Oxidized mesoporous ZrO2/carbon composites for arsenic removal
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This study is mainly focused on the synthesis and characterization of oxidized mesoporous ZrO2/Carbon composites, determining the best air oxidation time, and comparing the adsorption performances of arsenate on oxidized mesoporous ZrO2/Carbon composites and unoxidized composites. The mesoporous ZrO2/Carbon composites were synthesized via a facile evaporation induced triconstituent co-assembly approach by using Pluronic F127 as a template and zirconium oxychloride octahydrate and resol as Zr and carbon sources, respectively(Li, Xu et al. 2010). The oxidized samples were produced by oxidation at 400℃ in the presence of air. The oxidized composites were characterized by X-ray energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). Preliminary experiments showed a relatively low adsorption capacity of unoxidized composites, while air oxidation could improve the arsenic adsorption performance by mesoporous ZrO2/Carbon composites. The best air oxidation time was then determined by investigating the adsorption of arsenic by samples oxidized for various time, tested at pH = 4.7 and an initial arsenic concentration of 50ppb. Experiments demonstrated that the best air oxidation time was 20min (OMZC-20) based on its ability to adsorb arsenate. Initial arsenate concentrations and pH values varied while the ionic strength was kept constant by adding NaNO3. The Freundlich model fitted experimental data better than the Langmuir and Temkin models. The optimal pH values for arsenate adsorption was 2-4, and the adsorption capacity decreased with increasing pH from neutral to alkaline values.