• Journal of the Korean Ceramic Society
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• v.29 no.12
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• pp.963-969
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• 1992

This paper describes the feasibility for a direct production of zinc oxalate powders from zinc-loaded D2EHPA solutions combining the purification and the precipitation in one operation unit. This process has the potential as an alternative to conventional method for the synthesis of zinc oxide precursor particles from the hydrometal-lurgical processes. Zinc was extracted into D2EHPA in kerosene and then zinc-loaded D2EHPA solution was emulsified with oxalic acid-HCl solution to precipitate zinc oxalate powder, which was readily calcined to zinc oxide. The precipitation kinetics and yield were sensitive to experimental conditions. The morphology, size and size distribution of the zinc oxalate powders varied with zinc/oxalate ion riatio, temperature, and the presence of SPAN 60, which affected nucleation, growth, and the emulsion characteristics.

• Clean Technology
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• v.29 no.1
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• pp.46-52
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• 2023

Oxalic acid has been traditionally obtained via the oxidation of carbohydrates using nitric acid and catalysts. However, this process produces a variety of nitrogen oxides during oxidation and requires a separation process due to its various intermediates. These products and additional steps increase the harmfulness and complexity of the process. Recently, the electrochemical reduction of carbon dioxide into oxalic acid has been suggested as an environmentally friendly and efficient technology for the production of oxalic acid. In this electrochemical conversion system, zinc oxalate (ZnC₂O₄) is obtained by the reaction of Zn²⁺ ions produced by Zn oxidation and oxalate ions produced by CO₂ reduction. ZnC₂O₄ can then be converted to form oxalic acid, but this requires the use of a strong acid and heat. In this study, a system was proposed that can easily convert ZnC₂O₄ to oxalic acid without the use of a strong acid while also allowing for easy separation. In addition, this proposed system can also further convert the products into glycolic acid which is a high-value-added chemical. ZnC₂O₄ was effectively separated into Zn(OH)₂ powder and oxalate solution through a chemical treatment and a vacuum filtration process. Then the Zn(OH)₂ and oxalate were electrochemically converted to zinc and glycolic acid, respectively.

• Korean Journal of Environmental Agriculture
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• v.4 no.1
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• pp.31-36
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• 1985

In order to choose a suitable soil extractant for the prediction model of heavy metal content in brown rice, four extractants-0.1 M HCl, 0.1 M $HNO_3$, 0.1 M $NH_4$-oxalate and 0.001 M 2Na-EDTA, were compared by analyzing 84 soil and 45 brown rice samples collected from paddy fields adj-acent to five old zinc-mining sites. Content of cadmium and zinc in brown rice had the highest correlation coefficient to 0.001 M 2Na-EDTA and 0.1 M HCl extractants, respectively. However, the lead content in brown rice was significantly correlated with only 0.1 M $NH_4$oxalate solution. For the simultaneous prediction of zinc, cadmium and lead in brown rice, 0.1 M $NH_4$-oxalate solution was the most effective. On the multiple analysis by using various chemical characteristics of soils, pH and calcium content of soils were effective variables for the estimation of cadmium content in brown rice, while CEC and magnesium content were more effective for the estimation of zinc content in brown rice. Furthermore, for the estimation of lead content in brown rice, factors such as pH, CEC, calcium, magnesium, potassium and organic matter content were important variables in the multiple regression equation.

• Korean Chemical Engineering Research
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• v.55 no.6
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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.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.7
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• pp.870-878
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• 2009

This study was conducted to select the soybean cultivar to minimize the formation of calcium oxalate, and investigate the ingredients for total oxalate (Ox), phytate ($InsP_6$) and minerals such as calcium (Ca), magnesium (Mg), sodium (Na), zinc (Zn), and potassium (K) in 113 recommended soybean cultivars in Korea. Ca content ranged from 0.586 mg/g in Saealkong to 3.177 mg/g in Daolkong, and Mg content ranged from 0.559 mg/g in Taekwankong to 3.085 mg/g of dry seed in Seonheukkong. The total oxalate content ranged from 1.24 mg/g in Seonheukkong to 3.81 mg/g in Ilmikong, and InsP6 content ranged from 0.43 mg/g in Mailikong to 4.72 mg/g of dry seed in Dagikong. In the cross-correlation analysis for the contents of Ca, Mg, Ox and $InsP_6$, Seonheukkong and Danmi2 were selected to minimize the formation of calcium oxalate because the contents of Ca and $InsP_6$ were much higher than the content of Ox. These cultivars could be useful for producing soy foods beneficial to populations at risk for calcium oxalate kidney stones and for improved mineral bioavailability.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.2
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• pp.181-194
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• 1994

The purpose of this study was to compare the retention and fitness of crown treated with various desensitizing agents on natural teeth. Varnish, dentin primer, bonding agent and potassium oxalate treated groups and control group with no treatment were used. The retention test was executed with the Instron test machine(Instron Co.,U.S.A.) on 24 hours after cementation with zinc phosphate cement. After retention test, the teeth and crowns were washed and recemented. The cemented crowns were embedded in clear resin and sectioned with a diamond saw. The occlusal and marginal fitnesses, were measured indirectly with a stereomicroscopic photographs. The result of this study were obtained as follows : 1. The retention of control group was higher than any other desensitizing agent treated group. 2. The differences of retention among varnish, dentin primer, bonding agent and potassium oxalate treated groups were not statistically significant. 3. There were no statistically significant difference in fitness at occlusal surface and margin among control, varnish, dentin primer, bonding agent and potassium oxalate treated groups. According to these results, desensitizing agents used to protect the pulp from irritation of luting agents may adversely affect the retention of castings. Therefore, desensitizing agents should be used in limited areas carefully.

