• Resources Recycling
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• v.17 no.5
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• pp.3-10
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• 2008

We researched recycle of mixed waste acids including HF, $CH_{3}COOH$, $HNO_3$ produced during semiconductor wafer process. At first, we recovered HF in form of $Na_{2}SiF_6$ by precipitation using $NaNO_3$ and $Na_{2}SiO_3$. Concentration of HF was made down from 110 g/L, initial concectration, to 0.5 g/L and Recovery rate of HF was 99.5%. After recovery of HF, concentration of $HNO_3$ and $CH_{3}COOH$ is 498 g/L, 265 g/L respectively. From that mixed acid, we recovered $CH_{3}COOH$ using 2 stages of fractional distillation. In first stage, $CH_{3}COOH$ was distilled for separation from $HNO_3$. And in second stage, we recoverd refined $CH_{3}COOH$ by using fractional distillation for removing a little amount of $HNO_3$ in $CH_{3}COOH$ vapor. The concentration of recovered $CH_{3}COOH$ in second stage is 20% and finally recovery rate of $CH_{3}COOH$ is about 87.5%.

• Journal of Wetlands Research
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• v.10 no.2
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• pp.1-14
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• 2008

This study was to describe the ecological survey of wetland plants from Sinbul Mt. and suggest the ways of the sustainable ecological management and wise use. We found 167 plant species. Molinia japonica HACK was the most dominant species and Asarum maculatum NAKAI, Drosera rotundifolia L. and Utricularia racemosa WALL were considered as the most important species. Thus, it was concluded that this area need strong conservation due to the necessity for species diversity. Such several management schemes as the designation for national wetland conservation area, continuous monitoring, cautious surveillance and wise management were suggested to implement successful conservation.

• Clean Technology
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• v.11 no.1
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• pp.21-28
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• 2005

Nitric acid free pickling solution was applied to solve the severe environmental problems attributed to nitric acid during pickling process of stainless steel product. In points of pickling capability and erosion of stainless steel base metal, a solution contains I% of hydrochloric acid and 2% of hydrofluoric acid and hydrogen peroxide was revealed as the best alternative to conventional mixed acid of nitric acid and hydrofluoric acid. To keep the pickling capability, it was necessary to maintain the concentration ratio of hydrogen peroxide to hydrochloric acid above 0.5.

• Applied Chemistry for Engineering
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• v.2 no.1
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• pp.77-85
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• 1991

A series of samples having different $SiO_2/Al_2O_3$ ratio were prepared by treating hydrogen mordenites with boiling hydrochloric acid and with hydrofluoric acid. The acidities of these samples were measured by TPD of $NH_3$ and by pyridine adsorption using IR, and the catalytic activities and selectivities of isomerization were measured for the reaction of ortho-xylene. For the samples treated by boiling hydrochloric acid, the acidities decreased with the increasing $SiO_2/Al_2O_3$ ratio caused by the extraction of framework aluminum. The sample having the $SiO_2/Al_2O_3$ ratio or 22 showed better activity than the others. For the samples treated by hydrofluoric acid, the content of chemically binding fluorine increased with the increasing contact time of hydrofluoric acid solution. The catalytic activities decreased with the hydrofluoric acid treatment due to the decreased acid sites resulted from the extraction of aluminum and silicon as well as the hydroxyl group replacement by the fluoride ion. The slightly increasing catalytic activities, however, came from the newly created acid sites, due to the removal of surface silicon, having enhanced by the inductive effect of binding fluorin with further acid treatment.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.423.1-423.1
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• 2014

본 발표에서는 실리콘 이종접합 태양전지에서 중요한 실리콘 웨이퍼 표면/계면 제어에 대하여 발표한다. 다시 말하여, 실리콘 웨이퍼 기판 세정공정 변화에 따른 실리콘 웨이퍼 표면의 소수전하수명(minority carrier lifetime, MCLT) 및 태양전지 소자특성 변화에 대하여 연구하였다. 구체적으로, 실리콘 웨이퍼 클리닝 최초단계로써 KOH damage etching 공정을 도입할 때, 이후 클리닝 공정을 통일하여 적용한 웨이퍼 표면의 MCLT 및 상기 웨이퍼를 이용하여 플라즈마 화학기상증착법(PECVD)을 통하여 제작한 태양전지 소자 효율은 KOH etching 시간이 10분일 때 최대치에 도달한 후 감소하였다. 또한, RCA1, RCA2, Piranha로 이루어진 웨이퍼 클리닝 단계의 사이에, 또는 맨 마지막에 묽힌 불산용액(DHF, 5 %) 처리를 하여 표면 산화막 제거 및 수소종단처리를 하여 기판의 passivation 특성을 향상시키고자 할 때, 불산용액 처리 순서에 따른 웨이퍼 표면의 MCLT 및 태양전지 소자 효율을 비교하였다. 그 결과, 묽은불산용액을 클리닝 단계 사이에 적용하였을 때의 MCLT 및 태양전지 소자의 특성이 더 우수하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.926-933
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• 2012

