Preparation Of Magnetic Graphite Oxide And Its Catalytic Activity To Dyeing Wastewater Treatment

Electrocatalytic oxidation and heterogeneous Fenton can effectively treat dyeing wastewater,where the development of electrode materials and highly active catalysts has been the focus of research.Magnetic graphite oxide(MGO)has the advantages of high catalytic activity and good dispersion of magnetic material on the surface.However,the preparation of MGO with potassium permanganate or potassium chlorate is susceptible to secondary contamination and explosion risk.Therefore,there is an urgent need to find a new method that is safe,efficient and pollution-free.In this paper,MGO was synthesized in situ using a modified Hummers method with potassium percarbonate(K₂Fe O₄)as the oxidant and iron source.MGO/CB electrode was prepared by mixing MGO with carbon black(CB)and combined with DSA anode to construct an electrocatalytic oxidation system.In addition,a heterogeneous Fenton system was constructed to treat Reactive Red X-3B simulated dyeing wastewater using MGO as a catalyst.The operating parameters in both oxidation systems were investigated,and the catalytic activity and mechanism of MGO were studied.The details of the study are as follows:In the MGO/CB electrocatalytic oxidation system,the effects of potassium ferrate,hydrogen peroxide,deionized water and roasting temperature on the structure and electrocatalytic activity of MGO/CB were investigated.The results showed that a large number of oxygen-containing functional groups were introduced into the graphite after K₂Fe O₄ oxidation.With the increase of K₂Fe O₄ dosage,the oxidation degree of graphite tended to be stable and gradually changed from hydrophobic to hydrophilic.The calcination temperature had an effect on the crystalline phase and catalytic activity of iron oxide.The optimal conditions for the preparation of MGO were determined as 50 m L sulfuric acid mixed with 2 g graphite,6 g potassium ferrate,45 m L deionized water and calcination temperature of 300?.The cycle stability of the MGO/CB electrode can be improved by adding conductive carbon black and roasting.The optimized electrode showed excellent electrocatalytic activity under both neutral and alkaline conditions and could be reused at least 9times.Both cathode and anode played a role in the decolorization of dyes.MGO/CB made the main contribution in organic degradation and its synergistic effect resulted in a significantly higher catalytic activity than the mixture of iron oxide and graphite oxide.The coexistence of various iron oxides can increase the active sites of iron.Under the action of cathodic reduction and free radicals(~1O₂,·O₂^-),the COD_cr removal reached 77%,and the dye wastewater could be completely decolorized after 4 h.In the heterogeneous Fenton system of MGO/H₂O₂,color and COD_cr removal of Reactive Red X-3B simulated wastewater reached 99.8%and 86.31%after 2 h at the catalyst and hydrogen peroxide dosing of 3 g/L and 15 m M,respectively.The results showed that MGO had high catalytic activity at the initial p H 2-9.The large number of acidic functional groups on the surface of MGO formed the surface acidic microenvironment,which released H⁺and lowered the system p H,promoting the multiphase Fenton reaction.Under the joint action of dissolved iron and surface iron,H₂O₂ can be effectively converted into active substances such as^·OH and ~1O₂.The synergistic effect of MGO and iron oxides surface defects accelerated the adsorption and oxidation of pollutants at the acidic interface.The catalytic performance of MGO was stable and can be reused more than 5times.This study may provide a theoretical basis for the application of MGO/CB electrode and MGO Fenton-like catalyst for the treatment of dyeing wastewater.