• 한국지하수토양환경학회지:지하수토양환경
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• 제20권5호
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• pp.1-10
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• 2015

FeS, as a natural reduced iron mineral, has been recognized to be a viable reactive material for As(III) sequestration in natural and engineered systems. In this study, FeS-coated sand packed columns were tested to evaluate the As(III) removal capacities under anaerobic conditions at pH 5, 7 and 9. The column obtained As(III) removal capacity was then compared with the capacity result obtained from batch reactors. In the comparison, two different approaches were used. The first approach was used the total As(III) removal capacity which method was proved to be useful for interpreting pH 5 system. The second approach was used to consider sorption non-linearity and proved to be useful for interpreting the pH 9. The results demonstrated that a mechanistic understanding of the different removal processes at different pH conditions is important to interpret the column experimental results. At pH 5, where the precipitation of arsenic sulfide plays the major role in the removal of arsenic, the column shows a greater removal efficiency than the batch system due to the continuous dissolution of sulfide and precipitation of arsenic sulfide. At pH 9, where adsorption mainly governs the arsenic removal, the sorption nonlinearity should be considered in the estimation of the column capacity. This study highlighted the importance of understanding reaction mechanism to predict column performance using batch-obtained experimental results.

• 대한치과교정학회지
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• 제46권6호
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• pp.386-394
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• 2016

Objective: The objective of the study was to evaluate the practicality and the validity of different surface treatments of self-drilling orthodontic mini-implants (OMIs) by comparing bone cutting capacity and osseointegration. Methods: Self-drilling OMIs were surface-treated in three ways: Acid etched (Etched), resorbable blasting media (RBM), partially resorbabla balsting media (Hybrid). We compared the bone cutting capacity by measuring insertion depths into artificial bone (polyurethane foam). To compare osseointegration, OMIs were placed in the tibia of 25 rabbits and the removal torque value was measured at 1, 2, 4, and 8 weeks after placement. The specimens were analyzed by optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Results: The bone cutting capacity of the etched and hybrid group was lower than the machined (control) group, and was most inhibited in the RBM group (p < 0.05). At 4 weeks, the removal torque in the machined group was significantly decreased (p < 0.05), but was increased in the etched group (p < 0.05). In the hybrid group, the removal torque significantly increased at 2 weeks, and was the highest among all measured values at 8 weeks (p < 0.05). The infiltration of bone-like tissue surface was evaluated by SEM, and calcium and phosphorus were detected via EDS only in the hybrid group. Conclusions: Partial RBM surface treatment (hybrid type in this study) produced the most stable self-drilling OMIs, without a corresponding reduction in bone cutting capacity.

• 한국환경과학회지
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• 제11권3호
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• pp.263-269
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• 2002

This study was conducted to know the removal characteristics of ammonia nitrogen by commercially available cation exchange resins. Eight acidic cation exchange resins were investigated in batch reactors. Among them, the most effective resin for ammonia removal in solution was PK228, which was a strong acidic resin of $Na^{+}$ type. PK228 was compared with activated carbon and natural zeolite. The effects of cation exchange capacity, ammonia concentration, resin amount, temperature and pH on ammonia removal by PK228 were investigated in batch reactor, and the effect of effluent velocity in continuous column reactor. Strong acidic resins of porous type were more effective than week acidic resins or gel type resins for ammonia removal in solution. PK228 was more effective than activated carbon and natural zeolite for ammonia removal in batch reactor. With increasing initial ammonia concentration, the amount of ammonia removed by PK228 increased, but the proportion of removed ammonia to initial ammonia concentration decreased. The effect or temperature on ammonia removal by PK228 was very slight. The ammonia removal to acidic solution was more effective than that at basic solution. With decreasing effluent velocity of solution through column, breakthrough point extended, and ammonia removal capacity increased.d.

• 한국환경과학회지
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• 제24권1호
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• pp.1-7
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• 2015

The solid-phase extractant PS-D2EHPA/TBP was prepared by immobilizing two extractants D2EHPA and TBP in polysulfone (PS). The prepared PS-D2EHPA/TBP was characterized by using fourier transform infrared spectrometer (FTIR) and scanning electron microscopy (SEM). The removal of Cu(II) from aqueous solution was investigated in batch system. The experiment data were obeyed the pseudo-second-order kinetic model. Equilibrium data were well fitted by Langmuir model and the removal capacity of Cu(II) by solid extractant PS-D2EHPA/TBP obtained from Langmuir model was 3.11 mg/g at 288 K. The removal capacity of Cu(II) was increased according to increasing pH from 2 to 6, but the removal capacity was decreased below pH 3 remarkably.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권7호
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• pp.43-52
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• 2015

The uranium removal capacity of radish sprouts (Raphanus sativus L.) in groundwater was calculated on the basis of the amount of uranium accumulated in the radish sprouts rather than the concentration in solution, of which process was very limited in previous studies. Continuous rhizofiltration clean-up system was designed to investigate the feasibility of radish sprouts, applying for uranium contaminated groundwater (U concentration: 110 μg/L) taken at Bugogdong, Busan. Six acrylic boxes (10 cm × 30 cm × 10 cm) were connected in a direct series for the continuous rhizofiltration system and 200 g of radish sprouts cultivars was placed in each box. The groundwater was flushed through the system for 48 hours at the constant rate of 5 mL/min. The rhizofiltration system was operated in the phytotron, of which conditions were at 25℃ temperature, 70% of relative humidity, 4,000 Lux illumination (16 hours/day) and 600 mg/L of CO₂ concentration. While 14.4 L of contaminated groundwater was treated, the uranium removal efficiency of the radish sprouts (1,200 g in wet weight) was 77.2% and their removal capacities ranged at 152.1 μg/g-239.7 μg/g (the average: 210.8 μg/g), suggesting that the radish sprouts belong to the group of hyper-accumulation species. After the experiment, the sum of U amounts accumulated in radish sprouts and remained in groundwater was 1,472.2 μg and the uranium recovery ratio of this rhizofiltration experiment was 92.9%. From the results, it was investigated that the radish sprouts can remove large amounts of uranium from contaminated groundwater in a short time (few days) because the fast growth rate and the high U accumulation adsorption capacity.

