• Korean Journal of Food Science and Technology
• /
• v.53 no.2
• /
• pp.121-125
• /
• 2021

Very low methoxyl pectin (VLMP) has different physical and rheological properties compared to high and low methoxyl pectins (HMP and LMP). In this study, we produced LMP and VLMP by alkaline de-esterification, and investigated the structural and textural properties. Apple peel pectin was kept at pH 12 using 5.0 M NaOH solution for 3 and 24 h to produce LMP and VLMP, respectively. The molecular weight was decreased due to the removal of an esterified group in the pectin backbones by the alkali treatment, and the VLMP showed a higher calcium ion sensitivity which leads to the production of the gel with increased hardness. The result clearly showed that VLMP has the potential to improve the texture and stability in food products depending on their degree of esterification, and this result can be applied as a functional ingredient in food industrial area application to enhance the current commercial pectins.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2021.11a
• /
• pp.21-22
• /
• 2021

This study incorporates fine waste glass (GS) as a replacement for natural sand (NS) in ground granulated blast furnace slag (GGBS) based alkali activated mortar (AAm). Tests were conducted on the AAm to determine the mechanical properties, apparent porosity and the durability based on its resistance to Na2SO4 5% and H2SO4 2% concentrated solutions. The study revealed that increasing GS up to 100 wt%, increased strength and decreased porosity. The lower porosity attained with the incorporation of GS, improved the resistance of mortar to Na2SO4 and thus increasing durability. However, the durability of mortar to H2SO4 solution was negatively impacted with the further reduction of porosity observed with increasing GS above 50 wt.% believed to be caused by the stress induced as a result of expansive reaction products created when the mortar reacted with acid.

• Analytical Science and Technology
• /
• v.11 no.4
• /
• pp.248-253
• /
• 1998

The adsorption and separation behaviors of alkali, alkaline earth and transition metal ions using a poly-dibenzo-18-crown-6 were investigated in aqueous solution. The adsorption degree(E) and distribution ratio(D) of alkali, alkaline earth metal ions were Li(I)$t_R$) of metal ions were affected by the adsorption degree(E) and distribution ratio(D). This results showed good separation efficiency of K(I), Sr(II), Ag(I) and Pb(II) from the mixed metal solution.

• Proceedings of the IEEK Conference
• /
• 2001.10a
• /
• pp.357-361
• /
• 2001

The possibility of producing Cr$_2$O$_3$powder from waste magnesia-chromium refractory was investigated by sulfuric acid reaction, alkali fusion, water leaching & purification and heat treatment. The effects of temperature, the amount of NaOH added and the flow rate of air on chromium extraction efficiency in an alkali fusion step were investigated. The fusion product was leached with methanol to solve free-NaOH, and then leached with water to produce a Na$_2$CrO$_4$solution. The purity of chrome(Ⅵ) oxides, prepared both from monochromate with an impurity content and monochromate purified with $CO_2$were also examined. The purified monochromate solution was reduced from Cr(Ⅵ) to Cr(III) with NaHSO$_3$solution. The reduced solution was neutralized with NaOH to produce Cr(OH)$_3$. Water washing was treated to eliminate Na$_2$SO$_4$from neutralized Cr(OH)$_3$slurry. The washed Cr(OH)$_3$was dried and thermally treated to produce Cr$_2$O$_3$powder. The properties like lightness and hue of Cr$_2$O$_3$fabricated in this study were L=47.47, a=-14.40 and b=17.21.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.32 no.2
• /
• pp.68-76
• /
• 2022

This study was performed to investigate the mechanism of the change in compressive strength of autoclave cured geopolymers. Specimens were immerged in distilled water, 2M, 8M, and 14M alkaline solutions for 3, 7, and 21 days. The change in the specimens immersed in a short period of time was not significant, but the compressive strength of the specimens immersed in the distilled water and 8M alkali solution) for 21 days increased more than twice as much as before immersion because of additional geopolymerization. However, compressive strength decreased due to the alkaline aggregate reaction when alkaline solution was supplied more than a certain level of concentration. Therefore, immersing the specimens for more than 21 days in the distilled water or 8M alkaline solution would be desirable for the improvement of compressive strength of autoclave cured specimens.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.11a
• /
• pp.264-267
• /
• 2007

