• Korean Chemical Engineering Research
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• 제55권6호
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• pp.785-790
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• 2017

To collect zinc, Fe and Zn in spent pickling solution were extracted by using TBP (tributyl phosphate), and Zn was recovered from extracted solution to zinc oxalate particles by oxalic acid solution. The reusability of TBP solvent was also tested. The distribution coefficient of Zn was not affected by the concentration of Fe in spent pickling solution, almost constant with the values of 7.12~9.31 when extracted by TBP solvent. It was found that the extraction capacity of TBP solvent for Zn is higher than that for Fe. The extraction efficiency of Zn was higher than 95%, while most of Fe was left in aqueous phase. After the recovery, the used TBP solvent could be repeatedly reused for the extraction of Zn up to eight times. XRD analysis showed that zinc oxalate ($ZnC_2O_4$ $2H_2O$) was formed from the reaction of Zn-TBP and oxalic acid. From the results of SEM analysis, the formation of zinc oxalate particle was strongly affected by the concentration of oxalic acid. In summary, Zn in spent pickling solution was successfully separated and recovered with TBP solvent and oxalic acid solution, respectively.

• 한국표면공학회지
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• 제17권3호
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• pp.78-86
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• 1984

Hard anodic oxide film was investigated formed on pure aluminium with various temperature (30$^{\circ}-60^{\circ}C$), current densities (1.5-3.0A/$dm^2$) and concentrations(3-15g/l) of oxalic acid in 0.5M malic acid bath. The resulting characteristic of the anodic oxide film obtained were summarized as follows in the view point of physical and mechanical properties in relation with the above process variables. 1. The film thickness increased with oxalic acid concentration and bath temperature, while the reversed phenomena were obtained at a high concentration of oxalic acid and high temperature due to the severe dissolution of the anodic oxide film. 2. The hardness and the abrasion resistance were improved by lowering the addition of oxalic acid and the bath temperature. This feature was directly dependent on the porosity formed on the anodic oxide film. 3. The maximum hardness of anodic oxide film showed Hv 579 in the temperature of 30$^{\circ}C$ with the current density, 2.5A/$dm^2$ in the 0.5M malic acid bath mixed with 5g/l oxalic acid.

• 펄프종이기술
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• 제33권1호
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• pp.73-79
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• 2001

Stricter environmental demands have increased the need to replace conventional C/D bleaching sequence by chlorine-free sequence. Permanganate is well known as a powerful oxidant and have been used industrially in variable fields. However, it has considered to be difficult to use permanganate as a bleaching reagent because of its strong oxidative effect decreasing the viscosity of pulps extremely. We have tried to use permanganate as a bleaching reagent for KP under the mild condition and it was clear that pernanganate oxidized lignin remained in pulps selectively and increased pulp brightness decreasing K number of pulps with small degradation of cellulose. We have employed the neutral condition in the permanganate bleaching process in this study. In this case, permanganate was converted to manganese dioxide after bleaching reaction. The manganese dioxide is remained in the treated pulp fibers because of its insolublity in water. So it was required to reduction the manganese oxide to manganese ion by using reductants with acid. In this paper, we proposed to use oxalic acid as a reducing reagent converting manganese oxide to manganese ion after bleaching reaction. Oxalic acid plays the role as a reductant and a acid, so post-treatment after bleaching became to be easy by using oxalic acid. On the study using lignin model compounds, it was clear that permaganate react with phenols firstly, after that oxalic acid reduce the manganese oxide to manganese ion in the mixture of permanganate, phenols and oxalic acid. Several lignin model compounds ($\textit{p}$-hydroxybenzaldehyde, vanillin, syringaldehyde, veratraldehyde) are selected to elucidate the effect of substituents on reaction rate and its mechanism with permanganate including oxalic acid in this study. Except for veratraldehyde, the rate of oxidative degradation of phenolic compounds by permanganate with oxalic acid are higher than neutral condition. Especially, the degradation rate of $\textit{p}$-hydroxybenzaldehyde are strongly dependent on pH of reaction mixture. On the other hand, the degradation rate of veratraldehyde are decreased with decreasing pH and main degradation product is veratric acid. This result indicate that pH of bleaching liquor should be kept over 2 to degrade of non-phenolic lignin in the pulps effectively in permanganate bleaching.

