Magnetic Goethite Research Articles

Effect of magnitude of voltage and magnetic field on memory effect in nematic phase of liquid crystal and their composites with aerosil and goethite nanoparticles

In liquid crystals doped with aerosil nanoparticles, the state induced by applying voltage or a magnetic field stays remembered after removing the power. The ability to remember the induced state after removing the power is known as non-volatile memory effect. The present paper describes how the magnitude of voltage and magnetic field affects the memory effect in the nematic phase of liquid crystal 4-cyano-4′-pentylbiphenyl doped with aerosil nanoparticles and with a combination of aerosil and magnetic goethite nanoparticles. Capacitance measurements revealed increasing in memory when the magnitude of voltage and magnetic field is increased. Applying fields with various magnitudes provides the possibility of fabrication a multilevel memory device based on the response to electric or magnetic field. The memory can be erased, and the initial state can be restored by heating the composites to the same temperature.

Effect of temperature on memory effect in nematic phase of liquid crystal and their composites with aerosil and geothite nanoparticles

Liquid crystal doped with aerosil nanoparticles is known for exhibiting an electromechanical memory effect. After exposing the composite to the electric field the state induced by the electric field stays remembered due to the presence of aerosil nanoparticles. In this paper, we investigated the memory effect induced by electric and magnetic fields. Liquid crystal 4-cyano-4′-pentylbiphenyl doped with non-magnetic aerosil nanoparticles and a mixture of aerosil nanoparticles and elongated magnetic goethite nanoparticles were explored via capacitance measurements. Studied systems exhibited hysteresis in capacitance-voltage and capacitance-magnetic field dependences. The measurements revealed a great impact of temperature and heating/cooling rate on the hysteresis of the system. Observed electromechanical and magnetomechanical memory effect provides potential use of the system as voltage-driven or magnetic field-driven non-volatile memory devices.

Effective capture of aqueous uranium using a novel magnetic goethite: Properties and mechanism

A large amount of uranium-containing wastewater is produced by the nuclear industry, which causes harm to human health and the environment. Goethite (α-FeOOH) is highly insoluble in water and has a net positive surface charge, making it an effective sorbent for metal–anion complexes in aqueous solutions. In this study, goethite (α-FeOOH) and Fe2+-modified magnetic goethite (M-α-FeOOH) were prepared using an easy one-pot chemical precipitation method and used to remove uranium from solution. The adsorbents were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), BET surface area analysis, fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometry (VSM). When Fe2+ partially substitutes for Fe3+, the material is magnetic, has a larger specific surface area and can be rapidly separated in a magnetic field. The uranium adsorption performance of M-α-FeOOH was substantially better than that of α-FeOOH, and its maximum adsorption capacity increased by 46.09%. The data fitted well with the quasi-second order kinetic model and the Langmuir isothermal adsorption model. According to the results of this study, the increase in the uranium removal performance of M-α-FeOOH was attributed to its higher specific surface area, better dispersion, and larger quantity of activated adsorption sites. These results, along with its low-cost, environmentally friendly, and facile synthesis, reveal M-α-FeOOH is a promising material for uranium capture.

Removal of Cr(VI) from Wastewater by a Novel Adsorbent of Magnetic Goethite: Adsorption Performance and Adsorbent Characterisation

AbstractA novel adsorbent of magnetic goethite was prepared by neutralisation hydrolysis and employed for Cr(VI) adsorption from aqueous solution. The magnetic goethite adsorbent was characterised by using scanning electron microscopy (SEM), X‐ray diffractometer (XRD), vibrating sample magnetometer (VSM), fourier transform infrared (FTIR), brunauer‐Emmett‐Teller (BET) and X‐ray photoelectron spectroscopy (XPS) method. VSM showed that the prepared adsorbents are super‐paramagnetic iron hydroxide. FTIR spectra revealed that magnetic goethite have ‐OH and other functional groups. The effects of various factors, including pH, adsorbent dosage, initial concentration, and ion concentration, were evaluated. Under the conditions of pH 3, 4 g/L magnetic goethite, 20 mg/L Cr(VI) concentration, and 0.01 mol/L NaNO3, the removal efficiency of Cr (VI) reached 88.2% and the adsorption capacity of the adsorbent reached 4.32 mg/g. The adsorption kinetic tests showed that the adsorption of Cr(VI) on the adsorbent matched well with pseudo‐second‐order kinetics, indicating the occurrence of chemisorption. The fitting of the Langmuir isotherm model showed that the adsorption of Cr(VI) on magnetic goethite was monolayer adsorption. On the other hand, thermodynamic studies conjectured that the adsorption processes of magnetic goethite for Cr(VI) was endothermic and spontaneous. These results suggest that magnetic goethite has great potential for the removal of heavy metals from wastewater.