Phosphoric acid used for the production of phosphate fertilizers is synthesized by the reaction of phosphate rock and sulfuric acid. As the reaction is exothermic, yield of phosphoric acid is poor at elevated temperature. Therefore, enhancement in its yield requires the process temperature be maintained by releasing the vapor ($80^{\circ}C$) containing HF and SiF4 through a vacuum cooler. However, these valuable resources; Fand Si, which can be utilized for the manufacture of refrigerant and polysilicon, respectively, are being wasted in the treatment process. We performed lab-scale experiments to estimate the amount of recoverable H2SiF6, a by-product of phosphoric acid manufacturing process. The experimental results showed a decrease of fluorine concentration by 0.12wt% in the liquid phase. Preliminary estimation showed a possible recovery of 5,509 ton/yr of fluorine considering the scale of the fertilizer manufacturing plant. Furthermore, field-scale experiment showed that H2SiF6 could be enriched in liquid phase from 0.35wt% to 7.33wt% and the vapor flow-rate from vacuum cooler was estimated at $51,000m^3/hr$. Anew, the efficiency of fluorine recovery in the pilot-scale experiment was found to be 76.74% and the production of H2SiF6 was estimated at 5,340 ton/yr.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.8
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• pp.909-914
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• 2007

Fluorine compounds are the essential chemicals for wet processes of semiconductor and LCD production line. Problems of conventional treatments for fluoride wastewater are their high operation costs and low fluoride removal capacity. In this study, cement paste containing various Ca-bearing hydrates such as portlandite, calcium silicate hydrate(CSH), and ettringite was investigated for fluoride removal. The objectives of this study are to assess the feasibility of using cement paste cured mixture of cement and water as an alternative agent for treatment of fluoride wastewater and to investigate fluoride removal capacity of the cement paste. The performance of cement paste was comparable to that of lime in the kinetic test. In column experiment where the effluent fluoride concentrations were below 0.5 mg/L. Then the leached calcium reached the maximum level of 800 mg/L. The nitrate reduced to the level of less than 10 mg/L. Nitrate in the wastewater was exchanged with interlayer sulfate of these cement hydrate LDHs. Phosphate concentration could be reduced to 10 mg/L by forming calcium phosphate. These results indicate that the cement paste generally has advantageous characteristics as an economical and viable substitute for lime to remove fluoride.

• Analytical Science and Technology
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• v.29 no.5
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• pp.219-224
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• 2016

불산 중 극미량 음이온의 고상추출과 이온크로마토그래프를 이용한 고감도 분석법이 개발되었다. 불산 중 불소이온이 고상에 의해 제거하였고 이어서 음이온 (F⁻, CH₃COO⁻, Cl⁻, Br⁻, NO₃⁻, PO₄³⁻, SO₄²⁻)들이 이온크로마토그래프를 이용하여 연속적으로 분리하였다. 고상 추출법에 영향을 주는 각 인자들 (흡착제의 선택, 시료의 부피 및 pH, 용출 용액과 용출용액의 부피)을 결정하였으며 그 결과 흡착제로서 Oasis WAX 컬럼이 가장 우수하였고 1.0 mL의 시료부피, 용출용액으로 50 mM 초산암모늄염 5 mL가 분리능에서 가장 우수하였다. 개발한 방법에 의한 음이온 (Cl⁻, Br⁻, NO₃⁻, PO₄³⁻, SO₄²⁻)들의 방법검출한계는 25 % 불산용액 (w/w) 중에 0.04~0.30 µg/L의 범위를 보였고 정밀도는 20.0와 40.0 µg/L의 농도에서 5 % 이내를 보였다. 한 제조회사에 의한 25 % 불산 중 음이온의 4.2에서 47.5 µg/L의 범위로 모두 검출되었다. 이 방법은 시험절차가 간단하고, 재현성 및 감도가 좋아서 반도체회사에서 불산 중 음이온 불순물을 정도 관리하는데 매우 유용한 방법이 될 것으로 판단된다.

• 월간산업보건
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• s.304
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• pp.2-4
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• 2013

• Resources Recycling
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• v.2 no.4
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• pp.1-9
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• 1993

A study on the recovery of nitric and hydrofluoric acids is carried out with pulsed column extractor in order to the industrial application of this process. Firstly, from the continuous experiments about the recovery of acids using domestic stainelss steel pickling solution, it is found out that the free nitric and hydrofluoric acids are only extracted by 70% TBP and the heaby metals such as Fe, Cr and Ni are not extracted. The effectiveness of extraction and stripping generally improves as the pulse velocity(product of amplitude and frequency) is increased, optimum performance typically occuring slightly below an amplitude-frequency product which results in flooding the column because of excessive emulsification. When the pickling solution is treated by 70% TBP at a phase ratio of A/O=1/2 in the extraction and by distilled water at a phase ratio of O/A=1 in the stripping, the concentration of refined acides are 102g/$\ulcorner$ $HNO_3$and 8.8g/$\ulcorner$ HF, respectively and the recovery of $HNO_3$and HF are 90.7% and 75.2%, respectively.