• 에너지공학
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• 제10권4호
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• pp.342-348
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• 2001

A new design concept for a decay heat removal system in a liquid metal reactor is proposed. The new design utilizes a thermosyphon to enhance the heat removal capacity and its heat transfer characteristics are analyzed against the current PSDRS (Passive Safety Decay heat Removal System) in the KAL IMER (Korea Advanced LIquid MEtal Reactor) design. The preliminary analysis results show that the new design with a thermosyphon yields substantial increase of 20∼40% in the decay heat removal capacity compared to the current design that do not have the thermosyphon. The new design reduces the temperature rise in the cooling air of the system and helps the surrounding structure in maintaining its mechanical integrity for long term operation at an accident. Also the analysis revealed the characteristics of the interactions among various heat transfer modes in the new design.

• Advances in environmental research
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• 제4권4호
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• pp.263-271
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• 2015

In this study, the effect of initial nitrate loading on nitrate removal and byproduct selectivity was evaluated in a continuous system. Nitrate removal decreased from 100% to 25% with the increase in nitrate loading from 10 to $300mg/L\;NO_3-N$. Ammonium selectivity decreased and nitrite selectivity increased, while nitrogen selectivity showed a peak shape in the same range of nitrate loading. The nitrate removal was enhanced at low catalyst to nitrate ratios and 100% nitrate removal was achieved at catalyst to nitrate ratio of ${\geq}33mg\;catalyst/mg\;NO_3-N$. Maximum nitrogen selectivity (47%) was observed at $66mg\;catalyst/mg\;NO_3-N$, showing that continuous Cu-Pd-NZVI system has a maximum removal capacity of 37 mg $NO_3{^-}-N/g_{catalyst}/h$. The results from this study emphasize that nitrate reduction in a bimetallic catalytic system could be sensitive to changes in optimized regimes.

• 유기물자원화
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• 제9권3호
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• pp.136-144
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• 2001

악취중 황화수소의 생물학적 제거시스템에서 바이오필터의 미생물 담체로 유기담체인 Peat와 Rock wool을 사용하고 미생물원으로 소화 슬러지를 식종했다. 유입 황화수소 농도를 증가시켜 완전히 제거되는 황화수소의 유입 부하를 완전 제거능, 제거를 보여준 최대의 제거량을 최대 제거능으로 정의하였다. 단위 중량 및 단위 체적 기준으로 비교한 완전 제거능 및 최대 제거능은 Peat보다 Rock wool의 결과가 높았다. 동력학적 반응속도 해석에 의한 황화수소의 최대 제거속도($V_m$) 및 포화정수($K_s$)를 이용한 속도해석 결과는 황화수소의 농도가 증가할수록 Rock wool의 반응속도가 빠르게 진전되었다.

• 한국대기환경학회지
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• 제15권5호
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• pp.649-655
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• 1999

Biofiltration of polluted gas streams contained $H_2S$ was studied. The experiments were performed in a laboratory-scale reactor with a porous ceramic media inoculated with sulfur oxidizing bacterium, TAS which was isolated from activiated sludge. The concentration of $H_2S$ in the inlet gas varied from 109 to 3,841 ppm, at the various space velocities(SV) of 50 $h^{-1}$ to 250 $h^{-1}$. Various tests have been conducted to evaluate the effects of such parameters as pH, concentration of sulfate ion and retention time on the pressure drop and maximum elimination capacity. The removal efficiency of $H_2S$ decreased as the $H_2S$ concentration or gas velocity increased in the inlet gas. Pressure drop was insignificant in this system. The maximum elimination capacity could reach up to 16.35g-S/kg-dry packing material/day.

• 한국환경보건학회지
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• 제23권1호
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• pp.50-54
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• 1997

The removal efficiency of nutrient was investicated by using Glycine max Meer seedling. After budding, Glycine max Merr was raised at darkness for 4 days. During cultivation, the removal efficiency of $NO_2-N+NO_3-N$ was up to 90% with initial concentration of 20-100 ppm. The removal efficiency of PO$_4$-P was up to 80% with initial concentration at 30 ppm, but it was down to 22% and 27% at 40 ppm and 50 ppm. When the removal efficiency of nutrient was compared with alternating 12 hours' light and darkness, the removal efficiency of NO$_2$-N + NO$_3$-N was up to 90% at below 60 ppm. It was not different from each other. But it was particularly low about 62% and 34% at 80 ppm and 100 ppm in alternating 12 hours' light. The removal efficiency of PO$_4$-P was low at alternating 12 hours' light between 10-50 ppm on the whole range. The neutralizing capacity of pH was shown in acidity and alkalinity except strong acidity(below pH 3). The initial pH was neutralized at 6.0-7.7 of pH after 4 days. Particularly, Glycine max Meer seedling that was difference from other water plants, was shown the neutralizing capacity in strong alkalinity.