Efficiency And Mechanism Of Manganese-based Bimetallic Minerals In Catalytic Oxidation Of Organic Pollutants

In recent years,the rural water and soil environment have suffered serious organic pollution,posing a potential threat to the ecological security of green water and pure soil.The degradation of organic pollutants by transition metal catalytic oxidation has received extensive attention.Unfortunately,in the process of degrading organic pollutants by transition metal catalysts,the redox cycle between high and low valence metal elements cannot be successfully achieved.The high valence metal elements,accumulation would inhibit its efficient and sustainable catalytic ability.In this study,three manganese-based bimetallic catalysts were synthesized,and three efficient degradation systems for organic pollutants were established as manganese-iron bimetallic oxide/PMS,manganese-iron bimetallic selenide/PMS,and manganese-cobalt bimetallic selenide/H₂O₂.For catalyst characterization,activation ability analysis,degradation performance evaluation,influence of reaction conditions,active species identification,catalyst stability evaluation,etc.,the reaction process and mechanism of catalytic oxidation of manganese-based bimetallic minerals were analyzed in detail.Strategies such as metal vacancies significantly increase the redox cycle rate between high and low valence states of transition metals,showing efficient and sustained catalytic activation.The main research contents are as follows.（1）Study on the activation of PMS by ferromanganese bimetallic oxides.The Mn Fe₂O₄/PMS/ascorbic acid（AA）system can efficiently remove methylene blue（MB）.The experiment shows that AA plays a very important role in the removal of MB.By tracking the concentration of PMS and AA in the reaction and adding experiments,it was found that the system maintained a high-efficiency degradation state in the presence of AA.The role of AA is to accelerate the reduction of Fe/Mn（III）on Mn Fe₂O₄ and help the dissolution of Fe/Mn（II）,form a Fe/Mn cycle between the heterogeneous interface and the homogeneous interface of the catalyst,and improve the adsorption capacity of oxygen on the catalyst surface.active,produce abundant ¹O₂,and achieve efficient degradation.（2）Study on the activation of PMS by ferromanganese bimetallic selenides.The elemental conversion efficiency of Mn Fe Se₃ is higher than the Mn Fe₂O₄/PMS system.This study focuses on the role of non-metallic components in the heterogeneous catalytic oxidation process.The high catalytic efficiency of Mn Fe Se₃ is attributed to the efficient cycling of Mn/Fe/Se elements between oxidized and reduced states during the reaction,and Se acts as a non-metallic element,which accelerates the circulation between metal elements.The degradation of pollutants is achieved by SO₄^-·、·OH generated on the catalyst surface and·OH in solution.（3）Activation of H₂O₂ by manganese-cobalt bimetallic selenides.The Mn_0.5Co_0.5Se composite exhibits the best catalytic performance,showing high reusability and stability over 5 cycles.The results of response surface methodology showed that the optimal conditions for removing target pollutants were catalyst dosage of 0.1 g/L,H₂O₂ concentration of 2.6 m M,and initial p H of 6.98.The degradation rate of contaminants during the reaction time was 98%.The degradation processes of pollutants include non-radical processes（based on ¹O₂）and free radical processes（based on·OH and·O₂^-）.Se vacancies on the surface of Mn_xCo_1-xSe were identified,and it was found that Se vacancies played an important role in the generation of non-radical ¹O₂.In conclusion,this study provides a new idea for the catalytic oxidation of organic pollutants in water by manganese-based bimetallic minerals.