| With the continuous development of science and technology,our environment is increasingly being destroyed,in which water pollution is becoming more and more serious and threatens the health of human beings and other creatures.Photocatalysis and adsorption technology has attracted widely attention as they are currently recognized one of the most effective methods to address the issue.In this thesis,a synergistic mechanism based on the photocatalysis and adsorption has been attempted to establish to achieve a better removal efficiency of organic pollutants.As a promising photocatalytic semiconductor material,bismuth vanadate has suitable band gap.Furthermore,its conduction band and valence band location are suitable for the broad prospect of application,which is limited by its low adsorption ability of pollutants and the slow migration of photogenerated electrons-holes.On the other hand,carbon-based materials have the large specific surface area and porous structure in general and are widely applied in the adsorption of pollutants.However,the removal efficiency is restricted by single adsorption effect.To solve the problem,these two materials have been combined together here.It is found that the sample named BVO-0.18C shows the best photocatalytic and adsorption performance simultaneously.The details of the thesis are as follows:1.The carbon sphere with well dispersion and homogenous morphology was prepared by hydrothermal method.And then,the compound BiVO4/C was synthesized by the secondary hydrothermal.The fabrication process was simple and the raw materials was cheap.Many techniques were used to characterized the composites,including SEM,XRD,Raman spectra,FT-IR spectra,DRS,XPS,EIS,BET and so on.The adsorption performance of BVO/C composites were studied and the sample BVO-0.18C was used as the best sample to compared with carbon sphere on the aspects of adsorption kinetics and thermodynamics.For adsorption kinetics,the pseudo first-order and the pseudo second-order dynamic models were used to evaluate the MB adsorption performance of the samples.The result shows that the pseudo second-order model is more suitable to describe the adsorption behavior and BVO-0.18C shows the better performance than carbon sphere.For adsorption isotherms,Langmuir and Freundlich isotherm models were used to fit.It is found that the Langmuir model matches the experimental data better.The value of K1 is lower than 1,which indicates that the samples are advantageous to the adsorption of MB.Consideration of the maximum MB adsorption capacity,the value of BVO-0.18C is a little higher than that of carbon sphere,which suggests that the adsorption performance of B VO-0.18C was not inferior to that of carbon sphere.2.In order to test the photocatalysis performances of the samples,methylene blue(MB)and rhodamine b(RhB)are chosen to be the target pollutants.As the result,the sample named BVO-0.18C shows the best photocatalysis performance.The efficiency of photodegradation for MB and RhB over BVO-0.18C is 11.56 and 4.42 times the same as pure BiVO4,respectively.This is mainly because that carbon sphere has good electrical conductivity and adsorption ability,which could effectively reduce the recombination ratio of photogenerated electrons and holes and enhance the contact between the composites and the pollutants at the same time.Beside that,the strong contact instead of mechanical mixing between bismuth vanadate and carbon sphere was been proved by a serious of experiments.At last,the recycle tests and quenching experiments have been taken,and the active species were study.In conclusion,the synergistic mechanism between photocatalysis and adsorption was established based on the bismuth vanadate and carbon sphere.And the sample with the best photodegradation and adsorption performance simultaneously was found out,which effectively improved the efficiency of pollutant removal. |
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