• Fibers and Polymers
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• v.7 no.1
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• pp.20-25
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• 2006

The alkaline dissolution behavior of sea-island type polyarnide microfibers were successfully monitored using a cationic dye staining method. Weight reduction behavior of the alkali-treated microfiber fabrics and the treated fabrics stained with cationic dye were investigated in a comparative manner. The termination of dissolution monitored by both methods was also confirmed by scanning electron microscopy.

• Textile Coloration and Finishing
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• v.22 no.4
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• pp.325-331
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• 2010

The alkaline dissolution behavior of sea-island type ultrafine nylon fiber were dependent on the concentration of NaOH and treatment time, and the most appropriate condition for alkaline dissolution was to treat with 20g/l NaOH for 30 min at $80^{\circ}C$. The dyeing properties of sea-island type ultrafine nylon fiber and regular nylon fiber were examined with 3 different types of acid dyes in this study. The dye uptakes of ultrafine nylon fiber were higher than regular nylon fiber because of large surface area per unit mass, which increased as the dye bath pH decreased. The dyeing rates on ultrafine nylon fiber were faster and dye exhaustions were higher than regular nylon fiber, however color strength and rating of wash fastness were lower. It was also found that levelling type acid dye showed fast dyeing rate on both nylon fibers than metal-complex and milling type acid dyes.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.419-425
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• 2024

The purpose of this study is to improve the concentration of U(VI) in carbonate solution reasonably, which to improve the application potential of the alkaline reprocessing processes. The dissolution behavior of U₃O₈ in carbonate peroxide solutions was investigated under different conditions, including pH, carbonate concentration, and solid-liquid ratio. The results showed that the dissolution rate of U₃O₈ increased with the increase of pH from 8 to 11 in the mixed carbonate solution containing 0.5 mol/L H₂O₂. The role of carbonate ions in the dissolution of U₃O₈ was further elucidated by observing the dissolution of UO₄⋅4H₂O in carbonate solutions. Furthermore, the concentration of U(VI) in 3 mol/L Na₂CO₃ solution was successfully increased to 350 g/L under ultrasonic-assisted conditions at 60 ℃ and a solid-liquid ratio at 1/2 g/mL. Meanwhile, it is suggested that increasing the concentration of carbonate ions can improve the stability of the dissolved solution containing uranyl peroxycarbonate complex.

• YAKHAK HOEJI
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• v.30 no.1
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• pp.14-23
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• 1986

This study was conducted to investigate the correlation between the dissolution rates and the bioavailabilities of commercial phenytoin products, and also the correlation between their biovailabilities in rabbits and those in humans. Dissolution test was conducted in pH 9. 0 alkaline borate buffer (0.2M) using basket method with seven phenytoin products commercially available. According to the dissolution rate, the phenytoin products were divided into three groups, such as rapid, intermediate and slow group. Three phenytoin products from each group were selected for the bioavailability test in rabbits and humans. The bioavailability test was carried out in rabbits and normal volunteers using cross over design. Single doses of 20mg/kg and 300mg/man were orally administered to rabbits and normal volunteers respectively. Average $C_{max}$, $t_{max}$ and AUC of three phenytoin products were determined from the serum concentration-time curve in rabbit and human experiments. The relative bioavailability evaluation was conducted using AUC of three phenytoin products. The correlations between the dissolution rate constants and bioavailabilities (AUC) of three phenytoin products in rabbits as well as those in humans were not found. Whereas, there was significant correlation between average AUC of three phenytoin products in humans and those in rabbits (r=0.993, p<0.1). From the results of this experiment, it can be concluded that the bioavailability of phenytoin products in humans may be predicted from the results of the rabbit experiment. Also it is assumed that the prediction of the bioavailability of phenytoin products in humans may be difficult from the only results of in vitro dissolution test.

