Synthesis of magnetic porous gamma-Fe2O3/C@HKUST-1 composites for efficient removal of dyes and heavy metal ions from aqueous solution

A novel and inexpensive approach was adopted to developmagnetic porous gamma-Fe2O3/C@HKUST-1 composites for the adsorption of dyes and heavy metal ions from aqueous solution. The gamma-Fe2O3/C with unique functional groups present such as -OH and -NH2 was used as the support to directly grow HKUST-1 by a stepwise liquidphase epitaxy process. The crystallographic, morphology, and magnetic properties as well as porosity of the assynthesized gamma-Fe2O3/C@HKUST-1 composites were carefully studied by XRD, SEM, TEM, XPS, TGA, and BET. The results indicated that the BET surface area, micropore volume, and saturation magnetization of the gamma-Fe2O3/ C@HKUST-1 are 993.4 m(2) g(-1), 0.69 cm(3) g(-1), and 12.6 emu g(-1), respectively. In addition, a uniform distribution of ultrafine gamma-Fe2O3 nanoparticles with an average diameter of 2-3 nm was observed in the gamma-Fe2O3/C@HKUST-1 composites. Our results showed that methylene blue (MB) and Cr(VI) (used as amodel for typical dye pollutants and heavy metal ions) are effectively removed from aqueous solutions by gamma-Fe2O3/ C@HKUST-1. The maximum adsorption capacities were 370.2 and 101.4 mg g(-1) of adsorbent for MB and Cr(VI), respectively. Moreover, a removal efficiency of about 90% was retained after five cycles of consecutive adsorption-desorption. The adsorption kinetics data were well described by a pseudo-second-order model (R-2 > 0.99), and equilibrium data were well fitted to the Langmuir isotherm model (R2 > 0.99). Finally, our results suggested that the gamma-Fe2O3/C@HKUST-1 composites have a great potential to be employed for treatment of wastewater containing MB and Cr(VI).