| In recent years,with the rapid development of the textile industry,water pollution has become more and more serious which caused by dyes.The dye in the waste liquid has a very stable chemical structure,so it is more difficult to self-decompose in the natural.It's of great importance to degrade the dyes.Semiconductor photocatalytic oxidation has a better effect on the degradation of organic pollutants in wastewater,and has made great achievements in the field of environmental pollution control.At present,there are many methods for degrading organic pollutants,such as electrochemical method,biological decomposition method,adsorption method,physical sedimentation method,photocatalytic oxidation method,and so on.As a result of many years of study,researchers have found that the combination of adsorption and photocatalytic oxidation has great significance for the degradation of organic pollutants.Ti O2 has become one of the most promising photocatalysts all around the world due to its low cost,no secondary pollution,good photocatalytic and so on.However,due to the shortcomings such as the small particle size of Ti O2 which results in the difficulty of recycling and the fast electron-hole pair recombination.Therefore,we should take some available measures to modify Ti O2.Activated carbon has a better adsorption effect on dyes in wastewater because of large surface area,microporous structure,high adsorption capacity and high surface reactivity.Therefore,we composited Ti O2 with C to prepare Ti O2/C composites.Through this modification method,the synergy between adsorption and photocatalysis can be well exerted.This thesis mainly includes the following two aspects:The first system prepared Ti O2/C composites under different conditions by L9?33?orthogonal array method?three factors are:the concentration of titanium sulfate in the reaction solution,the C content in the composite material,and the firing temperature?to measure the optimal preparation conditions for the degradation of methylene blue?MB?.In this experiment,the Ti O2/C composites with approximately40 wt%carbon were prepared by calcination of precursors,formed from one-pot liquid phase reaction between Ti?SO4?2 and flour.These composites had a high specific surface area?up to about m2/g?.Calcination temperature had a large effect on the transformation of the crystal.When the calcination temperature was 850 oC,all the anatase was transformed into rutile.Research shown that Ti O2/C composites prepared with higher calcination temperature and titanium sulfate solution concentration are favorable for adsorption and ultraviolet photocatalytic degradation of methylene blue solution.However,the carbon content in the composites should be selected appropriately.The second system described the Ti O2/C composites with approximately 40 wt%carbon were prepared by calcination of precursors,formed from one-pot liquid phase reaction between Ti?SO4?2 and flour.All Ti O2/C composites displayed mesoporous structures with high BET surface areas?117?138 m2/g?and small crystal sizes of Ti O2?8?27 nm?.The content of graphitic carbon and rutile Ti O2 increased while surface areas and Ti O2 crystal sizes decreased for the Ti O2/C composites with calcination temperature increasing from 650 to 800 oC.When the calcination temperature was 800 oC,the anatase Ti O2 completely changed into the rutile Ti O2 in the Ti O2/C composite.The results from adsorption and photocatalysis showed that the Ti O2/C composite with higher calcination temperature exhibited a better adsorptive and photocatalytic degradation performance for the removal of methylene blue?MB?.For the entire rutile Ti O2/C-800 composite,the adsorption process of MB can be well described by the pseudo second order kinetic model,governed by chemical adsorption,and the maximum adsorption was about 15 mg/g.Under 15 W UV light irradiation for 3 h,the percentage of MB?14 mg/L?photocatalytic degradation on 50 mg of Ti O2/C-800 were 25.1%higher than that of maximum adsorption removal.These results suggest that the graphitized carbon had a significant effect on the adsorptivity and photocatalytic activity of Ti O2/C composite.At the same time,the absorption of light by Ti O2/C composites was successfully extended from the ultraviolet light to the visible light.When the calcination temperature was further increased higher than 850?,the Ti O2 in the composites gradually changed to Ti3O5.In the adsorption experiment,the adsorption capacity of materials were:Ti3O5>rutile phase of Ti O2>anatase phase of Ti O2,while in the ultraviolet photocatalytic degradation of methylene blue,the catalytic ability of materials were:rutile phase of Ti O2>anatase phase of Ti O2>Ti3O5. |
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