• Advances in nano research
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• v.16 no.1
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• pp.41-52
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• 2024

In this study, rare-earth orthoferrites LnFeO₃ were synthesized using a facile hydrothermal reaction and their visible-light-induced photo-Fenton degradation of organics was optimized through Ln variation (Ln = La, Pr, or Gd). The morphological, structural, and chemical characteristics of as-prepared samples were examined in detail by using different methods, including XRD, SEM, TEM, XPS, etc. On the other side, under visible light illumination, the photo-Fenton-like catalytic activities of LnFeO₃ were assessed in terms of the removal of selected organic models, i.e., pharmaceuticals (ketoprofen and tetracycline) and dyes (rhodamine B and methyl orange). As compared with PrFeO₃ or GdFeO₃, the sample of LaFeO₃ displayed more structural distortion, larger specific surface area, and narrower band gap, resulting in its higher photo-Fenton-like catalytic activity toward the degradation of organics. In organic-containing solution, in which the initial solution pH = 5, catalyst dosage = 1 g/L and H₂O₂ concentration = 10 mM, 98.2% of rhodamine B, 31.1% of methyl orange, 67.7% of ketoprofen, or 96.4% of tetracycline was removed after 90-min exposure to simulated visible light. Our findings revealed that variation of Ln site on rare-earth orthoferrites was an effective strategy for optimizing their organic removal via visible-light-induced photo-Fenton reaction.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.1
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• pp.21-30
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• 2006

[ $M/Fe_2O_3$ ] (M=Rh, Ce and Zr) mixed oxides were prepared using urea method to develop a medium for chemical hydrogen storage by their redox cycles. And their redox behaviors by repeated cycles were studied using temperature programmed reaction(TPR) technique. Additives such as Rh, Ce and Zr were added to iron oxides in order to lower the reaction temperature for reduction by hydrogen and re-oxidation by water-splitting. From the results, concentration of urea used as a precipitant had little effect on particle size and reduction property of iron oxide. TPR patterns of iron oxide consisted of two reduction peaks due to the course of $Fe_2O_3\;{\rightarrow}\;Fe_3O_4\;{\rightarrow}\;Fe$. The results of repeated redox tests showed that Rh added to iron oxide have an effect on lowering the re-oxidation temperature by water-splitting. Meanwhile, Ce and Zr additives played an important role in prevention of deactivation by repeated cycles. Finally, Fe-oxide(Rh, Ce, Zr) sample added with Rh, Ce and Zr showed the lowest re-oxidation temperature by water-splitting and maintained high $H_2$ recovery in spite of the repeated redox cycles. Consequently, it is expected that Fe-oxide(Rh, Ce, Zr) sample can be a feasible medium for chemical hydrogen storage using redox cycle of iron oxide.

• Journal of Sensor Science and Technology
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• v.17 no.4
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• pp.281-288
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• 2008

Polyacrylonitrile(PAN)/metal oxide(MO) nanocomposite mats with a thickness of 0.12 mm were electrospun by adding 0 to 10 wt% of MO nanoparticles ($Fe_2O_3$, ZnO, $SnO_2$, $Sb_2O_3-SnO_2$) into PAN. Pt electrode was patterned on $Al_2O_3$ substrate by DC sputtering and then the PAN(/MO) mats on the Pt patterned $Al_2O_3$ were electrically wired to investigate the $CO_2$ gas sensing properties. As the MO content rose, the fiber diameter decreased due to the presence of lumps caused by the presence of MOs in the fiber. The PAN/2% ZnO mat revealed a faster response time of 93 s and a relatively short recovery of 54 s with a ${\Delta}R$ of 0.031 M${\Omega}$ at a $CO_2$ concentration of 200 ppm. The difference in sensitivity was not observed significantly for the PAN/MO fiber mats in the $CO_2$ concentration range of 100 to 500 ppm. It can be concluded that an appropriate amount of MO nanoparticles in the PAN backbone leads to improvement of the $CO_2$ gas sensing properties.

