| The particle size of nanomaterials is between1～100nm. In addition to the basic characteristics, its also has more special qualities including quantum size effect, surface and interface effect, small size effect and the macroscopic quantum tunneling effect.Currently, nano-TiO2is one of the widespread concern nanomaterials, it has many valuable properties such as large special areas, excellent surface tension, powerful magnetism, good at absorb the UV rays, outstanding surface activitiy and so on. Due to the excellent qualities of nanoTiO2, it is widely used in a lot of areas including photocatalysis, maquillage, textile process, medicine, solar cell, et.al.The traditional methods to synthetise nano-TiO2can mainly separate into two parts including gas method and liquid method. Among that, the liquid method include hydro-thermal synthesis, sol-gel method, microemulsion method, liquid subside method. In recent years, using biomimetic synthesis method prepare nano-TiO2has increasingly become the research hotspot. It means that use biological molecules (including proteins, ploysaccharides, amino acids, etc.) as the template, through regulate the synthesis process to control the size, appearance and crystal form.Based on the principle of biomimetic synthesis, flower-like TiO2hierarchical spheres assembled by nanosheets were synthesized by glycine assistant via a simple hydrothermal approach. X-ray diffractometer (XRD), scanning electron microscopy(SEM), transmission electron microscopy (TEM), surface area analyzer were used to characterize the product. Parameters of the product included phase, morphology, microstructure, pore size distribution and specific surface area were considerated. Reaction time, temperature, solution pH and glycine dosage were studied via experiments to affect morphology. Results showed that the diameter of these flower-like spheres are about2μmn, with sheet thickness about20nm. The adsorption-desorption isotherms can be as certained as type IV, and specific surface area was about270.3m2·g-1with pore diameter of about56nm. The formation of flower-like TiO2spheres is an Oswald ripening process, reaction temperature, solution pH and glycine dosage all played an important role in control of shape and size of the as-synthesized TiO2nanocrystals.Furthermore, the adsorption properties of flower-like TiO2spheres on Pb(II) were studied, and the factors affecting the adsorption rate such pH, temperature, initial concentration of Pb(Ⅱ) and reaction time were investigated. All the results showed that with pH increasing, the adsorption rate increased, when the pH was4.0, the adsorption rate reached the highest point. As well, the adsorption reaction to reach equilibrium at210min. The adsorption isotherm data could be well described by Langmuir model better than Freundlich model. At the temperature of20℃、30℃and40℃, the maximum adsorption amount can be expected to reach76.34,76.34and77.52mg.g-1.The photocatalytic activity of this as-synthesized nano-TiO2was evaluated by the photocatalytic oxidation decomposition of methyl orange under sunlight illumination in the presence of hydrogen peroxide (H2O2). Reaction time, initial methylene orange, solution pH and catalyst dosage were studied via experiments, and important reaction conditions were optimizated using response surface method. From the results,we can see that the photocatalytic activity of the obtained TiO2was higher than that of commercial TiO2, the degradation rate can reached98%at30min. According to the regression equation, the best array were obtained:the pH of methyl orange solution was4.02, initial Methylene Orange concentration was9.06mg/L and flower-like sphere dosage was22.78mg. |
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