Study On Fenton-like And Persulfate Activation Performance Of Copper-based Composite Metal Oxides

Removing refractory organic pollutants from water is still a challenge for environmental remediation.These pollutants can be degraded by reactive oxygen species?ROS?produced from the activation of some oxidants.Advanced Oxidation Processes?AOPs?are techniques that produce highly active substances and can oxidize refractory organic contaminants.Among them,the heterogeneous Fenton oxidation and persulfate activation technologies are two representative technologies in the advanced oxidation process.In recent years,the research on heterogeneous catalysts based on these two reactions has become the focus of scientists.The transition metals represented by iron and copper have the advantages of low cost,high stability and good activity.The multi-component composite metal oxides can accelerate interfacial electron transfer through the synergy between different metals,promote the decomposition of hydrogen peroxide to generate active radicals,and improve the removal efficiency of organic pollutants.Therefore,this paper is mainly for the development of a series of copper-based bimetallic or multi-metal composite oxide catalysts,which are used to degrade dye contaminants and antibiotic wastewater,and focus on the Fenton oxidation technology and persulfate activation technology.Explore the reaction mechanisms and principles.The specific studies include the following three parts:?1?In order to provide useful information for the rational design of effective Fenton-like catalyst,a series of Cu-based bimetallic oxides were synthesized and their Fenton-like performances for the degradation of Orange II and ciprofloxacin were compared.The structure,chemical oxidation state,surface charge property and redox ability of the catalysts were also investigated by different characterization techniques.Among them,NiCu exhibited the highest adsorption capacity towards Orange II and the highest activity for the production of·OH from H₂O₂ decomposition,which could be attributed to its high surface area and highly positively charged surface.However,FeCu exhibited the highest activity for the degradation of Orange II.The reason might be that FeCu has more unpaired electrons and higher redox ability,thus promoting the activation of adsorbed Orange II through the electron transfer process.By contrast,NiCu exhibited the highest activity for the removal of ciprofloxacin because ciprofloxacin was mainly degraded by·OH.Finally,the main degradation intermediates of Orange II and ciprofloxacin were determined by liquid chromatography-mass spectrometry.?2?Cu-Fe-Ni composite metal oxide catalysts were prepared by hydrothermal method for the degradation of ciprofloxacin and acid orange II by Fenton reaction.The Cu-Fe-Ni ratio was 2:1:1.The activity was the best,and the effects of different reaction conditions on the degradation efficiency of the pollutants were discussed,and the optimal reaction conditions were determined.It was confirmed by characterization that·OH and·O2-are the main active species degrading ciprofloxacin and acid orange II,respectively,consistent with the results of the first part of the bimetal oxide.?3?Cu-Fe composite oxides with different Cu:Fe ratios were synthesized by a hydrothermal method and investigated as a heterogeneous catalyst for persulfate activation.The obtained samples exhibited much higher activity than CuFe₂O₄ for the degradation and mineralization of ofloxacin with persulfate,and the optimized Cu:Fe ratio was 1:1?CuFe1?.The results of catalyst characterization and electron paramagnetic resonance analysis indicate that the activities of the catalysts for ofloxacin degradation and superoxide radical?·O₂^-?production are highly positively correlated with their redox ability.The removal efficiencies of ofloxacin in the presence of different scavengers further demonstrate that·O₂^-is the dominant reactive species in this process,which is quite different from previous studies.It is suggested that CuFe1 with higher oxidation ability could weaken the S-O bond of adsorbed persulfate,thus promoting the decomposition persulfate into·O₂^-.Finally,the possible degradation pathway of ofloxacin was proposed according to the liquid chromatography-mass spectrometry result.