• Journal of Electrochemical Science and Technology
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• 제10권4호
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• pp.416-423
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• 2019

A novel non-enzymatic oxalic acid (OA) sensor based on the platinum/carbon black-nickel-reduced graphene oxide (Pt/CBNi-rGO) nanocomposite is reported. The nanocomposites were prepared by the ethylene glycol reduction method. Their morphology and chemical composition were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The results clearly demonstrated the formation of the Pt/CB-Ni-rGO nanocomposite. The electrocatalytic activity of the Pt/CB-Ni-rGO electrode was investigated by cyclic voltammetry. It was determined that the appropriate amount of Pt enhanced the catalytic activity of Pt for oxalic acid electro-oxidation. Moreover, the modified electrode was determined to be highly selective for oxalic acid without interference from compounds commonly found in urine including uric acid and ascorbic acid. The chronoamperometric signal gave a wide linearity range of 20 μM-60 mM and the detection limit (3σ) was found to be 2.35 μM. The proposed method showed high selectivity, stability, and good reproducibility and could be used with micro-volumes of sample for the detection of oxalic acid. Finally, the oxalic acid content in artificial and control urine samples were successfully determined by our proposed electrode.

• 한국토양환경학회지
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• 제5권1호
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• pp.45-54
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• 2000

본 연구는 중금속(Zn, Cd)으로 오염된 토양을 여러 세척 용제(물, mineral acid, chelating agent, organic acld)를 가지고 탈착시켜 제거하는 실험으로 pH와 농도에 따라 회분식과 연속식 실험을 병행하였다. 물과 NaOH에 의한 세척 효과는 거의 없는 것으로 나타났으며 HCI, EDTA, Oxalic acid에 의한 세척 효과는 매우 높게 나타났다. HCI에 의한 세척효과가 가장 높은 이유는 낮은 pH에 의한 중금속의 이온화 현상에 의한 것으로 사료되며 EDTA, Oxalic acid의 효과가 높은 것은 용해도를 증가시켜 중금속 이온과 많은 착물을 형성하기 때문이다. 또한 Zn이 Cd보다 대체적으로 탈착율이 좋았으며 일반적으로 제거 경향은 pH가 낮을수록, 세척 용제의 농도가 높을수록 탈착율이 증가하였다. 중금속으로 오염된 토양 복원시 Zn의 세척 용제로는 HCI 과 EDTA를, Cd의 세척 용제로는 HCI과 Oxalic acid를 가지고 세척을 함으로써 효과적으로 정화되는 것을 알 수 있었다.

• 자원리싸이클링
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• 제11권3호
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• pp.10-16
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• 2002

폐리튬이온전지로부터 추출한 $LiCoO_2$의 침출에서 황산, 질산과 같은 강산은 Co와 Li을 완전 용해시키므로 Co와 Li을 분리하여 회수하기 위해서는 별도의 공정이 필요하다. 낮은 pH에서 Co oxalate의 용해도가 낮다는 점을 착안한 oxalic acid 침출에서 양극활물질로부터 Co를 선택적으로 회수하는 연구를 수행하였다. 변수실험으로 도출된 최적조건, oxalic acid 3M, 침출온도 $80^{\circ}C$, 초기 광액농도 50g/L.의 조건에서 순수한 $LiCoO_2$를 침출한 결과, Li이 95% 이상 용해되는 반면에 Co는 1% 이하의 침출율을 나타내었다. 같은 침출조건에서 폐리튬이온전지로부터 선별한 양극활물질을 침출한 결과, Co와 Li의 침출율은 각각 0.25%, 99%로 높은 선택성을 보였다. 용액 중에 잔류하는 Li은 $Na_2$$CO_3$혹은 LiOH을 첨가하여 Li 탄산염 흑은 Li 수산화물의 형태로 회수할 수 있다.

