• Nuclear Engineering and Technology
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• 제54권5호
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• pp.1909-1913
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• 2022

This work shows the technical feasibility to obtain uranium tetrafluoride through an electrochemical mercury cell. This technique represents a custom scaling-up methodology from our previous studies to obtain UF₄ using the dropping mercury electrode cell. The UF₄ products were obtained from natural UF₆ gas, which was hydrolyzed to obtain a 50 g/L UO₂F₂ solution. The electrolysis cell was made using a mercury reservoir, to reach UF₄ production rates of 1 Kg UF₄/day. This custom design allowed a stable UF₄ production thanks to the mercury cathode, which do not permit the accumulation of solid products in its surface. The cell was tested using current densities from 5.000 to 17.500 A/m² and temperatures from 25 to 65 ℃. The maximum current efficiency achieved under these conditions was 80%. The UF₄ powders possessed spherical morphology, with diameters between 20 and 80 ㎛. Compared to the SnCl₂ precipitation, this process did not allow preferential growth of the precipitates. This improved the compaction of the UF₄ - Mg powders mixtures, with densities between 3.0 and 3.5 g/cm³. The purity of the UF₄ products was over 98%.

• 한국식품과학회지
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• 제38권4호
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• pp.488-494
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• 2006

두부 순물을 UF막으로 농축시켜 제조한 UF 분리농축분말의 일반성분 및 이들 분말을 식품에 첨가할 경우 반드시 고려해야 할 용해도, 유화력, 거품형성능에 대해 살펴보았다. 그 결과 일반 성분에 있어서, UF 분리농축분말의 수분함량과 탄수화물 함량은 순물과 큰 차이가 없었으며 단백질 함량은 순물분말보다 2배가량 높았으나 회분함량은 2배 낮았다. 유지흡착력을 비교 시 ISP>UF 농축분말>순물 순으로 높게 나타났으며 UF 분리농축 분말의 용해도가 ISP와 순물에 비해 높기 때문에 수분흡착력은 매우 미약하였다 UF 분리농축분말의 단백질의 용해도는 등전점 부근인 pH 4.0에서 가장 낮았으며 산성 또는 알칼리성으로 갈수록 증가하는 전형적인 단백질 용해도 곡선을 나타내었다. 유화력은 ISP와는 달리 pH에 따른 현화를 보이지 않으며 150-200 정도의 EAI 값을 나타내었고, 유화안전성은 pH 6.0 이하의 산성에서 더 높은 값을 나타내며 대체로 75-92%의 높은 유화안정성을 보였다. UF 분리농축분말의 거품형성능은 증류수 처리구간에서 ISP와는 달리 pH 4.0-6.0에서 가장 우수하였으며 NaCl 농도가 높을수록 약간 감소하는 경향을 나타내었고, 거품안정성을 측정한 결과 ISP에 비해 대두 단백질의 등전점인 pH 4.0 부근에서 5-7배 높은 거품안정성을 나타내었으나 pH 4.0을 제외한 모든 pH 구간에서 20분 안에 거품이 소멸되었다 UF 분리농축분말은 isoflavone 등 여러가지 기능적 성분을 함유하는 것으로 알려져 있을 뿐만 아니라 용해도, 유화력, 유화안정성, 거품형성능 등이 ISP보다 우수하여 식품가공에서 다양하게 활용될 수 있을 것으로 기대된다.

• Preventive Nutrition and Food Science
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• 제11권4호
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• pp.333-338
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• 2006

This study was conducted to investigate the quality characteristics of muffins with added ultrafiltered (UF) sunmul powder. Muffins were prepared with four different levels of UF powder (0%, 3%, 5% and 7%) and the physicochemical properties were examined. The volume and specific volume were lower in muffins prepared with UF powder than the control. The incorporation of UF powder in muffin lowered the lightness values but increased the redness values. Rheology testing showed that hardness increased with increasing UF powder and gumminess and brittleness were the highest in the control group and decreased with increasing UF powder. Initial isoflavone content was 2.39$\sim$5.57 mg%, and decreased to 1.81$\sim$4.09 mg% after baking, resulting in 24$\sim$37% reduction in muffin formulations. Scanning electron microscopy showed that the size of the air cells increased with increasing UF powder levels. In sensory evaluation, overall acceptability score was the highest in muffins with 3% added UF powder and no significant difference was observed between control and 7% addition. Therefore, muffins prepared with up to 7% addition of UF powder would be at least as acceptable as control muffins.

