科研之友
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摘要
In this study, we used the oxalic acid cross-linking activated alumina/chitosan biocomposites (AACB) for defluoridation from aqueous solution for the first time. Scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS), Zeta potential, Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron (XPS) spectroscopy were employed to study the structure and F- adsorption sites of AACB. Langmuir and Freundlich isotherms fit well with the experimental data, indicating a feature of monolayer F- adsorption and physicochemical adsorption on the surface of AACB. Zeta potentials with pH variation of AACB before and after fluoride sorption confirm that chemical adsorption with electrostatic interaction governs the adsorption process. Practical application of AACB was evaluated by F- adsorption under simulated F- concentration and pH value of drinking water which is naturally polluted by fluoride. The results demonstrated that AACB reduced F- concentration from 4.52 mg/L to 0.57 mg/L, below the F- permitted concentration (1.0 mg/L) in drinking water set by Ministry of Environmental Protection of the People's Republic of China. Furthermore, AACB keeps a high defluoridation effect under low basicity condition. FTIR and XPS analysis showed that -NH and Al-O work as F- adsorption sites. AACB presents a combined effect between alumina and chitosan during F- adsorption. This is a reason for the higher defluoridation capacity of AACB than alumina and chitosan separately. The oxalic acid cross-linking biocomposites showed potential application on purification of natural fluoride polluted water body.
