• Resources Recycling
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• v.14 no.1
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• pp.17-25
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• 2005

In order to recover valuable metals from the waste electronic scrap, bioleaching of Cu, Zn, Al, Co, Ni, Sn and Pb was carried out using Thiobacillus ferrooxidans as a leaching microorganism in a shaking flask. In a preliminary study, to obtain the data on the leaching of Cu, Zn, Al, Co and Ni, the metal leaching was accomplished using metal powers instead of electronic scrap. The leaching percentaga of Cu, Zn, Co, Al and Ni powers was reduced with the increase of metal power concentration in solution. Below the metal concentration of 0.5 g/L, more than 85% of Cu, Co and Zn powers was leached out. At the electronic scrap concentration of 100 g/L, Thiobacillus ferrooxidans were able to leach more than 90% of the available Cu and Co while Al, Zn and Ni were able to leach less than 40%. Pb and Sn were not detected in the leachate. Pb was precipitated as PbSO$_4$, whereas Sn precipitated probably as SnO.

• Journal of Korean Vacuum Science & Technology
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• v.4 no.3
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• pp.81-85
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• 2000

The effects of $NH_3$ flow rate and reactor pressure on Al composition and the interface of AlGaN/GaN heterostructure were studied. Equilibrium partial pressure of Ga and Al over AiGaN alloy was calculated as a function of growth pressure, $NH_3$flow rate and temperature. It was found equilbrium vapor pressure of Al is significantly lower than that of Ga, thus, the alloy composition mainly controlled by Ga partial pressure. We believe that more decomposition of Ga occur at lower $NH_3$ flow rate and higher growth pressure leads to preferred Al incorporation into AlGaN. The alloy composition gradient became larger at AlGaN/GaN heterointerface at higher reactor pressures, higher Al composition and low $NH_3$ flow rate. This composition gradient lowered sheet carrier concentration and electron mobility as well. We obtained an AlGaN/GaN heterostructure with sheet carrier density of ${\sim}2{\times}10^{13}cm^{-2}$ and mobility of 1250 and 5000 $cm^2$/Vs at 300 K and 100 K, respectively.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.349-355
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• 2018

$BaMnAl_{11}O_{19}$ was prepared by urea-induced homogeneous precipitation and characterized by X-ray diffraction and scanning electron microscopy. At increased precipitant concentrations, AlOOH replaced $Al(OH)_3$ as an Al precursor. $BaMnAl_{11}O_{19}$ exhibited enhanced catalytic combustion performance and inhibited CO generation. Catalytic performance was also enhanced by the presence of $BaAl_2O_4$ and $BaMnAl_{11}O_{19}$. Compared to $BaAl_2O_4$, $BaMnAl_{11}O_{19}$ exhibited superior catalytic combustion activity.

• Analytical Science and Technology
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• v.13 no.5
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• pp.601-607
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• 2000

Lanthanum has been used as one of the burnup monitor in spent nuclear fuel. $U_3Si/Al$ spent nuclear fuel contains small amount of La in high concentration of U and Al. Therefore, chemical separation of La is required to remove matrix elements. At first, ion chromatography (IC) and inductively coupled plasma systems were installed in radiation shielded glove box to handle the radioactive samples. Retention behavior of uranium, aluminum, lanthanum and some interesting fission products (Sr, Zr, Y, Mo, Ru, Pd, Rh, Cs, Ba, Ce, Pr, Nd, Sm, Eu and Cd) was investigated using the CG10 column and ${\alpha}$-HiBA eluent. As all elements were eluted earlier than lanthanum in 0.2 M ${\alpha}$-HiBA eluent, a portion of U and Al was directly passed to waste using a three way valve between the column and the nebulizer. Thus it was possible to determine the lanthanum in a high concentration of U and Al matrix. Retention time of La was about 12 minutes in this separation condition. Optimum range for the determination of La in $U_3Si/Al$ spent nuclear fuel was $1-10{\mu}g/L$ (ppb) with this system and detection limit was $0.25{\mu}g/L$ in case of $200{\mu}L$ of sample volume.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.2
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• pp.127-137
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• 2019

Zr electrorefining is demonstrated herein using Zirlo tubes in a chloride-fluoride mixed molten salt in the presence of $AlF_3$. Cyclic voltammetry reveals a monotonic shift in the onset of metal reduction kinetics towards positive potential and an increase in intensity of the additional peaks associated with Zr-Al alloy formation with increasing $AlF_3$ concentration. Unlike the galvanostatic deposition mode, a radial plate-type Zr growth is evident at the top surface of the salt during Zr electrorefining at a constant potential of -1.2 V. The diameter of the plate-type Zr deposit gradually increases with increasing $AlF_3$ concentration. Scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX) and X-ray photoelectron spectroscopy (XPS) analyses for the plate-type Zr deposit show that trace amount of Al is incorporated as Zr-Al alloys with different chemical compositions between the top and bottom surface of the deposit. Addition of $AlF_3$ is effective in lowering the residual salt content in the deposit and in improving the current efficiency for Zr recovery.

