| Electro-Fenton,a advanced oxidation process,can generate highly reactive radicals hydroxyl radical(·OH)and remove organic pollution effectively.It has many advantages such as operability,simple device,low cost,good treatment efficiency.The electrode materials,especially cathode materials,are the core part in EF process,which can remove organic pollution by in situ generate H2O2.How to enhance the diffusivity of O2 to cathode and accelerate the two-electron reduction of O2 to H2O2 are the important indictors of cathode in EF process.Graphene have good electrical conductivity,chemical stability,large specific surface area,and rich active sites.Due to lower binding energy with H and high capacity for adsorption and storage of H than other metals,Pd has been proposed as a promising catalyst for the direct synthesis of H2O2.Base on this,we synthesized three-dimensional(3D)macroporous graphene aerogels(GA),which was in-situ assembled by reduced graphene oxide(rGO)sheets on titanium wire as binder-free electrode.Pd/rGO/carbon felt from palladium(Pd),reduced graphene oxide(rGO)and carbon felt.The 3D GA and Pd/rGO/carbon felt were used as cathodes respectively,and graphite tube was used as anode.The EF process was carried out by a beaker experiment for the removing of EDTA-Ni.The graphene oxide(GO)was prepared according to a modfied Hummer’s method,then VC was used as reductant to synthesized 3D GA which was used as cathode in the following experiment.Pd/rGO/carbon felt was synthesized by palladium acetate and rGO reduced by sodiumformate solution and then modified on carbon felt by Nafion ethanol solution.The Xray diffraction(XRD),Scanning Electron Microscopy(SEM),Transmission Electron Microscope(TEM),Brunauer-Emmett-Teller(BET),Cyclic Voltammetry(CV),Linear Sweep Voltammetry(LSV)and Rotating Ring-disk Electrode(RRDE)were used to analysied the synthetical 3D GA and Pd/rGO/carbon felt.Results indicated 3D GA formed three dimensional architecture with large and homogenous macropore structure and surface area.The cathode displayed the highest current density and electrochemical active surface area(EASA)at pH 3,and better two-electron selectivity for ORR than other pH value,confirming the 3D GA cathode at pH 3 has the highest electrocatalytic activity and generates more H2O2.The factors such as pH,applied current,concentration of Fe2+,Na2SO4,and aeration rates of air were also investigated.Under the optimum conditions,73.5% of EDTA-Ni was degraded after reaction for 2 h.Mechanism analysis indicated that that the production of ·OH on the 3D GA cathode played an important role in the removal of EDTA-Ni in the 3D GA-EF process,where the direct regeneration of Fe2+ on the cathode would greatly reduce the consumption of H2O2.Therefore,it is of great promise for 3D GA catalyst to be developed as highly efficient,cost-effective and durable cathode for the removal of EDTA-Ni.The characterization results of Pd/rGO/carbon felt showed that the presence of rGO in Pd/rGO/carbon felt significantly increased the current response of two-electron reduction of O2(0.45V).The key factors influencing the removal efficiency of EDTA-Ni,such as pH,current and Fe2+ concentration,were investigated.Under the optimum conditions,the removal efficiency of EDTA-Ni reached 83.8% after 100 min EF treatment.Mechanism analysis indicated that introducting of rGO in Pd/rGO/carbon felt significantly enhanced the electrocatalytic activities by inducing ·OH in EF process,direct H2O2 oxidation still accounted for a large amount of EDTA-Ni removal efficiency. |
PDF Full Text Request