• Resources Recycling
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• v.20 no.1
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• pp.61-68
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• 2011

Impurity removal from metallurgical grade silicon by acid washing at $50^{\circ}C$ was investigated by employing sulfuric, nitric acid and the mixture of hydrochloric and hydrofluoric acid. Acid washing treatment had no effect on the removal of boron and the concentration of this clement after treatment was rather increased. In our experimental range, the removal percentage of phosphorus was 60%. In the acid washing with sulfuric and nitric acid, the removal percentage of major impurities was below 50%, which indicates that refining effect was not great with these acids. Acid washing with the mixture of hydrochloric and hydrofluoric acid led to removal percentage of higher than 90%. Data on the purity of silicon after acid washing at various conditions are reported.

• Journal of Radiation Protection and Research
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• v.24 no.2
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• pp.73-86
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• 1999

The ion-exchange method for the purification of primary coolant has been used broadly in PWR(pressurized water reactor)-type nuclear power plants due to its high decontamination efficiency, simple system, and easy operation. However, its non-selective removal of metal and non-radionuclides shortens its life, resulting in the generation of a large amount of waste ion-exchange resin. In this study, the feasibility of electrodeionization (EDI) was investigated for the purification of primary cooling water using synthetic solutions under various experimental conditions as an alternative method for the ion exchange. The results shows that as the feed flow-rate increased, the removal efficiency increased and the power consumption decreased. The removal rate was observed as a 1000 decontamination factor(DF) at a nearly constant level. For the synthetic solution of 3 ppm TDS (Total Dissolved Solid), the power consumption was 40.3 mWh/L at 2.0 L/min of feed flow rate. The higher removal rate of metal species and lower power consumption were obtained with greater resin volume per diluting compartment. However, the flow rate of the EDI process decreased with the elapsed time because of the hydrodynamic resistivity of resin itself and resin fouling by suspended solids. Thus, the ion-exchange resin was replaced by an ion-conducting spacer in order to overcome the drawback. The system equipped with the ion-conducting spacer resolved the problem of the decreasing flow rate but showed a lower efficiency in terms of the power consumption, the removal rate of metal species and current efficiency. In the repeated batch operation, it was found that the removal efficiency of metal species was stably maintained at DF 1000.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2001.05a
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• pp.173-175
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• 2001

흡착에 필요한 최적의 세라믹 볼의 소성온도는 93$0^{\circ}C$가 가장 적당하다. 공업용수 중에 용존되어 있는 유기물 및 유해성분이 제거(COD나 $BOD_{5}$)가 가능하다. Fe와 Pb의 중 금속 제거의 경우 Pb의 경우가 제거 효율이 더 크며, 이에 따른 mechanism으로 이온교환이온이 Pb의 경우 2가 양이온이기에 더욱 효율이 크고 Fe의 경우는 수화하여 구조적인 붕괴를 일으키며, 2가와 3가의 공존하므로 Pb보다 제거율이 낮다. Fe와 Pb 중금속수를 1시간 동안 제거하여 Freundlich형 등온식에 따른 계산 결과 5,10ppm에서 1/n의 수치가 2 이상을 넘지 않고 있고, 500, 1000ppm의 경우는 등온이온교환으로 할 때 1/n의 수치가 2에 근접하므로 분말의 경우에 비해 제거율이 낮지는 않다. 그러므로 경제적 이점과 재활용면에서 볼의 사용이 우수하다는 것을 알 수 있다. 장치의 용기에 비례하여 볼 때 볼의 양은 600g이 가장 적당한 양이다. 등온교환의 경우 Apatite(HAp)를 이용한 분말의 제거율 보다 약간 낮으나 분말의 경우 사용 후 취급이 용이하지 않고 2차적 오염이 예상되므로 세라믹 볼의 경우 환경친화성재료로 여러 가지의 수처라 공정에 적용이 가능할 것으로 판단된다.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.54.2-54.2
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• 2011

야금학적 정련 공정 중 슬래그 처리, 일방향 응고, 플라즈마-전자기유도용해 공정을 적용한 태양전지용 실리콘 제조 기술에 관한 연구를 수행하였다. 원소재인 금속급 실리콘을 제조하기 위해원재료로 규석, 코크스(Cokes), 숯, 그리고 우드칩(Wood chip)을 사용하였으며, 150kW급 DC 아크로(Arc furnace)를 이용하여 순도 99.8% 금속급 실리콘을 제조하였다. 제조된 용융 상태의 금속급 실리콘은 슬래그와 반응시켜 불순물을 제거하였다. SiO2-CaO-CaF2 계의 슬래그를 이용하였으며, 금속급 실리콘과 슬래그의 질량비 및 반응 시간에 따른 실리콘 불순물 특성을 평가하였다. 이후 고액 계면이 제어 가능한 일방향 응고 장치를 이용하여 금속불순물을 제거하였다. 고액상태의 온도 조건 및 응고 시간에 따른 불순물 농도 변화를 평가하였으며, 순도 6N급의 실리콘을 제조하였다. 마지막 공정으로 스팀 플라즈마 토치와 냉도가니가 적용된 전자기 유도 용해장치를 이용하여 붕소와 인을 제거하였다. 플라즈마 토치 가스로는 아르곤, 스팀, 수소를 이용하였다. 붕소와 인의 제거율은 각각 94%와 96%를 달성하였으며, 최종 순도 6N급의 실리콘을 제조하였다.

