Microwave-induced Catalytic Degradation Of Dye Wastewater Using Magnetic Composites

Dyes have complex composition,stable properties,and high chemical oxygen consumption,and their disposal have always been a difficult problem in wastewater treatment.Microwave-induced catalytic oxidation technology has been widely investigated in dye wastewater treatment.In this study,nano magnetic composites was prepared as catalysts using in microwave-induced catalytic degradation process by combining materials of different microwave loss mechanism,which could absorb microwave strongly.Microwave?MW?combined with different magnetic composite was developed to explore operational parameters that would influence the degradation of the dye wastewater by the experimental studies,the aim of which is to find an efficient and rapid method for decolorization of dyes.Firstly,NaBH₄ reduction method was used to prepare nano zero-valent iron?nZVI?particles.With methyl orange as the target pollutant in the experiment,the degradation efficiency of the dye was analyzed by changing the dosage amount of nano zero-valent iron?nZVI?powder and the microwave power at the initial pH = 7 and I=0.1.Kinetic studies suggested that the degradation process could be described by the exponential decay kinetic model.In this study,it was shown that dyes can be rapidly and effectively removed by MW-nZVI.Then,nZVI was loaded on graphene in order to improve the aggregation phenomenon of nZVI,and the as-prepared graphene/nZVI composite was used as catalyst to study the degradation of methyl orange under microwave induced catalytic oxidation.The degradation experiments of methyl orange under different experimental conditions such as the initial dye concentration of methyl orange,dosage of catalyst,microwave power and time,were carried out systematically to study the degradation of methyl orange under microwave irradiation.The degradation efficiency of methyl orange could reach 98.1%for 50 mg/L methyl orange,catalyst dosage of 3 g/L,and 750 W microwave irradiation.All the results show that the removal efficiency of methyl orange was improved with the increase of catalyst dosage and microwave power,but decreased with increasing the initial concentration of methyl orange.Finally,coal fly ash/CoFe₂O₄?CFA/CFO?magnetic composite was prepared by hydrothermal synthesis method and was used as catalyst to degrade malachite green under microwave irradiation.Kinds of characterization methods such as XRF,SEM,XRD,FTIR,BET and VSM were used to observe the morphology,structure and property of the samples.Batch studies were conducted to evaluate the removal efficiency of the dye by changing the dosage amount of CFA/CFO composite,the microwave power and irradiation time at the initial pH = 7 and I=0.1,The removal dye efficiency could reach 96.7%with CFA/CFO dosage amount of 2 g/L and microwave power 720 W.Microwave heating does not rely on heat conduction from the surface to inside of materials,and could absorb and convert microwave energy to heat.Moreover,microwave could induce the temperature of microwave absorber to increase rapidly,producing active oxygen species which possess strong oxidizing property and promoting chemical reaction as a result.In conclusion,this study offered an efficient and economic method for the disposal of dye wastewater and also provided a technology to solve the catalyst recovery problem with no secondary pollution.And hence,it is a promising technology for the treatment of dye wastewater and would bring some benefits for engineering application.