Study on spectrum of solvent extraction of chromium( VI) by primary amine

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 1H 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 1H 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 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.