Papers by Keyword: Magnetite

Abstract: Reverse co-precipitation (RCP) in ambient atmosphere is one of the strategies to produce magnetite nanoparticles in a rapid, simple, and cost-effective synthesis route without applying temperature surfactants or inert gases. However, RCP of ferrous/ferric blended salt in sodium hydroxide (NaOH) solution in an oxidizing medium produced of maghemite as a dominant phase rather than magnetite because of the oxidation of Fe²⁺ to Fe³⁺ happened. Based on this background, an oil membrane layer-assisted reverse co-precipitation approach has been examined to synthesis of magnetite in ambient atmosphere at room temperature. The result showed that although addition of benzene as an oil membrane layer was effective to prevent oxidation of magnetite to maghemite, but the magnetite particle size for the samples from the oil membrane layer-assisted reverse co-precipitation method was much larger than that from a reverse co-precipitation method without addition of oil membrane layer.

Abstract: This study develops a fast and simple way to produce high purity magnetite (Fe₃O₄) microparticles from mill scale by using hydrogen reduction with the addition of vapour as a retarding agent. By optimising the reduction temperature and gas flow rate, the characterisations by X-ray diffractometry technique shown that the Fe₃O₄ fraction of over 93 wt.-% is shown at the reduction temperature of 550 – 650 oC with the flow rate of the 4.5-5.5 mol%H₂ + Ar gas + H₂O gas mixture from 100 – 200 ml/min. The highest Fe₃O₄ fraction of over 99 wt.-% can be achieved from the reduction with the mixed gas at 650 oC and the flow rate of 200 ml/min for 4 hour.

Abstract: We report on the results of a study of the lateral photovoltaic effect in theFe3O4/SiO2/n-Si structure grown on Si(001) and Si(111) substrates. It was found that in theFe3O4/SiO2/Si(001) structure the LPE sensitivity is a half times as much, and the photoresponseparameters are about 3 times less than those in the Fe3O4/SiO2/Si(111) structure. It is supposed thata higher sensitivity and faster photoresponse in the Fe3O4/SiO2/Si(001) structure, compared with theFe3O4/SiO2/Si(111) structure, are caused by a lower density of surface states at the SiO2/Si(001)interface than at the SiO2/Si(111) interface.

Abstract: We report on the results of a study of the lateral photovoltaic effect in the Fe₃O₄/SiO₂/n-Si(001) structure at temperatures of 300 and 122 K under continuous and pulsed illumination. It is found that when the temperature changes from 300 to 122 K, the LPE sensitivity decreases from 112 to 65 mV/mm. At pulsed illumination, an increase of rise time and a fall time is observed with decreasing temperature. From a consideration of the energy band diagrams and equivalent circuits of the Fe₃O₄/SiO₂/n-Si structure, it is assumed that the detected temperature effects of LPE are due to the strong dependence of the magnetite film resistance on temperature.

Abstract: Magnetic nanofluids are a category of nanomaterial which exhibit simultaneously liquid and superparamagnetic properties. These nanofluids are magnetic nanoparticles stably dispersed in liquid carrier. Magnetic nanoparticles with and without SiO₂ encapsulation have been successfully synthesized by co-precipitation method from ferrous and ferric precursors dispersed in various liquid. Fe₃O₄ nanoparticles were investigated by Zeta Potential and HR-TEM to determine the stability of nanoparticles, average particles size and microstructure of nanoparticles. From zeta potential measurements, is was found that the value of zeta potential for Fe₃O₄ dispersed in ethanol was ± 0,9 mV, while dispersed in di-water was ± 31,1 mV, indicating that nanoparticles Fe₃O₄ are more stable in DI-water. The increasing of zeta potential indicated the adsorption of negatively charged hydroxyl group to the surface of Fe₃O₄ nanoparticles. From XRD measurements, it was found that crystal quality of Fe₃O₄.SiO₂ sintering at 80 °C decreased by increasing the volume of tetraethyl orthosilicate (TEOS), while that samples sintering at 1000 °C have a good crystal quality with hexagonal phase of a-Fe₂O₃.SiO₂. From SQUID measurements, it was found that samples of Fe₃O₄.SiO₂ sintering at 80 °C with TEOS volumes of 1 ml and 2 ml showed a paramagnetic like while samples of a-Fe₂O₃.SiO₂ sintering at 1000 °C with the same TEOS volume showed ferrimagnetic properties.

Abstract: Metals removal from wastewater has become a major concern over the years due to the adverse effects of metals on organisms and environment. Adsorption is one of the safest, simplest, and most cost-effective methods for metals removal. The primary purpose of this study was to develop a magnetically separable activated carbon from pineapple crown leaf for zinc removal. Magnetic activated carbon (MAC) were characterized by SEM-EDX and FTIR. The ability of MAC to adsorb zinc ion was studied through variation of initial solution pH, concentration, and contact time. The optimum pH for zinc removal was four, while the equilibrium was reached after 180 min. In this condition, the percentage removal of zinc was 70.5%.

