The authors have declared that no competing interests exist.
In this work, SrCrxFe12-xO19 (x = 0.0, 0.5, 1.0, 1.5) nanostructures were successfully synthesized by sol-gel auto-combustion method, and different aminoacids were used as green reductants. Various analysis results show that SrCrxFe12-xO19 nanoparticles synthesized successfully.The present study shows that SrCrxFe12-xO19 nanoparticle could be used as adsorbent for the desulfurization of liquid fuels. Increasing of nanoparticles concentration was caused to increase the adsorption rate of sulfur contents of fuel. The adsorption rate of sulfur contents of fuel in various concentrations 4.5, 9.5, and 18.5 g. L -1 of SrCrxFe12-xO19 nanoparticles in solution was estimated about 39, 50, and 62% for 30 min, respectively. The results of catalytic tests reveals that SrCrxFe12-xO19 nanoparticles have the potential to be used as a new kind of semiconductor catalysts for the desulfurization of liquid fuels. Magnetic property of the final sample was measured at room temperature by a vibration sample magnetometer (VSM) and shown that the intrinsic coercivity of product is about 6000 Oe and it exhibits characteristics of single magnetic domains (Mr/ Ms = 0.53).
Nanostructure materials are used in various fields such as photocatalytic, superconductors, nanoelectronicssuch as photocatalytic, superconductors, nanoelectronics and supercapacitors [
Recently, simple and inexpensive methods have been replaced by complex and expensive routes that can control the shape and size of nanostructures, also, due to the environmental worries, using of natural sources instead of chemical compounds has particular importance. Hence, we tried using amino acids as a natural source to use of green chemistry benefits. On the other hand, environmental concerns have driven the need to remove sulfur-containing compounds from light oil. One of main component in liquid fuel is sulfur compounds such as SO2 and H2S that are harmful for environmental and human healthy, so, much attention has been recently devoted to this process. In present work, removal of sulfur compounds in liquid fuels using SrCrxFe12-xO19 nanoparticles as an effective catalyst was reported. The obtained results showed that the mechanism of desulfurization follows Freundlich isotherm that is another form of the Langmuir approach for adsorption on a heterogeneous surface. Furthermore, the sol-gel route has used as a versatile technique for preparing chemical compounds and inorganic materials that possess advantages such as: chemical homogeneity, easy component adjustment, low calcination temperature and low cost, in addition to sol-gel route is one of methods for synthesis of nanomaterials [
The SrFe12O19 with high crystalline and small particle size is synthesized by sol-gel method [
Herein, SrCrxFe12-xO19 (x = 0.0, 0.5, 1.0, 1.5) nanostructures were synthesized by using various amino acids as fuel, reducing and capping agent via sol-gel auto-combustion technique. In addition, the effect of various parameters such as type of amino acid and chromium ions concentration that is substituted by Fe+3 cations on the particle size, morphology and purity of product was studied. The as-produced nanostructures were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDS) analysis and powder X-ray diffraction (XRD). Magnetic property of the final sample was measured at room temperature by a vibration sample magnetometer (VSM) and shown that the intrinsic coercivity of product is about 6000 Oe. The results of catalytic tests reveals that SrCrxFe12-xO19 nanoparticles have the potential to be used as a new kind of semiconductor catalysts for the desulfurization of liquid fuels.
All the chemicals used in this work were commercially available and employed without further purification. FT-IR spectra were recorded on Magna-IR, spectrometer 550 Nicolet in KBr pellets in the range of 400–4000 cm–1. Powder X-ray diffraction (XRD) patterns were collected from a diffractometer of the Philips Company with X’PertPro monochromatized Cu Kα radiation (λ = 1.54 Å). Microscopic morphology of the products was studied by FESEM (Mira3 tescan) and TEM (HT-7700). The energy dispersive spectrometry (EDS) analysis was studied by XL30, Philips microscope. The magnetic properties of the samples were detected at room temperature using a vibrating sample magnetometer (VSM, Meghnatis Kavir Kashan Co., Kashan, Iran).
Sr(NO3)2, Fe(NO3)3. 9 H2O, Cr(NO3)3. 9 H2O and various amino acids were used as starting materials. SrCrxFe12-xO19 (x = 0.0, 0.5, 1, 1.5) nanostructures were synthesized through the reaction between Sr(NO3)2, Fe(NO3)3. 9 H2O, Cr(NO3)3. 9 H2O with molar ratio of 1: 12: x (x = 0.5, 1 and 1.5), respectively. At first, 0.2 g (1 mmol) Sr(NO3)2 was dissolved in 75 ml of distilled water, and then aqueous solutions including stoichiometric amount of Fe(NO3)3. 9 H2O (4.5 g) and Cr(NO3)3. 9 H2O was added to it. The resulted solution was vigorously stirred at 50°C for 30 min. Then, the appropriate amount from amino acid (glutamine, cysteine, valine and leucine) was dissolved in a minimum amount of de-ionized water (the molar ratio of amino acid to Sr(NO3)2 was fixed at 13). Finally, thermal dehydration was done and the obtained powder disinterred at 800, 900 and 1000 OC for 120 min. The as-prepared products were characterized by XRD, SEM, EDS, FT-IR and TEM.
