Microwave Catalytic Degradation Of Bisphenol A By Si C Supported Composite Metal Oxides

Bisphenol A is A class of endocrine disruptors that are difficult to degrade.It is A kind of Pharmaceutical and personal care products（PPCPs）.When it enters the human body,it can cause endocrine disorders and interfere with the normal development of the human body.It can also pose a serious threat to the health of fetuses and children.In recent years,the pollution of bisphenol A is becoming more and more serious,and its treatment is imminent.Microwave oxidation technology,as a new advanced oxidation technology,has the advantages of simple operation,fast reaction rate,strong degradation ability and high mineralization rate,and is often used to treat high concentration and difficult to degrade organic pollutants.However,the effect of oxidation degradation of pollutants depends on the matching between the catalyst and the microwave field and the stability of the catalyst.Therefore,it is crucial to select the appropriate catalyst.In this paper,three kinds of microwave catalysts,NiFe₂O₄/Si C、NiCo₂O₄and NiCo₂O₄/Si C,were prepared and applied to microwave oxidation of bisphenol A.The main research contents and obtained results are as follows:（1）NiFe₂O₄/Si C is a granular mesoporous material with a specific surface area of211.434 m²/g and a pore volume of 0.442 cm³/g.The degradation of bisphenol A by microwave-assisted Fenton method was studied.The results showed that under the optimal reaction conditions（bisphenol A solution 20 mg/L,p H=3,NiFe₂O₄/Si C（40%）dosage 4 g/L,H₂O₂concentration 3 m L/L,microwave power 400 W）and reaction time 8 min,the degradation rate of bisphenol A reached 100%and the mineralization rate was 64%.After being recycled for five times,the degradation rate of bisphenol A still reached 100%,and the dissolution rate of metal ions was only 0.7 mg/L,which indicated that the material had good stability.（2）Sea urchin-like NiCo₂O₄hollow pellets are also mesoporous materials,with a specific surface area of 106.362 m²/g and a pore volume of 0.352 cm³/g.Using it as catalyst,the performance of microwave oxidation degradation of bisphenol A was studied.The results showed that under the optimal reaction conditions（bisphenol A solution 20 mg/L,p H=3,NiCO₂O₄dosage 0.5 g/L,microwave power 300 W）,the degradation rate of bisphenol A reached 100%and the mineralization rate was60.29%under 8 min reaction.After the catalyst was recycled for five times,the degradation rate of bisphenol A was reduced to 50%,and the dissolution rate of metal Co ions was as high as 16.2 mg/L,indicating that the material had poor stability.（3）In order to enhance the stability of NiCo₂O₄,the catalyst NiCo₂O₄/Si C was prepared by loading it on Si C.NiCo₂O₄/Si C is also a mesoporous material with a specific surface area of 45.920 m²/g and a pore volume of 0.185 m³/g.The degradation of bisphenol A by catalytic oxidation under microwave was studied.The results showed that under the optimal reaction conditions（bisphenol A solution 20 mg/L,p H=3,NiCo₂O₄/Si C（60%）dosage 1.5 g/L,microwave power 300 W）,reaction for 8min,the degradation rate of bisphenol A reached 100%,and the mineralization rate was 72%.After the catalyst was recycled for five times,the degradation rate of bisphenol A was still up to 91%,and the dissolution rates of Co and Niions were 1.9mg/L and 0.9 mg/L,respectively,which indicated that the material had good stability.（4）With NiFe₂O₄/Si C as the catalyst,the oxidizing agent hydrogen peroxide is needed to efficiently degrade bisphenol A,which belongs to microwave-assisted Fenton method.Based on the results of free radical scavenging experiments,the mechanism of microwave-assisted Fenton reaction was speculated as follows.When the catalyst is irradiated by microwave,NiO on the catalyst absorbs microwaves and generates hole-electron pairs under the induction of microwave.At the same time,Fe²⁺on the catalyst reacts with H₂O₂through Fenton to form·OH and Fe³⁺.Under the action of·OH radical and some holes,bisphenol A was oxidized and degraded.Fe³⁺generated by the Fenton reaction captures microwave-induced electrons and regenerates Fe²⁺to ensure the cycle between Fe²⁺and Fe³⁺.（5）With NiCo₂O₄and NiCo₂O₄/Si C as catalysts,Bisphenol A can be highly oxidized and degraded without additional oxidants,which belongs to microwave catalytic oxidation method;Based on the results of free radical scavenging experiments,it is speculated that the reaction mechanism of microwave catalytic oxidation is:When subjected to microwave radiation,NiCo₂O₄composite metal oxide absorbs microwave and excites to generate hole-electron pairs.The hole（h⁺）has a strong oxidation ability,and oxidizes H₂O to form·OH radical.The electrons（e^-）will initially dissolve with oxygen in water to form O₂^·-radicals,which are unstable O₂^·-and chemically convert to·OH and O₂^·-.Under the combined action of·OH radical,hole and O₂^·-,bisphenol A was oxidized and degraded.