Controllable Preparation Of FeOOH-based Materials And Its Electrocatalytic Behavior On The Degradation Of Antibiotics And The Evolution Of Nitrogen

In order to solve the antibiotic pollution problems and the low activity of the electrocatalysts,four FeOOH-based materials have been synthesized by introducing of orange peel biochar,Mo,CQDs and W/S.In addition,metronidazole,tetracycline and levofloxacin have used as the model contaminants to evaluate the electro-degradation performance of the as?prepared Bio-FeOOH,1D-FeOOH@Mo,CQDs@FeOOH and WS2@FeOOH.Four optimal system are determined basic on the degradation performance of as-prepared material on target,which is including the degradation of tetracycline by Bio-FeOOH,the degradation of metronidazole by 1D-FeOOH@Mo,the degradation of levofloxacin by CQDs,@FeOOH and WS2@FeOOH.The degradation mechanism of the antibiotics and the transformation of inorganic N-products during the antibiotics degradation process have been fully investigated.Firstly.the stability,electrochemical active area and charge transfer resistance of the as-prepared materials were characterized by X-ray Diffraction,Transmission Electron Microscope.Atomic Force Microscope.Physical and Chemical Adsorption Apparatus.Cyclic Voltammetry,Electrochemical Impedance Spectroscopy and Linear Scanning Voltammetry.Then,the active radicals during antibiotics degradation process has been evaluated by radical quenching experiments and EPR spectrum.In addition,the degradation kinetics of antibiotic in four as-prepared systems were studied by the First order diffusion kinetics and the Second order diffusion kinetic equations.Finally,the degradation pathw-ay of the antibiotics and the transformation of inorganic N-products during the antibiotics degradation were studied by the Three Dimensional Fluorescence spectrum,Liquid Chromatography-Mass Spectrometry and Ultraviolet Visible spectrum.The main conclusions are as follows:(1)Controllable preparation of Bio-FeOOH and its catalysis behavior on the degradation of tetracycline.In this work,four FeOOH-based electrode with different structures have been synthesized by introducing the orange peel biochar.Characterization results showed that Bio-FeOOH-5 with a special three dimensional dendritic structure was achieved when the Bio/Fe material ratio is 5%.Bio-FeOOH-5 also revealed the lowest chlorine evolution voltage and charge transfer resistance,and its electrochemical active area is about 5 times bigger than Bare-FeOOH.Nearly 99.3%of the tetracycline was decomposed by Bio-FeOOH-5 electrode.The active radical detection results demonstrated HCIO is the main radical in degradation of tetracycline.Kinetic studies show that the as-prepared Bio-FeOOH-5 showed the highest korg and krad,which is about 6.1 and 3.1 times bigger than the Bare-FeOOH.In the tetracycline degradation process,HCIO first attacked the C-N bond of TCY for denitrification,and then attacked the benzene ring of TCY for ring opening reaction.When the degradation reaction reaches equilibrium,the yield of inorganic nitrogen product was 91.2%,which including 74.9%NH4+ and 25.1%N2.(2)An efficient metronidazole degradation system has been synthesized by 1D-FeOOH@Mo electrode.In this work,the 1D-FeOOH@Mo electrode was prepared by modified the 1D-FeOOH by Mo.Characterization results showed that Mo was adsorbed on 1D-FeOOH by lattice adsorption process.The specific surface area and electrochemical active area were improved about 2.0 and 5.7 times when Mo was adsorbed.Nearly 99.6%of the metronidazole was decomposed in 1D-FeOOH@Mo activating PMS in 30 min.The DFT theoretical calculation demonstrated that the adsorption energy of FeOOH on HSO5-could be reduced and the density of electron on electrode surface could be increased when introducing of Mo,which is benefited to SO4·-generation.In the degradation of metronidazole,the metronidazole was been decomposed by HO· by break the C-N bond on the branch chain of metronidazole and the C=N bond of the imidazole ring.When metronidazole were completely decomposed,the yield of inorganic nitrogen product was 20.8%.which including 62.9%NO3-and 27.8%N2.(3)In the degradation of levofloxacin system,four CQDs@FeOOH electrodes with different morphology and exposed facet was synthesized by combining using the CQDs as the structural regulator.Characterization results showed that the 3D CQDs@F-1 arrays with(110)exposed facets was successfully prepared w-hen the CQDs/Fe material ratio is 1%.Compared to raw FeOOH,the as-prepared CQDs@F-1 showed a higher specific surface area and electrochemical active area,which is about 3.0 and 2.3 times than the raw FeOOH.About 99.4%of levofloxacin could be decomposed by CQDs@F-1 when extending the reaction time to 80 min.Radicals quenching experiments and ESR analysis showed that approximately 82.4%of the degradation for levofloxacin was achieved by HO·.Characterization data and DFT calculation demonstrated that the highest HO· generation rate of the CQDs@F-1 anode was attributed to the moderate adsorption energy of the exposed(110)facets towards H2O molecule,which was responsible for promoting the generation of HO·.CQDs@F-1 also showed a higher the transfer coefficient than others.At the end of the degradation process,the yield of inorganic nitrogen product was 72.1%,and the main inorganic nitrogen product was NO3·,accounting for 98.2%of the total inorganic nitrogen products.(4)In order to achieve the efficient degradation of levofloxacin in surface water solution(without electrolytes),the levofloxacin piezo-degradation system was designed based on WS2@FeOOH material.For the first time,the WS2@FeOOH was synthesized by modified FeOOH by ball grinding.Characterization results showed that WS2@FeOOH has abundant single-layer and thin-layer structures,and its thin-layer edges are respectively composed of 52.5%type 1T and 47.5%type 2H WS2.The AFM results demonstrated that the surface potential WS2@FeOOH was 62.9 mV,which is 20 times bigger than FeOOH.Both oxygen radicals O21and O2·-were generated and took part in the LVX degradation,while O21 were more contributed to the levofloxacin degradation.Levofloxacin can only be transformed into intermediates,and cannot be completely decomposed into small molecular products.Only 0.65 mg/L of NO3-was produced during the degradation of levofloxacin,and the yield of inorganic nitrogen was 4.3%.In summary,metronidazole,tetracycline and levofloxacin have been efficiently removed based on the active electrocatalytic material design.The mechanism,kinetics and transformation of nitrogen of the antibiotic degradation process were both fully studied.This work not only provides an efficient method for antibiotic elimination,but also extends the possible application areas of electrochemical oxidation process.