• 한국분말재료학회지
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• 제28권6호
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• pp.497-501
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• 2021

Cobalt (Co) is mainly used to prepare cathode materials for lithium-ion batteries (LIBs) and binder metals for WC-Co hard metals. Developing an effective method for recovering Co from WC-Co waste sludge is of immense significance. In this study, Co is extracted from waste cemented carbide soft scrap via mechanochemical milling. The leaching ratio of Co reaches approximately 93%, and the leached solution, from which impurities except nickel are removed by pH titration, exhibits a purity of approximately 97%. The titrated aqueous Co salts are precipitated using oxalic acid and hydroxide precipitation, and the effects of the precipitating agent (oxalic acid and hydroxide) on the cobalt microstructure are investigated. It is confirmed that the type of Co compound and the crystal growth direction change according to the precipitation method, both of which affect the microstructure of the cobalt powders. This novel mechanochemical process is of significant importance for the recovery of Co from waste WC-Co hard metal. The recycled Co can be applied as a cemented carbide binder or a cathode material for lithium secondary batteries.

• 한국표면공학회지
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• 제55권1호
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• pp.24-31
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• 2022

This study investigated the effect of pre-treatment on the PEO film formation of AZ91 Mg alloy. The pre-treatment was conducted for 10 min at room temperature in 0.5 M oxalic acid (C₂H₂O₄) solution containing various ammonium fluoride (NH₄F) concentrations. The pre-treated AZ91 Mg specimens were anodized at 100 mA/cm² of 300 Hz AC for 2 min in 0.1 M NaOH + 0.4 M Na₂SiO₃ solution. When AZ91 Mg alloy was pretreated in 0.5 M oxalic acid with NH₄F concentration less than 0.3 M, continuous dissolution of the AZ91 Mg alloy occurred together with the formation of black smuts and arc initiation time for PEO film formation was very late. It was noticed that corrosion rate of the AZ91 Mg alloy became faster if small amount of NH₄F concentration, 0.1 M, is added. The fast corrosion is attributable to fast formation of porous fluoride together with porous oxides in the reaction products. On the other hand, when AZ91 Mg alloy was pretreated in 0.5 M oxalic acid with sufficient NH₄F more than 0.3 M, a thin and dense protective film was formed on the AZ91 Mg alloy surface which resulted in faster initiation of arcs and formation of PEO film.

• Journal of the Korean Wood Science and Technology
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• 제30권2호
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• pp.151-157
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• 2002

갈색부후균 Tyromyces palustris를 이용하여 CCA, CCFZ처리 목재에서 구리를 제거하였다. 균에 의한 구리의 제거효율을 높이기 위한 전처리 방법으로서 증기압처리와 수산처리를 검토하였으며, 적정 배양 방법을 찾기 위하여 진탕배양, 고체배양, 정치배양에서 구리 제거율을 비교하였다. 전처리 방법에서, 증기압 처리만으로는 효과적인 구리제거가 불가능하였으며, 수산처리는 구리제거율은 낮았으나 수산처리 후 균처리를 하면 제거율이 향상되었다. 배양 방법에서는 정치 배양의 구리 제거효율이 높게 나타났다. 대량 배양을 위한 공기부양식 생물반응기에 의한 구리의 제거율은 7일 배양 이후 61%의 제거율을 보였다. T. palustris에 의한 구리제거기작을 탐색하기 위하여 배양액 중에 생성된 물질을 LC/Mass 분석 결과 T. palustris에서 분비되어진 수산과 방부처리 목재 중의 구리가 결합된 수산구리 착염체의 형성이 배양액 중에 존재함이 확인됨으로 균체 외 수산의 작용이 처리재의 구리제거에 크게 관여함이 밝혀졌다.

