• 환경생물
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• 제23권4호
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• pp.374-378
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• 2005

A diffusion - precipitation method was developed to determine acid volatile sulfide (AVS) concentrations in freshwater sediments. This method uses silver nitrate as a sulfide trap solution and the concentration of trapped sulfide is determined gravimetrically. The proposed diffusion - precipitation method is more rapid and less expensive than previously developed purge- and - trap methods. Spiked sodium sulfide recoveries using this method $(97\~120\%)$ were similar with a previously developed diffusion - absorption method $(93.8\~115\%)$ and about $20\%$ greater than a previously developed purge-and-trap method $(74.6\~105\%)$. Detection limit of this method $(0.1\;{\mu}mole\;S\;g^{-l})$ was comparable with that of diffusion-absorption method $(0.06\;{\mu}mole\;S\;g^{-l})$ and purge-and-trap method $(0.05\~0.5\;{\mu}mole\;S\;g^{-l})$.

• Bulletin of the Korean Chemical Society
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• 제25권8호
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• pp.1156-1160
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• 2004

The technique of an on-line preconcentration by the direct sulfide precipitation has been developed. Sn was homogeneously precipitated by sulfide, which was generated in situ from the hydrolysis of thioaceteamide. Precipitate was collected on a filter in the line and dissolved out instantaneously by KOH to be sent to an ICP. The enrichment factor was 4 with the sampling speed of 15/hr for 1.0 mL of sample. It was increased to more than 40 times when the sampling volume was increased to 10 mL with the sampling speed of 5/hr. $Sn^{2+}/Sn^{4+}$ could be separately determined with the on-line precipitation technique. The method was applied to the analysis of NIST SRM 1566 Oyster sample and yielded good agreement with the certified value.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.292-295
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• 2001

A Study on the precipitation characteristics of nickel hydroxide as well as carbonate and sulfide is carried out to determine the proper treatment condition of the wastewater induced from nickel-plating industry. The nickel concentrations in the effluent could be kept lower than 5ppm when the value of pH was maintained higher than 10. The precipitation of nickel salts by alkaline addition to the nickel containing model wastewater was conducted by using proper amount of sodium hydroxide, sodium carbonate, sodium bicarbonate and sodium sulfide. In case of the sulfide treatment, the residual nickel concentration in the clear water after precipitates removed showed the lowest value. The influences of the precipitation condition upon the particle size of the crystals precipitated were also investigated. In spite of the various precipitation conditions were adopted, the particle size of the precipitated crystals showed no great differences. The sedimentation rates of the precipitated particle bed were observed and the free sedimentation period was terminated within 20 minutes. Although the hindered sedimentation as well as bed compaction progressed subsequently, the bed heights were maintained almost the same level after two hours of sedimentation.

• Applied Biological Chemistry
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• 제2권
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• pp.9-14
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• 1961

The formation of sulfide from sulfate has been discussed from the thermodynamic principles. No mechanism of the reaction has been presented. From the stoichiometric and Nernst equations for the conversion of sulfate into sulfide, it was concluded that the formation of sulfide from sulfate can take place more readily if pH of a medium is low. The difficulty of this conversion increases with increasing pH. As pH of a medium increases, the degree of dissociation of H₂S into S= increases and this, in turn, renders the chance of precipitation of sulfide as FeS easier. Higher the pH of a soil or medium, greater is the S= concentration. The concentration of ferrous ion required to remove dissolved sulfide in a medium by forming insoluble FeS decreases with increasing pH. From the theory it was pointed out that an application of lime and iron rich foreign substances to a soil may be effective in causing the removal of dissolved sulfide from solution.

• 한국세라믹학회지
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• 제49권2호
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• pp.155-160
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• 2012

This paper reported a simple deposition-precipitation method, introducing the metal (Ni, Ag and Sn) and $Na_2S{\cdot}5H_2O$ to preparedispersion metal sulfide nanoparticles on the surface of the Multi-walled carbon nanotube for synthesis of CNT-$M_xS_y$ ($NiS_2$, $Ag_2S$, SnS) composite photocatalysts. The characterization of the prepared CNT-$M_xS_y$ ($NiS_2$, $Ag_2S$, SnS) composites was performed by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis and BET analysis. Furthermore, the MB degradation rate constant for CNT-SnS composite was $5.68{\times}10^{-3}$ under visible light irradiation, which was much higher than the corresponding values for other samples. The detailed formation and photocatalytic mechanism are also provided here.

