Study On Treatment Of Rhodamine B Simulated Wastewater By Heterogeneous Metal Catalyst In Electro-Fenton System

With the development of the printing and dyeing industry,the composition of printing and dyeing wastewater is more complicated,and the total amount of the wastewater is also increasing.It has become an urgent problem to degradate the printing and dyeing wastewater for environmental protection purpose.Heterogeneous electro-Fenton technology has become an important process for the treatment of the printing and dyeing wastewater because it overcomes the problems of narrow operation pH value,large amount of iron mud generation in the traditional Fenton process and high efficiency in the treatment of refractory wastewater.In order to investigate the optimum operating conditions and multi-metal synergy mechanism of heterogeneous metal catalysts in the treatment of printing and dyeing wastewater by electro-Fenton,the catalyst of iron and manganese loaded on MCM-41,a mesoporous material containing aluminum,was synthesized by the method of co-precipitation.The prepared catalyst was characterized by the methods of TEM,XRD,BET,and XPS.The prepared catalyst was applied to the treatment of Rhodamine B simulated wastewater in electro-Fenton system with carbon felt as cathode and platinum wire as anode.The optimal operation conditions of the electro-Fenton process were investigated.The degradation kinetics of Rhodamine B and the degradation mechanism were also studied.The conclusions are as follows:（1）Four kinds of heterogeneous catalysts of MCM-41（donated as G1）,Mn-MCM-41（donated as G2）,Fe-Mn-MCM-41（donated as G3）,and Fe-Mn/Al-MCM-41（donated as G4）were prepared by a co-precipitation method.The catalytic activity of G4 was found to be the highest by comparison.The single factor experiment showed that the optimal calcination temperature of G4 was 550℃,the calcination time was 6 h,the ratio of iron-manganese metal ions was 1:1,and the dosage of iron-manganese metal ions was 0.018 mol/L.The catalysts were characterized by XRD,BET,TEM,and XPS.It was found that all the prepraed catalysts maintained good mesoporous structure and the supported metal ions were highly dispersed on the catalyst surface.The Catalyst of G4 was repeatedly for 3^rdd times and the results showed that the removal rate of rhodamine B were all maintained above 90%.After degradation,the amount of Fe and Mn ions leaching was less than 0.18 mg/L and 0.6017 mg/L.（2）In the electro-Fenton system with carbon felt as the cathode and platinum wire as the anode,the catalyst of G4 was added,and the optimal operation conditions of the electro-Fenton system were obtained by single factor experiment.The initial concentration of Rhodamine B is 10 mg/L,pH=5,oxygen flow rate is 0.3 L/min,the voltage is 8 V,the electrolyte concentration（Na₂SO₄）is 0.1 mol/L,and the catalyst dosage is 0.5 g/L.The results showed that the synergistic effect of adsorption,electrochemical oxidation and Fenton oxidation is primarily responsible for the high degradation efficiency of Rhodamine B in the electro-Fenton catalytic oxidation process.The degradation efficiency of Rhodamine B and TOC of the simulated wastewater under the optimal treatment conditions were determined to reach 99.6%and 60%after 3 hours of treatment.（3）The degradation mechanism of rhodamine B in the heterogeneous electro-Fenton system was investigated,and the reaction kinetics of heterogeneous catalyst of G4 for catalytic oxidation was also studied.The comparative experiments confirmed that the active matters in the heterogeneous electro-Fenton system is·OH;The kinetic study on the degradation of Rhodamine B was carried out by pseudo-zero reaction,first-order reaction and second-order reaction,and the results showed that the degradation of Rhodamine B in heterogeneous electro-Fenton system is fit with the first-order kinetic equation.Through the UV-vis analysis of the degradation process of Rhodamine B,it is concluded that the removal of Rhodamine B in the heterogeneous electro-Fenton system is the result of the destruction of the conjugated structure of Rhodamine B and N-deethylation.The effect of iron-manganese-aluminum metal on the catalytic activity of heterogeneous metal catalysts was studied.The catalysts containing different metals were prepared for the removal of rhodamine B from heterogeneous electro-Fenton system,and the removal rate was used to fit dynamics.The results showed that the catalytic activity of catalysts loaded with multi metals is higher than that of single metal.The catalytic activity of catalyst supported metal manganese is higher than that of supported metal iron.The addition of aluminum metal in the catalyst has little effect on the catalytic activity of the catalyst,but the stability of the catalyst is significantly improved by aluminum ions.