Fe3O4 magnetic nanoparticles synthesis from tailings by ultrasonic chemical co-precipitation
Research Highlights
► Fe3O4 nano-powder was synthesized by ultrasonic-assisted chemical co-precipitation. ► Fe3O4 nano-powder coated with C12H25OSO3Na show better dispersion and uniform size. ► Nanoparticles synthesis requires no protecting gas, and can be easily implemented.
Introduction
As developed mines are drying up, utilization of tailings is getting more attention [1]. Iron ore tailings are one of the most important industrial solid wastes. Due to their low iron content, exiguous granularity and complex composition, widely used extraction methods of magnetic separation or flotation are ineffective [2]. In this study high purity iron was separated from iron ore tailings by acidic leaching in order to alleviate the pressure of mining solid wastes on the environment. Magnetic Fe3O4 nanoparticles were synthesized with the purpose to explore sustainable economic way of recycling useful elements from mining solid wastes.
Iron ferrite, Fe3O4, is a traditional magnetic material used in magnetic storage media, solar energy transformation, electronics, ferrofluids and catalysis [3], [4], [5], [6], [7]. Several methods have been reported to synthesize Fe3O4 powders, including hydrothermal synthesis [8], microemulsion [9], chemical co-precipitation [10], oxidation of Fe(OH)2 by H2O2 [11], R-ray irradiation [12], microwave irradiation [13], etc. Co-precipitation is the simplest and cheapest synthesis method. However, this method does not yield uniform nano-scale Fe3O4 particles directly without further separation. Therefore, uniform Fe3O4 nanoparticles preparation method with excellent dispersion is needed.
In this paper high purity iron was separated from tailings, and then magnetic Fe3O4 nanoparticles were synthesized by ultrasonic-assisted chemical co-precipitation. Utilizing iron particles coated with surface active agent, instead of vacuum or protective gas processes, the problems of Fe2+ oxidation and particles agglomeration were successfully solved.
Section snippets
Separation of iron
Iron ore tailings were weighed (100 g), and mixed with 37.5 wt.% hydrochloric acid (HCl). Then pickling was filtered out and collected. An appropriate amount of hydrogen peroxide (H2O2) was added to the filtrate so that all iron could exist in the Fe3+ form. Filtrate was heated to 60 °C, and its pH value was adjusted to 3.2 by adding an appropriate amount of concentrated ammonia. As a result, Fe was separated from tailings and precipitated into Fe(OH)3. Finally, some amount of Fe(OH)3 was washed
Fe3O4 nanoparticles crystal structure and morphology
Fig. 2 shows X-ray diffraction patterns of synthesized Fe3O4 nanoparticles.
Comparing XRD pattern of synthesized particles with the standard diffraction spectrum (JCPDS: 65–3107), the synthesized product is crystalline Fe3O4. The sharpness of XRD reflections clearly shows that the synthesized Fe3O4 is highly crystalline. The average particle size was calculated to be 19.4 nm using the Sherrer's equation [14]:where L is equivalent of particles average core diameter; K is the grain shape
Conclusions
Utilizing high purity iron separated from iron ore tailings by acidic leaching method, nano-scale magnetic Fe3O4 powder was synthesized by ultrasonic-assisted chemical co-precipitation. As a result, Fe3O4 particles with 15 nm diameter exhibited super-paramagnetic behavior, and C12H25OSO3Na was added as surface active agent, assisting to obtain Fe3O4 nanoparticles with homogenous size and shape distribution. In the present study nanoparticles synthesis requires no protecting gas, and can be
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