Preparation And Fenton-Like Properties Of Graphene-Based Transition Metal Co-Catalytic Composites

The environmental crisis is a major problem facing today’s society.The development of industrial civilization has led to the discharge of a large number of organic compounds into the water environment,resulting in increasingly serious water pollution.These pollutants are extremely toxic,non-degradable and bioaccumulative due to their large amount and wide range of pollution,which seriously affect the balance of ecosystem and human health and safety.The Fenton-like advanced oxidation technology based on sulfate radicals(SO₄^·-)has become a hot spot in the field of water treatment research in recent years,and the key lies in the selection of efficient catalytic materials.Graphene and its composites have been widely used as catalytic carriers,while the co-catalytic effect among transition metals can significantly enhance the water treatment effect.However,the practical application of catalysts still suffers from limited reactivity and difficult separation and recovery.In this study,three new transition metal co-catalytic materials were synthesized by loading modification of graphene.While maintaining its high Fenton-like catalytic activity,the separation and recycling capabilities was gradually improved,and the dissolution of transition metal was reduced.The structure of the composites was characterized and the Fenton-like degradation performance and meclianism of water organic pollutants were studied.The main conclusions are as follows:（1）A novel 3D α-FeOOH@MoS₂/rGO nanocomposite was fabricated by a simple in situ hydrothermal method.The catalysts before and after the reaction were analyzed by multiple characterizations,which confirmed the succccessful synthesis of the material and its structural stability.The introduction of rGO contributed to the uniform dispersion of a-FeOOH,and MoS₂/rGO hybrid could effectively solve the problem of material reunion,and the co-catalysis of MoS₂ accelerated the F3（Ⅲ）/Fe（Ⅱ）conversion.α-FeOOH@MoS₂/rGO activation of peroxymonosulfate（PMS）for rapid degradation of rhodamine B（RhB）,with 99.9%of RhB removed within 20 min,with a reaction rate constant of 0.19725 min^-1,and high removal efficiency and mineralization（>60%）for a variety of other organic pollutants.The electron paramagnetic resonance（EPR）and quenching experiments results verified that singlet oxygen（¹O₂）,superoxide radicals（·O₂^-）and SO₄^·-played a major role in the degradation of pollutants.In addition,the composite has excellent reusability,strong adaptability to the environment,and has good prospects for practical applications.（2）Co/Mo heterojunctions,flower-like MoS₂ nanosheets and monolayer GO nanosheets were successfully anchored on melamine sponges by impregnation pyrolysis to obtain 3D Co/Mo co-catalytic graphene sponges（SCMG）.3D melamine sponges as substrates provided a highly dispersed support for Co/Mo lieterojunctions and greatly facilitated the separation and recovery of catalysts.SCMG/PMS was able to remove 100%of RhB within 2 min,and it can also efficiently remove various dyes and antibiotic wastewater.The EPR and quenching experiments results verified that ¹O₂ and SO₄^·-were the main reactive oxygen species（ROS）involved in SCMG/PMS system,which contribute to a high efficiency over a wide pH range（3-9）and with the interference of co-existing ions.In addition,SCMG has good reusability and stability with metal leaching well below the existing safety standards over a wide pH range,indicating that this transition metal cobalt-molybdenum catalyst has good prospects for application in the environmental field.（3）A recoverable graphene oxide-supported 3D MoS₂/FeCo₂O₄ co-catalytic sponge（SFCMG）was synthesized by impregnation pyrolysis and in situ hydrothermal method.The three-dimensional graphene sponge served as a substrate to provide a highly dispersed carrier for FeCo₂O₄@MoS₂,which promoted the synergistic catalytic degradation of RhB.XPS confirmed the accelerated electron transfer between the bimetals and PMS by the introduction of GO.SFCMG/PMS could remove 95.0%and 100%of RhB within 2 min and 10 min,respectively,and ¹O₂ played a prominent role in RhB degradation.SFCMG/PMS showed efficient degradation performance and high stability over a wide pH range（3-9）,with 99.1%of RhB degraded after five cycles,and good degradation performance for many typical organic pollutants.The characterization results revealed that the synthesized Fe/Co bimetallic oxides not only have excellent co-catalytic ability,but also can limit the leaching of metals to a greater extent than SCMG.This study further extends the practical application of transition metal co-catalysis and provides an emerging class of Fenton-like catalysts for organic wastewater treatment.