Degradation Of Simulated Levofloxacin Wastewater By Heterogeneous Catalytic Oxidation Of Co-Fe PBAs@rGO/PMS System

Advanced oxidation processes（AOPs）is widely used in the removal of difficult biodegradableorganic matter,because it can produce reactive free radicals,such asOH^·、O₂^·-、·OOH、SO₄^·-etc.The advanced oxidation technology based on the free radical of sulphuric acid is a new kind of new technology which is very promising to remove the organic pollutants which are difficult to degrade.Under neutral or alkaline conditions,the redox potential of SO₄^·-（2.5-3.1 V）is higher than that of OH^·（1.8-2.7 V）,even under acidic conditions,both have similar oxidation capacity.Compared with OH^·,SO₄^·-the reaction system of pH has wider range,longer half-life,higher salinity and slower consumption rate of original oxidant,which is beneficial to the improvement of oxidant utilization efficiency.SO₄^·-can be produced by activation of PMS by metal ions,metal oxides,non-metallic catalysts and so on.Among them,Co（II）is a metal ion activated PMS degradation of organic compounds is the most effective,Co（II）homogeneous catalytic oxidation system has the advantages of simple operation,fast reaction rate,but the presence of metal ions is not easy to recycle,cause two pollution problems such as Co²⁺into the environment,and the heterogeneous cobalt oxide system effectively the homogeneous system problem.This paper mainly through the magnetic composite catalyst Co-Fe PBAs@rGO synthesis,catalytic single peroxomonosulfate（PMS）to produce sulfate radical,degradation of typical quinolones levofloxacin hydrochloride（LVF）,to study the catalytic performance of the catalyst.Meanwhile,several important parameters affecting the reaction were investigated,and the best reaction conditions,the stability of the catalysts,the amount of cobalt and iron ions dissolved in the solution and the influence of inorganic salt ions Cl^-on the LVF degradation process were also determined.The influence and effect of ultrasonic and light aid on Co-Fe PBAs@rGO/PMS system were investigated.The main contents and conclusions of this paper are as follows:（1）Preparation and characterization of catalystCo₃[Fe（CN）₆]₂ prepared by coprecipitation method and graphite oxide prepared by the modified ummers method were used to synthesize Co-Fe PBAs@rGO nanocomposite catalyst by hydrothermal method。By XRD,FT-IR,BET,SEM,TEM,XPS,VSM and other characterization methods of catalyst crystal structure,microstructure,physical adsorption,chemical structure,magnetic intensity and other aspects were analyzed,the results show that the Co-Fe characterization of PBAs successfully loaded onto rGO,in the sample preparation process,accompanied by a small amount of CoFe₂O₄.Most of the GO in graphene composites have been reduced,and Co-Fe PBAs NPs is uniformly dispersed on the surface of rGO and its particle size is larger than before the load.The saturation magnetization of Co-Fe PBAs@rGO composites is 15.29emu/g,and the specific surface area and pore volume are 186.84 m²/g and 0.38 cm³/g respectively,and the pore size is 3.4 nm.（2）Catalytic activity and stability test of Co-Fe PBAs@rGOBy studying the catalytic activity of Co-Fe PBAs@rGO,we know that Co-Fe PBAs@rGO atalyzes the degradation of LVF by PMS.The effect is very good.The catalytic effect of Co-Fe PBAs,Co-Fe PBAs@rGO and CoFe₂O₄@rGO is compared.The result is Co-Fe PBAs@rGO>Co-Fe PBAs>CoFe₂O₄@r GO.Through the research on the effect of several important reaction parameters,and considering the factors of reaction efficiency and economic utility and so on,the optimal reaction conditions for the final:the original LVF concentration is 20mg/L,the catalyst concentration is 50mg/L,the concentration of PMS is 1mM,not adjusting the initial pH,the reaction temperature is room temperature 25±2℃.Under this condition,the degradation efficiency of LVF in 30min was 79.8%.Through the study of inorganic ions could influence the degradation efficiency of LVF.The results show that high concentration of Cl^-to the inhibition of LVF degradation.The experiment of free radical quenching showed that the degradation of LVF was the main effect of SO₄^·-in the system.When the catalyst was used for 5 cycles,the catalyst still showed high catalytic activity,indicating that Co-Fe PBAs@rGO was recyclable and reusable.（3）The influence of ultrasonic and light aid on the heterogeneous Co-Fe PBAs@rGO/PMS/LVF ystemConsidering that ultrasound and light can play an auxiliary role in the reaction system,and raphene and PBAs have optical properties,they can absorb most of the wavelength light in the solar spectrum.In this paper,the degradation of LVF by ultrasonic and light assisted Co-Fe PBAs@rGO/PMS catalytic oxidation system was studied.The results show that ultrasonic cavitation can effectively increase the degradation rate of Co-Fe PBAs@rGO/PMS LVF in the system,but the final degradation rate has little effect;light has auxiliary effect on Co-Fe PBAs/PMS and Co-Fe PBAs@rGO/PMS system,an increase in the degradation rate of LVF at the same time,also improves the degradation efficiency.