• Journal of Wetlands Research
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• v.12 no.1
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• pp.23-31
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• 2010

Chlorinated aliphatic hydrocarbons (CAHs) such as tetrachloroethylene (PCE), 1,1,1-trichloroethane (1,1,1-TCA) are the contaminants most frequently found in soil and groundwater. They have a potential to be toxic to and persistent in environment. This study is focused on selection of zero-valent metal and ores for the removal of high concentration PCE or 1,1,1-TCA and mixture of two compound. For the screening of suitable metals, we measured dechlorination rate, removal capacities and economics by using batch reactor test. This results suggest that removal rate and dechlorination of high quality iron and zinc are higher than slag and nature ores like zinc and manganese. Among nature ores, zinc ores(64% purity) have highest removal capacities. And in economics zinc ores is 10 times better than high quality metal tested. We conclude zinc ore is most suitable metal for the removal of PCE or 1,1,1-TCA.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.423-429
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• 2008

Currently, Ash-free clean coal producing process by solvent extraction is under development. The produced ash-free clean coal can be directly combusted in a gas turbine which results in substantial improvement of power generation efficiency. However, the clean coal produced by the solvent extraction still contain trace amount of alkali metal which may cause corrosion on turbine blades during the direct combustion. In present work ${\alpha},{\beta}$-metal (Zr and Ti) phosphates and H-Y zeolite were synthesized and their ion exchange characterizations were investigated for the application on alkali metal removal for clean coal production. $Na^+$ ion removal capacities of the metal phosphates and H-Y zeolite were measured and compared in both aqueous solution (100 ppmw, $Na^+$) and coal dissolved N-methyl-2-pyrrolidone (NMP, 12 ppmw $Na^+$) at elevated temperature. In aqueous solution, the ${\beta}$ form metal phosphates showed very high ion exchange capacities compared to ${\alpha}$ form. ${\beta}$ form metal phosphates also showed higher $Na^+$ removal capacities than H-Y zeolite. In ion exchange medium of NMP, all the ${\alpha}$ form metal phosphates showed over 90% of $Na^+$ ion removal efficiency in the temperature range of 200 to 400 while that of H-Y zeolite decreased as a half when the temperature was over 350. In addition, the regenerated metal phosphates by acid treatment showed no sign of degradation in $Na^+$ removal efficiency. Among the metal phosphates used, $Zr_{0.75}Ti_{0.25}(HPO_4)_2$ showed the best performance in $Na^+$ removal and is expected to be the most suitable inorganic ion exchanger for the alkali metal removal process.

• Applied Chemistry for Engineering
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• v.7 no.1
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• pp.109-117
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• 1996

Removal of metal ions on the ultrafiltration membrane with micellar-enhanced with anion surfactants is a recently developed technique which can remove heavy metals and small molecular weight ions from wastewater with simple separation process and without a phase change. Above a certain concentration, so called the critical micelle con binding cationic cobalt ions and anionic surfactants, were removed by ultrafiltration membrane. The transmembrane pressure difference had a relatively small effect on the rejection coefficient of metal ions on the ultrafiltration membrane whereas the level of anionic surfactant-to-metal ratio (S/M) had a substantial effect.

• Journal of the Mineralogical Society of Korea
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• v.27 no.4
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• pp.207-222
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• 2014

In order to recover the metallic copper powder from the mine-waste rock, heap bioleaching, Fe removal and electrowinning experiments were carried out. The results of heap leaching with the mine-waste rock sample containing 0.034% Cu showed that, the leaching rate of Cu were 61% and 62% in the bacteria leaching and sulfuric acid leaching solution, respectively. Sodium hydroxide (NaOH), hydrogen peroxide ($H_2O_2$) and calcium hydroxide ($Ca(OH)_2$) were applied to effectively remov Fe from the heap leaching solution, and then $H_2O_2$ was selected for the most effective removing Fe agent. In order to prepare the electrolytic solution, $H_2O_2$ were again treated in the heap leaching, and Fe removal rates were 99% and 60%, whereas Cu removal rates were 5% and 7% in the bacteria and sulfuric acid leaching solutions, respectively. After electrowinning was examined in these leaching solution, the recovery rates of Cu were obtained 98% in bacteria and obtained 76% in the sulfuric leaching solution. The dendritic form of metallic copper powder was recovered in both leaching solutions.

• Applied Chemistry for Engineering
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• v.5 no.6
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• pp.925-934
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• 1994

Nickel recovered from the spent oil-hydrogenation catalysts was used in hydrogenation catalyst preparation. The spent catalyst contains approximately 21.8% Ni, 0.7% Mg, and small quantities of Al, Fe, and Zn. Nickel recovery was obtained by inorganic acid digestion in the order of HCI>$NHO_3$>$H_2SO_4$. For $HNO_3$, 3hour extraction with 3N solution was satisfactory. In the PH range of 6.5~9.0, Ni recovery was higher, but metallic impurities were found to be coprecipitated. The PH in the range of 7.0~9.0 seems to be the optimum condition for separation to obtain acceptable Ni precipitates without the decrease of purity. The catalysts prepared with reclaimed nickel by wet reduction methods showed catalytic activities close to those prepared using reagent nickel in the oil hydrogenation reaction. The surface areas of the support do not seem to affect the catalytic activity.

• Resources Recycling
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• v.4 no.1
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• pp.46-51
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• 1995

After removal of mercury in the silver oxide batteries with the distillation process, the leaching of valuable metals from the residue was studied. The distilled residue was reacted with the various HNO, concentration, reactlon temperature, readion time and pulp density. It was found that the optimum condition for leachmg was 2N HNO,, 40-60% reaction temperature, 6 hours reaction tlme and 10g/200ml pulp density. More than 99% of silver and zinc were dissolved in this process while less than 50% of iron and nickel were leached