Research On Degradation Of Organic Dyes By Ultrasound Combined With TiO₂

In the course of the development of human society,the wastewater discharged into the environment contains a large amount of soluble organic pollutants,which poses a certain threat to the survival of human beings and other organisms.How to effectively treat wastewater has become one of the problems faced by human beings.At present,the main treatment technologies include:biotechnology,chemical technology and physical technology,but they have their own defects in the treatment of wastewater.With the deepening of the research on ultrasonic cavitation,the research on the degradation of organic pollutants in water by ultrasonic catalysis has attracted more and more attention.In this paper,rhodamine B and methyl orange are used as simulated solutions of organic pollutants in wastewater to be degraded.Nanoparticles were obtained by the sol-gel method and heat treatment method.And then the degradation experiments of rhodamine B and methyl orange were carried out by using the method of ultrasonic radiation-mechanical agitation combined with nanoparticles,and the degradation mechanism of methyl orange and rhodamine B under the reaction system was investigated.The main research contents and results are as follows:(1)In this paper,the method for preparing pure TiO2 nanoparticles was studied.Nanoparticles were obtained by sol-gel method and heat treatment at 800 degree temperature for 3 hours in muffle furnace.The crystal structure of nanoparticles was determined by X-ray diffraction(XRD),it was found that the prepared pure Ti02 nanoparticles were composed of two different crystal phases,anatase and rutile.The surface morphology of pure Ti02 nanoparticles was studied by scanning electron microscopy,it was found that the distribution of nanoparticles was relatively uniform and regular,and the shape was close to spherical.The chemical composition of the prepared nanoparticles was analyzed by energy dispersive X-ray(EDS)analysis,it was found that pure TiO2 nanoparticles were mainly composed of Ti and O.The degradation of rhodamine B was significantly improved by the combination of prepared Ti02 nanoparticles and ultrasonic catalysis-mechanical agitation.The optimum degradation conditions are as follows:revolutions per minute is 500r/min,pH is 7,the initial concentration of rhodamine B is 20mg/L,the frequency of ultrasonic vibration is 40kHz,the output power is 300W and the amount of adding nanoparticles of TiO2 is 500mg/L.Finally,it was concluded that the degradation efficiency of the reaction was improved by combining ultrasound with mechanical agitation and then adding the appropriate amount of nano-solid particles.(2)And.the Fe-doped TiO2 nanoparticles were also made in the same way.The crystal structure of nanoparticles was determined by X-ray diffraction(XRD),it was found that iron doping did not change the crystal structure of the TiO2 nanoparticles.However,Fe3+ions as dopants hindered the transition from anatase to rutile.The surface morphology of TiO2 nanoparticles was studied by scanning electron microscopy,it was found that the particle size of Fe-doped Ti0Z is smaller than that of pure TiO2 nanoparticles,and the particle size of TiO2 nanoparticles increases with the increase of Fe content in the samples.The chemical composition of the prepared nanoparticles was analyzed by energy dispersive X-ray(EDS)analysis,it was found that the iron-doped TiO2 nanoparticles were mainly composed of Ti,0 and Fe.The degradation of methyl orange was significantly affected by the combination of modified TiO2 prepared and ultrasonic catalysis-mechanical agitation.At the same time,it was concluded that the degradation rate of 0.5%Fe-doped modified TiO2 nanoparticles was higher.The optimum degradation parameters are as follows:the initial dosage of nanoparticles is 500mg/L,the pH is 3,the time is 60min,the initial concentration of methyl orange is 10mg/L,the frequency of ultrasonic vibration is 40kHz,and revolutions per minute is 500r/min.Modified TiO2 nanoparticles had good stability and reusability under ultrasonic catalysis-mechanical agitation.(3)Response Surface Methodology(RSM)was performed on the experimental data obtained from degradation of methyl orange.Statistical model was established by quadratic equation,and the optimum experimental conditions were obtained by model analysis:the initial dosage of modified TiO2 nanoparticles was 490.50mg/L,the initial concentration of methyl orange was 9.22mg/L and the frequency of ultrasonic vibration was 36.02 kHz.The effects of dark and light on the degradation efficiency were studied.It was found that sunlight had no significant effect on the degradation rate of the whole degradation system.At the same time,the effect of physical adsorption of nanoparticles on the degradation rate was studied.It was found that the adsorption amount of dyes on nanoparticles could be neglected under the intensity of ultrasonic catalysis-mechanical agitation.