Abstract: One of the important characteristics of magnetic materials is the measurement of magnetic characteristics through Superconducting Quantum Interference Device (SQUID) especially magnetization temperature dependence M(T)_ZFC and MT_FC measurement. In this work, we reported magnetization temperature dependence measurements of magnetite nanoparticles without SiO₂ encapsulation (Fe₃O₄) and magnetite nanoparticles with SiO₂ encapsulation (Fe₃O₄.SiO₂) at the application of magnetic fields of 100 Oe. The nanoparticles magnetite was synthesized by co-precipitation method. It was calculated that the blocking temperature of magnetite nanoparticles Fe₃O₄ without and with SiO₂ encapsulation is 118.38 K and 209.03 K, respectively. The blocking temperatures of magnetic nanoparticles increase by SiO₂ encapsulation.

Abstract: Mercury pollution through water causes several dangerous diseases. Various efforts have been made to reduce mercury pollution. One of them is by using sorbent. Many ways to improve absorption efficiency, one of which is using magnetic sorbents. This study focused on the effect of grain size and the concentration of Mn_0.25Fe_2.75O₄@SiO₂ core-shell on mercury absorption efficiency. The synthesis of Mn_0.25Fe_2.75O₄@SiO₂ with 6 and 8 mL of TEOS was carried out through coprecipitation and sol-gel methods. The characterization using XRD, VSM, and FTIR was conducted to determine grain size, properties, and material functional groups proving that SiO₂ was successfully covered on the Fe₃O₄ surface. The percentage of absorption was found by using the AAS instrument. Diffraction data confirmed the presence of Fe₃O₄ and the amorphous SiO₂ phase. According to the Rietveld analysis of all samples demonstrated the particle size of Mn_0.25Fe_2.75O₄ around 11-12 nm. The Mn_0.25Fe_2.75O₄ core had superparamagnetic properties for magnetic separation, and the SiO₂ shell could protect the core of being oxidized or dissolved under acid condition. FTIR results showed the sample had a functional group of the main components of Fe-O and SiO₂ at a wavenumber of 420-507 cm^-1 and 801 cm^-1 (stretching) and 1078 cm^-1 (bending), respectively. The results of the mercury absorption test indicated that the smaller the grain size and the higher the concentration of TEOS, the percentage of mercury uptake would increase. In addition, the absorption percentage increased with the duration of absorption time given.

Abstract: The TiO₂/Fe₃O₄ nanoparticle has been successfully synthesized and the material is then applied as a photocatalyst to reduce Pb(II). The Fe₃O₄ was synthesized through sono-coprecipitation method using NH₄OH as a precipitating agent. The coating TiO₂ onto Fe₃O₄ was performed respectively via hydrolysis reaction and sol-gel process using ammonium sulfate and TTIP as a reagent of TiO₂. This study investigated several parameters such as the effect of time, equilibrium state and material responsiveness toward ultraviolet light. The XRD measurement indicated the presence of Fe₃O₄ and TiO₂ while TEM image displayed the photocatalyst had a nanosized particle with approximately 60 nm in size. An activity test at pH 4, the equilibrium of photoreduction process showed at 60 minutes. The kinetic parameter of Pb(II) reduction at various catalyst presented that TiO₂/Fe₃O₄ nanoparticle had better reduction rate constant than that of TiO₂. Reusing of TiO₂/Fe₃O₄ photocatalysts showed the results of Pb (II) photoreduction were not significantly decrease and the results of photocatalysis were still better than TiO₂.

Abstract: The mineral processing technology of Anshan-type iron ores has been developed in a rapid speed in recent years, and the combined flowsheet at the core of anionic reverse flotation has become a mainstream in the beneficiation of Anshan-type iron ores in china. With the successful application of this combined flowsheet, some obvious problems are also emerging. Such as high requirement of pulp temperature, complex reagent system, high cost of reagent consumption and so on. In view of this,we have carried out an experimental study on the separation of Anshan type iron ore by cationic reverse flotation . A new collector (named KBD) which is mixed amines have been developed . On this basis, the actual mineral separation experiment is carried out in the laboratory.With KBD as the collector,and starch and sodium hexametaphoshate as the depressant, has resulted in an iron concentrate of 68.16% and recovery rate of 89.71%. The determination of the electrokinetic potential and the infra-red spectroscopic analysis show that KBD can effectively and priorly adsorbed to the surface of quartz, and has greatly change the elecrtokinetic potential of quartz.The interaction of the depressing agent has increased the differences of the floatabilities in quartz and hermitite and changed the surface electric property so that the effective separation has been realized.