Modification Of Graphite Felt Material And Degradation Of Coking Wastewater By Heterogeneous Electro-Fenton

Electro-Fenton is a new type of advanced electrochemical oxidation technology,which can generate a strong oxidant hydroxyl radical(·OH)in solution,non-selective oxidation degradation of most organic pollutants in water,it is considered an environmental-friendly green process.From the research progress of the Electro-Fenton technology,it can be seen that the further development of its technology in sewage treatment faces two challenges:oxygen is prone to four-electron reaction during the reduction process of the cathode,and the generation efficiency of hydrogen peroxide is not high;Fe²⁺will generate Fe³⁺in the process of participating in Fenton reaction.When the p H of the solution is high,Fe(OH)₃ precipitates and a lot of iron sludge is produced,which reduces the degradation efficiency Therefore,the development of cathode catalysts containing highly selective iron active substances is a hot topic widely concerned by scholars at home and abroad.Graphite felt(GF)has an excellent spatial structure,high conductivity and low price.It is an excellent catalyst carrier.Transition metal nickel and cobalt compounds can form co-Fenton catalyst with iron,which is conducive to improving the efficiency of·OH generation.In this paper,a simple hydrothermal reaction is used to produce graphite felt as a carrier,iron-nickel-cobalt ternary hydroxide as the active substance,PTFE hydrophobic treatment as the cathode of the electric Fenton system,and graphite felt as the anode.On the Fenton reaction device,the degradation effect of coking wastewater was investigated,and the influence of different parameters on the reaction was explored.The specific research contents and conclusions are as follows:(1)The iron-nickel hydroxide was loaded on graphite felt,and the effects of different iron-nickel molar ratio catalysts on the degradation performance of coking wastewater were explored.The morphology,composition and other microstructures of the prepared catalyst were characterized by SEM,XRD and other technologies,which proved that the active material of iron-nickel hydroxide was successfully loaded on the surface of graphite felt.Electrochemical tests were performed on a rotating disk electrode(RDE)and the electron transfer numbers of different catalysts were calculated.It was found that the Fe₄Ni₁-OH/GF catalyst had an electron transfer number n=2.5,which was the closest to the two-electron reduction reaction,using a three-electrode in the system test,the applied potential was-0.6 V,and the coking wastewater was used as the experimental object.Among the five different catalysts with different iron-nickel ratios,the Fe₄Ni₁-OH/GF catalyst with an iron-nickel molar ratio of 4/1 had the highest degradation efficiency for coking wastewater,reached 57.8%.(2)Control the iron-nickel molar ratio to 4/1,change the content of cobalt,and prepare the iron-nickel-cobalt ternary hydroxide catalyst supported on the surface of the graphite felt,electrochemical results show that the electron transfer number of 10%Co-Fe₄Ni₁-OH/GF catalyst in the potential range of-0.5 V to-0.9V is about 2.5,which is wider than the potential range of Fe₄Ni₁-OH/GF catalyst for two-electron oxygen reduction.(3)A self-made gas disk is used for aeration and an Electro-Fenton packed bed reaction device is designed,using 10%Co-Fe₄Ni₁-OH/GF as the cathode catalyst,GF as the anode catalyst,and coke wastewater as the research object for small-scale amplification experiments optimize the experimental conditions.When the reactor operating voltage is 3.0 V,the liquid flow rate is 1.0 L/h,and the gas flow rate is 1.0 L/min,the degradation effect of coking wastewater is the best,with a degradation rate of 40.1%.The reactor was continuously operated for120 h,and the COD of the coking wastewater at the outlet showed an upward trend,rising from 79.8 mg/L to 95.3 mg/L.The degradation rate of coking wastewater changed from 48.0%to 37.8%.This shows that the catalyst has good stability and can be used as a candidate catalyst for further amplification.