Preparation And Catalytic Performance Of Iron-basd Catalysts Supported By Activated Carbon Fibers

Advanced oxidation technology based on persulfate(PS)has become one of the most promising technologies in printing and dyeing wastewater treatment due to the strong oxidation and wide pH applicability.It is critical to activate PS and produce reactive oxygen species for wastewater treatment.Among methods of activating PS,transition metal activation method has been considered as an ideal method for PS activation owing to the mild reaction conditions and it doesn't need additional energy.However,the transition metal activation method still has drawbacks such as low catalytic efficiency and secondary pollution.It is of great significance to develop a catalyst with high catalytic efficiency and no secondary pollution.In this paper,activated carbon fibers(ACFs)with large specific surface area and good chemical stability was selected to combine with iron-based catalyst to prepare iron-based catalytic fibers.Using PS as the oxidant,dyes as the target pollutant,the catalytic ability of iron-based catalytic fibers was investigated.The paper focuses on the catalytic performance and repeatability of catalytic fiber,as well as reaction mechanism of PS activation.The main research contents are as follows:Iron oxalate(FeOxa)was supported on ACFs via a simple impregnation method,obtaining a heterogeneous catalyst(FeOxa@ACFs).The structure of FeOxa@ACFs was characterized by scanning electron microscope(SEM),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).Using PS as the oxidant,reactive brilliant red RR M-3BE as the target pollutant,The catalytic performance and reusability of FeOxa@ACFs were investigated,the effect of anions(Cl-?SO42-?NO3-?CO32-?HCI3-?H2PI4-)were also investigated in FeOxa@ACFs/PS system.The results indicated that FeOxa@ACFs could activate PS to achieve a removal rate of 96.8%for RR M-3BE within 20 min and the removal rate of the RR M-3BE could reach 95.4%after the fifth cycle of FeOxa@ACFs,suggesting that FeOxa@ACFs possessed good reusability.Moreover,multiple pollutants including methylene blue(MB),reactive red(X-3B),methyl orange(MO),acid red 1(AR1),acid orange 7(AO7),sulfadiazine(SD),ciprofloxacin(CIP)and Phenol could be effectively removed in FeOxa@ACFs/PS system.When the concentration of Cl-,SO42-and NO3-were less than 1 mM,there was no effect on the RR M-3BE removal.When the concentration of Cl-,SO42-and NO3-were more than 1 mM,which inhibited the catalytic reaction,while H2PO4-,CO32-and HCO3-had inhibitory effect on catalytic system.Electron paramagnetic resonance(EPR)technology combining with radical quenching agents such as methanol(MA)and tert-butanol(TBA)were used to study the catalytic mechanism.The results indicated that both hydroxyl(-OH)and sulfate(SO4·-)radicals were generated and SO4·-played a key role in FeOxa@ACFs/PS system.In order to further improve the catalytic activity of iron-based catalytic fibers,Fe3O4@ACFs was prepared by calcination method.Compared with the FeOxa@ACFs/PS system,Fe3O4@ACFs could activate PS to achieve a removal rate of 97.0%for RR M-3BE within 8 min and the reaction rate constants(0.46 min-1)was 2.7 times higher than that of FeOxa@ACFs/PS system(0.17 min-1).The removal rate of the RR M-3BE could reach 96.0%after the sixth cycle of Fe3O4@ACFs,indicating that Fe3O4@ACFs possessed good reusability.Furthermore,multiple pollutants including MB,X-3B,MO,AR1,AO7,Phenol,sulfadiazine(SD),sulfamethoxazole(SMX)and tetrachlorophenol(4-CP)could be effectively removed in Fe3O4@ACFs/PS system.Cl-and NO3-had little effect on Fe3O4@ACFs/PS system,while H2PO4-,SO42-,CO32-and HCO3-had inhibitory effect on catalytic system.Electron paramagnetic resonance(EPR)technology combining with radical quenching agents such as methanol(MA)and tert-butanol(TBA)were used to study the catalytic mechanism.The results indicated that both·OH and SO4·--were generated in Fe3O4@ACFs/PS system.