Study On Microwave Enhancement Modification Of Foamed Metal And Its Application In Wastewater Treatment

More and more attention has been paid to microwave thermal utilization technology with the deepening understanding of microwave.Microwave heating technology is widely used in organic wastewater treatment,solid waste treatment,metallurgy,food processing,traditional Chinese medicine extraction and petrochemical industry nowadays.Microwave heating is a process that substance absorbs and dissipates the microwave energy.Compared with the traditional heating method,microwave heating is faster in heating speed,higher in heating efficiency and more flexible in heating ways.Due to the selective heating characteristics,many researches have shown that in the process of using microwave heating to treat materials,the processing effect will be strengthened and the corresponding treatment efficiency will be improved if the material has strong microwave absorptivity.Therefore,the key to enhance the effect of microwave heating is the selection of strong microwave absorbing materials.However,microwave absorbing materials that commonly used at present,such as iron oxide(Fe2O3)and activated carbon(AC),are mostly powdery materials,whichare easy to agglomerate,difficult to recycle and easy to be wasted.Other catalyst carriers,such as aluminium trioxide(Al2O3)and titanium dioxide(TiO2),are low in microwave absorptivity.Therefore,the development of composited microwave absorbing materials with high absorptivity and high recovery efficiency is of great significance to promote the application of microwave heating technology.This research takes nickel foam(NF)as the substrate,combining nano materials with different microwave loss mechanisms to prepare barium titanate modified nickel foam(BTO-NF)and multi-walled carbon nanotubes modified nickel foam(MWCNTs-NF)composite to strengthen microwave absorptivity.Heat generation characteristics of different materials were studied through microwave calorimetry and the microwave absorptivity coupling mechanisms of composited materials were explored.Composited material(BTO-NF?MWCNTs-NF)were conducted to remove the total organic carbon in P-nitrophenol(P-NP)organic wastewater to explore the practical value of composite materials.Firstly,the nano barium titanate(BTO)and multi-walled carbon nanotubes(MWCNTs)were loaded onto the NF substrate through electrophoretic deposition methods.Meanwhile,SEM,XRD and FT-IR were used to explore the effects of different source voltage,concentration of electrophoretic solution and electrophoretic deposition time on deposition volume and deposition morphology during electrophoretic deposition process.The experimental results showed that the BTO-NF composite absorbing material has the best deposition morphology and the most excellent deposition mass(35.3%)under voltage of 70V and concentration of 15mg/ml with the electrophoretic deposition time of 10min.MWCNTs-NF has the most deposition mass(8%)and the best deposition morphology under voltage of 80V and concentration of 0.25mg/ml with the electrophoretic deposition time of 30 min.Secondly,on the basis of the best electrophoretic deposition experimental conditions,microwave calorimetry was used to measure the microwave heat generation characteristics of NF,BTO,MWCNTs,BTO-NF and MWCNTs-NF.Besides,the microwave heating performance of composite materials and single absorbing materials was compared.The results revealed that under the conditions of BTO and MWCNTs loading ratios of 35.3%and 8%,the microwave heating performance per unit mass of BTO-NF and MWCNTs-NF were increased by 33.3%and 53.7%than that of NF,respectively.It was found that the heat generation ability of composite materials was not a simple addition effect of single material according to load ratio,but there was a new additional microwave absorbing coupling channels formed,thus the heating performance of composite materials was enhancedFinally,BTO-NF and MWCNTs-NF were conducted to microwave-assisted total organic carbon removal in P-nitrophenol.Total organic carbon analyser(TOC)was used to detect the removal efficiency of total organic carbon.Effect of experimental conditions,such as type of microwave absorbing materials,microwave irridation time,microwave power and oxidant dosage,were explored.Results showed that when the concentration of P-nitrophenol was 100 mg/L,treatment time was 300 seconds,hydrogen peroxide(H2O2)dosage was 3ml/L and microwave power was 1000W,the removal rates of total organic carbon by BTO-NF(3g/L)was 98.0%.The removal efficiency was 62.0%,40.1%and 18.7%higher than adding no microwave absorbing materials,respectively.As for MWCNTs-NF,the removal efficiency of total organic carbon by MWCNTs-NF(1g/L)was 96.1%when the concentration of P-nitrophenol was 100 mg/L,treatment time was 300 seconds,hydrogen peroxide(H2O2)dosage was 2ml/L and microwave power was 1000W.The removal efficiency of MWCNTs-NF was 62%higher than adding no microwave-absorbing materials,16.8.%higher than adding NF alone and 30.9%higher than adding MWCNTs alone,respectively.The research focused on developing composite materials with strong microwave absorptivity and high recycling performance.The multi-layer composite absorbing materials prepared in this paper strengthen the microwave absorptivity of the matrix materials and the modified materials,solving the shortcomings of the modified nano materials which are difficult to recycle.They have great application prospects.The composite materials were applied to wastewater treatment,and its treatment efficiency was better than that of single material.Furthermore,there is no secondary pollution produced in the treatment process,and it is convenient and efficient,which contributed toits practical application.