Performance And Mechanism Of Complex OMS-2 Catalysts Activated PMS For Degradation Of Acid Orange 7

Sulfate radical-based advanced oxidation process is a high efficient method to treat printing and dyeing wastewater,which have attracted extensive attention lately.As a transition metal element that can activate persulfate,manganese is abundantly stored in the natural world.It is a valence metal that fluctuates in the range of+2 to+7.The manganese oxide octahedral molecular sieve（OMS-2）has a unique pore structure,a multivalent valence state,and a large specific surface area.After long-term research,it was found that OMS-2 not only has a good pore structure but also has good environmental properties and is a natural carrier and catalyst.However,the activity of OMS-2 for peroxymonosulfate（PMS）was greatly influenced by pH.In order to solve this deficiency,the regulation of the valence state of OMS-2 has gradually become a trend and research hotspot in recent years,aiming at increasing the adaptability to different pH and using in a wider range area.In this study,the porous structure of manganese octahedron molecular sieves（OMS-2）was used as the support,and the non-metal carbonitrides（g-C₃N₄）,graphite（Gt）and copper oxide（CuO）were used as active materials,respectively.Persulfate（PMS）was as an oxidant and Acid orange 7（AO7）was as target degradation product.The detailed works were as follows:1.A complex OMS-2/CN catalyst was prepared by a simple reflux method.Based on the synthesis process of the catalysts,it was found that the high-valence manganese elements reacted with the lower manganese elements at first,and then react with highly reducing g-C3N4.After the reaction,the performance of g-C3N4 changed and the catalytic efficiency of the composite catalyst increased.2.Synthesizing OMS-2/Gt catalysts by adjusting the ratio of OMS-2 to Gt,a catalyst with higher catalytic efficiency is obtained.The ratio of Mn³⁺/Mn⁴⁺is introduced to find out the intrinsic influence of the valence of manganese on the composite catalyst.The analysis shows that the low-valent manganese element has a dominant influence on the activity of catalysts,which was further confirmed by experiments.Thus,the reason for the increasing activity of the OMS-2/Gt catalyst reasoned from the increase in the proportion of Mn³⁺.3.The multi-metal oxide CuO/OMS-2 catalyst was prepared by combined reflux and ignition.The specific surface area of OMS-2 increased first and then decreased with the increase of CuO loading,and the catalytic activity also showed a similar pattern.A synergistic effect was observed between the metal oxide CuO and the carrier OMS-2.Electron paramagnetic resonance（EPR）was used to capture the active material in the reaction system.The results showed that sulfate radicals(SO4^-·)were generated,and a small amount of hydroxyl radicals（·OH）were also generated in the system.In this paper,three representative complex catalysts were synthesized to study the adjusted valence of the supports by the carriers and the direct effect on PMS activation.Thus,the experimental parts of this paper are refined into three major chapters,and morphology,crystal structure,specific surface area and element existence state of catalysts are described in detail,comparisons are made between OMS-2 in the structure.The practices of composite catalysts activating PMS not only provide a new idea for the transition metal activated persulfate,but also broaden the direction application of OMS-2 in the related fields.