• 한국환경과학회지
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• 제10권4호
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• pp.299-304
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• 2001

For the remediation of the contaminated soil with heavy metals, Cd, Cr, Cu, and Pb, the reaction parameters were optimized. Tartaric acid (TA) and oxalic acid(OA) as a washing agent and recovery of metals, The optimum washing conditions of TA and OA were in the ratio of 1 : 20 between soil and acid solution during 2hr reaction under unbuffered pH solutions. At the optimized reaction conditions, the removal efficiencies were compared with that of 0.1 M HCl and ethylenediamine tetraacetic acid(EDTA). TA showed higher efficiency on the removal of Pb than that of EDTA, which established for the remediation of contaminated soil with Pb and Cd metals. The recovery of metal ions from washing solution was achieved by adding calcium hydroxide and sodium sulfide by forming the precipitation of metal hydroxide and metal slfied. Optimum amounts of sodium sulgide and calcium hydroxide were Cd = 25g/$\ell$, Cu = 5~10g/$\ell$ and Pb = 5~10g/$\ell$ for the washing solution of OA and 2~5g/$\ell$ for the washing solution of TA, respectively. The amounts of $Na_2S$ and $CA(OH)_2$ for the tartaric acid was less than that of oxalic acid.

• Korean Chemical Engineering Research
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• 제51권6호
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• pp.661-665
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• 2013

ITO glass 제조공정에서 발생되는 인듐스크랩으로부터 인듐옥살산염의 제조에서 유기산의 영향을 연구하였다. 유기산의 종류, 농도 그리고 반응액의 pH, 온도, 시간 등을 변화시키면서 인듐옥살산염 제조에 미치는 영향을 조사하였다. 불순물 제거 효율은 구연산 및 옥살산 모두 비슷하였으나 구연산은 인듐과 유기산염을 형성하지 못하였다. 인듐옥살산염 제조의 최적 조건은 옥살산 농도 1.5M, pH 7, 반응온도 $80^{\circ}C$, 반응시간 6시간이었다. 한편, pH가 증가하면 회수율은 증가하지만, 순도는 감소하였다. 2회 반복으로 제조된 인듐옥살산염의 순도는 99.995% (4N5)를 나타내었다. 인듐옥살산염은 치환반응, 소성 등에 의해 인듐금속 및 인듐산화물 등으로 전환할 수 있다.

• Food Science and Biotechnology
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• 제17권3호
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• pp.534-539
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• 2008

This study investigated the effects of pretreatment and storage conditions on the properties of stored chestnuts. Effects on chestnuts of refrigerated storage (RNT) and frozen storage (FNT) with no pretreatment, frozen storage after oxalic acid treatment without blanching (FON) and with blanching (FOB) were examined. Water binding capacity, swelling power, solubility, and viscosity of the starch produced from RNT, FNT, and FON were similar to those of the starch produced from control (CON). FOB showed significant differences in these properties from CON. Textural properties of starch gels prepared from stored chestnuts except FOB also were very similar to those of CON starch gels. The sensory characteristics of steamed FON and FNT were similar to those of steamed CON except in brown color and hardness. Steamed FNT tended to have higher brown color and lower hardness than steamed FON. Steamed RNT showed significant differences in all the sensory properties except in hardness and cooked chestnut flavor. Steamed FOB was significantly higher than steamed CON in water release and off-flavor. Among the storage conditions examined, frozen storage with oxalic acid treatment is recommended for the long-term storage of chestnuts.

• 한국물환경학회지
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• 제20권2호
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• pp.176-182
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• 2004

The purpose of this study was to investigate the heterogeneous catalytic ozonation of oxalic acid by manganese (Mn) doped-granular activated carbon (GAC). In order to observe the effect of the amount of Mn doped on GAC, catalysts were manufactured by varying the impregnated Mn concentration. In this paper, the following had labeled all sorts kinds of Mn-doped GAC were labeled with suitable names according to the amount (mM) of the concentration of dipping solution: They were each named as 'Mn20', 'Mn50', 'Mn100' and 'Mn200'. These experiments were performed in a batch reactor (0.5 L) and a semi-batch reactor (1 L) and Mn-free GAC was used as a blank catalyst. The ozone decay properties of each manufactured catalyst were firstly investigated to find out the reactivity between the aqueous ozone and the catalysts. Oxalic acid removal by catalytic ozonation was then performed to demonstrate the oxidative efficiencies of each catalyst.