• 한국식품조리과학회지
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• 제21권5호
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• pp.647-654
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• 2005

This study was conducted to investigate the quality characteristics of Jeung-Pyun prepared with the addition of ultrafiltered(UF) sunmul powder. Jeung-Pyun was prepared with five different levels of UF powder(0%, 0.5%, 1%, 2% and 3%) and the physico-chemical properties were examined. The pH of Jeung-Pyun batters decreased from $4.57{\sim}5.69$ to $4.38{\sim}5.03$ during 4 hours of fermentation at $35^{\circ}C$. The weight of Jeung-Pyun decreased, whereas the volume increased, with increasing UF powder content. Total isoflavone content was $0.41{\sim}2.39\;mg%$ before cooking and increased to $0.77 {\sim}3.80\;mg%$ after cooking. The increase of aglycones was particularly observed after cooking. The incorporation of UF powder in Jeung-Pyun lowered the lightness values but increased the redness and yellowness values. Rheology test showed that hardness was decreased with increasing UF powder amount. The values of gumminess and brittleness were the highest in the control group and decreased with increasing UF powder amount. Scanning electron microscope showed that the size of the air cells decreased with increasing UF powder levels. The results of sensory evaluation showed that there were no significant differences in scores of sweetness and moistness among the samples. Therefore, Jeung-Pyun prepared with UF to 3% addition of UF powder was considered to be as acceptable as Jeung-Pyun prepared without UF power.

• Journal of the Korean Wood Science and Technology
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• 제26권4호
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• pp.92-97
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• 1998

Four urea-formaldehyde (UF) resins were synthesized as a particleboard (PB) binder with the four different initial formaldehyde/urea mole ratio and the final mole ratio of 1.15. The UF resins were characterized according to the standard method of resin adhesive analysis. PBs were manufactured using liquid UF resins at 5 minutes press time and 6% resin solids levels on an ovendry particle weight basis. A total of 20 PBs was fabricated for 5 panel replication per UF resin types. The panels were tested for physical strength properties per the procedure ASTM D 1037. The formaldehyde emission levels from the PBs bonded with the UF resins were tested according to 2-hour desiccator test method ASTM D 5582. There were no significant differences among UF resin types for internal bond strength of PBs. But there were significant differences among UF resin types for formaldehyde emission level of PBs. The results showed that the formaldehyde emission level was influenced by the UF resin types without reducing the adhesive performance.

• Environmental Engineering Research
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• 제23권2호
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• pp.159-163
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• 2018

The feasibility of applying coagulation-integrated microfiltration (MF) as a pretreatment for an ultrafiltration (UF) feed in oily wastewater treatment was investigated. The effects of different coagulants on oil removal rates from wastewater were studied. The maximum oil removal rate of 82% was obtained after coagulation with 130 mg/L of polyaluminium chloride (PAC). UF flux reached $95L/(m^2{\cdot}h)$ with coagulation-integrated MF as pretreatment. This value was 2.5 times higher than that flux obtained without pretreatment. The value of UF flux increased as the transmembrane pressure (TMP) and cross-flow velocity (CFV) of the UF module increased. UF flux gradually increased when TMP and CFV exceeded 0.4 MPa and 3 m/s, respectively, because of concentration polarization and membrane fouling stabilization. Chemical oxygen demand reduction and oil removal rate reached 95.2% and 98.5%, respectively, during integrated membrane processing with a PAC concentration of 130 mg/L, TMP of 0.4 MPa, and CFV of 3 m/s for UF. In addition, sequentially cleaning the fouling membrane with NaOH and $HNO_3$ aqueous solutions caused UF flux to recover to 90%. These encouraging results suggested that the hybrid integrated membrane process-based coagulation and MF + UF are effective approaches for oily wastewater treatment.

