Functionalized Graphene And COFs Are Used For The Removal And Detection Of Hg And Pb In Water

With the development of science and technology,high-pollution industries such as industry and mining not only bring material prosperity to humans,but also bring snake in the grass of heavy metal pollution to humans.Therefore,the goal of clearing the hazards of heavy metals and treating heavy metal pollution has put forward the requirements for the development of heavy metal detection methods and removal methods.In this paper,the following two studies were carried out based on the above requirements:1)Direct synthesis of directly-thiolated graphene and it was used in the removal of mercury and lead in water.Firstly,the modified Hummers method was used to prepare graphene oxide.The introduction of hydrophilic groups into graphene solves the problem of graphene's dispersibility in water.Then,the graphene oxide is treated with hydrobromic acid to activate the hydroxyl groups at the edge of the graphene sheet and the epoxy group at the center of the sheet to form brominated Partial reduction of graphene oxide.Finally,thiourea with a nucleophilic sulfur reaction center is hydrolyzed under the action of an alkali with the bromine group on the partially reduced graphene oxide to form directly-thiolated graphene.Compared with other methods,the modified graphene synthesized by this method not only introduces active sites at the edge of the graphene sheet,but also introduces active sites in the middle of the sheet.Hence,the adsorption capacity of the material was increased.In this study,technical methods of SEM,TEM,EDS,XPS were used to characterize the directly-thiolated graphene,which proves the correctness and feasibility of the strategy in this study.The effect of pH and coexisting ion between directly-thiolated graphene and Hg2+ or Pb2+ were investigated and the result suggested that pH=6 was the best adsorption conditions of directly-thiolated graphene.The adsorption kinetics experiment shows that the adsorption behavior between directly-thiolated graphene and Hg2+ or Pb2+ belongs to chemical adsorption,which is more in line with pseudo second order kinetic model.Adsorption isotherm experiments show that the maximum adsorption capacity of directly-thiolated graphene is 143.9 mg g-1 for Hg2+ and 118.2 mg g-1 for Pb2+,respectively.The cycling experiment shows that directly-thiolated graphene still holds a recovery rate of over 85%after 4 times of regenerations2)Fe3O4@TpBD shell-core magnetic nanospheres were synthesized by in-situ growth method,and simple absorption was used to fix dithizone on the surface and pores of TpBD shell to give Fe3O4@TpBD the ability of adsorption ability of mercury A magnetic solid phase extraction method(MSPE)based on Fe3O4@TpBD@D core-shell magnetic nanospheres was established and used for the analysis of morphological mercury in trace level by high performance liquid chromatography-inductively coupled plasma mass spectrometry(HPLC-ICP-MS)Scanning Electron Microscope(SEM),Transmission Electron Microscope(TEM),X-ray Photoelectron Spectroscopy(XPS),X-ray Diffraction(XRD)and Fourier-Transform Infrared Spectroscopy(FT-IR)were applied for the characterization of the adsorbents prepared.Parameters influencing the final effect,such as solvent type of dithizone,sample pH,extraction and elution time,interference ion,ionic strength,sample volume and eluent type was optimized.Under the optimized conditions,the limits of detection(LODs,38)of developed method were 4.4 and 1.3 ng L-1 for inorganic mercury(IHg)and methylmercury(MeHg).The enrichment factors for IHg and MeHg were 182 and 200,respectively.The standard deviation(<4.5%)and correlation coefficient(?0.994)indicated that the developed method had high credibility and accuracy.The developed method was successfully applied for analyzing IHg and MeHg in water samples,including tap water,ground water,surface water and sea water.