• Particle and aerosol research
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• v.13 no.1
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• pp.33-40
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• 2017

Cobalt-iron oxides have emerged as alternative electrode materials for supercapacitors because they have advantages of low cost, natural abundance, and environmental friendliness. Graphene loaded with cobalt ferrite ($CoFe_2O_4$) nanoparticles can exhibit enhanced specific capacitance. In this study, we present three-dimensional (3D) crumpled graphene (CGR) decorated with $CoFe_2O_4$ nanoparticles. The $CoFe_2O_4$-graphene composites were synthesized from a colloidal mixture of GO, iron (III) chloride hexahydrate ($FeCl_3{\cdot}6H_2O$) and cobalt chloride hexahydrate ($CoCl_2{\cdot}6H_2O$) respectively, via one step aerosol spray pyrolysis. Size of $CoFe_2O_4$ nanoparticles was ranged from 5 nm to 10 nm when loaded onto 500 nm CGR. The electrochemical performance of the $CoFe_2O_4$-graphene composites was examined. The $CoFe_2O_4$-graphene composite electrode showed the specific capacitance of $253F\;g^{-1}$.

• Bulletin of the Korean Chemical Society
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• v.24 no.2
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• pp.209-218
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• 2003

Ecosystems in the Keweenaw Peninsula region of Lake Superior, USA, were disturbed by over 500 million tons of copper-rich mine tailings during the period 1850-1968. Metals leaching from these mine residues have had dramatic effects on the ecosystems. Vast acreages of exposed tailings that are over 100 years old remain unvegetated because of the combination of metal toxicity, absence of nutrients, and temperature and water stress. Therefore, it is important to characterize and fractionate solid copper phases for assessing labile forms of copper in soils and sediments contaminated by the mining wastes. X-ray diffraction analyses indicate that calcite, quartz, hematite, orthoclase, and sanidine minerals are present as major minerals, whereas cuprite,tenorite, malachite, and chalcopyrite might be present as copper minerals in the mining wastes. Sequential extraction technique revealed that carbonate and oxide fractions were the largest pools of copper (ca. 50-80%) in lakeshore and wetland stamp sands whereas the organic matter fraction was the largest reservoir (ca. 32%) in the lake sediments. The concentrations of iron and copper were inversely correlated in the oxide fraction suggesting that copper may occur as a surface coating on iron oxides. As particle size and water contents decrease, the percent of the copper bound to the labile carbonate fraction increases.

• Resources Recycling
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• v.7 no.2
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• pp.23-30
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• 1998

Aiming to rccycle the valuable mrnpunenl such as iron oxiiles and carbon from blast turnace sludge, [he physlco-chemical property and classification charactei~stics by hydrocyclone wcie invcstigxted. Carbon in sludge wils analysed to bo cxated mostly in coarse particles of sludge as a form of graphite whereas zinc lnortly in fine particles as zinc sulfides. On thc contrxy, iron oxides wne proved to be in the form of hematite, magnetile without any segregations according to particlc sizes of sludge. From the results of classiIication test using hydmcyclane of 75 mm dm, the recovcry and dczincificatian rate of low zinc sludge wcrc in the range of 67.9-73.6%, and 72.7-86 8%, respectively.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.4
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• pp.281-287
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• 2017

Mill scale, an iron waste, was used to separate magnetite particles for the adsorption of phosphate from aqueous solution. Mill scale has a layered structure composed of wustite (FeO), magnetite ($Fe_3O_4$), and hematite ($Fe_2O_3$). Because magnetite shows the highest magnetic property among these iron oxides, it can be easily separated from the crushed mill scale particles. Several techniques were employed to characterize the separated particles. Mill scale-derived magnetite particles exhibited a strong uptake affinity to phosphate in a wide pH range of 3-7, with the maximum adsorptive removal of 100%, at the dosage of 1 g/L, pH 3-5. Langmuir isotherm model well described the equilibrium data, exhibiting maximum adsorption capacities for phosphate up to 4.95 and 8.79 mg/g at 298 and 308 K, respectively. From continuous operation of the packed-bed column reactor operated with different EBCT (empty bed contact time) and adsorbent particle size, the breakthrough of phosphate started after 8-22 days of operation. After regeneration of the column reactor with 0.1N NaOH solution, 95-98% of adsorbed phosphate could be detached from the column reactor.

