伯胺萃取Cr(Ⅵ)的光谱学研究

Study on Spectrum of Solvent Extraction of Chromium(Ⅵ) by Primary Amine

利用等离子体发射光谱(ICP-AES),激光拉曼光谱,傅里叶变换红外光谱(FTIR),核磁共振(1HNMR)分析技术对伯胺在近中性条件下从水溶液中萃取Cr(Ⅵ)的过程进行了研究。ICP-AES对萃取前后水相Cr(Ⅵ)浓度测试结果显示,在近中性条件下,伯胺仍然能够萃取Cr(Ⅵ)。激光拉曼光谱显示,未经酸化的伯胺从近中性水溶液中萃取Cr(Ⅵ)后在890cm-1处出现新峰。红外光谱显示在近中性条件下直接使用伯胺萃取Cr(Ⅵ)与经酸化处理后按离子交换历程萃取的萃取机理不同,Cr(Ⅵ)进入有机相后在885cm-1处产生与拉曼光谱对应的新峰。1H核磁共振波谱显示,—NH2上的质子峰向低场移动,伯胺在萃取过程中通过氢键与Cr(Ⅵ)结合。综合以上不同分析手段得到的结果可以推断,伯胺在近中性的水溶液中是以溶剂化萃取历程通过氢键结合方式萃取Cr(Ⅵ)。

The Cr（ Ⅵ ） solvent extraction in near neutral aqueous solution by primary amine was experimentally studied by the inductively couple plasma-atomic emission spectrometry （ICP-AES）, laser Raman spectroscopy, Fourier transform infrared spectroscopy （FTIR） and ^1 H nuclear magnetic resonance spectroscopy （^1H NMR）. The ICP-AES analysis of the aqueous phase before and after solvent extraction showed that primary amine could extract Cr（Ⅵ） from nearly neutral solution. Laser Raman spectroscopy of loaded organic phase showed that a new peak appeared at 890 cm^-1 after Cr（ Ⅵ ） was extracted by primary amine. FTIR showed the process that primary amine extracted Cr（ Ⅵ ） from nearly neutral aqueous solutions was different from anion exchange mechanism, and the Cr（ Ⅵ ） extracted into the organic phase resulted in the appearance of the peak at 885 cm^-1 of FTIR which justified that the peak at 890 cm^-1 of Raman was caused by Cr（ Ⅵ ）. The ^1 H NMR spectroscopy showed that the value of chemical shift of protons of -NH2 decreased after extraction, and it is believed that primary amine was associated with Cr（Ⅵ） through hydrogen bonding. On the basis of the spectroscopic analysis results above, the the mechanism of Cr（ Ⅵ ） extraction by primary amine from nearly neutral aqueous solutions was believed to be solvation with molecular association between primary amine and Cr（Ⅵ） through hydrogen bonding.