Metal-Organic Framework-Derived Ironcobalt Oxides Activated Persulfate For Degradation Of Ciprofloxacin In Water

In recent years,with people’s increasing environmental awareness,antibiotic pollutants have gradually attracted the attention of scholars for their low concentration in water,wide variety and toxicity.Persulfate is widely used in practical water treatment due to its stable performance,low price,and environmental friendliness.However,due to the selective oxidation of persulfate alone and its catalytic oxidation,its ability to oxidize refractory organic pollutants in water is limited.To solve the above problems of persulfate-catalyzed oxidation,this study prepared metal-organic framework-derived iron-cobalt oxide（FeCo-MOF-600）materials as catalysts,constructed FeCo-MOF-600catalyst/persulfate system（C-PMS）.Then it systematically evaluated the synergistic effect between FeCo-MOF-600 catalyst and persulfate,and investigated the removal efficiency of the system for typical refractory organic pollutants such as ciprofloxacin.Finally,it revealed the inherent reaction mechanism of the system and explored the main pathway of pollutant degradation,and explored the potential application value of the system.This study could provide some reference and guidance for future researches based on persulfate advanced oxidation.The main research contents and conclusions of this thesis are shown as follows:（1）This study prepared iron-cobalt-containing metal-organic frameworks（FeCo-MOFs）by hydrothermal synthesis as precursors.Then it prepared iron-cobalt oxide catalyst（FeCo-MOF-600）was by calcining the precursor in a tube furnace at 600°C by the template method.Finally,it characterized the catalyst（FeCo-MOF-600）material before and after the reaction by Scanning electron microscope（SEM）,X-ray powder diffractometer（XRD）,X-ray photoelectron spectroscopy（XPS）,Fourier transform infrared spectroscopy（FT-IR）,specific surface area and porosity analyzer（BET）.The results show that the iron-cobalt oxide catalyst prepared by the template method is granular and has a multi-layer porous structure.The dispersed doping of Feand Co is realized,and functional groups such as C-O,N-C=N and Co-N_x are dispersed on the surface of the material.The morphology and structure of the catalyst material did not change significantly before and after use,the specific surface area and the uniformity of pore size distribution are both lower than before use.（2）This study evaluated the degradation and mineralization performance for the target contaminant ciprofloxacin（CIP）of persulfate alone（PMS）,electrochemical alone（E）,FeCo-MOF-600 catalyst alone（C）,and electro/persulfate system（E-PMS）and FeCo-MOF-600 catalyst/persulfate system（C-PMS）.The results showed that there was a good synergy between FeCo-MOF-600 catalyst and persulfate,whit SI=5.614.The C-PMS process had a synergetic effect for CIP removal,degrading 100%CIP in 15 min.And its reaction rate(0.193 min^-1)was significantly higher than the other comparison process.（3）Increasing the dosage of catalyst and oxidant could promote the removal efficiency of this process.But when the operating conditions reached the optimum,further increasing the dosage of catalyst and oxidant had a little positive effect on the efficiency of this process.Experiments found that bicarbonate ions（HCO₃^-）,sulfate ions(SO₄^2-),nitrate ions（NO₃^-）and chloride ions（Cl^-）four anions,all of which will inhibit the degradation of ciprofloxacin by FeCo-MOF-600 catalyst/persulfate system（C-PMS）to varying degrees.But it could still keep a good removal efficiency.The results confirmed that FeCo-MOF-600 catalyst/persulfate system（C-PMS）has certain potential application value.（4）There are mainly reactive oxygen species such as hydroxyl radical（·OH）,sulfate radical(SO₄^·-),superoxide anion(O₂^·-)and singlet oxygen（¹O₂）in FeCo-MOF-600catalyst/persulfate system（C-PMS）,which further strengthens the catalytic reaction ability of the system.By detecting and analyzing the intermediate products of ciprofloxacin in FeCo-MOF-600 catalyst/persulfate system（C-PMS）,we found that there were two possible degradation pathways for CIP degradation.And the CIP could be degraded into the small molecular organics or inorganics by dehydrogenation,hydroxylation,C-N bond cleavage,and ring opening.