Copper Iron Oxide/Graphene Composite Catalyzes Persulfate Treatment Of Azo Dye Methyl Orange

With the rapid development of society,more and more people's needs have made dyes widely used in various industries.Azo dyes are widely used because of their stable properties,simple preparation and low economic cost.As a result,a large number of azo dye wastewater has caused serious pollution to the environment.Azo dye wastewater belongs to refractory wastewater which has high content of organic pollutants,deep chromaticity,poor biodegradability and high toxicity.Therefore,the innocuous treatment is a difficult point in the field of wastewater treatment.Sulfate radicals?SO₄^-·?based advanced oxidation process was a green and efficient pollutant treatment technology.In recent years,due to its superior oxidation performance,it has become a research hotspot in the field of wastewater treatment at home and abroad.However,persulfate is relatively stable at room temperature and cannot decompose to produce SO₄^-·to degrade pollutants effectively,so additional methods are needed to assist its activation to produce SO₄^-·.Transition metal ion activation is the simplest and most convenient method.However,the traditional metal ion activation method has a large amount of metal ions dissolving,which easily causes secondary pollution of the environment.Therefore,stable and efficient heterogeneous catalysts have become the focus of attention of researchers.In this paper,graphene?RGO?was used as a carrier to prepare nano-CuO/RGO,magnetic nano-Fe₃O₄/RGO,and magnetic nano-CuFe₂O₄/RGO composite materials as heterogeneous catalysts for persulfate experiments.The main results are as follows:?1?The prepared nano-CuO/RGO catalyst has good catalytic performance and can and can activate persulfate to rapidly produce SO₄^-·,thereby effectively oxidizing and degrading pollutants.Lower pH is more beneficial to the removal of MO by this oxidation system.Under the rotational speed was 180 r/min,at normal temperature when the CuO/RGO dosage was 50mg,the initial concentration of Na₂S₂O₈ was 4 mmol/l,pH=4 and the initial concentration of MO was 50 mg/l,the removal rate of methyl orange reached 95.6%in 90 minutes.The results of XRD,SEM,and FTIR characterization of the nano-CuO/RGO catalyst showed that the catalyst had good crystallization and high purity.The catalyst has good reusability and maintains high catalytic activity after five cycles.However,the recovery of catalyst needs high speed centrifugation to separate the catalyst from solution,which increases the economic cost.?2?The magnetic nano Fe₃O₄/RGO catalyst has strong magnetism,and its saturation moment were 51.26 emu/g,which can quickly achieve solid-liquid separation under the action of an external magnetic field.XRD,SEM,FTIR,and XPS characterization results show that the prepared catalyst reaches the nanometer level,Fe₃O₄ was successfully supported on the graphene surface,and was regular spherical shape with an average diameter of 21 nm.Under the initial concentration of Na₂S₂O₈ was 5 mmol/l,Fe₃O₄/RGO the dosage was 50 mg,the concentration of MO was 50 mg/l,pH=2,the volume of water sample was 50 ml,the rotational speed was 180 r/min,the removal rate of MO was 88.9%in 90 minutes.The removal rate of methyl orange after the catalyst was used five times was 70.2%.Compared with the nano-CuO/RGO catalyst,the treatment effect is slightly worse,but due to its strong magnetism,its recycling and utilization was more simple,convenient and economical.?3?Magnetic nano-CuFe₂O₄/RGO catalyst combines the advantages of nano-CuO/RGO and magnetic nano-Fe₃O₄/RGO catalysts.Which catalytic persulfate has a good effect on the treatment of methyl orange.The VSM characterization results show that it has strong magnetism,the saturation moment were 42.9 emu/g.And can achieve solid-liquid separation within 20 s under the action of an external magnetic field,which was easy to recycle.XRD combined with Debye-Scherrer formula,SEM,FTIR,XPS characterization analysis results show that the prepared magnetic nano-Cu Fe₂O₄/RGO catalyst has good crystallinity and high purity,a large number of oxygen-containing functional groups of graphene oxide disappear during the hydrothermal preparation process,the oxidation Graphene was reduced to graphene.CuFe₂O₄ particles are loaded on graphene in a regular spherical shape with an average diameter of 45 nm.The oxidative degradation experiment showed that when the concentration of methyl orange was 50 mg/L,the initial concentration of persulfate was 5 mmol/L,the dosage of CuFe₂O₄/RGO was 50 mg,pH=2 was the best conditions.After 90 minutes,MO was completely removed.The orthogonal experiment shows that the order of influence of each factor on the treatment effect is:reaction time>initial pH>CuFe₂O₄/RGO dosage>initial Na2S2O8 concentration.In addition,after five repeated uses of the catalyst,the removal rate of MO remained was still above 90%,which showed superior recycling performance.?4?Oxidation of MO degradation mainly by the catalytic reaction system to produce a radical having a strong oxidation activity.The radical capture experiments show that SO₄^-·was the main radical for the effective oxidative degradation of MO during the oxidative degradation.