Synthesis and Characterization of Triamine modified coated Iron Sand Hybrid Nanomaterials originating from Kendal Coast

Received: 2nd September 2019 Revised:10th February 2020 Accepted: 11th March 2020 Online: 31 March 2020 Nanomaterials have broad and unique applications in various fields. In this research, synthesis of Iron Sand Magnetic Hybrid nanomaterials coated with propyldiethylenetriammine modified silica (PB@Si02@TA) originating from the coast of Muara Kencan, Kendal Regency. This study began with iron sand preparation, continued with activation, dispersing iron sand, then coating iron sand with propyldiethylenetriammine modified silica. The resulting product was characterized by X-Ray Fluorescence (XRF), Fourier Transform Infrared (FT-IR) Spectrophotometer, X-Ray Diffractometer (XRD), and Transmission Electron Microscope (TEM). The characterization results show that the iron sand of the coast of Muara Kencan Beach has a high iron oxide content (81.66%) with minerals in the form of magnetite. The characterization results also showed that the nanomaterial hybrid iron sand coated with propyldiethylenetriammine modified silica (PB@Si02@TA) was successfully synthesized with a crystal size of 36.21 nm, with better particle dispersion than the prepared iron sand.


Introduction
Nanomaterials have broad applications in various fields such as health, material coating, adsorption, sensors, and catalysts [1, 2, 3 , 4 , 5 , 6]. Nanomaterials have a large surface area, high reactivity, large adsorption capacity, and fast adsorption rate [ 7 ]. Nanomaterial in the form of magnetite (Fe 304 ) can be used in the process of adsorption of heavy metals because Fe 304 facilitates the process of separating the adsorbent from the solution in the Batch system through the use of external magnets [8]. Fe 304 in nature is found in iron sand, where natural iron sand also has other iron oxide compositions in the form of hematite ( -Fe 203 ) and maghemite ( -Fe 203 ) [ 9 ]. Iron sand is abundant on the coast of Central Java Province, one of which is in the Kendal Regency [10]. However, magnetite tends to form aggregates, so dispersing agents such as sodium citrate is needed [11].
Inorganic-organic hybrid material has potential as an adsorbent. Silica gel is used as an inorganic matrix on inorganic-organic hybrid materials that are stable under acidic conditions, inert to redox reactions, and can be modified with functional groups, thereby increasing adsorbent selectivity [12, 13 , 14 ]. The method used to coat silica on a magnetic material is the Stober method through the sol-gel process [ 15 ]. Where the silica gel precursor that is more often used is sodium silicate because of its low price and low toxicity [16], the surface of silica can be modified with active clusters of organic compounds such as the mercapto group (-SH) or amine group  to increase selectivity in adsorbing heavy metal ions. Diamine grouped adsorbents can adsorb heavy metals better than mercapto group adsorbents [ 17 ].
In order to improve the ability to adsorb heavy metals, an organic compound with three amine groups of N 1 -( 3 -trimethoxysilpropyl) diethylenetriamine (TMSPDETA) was used to modify silica-coated iron sand. The pH factor influences the type of interaction that occurs between the metal and the adsorbent surface. At low pH (pH <4.9) , the protonated amine group  forms -NH 3+ as Lewis acid so that it can bind to a metal θ = 0,9 . cos λ β θ anion complex [18]. However, at pH> 4.9 , the -NH2 group tends to be a Lewis base so that it can bind metal cations [18]. Thus, it is expected that the magnetized silica hybrid nanomaterial modified triamine group can be utilized as an adsorbent in further research. The purpose of this study was to synthesize and characterize the triamine modified silica-coated iron sand hybrid material (PB@Si 02@TA ). The benefit of this research is the production of a hybrid triamine modified silicacoated iron sand material (PB@Si 02@TA ).

Methodology
The stages of this research consisted of a) Preparation of iron sand magnetic material treated with water and characterization of the preparation material, b) Coating of iron sand material by adding Na2Si 03 and TMSPDETA solution and continued with a characterization of the synthesized material.

Iron Sand Magnetic Material Preparation
The essential ingredients of iron sand were separated using an external magnet. Solids attracted by external magnets were dried in an oven at a temperature of 70 -8O°C for 24 hours, then crushed and weighed. The obtained iron sand powder was characterized by XRF, FT-IR spectrophotometer, XRD, and TEM.

. Activation and Dispersion of Iron Sand Magnetic Materials
Five grams of magnetic iron sand from the preparation was then put into a beaker. Then washed with distilled water and sonicated for 30 minutes and repeated three times. After that, the magnetic material in the beaker was washed using a 10 mL HC1 solution and sonicated for 30 minutes, then rinsed using distilled water to neutral pH. An external magnet separated the mixture obtained in the beaker, and the sediment is taken. The activated magnetic material was then added with 100 mL of 0.5 M sodium citrate solution and allowed to stand for 24 hours. The obtained solid was separated with an external magnet and dried in an oven at a temperature of 70 -8o°C for 24 hours. Then the solid was crushed, weighed, and characterized with XRF, FT-IR spectrophotometer, XRD, and TEM.

