Preparation And Performance Study Of Fe₃O₄/palygorskite Composite Catalys

With the rapid development of social economy and industrial level,the ecological environment has been seriously damaged.How to prevent and control pollution and protect the natural environment has become the focus of restricting social progress.In this paper,Fe₃O₄/palygorskite composites were prepared with Qianxi-Dafang palygorskite as the carrier and applied to the treatment of environmental water pollution.The preparation methods and degradation properties of Fe₃O₄/palygorskite composites were studied by means of XRD,XRF,bet,zeta potential,SEM,FTIR,TOF and aspect ratio.The main contents are as follows:（1）Fe₃O₄/palygorskite composite catalyst material was successfully prepared by ultrasonic coprecipitation method,and the influence factors of its preparation conditions on the nano Fe₃O₄ crystal size in the composite were studied.Increasing the preparation temperature is conducive to the growth of Fe₃O₄ crystal,reducing the Fe3O4 load ratio is conducive to the reduction of Fe₃O₄ crystal size,and the influence of load ratio on the crystal size is greater than the preparation temperature.（2）The properties of the composites were characterized by various analysis methods.XRD analysis showed that the Fe₃O₄ characteristic diffraction peak of the composites was obvious and the intensity was high;FTIR analysis showed that the characteristic peaks of Fe OOH and Fe-O bonds were added in the composites;TOF analysis shows that the content of Fe in the surface element composition of the composite is significantly higher than that of purified palygorskite,and its distribution is closely related to the distribution of Mg,the characteristic element of palygorskite;The characteristic peaks of Fe 2P_2/3 and Fe 2p_1/3 of Fe₃O₄ and Mg(OH2) and Mg O of palygorskite were measured by XPS;The particle size of Fe₃O₄ in the composites was determined by XRD and electron microscope.The particle size was about 5-6nm.（3）The catalytic degradation of organic pollutants by composites was experimentally studied.It was found that the degradation effect increased with the increase of reaction temperature and decreased with the increase of p H value;The degradation effect of the composite was good at low H₂O₂ concentration.It was found that the composite could degrade more than 91.30%of MB in 10 minutes at the concentration of 0.02 mol/L H₂O₂;The reusability of Fe₃O₄/palygorskite composite was studied.It was found that under the reaction conditions of reaction temperature25℃,initial p H 6,reaction temperature 40℃,composite dosage 5g/L and[H₂O₂]=0.02mol/l,the degradation rate of MB could still be maintained above 86.44%.（4）The composite after reuse was comprehensively characterized.Through XRD study,it was found that the content of Fe₃O₄ in the reused material decreased,but its grain size increased;TOF and stem analysis found that the bonding tightness between palygorskite and Fe₃O₄ decreased after reuse,indicating that the service life of the composite is closely related to the bonding degree between palygorskite and Fe₃O₄;VSM analysis shows that the composites after repeated use for 10 times still have superparamagnetism.（5）Using the isothermal adsorption model,it is found that the adsorption process of palygorskite composite for methylene blue is in good agreement with Temkin isothermal adsorption model;The first-order and second-order kinetics of lagergren were combined and verified by azizian theory.It was found that the adsorption process well conforms to the first-order adsorption rate equation,and the diffusion in particles is not the only control step in the adsorption process.Thermodynamic studies show that the adsorption process is a spontaneous endothermic process,and increasing the temperature is conducive to the adsorption.（6）Through molecular dynamics simulation,the adsorption models of organic pollutant MB by magnetite and palygorskite were constructed respectively.It is found that on the（100）surface of palygorskite,MB can complete the adsorption in a very short time of<3ps and maintain the equilibrium state,and there is a certain amount of H₂O₂ on the palygorskite surface,which shows that palygorskite can greatly improve the contact opportunity between pollutants to be degraded and hydroxyl radicals in Fenton reaction,improve the utilization of H₂O₂ and enhance the degradation effect.Through theoretical discussion and experimental research,it is proved that Fe₃O₄/palygorskite is a composite catalytic material with low manufacturing cost,good catalytic effect,easy recovery and high reuse performance.