| In this work,amino-functionalized nano-Fe3O4 magnetic polymer adsorbents(NH2-NMPs) have been synthesized.Well multidispersed paramagnetic Fe3O4 with an average diameter of～20 nm was firstly prepared via the improved chemical co-precipitation method,followed by co-polymerization with methyl methacrylate(MMA) and glycidylmethacrylate(GMA) via suspension polymerization to obtain epoxyl-functionalized nano-sized magnetic polymer (M-co-GMA-MMA).Finally,the epoxyl- groups of the epoxyl-NMPs were modified by amino-functional groups(-NH-,-NH2,-N＜) of diamines via ring-opening reaction to obtain the NH2-NMP adsorbents.Overall,5 series,22 kinds in total,of NH2-NMPs were synthesized by varying the usage amount of diamino agents,i.e.ethylenediamine(EDA),GMA,DVB and nano Fe3O4,and the kinds of diamines.The morphology,dimensions,paramagnetic properties, contents and structures of NH2-NMPs have been characterized by transmission electron microscopy(TEM),vibrating sample magnetometer(VSM),X-ray diffraction(XRD), thermogravimetry and differential thermogravimetry analysis(TG-DTA),Fourier transform infrared spectroscopy(FTIR),Brunauer-Emmett-Teller(BET) and elementary analysis(EA). The experimental results showed that NH2-NMPs particles were well multidispersed with an average diameter of around 30-50 nm,well responded to magnetic fields,and thermodynamic stabilized below 300℃.The effects of the NH2-NMPs for the removal of Cr(Ⅵ) from wastewater were verified from laboratory batch tests.The effects of some important variables, e.g.the usage amount of EDA,GMA,DVB and nano Fe3O4,and the kinds of amine in the process of preparation on the effectiveness of the NH2-NMPs for the removal of Cr(Ⅵ) from wastewater were studied.Some important variables,e.g.the effects of pH value,the initial concentration of Cr(Ⅵ),coexisted metal ions,and temperature were intensively investigated. The adsorption thermodynamics were discussed by using differents adsorption isotherm,and the adsorption kinetic data obtained from batch experiments were analyzed using a pseudo-second-order rate.Presumed mechanism of Cr(Ⅵ) adsorption onto NH2-NMPs was also discussed by investigating the morphology,dimensions,magnetic properties,structures of the NH2-NMPs before and after adsorption of Cr(Ⅵ).The results showed that the adsorption properties of the NH2-NMPs were highly pH dependent,and the adsorption efficiency of Cr(Ⅵ) decreased with the increase of the pH value and the initial Cr(Ⅵ) concentration.Under the optimized condition,the highest maximum adsorption capacity of the synthsized NH2-NMPs onto Cr(Ⅵ) was 370.4 mg·g-1,which was 33 times higher than those of the other adsorbents reported in literature.The effect of the coexistence of Cu(Ⅱ),Zn(Ⅱ),Ni(Ⅱ) ions on the effectiveness of the NH2-NMPs for the removal of Cr(Ⅵ) from wastewater was also studied. The result showed that the effectiveness of the NH2-NMPs for the removal of Cr(Ⅵ) can be weakened by the coexisted metal ions.The thermodynamics studies showed that the process of the Cr(Ⅵ) adsorption onto NH2-NMPs was endothermic and entropy favored in nature,and was well correlated with the Langmuir isotherm equation.The kinetic studies showed that the adsorption process fitted the pseudo-second-order rate equations well.The adsorption mechanism studies showed that the adsorption of Cr(Ⅵ) could be related with electrostatic attraction,ion exchange and coordination interactions.The recycle of the NH2-NMPs have been studied and showed that the adsorption efficiency remained above of 96%after 8 cycles.The catalytic properties of post adsoprtion materials have been investigated for the selectivity oxidation of benzyl alcohol to benzaldehyde.The conversion of benzyl alcohol and selectivity of benzaldehyde both can be reached to 100%,which provide a feasible way to make waste profitable.
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