Coating of iron sand magnetic material by triamine modified silica
The process of coating iron sand material by silica gel and the attachment of a group of propyldiethylenetriammine to the surface of silica was conducted through the sol-gel process. Three grams of iron sand material were acidified with 1 mL 1 M HCl solution, and the precipitate was taken (Mixture 1). Then as much as 3.0 mL of Na2Si 03 solution added with 1.2 mL of distilled water and 1.8 mL of TMSPDETA, then sonicated for 30 minutes (Mix 2). Then mixture 2 was put into a container containing mixture 1 and sonicated for 10 minutes. After that into the mixture, 1 M of HCl solution was added dropwise to pH of 7 , and a gel was formed. Then, the gel formed was sonicated for 30 minutes and left for 24 hours. After aging, the gel was washed with distilled water to a neutral pH, separated with an external magnet, and the sediment was taken. The precipitate obtained was dried in an oven at 8o°C for 24 hours. After drying, the solid was crushed and separated using an external magnet. Solids attracted by magnets were weighed and characterized by FT-IR, XRD, and TEM spectrophotometers.

. Data analysis
Data analysis of iron sand material coating by silica gel and clustering was performed by interpreting the data obtained from the results of the characterization of the synthesized material.
Iron Sand Material Content. XRF analysis was used to identify the magnetic material content of the iron sand in Muara Kencan Beach, Kendal Regency, Central Java . Functional Group. FT-IR spectrophotometer analysis is used to qualitatively identify the presence of functional groups contained in a sample compound.
The crystallinity of the magnetic material can be seen from the intensity of the X-ray diffraction peak. A sharper peak in XRD indicates higher crystallinity [21]. Based on the XRD pattern, magnetite coated with silica has lower crystallinity compared to magnetite coated with citrate, due to the amorphous nature of silica [22]. θ Amorphous silica has a characteristic peak at 2 = 20-26° [ 23 ].

Results of analysis of material contained in iron sand (XRF test)
Morphology. TEM is used to determine the dispersion of magnetite nanomaterials [11] and see the image of the coated material. The magnetite part is black, while the silica layer is gray [  The results of XRF characterization on iron sand from the preparation and activation results are shown in Table 2. Based on Table 2, it is known that the magnetic material of the iron sand coast of Muara Kencan Beach has a content that is dominated by iron (Fe) and a minority content of impurities such as Ti, Si, Al, Ca, V, Mn, Eu , Rb, Re, K, P, Cr, and Zn. Meanwhile, activated iron sand showed an increase in iron content compared to prepared iron sand, from 81.66% to 82.64 %. This is because some of the impurities have dissolved in the HCl acid solution used in the activation process.  [ 24 ] 466 [ 25 ] 540 [22] 805 Composition (%) Elements Prepared iron sand Activated iron sand [ 24 ] 1092 81.66

. Results and Discussion
Iron sand samples were obtained from the Muara Kencan Beach, Kendal Regency, Central Java Province.
Iron sand was prepared using an external magnet to separate the material content of the iron sand from its impurities; then, it is washed with distilled water, then dried. Then the iron sand was activated using 1 M HCl solution and 0.5 M sodium citrate solution. The iron sand magnetic material obtained had a black color, which indicated that the iron sand was dominated by the magnetic iron oxide content (Fe 304 ). This result was following the characteristics of magnetite proposed by Cornell and Schwertmann [ 9 ].
Magnetic material for iron sand preparation, activated iron sand material, and the synthesized product in the form of hybrid triamine modified silicacoated iron sand material (PB@Si 02@TA ) were characterized to find out the success of synthesis with a) analysis of material contained in iron sand with X-Ray Fluorescence (XRF), b) functional group analysis with Fourier Transform Infrared (FT-IR) Spectrophotometer for analysis of functional groups in materials, c) analysis of crystallinity and crystal size with X-Ray Diffractometer (XRD) for analysis, and morphological analysis with Transmission Electron Microscope (TEM).

