Magnetic Graphene Oxide Grafted Polyamidoamine For The Adsorption Of Heavy Metal Ions

With the rapid development of industrialization,heavy metal ions pollution in water has become a serious environmental problem.Using graphene-based composites as a kind of adsorbent to remove harmful heavy metal ions in wastewater has been developed to a safe,convenient and efficient water treatment technology in recent years.In this study,using amino modified magnetic graphene oxide nanocomposites(MGO-NH2)as carriers,ethylenediamine and methyl acrylate as functional monomer,different generations of polyamidoamine dendrimers functionalized magnetic graphene oxide(MGO-PAMAM),up to generation 4.0,were synthesized via step by step growth chemical grafting approach and magnetic separation technology.The synthesized MGO-PAMAM were characterized by transmission electron microscopy(TEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),elemental analysis,X-ray photoelectron spectroscopy(XPS),thermogravimetric analysis(TGA),vibrating sample magnetomet er(VSM)and Zeta potential analysis.The adsorption properties of the obtained products for Hg(II),Ag(I)and Pb(II)in aqueous solution were investigated by batch experiments.The effects of PAMAM generations,initial Hg(II),Ag(I)and Pb(II)concentration,solution p H,contact time and temperature on the adsorption property of MGO-PAMAM were investigated in details.Simultaneously,the pseudo-first-order,pseudo-second order and intra-particle diffusion kinetic models were employed to study the adsorption kinetics,the Langmuir,Freundlich,Temkin and Dubinin-Radushkevich isotherm models were used to evaluate the isothermal adsorption process,the adsorption mechanism were also investigated.The results showed that the different generations of polyamidoam ine dendrimers functionalized magnetic graphene oxide,up to generation 4.0,were successfully synthesized.MGO-PAMAM with generation 3.0 of dendrimers(MGO-PAMAM-G3.0)has the maximum adsorption capacity to Hg(II)(113.71 mg·g-1),Ag(I)(52.06 mg·g-1)and Pb(II)(36.96 mg·g-1),respectively.The adsorption process of MGO-PAMAM-G3.0 for Hg(II),Ag(I)and Pb(II)were all well described by the pseudo-second-order kinetics model and the Langmuir isotherm model.The adsorption process was mainly considered as a monolayer chemical adsorption.The Hg(II)and Ag(I)adsorbed on the surface of MGO-PAMAM-G3.0 were reduced to Hg(I)and element Ag in the adsorption process.The Pb(II)was only complexed with amino functional groups on the surface of MGO-PAMAM-G3.0.In addition,the MGO-PAMAM possesses a good magnetic performance and its saturation magnetization can satisfy the requirement of the solid-liquid separation after adsorption.