• Journal of the Mineralogical Society of Korea
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• v.27 no.1
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• pp.53-62
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• 2014

In order to remove Fe impurity from low-grade pyrophyllite ore, the effect of certain variables such as particle size, concentration of sulfuric acid, amount of ammonium sulfate, added hydrogen peroxide, and temperature were studied. The euhedral cubic pyrites were observed in the low-grade pyrophyllite ore by reflected light microscopy, and quartz and dickite were identified in the sample by XRD analysis. The results of the Fe removal experiments showed that the best Fe removal parameters were when the particle size was at -325 mesh, the addition of $H_2SO_4$, $(NH_4)_2SO_4$ and $H_2O_2$ was at a 2.0 M, 10.0 g/l, and 3.0 M concentration, respectively, and at a $70^{\circ}C$ leaching temperature. In the dissolution kinetics analysis, the dissolution of Fe from the pyrite surface was a controlled chemical reaction, and the Fe dissolution reaction was proportioned to 0.066/R, $[H_2SO_4]^{1.156}$, $[(NH_4)_2SO_4]^{0.745}$, $[H_2O_2]^{0.428}$.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.350-356
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• 2013

Dissolution of ferronickel slag depending on aging condition was studied. Ferronickel slag typically contains 54.05% $SiO_2$, 34.33% MgO, and 5.51% $Fe_2O_3$. The main structure composite was similar to Enstatite [(Mg, $Fe^{2+}$ )$SiO_3$]. Ferronickel slag aging was made in 3 months under various experimental conditions, in water, bubbling water and wetting air. The most effective aging condition was the wetting air treatment. In this condition, the dissolving concentration of Mg and Fe was 80.0% and 75.1% respectively. The XRD and SEM data revealed that the wetting air condition also showed the biggest structural damage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.38-41
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• 2004

The oxidizer plays an important role in the metal chemical mechanical polishing(CMP) slurry. Currently, the oxidizer used in CMP slurry is nearly divided into several kinds such as $Fe(NO_3)_3$, $H_2O_2$, $KIO_3$, and $H_5IO_6$. It is generally known that oxidizer character of $H_2O_2$ is more effective than other oxidizers. In this work, we have been studied the characteristics for the $H_2O_2$ concentration of copper slurry, which can applicable in the recent semiconductor manufacturing process. Also, it plays an important role in the planarization of copper films using copper slurries during micro-electronic device fabrication. In this work, we confirmed that removal rate of Cu/TaN changed by $H_2O_2$ concentration on copper slurry. And we used $KMnO_4$ in the measurement method of $H_2O_2$. In analysis results, we confirmed that the difference of results is large. We thought that the difference was due to organic component existence. So in titration method of $H_2O_2$ concentration, we used $Na_2S_2O_3$ instead of $KMnO_4$ as solution. Consequently, using the titration method, we could calculate correct data reduced error. And $H_2O_2$ concentration has been adjusted to the target concentration of 0.1 wt%.

• Toxicological Research
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• v.23 no.3
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• pp.279-287
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• 2007

Copper (Cu) is an essential trace element indispensable for brain development and function; either excess or deficiency in Cu can cause brain malfunction. While it is known that Cu and Fe homeostasis are strictly regulated in the brain, the question as to how systemic Fe status may influence brain Cu distribution was poorly understood. This study was designed to test the hypothesis that dietary Fe condition affects Cu transport into the brain, leading to an altered brain distribution of Cu. Rats were divided into 3 groups; an Fe-deficient (Fe-D) group which received an Fe-D diet ($3{\sim}5 mg$ Fe/kg), a control group that was fed with normal diet (35mg Fe/kg), and an Fe-overload group whose diet contained an Fe-O diet (20g carbonyl Fe/kg). Following a 4-week treatment, the concentration of Cu/Fe in serum, CSF (cerebrospinal fluid) and brain were determined by AAS, and the uptake rates of Cu into choroids plexus (CP), CSF, brain capillary and parenchyma were determined by an in situ brain perfusion, followed by capillary depletion. In Fe-D and Fe-O, serum Fe level decreased by 91% (p<0.01) and increased by 131% (p<0.01), respectively, in comparison to controls. Fe concentrations in all brain regions tested (frontal cortex, striatum, hippocampus, mid brain, and cerebellum) were lower than those of controls in Fe-D rats (p<0.05), but not changed in Fe-O rats. In Fe-D animals, serum and CSF Cu were not affected, while brain Cu levels in all tested regions (frontal cortex, striatum, hippocampus, mid brain, and cerebellum) were significantly increased (p<0.05). Likewise, the unidirectional transport rate constants $(K_{in})$ of Cu in CP, CSF, brain capillary and parenchyma were significantly increased (p<0.05) in the Fe-D rats. In contrast, with Fe-O, serum, CSF and brain Cu concentrations were significantly decreased as compared to controls (p<0.05). Cu transport was no significant change of Cu transport of serum in Fe-O rats. The mRNA levels of five Cu-related transporters were not affected by Fe status except DMT1 in the CP, which was increased in Fe-D and decreased in Fe-O. Our data suggest that Cu transport into brain and ensuing brain Cu levels are regulated by systemic Fe status. Fe deficiency appears to augment Cu transport by brain barriers, leading to an accumulation of Cu in brain parenchyma.

