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The effect of 6 hours stirring time on natural iron sand base on magnetics Fe3O4 nanoparticle by sonification

In this research, ferrite magnetic nanoparticles (Fe3O4) from natural iron sand have been synthesized by co-precipitation technique with varying stirring time and sonification process. The purpose of this study was to determine the effect of 6 hours of synthesized magnetic nanoparticles (MNPs) on the resulting crystal size. The different structures and properties of the synthesized Fe3O4 nanoparticles were investigated using X-Ray Diffraction (XRD), Scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and Energy Dispersion X-ray (EDX), respectively. XRD and SEM produced mean crystal sizes over the range of 13.93 nm and particle sizes of 14.8 nm. The EDX test explained that the Fe3O4 compound was successfully formed at 6.00 KeV. FTIR showed the element content of Fe-O at 555 cm-1. This study’s results indicate the MNPs synthesis process at 6 hours and the sonification process can produce Fe3O4 nanoparticles with a minimum size at the optimal time compared to synthesis at 8 hours, 7 hours, and 5 hours.


Introduction
Compared to bulk forms, nanoscale materials (<100 nm diameter) have superior physical and chemical properties due to the mesoscopic effect, small object effect, quantum size effect, surface/interface effect. In this decade, MNP Fe3O4 has been studied intensively because of its superparamagnetic properties, high coercivity, low curie temperature. There are also additional, deficient toxic, biocompatible properties. Therefore, Fe3O4 MNPs generate several applications such as biosensors [1], gas sensors, contrast agents for MRI, contrast agents for PET and NIRF, hyperthermia therapy, magnetic targetsdrug delivery systems, microelectronic applications such as photodiodes, microwave absorbers, adsorbent for vegetables and fruits, nano-photocatalysis, lithium-ion battery, ferrofluid, magnetic printer ink, thin-film, Solar Cell, bone repair [2], bioremediation [3], cancer treatment [4], SERS application [5].
There are various ways to synthesize nano Fe3O4, including solvothermal [6], hydrothermal [7], solgel [8], electrospinning [9], microwave combustion method, photochemical [10], co-precipitation. Among the developed synthesis methods, the coprecipitation method is the simplest because it is easier to perform and requires a relatively low reaction temperature (<100˚C). Controlling the shape and size of the particles can be controlled by variations in reaction temperature [11], pH at reaction time [12], and concentration of materials [13]. The co-precipitation method is a chemical process that reduces Nanotechnology, particularly in nanoparticles, has been widely developed because of its size and very active performance. The disadvantage is that it is prone to clumping between the nanoparticles and their neighbors due to their small size and high surface energy [14,15]. The sonification process is carried out to reduce clumping to produce a homogeneous particle size and tend not to agglomerate easily. Research by Rahmawati (2017) uses a sonification process resulting in a much smaller nanoparticle size than without the sonification process [16].
Synthesis of MNPs from natural iron sand using a synthesis time of 6 hours is known to have never been carried out. Several studies conducted the synthesis of MNPs at 90 minutes by Setiadi (2016) to produce Fe3O4 nanoparticles with a size of 25-50nm [17]. Rahmawati's research (2017) carried out the synthesis of MNPs in 30 minutes resulting in 20-25 nm of Fe3O4 nanoparticles. The synthesis process with a long time will make the nanoparticles stable and well homogenized [16]. Therefore, this research is focused on the synthesis of nano Fe3O4 with a stirring time of 6 hours using local natural iron sand. The Fe3O4 nanopowder formed was characterized using XRD to see its crystal structure, SEM-EDX to see the surface morphology and powder composition, and FTIR to see the presence of its molecular structure.

Materials
The main ingredients used in the synthesis of Fe3O4 nanoparticles with the co-precipitation method are natural iron sand (Kulonprogo Beach, Yogyakarta, Indonesia), 37% Chloride Acid (HCL) solution, Ammonium Hydroxide (NH4OH) solution, and aquades.

