| In recent years, magnetic nanoparticles were concerned because of its superior reactivity. The materials also has wide application prospects in the field of environment remediation. In this paper, Different types of magnetic nanocomposites were prepared, which can be used for Pb, Cd, Cr removal from aqueous solution. The dynamics process and external influencing factors of target pollutants removal in the system were discussed.1 NZVI@CM (NZVI@C/Fe3O4) magnetic nanocomposites were prepared by a hydrothermal and a liquid phase reduction methods. The materials were characterized by using transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR) and thermo gravimetric analysis (TG). NZVI@CM were applied to remove Pb(II) from aqueous solution. The results show:(1) Fe3O4 particles exhibit spherical particle with an average diameter of approximately 150 nm. Fe3O4 particles were coated with a layer of carbon NZVI dispersed on the surface of CM evenly.(2) Pb(Ⅱ) can be quickly and effectively removed by NZVI@CM nanocomposites in the system compared with CM or NZVI. The removal efficiency of Pb(Ⅱ) was 99.7% by using 60 mg of NZVI@CM at pH 7.(3) The presence of Cl- and NO3- in aqueous solution has adverse effect on the removal of Pb(Ⅱ).(4) The removal reaction of Pb(Ⅱ) accords to pseudo-second-order kinetics mode.2 NZVI/graphene oxide (NZVI/GO) magnetic nanocomposites were prepared by oxidation and liquid phase reduction methods. NZVI/GO nanocomposites were characterized by TEM, XRD, FT-IR, TG and Raman The capability of NZVI/GO to remove Cd(II) from aqueous solution was investigated. The Cd(II) removal with the influence of reaction time, mass fraction of each component in the nanocomposites, dosage of catalyst, pH, temperature and salinity were discussed in this paper. Experimental results show:(1) GO shows the lamellar structure; NZVI particles diameter is about 25 to 50 nm.(2) GO has no adsorption for Cd(II); The nanoparticles reactivity was highest when the mass ratio of GO and NZVI was 13. The removal efficiency of cadmium elements in mis system was 98%.(3) The removal efficiency of Cd(II) was reduced slightly with the increase of salinity in system.3 C16/Fe3O4@SiO2 nanocomposites were prepared by coprecipitation and sol-gel methods. Nanocomposites were characterized by TEM, XRD, FT-IR and TG. Then C16/Fe3O4@SiO2 were applied to remove Cr(III) and Cr(VI) from aqueous solutioa The various parameters, such as pH, the concentration of APDC, dosage of catalyst, co-existing ion, the type of eluent and the repeated use of nanocomposites were studied. The results show:(1) Fe3O4 particles exhibit spherical particle and uniform dispersion with an average diameter of approximately 20 nm. SiO2 and C16 were assembled on magnetic Fe3O4.(2) The removal efficiency of Cr(Ⅲ) and Cr(VI) have a obvious increase with the addition of APDC. The removal efficiency of Cr(Ⅲ) was 94.8% with the concentration of APDC at 3.125 mmol·L-1 in pH 9. The removal efficiency of Cr(VI) was 99.7% with the concentration of APDC at 12.5 mmol·L-1 in pH 2.(3) The method has good selectivity for removing Cr(Ⅲ) and Cr(VI). The existence of Pb2+, Cu2+ and Cd2+ have no effect on the removal efficiency of Cr(HI) and Cr(VI).(4) The elution effect of HNO3 for Cr(Ⅲ) and Cr(VI) metal complex which adsorbed on the surface of the materials is best The recovery rate can reach more than 90%.(5) The stability and durability of C16/Fe3O4@SiO2 magnetic nanocomposites was well and nanocomposites can be recovered after regeneration.
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