• Journal of Hydrogen and New Energy
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• v.20 no.5
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• pp.447-454
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• 2009

Electrolyzed reduced water was known as an alkaline solvent than piped water, natural water and mineral water etc. By means of reduction property, electrolyzed reduced water could dissolve a solute than other kinds of water without chemicals. In this study, serpentine dissolution in electrolyzed reduced water was investigated as a novel pre-treatment of serpentine which was a minerals for carbon dioxide sequestration. The elements (Ca, Si, Mg etc.) of serpentine were dissolved rapidly at early in the dissolvation then after some minutes the solubilities of serpentine elements showed stable state without abrupt changes. In spite of serpentine elements dissolution, chemical bondings and crystallographic structure of serpentine were not changed. It was explained that the dissolution mechanism of serpentine occurred from surface in electrolyzed reduced water and bulk structure sustained without collapse.

• Journal of the Mineralogical Society of Korea
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• v.5 no.2
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• pp.61-71
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• 1992

Through the low-temperature(60-150${\circ}C$) hydrothermal treatment of perlite with the alkaline solution at various NaOH concentrations, the mode of volcanic glass alteration and resultant zeolite formation were investigated in a closed system. At a temperature of 80${\circ}C$ and alkalinities of pH range 8 to 12, corresponding to the natural environments of diagenetic zeolite formation, only weak dissolution of perlitic glass occurs without zeolite formation despite the residence time of 100 days. Activities of Si and Al increase progressively, as a consequence of increasing pH, whereas activity ratios of Si/Al decrease. Zeolites were synthesized from perlite in the alkaline solution at above 0.1M NaOH concentrations. Below the temperature of 100${\circ}C$ Na-P was mainly formed, whereas analcime was the dominant zeolite at the temperature range of 100-150${\circ}C$. During Na-P synthesis chabazite and Na-X were also formed as by-products in case of lower proportion of solution/sample(<10ml/g) and higher NaOH concentraion (>3M), respectively. The alteration modes of perlite in the zeolite synthesis reflect that the formation of synthetic zeolites occurs as an incongruent dissolution likely with the diagenetic formation of natural zeolites from volcanic glass. Considering much difference in reaction kinetics between natural and synthetic systems, however, the evaluated synthetic conditions in these experiments were not directly applicable to the natural diagenetic system.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.2
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• pp.51-59
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• 2019

There is increasingly more research focusing on the application of FRP reinforcing bars as an alternative material for steel reinforcing bars, but most such research look at short term behavior of FRP reinforced structures. In this study, the microscopic analysis and tensile behavior of Basalt and Glass FRP bars under freezing-thawing and alkaline conditions were experimentally evaluated. After 100 cycles of the freezing and thawing, the tensile strength and elastic modulus of FRP bars decreased by about 5%. In the case of microstructure of FRP bars during the initial 20 days, no significant damages of FRP bar sections were found under $20^{\circ}C$ alkaline solution; however, the specimens immersed in $60^{\circ}C$ alkaline solution were found to experience resin dissolution, fiber damage and the separation of the resin-fiber interface. In the alkaline environment, the strength decrease of about 10% occurred in the environment at $20^{\circ}C$ for 100 days, but the tensile strength of FRPs exposed for 500 days decreased by 50%. At temperature of $40^{\circ}C$ and $60^{\circ}C$, an abrupt decrease in the strength was observed at 50 and 100 days. Especially, the tensile strength decrease of Basalt fiber Reinforced Polymer bars showed more severe degradation due to the damage caused by dissolution of resin matrix and fiber swelling in alkaline solution. Therefore, in order to improve the long-term performance of the surface braided FRPr reinforcing bars, surface treatment is required to ensure alkali resistance.

• Journal of the Mineralogical Society of Korea
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• v.9 no.1
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• pp.1-6
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• 1996

