Preparation Of Highly Stable Cu-Fe@Biochar Composite And The Photo-fenton Catalytic Performance

A large quantity of industrial wastewater is discharged as the rapid development of industrialization,which poses a serious threat to the environment and human health.The dye wastewater has the characteristics of large discharge,wide variety,and stable structure.Nitrobenzene is a kind of essential aromatic compounds in industry.The nitrobenzene wastewater is highly toxic and difficult to be degraded.Therefore,the key of the research is to explore a kind of catalyst with simple and green preparation technology,excellent catalytic performance,and good stability to treat various organic wastewater.This thesis proposed the use of mechanical activation（MA）for the pretreatment of precursor materials（cellulose and metal salts）,contributing to a stable combination of cellulose and metal salts,and a highly stable MA-pretreated biochar-supported Cu-Fe composite（MA-Cu-Fe@C）was prepared by a one-step calcination method.MA-Fe@C and MA-Cu@C composites were prepared by the same method.Moreover,Cu-Fe@C composite without MA pretreatment was also prepared.Photo-Fenton catalytic degradation of methylene blue（MB）and nitrobenzene by different composites was comparatively studied,and the mechanism of improving the catalytic performance and stability of the composites by MA pretreatment were explored.The main research contents and results are as follows:（1）Using bagasse cellulose,copper chloride,and ferric nitrate as raw materials,the precursor materials were pretreated by MA for the preparation of MA-Cu-Fe@C,MA-Fe@C,and MA-Cu@C composites by one-step calcination.Additionally,the precursor materials were pretreated by a simple mixing method to prepare Cu-Fe@C.XRD,SEM,TEM,FTIR,XPS,VSM,and specific surface area and porosity analysis were used to investigate the effect of MA pretreatment on the structure and properties of the composites.The results show that a strong interaction was formed between cellulose and metal salts induced by MA pretreatment,and the metal-based components formed by calcination were uniformly and closely bonded and stably loaded on the biochar.The MA-Cu-Fe@C composite had a large specific surface area(221.02 m²·g^-1)and a small average pore size（4.47 nm）,with a saturation magnetization of 82.5emu·g^-1.MA pretreatment changed the surface chemical bonds and electronegativity of the cellulose,leading to a smaller isoelectric point（6.7）of the MA-Cu-Fe@C composite.（2）The photo-Fenton catalytic performance of different composites for the degradation of MB and the mechanism of enhancing the catalytic activity and stability of the composites by MA were studied.The results show that MA-Cu-Fe@C exhibited excellent catalytic activity and cycling stability.Under the optimal conditions of catalyst dosage of 0.5 g·L^-1,p H=5,and H₂O₂dosage of32 m M,the degradation rates of MB catalyzed by MA-Cu-Fe@C and Cu-Fe@C were 98.8%and 75%,respectively,and the mineralization rates were 73.7%and61.2%,respectively.The degradation rate of MB catalyzed by MA-Cu-Fe@C was still more than 96.0%after 20 cycles,while the that catalyzed by Cu-Fe@C was less than 5.0%after the second cycle.Cu（I）/Cu（II）and Fe（II）/Fe（III）jointly stimulated H₂O₂to produce·OH under visible light.The stable anchoring of active components reduced the leaching of metal-based components,resulting in the improvement of the catalytic activity and stability of the composites.（3）The photo-Fenton catalytic degradation of nitrobenzene by MA-Cu-Fe@C composite was studied.The effects of initial concentration of nitrobenzene,initial p H of solution,amount of catalyst,and concentration of H₂O₂on nitrobenzene removal were investigated.The mineralization rate of nitrobenzene and the structural changes in the degradation process were analyzed.The results show that the optimal reaction conditions were as follows:initial concentration of nitrobenzene of 50 mg·L^-1,initial p H=7,dosage of catalyst of 0.5 g·L^-1,and concentration of H₂O₂of 64 m M.The degradation rate of nitrobenzene could reach 91.1%,and the by-product of degradation is aniline,which was conducive to further deep degradation.In conclusion,MA-Cu-Fe@C composite exhibited high catalytic activity and recycling stability,which has a broad application prospect in the treatment of organic pollutant wastewater.