Synthesis Of Two-Dimensional Carbon-Based Nanomaterials And Their Performance Of Activating Peroxymonosulfate For Degradation Of Pollutants

Advanced oxidation process based on persulfate has attracted much attention in recent years,compared with other technologies,it has many advantages,such as low price,wide application range of p H,high stability,fast reaction rate and so on.Activators are mainly divided into carbon materials and transition metal ion,but the activation efficiency of carbon materials is low and the activation mechanism is not clear,and transition metal ions have poor stability and secondary pollution and other problems.Therefore,it is of great significance to develop the catalysts with high activity and stability and to clarify the catalytic activation mechanism.Two dimensional carbon based nanomaterials have great potential in the field of persulfate activated degradation of organic pollutants due to their low price,good chemical stability,environmental friendliness and high mass transfer efficiency.In this paper,two-dimensional carbon materials were modified by doping or combining with cobalt based transition metals to prepare low-cost,high activity and environment-friendly peroxymonosulfate（PMS）activated catalysts,and a synergistic system of photocatalysis and PMS activation was constructed to study the effects of preparation conditions and reaction conditions on the activation degradation,The structure-activity relationship was elucidated through the systematic analysis of the structural characteristics and activation degradation performance of the catalyst,which provided ideas for carbon based materials to activate PMS to degrade pollutants.The main research contents and conclusions are as follows:（1）High nitrogen doped carbon nanosheets（HANC）was synthesized by in situ template method using petroleum asphalt as carbon source,dicyandiamide as nitrogen source.The effect of heat treatment temperature and reaction conditions on the degradation performance of activation was studied,and the mechanism of catalytic activation was explored.HNAC mainly has a sheet-like structure and has excellent activation and degradation performance.The degradation rate of 20 mg/L tetracycline by HNAC-800 can reach more than 80%within 10minutes,and the catalyst has a wide range of p H,The strong anti anion interference,stability and universality.Quenching experiments and EPR tests show that the reaction is mainly carried out through non-radical pathways and a small amount of radical pathways.The experimental results show that high nitrogen doping improves the surface chemical activity of carbon materials,and the active sites may mainly come from nitrogen doped ortho carbon atoms.Meanwhile,the delocalized electrons also have high catalytic activity,which provides a reference for carbon based nonmetallic materials to activate PMS to degrade organic pollutants.（2）On the basis of the previous work,the single-atom Co-N-C catalyst was prepared by introducing cobalt salt in situ.The effects of heat treatment temperature and reaction conditions on the activation and degradation performance were investigated.The activation and degradation mechanism of PMS was explored by combining experiments and simulation calculation.Co-N-C has high activity,high stability and universality.The degradation rate of50 mg/L tetracycline can reach more than 80%in 10 minutes,and the catalyst has a wide range of p H,the strong anti anion interference.The quenching experiment and EPR test showed that the reaction was mainly carried out through radical pathway and a small amount of non-radical pathway.The experimental results and DFT calculation showed that the single atom pyridine Co-N₄ was the main catalytic active site.The strong interaction between pyridine nitrogen and atomically dispersed cobalt atoms can reduce ion aggregation,inhibit ion leaching,and improve catalytic activity and stability.At the same time,the two-dimensional structure can increase the contact area of the catalyst with PMS and pollutants,so as to develop efficient and stable cobalt based monatomic activation materials.（3）g-C₃N₄ nanomaterials were prepared by thermal polymerization,and further load cobalt oxide to prepare Co O_x@C/g-C₃N₄.The effects of cobalt oxide ratio and heat treatment temperature on the degradation of tetracycline by photo assisted activation of PMS were studied.The results show that the composite material can enhance the light absorption performance,and the carbon shell coating can effectively improve the electron transfer efficiency between Co O_xand g-C₃N₄,promote the electron hole separation and the variable valence cycle of cobalt,so as to effectively enhance the activation degradation performance of PMS.Co O_x@C/g-C₃N₄ can almost completely degrade 10 mg/L tetracycline in 60 minutes,and the catalyst has a wide range of p H,the strong anti anion interference and universality.It provides a new idea for the coupling of photocatalysis and PMS activation technology to realize photo assisted PMS activation.