Magnetic methods in tracing soil erosion, Kharkov Region, Ukraine

Magnetic measurements of soils are an effective research tool in assessing soil erosion. This approach is based on detecting layers showing different magnetic properties in vertical soil profiles and lateral catenas. The objective of this research is to compile data on magnetic susceptibility (MS) of soils in Eastern Ukraine to assess the soil erosion rates. The chernozems of Tcherkascy Tishki (Kharkov Region, Ukraine) have undergone a field crop rotation without proper soil conservation technologies being applied. We conducted an intrinsic element grouping of the magnetic susceptibility values and demonstrated that they can be used as MS cartograms in soil erosion mapping. The study showed a strong correlation between the MS values and the erosion index. MS and the erosion index were found to correlate with the humus content. Magnetic mineralogical analyses suggest the presence of highly magnetic minerals (magnetite and maghemite) as well as weakly magnetic goethite, ferrihydrite, and hematite. Stable pseudosingle-domain (PSD), single-domain (SD), and superparamagnetic (SP) grains of pedogenic origin dominate in the studied chernozems. Being an effective, quick and low cost alternative, magnetic methods can be successfully used in the soil erosion investigations.

Magnetic Separation and Recycling of Goethite and Calcium Sulfate in Zinc Hydrometallurgy in the Presence of Maghemite Fine Particles

Goethite (α-FeOOH) and calcium sulfate (CaSO4·2H2O) are the main solid constituents of the iron oxide residues in zinc hydrometallurgy by the goethite process. Impounding these residues in tailings ponds is costly to maintain and causes a great threat to the local environment. In this study, magnetic separation was applied to separating goethite from calcium sulfate with maghemite (γ-Fe2O3) fine particles as the carrier, which were prepared by roasting −1 μm pure magnetite mineral particles. The SEM images and XRD patterns indicated the precipitation of goethite on maghemite fine particles in the goethite process, which made the goethite aggregates magnetic, while the calcium sulfate formed nonmagnetic bulk precipitates. The magnetic goethite–maghemite aggregates were then separated effectively from calcium sulfate precipitates using a magnetic drum separator. The recovery of Fe and Ca to their corresponding products was 93.2% and 91.9%, respectively. The removal of S and As from goethite precipitates was studied by roasting with coal powder. Under the optimum conditions of the coke powder to the residue mass ratio of 4% and 1100 °C, 99.3% S and 99.5% As were removed while the goethite precipitates reached the standard of ironmaking raw materials. After drying, the calcium sulfate precipitates are used to produce cement and building materials.

Simple and Efficient Separation of Magnetic Minerals From Speleothems and Other Carbonates

Abstract Trace concentrations of iron oxide minerals in carbonate sediments can preserve fine details about Earth processes, from high-resolution recordings of the Earth's ancient magnetic field to microscopic remnants of extraterrestrial impacts. This paper presents a novel flask extraction method which uses a neodymium magnet and an orbital shaker for simple and efficient separation of magnetic minerals from carbonate sediments. A mineral assemblage of magnetic standards (titanomagnetite, magnetite, goethite, and hematite) combined with other mineral standards (kaolinite, quartz, and nanoscale TiO2) was subjected to the extraction procedure and compared to a natural speleothem sample. Exposure of the magnetic standards to a mildly acidic acetate buffer (pH ∼ 4) did not cause physical or chemical alteration. The strongly magnetic minerals were reproducibly extracted, with greater than 90% efficiency (by mass), from mixtures of the mineral standards. XRD and low-temperature magnetic characterization demonstrated phase purity of the extracts. Quantitative comparison with two commonly used literature methods showed that the flask extraction method was more reproducible and efficient. The addition of surfactant (Na(PO3)6) did not significantly improve extraction efficiency. Sequential dissolution and flask extraction of a simulated speleothem containing magnetic particles resulted in consistent extraction efficiencies for samples containing large (> 1 µm) strongly magnetic grains, but a reduction in efficiency was observed for smaller (< 1 µm) grain sizes. No method successfully extracted the weakly magnetic goethite and hematite. However, unprecedented, representative characterization of these minerals was possible through quantitative analysis of the remainder after the collection of the magnetic extract. This approach may facilitate detailed characterization of a wide range of carbonates, such as pelagic limestone, dolostone, unlithified carbonate ooze, speleothems, and freshwater and pedogenic carbonates. Such mineral extractions can lead to new insights into paleoenvironmental processes as well as an improved understanding of the recording of the Earth's magnetic field.