• Progress in Superconductivity and Cryogenics
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• v.13 no.2
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• pp.21-24
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• 2011

Superconducting high gradient magnetic separation (HGMS) has advantages to treat wastewater because it can generate high magnetic field and achieve rapid purification. In this study superconducting HGMS was applied to remove impurities from the condenser water in thermal power plant. The condenser water contained mainly hematite and maghemite and it was highly magnetized than hematite. In the HGMS tests using a 6-T cryo-cooled Nb-Ti superconducting magnet, the turbidity of the condenser water was effectively reduced up to 99.6% and the result showed better performance than that of the 0.5-T permanent magnet test. The higher magnetic field was applied in the range of 1-6T, the more iron oxides were removed. The effect of magnetic filter configuration on the condenser water treatment was also investigated. Consequently superconducting HGMS system can be applicable to remove iron oxide impurities from condenser water in thermal power plant.

• Applied Chemistry for Engineering
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• v.30 no.2
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• pp.151-154
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• 2019

We report the effective fabrication processes for more practical monolith catalysts consisting of washcoated alumina on a cordierite honeycomb monolith (CHM) and iron oxides nanoparticles in the alumina prepared by a simple dry coating method. It is confirmed that iron oxide nanoparticles were well deposited into the mesopore of washcoated alumina which is formed on the corner wall of honeycomb channel, and the effect of annealing temperature was evaluated for carbon monoxide oxidation catalysts. $Fe_2O_3/{\gamma}-Al_2O_3/CHM$ catalysts annealed at $350^{\circ}C$ exhibited the most enhanced catalytic activity, 100% conversion efficiency at more than $200^{\circ}C$ operating temperature.

• Applied Chemistry for Engineering
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• v.31 no.1
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• pp.13-18
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• 2020

Iron oxide nanoparticles were microencapsulated using fibroin, a protein polymer of silk fiber, for theragnostic applications. The content of iron oxide was determined to be 4.28% by thermogravimetric analysis and 5.11% by magnetometer. A suspension of murine fibroblast 3T3 cells grown in medium supplemented with iron oxide-microcapsules turned clear in response to the magnetic force and the cells aggregated to the magnet direction. Neodymium magnets placed on the top of the culture dish, and attracted cells to the center of the culture surface. The cells collected on the culture surface aggregated to form a rough spheroid of 2 mm in a diameter after 72 h. In the outer layer of the cell aggregate, cells were relatively large and gathered together to form a dense tissue, but the central part was observed to undergo cell death due to the mass transfer restriction. In the outer layer, iron oxide-microcapsules were lined up like chains in the direction of magnetic force. Using microCT, it was demonstrated that the iron oxides inside the cell aggregate were not evenly distributed but biased to the magnetic direction.

• Journal of the Mineralogical Society of Korea
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• v.22 no.3
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• pp.177-189
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• 2009

Iron (oxyhydr)oxides commonly form as secondary minerals of high reactivity and large surface area resulting from alteration and weathering of primary minerals, and they are efficient sorbents for inorganic and organic contaminants. Accordingly, they have a great potential in industrial applications and are also of substantial interest in environmental sciences. Goethite (${\alpha}$-FeOOH) is one of the most ubiquitous and stable forms of iron (oxyhydr)oxides in terrestrial soils, sediments, and ore deposits, as well as a common weathering product in rocks of all types. This study focused on adsorption reaction as a main mechanism in scavenging arsenic using goethite. Goethite was synthesized in the laboratory to get high purity, and a variety of mineralogical and physicochemical features of goethite were measured and related to adsorption characteristics of arsenic. To compare differences in adsorption reactions between arsenic species, in addition, a variety of experiments to acquire adsorption isotherm, adsorption edges, and adsorption kinetics were accomplished. The point of zero charge (PZC) of the laboratory-synthesized goethite was measured to be 7.6, which value seems to be relatively higher, compared to those of other iron (oxyhydr)oxides. Its specific surface area appeared to be $29.2\;m^2/g$ and it is relatively smaller than those of other (oxyhydr)oxides. As a result, it was speculated that goethite shows a smaller adsorption capacity. It is likely that the affinity of goethite is much more larger for As(III) (arsenite) than for As(V) (arsenate), because As(III) was observed to be much more adsorbed on goethite than As(V) in equivalent pH conditions. When the adsorption of each arsenic species onto goethite was characterized in various of pH, the adsorption of As(III) was largest in neutral pH range (7.0~9.0) and decreased in both acidic and alkaline pH conditions. In the case of As(V), the adsorption appeared to be highest in the lowest pH condition, and then decreased with an increase of pH. This peculiarity of arsenic adsorption onto goethite might be caused by macroscopic electrostatic interactions due to variation in chemical speciation of arsenic and surface charge of goethite, and also it is significantly affected by change in pH. Parabolic diffusion model was adequate to effectively evaluate arsenic adsorption on goethite, and the regression results show that the kinetic constant of As(V) is larger than that of As(III).

