The Construction Of Metal Carbon Composites And The Degradation Of Phenolic Contaminants By Activated Peroxymonosulfate

Among various refractory organic contaminants,phenolic compounds,as typical protoplasmic organic poisons which are toxic to most living things,have been widely concerned in the field of water treatment.Quantities of phenolic compounds in water environment,which are hostile and stubborn to be consumed by natural ecosystems.Extensive utilization and feeble treatment of phenolic compounds have caused a series of eco-environment and health risks.There is an urgent need for efficient treatment technology of phenolic compounds.Up till now,the permonosulfate based advanced oxidation processes(PMS-AOPs)witnessed an unprecedented booming scene in phenolic compounds treatment process owing to its high applicability and effectiveness.Triggering PMS activation to produce active oxidizing species(ROS)is the key factor in PMS-driven purification of phenolic wastewater.In the past few years,the supported transition metal catalysts have been developed to one of the research hotspots in the field of PMS-based heterogeneous catalysis since the supported transition metal catalysts were up-and-coming candidate with great activation performance and well controlled metal ions leakage problems.The purpose of this study is to construct environment-friendly metal carbon composites for PMS activation and phenol-containing water purification.The study results of this paper include the following three parts:(1)Three hierarchical porous graphitized biochar named C800-1,C800-2,and C800-3with increased iron deposition amount,decreased graphitized degree,and gradually destroyed graphitized carbon layers,respectively,were prepared using potassium ferrate as activator and corn straw as biomass.C800-1,C800-2,and C800-3 exhibited much different bisphenol A(BPA)degradation effects in presence of peroxymonosulfate among which C800-3 owned the best catalytic performance.For the degradation mechanism,the dominant role of the electron transfer pathway was gradually replaced by the SO4·– pathway with the increase of iron amount and the destruction of graphitized carbon layers.This work would provide a simple and feasible method,namely changing the ratio of potassium ferrate and biochar,to manipulate the radical and nonradical degradation pathway in PMS-based organic wastewater purification.(2)A convenient and efficient method to fabricate isolated Fe single-atom catalysts deposited on Myriophyllum aquaticum-based biochar(ISA-Fe/MC)is reported for PMS-based organics degradation.Firstly,the Fe nanoparticles anchored on the hierarchical porous graphitized biochar(nano-Fe/MC)can be obtained by utilizing K2 Fe O4 as a synchronous activation and graphitization agent.Subsequently,ISA-Fe/MC was achieved by HCl etching of nano-Fe/MC to remove the excess Fe nanoparticles.Compared with nano-Fe/MC,ISA-Fe/MC demonstrated outperformed catalytic capacity towards PMS activation for phenol degradation.The combination of super-high surface area,hierarchical porous structure,graphitization structure,and atomically dispersed Fe species should be responsible for prominent catalytic oxidation ability and outstanding resistance to common anions and humic acid.Based on the chemical scavengers,electron paramagnetic resonance(EPR)experiments,and electrochemistry tests,the SO4·– dominated radical degradation pathway for nano-Fe/MC and electron transfer reigned non-radical degradation pathway for ISA-Fe/MC was revealed.In contrast to nano-Fe/MC,density functional theory calculations demonstrated the enhanced density of states around Fermi level in ISA-Fe/MC meaning the increased catalytic performance and more electron transfer between single-atom Fe to adjacent graphitic C and N which could serve as electron transfer channel for PMS activation.(3)A family of graphene-based activators including reduced graphene oxide(RGO),nitrogen doped reduced graphene oxide(NRGO),zero-valent manganese loaded reduced graphene oxide(Mn-RGO)and zero-valent manganese loaded N-doped reduced graphene oxide(Mn-NRGO)were fabricated to activate PMS for BPA degradation.A significant synergistic effect between loaded manganese nano-particles(Mn-NPs)and doped N was revealed by comparing the apparent reaction rate constants with about 12.4,7.6 and10.5-folds enhancement when compared Mn-NRGO with RGO,NRGO,Mn-RGO,respectively.By integrating the results of chemical scavenger experiment,EPR test,galvanic oxidation process,PMS stoichiometric efficiency,linear sweep voltammetry and in-situ Raman spectrum,a predominant outer-sphere catalyst-PMS complexes mediated electron transfer pathway was uncovered.Based on kinetic studies,the specific contribution of synergistic effect was quantified to be at least 70%.The calculated Fermi level advanced by 0.03 e V in Mn-NG compared with that in NG,demonstrating that Mn-NG is more liable to donate electrons to PMS.The Eads and l O-O results pointed out that synergistic effect between Mn-NPs and doped N relied on the intimate affinity between Mn-NPs and HSO5–which triggered more uneven distribution of charge on the whole carbon sheets,and more adsorption of HSO5– on carbon framework.These newly created adsorption consequently reinforcing the formation of catalyst-PMS complexes and the elevation of mediated electron transfer pathway.Overall,this work provides a comprehensive and definite insight of the synergistic effect between loaded Mn-NPs and doped-N on carbon materials for promoting PMS activation to degrade organics.