• 한국지하수토양환경학회지:지하수토양환경
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• 제23권1호
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• pp.85-91
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• 2018

Arsenic (As) usually is bound to amorphous iron oxides in the soils, and it can be removed via dissolution of iron oxides. Inorganic acid and chelating agent are widely used to extract As in the soil washing. However, the overall performance is highly dependent on the state of As fractionation. In this study, oxalic acid and inorganic acids (HCl, $H_2SO_4$, and $H_3PO_4$) were applied to enhance the dissolution of iron oxides for remediation of As-contaminated soils. Oxalic acid was most effective to extract As from soils and removal of As was two times greater than other inorganic acids. Additionally, 75% of As bound to amorphous iron oxides was removed by 0.2 M oxalic acid. Arsenic removal by oxalic acid was directly proportional to the sum of labile fractions of As instead of the total concentration of As. Therefore, the oxalic acid could extract most As bound to amorphous iron oxides.

• 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.

• Journal of the Korean Wood Science and Technology
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• 제26권1호
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• pp.57-62
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• 1998

In this research, the removal or uptake of heavy metals such as coppers by using oxalic acid metabolism of wood rot fungi, Tyromyces palustris were endeavored. As results, the addition of oxalic acid to copper containing culture did not cause the mycelium growth, but Tyromyces palustris was able to grow in this culture without inhibition. Tyromyces palustris grew with the cicular halo type in copper containing culture, and this type was formed as collectives after examining by microscope, and considered as copper oxalates by analyzing FT-IR comparison experiment with standards. According to this result, Tyromyces palustris has secreted oxalic acid during incubation, this secreted oxalic acid was combined with coppers, and formed copper oxalates by chelating reactions. In other words, the oxalic acid was might be as non-toxifying agent of coppers in medium. By using this copper removal mechanisms, Tyromyces palustris immobilized sawdust was used in bench scale air lift system for removing coppers. The added coppers were almost removed from the system within 72hrs. Therefore, this nonenzymatic wood degradation mechanism may give a possibility for removing coppers from copper containing waste water.

• 한국연초학회지
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• 제11권1호
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• pp.3-9
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• 1989

Field experiment was conducted to find out the cause of calcium deficiency of burley tobacco (Nicotiana tabacum L.), Liming materials and application rate were CaSO4 : Ca 35kg/10a, CaCO3 : 35kg/10a and agricultural lime : Ca 142kg/10a. The breakdown in tissues at tips and margins of upper leaves was developed at maximum growth stage. If complete breakdown and death does not occur and growth takes place later, giving the leaf a scalloped appearance. Upper leaves contained lower calcium content than other leaves. The stem and midvein of calcium deficient plants contained lower calcium and calcium minus oxalic acid, but higher oxalic acid contents than those of normal plant. Fresh leaves of limed plot contained higher calcium and oxalic acid, but not significant increment of calcium minus oxalic acid than those of unlimed plot. Since calcium oxalate is insoluble, it could precipitate within the culls if the calcium and oxalic acid are accessible to each other. It suggest that high level of oxalic acid in stem and midvein could be interfering with translocation of calcium to upper leaves.

• 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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• 제54권1호
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• pp.30-36
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• 2021

In this study, double-layered anodizing films were formed on Al 5052 and Al 6061 alloys consecutively first in sulfuric acid and then in oxalic acid, and hardness, withstand voltage, surface roughness and acid resistance of the anodizing films were compared with single-layered anodizing films in sulfuric acid and oxalic acid electrolytes. Hardness of the double-layered anodizing film decreased with increasing ratio of inner layer to outer layer for both Al 5052 and Al 6061 alloys, suggesting that outer anodizing film formed in sulfuric acid electrolyte is damaged during the second anodizing in oxalic acid electrolyte. Withstand voltage of the double-layered anodizing films increased with increasing the thickness ratio of inner layer to outer layer. Surface roughness of the double-layered anodizing films were comparable with that of single-layered anodizing film formed in sulfuric acid but higher than that of single layer anodizing film formed in oxalic acid electrolyte. In acid resistance test, all of the double-layered and single-layered anodizing films showed good acid resistance more than 3 h without any visible gas evolution, which is attributable to sealing of pores. Based on the experimental results obtained in this work, it is possible to design a double-layered anodizing film with cost-effectiveness and improved physical and electrical properties by combining two consecutive anodizing processes of sulfuric acid anodizing and oxalic acid anodizing methods.

• 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.

• 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.

• 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.

• Journal of the Korean Wood Science and Technology
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• 제37권4호
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• pp.397-405
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• 2009

본 연구에서는 국내 조림 수종인 백합나무를 바이오에탄올 생산용 자원으로 이용하고자 oxalic acid 전처리 방법을 도입하여 가능성을 타진하였다. $160^{\circ}C$에서 0.037 g/g oxalic acid로 20분 전처리하였을 때 $40.22g/{\ell}$의 발효가능한 당을 생산하였으며, 처리된 고형 바이오매스를 이용하여 동시당화발효를 수행한 결과 72시간 후 $8.6g/{\ell}$의 에탄올을 생산하였다. 같은 조건에서 반응시간을 증가시켜 40분 처리하였을 때 $32.66g/{\ell}$의 발효가능한 당을 생산하였고 동시당화발효로 72시간 후 $9.5g/{\ell}$의 에탄올을 생산하였다. 가수분해산물을 분석한 결과, 같은 조건에서 반응시간이 증가함에 따라 acetic acid, 5-HMF, furfural, total phenols와 같은 발효저해물질이 증가하였다. 이와 같은 발효저해물질은 반응시간보다는 초기 oxalic acid 첨가량에 영향을 받았다. Acetic acid 생산량은 저농도(0.013 g/g)의 oxalic acid를 사용하였을 때 $3.39{\sim}5.78g/{\ell}$로 나타났으며 xylose 분해산물인 furfural은 glucose의 분해산물인 5-HMF보다 2~3배 많게 가수분해산물에 존재하였다. 리그닌 분해산물로 예측되는 total phenols는 모든 조건에서 $5g/{\ell}$ 이상이 검출되었다. 가수분해산물과 동시당화발효로부터 에탄올 생산량을 분석한 결과 0.037 g/g oxalic acid로 20분 전처리한 가수분해산물과 고형 바이오매스로부터 가장 높은 에탄올 생산을 예측할 수 있다.