Study On Catalytic Reduction Of 4-nitrophenol By Graphene Oxide And Composite Film

4-nitrophenol(4-NP)is one of the most common organic pollutants and is widely found in industrial and agricultural wastewater.The reduction product of4-aminophenol(4-AP)can be widely used in analgesic and antipyretic drugs,photographic developer,hair dye,corrosion inhibitor production,etc.In order to remove 4-nitrophenol,various methods such as adsorption,photocatalytic degradation,ozone oxidation,biological,electrochemical treatment and catalytic reduction have been developed.Among these methods,the catalytic reduction of 4-nitrophenol to4-aminophenol by sodium borohydride as a reducing agent has been considered as an effective and eco-friendly pathway.However,silver particles and nitrogen doped metal-free carbon catalysts have been widely used in the field of catalysis,which has attracted more and more attention.Therefore,the above two catalysts were designed in this paper,and the catalytic performance of catalytic reduction of 4-nitrophenol as4-aminophenol was studied.Polyvinylidene fluoride-silver-graphene oxide(PVDF-Ag-GO)nanocatalytic membranes were prepared by electrospinning for catalytic reduction of 4-nitrophenol as 4-aminophenol.Due to the small size of metal nanoparticles,high surface energy and easy agglomeration,which leads to the decrease of active sites and catalytic activity of silver particles.Therefore,we chose polyvinylidene fluoride as the membrane support material and loaded silver particles on its surface.Negatively charged oxygen radicals on the surface of graphene oxide can provide nucleation sites for silver particles,prevent agglomeration of silver particles and enhance catalytic activity.The PVDF-Ag(0-3%)-GO(0-2%)nanocomposite films with different content were prepared by electrospinning and characterized by SEM、XPS、EDX、FTIR、Raman.The effects of different graphene oxide content and silver loading,different temperatures,and different solution volumes on the catalytic reaction performance were systematically discussed.The cycling stability and related kinetic parameters of the nanocomposite films were discussed.The experimental results show that PVDF-2%Ag-1%GO nanocomposite film has the best catalytic activity,it can completely catalyze the reduction of 50 ml concentration of 20 mg/L of 4-nitrophenol in 70 minutes at room temperature,and it still maintains a high catalytic activity after recycling for five times.Although metal catalyst has high catalytic activity,it is expensive and expensive to use.The development of a highly active,durable and metal-free carbon catalyst capable of replacing metal-based catalysts is of increasing scientific and technological importance.Therefore,this study developed a nitrogen-doped metal-free catalyst with urea as nitrogen source and graphene oxide as carbon source.Two non-magnetic and magnetic nitrogen doped metal-free carbon catalysts were successfully prepared and used in the catalysis of 4-nitrophenol.the experimental results show that the nitrogen-doped metal-free carbon catalyst exhibits excellent catalytic activity in the catalytic reduction reaction of 4-nitrophenol,and the catalytic activity of non-magnetic nitrogen-doped metal-free carbon catalyst is higher than that of magnetic nitrogen-doped metal-free carbon catalyst.However,magnetic nitrogen-doped metal-free carbon catalyst facilitates the separation of catalyst and reaction solution compared with non-magnetic nitrogen-doped metal-free carbon catalyst.as a control experiment,we used pure graphene oxide and graphene oxide obtained by high temperature without nitrogen doping for catalytic experiments.The experimental results show that neither of these substances has catalytic properties because only carbon atoms doped with nitrogen atoms can be activated,resulting in more metal properties,thus providing catalytic sites for electron transfer on their surface to achieve catalytic reduction.