| Recently,peroxymonosulfate（PMS）based advanced oxidation technology has become one of the most promising wastewater treatment technologies due to its high catalytic efficiency and strong oxidation ability.Among PMS activation,the transition metal was widely used to activate PMS because of its mild reaction conditions without the additional energy.However,there still are some shortcomings such as lower catalytic efficiency,secondary pollution,poor p H adaptability and environmental tolerance in current transition metal activation methods.Therefore,the development of more efficient and environmental-friendly transition metal-based catalystic materials was urgently required.In this paper,a series of highly efficient heterogeneous iron/nitrogen/carbon catalysts with different dispersion were constructed by using low-cost and environmental-friendly metal iron as the catalytic active center,nitrogen doped carbon materials with rich micropore structure and good conductivity as catalyst carrier.The catalytic performances of these catalysts were evaluated by PMS activation for the removal of organic pollutants.This paper focuses on the composition,structure,catalytic performance,catalytic mechanism,p H adaptability and environmental tolerance of these catalysts.The main details are as follows:Iron and nitrogen co-doped porous carbon catalyst（Fe-NC）was fabricated by a facile calcination process using aniline andα-Fe2O3 as the precursors,and characterized by XRD,XPS,FE-SEM,TEM.The Fe-NC coupled with PMS could achieve 96%removal rate of sulfathiazole（STZ）in 40 min without the influence of solution p H and the removal efficiency was 6 times higher than that of the commercialα-Fe2O3 catalyst.Furthermore,Fe-NC also presented a favorable catalytic performance for removing other organic pollutants including phenolic compounds and organic dyes.The catalytic mechanism was elucidated by EPR and trapping tests,which confirmed that O2·-and 1O2 were dominant in the Fe-NC/PMS system.The three-dimensional porous carbon aerogel（CA）supported well-dispersed iron and nitrogen co-doped carbon（Fe NC-CA-X）catalysts were prepared from glucose,aniline and Fe Pc by hydrothermal,impregnation and calcination methods,which were characterized by FE-SEM,TEM,XRD,XPS.The Fe NC-CA-500 catalyst coupled with PMS could achieve almost 100%removal rate of 4-CP in 18 min and could selectively remove multiple aromatic compounds with different substituents.The catalytic efficiency of Fe NC-CA-500/PMS system was significantly better than that of Fe-NC/PMS system under the same reaction conditions,indicating that the highly-dispersed iron active sites was more conducive to the improvement of catalytic activity.Based on the EPR and a series of control experiments,we confirmed that the nonradical pathway via the electrons transfer between PMS and 4-CP was dominant while the generated reactive oxygen species（ROS）played a relatively small roles in4-CP removal.The single-atom iron and nitrogen co-doped hollow carbon microsphere loaded g-C3N4 catalyst（HFe NC-g-C3N4）was prepared by a facile cascade anchoring strategy using polystyrene as the hard template,iron phthalocyanine,polydopamine and urea as the Fe,N and C precursor,which was characterized by TEM,XRD,HAADF-STEM.The HFe NC-g-C3N4 catalyst with well-dispersed single-atom Fe-Nxactive sites could efficiently activate PMS and achieved almost 100%removal of4-CP in 5 min,and the catalytic efficiency was significantly improved with the reaction rate constant(1.663 min-1)being 5 times higher than that of Fe NC-CA-500/PMS system(0.3313 min-1).The mechanism of O2·-dominated radical combined with nonradical 1O2 pathway was confirmed by quenching experiments and EPR analysis. |