• Bulletin of the Korean Chemical Society
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• v.15 no.3
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• pp.256-260
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• 1994

Perovskite type oxides of the $Sr_xHo_{1-x}FeO_{3-y}$ system with compositions of x=0.00, 0.25, 0.50, 0.75, and 1.00 have been prepared at 1200$^{\circ}$C in air. X-ray powder diffraction assigns the compositions with x=0.00 and 0.25 to the orthorhombic crystal system and those with x=0.50, 0.75, and 1.00 to the cubic one. The unit cell volumes of solid solutions increase with x in the system. Nonstoichiometric chemical formulas were determined by Mohr salt titration. The mole ratio of $Fe^{4+}$ ions to total iron ions and the concentration of oxygen ion vacancies increase with x. Mossbauer spectra for the compositions of x= 0.00, 0.25, and 0.50 show six lines indicating the presence of $Fe^{3+}$ ions in the octahedral site. However, the presence of $Fe^{4+}$ ions may also be detected in the spectra for the compositions with x=0.25 and x=0.50. In the compositions with x=0.75 and 1.00, single line patterns show also the mixed valence state of $Fe^{3+}$ and $Fe^{4+}$ ions. The electrical conductivity in the temperature range of -100$^{\circ}$C to 100$^{\circ}$C under atmospheric air pressure increases sharply with x but the activation energy decreases with the mole ratio of $Fe^{4+}$ ion. The conduction mechanism of the perovskite system seems to be hopping of the conduction electrons between the mixed valence iron ions.

• Journal of Environmental Health Sciences
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• v.27 no.4
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• pp.63-71
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• 2001

PM 2.5/ samples were measured at two sites, Hadan(suburban site) and Anrak (roadside site) in Busan area. PM 2.5/ sampling was performed for 24-hour intervals by the FH9.5 particulate sampler. Aerosol samples were collected on PTFE filter. A total of 60 particulate samples were collected, dad samples were measured for Particulate mass concentration, metallic elements (Cr, Mn, Ni. Cu. Se, Fe, Pb, and Zn) and waer-soluble elements (C $l^{[-10]}$ , N $O_{3}$$^{[-10]}$ ,S $O_{4}$$^{2-}$, N $H_{4}$$^{+}$, $Ca_{2}$$^{+}$, $Mg_{2}$$^{+}$ and $^{+}$.Mass concentration in Hadan ranged 24.23~57.12 $\mu\textrm{g}$/㎥ and 60.22~72.12 $\mu\textrm{g}$/㎥m Yellow Sand Events. Major cations in Hadan and Anrak site is N $H_{4}$$^{+}$and N $a^{+}$ respectively. SO42$^{[-10]}$ was the abundant specie in the PM 2.5 fraction for Hadan site an dAnrak site. Hadan site showed igher concentration in S $O_{4}$$^{2.1}$ and N $H_{4}$ $^{+}$ In Anrak site the concentration of S $O_{4}$/sip 2-/and N $a^{+}$ was higher than other ions Prominent metallic elements were Fe and Pb in two sites. Principal component analysis showed that main source of PM 2.5 aerosol particles was non-metal related source which was resulted in relating elements as Cr, Ni, and Pb at Hadan site, Anrak site also has resulted PM2.5 aerosol paricles source, which was related its element like Zn, and Ni,. The SAS package analysis also showed that long-range transport effect at Hadan area due to Yellow Sand Event by the prevailing weaterlies.ling weaterlies.

• Journal of the Korean Ceramic Society
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• v.24 no.5
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• pp.431-436
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• 1987

High purity Al2O3 has been extracted from serlcite of clayminerals, selicite was treated by H2SO4(2N∼18N) solution, NH4OH treatment(PH8.5∼10.0) and metallic impurities such as Fe were removed by NaOH treatment. The tendency of extraction yield of ${\alpha}$-Al2O3 have been investigated by relating reaction time, acid concentration. Reaction products were analyzed by DT-TGA, chemical analysis and X-ray diffractometer. Prepared ${\alpha}$-Al2O3 power is fired in air at 1400$^{\circ}C$, 1600$^{\circ}C$ 2hr. The results are as follows; 1. The most suitable extracting conditions of ${\alpha}$-Al2O3 from Selicite were N-H2SO4, 120 min acidtreating time. 2. The optimum pH condition was 9.0. 3. Physical properties of sintered Al2O3 bodies were as follows. Relative density is 99%. Water absorption is 0.26%. Rock well hardness is 89.