• Korean Journal of Soil Science and Fertilizer
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• v.50 no.2
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• pp.115-126
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• 2017

There is an increasing concern over arsenic (As) contamination in rice. This study was conducted to develope a prediction model for As uptake by rice based on the physico-chemical properties of soil. Soil and brown rice samples were collected from 46 sites in paddy fields near three different areas of closed mines and industrial complexes. Total As concentration, soil pH, Al oxide, available phosphorus (avail-P), organic matter (OM) content, and clay content in the soil samples were determined. Also, 1.0 N HCl, 1.0 M $NH_4NO_3$, 0.01 M $Ca(NO_3)_2$, and Mehlich 3 extractable-As in the soils were measured as phytoavailable As concentration in soil. Total As concentration in brown rice samples was also determined. Relationships among As concentrations in brown rice, total As concentrations in soils, and selected soil properties were as follows: As concentration in brown rice was negatively correlated with soil pH value, where as it was positively correlated with Al oxide concentration, avail-P concentration, and OM content in soil. In addition, the concentration of As in brown rice was statistically correlated only with 1.0 N HCl-extractable As in soil. Also, using multiple stepwise regression analysis, a modelling equation was created to predict As concentration in brown rice as affected by selected soil properties including soil As concentration. Prediction of As uptake by rice was delineated by the model [As in brown rice = 0.352 + $0.00109^*$ HCl extractable As in soil + $0.00002^*$ Al oxide + $0.0097^*$ OM + $0.00061^*$ avail-P - $0.0332^*$ soil pH] ($R=0.714^{***}$). The concentrations of As in brown rice estimated by the modelling equation were statistically acceptable because normalized mean error (NME) and normalized root mean square error (NRMSE) values were -0.055 and 0.2229, respectively, when compared with measured As concentration in the plant.

• Journal of environmental and Sanitary engineering
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• v.15 no.1
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• pp.95-101
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• 2000

This study was investigated to the reaction of alumina sintering with alkaline. The soluble $NaAlO_2$ was made after the commercial ${\alpha}-Al_2O_3$ was calcinated with NaOH. The reaction of alumina was carried out to be based on the effects of calcination temperature, time, and the mixing ratio of ${\alpha}-Al_2O_3/NaOH$. The alumina was calcined over $500^{\circ}C$ with NaOH powder after it was sieved with 170/270 mesh. The calcined alumina with NaOH powder was dissolved into $25^{\circ}C$ distilled water and filtrated, and HCI was added to adapt pH 6.5~7.5. The residue was separated with vacuum pump for filtration after it was adapted to proper pH, and aluminum compound was precipitated with $Al(OH)_3$. The investigation was carried out with the variables; the calcination temperature($500-900^{\circ}C$), the calcination time (30~90 min), and the concentration of HCI when leaching(0.5~3.0N) respectively. In this investigation, the main product of ${\alpha}-Al_2O_3$ and NaOH was $NaAlO_2$ and the maximum conversion ratio was 91.4% under the optimum conditions as followed ; the ratio of NaOH/${\alpha}-Al_2O_3$ was 1.5 and the calcination conditions were $800^{\circ}C$ and 90 min.

• Environmental Engineering Research
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• v.16 no.3
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• pp.149-157
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• 2011

Nanofiltration (NF) experiments were conducted to investigate fouling of Al-hydroxide precipitate and the influence of organic compound, inorganic compound, and their combination, i.e., multiple foulants. $CaCl_2$ and $MgSO_4$ were employed as surrogates of inorganic compounds while humic acid was used as surrogate of organic compound. The flux attained from NF experiments was fitted with the mathematical fouling model to evaluate the potential fouling mechanisms. Al-hydroxide fouling with a cake formation mechanism had little effect on the NF membrane fouling regardless of the Al concentration. The NF fouling by Al-hydroxide precipitate was deteriorated in presence of inorganic matter. The effect of Mg was more critical in increasing the fouling than Ca. This is because the Mg ions enhanced the resistances of the cake layer accumulated by the Al-hydroxide precipitate on the membrane surfaces. However, the fouling with Mg was dramatically mitigated by adding humic acid. It is interesting to observe that the removal of the conductivity was enhanced to 61.2% in presence of Mg and humic acid from 30.9% with Al-hydroxide alone. The influence of dissolved matter (i.e., colloids) was more negative than particulate matter on the NF fouling for Al-hydroxide precipitate in presence of inorganic and organic matter.

• Journal of the Korean institute of surface engineering
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• v.52 no.3
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• pp.117-122
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• 2019

In this study, surface porosity and corrosion resistance of PEO coatings prepared on the 6061 Al alloy were investigated in terms of sodium phosphate ($Na_3PO_4$) concentrations in an alkaline solution and $NaAlO_2$ sealing. The surface morphologies of the PEO coatings clearly show that the coatings film formed in $9g\;L^{-1}$ had the lowest porosity. The $NaAlO_2$ sealing was found to remove micropores and cracks existing on the surface of PEO coatings. As a result, the $NaAlO_2$ sealing resulted in the movement of corrosion potential toward more positive value and lower corrosion current density.

• Korean Journal of Materials Research
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• v.9 no.9
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• pp.878-882
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• 1999

Structural properties of $Al_xGa_1-_xN$ epilayers grown on (0001) sapphire substrate by plasma induced molecular beam epitaxy are investigated in the range of AlN molar fraction from 0.16 to 0.76. The AlN molar fraction estimated by X-ray diffraction agrees well with that of Rutherford backscattering spectroscopy, showing a good linear relationship. The uniform Auger electron microscopy depth profile and linear dependence of average atomic concentration of all the constituents of AlGaN epilayers on AlN molar fraction imply that the epitaxial growth of $Al_xGa_1-_xN$ layers with variation of AlN molar fraction is well controlled without the compositional fluctuation in depth of the epilayer. It is observed by atomic force microscopy that the surface grain shape of $Al_xGa_1-_xN$ epilayer changes from roundish to coalesced one with increasing AlN molar fraction.