• Resources Recycling
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• 제27권6호
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• pp.3-10
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• 2018

Tungsten is a metal with high melting point and used as a raw material for the production of super alloys. Tungsten exists as $WO{_4}^{2-}$ in alkaline solution. As solution pH decreases, polymerization reaction of $WO{_4}^{2-}$ occurs to result in the precipitation of tungstic acid. The hydrometallurgical process for the recovery of tungsten from ores or secondary resources can be classified as acid and alkaline leaching. In selecting a process for the recovery of pure tungsten from secondary resources, the nature and concentration of impurities in the secondary resources and the manufactured tungsten materials should be considered.

• Journal of the Korean Society of Food Science and Nutrition
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• 제32권3호
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• pp.400-405
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• 2003

The surimi processing from jack mackerel and white croaker muscle using acidic and alkaline solubilization was evaluated. The optimum pH for solubilizing protein in acidic and alkaline range was around 2.5 and 10.5, respectively. The optimum pH value for recovery of protein was around 5. The protein solubility was decreased with increase of salt. The homogenized speed and time for maximum solubility were below 9,500 rpm and 30s, respectively The optimum ratio of water to minced muscle was 6 by evaluating breaking force, deformation and whiteness of cooked gel. The protein yield of alkaline processing is higher than that of conventional processing. In addition, the waste water of conventional processing had high solid, nitrogen content and chemical oxygen demand compare to those of acidic and alkaline processing.

• Journal of Korean Society of Environmental Engineers
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• 제29권7호
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• pp.801-809
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• 2007

Fly ash and blast furnace slag are an industrial by-product that can be alkali-activated to yield adhesive and cementitious materials, whose production is less energy-intensive and emits less $CO_2$ than ordinary Portland cement manufacture. A laboratory investigation was carried out to evaluate the effect of alkali-activating conditions on compressive strength of fly ash/slag cement and the acid corrosion resistance of this cement. Two alkali activator solution, NaOH and waterglass + NaOH solutions, were used. Waterglass concentration was the factor that gave the highest compressive strength in all tests. The next significant factor was the NaOH concentration, followed by curing temperature. Acid corrosion resistance of FC(fly ash cement) and FSC(fly ash/slag cement), such as sulfuric$(H_2SO_4)$ and hydrochloric acid(HCl), was for better than Portland cement(PC).

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 한국생물환경조절학회 1996년도 심포지움 및 학술논문발표요지
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• pp.64-66
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• 1996

수경재배에서 요구되는 최적의 배양액 pH는 5.5-6.5 이고, pH를 최적의 상태로 조절해 주는 방법으로 비료의 흡수생리를 이용하는 방법과 화학적인 산알칼리 용액을 이용하여 조절해 주는 방법이 있다. 이러한 pH 조절은 자동적으로 행해야 효과가 크며 본 실험은 흡수생리적인 면에서 산 혹은 알칼리 비료를 화학적인 산 알칼리와 비교하여 pH 조절효과의 차이를 보고자 하며 생육제어시스템 중 pH의 자동계측 및 제어를 통해서 계속적인 pH의 안정적인 수준을 유지하면서 상품성과 품질이 우수한 작물을 생산하고자 이 실험을 수행하였다. (중략)

• Air Cleaning Technology
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• 제17권4호통권67호
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• pp.39-57
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• 2004

첨단산업으로 불리는 반도체, LCD, PDP, 유기EL(OLED) 등의 생산 공정은 고도의 청정상태를 요구하며, 때문에 이들의 생산공정 중 대부분이 클린룸 내에서 이루어진다. 클린룸 내에서의 주요공정은 크게 박막형성(Layering), 노광(Photo Lithography), 식각(Etching) 등 3가지 공정으로 나눌 수 있으며, 반도체 제조공정의 경우 특별히 도핑(Doping) 공정이 추가된다. 오염물질을 함유하는 클린룸 배기는 일반적으로 산, 알칼리, Toxic(PFCs, Flammable), VOC 등으로 분류하며, 각각의 배기는 각 배기특성에 맞는 오염제어 장치를 통해, 정화된 후, 대기로 방출된다. 산, 알칼리 배기는 일반적으로 최종 단계에서 중앙집중식 습식스크러버에 의해 흡수, 중화 처리되며, VOC의 경우 농축기(Concentrator) & 축열식 열 산화장치(RTO) 설비에 의해 연소 처리된다. 하지만 CVD공정으로부터의 배기가 주를 이루는 Toxic배기의 경우, 다량의 PFCs(과불소화합물) 가스를 함유하고 있는 이유로, 대부분 클린룸 내부에 P.O.U(Point of use) 처리장치가 설치되며, P.O.U에 의해 1차 처리된 후 최종적으로 중앙집중식 습식스크러버를 거쳐 대기로 방출된다. 알칼리배기의 주성분으로는 암모니아($NH_3$), HMDS (Hexa Methyl DiSilazane), TMAH (Tetra Methyl Ammonium Hydroxide), LGL, CD 등이며 흡수액에 황산(Sulfuric Acid)용액을 공급, 중화처리하고 있다. 탄소성분을 먹이로 하는 미생물의 번식에 의한 막힘 문제를 제외하고는 큰 문제가 없다. 하지만 Toxic배기 및 산배기의 경우 처리효율이, 가스흡수 이론에 의한 계산결과와 비교할 때, 매우 저조하게 나타나는 효율부족 현상을 겪고 있으며, 이는 잔여 PFCs 가스성분 및 반응에어로졸, 응축에어로졸 등의 영향으로 추정하고 있다. 최근 Toxic 배기의 경우, P.O.U 설비를 Burn & Wet type으로 변경하여, 배기 중 PFCs 및 반응에 에어로졸($SiO_2$)의 농도를 원천적으로 감소시키는 노력이 진행 중이다. 산배기의 경우, 산결로 현상에 의한, 응축에어로졸이 문제가 되고 있으나 내식열교환기(Anti-Corrosive Heat Exchanger), 하전액적스크러버 시스템(Charged Droplets Scrubber System), Wet ESP(Wet Electrostatic Procipitator) 등의 도입을 통해 문제해결을 위한 노력을 경주하고 있다.