Sulfur content of fuel has been decrease to low levels by environmental regulation in worldwide with the aim of improving air quality. In this research, SrCrxFe12-xO19 nanoparticles (sample no. 6) were used as new adsorbent. The present study shows that SrCrxFe12-xO19 nanoparticles could be used as adsorbent for the desulfurization of liquid fuels. Total sulfur content was measured using petrotest calorimetric bomb C5000.according to ASTM D-1266. Batch experiment for determination of the kinetic models are used. Kinetics of sulfur on SrCrxFe12-xO19 nanoparticles carried out at 35 OC. Different concentration of SrCrxFe12-xO19 nanoparticles were brought in contact with 30 ml sample at 35 OC.
To investigate the effect of different parameters on the morphology, particle size and purity of the products, the various experiments were performed. All of the preparation conditions were illustrated in
Sample no. | Kind of Amino acids | Amount of Cr+3 / Sr+2 | Morphology and Particle size |
---|---|---|---|
1 | - | 0 | Irregular shapes; 300 nm |
2 | Glutamine | 0 | Irregular shapes; 50 nm- 500 nm |
3 | Cysteine | 0 | Hexagonal shapes; 200–400 nm |
4 | Valine | 0 | Hexagonal and uniform shapes; 150 nm |
5 | Leucine | 0 | Irregular shapes and particle; 50 nm- 500 nm |
6 | Valine | 0.5 | Uniform particle; 50 nm- |
7 | Valine | 1 | Irregular shapes; 200 nm |
8 | Valine | 1.5 | Irregular large shapes and fine particles |
The morphology of the products (SrFe12O19) prepared by various aminoacids is examined by SEM (
(a) sample 1, (b) sample 2, (c) sample 3, (d) sample 4 and (e) sample 5.
The morphology of the SrCrxFe12-xO19 (x = 0.5, 1.0, 1.5) micro/nanostructures is examined by SEM (
(a) sample 6, (b) 7, and (c) 8.
The crystal structure of the as-prepared micro/ nanostructure is determined by XRD.
(a) sample 4, and (b) sample 6.
(a) sample 7, and (b) sample 8.
In the EDS spectrum of SrCrxFe12-xO19 obtained from sample 6 (
(a) UV–vis spectrum, and (b) curve (Ahυ) n versus hυ of sample 6.
Optical band gap (Eg) may be evaluated based on the optical absorption spectrum using the following equation [
The magnetic properties of materials were investigated by VSM. The magnetic hysteresis loop was depicted in
In this study, we prepared different concentrations of sample by diluting it with n-hexane to investigate its effect on the sorption kinetics during the experiment. The catalytic activities of the obtained particles are evaluated by desulfurization of liquid fuels, and the adsorption amounts are changed by concentration of nanoparticles, as shown in
(a) 4.5 g. L -1, (b) 9.5 g. L -1, and (c) 18.5 g. L -1.
Longmuir isotherm assumes monolayer adsorption onto a surface containing a finite number of adsorption. The linear form of Langmuir isotherm equation is given as:
Where C
The isotherm was another form of the Langmuir approach for adsorption on a heterogeneous surface. the linear form of Freundlich equation is:
Where C
Effect of temperature on removal of total sulphur was studied at range 15–55°C. The result shows that temperature has large effect on removal of total sulfur.
The effect of contact time on the rate of the removal of sulfur at different concentration of nanoparticle as shown in
Chromium substituted strontium ferrites have been produced via a sol-gel auto-combustion technique by using various amino acids as fuel, reducing and capping agent. The effect of types of amino acid and chromium ion concentration on the morphological, magnetic and optical properties of products were studied. By considering SEM images, valine amino acid is chosen as desired amino acid for reducing process in auto-combustion reaction. XRD results are shown that when the concentration of Cr 3+ is ≥ 0.5, except than SrFe12O19 phase, Fe2O3 is formed. The saturation magnetization decreases with doping chromium to compare with SrFe12O19, due to the substitution of Cr 3+in the 12k and 2a sites of the lattice. Also, with doping of Cr 3+, coercivity is increasing due to increase in anisotropy field, which in turn increases of domain wall energy and morphology anisotropy. Investigating of UV-vis spectrum detected two absorption peaks around approximate 275 and 370 nm can be observed, which is similar to other reports. The present study shows that SrCrxFe12-xO19 nanoparticle could be used as adsorbent for the desulfurization of liquid fuels. Increasing of nanoparticles concentration was caused to increase the adsorption rate of sulfur contents of fuel. The adsorption rate of sulfur contents of fuel in various concentrations 4.5, 9.5, and 18.5 g. L -1 of SrCrxFe12-xO19 nanoparticles in solution was estimated about 39, 50, and 62% for 30 min, respectively. The results of catalytic tests reveals that SrCrxFe12-xO19 nanoparticles have the potential to be used as a new kind of semiconductor catalysts for the desulfurization of liquid fuels.
Authors are grateful to the council of Iran National Science Foundation (INSF) and University of Kashan for supporting this work by Grant No (159271/8290).