Study On The Adsorption And Photodegradation Of Fluoroquinolones By Nano Molybdenum Disulfide

Antibiotic residues in water exist as persistent contaminants and are harmful to our health and even damage the ecological balence.Unfortunately,it is quite difficult to remove these pharmaceutical compounds from water by traditional sewage treatment techniques.A graphene-like layered compound that named molybdenum disulfide(MoS₂)take many advantages such as the special layered structure,large specific surface area,high reactivity,adjustable band gap,absorption of visible light energy and excitation of electron-hole pairs,as well as excellent chemical stability and thermodynamic properties stability.Therefore,it is considered as a potential adsorbent and a photocatalyst to some antibiotics in aquatic environment and development for the treatment of water pollution caused by antibiotics.In this thesis,two kinds of nano-MoS₂with different morphologies were prepared by microfacies exfoliation method and hydrothermal method,respectively.Then,the adsorption performance of as-prepared MoS₂to fluoroquinolones was compared with lomefloxain(LOM)as a target pollutant.On basis of the result,the focus was placed on the adsorption and photocatalytic degradation of norfloxacin(NOR)by the flower-like MoS₂microspheres.The present work aims to provide some experimental basis for the removal of antibiotic residues in aquatic environment.This paper consists of four chapters:Chapter 1.The pollution and the treatments of antibiotics in aquatic environment are introduced.The research progress of nano molybdenum disulfide is summarized.Especially,the applications of nano-MoS₂as an adsorbent and a photocatalyst to remove pollutants from water environment are reviewed in detail.Chapter 2.Two kinds of nano-MoS₂with different morphologies were prepared by microfacies exfoliation method and hydrothermal method,respectively.The effects of p H,adsorption time and initial concentration of lomefloxacin solution on the adsorption were investigated with lomefloxacin as a target pollutant.The results showed that the adsorption equilibrium both in two cases could be achieved within 12h,and the adsorption data both could be well fitted by pseudo-second-order kinetics model and the Langmuir isotherm adsorption model.However,the flower-like MoS₂microspheres synthesized by the hydrothermal method showed a stronger adsorption capacity for lomefloxacin.Chapter 3.The adsorption kinetic and thermodynamics behavior of norfloxacin(NOR)by flower-like MoS₂microspheres were studied in this chapter.The effects of initial concentration of NOR,initial p H,temperature,adsorption time and ionic strength on the adsorption of norfloxacin solution were investigated in detail.The results showed that the maximum adsorption capacity was 182.2 mg·g^-1at 318K when the initial concentration of NOR solution was 100 mg·L^-1,the initial p H value was 6,and the adsorption time was 12 h.The adsorption data could be well fitted by the pseudo-second-order kinetics model and Langmuir isotherm adsorption model,and a spontaneous endothermic process was revealed by the calculated thermodynamic parameters.Chapter 4.The photocatalytic degradation of norfloxacin by the flower-like MoS₂microspheres was investigated under the optimized photocatalytic degradation conditions.The results showed that MoS₂has a potential capability of degrading NOR in a neutral or weak alkaline medium with the highest degradation efficiency of 72%.The fitting was performed by the first-order reaction kinetics.It was found that the maximum adsorption rate constant was 0.0121 min^-1when the initial p H value was 8.Finally,the possible photocatalytic degradation mechanism of NOR by nano-MoS₂was preliminary discussed,and the order of active species in the photodegradation process was:·O₂^->h⁺>·OH.