High purity Fe3O4 from Local Iron Sand Extraction

Indonesia has a long coastline and is rich with iron sand. The iron sand is generally rich in various elements such as iron and titanium. One of the products processing of the iron sand mineral is iron (II) (III) oxide (magnetite Fe3O4). The stages of purification process to extracting magnetite phase and discarding the other phases has been performed. Magnetite phase analysis of ironsand extraction retrieved from Indonesia have been investigated. The result of analysis element of iron sand shows that it consists of majority Fe around 65 wt%. However, there are still 17 impurities such as Ti, Al, Ce, Co, Cr, Eu, La, Mg, Mn, Na, Sc, Sm, Th, V, Yb, and Zn. After extraction process, Fe element content increases up to 94%. The iron sand powder after milling for 10 hours and separating using a magnetic separator, the iron sand powders are dissolved in acid chloride solution to form a solution of iron chloride, and this solution is sprinkled with sodium hydroxide to obtain fine powders of Fe3O4. The fine powders which formed were washed with de-mineralization water. The X-ray diffraction pattern shows that the fine powders have a single phase of Fe3O4. The analysis result shows that the sample has the chemical formula: Fe3O4 with a cubic crystal system, space group: Fd-3m and lattice parameters: a = b = c = 8.3681 (1) Å, α = β = γ = 90°. The microstructure analysis shows that the particle of Fe3O4 homogeneously shaped like spherical. The magnetic properties using vibrating sample magnetometer shows that Fe3O4 obtained have ferromagnetic behavior with soft magnetic characteristics. We concluded that this purification of iron sand had been successfully performed to obtain fine powders of Fe3O4 with high purity.


Introduction
In Indonesia, approximately 2 billion tons natural iron sand resources are spread along the southern coast of Java, Sumatra, West Nusa Tenggara, and so on with the main content of iron oxide, titania, silica and alumina [1]. In Indonesia, iron sand is the source of raw material of iron/steel industry [1]  and cement [2]. Also, the product of iron sand processing can be Fe 3 O 4 . By processing the natural resources of iron sand into Fe 3 O 4 , the added value can be increased several number fold and can be used for import substitute products to enhance the competitiveness of the national industry. Magnetite (Fe 3 O 4 ) is an interesting material to develop because it is very applicable so that many researchers are interested in developing it [3][4][5][6][7][8][9]. Some of the treatment methods used are milling and precipitation [3], coprecipitation [4,7], precipitation and sol-gel [5], mechanical vibration [6], coprecipitation with polyethylene [8], mechanical alloying [9]. Through the Fe 3 O 4 calcination process, barium hexaferrite may be produced as a microwave absorber [3], for biomedical [10], and others. In this paper, we will report Fe 3 O 4 synthesis results from the natural iron sand of the titanomagnetite type.The iron sand powder after milling for 10 hours and separating using a magnetic separator, the iron sand powders are dissolved in acid chloride solution to form a solution of iron chloride, and this solution is sprinkled with sodium hydroxide to obtain fine powders of Fe 3 O 4 . Therefore this study aims to obtain nanoparticle of Fe 3 O 4 through the iron sand extraction.

Experiment
The iron sand of titanomagnetite is retrieved from Lampung, Indonesia. The purifying process of iron sand into iron oxide product in the form of high purity Fe 3 O 4 is shown in Figure 1. The iron sand of titanomagnetite was milled by using high energy milling (HEM), then dissolved in chloride acid (HCl) technical quality with the ratio of 250 g/L HCl to solve iron chloride. 5 M sodium hydroxide technical quality was added to a solution of iron chloride at a temperature of 80 °C for 1 hour. The precipitate was washed with demineralization water until pH of 7 with the purpose of disappearing the residual salts, then the precipitate was separated from the solvent using a permanent magnet and after that dried in an oven at a temperature of 100 °C. The dry powder sample was re-milled and then heated at a temperature of 400 °C in a furnace for 5 hours, so that obtained a Fe 3 O 4 powder. The Fe 3 O 4 powder was analyzed by X-ray diffractometer (XRD) of Pan Analytical product with CuKα radiation (λ = 1.5406 Å). The qualitative and quantitative analysis of phase was carried out by GSAS program. The particle morphology of the Fe 3 O 4 powders was observed by the scanning electron microscope (SEM) using JED 2300 JEOL. The elemental composition was analyzed by using energy dispersive spectroscopy (EDS). Finally, the magnetic properties were measured by using vibrating sample magnetometer (VSM) of Oxford product. Figure 2 shows the result of microstructure observation on iron sands sample of titanomagnetite type extracted by using scanning electron microscope.  In Figure 2 it appears that the surface morphological observations show that the samples have the same form and color, although there is still a wide particle of about 1.8-10 μm. It is assumed that the sample has a homogeneous phase. However, photographs of these surface morphologies also cannot determine the phases contained in the titanomagnetite iron sand samples of these extractions. For the analysis of the existing phases in the iron sand, x-ray diffraction is used, while for the analysis of the constituent elements, energy dispersive spectroscopy is used. Figure 3 shows the result of elementary analysis using energy dispersive spectroscopy on titanomagnetite iron sand sample. The resulting energy spectrum as shown in Fig. 3 shows that the most dominant elements are oxygen (O) and iron (Fe) which are consecutively at 0.525 keV and 6.398 keV energy with K-wavelength. This means that the extraction of titanomagnetite iron sand sample has successfully separated the iron (Fe) element from other impurities. In detail, the element content present in the iron sands of this type of titanomagnetite is shown in Table 1. In Table 1 it appears that the Fe content of total iron sand samples of titanomagnetite type of this extraction is 79.12%. These results indicate that the iron content in the titanomagnetite iron sand sample has been successfully performed.  Aluminum (Al) 1.10 ± 0.09 5.
Oxygen (O) 16.18 ± 0.11 Figure 4 shows the results of the measurement and structural analysis that can identify the phase of the x-ray diffraction pattern of titanomagnetite iron sand samples extracted.
(a) XRD identification (b) Refinement of XRD   [4] and also Rusianto et al. [6]. Thus, based on the results of the analysis of the x-ray diffraction pattern, the amount of phase content contained in the iron titanomagnetite iron extraction is shown in Table 2.

Conclusion
The samples Fe 3 O 4 have been successfully extracted by coprecipitation method from local iron sand. The sample has a homogeneous phase. However, photographs of these surface morphologies also can not determine the phases contained in the titanomagnetite iron sand samples of these extractions. The resulting EDS shows that the most dominant elements are oxygen (O) and iron (Fe). The XRD data show that the sample has a single phase with the structure of spinel ferrite particles. The functional group's analysis by using FTIR shows that transmittance peaks of the iron sand extraction appeared at wave numbers around 600 cm -1 that indicated the presence of the Fe-O bond vibrations. The hysteresis loop shows that all of the samples have the ferromagnetic behavior with a relatively small of coercivity value.