In this paper, a magnetic graphene oxide (MGO) composite was prepared by the click reaction between the alkyne-modified Fe3O4 nanoparticles and the azide-modified graphene oxide for the purpose of removing the Congo red (CR) dye from water. The deposition of the Fe3O4 nanoparticles on the graphene oxide to successfully prepare the MGO composite was evidenced by the Fourier-transform infrared spectrometer, wide-angle X-ray diffraction equipment, scanning electron microscope, thermal gravimetric analyzer, and Raman spectrometer. The value of saturation magnetization for the MGO composite was 34.9 emu/g. The CR absorption capacities of the MGO composite increased first and then decreased as the pH value increased. It was found that the maximum adsorption capacity of the MGO composite for the CR was as high as 769.2 mg/g. In the absorption-desorption experiment, the CR absorption capacities of the MGO composite from the second cycle to the fifth cycle remained stable to be about 130 mg/g. Moreover, both the Langmuir model for the adsorption isotherm and the pseudo-second-order kinetic model could be used to describe the CR absorption behaviors of the MGO composite.
Takovite, a kind of hydrotalcite-like compounds (HTlcs), was used for boron removal from water. It was prepared by coprecipitation method and characterized by X-ray diffraction technique (XRD). The equilibrium time of boron sorption by takovite as well as its boron uptake capacities was determined by the reaction kinetic experiments and isotherm sorption experiments. The effects of experimental conditions on boron removal efficiency were also evaluated. Generally, the boron uptake by takovites increases with increasing initial boron concentration in solution. The isotherm sorption data match well with the Freundlich model, indicating that the anion exchange contributes a lot to solution deboronation. Moreover, at higher temperature, greater boron removal by takovite was observed. As compared to calcined takovite, uncalcined takovite has better performance in terms of boron uptake, since the structural restoration of calcined takovite didnt happen during its contact with boron-containing solution, which is quite different from the behavior of other HTlcs as reported.
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