Synthesis
The first step is the extraction of natural iron sand using permanent magnets. Natural iron sand is filtered using gauze with a certain mesh size to separate the remaining impurities. Re-extraction uses permanent magnets to obtain magnetic components. The natural iron sand is then washed and dried in the sun. To obtain Fe3O4 nanoparticles, the method used is co-precipitation. The decomposition of natural iron sand is dissolved with HCl at 370 rpm for 6 hours to form a black solution. The result of decomposition with HCl is then filtered with filter paper to obtain FeCl2 and FeCl3. Then the solution that passes through the filter is added to the NH4OH solution. FeCl2 and FeCl3 solutions react chemically with NH4OH to form a Fe3O4 nano, NH4Cl, and H2O solution. The result of the solution was then sonified for 2 hours. Then washed with distilled water to lower the pH. After that, it is dried to produce Fe3O4 nanoparticle powder.

Characterization
SEM-EDX measurement, SEM is a testing technique to see the surface morphology of Fe3O4 nanoparticles. EDX is a testing technique used to determine the composition of Fe3O4 nanoparticles. The tool type and series are SEM-EDX JED-2300 JEOL. To calculate the average particle size of the SEM images, ImageJ 1.52V software was used. XRD measurement XRD is one of the testing tools to determine the structure crystal of Fe3O4 nanoparticles. CuKα radiation was used to investigate the phase of Fe3O4 powder in the range of angles from 20 to 80. The tool type and series are Shimadzu 7000. The spectra obtained were compared with a standard database by Joint Committee on Powder Diffraction Standard (JCDPF 19-0629 and JCPDF 07-0007) from the International Center for Diffraction Data (ICDD). FTIR measurement, FTIR, is used to find out the bonding functional groups of Fe3O4 nanoparticles through their specific adsorption spectrum. The functional groups on the surface of Fe3O4 nanoparticles can be determined with the Perkin Elmer FTIR Spectrometer. Samples were examined in the wavenumber range between 400-4000 cm -1

Result and Discussion
To obtain Fe3O4 nanoparticles, the method used is co-precipitation with the following chemical reactions.    Figure 1.(b) shows the change in composition after natural iron sand was synthesized using the co-precipitation method. The composition contained into C, O, Al, Cl, and Fe with Al composition can be neglected because % w.t is below 0.5%. The morphological structure of natural iron sand using SEM is shown in Figure 2; it can be seen that the synthesized Fe3O4 nanoparticles are still agglomerated and not homogeneous. The cause of agglomeration [18] and not homogeneous [19] is due to the presence of the element NH4Cl, which is very strong to bind water. From calculations using ImageJ software, the measured average particle size is 14.8 nm.   The effect of the sintering time is shown by the sample results data in Table 1. The particle size decreases from the stirrer time of 8 hours to 6 hours later when the stirrer time of 5 hours, the crystal size has increased. This can be due to the equilibrium of the process when the stirrer time is 6 hours, whereas when the stirrer time is longer, the solution will become saturated, increasing the particle size and the occurrence of agglomeration. At a stirrer time of 7 hours and 8 hours, the possibility of the energy produced is greater so that the particles tend to interact with other particles and form a much larger size [23].   Figure 2.The adsorption peaks detected were at wavenumbers 555 cm -1 , 1091 cm -1 , 1393 cm -1 , 1442 cm -1 ,1644 cm -1 ,1752 cm -1 , 2006 cm -1 , 2805 cm -1 , 3016 cm -1 , 3116 cm -1 , 3356 cm -1 . The single peak of adsorption observed at 555 cm -1 is the Fe -O functional group bond [24], which indicates that a single-phase Fe3O4 bond has been formed. The adsorption peak with a wavenumber of 1091 cm -1 to 3356 cm -1 shows that the pattern of functional bond groups formed is NH4Cl, following PerkinElmer's FTIR analysis shown in Figure 5.

Conclusion
Synthesis of natural iron sand in the Kulonprogo area (Yogyakarta, Indonesia) has been carried out using the co-precipitation method. The final result is a powder of black Fe3O4 nanoparticles with an average particle diameter of 14.8 nm, good crystallinity, and maintaining the purity of Fe3O4 particles (singlephase at wave number 555 cm-1); from SEM-EDX, XRD, and FTIR analysis. The stirrer time effect indicated that 6 hours was the optimal time to produce a crystal size of 13,661 nm compared to the stirrer duration of 8 hours, 7 hours, and 5 hours.