• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.42 no.4
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• pp.64-70
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• 2010

In this study, hemicelluloses were pre-extracted from mixed hardwood chips using sodium hydroxide solution and then they were isolated from pre-extractives by using various solvents. Isolation was conducted by precipitating hemicelluloses with isopropanol, ethanol, 1,4-dioxane, dimethylsulfoxide (DMSO) and potassium hydroxide (KOH), respectively. The precipitate yield on alkali pre-extractives was the highest when hemicelluloses were isolated by DMSO and then precipitated with ethanol. Most precipitates were yellow colored. The efficiency of isolation was evaluated by analysing the characteristics of isolated hemicelluloses. Isolation using DMSO, KOH and 1,4-dioxane ($80^{\circ}C$) showed rather high efficiency. The highest total separation efficiency was about 77% when alkali pre-extractives were reacted with KOH and precipitated with ethanol. The quantity and purity of isolated hemicelluloses were affected by the solvent type.

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.745-754
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• 2013

This study evaluated the optimal soil washing conditions for toxic metals considering the removal efficiency of toxic metals from contaminated soils as well as from soil washing effluents. In the contaminated soils, As was the major contaminant and extracted by sodium hydroxide solution better than by sulfuric acid. However, in the case of the treatment of soil washing effluents, sodium hydroxide was less effective extractant because soil organic matter extracted by sodium hydroxide prevented the solid-liquid phase separation and toxic metal removal. In the treatment of soil washing effluents with sulfuric acid, toxic metals in the effluents were mostly precipitated at the pH above 6.5. In addition, granular ferric oxide (GFO) as an adsorbent enhanced the removal of As and Pb indicating that toxic metals in the washing effluents can be removed almost completely by the use of combined adsorption-neutralization process. This study suggests that soil washing techniques for toxic metals should be optimized based on the physical and chemical properties of the contaminated soils, the nature of chemical extractant, and the removal efficiency and effectiveness of toxic metals from the soils as well as soil washing effluents.

• Applied Biological Chemistry
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• v.33 no.3
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• pp.223-230
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• 1990

Gelatinization properties of heat-moisture treated Olchal(japonica) and Hankangchalbyeo(j x indica) waxy rice starches were compared. The blue value, light transmittance of starch suspension and viscosity in sodium hydroxide solution were similar between two starches. Olchal starch showed lower water binding capacity, swelling power md peak viscosity by amylograph than Hankangchalbyeo starch. Upon heat-moisture treatments all above parameters were decreased. The critical sodium hydroxide concentration for gelatinization was increased by treatments. The initial pasting temperature of Olchal starch was higher than that of Hankarlgchalbyeo. All amylograph reference points increased by the treatments, except the maximum viscosity or 2l% moisture-treated Olchal starch. Starches treated at 18% moisture level showd the highest value of consistency index. The activation energy of consistency index for gelatinized Olchal starch was lower than that for Hankangchalbyeo starch. The heat-moisture treatments had no effect on activation energy.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.6
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• pp.661-666
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• 2006

The compressive strength of a paste composed of a low-calcium Class F fly ash and alkaline activator solutions was investigated. These activator solutions, made with sodium hydroxide, water glass and water, have a very high $OH^-$ concentration. The composition of alkaline activator solution and temperature have been shown to notably influence the development of the compressive strength of the fly ash-cements paste. Compressive strength of 50 MPa could be achieved by curing of the fly ash at $60^{\circ}C$ for 48 hrs or $85^{\circ}C$ for 24 hrs. This study presented the optimum mixing ratio of Class F fly ash/sodium hydroxide/water glass as 25:8:2 in weight basis, and activator/fly ash as 0.6/1.0 for high strength paste.

