Non-aqueous Synthesis And Catalytic Degradation Of Titanium Modified Fe₃O₄ Magnetic Particles

With the rapid development of modern industry,the problem of water pollution has become an urgent problem for many countries.Fenton reaction is a kind of advanced oxidation technology widely used in the degradation of organic pollutants.However,the homogeneous Fenton reaction still has the following difficult problems in practical application:narrow p H range??3?,effluent larger chromaticity and lower hydroxyl radical utilization rate increase processing costs.In order to solve the problems in the homogeneous Fenton reaction,many studies have used magnetite as heterogeneous Fenton reaction catalyst.We know that doping magnetite with Ti could improve the catalytic performance of magnetite,while ilmenite is a widely distributed magnetic mineral in nature.Titanium-modified Fe₃O₄ which is prepared by water as solvent,has the following problems:the p H requirement of the reaction system is less than 1 to prevent Ti⁴⁺hydrolysis;the equipment requirements are high,a large number of alkali is needed to neutralize the reaction system in the later stage,and the waste of raw materials is serious;most of the cationic dyes?such as methylene blue?are used as the target.Pollutants,but the degradation of anionic dyes,drugs and personal care products is rarely studied.Therefore,in this paper,Fe_3-xTi_xO₄were synthesized by ionothermal method and solid phase conversion method for the first time,and the degradation effect of the synthesized magnetic materials on various organic wastewater was studied.The main research contents are as follows:1.Titanium-modified Fe₃O₄ magnetic nanoparticles were synthesized in situ by ionothermal method,and a series of catalysts were synthesized by changing the amount of titanium modified.The optimum amount of titanium modified catalyst Fe_2.5Ti_0.5O₄was screened out.Fe_2.5Ti_0.5O₄ was synthesized by XRD,SEM,TEM,BET and XPS.The results showed that Ti modified Fe₃O₄ nanoparticles agglomerated with Fe₃O₄?cell parameter 0.838,particles size 15.7 nm?.Compared with the blank Fe₃O₄,the cell parameters and particle sizes of Fe_3-xTi_xO₄?cell parameters 0.840,particle size 28.0 nm?increased.Although the saturation magnetization of Fe_3-xTi_xO₄ decreased compared with the blank Fe₃O₄,magnetic separation was still possible.BET characterization showed that Fe_2.5Ti_0.5O₄ had a specific surface area close to that of Fe₃O₄-op-DES.XPS and Fe content measurements showed that Fe²⁺ions were concentrated on the surface of Fe_2.5Ti_0.5O₄ catalyst..2.Fe_2.5Ti_0.5O₄ was used to catalyze the decomposition of hydrogen peroxide to produce hydroxyl radicals to degrade different pollutants?MB,Rh B,OG,CIP and MNZ?.Fe_2.5Ti_0.5O₄ could decolorize methylene blue solution in 2 hours and remove COD by66%.Ti-modified Fe₃O₄ had better catalytic degradation effect than Ti-modified Fe₃O₄prepared in aqueous phase.At the same time,Fe_2.5Ti_0.5O₄ had the same cyclic degradation effect on five times of MB solution,and had high catalytic activity,good stability and high degradation salinity.At the same time,it was found that titanium modification could effectively improve the adsorption performance of Fe₃O₄ catalyst for cationic dyes,thus promoting the decolorization effect of cationic dyes.The data of decomposition of hydrogen peroxide show that the pre-exponential factor of decomposition of hydrogen peroxide by Fe_2.5Ti_0.5O₄ is much lower than that of Fe₃O₄,which indicates that Ti modification reduces the collision frequency between hydrogen peroxide and catalyst surface,but Ti modification reduces the activation energy of decomposition of hydrogen peroxide by Fe₃O₄ from 62.07 k J·mol^-1 to 54.32 k J·mol^-1,indicating that titanium modification introduces new active sites on the surface of Fe₃O₄nanoparticles.Fe_2.5Ti_0.5O₄ also had good degradation ability to Rh B and CIP,but had poor or no degradation ability to anionic dyes?OG?and non-adsorbable antibiotics?MNZ?.3.In order to improve the catalytic degradation of MNZ by Ti-modified Fe₃O₄particles,metal ions?Cu,Al?and small organic molecules?epichlorohydrin and taurine?were used to further modify the surface of Fe_3-xTi_xO₄ magnetic particles.It was found that metal ions?Cu,Al?modified Fe_3-xTi_xO₄ could slightly improve the catalytic degradation of metronidazole,but the degradation effect was still limit.Fe_3-xTi_xO₄modified with taurine had certain degradation effect on metronidazole,but had no cyclic performance,while ECH modified Fe_3-xTi_xO₄ had no degradation ability on metronidazole.4.In order to prepare the catalysts for degradation of metronidazole with high catalytic activity and good cycling performance,we designed a new method of preparing Fe_3-xTi_xO₄ in non-aqueous phase system.Firstly,Ti modified Fe OOH was synthesized.Then,high temperature calcination and reduction of glucose in N₂ atmosphere were used.Fe_3-xTi_xO₄-ST was successfully synthesized by solid-phase conversion method.It was applied to degradation of metronidazole.The results showed that Fe_3-xTi_xO₄-ST synthesized by solid-phase conversion method has good catalytic degradation effect on metronidazole.Recycling experiments show that the synthesized catalyst has good reusability.Ti modification reduces the activation energy of decomposition of hydrogen peroxide by Fe₃O₄ from 39.14 k J·mol^-1 to 23.67 k J·mol^-1,indicating that titanium modification introduces new active sites on the surface of Fe₃O₄ nanoparticles.Compared with the samples prepared by ionothermal method,the activation energy of decomposition of hydrogen peroxide by Fe_3-xTi_xO₄ prepared by solid-phase conversion method was reduced from 54.32 k J·mol^-1 to 23.67 k J·mol^-1,indicating that the surface of particles prepared by solid-phase conversion method had more active sites.