• 공업화학
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• 제8권1호
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• pp.108-113
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• 1997

본 연구에서는 질산매질에서 UV 광조사에 의한 옥살산 분해연구가 수행되었다. UV 광원은 $2537{\AA}$의 파장을 방출하는 수은램프가 사용되었다. UV 광조사에도 불구하고 옥살산 자체는 분해되지 않았다. 그러나 질산매질하에서 UV 광조사에 의해 옥살산은 쉽게 분해되었다. UV광조사에 의해 $NO_3{^-}$으로부터 발생되는 산소라디칼이 옥살산을 분해시키는 것으로 조사되었다. 옥살산 분해율은 질산 0.5M 부근에서 최대를 이루다가 질산농도 증가에 따라 점차 감소하였다. 이것 역시 산소라디칼과 $NO_3{^-}$ 사이에서 반응으로 쉽게 설명될 수 있다.

• 한국의류학회지
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• 제28권1호
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• pp.131-142
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• 2004

When the cotton/polyester fiber mixed fabrics were treated with ferrous sulfate and oxalic acid for burn out finishing, it was examined how the effects of process conditions as concentration of burn out agents, temperature, time and pressure act onto the properties of polyester ground fabrics. The results are as follows. The effect of burn out finishing by pressure was greated in 3 kgf/$\textrm{cm}^2$. The properties as white index and tensile strength of polyester ground fabrics were decreased according as processing concentration, temperature time increases. The shrinkage was increased according as processing concentration, temperature time increases. The optimum condition of burn out agents to ferrous sulfate was 30% concentration, 150$^{\circ}C$, 1 min, 3 kgf/$\textrm{cm}^2$ and to oxalic acid was 10% concentration, 110$^{\circ}C$, 1min, 3 kgf/$\textrm{cm}^2$. And the optimum of ferrous sulfate and oxalic acid used in combination was 10% ferrous sulfate and 7% oxalic acid, 110$^{\circ}C$, 1 min., 3 kgf/$\textrm{cm}^2$.

• Restorative Dentistry and Endodontics
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• 제6권1호
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• pp.37-50
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• 1980

Scanning Electron Microscopic (SEM) examination on the labial surface of 91 permanent upper incisors were made after etching procedure with phosphoric acid, sulfuric acid, nitric acid, hydro chloric acid, oxalic acid, formic acid, citric acid and zinc phosphate liquid for 2 minutes. Following results were obtained. 1. In the surfaces etched by 10%. 50% phosphoric acid, 50% sulfuric acid, 10%. 30% nitric acid, 10%. 50% oxalic acid, 10%. 30%. 50% formic acid, 30%. 50% citric acid and zinc phosphate liquid, there appeared to be a preferential removal of prism cores, but in the surfaces etched by 10% phosphoric acid, 50% nitric acid, 10%. 30% hydrochloric acid and 30% oxalic acid, the prism peripheries were removed preferentially. 2. According to Silverstone classification on enamel etching pattern the surface treated by zinc phosphate liquid, 30. 50% citric acid, 10%. 30%. 50% formic acid, 10%. 50% oxalic acid, 10%. 30% nitric acid, 50% sulfuric acid and 10%. 50%. phosphoric acid showed Type 1, and etched by 30% oxalic acid, 10%. 30% hydrochloric acid, 50% nitric acid and 10% phosphoric acid showed Type II. Etching of prism cores was by far the most common occurence. The changes produced could be related to intrinsic differences in histology and / or solubility of enamel.

• 한국재료학회지
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• 제22권10호
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• pp.526-530
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• 2012

Silica-based ceramic-matrix composites have shown promise as advanced materials for many applications such as chemical catalysts, ceramics, pharmaceuticals, and electronics. $SiO_2$-CuO-$CeO_2$ multi-component powders and their thin film, using an oxalic acid template as a chelating agent, have larger surface areas and more uniform pore size distribution than those of inorganic acid catalysts. $SiO_2$-CuO-$CeO_2$ composite powders were synthesized using tetraethylorthosilicate, copper (II) nitrate hemi (pentahydrate), and cerium (III) nitrate hexahydrate with oxalic acid as template or pore-forming agent. The process of thermal evolution, the phase composition, and the surface morphology of these powders were monitored by thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffractometry (XRD), field-emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectrometry (EDXS). The mesoporous property of the powders was observed by Brunner-Emmett-Teller surface (BET) analysis. The improved surface area of this powder template with oxalic acid was $371.4m^2/g$. This multi-component thin film on stainless-steel was prepared by sol-gel dip coating with no cracks.