Investigation On Adsorption Of P-nitrophenol On Graphene-basesd Materials

Due to the unique physical and chemical properties,graphene based materials have been widely studied as sensors and adsorbents.Based on the surface effects and quantum size effect,graphene based materials have higher effection on adsorption so as the sensitivities and response speed.So graphene based materials are promising sensors for toxic pollutants' detection.P-nitrophenol,as one of high toxic pollutants,has attracts more and more researchers.Some researchers have designed electrochemical sensors and solid-phase microextraction coatings based on graphene based materials for p-NP's detection.but the interaction between p-NP molecule and graphene is not very clear.Therefore,it is very meaningful to take a systematic investigation about the adsorption of p-NP molecule on graphene based materials' surface and their interactions.In this thesis,we combined adsorption experiments and quantum chemistry calculation to investigate p-NP molecule's adsorption behaviors and interactions on perfect graphene,defected graphene and modified graphene through experimental observation,calculation of adsorption energy,analysis of electronic density,population and electronic static potential.The thesis contains the following three parts:1.Graphene oxide(GO)was prepared by modified Hummers method and reduced graphene oxide(RGO)was prepared using hydrazine hydrate as reducing agent.Then we studied the adsorption behaviors of p-NP on GO and RGO.TEM,Raman spectra,XPS,FT-IR were used to systematically characterize the structure of GO and RGO.Results of characterization showed that the reduction process effectively reduced the content of oxygen groups and carbon atoms restored from sp3 hybrid to sp2 hybrid.Results of adsorption experiment showed that the adsorption behaviors on two adsorbents were all influenced by pH.Under pH 6.0 and 293 K,the adsorption equilibrium of p-NP on GO was reached within 50 min.Adsorption kinetics followed the pseudo-second-order model and adsorption isotherms was well fitted by the Freundlich model.The maximum adsorption capacity of GO for p-NP was 35.10 mg/g.The adsorption equilibrium of adsorption of p-NP on RGO was also reached within 50 min.Adsorption kinetics followed the pseudo-second-order model and adsorption isotherms was well fitted by the Langmuir model.The maximum adsorption capacity of RGO for p-NP was 29.94 mg/g.FT-IR analysis showed that for the adsorption of p-NP on GO,adsorption affinity was mainly derived from hydrogen bonds while for the adsorption of p-NP on RGO,adsorption affinity was mainly derived from ?-? interaction.2.By using DFT method,we studied the adsorption of p-NP on perfect graphene and intrinsic defected graphene's surfaces.Calculation results showed that the adsorption of p-NP on perfect graphene and SW defected graphene were physical adsorption and n-n interactions was the main adsorption affinity.However,the adsorption of p-NP on SV defected graphene was chemical adsorption and new formed C…H…O chemical bond was the main adsorption affinity.Introduction of these two kinds of defect was beneficial for p-NP adsorption and SV defected graphene had potential application value in degradation of p-NP.3.By using DFT method,we studied the adsorption of p-NP on modified graphene's surfaces.Simulation result showed that the main adsorption affinity of adsorption of p-NP on oxygen containing groups modified graphene was hydrogen bond.Introduction of-COOH,-OH on plane and epoxy was beneficial for p-NP adsorption while-OH on edge was inactive for p-NP adsorption.Simulation result of p-NP adsorption on N and B doped graphene showed that electrostatic interaction and ?-? interactions was the main adsorption affinity and introduction of B and N atom was beneficial for p-NP adsorption with.