Effect of Preparation Methods on Phosphate Adsorption by Iron-Titanium Binary Oxide: Coprecipitation and Physical Mixing

To investigate the effect of preparation methods on surface characteristics and adsorption properties of the formed metal composite oxides,two kinds of iron-titanium binary oxides were synthesized by a coprecipitation method or a physical mixing method and were denoted as CFe-Ti and MFe-Ti,respectively. The prepared CFe-Ti and MFe-Ti were systematically characterized using SEM, XRD,BET,and FTIR techniques. Their phosphate adsorption behaviors were also studied via batch adsorption experiments. Compared with pure FeOOH and TiO_2,CFe-Ti exhibited a looser nanostructure with more pore and surface hydroxyls. Moreover,the CFe-Ti had a high maximal phosphorus adsorption capacity of 40. 6 mg·g~(-1) ,which is about 1. 5 times and 2. 4 times as high as that of pure FeOOH ( 27. 2 mg·g~(-1) ) and TiO_2 ( 16. 7 mg·g~(-1) ) ,respectively. This suggests that an obvious synergistic effect is present in the CFe-Ti system. However,the morphology and structure of MFe-Ti were not significantly different from those of pure FeOOH and TiO_2 . The maximal adsorption capacity of MFe-Ti was 22. 7 mg·g~(-1) ,which is obviously lower than that of CFe-Ti and even lower than that of pure FeOOH. Evidently,there is no synergistic effect in the MFe-Ti system. In addition,phosphate adsorption mechanisms at the surface of CFe-Ti and MFe-Ti were the same as those of their component oxides,and chemical adsorption occurred at the surface of the oxides through the formation of inner-sphere complexes. Therefore,the surface characteristics and adsorption properties of the metal composite oxides were closely related to their preparation methods. The coprecipitation method was a simpler and more economical way than the physical mixing method to fabricate a highly effective iron-titanium binary oxide for phosphate adsorptio