Facile Synthesis Of Porous Fe-doped G-C₃N₄ With Highly Dispersed Fe Sites For Dinitrophenol Pollutants Degradation By Peroxymonosulfate Activation

The refractory organic pollutants in water have attracted great public attention due to their toxicity,carcinogenicity and bioaccumulation,which could be a serious threat to human beings and ecosystem.Presently among various treatment methods for organic pollutants,advanced oxidation technology of persulfate（SR-AOPs）as a new sewage treatment technology has attracted extensive attention of researchers.Iron is a transition metal element widely existing in nature,and has the characteristics of large abundance,non-toxic and environment-friendly.Therefore,the application of iron-based catalysts in SR-AOPs has a good prospect.However,at present,most Fe doped g-C₃N₄ materials are prepared by mixing iron salt and single g-C₃N₄precursor in solution,drying and high temperature calcination,which may lead to a large number of active sites being covered.In addition,some researchers have prepared Fe doped thin-layer g-C₃N₄ catalyst by introducing concentrated strong acid,but its preparation process is complex.It is,therefore,highly desirable to explore facile synthesis strategies of Fe doped g-C₃N₄ to further improve PMS activation capacity for environmental remediation applications.In view of the above problems,this thesis includes the following contents:（1）A series of porous Fe doped g-C₃N₄（x Fe-CN）catalysts with different Fe doping were prepared via a simple solid phase grinding reaction followed by thermal annealing treatment with thiourea as pore forming agent and iron dispersant,melamine as carbon nitride precursor and iron nitrate as iron source.The catalysts were characterized by XRD,FT-IR,XPS,HR-TEM and BET.The results show that the introduction of thiourea and Fe transforms the layered g-C₃N₄ into a three-dimensional network porous structure,and the specific surface area has also been improved.（2）Taking 2-sec-butyl-4,6-dinitrophenol（DNBP）as the target pollutant,the performance and reaction mechanism of the prepared catalyst activated PMS for oxidative degradation of DNBP were explored.At the same time,the effects of different reaction factors on the reaction process were investigated,and the optimum degradation conditions were explored.The results show that x Fe-CN material as PMS heterogeneous catalyst has excellent catalytic activity and good recycling.With the increase of Fe content,the performance of catalyst activated PMS first improves and then decreases,of which 12.5%Fe-CN is the best.The optimum degradation conditions were as follows:at room temperature,the amount of catalyst was 0.3 g/L,the concentration of PMS was 0.6 g/L,the initial p H=5.5.The oxidative degradation process of DNBP includes free radical(·OH and SO₄^·-)and non-free radical(Fe^IV=O)pathways.（3）Considering that a single g-C₃N₄ itself is a good photocatalyst and PMS can be activated by light,the properties of the prepared x Fe-CN materials for photodegradation of DNBP and degradation of DNBP by photosynthetically activated PMS were comprehensively evaluated with 500 W xenon lamp simulating sunlight and DNBP as the target pollutant,and the corresponding reaction mechanism was put forward.The results show that the prepared catalyst has little effect on photocatalytic degradation of DNBP,and its PMS activation performance is significantly improved under the condition of light excitation;the doping of highly dispersed Fe can obviously change the electronic structure of g-C₃N₄ and improve its light absorption performance,so that it can use the visible light with longer wavelength in the process of activating PMS.Different from the process of activating PMS without light,h⁺plays a more important role than·OH and SO₄^·-reactive oxygen radicals in this process.