• 한국식품저장유통학회지
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• 제17권4호
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• pp.563-570
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• 2010

본 연구는 여름철에 집중 생산되는 오디를 이용하여 오디와인을 개발하고자 하였다. 발효 종료시점 오디과즙의 pH는 3.2~3.6, 총산 함량은 0.40~0.53%, 당도는 발효 6일째 $9.5{\sim}14.5^{\circ}brix$로 급격히 감소하였으며 이후에도 지속적으로 감소하여 발효 36일 이후에는 $3^{\circ}brix$ 부근에서 더 이상의 당 소모는 없었다. 알콜 함량은 발효 6일째 급격히 증가하여 $16^{\circ}C$와 $18^{\circ}C$는 4.5%, $20^{\circ}C$는 6.5%, $25^{\circ}C$는 8.0%로 배양온도가 높을수록 증가하여 48일째 10.5~11.5%로 측정되었다. 오디와인은 citric acid, malic acid, oxalic acid가 검출되었으며, citric acid와 oxalic acid는 발효 후 감소하였으며, malic acid는 증가하였다. 당의 종류로는 fructose, glucose, maltose, sucrose가 확인되었으며, 오디 발효에서 가장 많이 이용된 당은 glucose와 maltose 이었다. 알콜 생성량이 가장 높은 조건은 $20^{\circ}C$와 $25^{\circ}C$이었으며, 두 온도간에는 유의적인 차이는 없었다. 전자공여능은 40%(v/v) 농도에서 오디와인은 90% 이상의 높은 활성을 나타내었다. SOD 유사활성은 100%(v/v) 농도에서 오디과즙, 오디와인이 각각 80.1% 및 72.1%이었다. 아질산염 소거능은 100%(v/v) 농도에서 오디과즙과 오디와인은 각각 86.2%, 85.2%의 소거능을 보였다. 오디와인 보다 오디과즙이 더 높은 활성을 나타내었으며, 발효 후에 기능성이 증가하지는 않았지만 비슷한 수준으로 유지됨을 볼 수 있었다. 관능평가에서 전체적인 밸런스는 오디와인이 5.00로 보통 이상으로 평가되어 오디를 이용한 발효주의 산업 가능성을 확인할 수 있었다.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2017년도 춘계학술논문요약집
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• pp.336-337
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• 2017

• 한국재료학회지
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• 제28권2호
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• pp.82-88
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• 2018

Stable slurries of YSZ in aqueous suspension with added polymer dispersants, namely, poly-methacrylic acid ammonium salt (PMMA), poly-acrylic acid (PAA) and poly-acrylic-co-maleic acid (PAMA), were mixed with the monomolecular dispersants citric acid and oxalic acid. The dispersion properties of the suspension were investigated using PSA, viscosity, sedimentation, and FT-IR. The polymer dispersants and monomolecular dispersants were attached to the YSZ surface by the carboxylic group, as shown by the FTIR results. A stabilized aqueous suspension was obtained when the polymer dispersant and citric acid were mixed and compared to the use of citric acid alone as a dispersant agent. When the polymer dispersant and citric acid were mixed and milled through attrition milling, there was a smaller particle size compared to when the polymer dispersant alone was used as a dispersant agent. This study determined that the particle size of the mixed dispersant was affected by the properties of the monomolecular dispersant and that the stability of the suspension was affected by the polymer dispersant. However, when slurries of YSZ were mixed with oxalic acid, the particle bridging behavior was the result of the high degree of viscosity and the small sedimentation height.