• Journal of Sensor Science and Technology
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• v.25 no.1
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• pp.41-45
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• 2016

In this study, LET (Linear Energy Transfer) calibration of CR-39 SSNTD (Solid State Nuclear Track Detector) was performed using 500 MeV/u Fe heavy ions in HIMAC (Heavy Ion Medical Accelerator) for high LET radiation dosimetry. The irradiated CR-39 SSNDT were etched according JAXA (Japan Aerospace Exploration Agency) etching conditions. And the etched SSNTD were analyzed by using Image J. Determined dose-mean lineal energy ($\overline{y_D}$) of 500 MeV/u Fe is about 283.3 keV/um by using the CR-39 SSNTD. This value is very similar result compare to the results calculated by GEANT4 Monte Carlo simulation and measured with TEPC active radiation detector. We confirmed that the CR-39 SSNTD was useful for high LET radiation dosimetry such as heavy iron ions.

• Korean Journal of Metals and Materials
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• v.50 no.3
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• pp.218-223
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• 2012

Fe-(8.5, 18.5, 28.3, 36.9) wt% Cr alloys were corroded between 600 and $800^{\circ}C$ for up to 70 h in a 1 atm gas mixture that consisted of 0.0242 atm of $H_2S$, 0.031 atm of water vapor, and 0.9448 atm of nitrogen gas. Their corrosion resistance increased with an increment in the Cr content. The Fe-8.5%Cr alloy corroded fast, forming thick, fragile, nonadherent scales that consisted primarily of an outer FeS layer and an inner (Fe, Cr, O, S)-mixed layer. The outer FeS layer grew into the air by the outward diffusion of $Fe^{2+}$ ions, whereas the inner mixed layer grew by the inward diffusion of oxygen and sulfur ions. At the interface of the outer and inner scales, voids developed and cracking occurred. The Fe-(18.5, 28.3, 36.9)% Cr alloys displayed much better corrosion resistance than the Fe-8.5Cr alloy, because thin $Cr_2O_3$ or $Cr_2S_3$ scales formed.

• Journal of Environmental Science International
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• v.29 no.7
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• pp.739-748
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• 2020

The characteristics of heavy metal ion (Ni²⁺, Zn²⁺, and Cr³⁺) adsorption by zeolite synthesized from Jeju scoria using the fusion and hydrothermal method, were studied. The synthetic zeolite was identified as a Na-A zeolite by X-ray diffraction analysis and scanning electron microscopy images. The equilibrium of heavy metal ion adsorption by synthetic zeolite was reached within 60 min for Ni²⁺ and Zn²⁺, and 90 min for Cr³⁺. The uptake of heavy metal ions increased with increasing pH in the range of pH 3-6 and the uptake decreased in the order of Cr³⁺ > Zn²⁺ > Ni²⁺. For initial heavy metal concentrations of 20-250 mg/L at nonadjusted pH, the adsoption of heavy metal ions was well described by the pseudo second-order kinetic model and was well fitted by the Langmuir isotherm model. The maximum uptake of heavy metal ions obtained from the Langmuir model, decreased in the order of Zn²⁺ > Ni²⁺ > Cr³⁺, differing from the effect of pH on the uptake, which was mainly based on the different pH of the solutions.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.6
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• pp.1021-1026
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• 2000

The removal of cadmium, copper and chromium ions was carried in a phase transfer reactor using W/O(water in oil) microemulsion containing sodium di[2-ethylhexyl] sulfosuccinate(AOT) and isooctane system. Removal efficiencies and mass transfer rate of $Cd^{2+}$, $Cu^{2+}$ and $Cr^{3+}$ were increasing with increasing pH of aqueous solution. However, $Cr^{6+}$ was not extracted by W/O microemulsion with AOT/isooctane system. It was found that removal of heavy metal ions were required an attractive electrostatic interaction between the metal ions and W/O microemulsion. The relationship between mass transfer rate. Jo of $Cd^{2+}$, $Cu^{2+}$ and $Cr^{3+}$ and pH of aqueous solution by W/O microemulsion suggested.

• Journal of the Korean Chemical Society
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• v.31 no.5
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• pp.375-381
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• 1987

Rates for the aquation of trans-[Cr(tn)$_2Cl_2]^+$ and trans-[Cr(en)(tn)Cl$_2$]^+$ ions in aqueous acidic solution have been measured by spectrophotometric method at various temperatures and pressures. Activation volumes are negative and lie in the limited range -1.7 ∼ -2.9cm$^3$mol$^{-1}$ or the complex ions. Activation entropies and activation compressibility coefficients are small negative values. From the results of thermodynamic parameters, it can be inferred that the aquation of the complex ions proceed through an associative interchange(Ia) mechanism. Furthermore, the information on possible transition state structure and reaction paths can be obtained by considering total stabilization energy of the hypothetical intermediates within the framework of angular overlap model. It is found that the theoretically predicted mechanism is consistent with the experimentally observed results.

