Study On The Degradation Of Acetaminophen By Catalyzing PMS With MnFe₂O₄ And Its Mineral Composite Catalytic Materials

Acetaminophen（ACE）,as a typical pharmaceutical and personal care product（PPCPs）,poses a serious threat to water environment due to its large dosage and difficult degradation.Advanced oxidation processes（AOPs）have emerged as a new technology to effectively remove refractory organic pollutants in water.Among them,the AOPs based on peroxymonosulfate（PMS）have broad application prospects in treating PPCPs wastewater due to their strong oxidizing properties,wide adaptability to p H range,and reaction stability.Transition metal heterogeneous activation of PMS is a commonly researched method.Therefore,finding a catalyst with strong catalytic activity,stable structure,and low cost became the key to promoting the accelerated application of PMS advanced oxidation technology.Based on the idea of preparing and regulating the properties of bimetallic composite catalysts,this study selected Fe and Mn as the active components to prepare Mn Fe₂O₄ bimetallic catalysts and constructed a composite catalyst（D-Mn Fe）by introducing diatomite as the carrier to enhance the catalyst activity and stability.With ACE as the target pollutant,the study investigated the effects of preparation conditions and various factors on the degradation of ACE by non-homogeneous PMS activation of Mn Fe₂O₄ and D&Mn Fe,and systematically studied the degradation characteristics,influencing factors and action mechanism in the catalytic oxidation system.The main contents and conclusions of this study are as follows:（1）Mn Fe₂O₄ and D-Mn Fe catalysts of two types were prepared by the sol-gel method,and the catalytic performance of different systems was compared.When the dosage of PMS/Mn Fe₂O₄（350℃）catalyst was 0.5 g/L,the dosage of PMS was 0.3 g/L,and the temperature was 25℃,the degradation rate of ACE was 77.67%.However,the degradation rate of PMS/D-Mn Fe-50%reached 98.42%,and the degradation reaction followed the composite pseudo-first-order kinetic model.（2）SEM,XRD,XPS,and FT-IR characterization methods were used to analyze the morphology changes and crystallization of the two catalysts.It was found that Mn Fe₂O₄conformed to the spinel-type crystal structure with an average grain size of about 11.07nm,and the material showed a nanoparticle shape with agglomeration phenomenon at the micro-level.D-Mn Fe-50%well-preserved the crystal structure and functional groups of diatomite and Mn Fe₂O₄,Mn Fe₂O₄ particles were uniformly attached to the diatomite,which can expose more active sites to enhance the catalyst activity and alleviate the problem of active site coverage caused by agglomeration.Fe and Mn existed in the form of divalent and trivalent in both materials.（3）The degradation rate of PMS/Mn Fe₂O₄ system was higher than 72.22%within the p H range of 5～9,and the degradation rate was poor under strong acid（p H=3）and strong alkali（p H=11）conditions.The PMS/D-Mn Fe-50%system had a wider p H range,and ACE could be efficiently degraded（degradation rate higher than 97.14%）within p H=3～9.Coexisting anions Cl^-,HCO₃^-,H₂PO₄^-and macromolecular organic matter humic acid in the water had an inhibitory effect on the degradation of ACE by PMS/D-Mn Fe-50%.Mn Fe₂O₄ showed a degradation rate decrease of 55.48%after four cycles of use,and there was a problem of high metal ion leaching（Mn leaching 1.728 mg/L,Fe leaching 0.329 mg/L）.D&Mn Fe-50%had good repeatability,and the degradation rate was still 81.80%after four cycles of use.The addition of diatomite carrier improved the material stability and reduced the leaching of metal ions（Mn leaching 0.658 mg/L,Fe leaching 0.208 mg/L）,which enhanced the catalyst activity while reducing secondary pollution and resource waste.（4）Mechanism analysis showed that SO₄^-·,·OH,¹O₂,and·O₂^-were the main active species in the PMS/D-Mn Fe-50%system.Among them,SO₄^-·,·OH,and ¹O₂ played a dominant role in the degradation process of ACE.The synergistic effect between Fe and Mn made the catalyst have good recyclability and catalytic performance.Moreover,there were multiple interaction mechanisms between D&Mn Fe-50%and PMS,which helped to enhance the catalytic effect.