RESUMEN
The adsorption of pentachlorophenol on hematite was studied through adsorption experiments and FTIR analysis. The pH adsorption isotherms of pentachlorophenol onto hematite were obtained by the static state experiments. The largest adsorption quantity occurred at about pH 6. The adsorption quantity at pH 8.5 of the isoelectric point of hematite was about 31% of the largest adsorption quantity. Fourier transform infrared (FTIR) spectroscopy was used to analyse the change of hematite before and after PCP adsorption, and the species of PCP on hematite. It was discovered that: (1) the typical peak at 565 cm(-1) of the Fe-O bond in alpha-Fe2O3 did not change before and after adsorption, and the adsorption occurred on the surface of hematite. (2) At pH 6.0, the stretching vibration peak at 3 438 cm(-1) due to the hydrogen bond formed between O-H on the surface of alpha-Fe2O3 and water molecules shifted to 3 417 cm(-1). The bending vibration peak of H-O-H+ on the surface at 1 643 cm(-1) was weakened because of complex reaction. The peak owing to Fe-OH bond was displaced from 1 050-1 100 cm(-1) to 950 cm(-1) with increased intensity. The C-O bond stretching vibration peak of PCP was displaced from 1 215 to 1 122 cm(-1). The main interaction between PCP and hematite was static electric interaction. (3) At pH 8.5, the stretching vibration peak of the hydrogen bond formed between O-H on the surface of alpha-Fe2O3 and water molecules was displaced from 3 438 to 3 428 cm(-1). The bending vibration peak at 1 643 cm(-1) was obviously weakened because of the hydrogen bonding. The H-O-H+ bending vibration peak at 1 050-1 100 cm(-1) was displaced to 947 cm(-1) with obviously increased intensity, indicating that the interaction was mainly through hydrogen bond.
RESUMEN
IR spectra were used to analyse the azo dye solution decoloration action by two kinds of iron oxyhydroxides. It was discovered that: (1) Acid Red G and methyl orange are apt to form complex on the surface of iron oxyhydroxides > FeOH, especially Acid Red G. which possesses two -SO3Na structures has a relatively high decoloration efficiency as a result of complexation reaction; (2) after 2 hours adsorption, the IR spectra of iron oxyhydroxides show characteristic wave numbers at 1 033 and 1 030 cm(-1) which belong to -SO3Na, whereas the peaks at wave numbers between 1 450 and 1 400 cm(-1), which belong to azo dye, disappear. These phenomena indicate that azo dye molecules are adsorbed on the surface of iron oxyhydroxides due to the negative -SO3Na structure, and at the moment azo dye molecules are adsorbed on the surface of iron oxyhydroxides, the electron transfer occurs between the azo dye molecules and the iron oxyhydroxides surface's Fe3+ centre, which could lead to the rupture of azo bond. It can be infered that the decoloration of azo dye molecules is the co-effect of the selective chemical absorption and the oxidation-deoxidation effect on the surface of iron oxyhydroxides.