The magnetic mechanism of paleosol S5 in the Baoji section of the southern Chinese Loess Plateau

In the central Chinese Loess Plateau (CLP), the magnetic susceptibility has the highest value in the S5 paleosol unit. However, at the southern of the CLP, such as in Baoji, the magnetic susceptibility value in the S5 paleosol unit is on the lower range of the top 6 paleosols (S0, S1…S5). The studies of rock magnetism and geochemistry showed that the Baoji S5 experienced a stronger pedogenesis and chemical weathering than the S3. The paleosol S3 was formed under an oxidizing environment where the maghemite and hematite are formed simultaneously. Maghemite is the main contributor to magnetic enhancement. However, the concentrations of maghemite in the S5 are lower than in the S3. With the development of pedogenesis, the proportion of the maghemite component decreased in the S5, while the concentrations of anti-ferromagnetic minerals (mainly goethite) increased. In the field, measurable amounts of dark brown iron-manganese cutans can be observed on the cranny surface of S5. These indicate that the iron–manganese elements in the S5 were assembled, and pedogenesis occurred intermittently between wet and dry, and strong leaching soil conditions. This may have led to fine-grained magnetite, maghemite and hematite, which were gradually converted into weak magnetic goethite, therefore resulting in the lower magnetic susceptibility of S5.

Rapid and direct magnetization of goethite ore roasted by biomass fuel

Biomass is a renewable and carbon neutral solid fuel. Utilization of biomass in iron ore roasting process as heating agent and reducing agent contributes to energy conservation and emission reduction, and can partially replace for coal and coke. The biomass instead of coke was mixed together with iron ore powder from the north of Hainan province into ball roasting process to investigate the effects of mixture composition, reduction temperature, reaction time, the thermal reduction and magnetic properties of the mixture. The results show that the reduction temperature, reaction time and dosage of the biomass are correlated to the quality of the reduction and the magnetism of the iron ore, within the experimental conditions. The mechanism of the biomass reducing the weakly magnetic goethite into stronger magnetic iron oxide has been discussed. The results show that the goethite ores is dramatically reduced and magnetized by about 20 wt.% biomass at low roasting temperature. Application of biomass energy in iron ores roasting process is prospective to the effective use of biomass and for decreasing the consumption of fossil fuels in the steelmaking process.

Field sludge characterization obtained from inner of pipelines

Physicochemical characterization of sludge obtained from refined hydrocarbons transmission pipeline was carried out through Mössbauer spectroscopy and X-ray diffraction. The Mössbauer and X-ray patterns indicate the presence of corrosion products composed of different iron oxide and sulfide phases. Hematite (α-Fe 2O 3), magnetite (Fe 3O 4), maghemite (γ-Fe 2O 3), magnetic and superparamagnetic goethite (α-FeOOH), pyrrhotite (Fe 1− x S), akaganeite (β-FeOOH), and lepidocrocite (γ-FeOOH) were identified as corrosion products in samples obtained from pipeline transporting Magna and Premium gasoline. For diesel transmission pipeline, hematite, magnetite, and magnetic goethite were identified. Corrosion products follow a simple reaction mechanism of steel dissolution in aerated aqueous media at a near-neutral pH. Chemical composition of the corrosion products depends on H 2O and sulfur inherent in fluids (traces). These results can be useful for decision-making with regard to pipeline corrosion control.

On the Analysis of the Mössbauer Spectra of the Rust Converted by Tannic and Phosphoric Acids

In previous work, we reported results on the action of rust converters based on a mixture of tannic and phosphoric acids, upon the rust formed on mild steel coupons. There, the rust before and after the application of converters were characterized by room-temperature Mossbauer spectroscopy, among other techniques. The present work is an extension of this one, and additional MS at 77 K, 130 K and 300 K for some samples are presented. Special emphasis is given to the methodology of analysis. Our results confirm previous findings that an important portion of the magnetite remains without conversion. New information was also derived: (i) the converters seem to affect more the magnetite octahedral (B) than the tetrahedral (A) sites; (ii) among the magnetite B sites, the Fe2+ is the most affected; (iii) at least 31% of magnetic goethite at 77 K is transformed by the converter; and (iv) the presence of an additional phase identified as ferrous phosphate, could be resolved unambiguously only at these lower temperatures.

A process for enhanced removal of iron from bauxite ores

A process to remove iron from bauxite ore is described in which the ore is first finely crushed, calcined, and contacted with a reducing gas to convert iron present as very weakly magnetic goethite or hematite to magnetite or elemental iron. The ore is then passed through a magnetic separator to remove the iron. A 1.5% Fe 2O 3 product was produced from an Alabama bauxite ore analyzing 2.7% Fe 2O 3. Calcination and H 2 reduction at 800°C and single-pass magnetic separation at 4000 Gs were used. There was 95% recovery of the iron-free bauxite starting material, and the magnetic fraction contained 21% Fe 2O 3.