• Journal of the Mineralogical Society of Korea
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• v.20 no.1 s.51
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• pp.47-60
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• 2007

While sedimentological researches on Western coastal tidal flats of Korea have been much pelformed previously, mineralogical and biogeochemical studies are beginning to be studied. The objectives of this study were to investigate mineralogical characteritics of the inter-tidal flat sediments and to explore phase transformation of iron(oxyhydr)oxides and biomineralization by metal-reducing bacteria enriched from the inter-tidal flat sediments from Muan, Jeollanam-do, Korea. Inter-tidal flat sediment samples were collected in Chungkye-myun and Haeje-myun, Muan-gun, Jeollanam-do. Particle size analyses were performed using the pipette method and sedimentation method. The separates including sand, silt and clay fractions were examined by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), and X-ray diffiaction (XRD). After enriching the metal-.educing bacteria from the into,-tidal flat sediments, the bacteria were used to study phase transformation of the synthesized iron (oxyhydr)oxides and iron biomineralization using lactate or glucose as the electron donors and Fe(III)-containing iron oxides as the electron accepters. Mineralogical studies showed that the sediments of tidal flats in Chung]rye-myun and Haeje-myun consist of quartz, plagioclase, microcline, biotite, kaolinite and illite. Biogeochemical researches showed that the metal-reducing bacteria enriched from the inter-tidal flat sediments reduced reddish brown akaganeite and mineralized nanometer-sized black magnetite. The bacteria also reduced the reddish brown ferrihydrite into black amorphous phases and reduced the yellowish goethite into greenish with formation of nm-sized phases. These results indicate that microbial Fe(III) reduction may play one of important roles in iron and carbon biogeochemistry as well as iron biomineralization in subsurface environments.

• Journal of Korean Society of Forest Science
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• v.90 no.5
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• pp.608-618
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• 2001

To understand the weathering processes of the soil by submicroscopic method is very important to realize the properties of the soils. In this study soil formation processes show every steps to the changes in chemical and mechanical properties and the submicroscopic characteristics of soil weathering on the profiles of forest soils derived from granite in southern part of Korea. Fecal pellets(SEM) are given a full detail of the positive activities of the forest soil animals; mainly invertebrates in the O horizon and the E horizon. External shapes of fecal pellets have been divided into five groups : spherical, ellipsoidal, cylindrical, platy and threadlike. But doughnutlike form of fecal pellets is observed in this study. The soluble and suspended materials in the soils move downwards by percolation from the A horizon to the B or the BC horizons, and result in the illuviation cutans(SEM) on the ped surface of the lower horizon and deposited stack of kaolinite. Illuviated cutans are deposited on the ped surface even in the depth of 312cm in the BC horizon as well as the Bt horizon and comprise of fine silt, coarse clay and fine clay. A lot of halloysites are observed on the cutan surface. Halloysite formation from feldspars has been well known but a lot of hallyosite formation are observed in this study. The formation were predicted by Jackson(1962), inferred by Wada and Kakuto(1983a, b) and proved evidently by Cho and Mermut(1992a, b). This also suggests that halloysites in the soils derived from granite are formed a lot from ferruginous chlorites. The release of Fe from the chlorite structure are significant pedogenic processes and newly formed Fe oxides imparted a red color to the soils. The iron oxides particles, which are ejected and recrystalized, aggregate thickly on the edge of the ferruginous chlorites, and this indicates the release of structural Fe from weathered chlorites. Hematites and goethites are frequent in the fine clay in this soils.