• Korean Journal of Environmental Agriculture
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• v.29 no.2
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• pp.115-119
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• 2010

Zinc (Zn) is an essential element required for growth and development of plants. However, Zn can be toxic to plants when it presents excessive amount. Phytoextraction is an economic and environment-friendly technique using plants to clean-up metal-contaminated soils. However, the technique cannot be applied in highly metal-contaminated areas because plants will not normally grow in such conditions. Therefore, this research focuses on identifying chelating agents which are biodegradable and applicable to highly metalcontaminated areas. Zn as a target metal and cysteine (Cys), histidine (His), malate, citrate oxalate, succinate, and ethylenediamine (EDA) as biodegradable chelating agents were selected. Plants were grown on agar media containing various chelating agents with Zn to analyze the effect on plant growth. Malate and His slightly increased the inhibitory effect of Zn on root growth of plants, whereas Cys, citrate, oxalate, and succinate did not show significant effects. However, EDA strongly diminished the inhibitory effect of Zn on root growth. The effect of EDA is correlated with decreased Zn uptake into the plants. In conclusion, as biodegradable chelating agents, EDA is a good candidate for growth of plants in highly Zn-contaminated areas.

• Korean Journal of Environmental Agriculture
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• v.4 no.1
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• pp.25-30
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• 1985

In order to characterize relationship between accumulation of cadmium, zinc and lead in soil and soil chemical properties and also to choose a suitable soil extractant for the prediction model of heavy metal content in brown rice, four extractants-0.1 M HCl, 0.1 M $HNO_3$, 0.1 M $NH_4-oxalate$ and 0.001 M 2Na-EDTA, were compared by analyzing 84 soil samples collected from paddy fields adjacent to five zinc-minig sites. Contents of Cd, and Pb in soil increased with Zn content and those of three elements were found to be much higher in surface soil ($0{\sim}15 cm$) than suvsqrface soil ($15{\sim}30 cm$). Contents of these elements in soil were positively correlated with soil pH, but its correlation between extractable heavy metal content and organic matter or CEC varied from region to region. These three elements were negatively correlated with Mg content of soils. The extractability of the metals was in the order 0.1 M $HCI{\geq}0.1 M$ $HNO_3>0.001 M$ 2Na-EDTA>0.1 M $NH_4-oxalate$.

• Journal of the East Asian Society of Dietary Life
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• v.5 no.2
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• pp.63-71
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• 1995

Defatted sesame flour is the by-products obtained after oil extracting process. Although this flour has high quality and quantity of protein its use is limited only for animal feed and fertilization. Sesame seeds contain antinutrients such as oxalate, phytate and phenol compounds and these compounds lower their nutritive value. recently, ultrafiltration(UF) has been used to concentrate protein from various food sources. This study was carried out to examine the effects of UF with different membrane pore size on the components of sesame protein concentrates including antinutrients and to compare with that of conventional acid-precipitated sesame protein isolate. The protein contents of sesame protein concentrates prepared by JF using 10K, 30K, 100K were 84.2%, 82.7%, 76.4% and the protein yields were 36.44%, 34.69, 31.43% and the protein contents was 88.7% Alkali extraction process at pH 9.0 followed by UF technique reduced oxalate and phytate content. There were 85% and 94% reduction of oxalate and phytate content by UF with membrane pore size of 100K daltons, respectively. However, the content of total phenol compounds was not reduced by this method. About 99% of calcium and 50% of zinc were removed by UF with membrane of 100K daltons. total essential amino acid contents of sesame protein concentrates prepared by UF were decreased slightly when compared with acid-precipitated sesame protein concentrate.

• Advances in nano research
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• v.14 no.4
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• pp.313-327
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• 2023

Zinc metal organic framework (MOF_Zn)-loaded goad nanoparticles (AuNPs) sol (Au@MOF_Zn), which was characterized by TEM, Mapping, FTIR, XRD, and molecular spectrum, was prepared conveniently by solvothermal method. The results indicated that Au@MOF_Zn had a very strong catalytic effect with the nanoreaction of AuNPs formation between sodium oxalate (SO) and HAuCl4. AuNPs in the new indicator reaction had a strong resonance Rayleigh scattering (RRS) signal at 370 nm. The indicator AuNPs generated by this reaction, which had the most intense surface enhanced Raman scattering (SERS) peak at 1621 cm -1. The new SERS/RRS indicator reaction in combination with specific aptamer (Apt) to fabricate a sensitive and selective Au@MOF_Zn catalytic amplification-aptamer SERS/RRS assay platform for carbendazim (CBZ), with SERS/RRS linear range of 0.025-0.5 ng/mL. The detection limit was 0.02 ng/mL. Similarly, this assay platform has been also utilized to detect oxytetracycline (OTC) and profenofos (PF).