Migration Control Of Charge Carriers On Metal Semiconductors For Antibiotics Degradation

Antibiotics have widely entered water environment due to their excessive consumption and discharge,triggering the emergence of drug-resistant genes and causing serious clean water shortages and water safety issues.Metal semiconductor-based photocatalytic technology can generate oxidizing holes（h⁺）and reducing electrons（e^-）,which can be used to oxidize water to generate hydroxyl radicals（·OH）and activate persulfate to generate sulfate radicals（·SO₄^-）,respectively.Thus,improving the utilization of charge carriers（h⁺and e^-）is a crucial part of advanced oxidation technology.In this thesis,the applications of photocatalysis and light-assisted persulfate activation technologies for the degradation of antibiotics are strengthened by regulating the migration of carriers,while the mechanisms are further explored.The main research contents and experimental results are as follows:1.Femtosecond time-resolved diffuse reflectance spectroscopy was used to study the charge carrier dynamics of facet engineered Ag₃PO₄ during the photodegradation of antibiotics.The results show that the antibiotic degradation efficiency of Ag₃PO₄ tetrahedrons with{111}crystal planes was 1.8 times that of Ag₃PO₄ cubes with{100}crystal planes due to the higher hole mobility of Ag₃PO₄ tetrahedrons.Therefore,the hole mobility of photocatalysts can be promoted by adjusting their facet structures,thereby improving the efficiency of water treatment.2.Novel 3D Co₃Mn-layered double hydroxide aerogel（Co₃Mn-LDH/r GA）was synthesized for peroxymonosulfate（PMS）activation to achieve continuous and efficient degradation of metronidazole with the assistance of visible light.The transformation of Co²⁺/Mn³⁺to Co³⁺/Mn⁴⁺on the surface of the catalyst and the visible light-generated e^-co-contributed to the boosted production of free e^-,which was quickly transferred through r GA as abundant e^-transfer channels to react with PMS,resulting in the enhanced first-order kinetic constant of 0.28 min^-1.Moreover,an outstanding reusability of Co₃Mn-LDH/r GA/PMS/Vis system consolidated in cyclic equipment was found,in which metronidazole could be efficiently and continuously removed for more than 10 cycles.3.The degradation rates of seleted nitroimidazoles antibiotics were found to vary with their molecular structures during Co₃Mn-layered double hydroxide（Co₃Mn-LDH）catalyzed PMS oxidation process.The degradation efficiency of secnidazole was determined to be the highest with a reaction rate of 0.24 min^–1,which was 3.6,2.3 and 1.8 times that of menidazole,metronidazole and ornidazole,respectively.Density functional theory calculation showed that the presence of electron-donating groups（–CH₃ and–OH）and the absence of electron-withdrawing atom（Cl）leaded to the richest active sites on the molecular structure of secnidazole,which thus contributed to its highest degradation efficiency.