Removal Of Dyes, Heavy Metals And Organic Pollutants And Studies Of Site Energy Distributio Function Based On Nano-ferrite Materials

Water pollution problems have attracted increasing public concern in China with the development of industrial revolution and rapid modernization process, especially the dye, heavy metals and organic pollutants wastewater. In this paper, based on nano-ferrite materials, with the Congo red and Rhodamine B dye wastewater, heavy metal Pb and Atrazine, Carbamazepine, Bisphenol A, Norfloxacin and 4-nitrophenol organic pollutants wastewater as the goal, we are hoping to extend application range which the nano-ferrite materials adsorption treatment of water pollution, and based on the adsorption of organic pollutants, we studied the site energy distributions of nano-metal oxide material, oundation for research to expand site energy distributions. The details are summarized as follows:1. In this work, Bismuth ferrite（Bi FeO3） with high-purity was successfully synthesized. The thorough characterization of BiFeO3 included X-ray diffraction, Scanning electron microscopy, BET special surface areas and pore structures, UV–vis diffuse reflectance spectra. The adsorption and photocatalytic performance were studied by removal of Congo red and Rhodamine B. The adsorption isotherms were confirmed to fit to the Langmuir theory and the adsorption kinetics were consistent with pseudo-second-order model. The adsorption capacities for Congo red and Rhodamine B were 24.27 mg g-1 and 7.96 mg g-1, and the adsorption rates were 0.0243 and 0.0406 g mg-1 min-1, respectively. Photocatalytic activities of the photocatalysts were studied by employing the photocatalytic degradation of Congo red and Rhodamine B under visible-light irradiation. The results indicated that the removal rate of Congo red was superior to that of Rhodamine B. BiFeO3 removal the Congo red can be substantially completely degraded in 4 h, while Rhodamine B with only 30% in the BiFeO3 photodegradation system by synergistic effect of the adsorption and photocatalysis.2. In this paper, nanoporous adsorbents of ZnO/ZnFe₂O₄/C were synthesized by using metal organic framework（FeIII-modified MOF-5） as both the precursor and the self-sacrificing template, and were characterized the material by XRD, SEM, TEM, VSM, BET and so on. Adsorption properties of ZnO/ZnFe₂O₄/C toward Pb（II） ion were investigated, including pH effect, adsorption equilibrium, adsorption kinetics. The adsorption isotherms was well described by Langmuir isotherm model and the adsorption kinetics was more consistent with the pseudo-second-order model. The MOF-derived inorganic adsorbents exhibited highly absorption performance with maximum adsorption capacity of 344.83 mg g-1. X-ray powder diffraction and high-resolution X-ray photoelectron spectroscopy suggest that Zn（II） was substituted by a significant portion of Pb（II） on the surface of ZnO nanocrystals. Microscopic observations also demonstrate the effect of Pb（II） ion on ZnO crystal as reflected by considerably reduced average particle size and defective outer layer. Quantitative measurement of the released Zn（II） ions and the adsorbed Pb（II） ions indicated a nearly liner relationship（R2=0.977）. We propose the mechanism of ZnO/Zn Fe₂O₄/C adsorption Pb（Ⅱ） that was occurs ion exchange between Pb（II） and Zn（II） during the process of adsorption; thus the lead with high concentration and high toxicity can be converted to low concentration and low toxicity of zinc, this may provide a new way to purify the heavy metal wastewater with high toxicity. Moreover, Pb-containing ZnO/ZnFe₂O₄/C adsorbents are strongly magnetic allowing their separation from the water environment by an external magnet.3. The metal oxide adsorbent named Zn O/ZnFe₂O₄/C was synthesized by using metal organic framework as the self-sacrificing template. Sorption of Atrazine, Carbamazepine, Bisphenol A, Norfloxacin and 4-nitrophenol onto ZnO/ZnFe₂O₄/C was investigated, and the adsorbing capacity followed the order of 4-nitrophenol > Norfloxacin > Bisphenol A > Carbamazepine > Atrazine. All isotherms were fitted well by the Dubinin-Ashtakhov（DA） model, and the approximate site energy distributions were calculated based on DA model. We can also get this sort of the adsorption capacity according to the approximate site energy distributions. In addition, we also calculated the average site energy, and studied the relationship between the average site energy and adsorption capacity, and the results show that a significantly positive correlation between the average site energy and adsorption capacity.