Preparation Of Graphene Based Composite And Its Adsorption Studies For Heavy Metal Ions

Graphene has become an issue in research of materials science andcondensed-matter physics since it was found in2004by Geim. With lots of carboxyl,hydroxyl and epoxy group in the surface of graphene oxide, it is easy to modifygraphene oxide in the surface, resulting with increasing attention in the application ofgraphene based composites. In view of the increasingly serious heavy metal pollution,these adsorbents as followed were prepared and their adsorption mechanism for heavymetal ions was studied.Graphene oxide(GO/EDA) modified ethylenediamine was prepared by reducinggraphene oxide (GO) with ethylenediamine (EDA), and characterized by Fouriertransform infrared spectra (FT-IR), thermogravimetric analysis (TGA), Raman spectra(Raman) and scanning electron microscope (SEM). The effects of media pH, adsorptiontime and initial metal ion concentration on adsorption capacity of GO/EDA for Pb(II),Cd(II), Cu(II) and Mn(II) had been investigated, and the adsorption kinetics andadsorption isotherm of the experiments were studied. The studies showed that theadsorption kinetic data could be well described by the Lagergren pseudo-second-orderequation, which was mainly chemisorption. Compared with Freundlich adsorptionmodel, the Langmuir adsorption model could better describe the adsorption behavior forheavy metal ions on GO/EDA. The adsorption capacity of GO/EDA for Pb(II) was413.22mg/g, which was far more than that of Cd(II), Cu(II) or Mn(II). The regenerationstudies for Pb(II) demonstrated that GO/EDA own regenerative ability and could berecycled for further use.Meanwhile, the effects of flow speed, height of adsorbent-bed and initialconcentration of Pb(II) and Cd(II) on adsorption properties of GO/EDAwere studiedunder dynamic condition and the height of adsorbent bed and the breakthrough timewere linear fitted by the Bed-Depth-Services Time (BDST) model. The results showedthat the breakthrough time shortened and removal rate decreased with the increase offlow speed and the initial concentration of Pb(II) and Cd(II), with the increase of heightof adsorbent bed, the breakthrough time lengthened, followed with the increase ofremoval rate. Via the BDST model, the relationship between the adsorbent-bed heightand the breakthrough time could be well districted accurately, and the breakthroughtime for new initial concentration of Pb(II) and Cd(II) solution could be predicted, forwhich the errors were below5%.Polyamidoamine dendrimers grafted graphene oxide (GO/tPAMAMs) wereprepared via grafting to methods, and characterized by FT-IR, TGA, Raman and SEM.The effects of media pH, adsorption time and initial metal ion concentration onadsorption capacity for Pb(II), Cd(II), Cu(II) and Mn(II) toward GO/tPAMAMs hadbeen investigated, and the adsorption kinetics and adsorption isotherm were studied.The adsorption process for the heavy metal ions toward GO/tPAMAMs composites can be explained with pseudo-second-order type kinetic model, which was based on theassumption that the rate-determining step is a chemical adsorption. The adsorption of allthe metal ions on GO/tPAMAMs composites fits the Langmuir equation well. Themaximum adsorption capacity of GO/tPAMAMs composites for Pb(II) was found to be568.18mg/g, which was higher than that for Cd(II), Cu(II) or Mn(II).In addition, PAMAMs grafted graphene oxide (GO/fPAMAMs) were prepared viagrafting from methods, and characterized by FT-IR, TGA, Raman and SEM. The effectsof media pH, adsorption time and initial metal ion concentration on adsorption capacityfor Pb(II), Cd(II), Cu(II) and Ni(II) toward GO/fPAMAMs had been investigated, andthe adsorption kinetics and adsorption isotherm of the experiments were analyzed anddiscussed. The adsorption process for the heavy metal ions for GO/fPAMAMscomposites can be explained with pseudo-second-order type kinetic model, which wasbased on the assumption that the rate-determining step was a chemical adsorption. Theadsorption of all the metal ions on GO/fPAMAMs composites fits the Langmuirequation well.GO/EDA, GO/tPAMAMs and GO/fPAMAMs were prepared and the adsorptionmechanism for heavy metal ions was studied, which has laid a good theoretical basis forthe treatment of wastewater containing heavy metal ions.