Woolastonite from Susan occurs as intercalations in limestone beds of Lower Paleozoic Joseon Supergroup. It is a thermal metamorphic product of impure limestone. Electron microprobe analysis shows that it is considerably pure wollastonite. It has triclinic cell with a=7.932$\AA$, b=7.328$\AA$, c=7.069$\AA$, $\alpha$=89.995$^{\circ}$, $\beta$=$95.255^{\circ}$, and $ \Upsilon=103.367^{\circ}$.Dissolution behaviors of wollastonite have been studied conducting three different dissolution experiments; two different reactions with HC1 (one batch and one re-initialization experiment) and one traction with distilled water. In the batch type powder wollastonite-HCl reaction, pH of solution rapidly increases in the early stage and then its rate of increase slows down to reach plateau resulting in parabolic relationship with time. It is represented by the early rapid rise and fall in pH giving a sharp pH-edge and succeeding slow rise in the re-initialization experiment. The early rapid rise in pH is due to the rapid sorption of H- in solution to oxygens on the reactive surface of wollastonite and the fall in pH means that all reactive surface sites are occupied by H- ions and no more H- adsorption occurs. The slow rise in pH following the pH- edge is due to the dissolution of wollastonite as evidenced by the correlation of pH variation and cation concentration. Dissolution of powder wollastonite in HCl shows linear trend with time. Si is dissolved predominantly over Ca at a constant rate. Ca is dissolved predominantly in the very early stage. Dissolution rate of coarse-grained wollastonite fragments in distilled water is parabolic with times howing a rapid reaction in the early stage and a slow reaction in the advanced stage. The Ca/Si ratio in solution is high in the case of coarse-grained wollastonite fragment as compared with powder wollastonite. The coarse-grained wollastonite fragment-water (acid) reaction resulted in the solution with an elevated constant pH value (alkaline) giving an important significance on the environmental view point.

• Analytical Science and Technology
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• v.37 no.1
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• pp.47-62
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• 2024

Abu Gurdi area is located in the South-eastern Desert of Egypt which considered as volcanic massive sulfide deposits (VMS). The present work aims at investigating the ore mineralogy of Abu Gurdi region in addition to the effectiveness of the hydrometallurgical route for processing these ores using alkaline leaching for the extraction of Zn, Cu, and Pb in the presence of hydrogen peroxide, has been investigated. The factors affecting the efficiency of the alkaline leaching of the used ore including the reagent composition, reagent concentration, leaching temperature, leaching time, and Solid /Liquid ratio, have been investigated. It was noted that the sulfide mineralization consists mainly of chalcopyrite, sphalerite, pyrite, galena and bornite. Gold is detected as rare, disseminated crystals within the gangue minerals. Under supergene conditions, secondary copper minerals (covellite, malachite, chrysocolla and atacamite) were formed. The maximum dissolution efficiencies of Cu, Zn, and Pb at the optimum leaching conditions i.e., 250 g/L NaCO₃ - NaHCO₃ alkali concentration, for 3 hr., at 250 ℃, and 1/5 Solid/liquid (S/L) ratio, were 99.48 %, 96.70 % and 99.11 %, respectively. An apparent activation energy for Zn, Cu and Pb dissolution were 21.599, 21.779 and 23.761 kJ.mol^-1, respectively, which were between those of a typical diffusion-controlled process and a chemical reaction-controlled process. Hence, the diffusion of the solid product layer contributed more than the chemical reaction to control the rate of the leaching process. High pure Cu(OH)₂, Pb(OH)₂, and ZnCl₂ were obtained from the finally obtained leach liquor at the optimum leaching conditions by precipitation at different pH. Finally, highly pure Au metal was separated from the mineralized massive sulfide via using adsorption method.

• Textile Coloration and Finishing
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• v.16 no.1
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• pp.40-47
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• 2004

Alkaline treatment gives Sea-Island type yam to produce microfiber and silk-like touch. But this treatment have some problems in dyeing and finishing process. To solve some problem occurred in dyeing and finishing of polyester fabric, the ultrasonic treatment technique was used recently. This study was carried out to confirm the effect of the ultrasonic treatment on alkaline weight loss finishing of polyester fiber under general alkaline treatment conditions; NaOH concentration 2, 3, 4, and 5％, treatment time 5, 10, 15, and 20 minutes, treatment temperature 70, 80, 90, and 99'E, respectively. On the other hand, the three way lay out method was used to test of significant obtained data from alkaline treatment. It was found that weight loss increased with increasing the NaOH concentration, temperature, and time. Also, in case of PET/Co-PET fabrics by ultrasonic, weight loss and dissolution of microfiber were superior to PET/Co-PET fabrics without ultrasonic. Tensile strength and modulus decreased with increasing NaOH concentrations and hydrolysis time. Therefore, the effect of alkali hydrolysis by ultrasonic application was better than that of the conventional method.