Preparation Of Co₃O₄ Core-shell Structure Catalyst And Its Application In Degradation Of Pollutants In Water

Due to the low biodegradability,persistence and toxicity of organic dyes,the contamination of wastewater by synthetic dyes has caused many health and environmental problems.Due to the persistence of these complex organic dyes,remediation of wastewater using traditional wastewater treatment techniques has become increasingly challenging.Advanced oxidation technology（AOPs）has become a potential treatment method for industrial organic dyes.By activating persulfate（PMS）,AOPs generates four main active substances:hydroxyl radical（·OH）,superoxide radical（O₂·-）,singlet oxygen（¹O₂）and sulfate radical（SO₄·-）.These free radicals are highly reactive due to their unpaired electrons and have demonstrated their ability to degrade organic pollutants.In the past,the efficiency of active free radicals produced by ultraviolet activation,thermal activation,microwave activation and alkali activation is not very high,and the operation is complicated and the energy consumption is high.Therefore,it is necessary to find a more efficient,energy saving and green way to activate persulfate in the oxidation process.By comparing with various activation methods,it is found that the activation of persulfate by transition metal catalyst may be a simpler and more effective method.The main work of this paper is as follows:（1）Preparation of R-Co₃O₄@SiO₂ catalyst and degradation of organic pollutants.Co（OH）₂ was prepared by hydrothermal method,and P-Co₃O₄ was calcined by Muffle furnace at high temperature.SiO₂ was loaded onto P-Co₃O₄ by simple stirring method,and R-Co₃O₄@Si O₂ catalyst was obtained by high-temperature calcination of argon,nitrogen and hydrogen mixture.The morphology,structure and element distribution of the materials were characterized and analyzed by a series of physical and chemical structure characterization.In addition,some factors affecting the degradation activity were also studied.At room temperature,0.10 g/L PMS was activated with 1 mg R-Co₃O₄@Si O₂ catalyst,and 40 m L of20 mg/L Coomas bright blue was completely removed within 4 minutes.The degradation rate constant k was 5.62 min^-1.The free radical test results showed that ¹O₂,SO₄·-,O₂·-and·OH all participated in the removal of pollutants,and ¹O₂ and O₂·-played a decisive role in the degradation process.（2）The preparation of R-Co₃O₄@CoNC catalyst and the degradation of organic matter such as Coomas bright blue.The structure and physicochemical properties of R-Co₃O₄@CoNC catalyst were characterized by SEM,XRD,BET,XPS and TGA.At room temperature,0.15 g/L PMS were activated with 1 mg R-Co₃O₄@Co NC catalyst,and 40 m L20 mg/L Coomasil bright blue was completely degraded for less than 4 minutes.The rate constant k value was up to 7.16 min^-1.They are 340.9 times higher than PMS and 447.5 times higher than R-Co₃O₄@Co NC system.The free radical test results showed that only three kinds of free radicals participated in the removal of pollutants from SO₄·-,O₂·-and ¹O₂,and·OH free radicals did not participate in the removal of pollutants,among which ¹O₂ and O₂·-played a decisive role in the degradation process.Therefore,this work provides a new idea for the preparation of transition metal catalyst with high efficiency activated peroxysulfate to degrade organic pollutants,and also provides a possible practical application value for wastewater treatment.