. Iron Sand and PR@Si02@TA functional groups
The results of FTIR characterization on magnetic iron sand were prepared, activated iron sand, citric acid dispersed iron sand, and the PB@Si02@TA were shown in Figure 1    Based on Figure 1 and Table 1 Based on Figure 1 shows that the prepared and activated iron sands and PB@Si02@TA have a -OH functional group and a Fe-OH bond that shows the iron oxide content of magnetic material. The prepared and activated iron sands also still have impurities in the form of silica. The iron sand activated by HC1 and sodium citrate also has a -COOgroup and a C-H bond from the citrate group that demonstrates that the citric dispersed activated iron sand was successfully synthesized. In PB@Si02@TA, there is also a Si-O-Si bond with symmetric stretching vibrations, N-H and C-H bonds of the propyldiethylenetriammine group, the -OH group from Si-OH which shows that the activated iron sand successfully coated with propyldiethylenetriammine modified silica group. Thus, PB@Si02@TA was synthesized successfully.

. Crystallinity and size of iron sand mineral and PB@Si02@TA
The results of XRD characterization on the prepared iron sand magnetic material, citric dispersed activated iron sand, and PB@Si02@TA are shown in Figure 2  Based on Figure 2, the XRD diffraction pattern on the prepared iron sand material, citric dispersedactivated iron sand, and PB@Si02@TA match with peaks of 2 on the standard Fe 304 diffraction pattern of JCPDS oo-ooi-iiii. This indicates that all these materials contain minerals containing iron oxide magnetite (Fe 304 ). The crystallite size of the prepared iron sand, activated iron sand, and PB@Si02@TA are determined by the Debye-Scherrer equation, as suggested by Wu et al [20]. Meanwhile, crystallinity is determined based on the intensity of the diffraction pattern, as stated by Hui et al. [21]. Determination of crystal size and intensity of diffraction pattern peaks at Miller index: 220, 311 , 400 , 422 , 511 , and 440 for the prepared iron sand material, citric dispersed-activated iron sand, and PB@Si02@TA are shown in Table 3 . Table 3 , the sizes of iron sand crystals are prepared, citric dispersed -activated iron sand, and PB@Si02@TA has nanoparticle size because it has a size in the range 1-100 nm referring to Kamal [2]. Activated iron sand has a smaller crystal size and a higher diffraction pattern intensity than the prepared sand iron. This may be since the prepared iron sand is only washed with distilled water, so the particles are still in the form of aggregates and have lower crystallinity because they still have more amorphous silica impurities suggested by Prasdiantika and Susanto [ 27 ]. Whereas in activated iron sand material, which is iron sand washed with HC1 solution, impurities are lost and soaking with was a as sodium citrate solution reduced aggregation of magnetite particles as suggested by [ 19 , 28, 29 ] and supported the TEM results in Figure 3 .

Based on
PB@Si02@TA material has a larger crystal size and lower intensity of diffraction pattern compared to activated iron sand. This is due to the effect of amorphous modified silica propyldiethylenetriammine groups on PB@Si02@TA material, as indicated by a diffraction pattern that is inflated, as stated by Hong et al. [22] and Tan et al. [ 23 ]. This shows that the activated iron sand was successfully coated with a propyldiethylenetriammine modified silica. Thus PB@Si02@TA was synthesized successfully.

. Morphology of PB@Si02@TA
The images of Transmission Electron Microscopy (TEM) on prepared iron sand and citric dispersed activated iron sand with a magnification of 500 nm are shown in Figure 3 .
The TEM image in Figure 3 shows that the iron sand produced from activated citrate dispersed ( 3 b) has a more evenly dispersed particle dispersion than the prepared iron sand ( 3 a). That is because sodium citrate in activated iron sand has succeeded in reducing the aggregation of magnetite material in iron sand. The black color in the TEM ( 3 a) image of the prepared iron sand is a magnetite particle, while the gray part is a silica impurity element, as stated by Li et al. [ 15 ]. While the gray color in the TEM (    From Figure 4 a, it is observed that there are many gray parts, which are the layers of citrate and silica impurities in iron sand. Whereas in Figure 4 b, PB@Si02@TA has a gray portion derived from a modified silica layer of the propyldiethylenetriammine group and has a black part, which is a magnetite oxide in iron sand.
In the modified silica coating of the propyldiethylenetriammine group, citric dispersed-activated iron sand was added with 1 M HC1, which causes the citrate to release; hence the magnetite produces a Fe-OH group which allows reacting with the propyldiethylenetriammine modified silica. The acidified iron sand exchanges ligands with silica compounds, then the silica-based ligands undergo condensation and coat the surface of the magnetite, as stated by Hong et al. [22] and Susanto and Prasdiantika

. Conclusions
The results of XRF, FTIR, XRD, and TEM characterization showed that the iron sand in the Muara Kencan Beach, at Kendal Regency had a high iron oxide content (81.66%) with a type of magnetic material was magnetite. The results of FTIR, XRD, and TEM characterization also showed that the iron sand hybrid nanomaterial coated with propyl diethylene triamine modified silica (PB@Si 02@TA ) was successfully synthesized with a crystal size of 36.21 nm and better particle dispersion compared to the prepared iron sand.