The Removal Of Norfloxacin From Water By Carbonized Polydopamine-decorated G-C₃N₄ Activated Peroxymonosulfate

Norfloxacin（NOR）,one of the fluroquinolone antimicrobials,is widely used to treat respiratory,gastrointestinal,wound and other infections.Nowadays,antibiotics are frequently detected in the water environment,leading to potential risks to human health and the ecological environment.Peroxymonosulfate-based advanced oxidation processes（PMS-AOPs）were widely used in antibiotic-contaminated water environments because of their high catalytic activity,high removal efficiency,and technical simplicity.Meanwhile,carbonaceous materials with high specific surface area,more electron-rich functional groups and conjugatedπ-system are treated as more ideal types of catalysts.Therefore,This study will use carbonaceous materials as activators for PMS.The details of the work are as follows.（1）An efficient and simple method to modify graphitic carbon nitride（CN）was proposed,and the morphological characteristics and surface functional group types of CN and carbonized polydopamine-decorated g-C₃N₄（CP-700）were analyzed by scanning electron microscopy（SEM）,fourier transform infrared spectroscopy（FTIR）and X-ray photoelectron spectroscopy（XPS）.The results showed that CP-700 had larger specific surface area,higher graphitization,higher content of pyridinic nitrogen and carbonyl groups（C=O）,and exhibited ultrathin nanosheet morphology containing porous structure.（2）It was demonstrated that after the modification by polydopamine（PDA）,CP-700enhanced the activation of PMS and exhibited excellent degradation ability:95%NOR degradation rate was achieved within 20 min.And the impacts of initial p H of solution,contaminant concentration and water mitrix on the degradation ability of CP-700/PMS system were explored,as well as the reusability study of the material.The results showed that the CP-700/PMS system exhibited high tolerance to the solution p H and inorganic anions.（3）The CP-700/PMS system was not hindered by the radical(sulfate radical(SO₄^·-)and hydroxyl radical（·OH）)pathway by quenching experiments and electron paramagnetic resonance spectroscopy（EPR）analysis,and the non-radical pathway dominated by singlet oxygen（¹O₂）and electron transfer played a major role in NOR degradation.Based on semi-quantitative calculations,it was clear that there was a linear positive correlation between the carbonyl groups content and the reaction rate constant（R²=0.9922）,concluding that the C=O group was an important active site.The excellent electron transfer ability of CP-700 was evidenced by electrochemical techniques and the electron transfer pathway in the system was that PMS was adsorbed on the CP-700 surface to form metastable complex,and then the electron transfer between NOR and metastable complex was achieved.This study provided a feasible strategy for the design of metal-free carbonaceous catalyst activated PMS for the treatment of antibiotic-contaminated water bodies.