Performance And Mechanism Of Iron-based Graphene For Remediation Of Glyphosate Contaminated Water

In view of the widespread use of glyphosate（GLY）in agricultural production,this paperfocuses on the development of high-performance graphene-ferrite composites,constructs a highly efficient adsorption and oxidation system for the repair of GLY contaminated water,and studies the adsorption properties of composites on GLY and the process mechanism of the activation of persulfate oxidants to degrade GLY.It mainly includes the following research contents:1.The magnetic reduced graphene oxide（rGO-Fe₃O₄）,with easy separation and high adsorption performance,was prepared and used to treat GLY contaminated water.GLY adsorption performance of rGO-Fe₃O₄ was investigated and influences of pH,adsorption time,temperature,contaminant concentration,and competing anions were analyzed.Moreover,the adsorption mechanism was discussed in the light of several characterization methods,including scanning electron microscopy（SEM）,energy dispersive spectrum（EDS）,Fourier transform infrared spectroscopy（FTIR）,and X-ray photoelectron spectroscopy（XPS）.The results demonstrated that the rGO-Fe₃O₄presented a significant GLY adsorption capacity and acid condition was beneficial for this adsorption.The process of adsorbing GLY by rGO-Fe₃O₄ was controlled by monolayer adsorption and chemical adsorption,and this reaction is prone to occur.Thermodynamic studies revealed that the adsorption of GLY onto rGO-Fe₃O₄ was spontaneous,endothermic and feasible process.High temperatures were beneficial to GLY adsorption.The GLY adsorption mechanism of rGO-Fe₃O₄ was mainly attributed to hydrogen-bond interaction,electrostatic interaction,and coordination,these effects greatly promote the reaction.2.Reduced graphene-based iron oxide composite was prepared via thermal chemical deposition method and used to remove GLY contaminated water by a dynamic adsorption experiment.Influences of GLY concentration,solution pH,flow rate and filler bed height were analyzed.Moreover,the dynamic adsorption mechanism was discussed by characterization means of SEM,EDS,XPS and automatic specific surface area and pore size distribution analyzer,as well as Thomas,Yoon-Nelson and Yan adsorption models.The results demonstrated that:when the initial concentration of GLY is 40mg/L,the filler bed height is 1.2cm,the pH value is 4,the flow rate is0.5ml/min,the temperature is 298K,the composite has excellent performance in dynamic adsorption GLY.In addition,Thomas,Yoon-Nelson and Yan models can well describe the process of dynamic adsorption of GLY by composites,but the Yan model fitting results has a better fit to the reaction.3.Two kinds of catalysts of three-dimensional graphene and its composite materials（3D-rGO and 3D-rGO-Fe₃O₄）were prepared by hydrothermal method and applied to the static experiment of oxidative degradation of GLY by active Na₂S₂O₈.Influences of Fe-C ratio,solution pH,oxidant quality,temperature,coexisting ions and material repeatability were analyzed.Moreover,the degradation mechanism was discussed by characterization means of SEM,EDS,XPS,FTIR and automatic specific surface area and pore size distribution analyzer,electron paramagnetic resonance spectrometer（EPR）as well as Thomas,Yoon-Nelson and Yan adsorption models.The experimental results show that:The composite catalyst had good reusability,and the GLY degradation rate increased with the increase of the temperature.When the initial concentration of GLY is 30mg/L,the rotation speed is 110rpm,the mass ratio of graphene to FeSO₄·7H₂O is 1:7,the pH value is 4,the quality of Na₂S₂O₈ is 48mg,the temperature is 298K,the 3D-rGO-Fe₃O₄ composite catalyst has excellent performance in degrading GLY by active Na₂S₂O₈.The degradation rate of the reaction system was96.8%,the rate constant was 2.1×10³min^-1,half-life was 330.07min,the correlation coefficient R² was 0.994,and the pseudo-first-order kinetic model can well describe the process of degradation of GLY by Na₂S₂O₈.In addition,coexisting ion experiments showed that Cl^-,NO₃^-,Mn²⁺,Zn²⁺,Mg²⁺and CO₃^2-all showed a certain inhibitory effect on the degradation process.