• Membrane and Water Treatment
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• v.13 no.5
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• pp.209-217
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• 2022

In the present research, Ficus religiosa Bark (FRB) is used as an adsorbent for the removal of heavy metal Cr (VI) ions. This Ficus religiosa Bark was characterized by Scanning Electron Microscope, Fourier transform infrared Spectroscopy, Thermo Gravimetric Analyzer and the results showed that activated adsorbent have high adsorption capacity and withstand even in high temperature. Batch and Continuous experiments were conducted to determine the effect of various parameters such as pH, contact time, adsorbent dose and initial metal concentration. The biosorption followed pseudo first order kinetic model. The adsorption isotherms of Cr (VI) on Ficus religiosa fitted well with the Temkin model. In Batch study, maximum biosorption capacity of Cr (VI) was found to be 37.97 mg g^-1 (at optimal pH of 2, adsorbent dosage of 0.3 grams and concentration of Cr (VI) is100 mg L^-1). The Continuous mode of study shows that 97% of Cr (VI) ion removal at a flow rate of 15 ml min^-1. From the results, selected Ficus religiosa Bark has the higher adsorption capacity for the removal of Cr (VI) ions from wastewater.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.53-54
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• 2013

Nano-multilayered CrAlSiN films consisting of crystalline CrN nanolayers and amorphous AlSiN nanolayers were deposited by cathodic arc plasma deposition. Their oxidation characteristics were studied between 600 and $1000^{\circ}C$ for up to 70 h in air. During their oxidation, the amorphous AlSiN nanolayers crystallized. The formed oxides consisted primarily of $Cr_2O_3$, ${\alpha}-Al_2O_3$, $SiO_2$. The outer $Al_2O_3$ layer formed by outward diffusion of Al ions. Simultaneously, an inner ($Al_2O_3$, $Cr_2O_3$)-mixed layer formed by the inward diffusion of oxygen ions. $SiO_2$ was present mainly in the lower part of the oxide layer due to its immobility. The CrAlSiN films displayed good oxidation resistance, owing to the formation of oxide crystallites of $Cr_2O_3$, ${\alpha}-Al_2O_3$, and amorphous $SiO_2$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.6
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• pp.88-94
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• 2013

The hexavalent chromium (Cr(VI)) is well known as a hazardous ion, presumably inducing dermatic diseases and if serious cancer. The present study concerns the binding capacity of Cr(VI) ions in the cement powder and matrix for a quantitative technique of Cr(VI) ions in cement to influence human health. Both the water-soluble and acid-soluble Cr(VI) ions present in 3 types of ordinary Portland cement (OPC), pulverised fuel ash (PFA), ground granulated blast furnace slag (GGBS), and silica fume (SF) were measured using the spectrophotometer. As a result, it was found that the concentration of water-soluble Cr(VI) ion in cement ranged from 10.5 to 18.9mg/kg-cement, and in the additional materials a very low value of Cr(VI) ion was measured. Acid-soluble Cr(VI) ion was even higher than water-soluble Cr(VI) ion, ranging from 172.4 to 318.2mg/kg-cement. Nevertheless, the concentration of acid-soluble Cr(VI) ion is not proportional to addition of acid. It depends rather the variable pH of solvent involving cement paste. As enough cement hydration occurs, the binding capacity of Cr(VI) ion increases, inhibiting this ions from leaching out in the presence of hydration products such as ettringite or tri-calcium aluminate which bind Cr(VI) ion by ion-exchange.

• Bulletin of the Korean Chemical Society
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• v.26 no.12
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• pp.1937-1940
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• 2005

A lab-made chemiluminescence system with air pump was developed for monitoring of some metal levels in rain. The air pump enabled injection of 17.7 $\mu$g samples into a glass cell filled with luminol-$H_2O_2$ reagent of typically 300 $\mu$L for chemiluminescence measurement. The monitored trend of total metal ions in the rain collected in our campus was compared with analytical results of each metal ion from GFAAS. The system was also demonstrated to determine $Cr^{6+}$ by reduction to $Cr^{3+}$ using $SnCl_2$. The limit of detection for $Cr^{6+}$ obtained by 4 measurements was 85.0 pg $mL^{-1}$ with a relative standard deviation of 3.4%. Although this system doesn’t have selectivity due to the characteristics of chemiluminescence, application of it to environmental monitoring as a sensor for some transition metal ions was demonstrated.

• Journal of Environmental Science International
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• v.9 no.4
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• pp.325-330
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• 2000

The hydroxyapatite (HAp) for the present study was prepared by precipitation method in semiconductor fabrication and the crystallized at ambient to 95$0^{\circ}C$ for 30min in electric furnace. The ion-exchange characteristics of HAp for various heavy metal ions such as $Cd^{2+}, Cu^{2+}, Mn^{2+}, Zn^{2+}, Fe^{2+}, Pb^{2+}, Al^{3+}, and Cr^{6+}$ in aqueous solution has been investigated. The removal ratio of various metal ions for HAp were investigated with regard to reaction time, concentration of standard solution, amount of HAp and pH of solution. The order of the ions exchanged amount was as follws: $Pb^{2+}, Fe^{3+}>Cu^{2+}>Zn^{2+}>Al^{3+}>Cd^{2+}>Mn^{2+}>Cr^{6+}. The Pb^{2+}$ ion was readily removed by the Hap, even in the strongly acidic region. The maximum amount of the ion-exchange equilibrium for $Pb^{2+}$ ion was about 45 mg/gram of HAp. The HAp would seem to be possible agent for the removal of heavy metal ions in waste water by recycling of waste sludge in semiconductor fabrication.