FTIR Spectroscopic Analysis of Cu2+ Adsorption on Hematite and Bayerite

The changes in surface hydroxyl structures and their absorption peaks after the adsorption of Cu2+ on the hematite and bayerite were studied by FTIR spectroscopy under the different pH values and Cu2+ concentrations. The result indicated that: (1) with the increase of Cu2+ concentrations, the H-O-H and OH deformation vibration of the hematite participated in the adsorption and Cu2+ combined with the Fe-O structure strongly, then Fe-O-(Cu) had been formed on the hematite surface. (2) In acid conditions, H+ in the solution destroyed the O-H structure of hematite surface and the existence of NO3- prompted the production of a new peak (1 131 cm(-1)). With pH value increasing, the hydroxy structure of hematite surface changed gradually from stretching vibration to deformation vibration, then the structures of Fe-OH and Fe3+-O2- constantly changed. (3) The adsorption of Cu2+ on the bayerite happened in the high wave position. With the Cu2+ concentration increasing, the free OH bending vibration, the OH- stretching vibration and its H-O-H bending vibration were all involved in the adsorption, and at the same time, Al3+ of Al-O was gradually replaced by Cu2+, which enhanced the vibration intensity of the low waves position. (4) With the increase in pH, the Al-OH bending vibration and Al-O stretching vibration changed gradually, which indicated that AlOCu+ and AlOCuOH structure had been formed on the bayerite surface after the adsorption.