• Journal of the Korean Wood Science and Technology
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• 제39권2호
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• pp.179-186
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• 2011

In an effort to understand the hydrolytic degradation process of cured urea-formaldehyde (UF) resins responsible for the formaldehyde emission of wood-based composite panels, this study analyzed the influence of acid hydrolysis on the morphology of cured UF resins with different formaldehyde/urea (F/U) mole ratios such as 1.6, 1.4, 1.2 and 1.0. Field emission-scanning electron microscopy (FE-SEM) was employed to observe both exterior and fracture surfaces on thin films of cured UF resins before and after the etching with hydrochloric acid as a simulation of the hydrolytic degradation process. FE-SEM images showed that the exterior surface of cured UF resin with the F/U mole ratio of 1.0 had spherical structures after the acid hydrolysis while the other cured UF resins were not the case. However, the fracture surface observation showed that all the samples possessed spherical structures in the cured state of UF resins although their occurrence and size decreased as the F/U mole ratio increased. For the first time, we found the spherical structures in cured UF resins of higher F/U mole ratio of 1.4. After the acid hydrolysis, the spherical structures became a much predominant at the fracture surface. These results indicated that the spherical structures in cured UF resinswere much more resistant to the hydrolytic degradation by the acid than amorphous region.

• Journal of the Korean Wood Science and Technology
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• 제36권2호
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• pp.63-72
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• 2008

As a part of abating formaldehyde emission of urea-formaldehyde (UF) resin adhesive, this study was conducted to investigate chemical structures of UF resin adhesives with different formaldehyde/urea (F/U) mole ratios, using carbon-13 nuclear magnetic resonance ($^{13}C$-NMR) spectroscopy. UF resin adhesives were synthesized at four different F/U mole ratios such as 1.6, 1.4, 1.2, and 1.0 for the analysis. The analysis $^{13}C$-NMR spectroscopy showed that UF resin adhesives with higher F/U mole ratios (i.e., 1.6 and 1.4) had two distinctive peaks, indicating the presence of dimethylene ether linkages and methylene glycols, a dissolved form of free formaldehyde. But, these peaks were not detected at the UF resins with lower F/U mole ratios (i.e., 1.2 and 1.0). These chemical structures present at the UF resins with higher F/U mole ratios indicated that UF resin adhesive with higher F/U mole ratio had a greater contribution to the formaldehyde emission than that of lower F/U mole ratio. Uronic species were detected for all UF resins regardless of F/U mole ratios.

• Nuclear Engineering and Technology
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• 제49권3호
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• pp.541-548
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• 2017

Uranium metal used for fabrication of fuel for research reactors in India is generally produced by magnesio-thermic reduction of $UF_4$. Performance of magnesio-thermic reaction and recovery and quality of uranium largely depends on properties of $UF_4$. As ammonium diuranate (ADU) is first product in powder form in the process flow-sheet, properties of $UF_4$ depend on properties of ADU. ADU is generally produced from uranyl nitrate solution (UNS) for natural uranium metal production and from uranyl fluoride solution (UFS) for low enriched uranium metal production. In present paper, ADU has been produced via both the routes. Variation of uranium recovery and crystal structure and composition of ADU with progress in precipitation reaction has been studied with special attention on first appearance of the precipitate Further, ADU produced by two routes have been calcined to $UO_3$, then reduced to $UO_2$ and hydroflorinated to $UF_4$. Effect of two different process routes of ADU precipitation on the characteristics of ADU, $UO_3$, $UO_2$ and $UF_4$ were studied here.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권7호
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• pp.70-79
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• 2015

A sample of soil humic acid (HA) was divided by ultrafiltration (UF) into five fractions of different molecular size (UF₁: > 300, UF₂: 100~300, UF₃: 30~100, UF₄: 10~30, UF₅: 1~10 kilodaltons). Apparent average molecular weight (M_w) of the HA fractions were measured using high performance size exclusion chromatography (HPSEC), and the chemical and structural properties of the five HA fractions were characterized by elemental compositions (H/C, O/C and w ((2O + 3NH)/ C)) and ultraviolet-visible absorption ratios (SUVA, A_4/6). The organic carbon normalized-sorption coefficients (Koc) for the binding of phenanthrene to the HA fractions were determined by fluorescence quenching and relationship between the sorption coefficients and structural characteristics of the HA fractions were investigated. The elemental analysis and UV-vis spectral data indicated that the HA fractions with higher molecular weights have grater aliphatic character and lower contents of oxygen, while the HA fractions with lower molecular size have greater aromatic character and molecular polarity that correspond to greater SUVA and internal oxidation values (w). The log Koc values (L/kg C) were gradual increased from 4.45 for UF₅ to 4.87 for UF1. The correlation study between the structural descriptors of the HA fractions and log Koc values of phenanthrene show that the magnitude of Koc values positively correlated with $M_w$ and H/C, while negatively correlated with the independent descriptors of the O/C, w, SUVA and A_4/6.