It is important to reduce optical losses from front surface reflection to improve the efficiency of crystalline silicon solar cells. Surface texturing by isotropic etching with acid solution based on HF and $HNO_3$ is one of the promising methods that can reduce surface reflectance. Anisotropic texturing with alkali solution is not suitable for multicrystalline silicon wafers because of its various grain orientations. In this paper, we textured multicrystalline silicon wafers by simple wet chemical etching using acid solution to reduce front surface reflectance. After that, surface morphology of textured wafer was observed by Scanning Electron Microscope(SEM) and Atomic Force Microscope(AFM), surface reflectance was measured in wavelength from 400nm to 1000nm. We obtained 29.29% surface reflectance by isotropic texturing with acid solution in wavelength from 400nm to 1000nm for fabrication of multicrystalline silicon solar cells.

• Clean Technology
• /
• v.19 no.4
• /
• pp.481-486
• /
• 2013

Alkali-surfactant-polymer (ASP) solution was manufactured by using the domestic surfactants for enhanced oil recovery. Domestic surfactants such as linear alkylbenzene sulfonic acid (LAS) and dioctyl sulfosiuccinate (DOSS) were used. This surfactants were purchased from AK chemtech Co., Ltd. (Korea). LAS and DOSS were blended and the ratio of LAS to DOSS are 1:1 and 2:1. Decane was used as a model compound of the crude oil. Surfactant solution and decane were blended to analyze microemulsion. Brine-oil-surfactant are mixed at varying concentration of brine from 0.8 to 3.6 wt.%. Increasing salinity causes the phase transition of microemulsion from water to middle to oil. Also, by measuring the surface tension and interfacial tension using pendent drop tensiometer and Huh's equation optimal ratio of the ASP solution was determined.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.11a
• /
• pp.313-317
• /
• 2003

The study is the results of accelerated tests and the specimens, mortars, are submerged in a 5% sulfuric acid solution. The deterioration of specimens is followed up by investigating the change in weight and compressive strength of the specimens and techniques such as XRD and XRF are used to examine the chemical changes. Sulfuric acid is a very aggressive acid that reacts with the free lime [$Ca(OH)_2$] in the concrete forming gypsum($CaSO_{4}.2H_{2}O$). This reaction is associated with an increase in volume of the concrete, and the corroded surface becomes soft and white. The results showed that the OPC mortar caused an decrease in weight above 18% and strength loss about 57%. On the other hand, AASC(alkali-activated slag composites) did not cause any decrease in weight and in the case of strength caused an decrease below 10%. In addition, this mechanical results was verified to XRD and XRF.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2010.05a
• /
• pp.389-390
• /
• 2010

this study is preliminary experimental research for develop methods to utilize the natural Hwangtoh as replacement materials for the cement in concrete, via alkali activation at $60^{\circ}C$ using NaOH solution and liquefied $Na_2SiO_3$ in a manufacture process of Hwangtoh concrete binder.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2006.04a
• /
• pp.220-223
• /
• 2006

To investigate the effect of solution pH and particle size of Na-bentonite on swelling characteristics and relative hydraulic conductivity, four kinds of acids and two alkali were selected. The results showed that the swelling was decreased to half of the original Na-bentonite's swelling index. Also the decrease in SI was most distinctive in pH 3.5 of HCl. But changes of swelling index between initial and stabilized were minimal in alkali treatment, compared to the change by acid treatment. No flux was detected under atmospheric pressure although there was drastic decrease in swelling. However, leaching started after application of 1.5 bars of air-pressure equivalent to 15 m of water head.