Preparation of cobalt-manganese co-doped metal-organic framework compound MIL-88B(Co-Mn)for activating peroxymonosulfate to degrade tetracycline
Objective Due to the complex molecular structure of antibiotics,their recalcitrance to degradation poses a significantenvironmental threat,harmful to human life and safety.More seriously,this accumulation also has a crucial impact on human survival and the sustainable development of the ecological environment.Advanced oxidation technology based on sulfate radical has been used as an effective treatment option for the removal of antibiotics.In recent years,the use of metal-organic frameworks(MOFs)to cata-lyze peroxymonosulfate has attracted extensive attention from researchers.Importantly,the catalyst prepared by pre-modification or post-modification of MOFs-based material exhibit key features,includinga porous structure,multiple active sites and good stability.Therefore,a high-efficiency solid catalyst,Co-Mn co-doped metal-organic framework compounds,is studied in this paper for the efficient degradation of TC in water.Methods In this paper,Co-doped metal-organic framework compound(MIL-88B(Co-Mn))is prepared by solvothermal meth-od.Firstly,Co(NO3)26H2O and Mn(NO3)24H2O with a total mass of 320 mg were dissolved in the DMF solution containing terephthalic acid according to different molar ratios and the mixture was stirred for 30 minutes;Then,the resultant light red solu-tion was reacted in a muffle furnace at 160 ℃ for 24 h.After cooling down,the obtained product was washed three times with DMF,methanol and deionized water respectively and dried in an oven at 60 ℃ for 12 h.Finally,catalysts with different molar ratios of cobalt and manganese were synthesized.Results and Discussion X-ray diffraction(XRD)pattern of MIL-88B(Cox-Mn1-x)shows the similar diffraction mode with that of MIL-88B,in which distinct characteristic peaks appear at around 14°,16°,18°,27° and 45° respectively.Moreover,the characteristic peaks of MIL-88B(Cox-Mn1-x)with different composite proportions are consistent with those of MIL-88B XRD pattern,indicating that the catalysts are successfully prepared.The micro-morphology and element distribution of the samples are revealed by scanning electron microscopy.MIL-88B(Cox-Mn1-x)materials all exhibit a relatively uniform and well-defined three-dimensional honeycomb structure.Meanwhile,element mapping images prove the distribution of Co,Mn,C and O elements in MIL-88B(Co0.6-Mn0 4)material,which further indicates the presence of cobalt-manganese metal and carbon oxygen elements in the catalyst.To determine the valence state and surface element composition of the catalysts,the composition of MIL-88B(Co0.6-Mn0.4)is studied by X-ray photoelectron spectroscopy(XPS).Elements such as Co,Mn,C,and O are detected in the full spectrum of MIL-88B(Co0.6-Mn0.4).In addition,the XPS spectra of Mn 2p and Co 2p are analyzed,confir-ming that in the MIL-88B(Co0 6-Mn0.4)catalyst,Co and Mn elements mainly exist in the form of Co2+,Co3+,Mn2+and Mn3+.The introduction of Co and Mn bimetallic active sites in MIL-88B can further improve the electron transfer efficiency of the catalytic PMS process,thereby promotes the formation of SO4-,ultimately improving the removal performance of pollutants.The catalytic performance of the catalyst is appraised through TC elimination over MIL-88B(Co0 6-Mn0 4)in the presence of PMS.Apparently,the prepared MIL-88B(Co0.6-Mn0.4)catalyst in the experiment exhibits excellent catalytic performance.After the reaction,the degradation rate of TC in the MIL-88B(Co0.6-Mn0.4)-PMS systems reaches 91.2％.Furthermore,the effect of different molar ratio cobalt-manganese doping amount on the performance of the catalyst is investigated,and the experimental conditions are optimized.The results shows that when the molar ratio of Co(NO3)2·6H2O and Mn(NO3)2·4H2O is 3∶2,pH=5,the TC mass concentration is 10 mg·L-1,the catalyst mass concentration is 20 mg·L-1,and the molar mass of peroxymonosulfate is 2 mmol·L-1,the removal rate of TC can reach more than 94％.Meanwhile,the stability of the catalyst is evaluated through cycling experiments.After the fourth cycle,the MIL-88B(Co-Mn)catalyst maintains approximately 90％of its original catalytic performance,indicating the favorable durability of MIL-88B(Co-Mn).Conclusion In this study,a cobalt-manganese co-doped metal-organic framework compound MIL-88B(Co0.6-Mn0.4)is prepared by the solvothermal method.And it is used to remarkably catalyze the removal of tetracycline from water by peroxymonosulfate.The reason is that the appropriate ratio of cobalt-manganese atoms to metals can significantly enhance the bimetallic synergy of metal-organic framework materials,thereby improving the ability of catalysts to activate peroxymonosulfate.Based on cycling experiments,the removal rate of TC can still reach 90.6％,which proves that MIL-88B(Co0.6-Mn0.4)is a new catalyst with high efficiency and reusability.This work also directs a feasible technology for treating actual antibiotic wastewater,and effectively removing TC from water by catalyzing peroxymonosulfate.
万方数据
维普
