Dispersed Fe-N₄ Sites Embedded In Carbon-doped Porous Boron Nitride For Highly Efficient Catalytic Advanced Oxidation Processes

With the rapid development of industrialization and urbanization,organic pollutants discharged from industrial and domestic wastewater have caused a serious threat to ecosystems and human health.Compared with conventional technologies,advanced oxidation processes(AOPs)can effectively realize the rapid degradation and mineralization of persistent organic pollutants(POPs)from wastewater.Single-atom catalysts(SACs)are emerging as potential alternatives in the field of wastewater purification because of their utmost atom utilization and excellent catalytic activity.In recent years,SACs have been widely used in Fenton systems for activating oxidants to produce highly reactive oxygen species,which finally act on organic pollutants and achieve their decomposition and mineralization.In this thesis,we successfully synthesized series of dispersed transition metal M-N4 sites embedded in carbon-doped porous boron nitride and further applied them to activate peroxymonosulfate(PMS)for degradation of organic pollutants from wastewater.The specific research are listed as follows:(1)We firstly prepared metallophthalocyanine complexes using tetracyanobenzene(TCNB)as organic linker and transition metal ions(Cu2+,Fe3+or Co2+)as nodes via an efficient and mild microwave synthesis method,followed by heating recrystallization with boric acid,urea and F127,and then successfully immobilized M in carbon-doped porous boron nitride(BCN)by high temperature calcination strategy through M-N4 coordination structure.It was found that the synthesized catalyst activities trends followed the order Fe-N4/BCN>Co-N4/BCN>Cu-N4/BCN>BCN,and Fe-N4/BCN presented the highest kinetic value with 0.1457 min-1.Furthermore,the structure and physicochemical properties of Fe-N4/BCN were investigated by a series of characterization techniques.The results showed that the porous Fe-N4/BCN exhibited a large specific surface area(531 m2/g),which is approximately 5.5 times higher than that of BCN.Notably,the X-ray photoelectron spectroscopy(XPS)results demonstrated that single Fe atoms were firmly coordinated with four N atoms in the BCN structure.(2)Selecting Bisphenol A(BPA)as the target organic pollutant,we further evaluated the catalytic performance of Fe-N4/BCN in activating PMS to degrade BP A.The results showed that Fe-N4/BCN exhibited superior catalytic performance in both activating PMS and degrading BP A,and only 0.1 g/L catalyst was required to achieve 100%removal of 20 ppm BPA within 30 min.The effect of different reaction conditions on the rate of BPA degradation was investigated by a series of batch catalysis experiments.In addition,free radical quenching experiments demonstrated that SO4-·and ·OH were the main active species in the free radical pathway during the degradation of BPA.The degradation rate of BPA maintained high level above 91.8%after five cycles,displaying the high stability of Fe-N4/BCN.We prepared a series of single-atom catalysts with abundant M-N4 sites and applied them to the efficient activation of PMS for the degradation of organic pollutants from water.The synergistic effect between the high specific surface area and the large number of active sites significantly improved the PMS activation and pollutant degradation efficiency.It provided a general approach for the future rational design of single-atom catalysts to improve the catalytic activity of Fenton-like systems.