Synthesis Of Fe0/Fe₃O₄@PC And Its Application In Persulfate Activation And Sulfamethoxazole Degradation

The sulfa antibiotic wastewater has poor biodegradability and cannot be completely removed by conventional sewage treatment processes.The advanced oxidation technology（SR-AOPs）based on sulfate radicals（SO₄·^-）has proven to be an ideal choice for the treatment of antibiotic wastewater.Fe-based materials are widely used as persulfate activation catalysts in SR-AOPs technology due to their rich reserves,environmental protection and magnetic recyclability.Recent studies have shown that the outer carbon shell of the carbon-coated iron catalyst（Fe@C）can effectively inhibit the agglomeration of the catalyst and reduce the leaching of metal ions.At the same time,the abundant functional groups on the surface of the carbon shell can also directly activate the persulfate.Based on this,this thesis uses Fe-containing paraffin combustion method to prepare a carbon-coated iron catalyst（Fe⁰/Fe₃O₄@PC）,and use it to activate monopersulfate（PMS）to degrade sulfamethoxazole（SMX）.The main research conclusions are as follows:（1）The effect of heat-treatment temperature on the crystal structure,pore characteristics,and surface chemical composition of the catalysts was investigated.Experiments have found that Fe⁰/Fe₃O₄@PC catalysts are composed of graphite carbon,Fe₃O₄ and Fe⁰;As the heat-treatment temperature increases from 500 ℃ to 900 ℃,the specific surface area(S_BET)and pore volume(V_Total)first increase and then decrease.Fe⁰/Fe₃O₄@PC-700 exhibits the largest S_BET（86.264 m²/g）and V_Total（0.2294 cm³/g）;There are oxygen-containing groups such as C=O,C-O,-COOH and Fe-O on the catalyst surface,among which Fe⁰/Fe₃O₄@PC-700 shows the highest surface C=O percentage,reaching 27.2%.The scanning electron microscope（SEM）characterization found that that Fe⁰/Fe₃O₄@PC-700 is granular with a particle size of 30～50nm.（2）The Fe⁰/Fe₃O₄@PC-700 catalyst obtained by heat treatment at 700 ℃ showed the highest PMS activation and SMX degradation activity.The optimal SMX degradation conditions in Fe⁰/Fe₃O₄@PC-700/PMS system are:catalyst dosage 0.2 g/L,peroxymonosulfate（PMS）0.5 m M,and initial p H 5.0,and SMX with an initial concentration of 10 mg/L was completely degraded within 20 minutes,with a mineralization percentage of 45.16%under this conditions.Among the common inorganic anions in natural waters,H₂PO₄^-,HCO₃^-and Humic acid（HA）had the most significant impact on the degradation of SMX.The natural organic matter in tap water,lake water and wetland water samples had a greater impact on the removal rate of SMX,which reduced the removal rate of SMX to 87.8%,67.0%and 51.8%,respectively.In addition,Fe⁰/Fe₃O₄@PC-700 has an excellent structural stability.After five cycles,the degradation rate of SMX still reached at 85%,and the total Fe content retained on the catalyst surface was as high as 99.73%.Moreover,the activity of the catalyst can be almost completely restored after heating at 700 ℃ for 80 min.（3）Both the≡Fe（II）of the exposed Fe₃O₄ particles and the arbonyl（C=O）of the carbon shell on the surface of the Fe⁰/Fe₃O₄@PC-700 catalyst activated the PMS to generate SO₄·^-,·OH,O₂·^-and ¹O₂.Among them,the non-radical pathway mediated by ¹O₂contributes the most to the degradation of SMX in the Fe⁰/Fe₃O₄@PC-700/PMS system.The Fe⁰ in the catalyst can promote the cycling of Fe（Ⅱ）/Fe（Ⅲ）and improve the catalytic activation efficiency of PMS.The characterized by liquid chromatography-mass spectrometry（LC-MS）shown that SMX might be degraded in the Fe⁰/Fe₃O₄@PC-700/PMS system in four ways,resulting in a total of twelve major degradation intermediates.