Cultivation of microalgae nannochloropsis sp. In palm oil mill effluent for biodiesel production

Extensive usage of fossil reserves resulted in rapid fossil fuel depletion. Biodiesel is one of the renewable energy alternatives designed to reduce reliance on fossil fuels. The generation of biodiesel from edible and non-edible crops is not identified as an ideal substitute to fossil fuels due to the competition for limited cultivable land proposed to cultivate crops for human consumption. To overcome the drawback, biodiesel is derived from the cultivation of microalgae. However, the cultivation of microalgae is costly as they require nutrients and water in a large amount. As a result, palm oil mill effluent (POME), which contains a large number of nutrients required for microalgae growth, is used as an alternative nutrition medium for microalgae cultivation while treating wastewater. In this study, attempts have been made to isolate and mass cultivate high lipid content microalgae from Teluk Cempedak, Kuantan coast, for biodiesel production. Among the collected samples, six microalgae were screened upon preliminary screening for morphological studies however green microalgae Nannochloropsis sp. was identified to be the most suitable microalgae with a high growth rate and abundant lipid content. Culture factors influencing the intracellular lipid body were investigated. The effect of different POME concentrations, photoperiod regimes and light-emitting diode (LED) light wavelengths were examined to determine the optimum factor for Nannochloropsis sp. growth and lipid enhancement. The mass cultivation under combined optimized culture factors of Nannochloropsis sp. followed by the Soxhlet extraction method yielded a lipid content of 61.5%. The extracted lipid was then transesterified with methanol to produce methyl esters (biodiesel) in 1.5 h, where potassium hydroxide (KOH) was used as a homogenous catalyst. Thin-layer chromatography (TLC) was done to ensure the conversion of Nannochloropsis sp. oil to biodiesel. The highest fatty acid methyl ester (FAME) formation from Nannochlropsis sp. was 80.24%. The output of gas chromatography- mass spectrometry (GC-MS) analysis proves that FAME comprises of high amount of oleic acid (C18:1) 66.13% and palmitic acid (C16:0) 12.38% respectively. Nannochloropsis sp. is a promising candidate for biodiesel production due to its composition of fatty acids and higher lipid content

Influence of Zn-Nb on the magnetic properties of barium hexaferrite

In the present study, BaFe12-2x Zn x Nb x O19 (x=0. 2, 0.4, 0.6 and 0.8) hexaferrites were prepared by the sol-gel technique and subsequent thermal treatment. The crystal structure, grain size, and magnetic properties were studied by means of X-ray diffraction (XRD), high-resolution scanning electron microscope (HR-SEM) and vibrating sample magnetometer (VSM). The X-ray diffraction analysis showed that the barium hexaferrite with small substitutions still maintained a hexagonal magneto-plumbite phase. It was found that the mean size of the grains increased with increasing substitution. The saturation magnetization increased slightly with increasing x, which was attributed to different preferential site occupation of Zn-Nb at low and high concentration ranges. The coercivity decreased with increasing x. Structural and magnetic characterizations of these ferrites provide significant information about their reactive physical properties

Microwave sintering of Ni-Cr doped strontium hexaferrite synthesized via sol-gel method

The magnetic behavior of Strontium hexaferrite ceramics with nominal composition SrFe12-2xNixCrxO19 (where x = 0.2, 0.4, 0.6, 0.8) samples are reported in this paper. Four samples were synthesized by the sol-gel method. The XRD analysis confirms the single phase and various parameters such as lattice constants (a and c), are calculated from the XRD data. Magnetic properties, such as specific saturation magnetization (Ms) and coercivity (Hc) are calculated from the hysteresis loops. Values of coercivity are found to increase up to the substitution level of x = 0.0-0.2 and then decreases continuously while that of saturation magnetization decrease continuously with increase in Ni-Cr concentration. The results show that microwave sintering requires about 75% less processing time than required by conventional method and still provides better magnetic properties

Synthesis, characterization and effects of citric acid and PVA on magnetic properties of CoFe2O4

Cobalt ferrite (CoFe2O4) particles were synthesized by sol-gel method using metal nitrates, citric acid (CA) and polyvinyl alcohol (PVA). X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), thermogravimetry/differential scanning calorimetry analysis and vibrating sample magnetometer were used to study the structural, thermal and magnetic properties of the CoFe2O4 powder. XRD results indicate that the resultant particles have crystalline, pure single phase spinel structure. From HR-SEM images, a systematic decrease in particle size is observed with an increase in PVA concentration, along with addition of CA. CA at various concentrations of PVA significantly enhance the magnetic properties of the materials