• 방사성폐기물학회지
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• 제21권1호
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• pp.1-8
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• 2023

The major concern in the deep geological disposal of spent nuclear fuels include sulfide-induced corrosion and stress corrosion cracking of copper canisters. Sulfur diffusion into copper canisters may induce copper embrittlement by causing Cu₂S particle formation along grain boundaries; these sulfide particles can act as crack initiation sites and eventually cause embrittlement. To prevent the formation of Cu₂S along grain boundaries and sulfur-induced copper embrittlement, copper alloys are designed in this study. Alloying elements that can act as chemical anchors to suppress sulfur diffusion and the formation of Cu₂S along grain boundaries are investigated based on the understanding of the microscopic mechanism of sulfur diffusion and Cu₂S precipitation along grain boundaries. Copper alloy ingots are experimentally manufactured to validate the alloying elements. Microstructural analysis using scanning electron microscopy with energy dispersive spectroscopy demonstrates that Cu₂S particles are not formed at grain boundaries but randomly distributed within grains in all the vacuum arc-melted Cu alloys (Cu-Si, Cu-Ag, and Cu-Zr). Further studies will be conducted to evaluate the mechanical and corrosion properties of the developed Cu alloys.

• 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.

• 한국토양환경학회지
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• 제3권3호
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• pp.21-31
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• 1998

폐광산 광미로부터 비소를 제거하기 위한 산침출 및 침전실험을 수행하였다. 다덕광산의 광미시료를 대상으로 염산 및 황산농도, 침출시간, 슬러리 농도에 따른 침출율의 변화를 조사함과 동시에 침출액 중의 비소성분을 침전시키기 위하여 pH조절과 Sodium Sulfide를 첨가하여 비소의 침전율을 관찰하였다. 염산침출의 경우 1시간 침출 후 산농도 및 슬러리 농도에 따라 40%에서 86%까지 비소침출율을 보였으며, 황산의 경우 47%∼77%의 침출율을 나타냈다. 침출시간에 따른 침출율의 변화는 10분이내에서 급격한 변화를 보이지만, 그후에는 침출시간이 증가함에 따라 완만한 증가를 보였다. 침출액중의 산농도가 높아지면 침출율이 증가하나 2N이상에서는 그 차이가 크지 않았다. 침출액을 반복사용할 경우 5회까지 꾸준히 침출이 일어나지만 그 증가폭은 점차 감소하였으며, 산농도가 높을수록 감소하는 추세가 보다 완만한 경향을 보였다. 침출액 중의 비소성분은 단순한 pH조절을 통하여 약 84%까지의 침전율을 보였으며, 침전제로 Sodium Sulfide 를 사용하였을 경우 99%이상의 침전율을 나타냈다.

• 자원환경지질
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• 제42권5호
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• pp.445-455
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• 2009

미생물학적 황산염 환원은 황산염을 전자수용체로 이용하는 황산염 환원 박테리아에 의해 황산염이 황화이온으로 변환되는 과정이다. 형성된 황화이온은 주변의 용존 금속 이온과 결합하여 용해도가 낮은 금속 황화물로 침전된다. 이 연구에서는 비소와 중금속으로 오염된 송천 금은광산 일대 토양을 대상으로 하여 토착 박테리아에 의한 황산염 환원을 유도함으로써 독성 원소의 원위치 고정화 기술의 효율성을 평가하였다. 왕수 분해 결과, 대상 토양 내 비소, 구리, 납의 함량은 각각 1,311 mg/kg, 146 mg/kg, 294 mg/kg 등으로 나타나 특히 비소의 오염이 심각한 상태였다. 회분식 실험 결과, 미생물학적 황산염 환원에 의하여 pH 증가, 산화환원전위 감소, 황산염 함량 감소, 비소와 구리 함량 감소 등이 관찰되었다. 이 때 가장 높은 중금속 침전 효율을 유도하는 탄소원과 황산염의 농도 범위는 각각 0.2~0.5%, 100~200 mg/L로 나타났다. 미생물학적 또는 화학적으로 황화물 침전을 유도하게 고안된 컬럼 실험 수행 결과, 비소와 구리는 두 컬럼에서 모두 98% 이상 제거되었다. 그러나 산소를 다량 포함한 용액을 주입한 후, 화학적으로 황화물 침전을 유도한 컬럼에서는 즉각적인 비소와 구리의 재용출 현상이 나타났으나, 미생물학적 황산염 환원을 유도한 컬럼에서는 침전물이 30일 이상 장기간 안정성을 보였다. 미생물학적 컬럼 내에 형성된 검은색 침전물을 분석한 결과 FeS와 CuS로 나타났으며 비소는 대부분 철 황화물에 흡착되어 있는 것으로 확인되었다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.403-404
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• 2006

Sintered materials have been applied widely in Valve Seat Inserts (VSI). The demands for VSIs are not only good heat and wear resistance but also good machinability. The sintered materials, which are made of a mixture of manganese containing iron powder and certain types of sulfide powder, have superior machinability due to precipitation of the fine MnS particles in the matrix. This report introduces a new VSI material, which has both superior machinability, and wear resistance due to applies of this "MnS precipitation" technique.