• Journal of Korean Society of Environmental Engineers
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• 제30권1호
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• pp.61-68
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• 2008

A new cementitious material has been developed, called alkali-activated fly ash cement(AAFC), which is used to produce AAFC-concrete for construction. The effect of acid attack, sodium chloride solution, carbonation, freeze-thaw cycling, and SEM, XRD analysis of the AAFC-concrete prepared using alkali-activated fly ash cement and OPC-concrete were experimentally investigated. It was found that the acid resistance of AAFC-concrete(35 MPa) prepared from alkali-activated fly ash at 85$^{\circ}C$ for 24 hrs is far better than OPC-concrete(35 MPa). Also, the AAFC-concrete(35 MPa) had a similar resistance of OPC-concrete(35 MPa) to attack, such as sodium chloride solution, carbonation and freeze-thaw cycling.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제10권1호
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• pp.1-9
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• 1977

The purpose of this study is to complish a method of fish glue malting with residual products such as fish head and skin discarded from sea food processing. Using the skins of Alaska pollack and file fish from fillet packers, the optimum conditions of skin glue processing were investigated and physical and chemical properties of the product were also determined. The yields of Alaska pollack, Thelagra calcogramma, skin and file fish, Novodon modestus, skin to the total body weight were $4.6\%\;and\;5.0\%$ respectively. The optimum conditions for a $49.3\%$n yield Alaska pollack skin glue processing were considered the extraction of previously tinted in $0.1\%$ calcium hydroxide solution for 3 hours with the additional water as much as 3 times of sample weight at $70^{\circ}C$ for 3 hours under the controlled pH 5.0. The conditions for file fish skin glue were similar to those of Alaska pollack except the addition of five times of water to the weight of sample skin needed for extraction. The content of crude protein of Alaska pollack and file fish skin glue were $98.0\%\;and\;96.0\%$ respectively. The contents of crude ash and crude lipid were not different from that of chemical grade gelatin. Relative viscosity, melting point, gelation temperature and jelly strength of Alaska pollack skin glue marked 5.84, $21.8^{\circ}C,\;7.1^{\circ}C\;and\;10.0g$ respectively and those of file fish skin glue showed $5.79,\;25.0^{\circ}C,\;7.4^{\circ}C\;and\;11.6g$ respectively.The color and turbidity of Alaska pollack skin glue are slightly superior to those of file fish skin glue. It is supposed that the extract residue of skin glue is valuable for use the animal feeds by the results of amino acid composition. And the ratio of each amino acid content to the total amino acid of Alaska pollack and file fish skin glue is similar to that of chemical grade gelatin.

• Analytical Science and Technology
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• 제5권1호
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• pp.33-39
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• 1992

THF-based crown-4 of 16-membered rings having tetrahydrofuran unit was synthesized by an acid-catalyzed condensation of furan and acetone followed by hydrogenation in an effort to obtain highly elective ionophores for lithium ions. The new ionophore was compared with previously reported ionophores under similar measurement conditions with the same plasticizer, tris(2-ethylhexyl) phosphate in poly(vinyl chloride)(PVC) membrane electrodes. Separate solution method was used to determine relative selectivity coefficients for the electrode. The selectivity coefficients($K_{LiM}^{POT}$) of lithium over ammonium, alkali and alkaline earth metal ions go from about $2.4{\times}10^{-1}$ to $2.3{\times}10^{-4}$ to working range and pH dependence have also been studied.

• Analytical Science and Technology
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• 제8권2호
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• pp.187-193
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• 1995

A PVC membrane ion-selective electrodes based on N,N,N,N-tetrabenzylethylenediamine as neutral carrier has been prepared by addition of plasticizers such as phthalates and sebacate and liphophillic additives such as NaTPB. The membrane electrodes were investigated to the electric resistance, response range to hydrogen ion and the interfering effect of alkali and alkline earth metals. A electric resistance hardly had on effect of plasticizers. In case of 0.7% NaTPB added to membrane, response of the electrodes were shown the values near to theoretical Nernstian slope and interferences by alkali and alkaline earth metal were few influenced. The performances of pH-selective electrodes were shown linerality to hydrogen ion between pH 2 and 10 in the presense of alkali and alkaline earth ions. Reproducibility and stability tests were shown good results in the same pH range.

• Korean Journal of Food Science and Technology
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• 제20권4호
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• pp.488-492
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• 1988

The physicochemical properties of viscosity, color, acidity and volume of anchovy extract were measured for their changes during extraction with alkali solution and/or proteolytic enzymes. The dried anchovies were ground in 0.3N NaOH solution followed by hydrolysis with neutral or alkaline protease and centrifuged to obtain anchovy extract. The results showed that the volume of supernatant after centrifugation increased from 70% of water only extraction to 89% by combined alkali-enzyme treatment. Titratable acidity of the extract showed a tendency of a little increase while viscosiy decreased with prolonged enzymic hydrolysis. Changes in Hunter value of 'L', 'a', 'b' showed that the extract became darker and less yellowish as protease treatment prolonged.