性。尽管煤灰中锐钛矿含量很低,但由于Ti—O的极化率很高,因此拉曼光谱显示锐钛矿的144cm^(-1)峰远远强于石英的461cm^(-1)峰。XRD结果表明,煤灰中主要存在石英、云母、赤铁矿、硬石膏和未知的无定形相矿物,FTIR和拉曼光谱综合分析的结果表明除了这些矿物,还存在偏高岭石、无定形氧化硅、长石、方解石和锐钛矿等。在定性分析方面,将FTIR和拉曼光谱结合起来比XRD单独获得的矿物组成信息更为详细。

The analysis of mineral matter in coal ash is based on the analysis and characterization of mineral composition.Mineral matter in two high-silicon and high-aluminum coal ashes were well characterized and identified with Fourier Transform Infrared Spectroscopy(FTIR),Raman spectroscopy,and X-ray diffraction(XRD).The results from combined use of FTIR and Raman spectroscopy were then compared with those of XRD.Results of FTIR show the presence of the strongest band in the range of 1 100~1 000 cm-1,such as the bands for quartz(1 089cm-1)and metakaolinite(1 042 cm-1),which are both assigned to Si-O stretching vibration.In contrast to original infrared spectra,the secondderivative infrared spectra show the positions of overlapping adsorption bands,which are masked in the original infrared spectra.The analysis of the overlapping adsorption bands are useful for the determination of mineral composition andthus provides more detailed information on mineral matter.For the anhydrite in coal ashes,the three Raman bands(1 157,1 126,and 674 cm-1)are obviously similar to the three corresponding FTIR bands(1 151,1 120,and 678 cm-1),for they show the identical vibration mode and close peak position.Moreover,the anhydrite in coal ashes shows other different bands in its FTIR and Raman spectra.Therefore,FTIR and Raman spectroscopy techniques are complementary for the identification of mineral phases in coal ashes.Although the anatase content of both coal ashes is very low,the Raman band of anatase(144 cm-1)is far more intense than the band of quartz(461 cm-1)because of the significantly high polarizability of Ti-O.The results of XRD show that the mineral components in both ashes are primarily quartz,muscovite,hematite,anhydrite,and unknown amorphous mineral phase.In addition to these minerals,combined use of FTIR and Raman spectroscopy indicates the presence of metakaolinite,amorphous silica,feldspar,calcite,anatase,etc.The combination of FTIR and Raman spectroscopy can therefore provide more detailed mineral composition than XRD for qualitative analysis of mineral matter in coal ashes.