The Efficiency And Mechanism Of 2,4 Dichlorophenol Degradation In Water By Catalyzed PMS With Alkylglycoside Modified MnFe₂O₄

With the rapid development of industrial production,dyes,drugs,pesticides and other industrial products have emerged in large quantities,resulting in the release of more and more 2,4-dichlorophenol（2,4-DCP）into the water environment and soil environment.2,4-DCP is an important organic chemical intermediate product,mainly used in the production of pesticides,herbicides,pharmaceuticals and other products.Due to its stable molecular structure,poor biodegradability,and bio aggregation,it is easy to be left behind for a long time.Therefore,it has been recognized as an environmental priority organic pollutant in many countries,such as the United States and China.However,it is difficult to completely degrade 2,4-DCP through traditional treatment methods.Therefore,it is urgent to explore an effective 2,4-DCP treatment technique.A novel mesoporous Alkylpolyglycoside（APG）coated Mn Fe₂O₄ nano-composites（APG@Mn Fe₂O₄）with abundant surface oxygen vacancies（VOs）was successfully developed via a facile co-precipitation method and utilized as a peroxymonosulfate（PMS）activator for 2,4-Dichlorophenol（2,4-DCP）degradation.The synthetic mechanism,physical and chemical properties and synthetic mechanism of the material were studied by a series of characterization methods.The catalytic performance of APG@Mn Fe₂O₄ on PMS was evaluated by 2,4-DCP degradation experiment,and the influencing factors in the degradation process were studied.In addition,the degradation mechanism and degradation pathway of 2,4-DCP in APG@Mn Fe₂O₄/PMS system were further revealed through the identification of free radicals and the analysis of intermediate products.The main research achievement of this study is proposed:（1）Magnetic mesoporous APG@Mn Fe₂O₄ nanoparticles rich in vacancy oxygen were synthesized by co-precipitation method.XRD and EDS and analysis proved the successful preparation of spinel structure Mn Fe₂O₄.FT-TR and TGA analysis proved the successful combination of APG and Mn Fe₂O₄,and roughly calculated the APG load was about 14%.The results of N₂ adsorption desorption test and magnetic test showed that APG@Mn Fe₂O₄ was a typical mesoporous structure and had good magnetic properties.Through cyclic voltammetry curve and Nyquist curve analysis,APG@Mn Fe2O4 has a stronger REDOX ability than pure Mn Fe₂O₄.According to SEM,TEM images,APG@Mn Fe₂O₄ single particles are spherical and it is a typical core-shell structure,the particles do not aggregate,and the particle size is between50nm-150nm.The XPS spectrum analysis of O 1s before and after APG loading,as well as solid state EPR test,Raman test and others proved that APG@Mn Fe₂O₄ has a higher content of vacant oxygen.（2）The degradation of 2,4-DCP was studied by using APG@Mn Fe2O4 as the catalyst of PMS.Under the same conditions,the degradation efficiency of 2,4-DCP in APG@Mn Fe₂O₄/PMS system was 93%.However,the degradation efficiency in Mn Fe₂O₄/PMS system was only 32%,indicating that the prepared APG@Mn Fe₂O₄ has higher catalytic activity.In the process of the reaction,the initial p H of the reaction system and some common anions have no obvious inhibitory effect on the degradation process,and the removal efficiency is relatively high in different water environments.Moreover,after three cycles of recycling,the degradation efficiency of 2,4-DCP can still reach 90%.Under optimal conditions,TOC removal rate of 2,4-DCP was up to73%,and the products during degradation were analyzed.Under the same conditions,the removal efficiency of APG@Mn Fe₂O₄/PMS system was 95.5%,98.8%,92.3%and97.0%,respectively,for Bisphenol A,Sulfanilic acid,Rhodamine B and Orange G.The above results indicate that APG@Mn Fe₂O₄ has excellent catalytic performance as a new type of environmentally friendly catalyst.（3）The catalytic mechanism of PMS by APG@Mn Fe₂O₄ was explored through quenching experiments and identification of free radicals.The results shown that in APG@Mn Fe₂O₄/PMS system,singlet oxygen,rather than hydroxyl radical and sulfate radical,played a major role in oxidation.Furthermore,the degradation of 2,4-DCP was mainly caused by the non-free radical pathway dominated by singlet oxygen,which was caused by the abundant oxygen vacancy on the catalyst surface.Combined with XPS analysis before and after the reaction,the degradation mechanism of 2,4-DCP was summarized as follows:it can be divided into two parts:one is the non-free radical pathway dominated by VO/PMS;the other is the free radical pathway dominated by Fe/Mn/PMS,while the non-free radical pathway plays a more important role.