Photocatalytic Treatment Of Macrolide Antibiotics Wastewaterwith TiO₂ Loaded Graphene

With the increase of the domestic pharmaceutical enterprises of antibiotic,the pressure of antibiotic wastewater treatment is also increased.So it is very necessary to find a kind of antibiotic wastewater treatment technology which is energy-saving,economic,highefficiency and without secondary pollution.In this thesis,the graphene modified TiO₂,S doped and graphene modified TiO₂ composite were prepared.And the catalysts were characterized by XRD,SEM,TEM,XPS,UV Vis diffuse scattering;The catalytic performance of these catalysts also have been studied through degradating tests of macrolide antibiotics azithromycin and roxithromycin;The photocatalytic mechanism of composites catalyst were explored by adding the hole and the hydroxyl radical scavenger;The degradation process and the intermediate products of azithromycin were analyzed by liquid chromatography-mass spectrometry.Conclusions are as follows:1)The GO was synthesized by modified traditional Hummer's method and the TiO₂ was prepared by sol-gel method.Then the composite of TiO₂ modified by graphene?TiO₂-RGO?was synthesized through TiO₂ reducing GO under UV-B lamp.The experiment results showed that the optimal technological conditions for degredating azithromycin solution were as follows: when the concentration of azithromycin 100 mg/L,the catalyst dosage 500 mg/L,and the initial pH 4,the degradation rate of TiO₂-RGO of Azithromycin reached to 98% using UV light radiation,reached to 73% using simulated sunlight.And the effect of hydroxyl radical and hole on the degradation process were almost equal through the mechanism test.Meanwhile,the degradation process and intermediate products were proposed on the basis of chromatograph mass spectrometer analysis.Futhermore,products can be divided into several kinds: hydroxy product,methylated product,hydroxyl methylation product,the fragment of the inorganic matter and the small mass.2)The GO were efficiently synthesized by high pressure closed Hummer's method and the TiO₂ were prepared by Sol-gel method.The preparation of S doped S-TiO₂ by wet method?roasting?.Then preparing the S doped and graphene modified TiO₂ composite?S-TiO₂-RGO?catalysts by photo-reduction using S-TiO₂ as photocatalyst.The performance of the catalyst was evaluated by photocatalytic degradation of roxithromycin,and the photocatalytic degradation experiment of roxithromycin was optimized.The experiment results showed that the optimal technological conditions for degradatingroxithromycin solution were as follows: Under the visible light,when the concentration of roxithromycin 100 mg/L,the catalyst dosage 500mg/L,and the initial pH was 4,the degradation rate of S-TiO₂-RGO of roxithromycin reached to 91.3% using simulated sunlight.The result of mechanism test shows that the hydroxyl radical plays a major role in the process of degradation,and the hole plays a minor role in the process of degradation.The mineralization of roxithromycin in the process of degradation was tested by monitoring the TOC value of the solution,the results shows that the TOC degradation rate was increased with the roxithromycin degradation rate increased.