| Polycyclic aromatic hydrocarbons (PAHs) are typical persistent poisonous matters known for their toxic, mutagenic and carcinogenic properties which are the largest number of carcinogenic single chemical species in the current known environment. The naphthalene series wastewaters are produced during the course of synthesize phthalic anhydride, dyestuffs and pesticides using the most water soluble PAHs-naphthalene as raw material.The wastewaters are characterized with component complex, higher concentrations, toxicity, darker color, acidity or alkalinity and toxicity, and are difficult to be degraded under natural environment. Therefore it is very meaningfulness to study and look for the practical technology that is used for processing wastewater of our countrvy's naphthalene series.In recent years, TiO2 nanocatalysts are widely used in wastewater treatment as a kind of new environmental function materials. However, because suspended TiO2 is hard to be separated from wastewater, the cost of this treatment is raised much higher. In this paper, superparamagnetic Fe3O4 nanoparticle in the form of ferrofluid (supplied by Harbin Normal University) was selected as the magnetic nanocore to produce homogeneous coated Fe3O4-SiO2 support using the well-known stober method. Then immobilizing TiO2 nanocatalyst on Fe3O4-SiO2 magnetic nanocores the monodispersed TiO2/Fe3O4-SiO2 (TFS) nanocatalyst with typical "coreshell" structrue was successfully obtained through sol-gel process. The prepared magnetic separable TiO2 nanocatalysts were characterized by scanning electron microscopy (SEM), Xray diffraction (XRD) and Fourier-transform infared spectroscopy(FTIR) methods which confirming that has synthesized a magnetic separable nano-scale composite TiO2 photocatalyst.To study the effect of the TFS composite photocatalyst's catalyzing and dagrading the contamination, this paper chooses the representational contamination of polycyclic aromatic--naphthalene to conduct the degradation experiment, and optimizes the experimental operating conditions through the method of central composite design of the response surface methodology, makes sure the influencing sequence of these experimental operating conditions. In the meanwhile,it takes three methods:numerical derivation,matlab simulation and genetic algorithm to get the more precise optimal values of operating parameters, so as to make the dagradation rate of naphthalene reach the maximum.The experiment result indicates that the TFS composite photocatalysts behave a high efficient ability of degradation,and its apparent reaction rate is fast. The optimal experimental condition which photocatalysis acts to naphthalene is:illumination time is 97.1min, pH-value is 2.1, the amount of compound catalyst is 96.2mg/L. In the conditon above, the optimized naphthalene degradation rate is high to 97.39%. Though model verification, the maximum relative error between this model predictive value and the experiment value is no more than 4% which illustates that this model has a good prediction effect to the results of experiment and shows a relatively fine guiding significance. It detects 12 kinds of determined intermediates and 3 kinds of uncertain intermediates in the progress of photocatalysis degradation reaction by using the GC-MS separation and analysis method, and conjectures the degradation pathway which can explain these compounds' formation and transformation.7... |
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