Preparation and magnetic properties of Ni-Cr doped strontium hexaferrite

The Ni-Cr-substituted M-type Strontium Hexaferrite such as SrFe12-2xNixCrxO19, with x =0.2, 0.4, 0.6, 0.8 mol% has been successfully prepared by the sol-gel process. The ferrites were systematically investigated by using powder X-Ray diffractometer (XRD), High Resolution Scanning Electron Microscope (HR-SEM) and Vibrating Sample Magnetometer (VSM). The XRD analysis confirms the single phase and lattice constants (a and c), have been calculated from the XRD data using powderX software. The lattice parameter was found to increase with increasing nickel-chromium concentration. Values of coercivity are found to increase up to the substitution level of x = 0.0-0.2 and then decrease slightly while that of saturation decrease continuously with increase in Ni-Cr concentration

Effect of TEA on the structural and magnetic properties of ferromagnetic ZnFe2O4 nanoparticles

Ferromagnetic ZnFe2O4 nanoparticles were synthesized by surfactant assisted hydrothermal method using different amount of triethylamine (TEA). The synthesized nanoparticles were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution transmission electron microscopy and vibrating sample magnetometer. The formation of single phase ZnFe2O4 was investigated by addition of different amount of TEA. Regular spinel structure was obtained for all synthesized product except for lower amount of TEA, owing to the less alkaline atmosphere. All the synthesized nanoparticles were spherical in shape with a small aggregation. Observed size of the nanoparticles was 10 nm as determined from TEM measurement for the sample synthesized with a higher amount of TEA. Room temperature ferromagnetic behavior was observed in all the samples

Wurtzite ZnSe quantum dots: synthesis, characterization and PL properties

A facile method for synthesis of monodispersed, starch-capped ZnSe nanoparticles at room temperature is being reported. The nanoparticles exhibited strong quantum confinement effect with respect to the bulk ZnSe. The transmission electron microscopy image indicated that the particles were well dispersed and spherical in shape. The X-ray diffraction analysis showed that the ZnSe nanoparticles were of the wurtzite structure, with average particle diameter of about 3.6 nm. The Fourier transform infrared spectrum confirmed the presence of starch as passivating agent

Study of CoFe2O4 particles synthesized with various concentrations of PVP polymer

CoFe2O4 particles were synthesized using metallic nitrates and polyvinylpyrolidone (PVP) using sol-gel method followed by calcination for 2 h at 960 C. PVP performed as a surfactant and the effect of various concentrations of PVP on the resultant CoFe2O4 powder was studied. The resultant samples were characterized by XRD, TG/DSC, HR-SEM and VSM. X-ray diffraction results indicated the crystalline phase of CoFe2O4 particles and impurity phase of hematite was observed for higher PVP concentrations. SEM images demonstrated the influence of PVP concentration on the size of the particles. By VSM measurements, the variations in magnetic properties with respect to PVP concentration are studied. All the magnetic characteristics H c, M s and M r increased for 6 wt% and 15 wt% of PVP concentration. The CoFe 2O4 particles synthesized with the optimum concentration of PVP may be very attractive for potential applications because of their outstanding magnetic properties (M s =81.1 Am2/kg, H c =831 Gauss)

Study of CoFe2O4 particles synthesized with various concentrations of PVP polymer

CoFe2O4 particles were synthesized using metallic nitrates and polyvinylpyrolidone (PVP) using sol-gel method followed by calcination for 2 h at 960 C. PVP performed as a surfactant and the effect of various concentrations of PVP on the resultant CoFe2O4 powder was studied. The resultant samples were characterized by XRD, TG/DSC, HR-SEM and VSM. X-ray diffraction results indicated the crystalline phase of CoFe2O4 particles and impurity phase of hematite was observed for higher PVP concentrations. SEM images demonstrated the influence of PVP concentration on the size of the particles. By VSM measurements, the variations in magnetic properties with respect to PVP concentration are studied. All the magnetic characteristics H c, M s and M r increased for 6 wt% and 15 wt% of PVP concentration. The CoFe 2O4 particles synthesized with the optimum concentration of PVP may be very attractive for potential applications because of their outstanding magnetic properties (M s =81.1 Am2/kg, H c =831 Gauss)

Sintering temperature dependence of optimized microstructure formation of BaFe12O19 using sol–gel method

In an attempt to obtain the best possible properties of barium hexaferrite (BaFe12O19), the sol–gel synthesis method was chosen and, the optimum sintering conditions were established. The effects of the sintering temperature on the structural, morphological and magnetic properties of hexaferrite were studied. X-ray analysis indicates that the sintered samples (1,000–1,150 °C) remained in the hexagonal structure. From this analysis, no secondary phases are identified. The effect of sintering temperature on the grain growth of BaFeBaFe12O19 is confirmed by the microstructure using HR-SEM and is in good agreement with the XRD analysis based on the peak intensity of the (107) plane. The samples sintered at 1,150 °C showed the densities as ~93 % of theoretical density. Sintering temperature affected the grains in compact samples. The results show that homogeneous and dense BaFeBaFe12O19 ceramics obtained at a lower sintering temperature of 1,150 °C which is lower than the normally reported sintering temperature of ≥1,200 °C. The thermal treatment can markedly affect the grains in compact samples