جستجوی مقالات مرتبط با کلیدواژه « اسید اولئیک » در نشریات گروه « فنی و مهندسی »

In recent years, there has been a significant interest in lanthanum-based perovskites due . Lanthanum strontium manganite (LSMO) is one of the most well-known materials. In this research, the synthesis and investigation of the effect of oleic acid on the structural and magnetic properties of La0.7Sr0.3MnO3 nanoparticles by the combustion sol-gel method is discussed. The structural and magnetic properties of the prepared samples were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), magnetic properties analysis (VSM), and field emission electron microscopy (FESEM). In the XRD study, it was found that the crystal structure of the samples is hexagonal. Also, the average crystal size in the samples increased from 18 nm to about 33 nm as a result of adding oleic acid. The images obtained from FESEM show that the presence of oleic acid in the synthesis of nanoparticles caused it to affect the shape of the particles as a surface layer. Synthesized nanoparticles have a particle size between 20-100 nm, and with the increase of oleic acid, the particle size becomes more than 100 nm. FTIR spectroscopy revealed the effective bonding between LSMO nanoparticles and oleic acid, based on these results, it clearly shows the presence of oleic acid molecules on the surface of magnetic particles. In the investigation of magnetic properties, it was found that the presence of non-magnetic sodium oleate surface layer, which due to the addition of oleic acid on nanoparticles, the saturation magnetization value decreased from 38.55 emu/g to 28.46 emu/g.

In order to enhance the water flux and rejection of polyethersulfone (PES) membranes for membrane distillation process (MDP), we have developed a new PES membrane using a oleic acid as a hydrophobic agent. The synthesis membranes are fabricated via the phase inversion procedure and we examined the effects of oleic acid on hydrophobicity, porosity, surface roughness, morphology and MDP performance. For the membrane characterization, the produced membranes were characterized by contact angle, FTIR spectroscopy, field emission scanning electron microscopy, atomic force microscopy and porosity measurements. The outcomes demonstrated that the presence of the small amount of oleic acid in the membrane has led to an increment in the membrane hydrophobicity and porosity, and also improves the water flux and rejection of the MDP. The increment amount of oleic acid not only have no positive efficacy on the membrane performance, but can also reduce the MDP efficiency. In some areas, the excess concentration of oleic acid prevents the crossing of vapors evaporation through the cavities, so it will diminish the MDP flux.

In the previous works, the floatability of pyrolusite has been studied using different collectors but the capability of its separation from gangue minerals has not been considered significantly. In this research the flotation behavior of pyrolusite and calcite and their separation from each other using oleic acid as an anionic collector were investigated. The results showed that the pyrolusite flotation recovery contains two peaks at pHs 5 and 9 occurred due to oleate ions physisorption and chemisorptions mechanisms, respectively. Using 10-4 M oleic acid, the maximum flotation recovery of pyrolusite was obtained 30.8% at pH=9. At this condition, flotation recovery of calcite was 68%. It was found that copper sulfate (CuSO4.5H2O) acts as pyrolusite activator and calcite depressant agent in a dosage range of 250 to 1250 g/t. It depresses both minerals at high dosages. The best results were obtained using 1000 g/t copper sulfate in the presence of 10-4 M oleic acid at pH=8. At these condition the flotation recovery of pyrolusite and calcite are 83.6% and 38%, respectively. Copper sulfate increases the pyrolusite surface zeta potential and decreases the electrostatic repulsion forces; and results in the increase in oleate adsorption and flotation recovery. In the ore sample flotation tests, using copper sulfate the MnO grade of the concentrate was increased from 19.1 to 22.7% while the recovery was improved from 40.5 to 66.8%.