| Along with the development of the society and economy, the demand of the water resource becomes greater. On the other hands, the water pollution is still deteriorating, which is a critical threat for human health, leading to the aggravation of the water resource shortage. Therefore, development of the efficient water treatment technology is significant for relief of the water crisis and improvement of the water environment. Heterogeneous Fenton oxidation technology has high efficiency for the organic contamination removal. However, harsh reaction conditions and inefeciency of catalysts are the main drawback.In this paper, a serias of novel nanomaterials were synthesized as heterogeneous catalysts in order to solve the problems existed in the Fenton oxidation technology. The catalytic capacity of these catalysts was evaluated through the experiemnts carried out at near neutral condition (pH5.0). And then, the feasibility using sulfate radical oxidation technology as an alternative technology for Fenton technology was investigated. Some creative results were obtained.Using Fe3O4nanoparticles as heterogeneous catalysts, its performence of H2O2decomposition for4chlorophenol removal was assessed at pH5.0. The results showed that4chlorophenol can be oxidized completely in the Fe3O4/H2O2system. The removal efficiency of4chlorophenol was up to96.8%and the concentration of dissolved iron ion was only about2mg/L as the reaction finished. The addition of the radical scavenger lead to the decline of the4chlorophenol removal efficiency. In the successive repeated experiments, the removal efficiency of4chlorophenol was down to91.8%in5th experiment when96.8%in1st experiment, while the removal efficiency of TOC was down to42.7%when48.7%in1st experiment. Both of the results demonstrated the good stability and reusability of the Fe3O4nanoparticles.To solve the low catalytic capacity of the Fe3O4in Fenton system, Fe3O4Au nanocomposites were designed and synthesized as Fenton catalysts. The catalytic capacity of the as synthesized solids was higher than Fe3O4. Additionally, comprehensive consideration of the cost and catalytic performance, the optimal Au content in the nanocomposites was1%in weight. The activation energy of Fe3O4Au/H2O2system was23.18kJ/mol, far lower than the Fe3O4/H2O2system. Meanwhile, metal ions were in absence in the solution after the catalytic experiment. After8successive reactions, the4chlorophenol removal efficiency during the4h was down to90.5%from the94.6%in1st experiment, which exhibited the high stability of the Fe3O4Au nanocomposites. Fe3O4Ag nanocomposites were prepeared by means of the method with some modification of the Fe3O4Au synthesis method for H2O2catalytic decomposition. The results showed that the catalytic property of Fe3O4Ag is much higher than Fe3O4Au. However, the results were induced by the dissolution of the Ag. On the other hands, as a disinfectant, Fe3O4Ag can make the bacterials death rapidly and efficiently. Moreover, no dissolved Ag ion appeared in the solution. Its reusability eliminated the subsequent risk of Ag particles.Due to the high cost of the Fe3O4Au nanocomposites, Fe3O4MnO2core shell nanocomposites were synthesized by means of the reaction between Fe(OH)2and KMnO4as Fenton catalysts. The as synthesized nanocomposites can make the H2O2decomposed efficiently to oxidize the4chlorophenol. And then, the composites with Fe/Mn molar ratio of6:1had the highest catalytic capacity, which demonstrated the synergetic effect existed between Fe3O4and MnO2. The active energy of the Fe3O4MnO2/H2O2was30.42kJ mol1, lower than the Fe3O4/H2O2system.Next, the Fe3O4MnO2were applied to activate the Potassium peroxymonosulfate for the4chloropehnol removal to overcome the drawbacks of Fenton reaction including low reation rate, high dosage of the oxidant and pH adjustment. According to the experimental results,4chlorophenol can be degradated completely in the Fe3O4MnO2/Oxone system. The catalytic capacity of Fe3O4MnO2towards potassium peroxymonosulfate was higher than MnO2. At the same time, the nanocomposites with Fe/Mn molar ratio of4:1had the highest catalytic activity. The successive experiments revealed the chemical and catalytic stability of Fe3O4MnO2. In comparison with previous catalytic systems, Fe3O4MnO2/Oxone had the higher degradation efficiency and was close to the practical engineering. In addition, Fe3O4MnO2core shell nanocomposites were used as oxidants and adsorbents for the removal of As (III) in aqueous solution. The results showed the nanocomposites with Fe/Mn molar ratio of3:1had the highest saturated adsorption capacity, up to80.40mg/g. The adsorption kinetic was fitted well with the pseudo second order kinetic model. According to the XPS analysis, the As (III) adsorbed on the surface of was oxidized to As (V).Above of all, application of heterogeneous catalysis technology in presence of nanocomposites for the removal of typical organic contaminants such as chlorophenol has broad prospects and is an efficient way to solve the environmental pollution, which should be studied entensively in future. |
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