• Advances in materials Research
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• v.9 no.3
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• pp.219-231
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• 2020

The aim of this study is to investigate the durability of fly ash based geopolymer mortar with and without protective coatings in aggressive chemical environments. The source materials for geopolymer are Fly ash and Ground Granulated Blast furnace Slag (GGBS) and they are considered in the combination of 80% & 20% respectively. Two Molarities of NaOH solution were considered such as 8M and 10M. The ratio of binder to sand and Sodium silicate to Sodium hydroxide solution (Na₂SiO₃/NaOH) are taken as 1:2 and 2 respectively. The alkaline liquid to binder ratio is 0.4. Compressive strength tests were conducted at various ages of the mortar specimens. In order to evaluate the performance of coatings on geopolymer mortar under aggressive chemical environment, the mortar specimens were coated with two different types of coatings such as epoxy and Acrylic. They were then subjected to different chemical environments by immersing them in 10% standard solutions of each ammonium nitrate, sodium chloride and sulphuric acid. Drop in compressive strength as a result of chemical exposure was considered as a measure of chemical attack and the drop in compressive strength was measured after 30 and 60 days of chemical exposure. The compressive strength results following chemical exposure indicated that the specimens containing the acrylic coating proved to be more resistant to chemical attacks. The control specimen without coating showed a much greater degree of deterioration. Therefore, the application of acrylic coating was invariably much more effective in improving the compressive strength as well as the resistance of mortar against chemical attacks. The results also indicated that among all the aggressive attacks, the sulphate environment has the most adverse effect in terms of lowering the strength.

• The Korean Fashion and Textile Research Journal
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• v.7 no.4
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• pp.439-444
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• 2005

This article describes the change in the hand value of chitosan-crosslinked cotton fabrics. The chitosan-crosslinked cotton fabrics were manufactured by mercerizing process using epichlorohydrin(ECH), 2% aqueous acetic acid and 20% aqueous sodium hydroxide. It proposed that the crosslinking and mercerizing were performed with the mixture of four different molecular weight chitosan and ECH in a single step. Cotton fabrics were dipped in the mixed solution of chitosan and ECH, picked up by mangle roller, pre-dried at $130^{\circ}C$, mercerized and crosslinked in NaOH solution and finally washed and dried. Mechanical and physical properties of the chitosan crosslinked fabric were measured on concentration and molecular weight by Kawabata Evaluation System(KES) and other instruments. As the concentration of chitosan solution increased, LT, WT, B, 2HB were increased. WT, B, 2HB, MIU, SMD, $T_0$, $T_m$ were decreased when chitosan was depolymerized. On the other hand, RT was increased when chitosan was depolymerized.

• Corrosion Science and Technology
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• v.3 no.1
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• pp.6-13
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• 2004

The effect of inhibitors on the electrochemical behavior and the stress corrosion cracking resistance of Alloy 600(UNS N06600) was evaluated in 10% sodium hydroxide solution at $315^{\circ}C$. The specimens of a C-ring type for stress corrosion cracking test were polarized at 150 mV above the corrosion potential for 120 hours with and without inhibitors such as titanium oxide, titanium boride and cerium boride. The chemical compositions of the films formed on the crack tip in the C-ring specimens were analyzed using a scanning Auger electron spectroscopy. The cerium boride, the most effective, was observed to decrease the crack propagation rate more than a factor of three compared with that obtained in no inhibitor solution. It was found that the changes of the active-passive transition potentials and the film compositions were related to the resistance to stress corrosion cracking in high temperature caustic solution.

• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.399-403
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• 1998

The gelation characteristics of chitosan of different molecular weight were investigated in terms of concentration and temperature of alkari aqueous solution. The average molecular weights and the degrees of deacetylation of the chitosan used were $2.0{\times}10^5$, $5.2{\times}10^5$, $8.2{\times}10^5$ and 85%, respectively. Sodium hydroxide solution was used as a gelation agent. A simple diffusion model was applied to study the gelation rate. The diffusion coefficients of the gelation agent in the chitosan gel increased with increasing its concentration, temperature of the casting solution, and molecular weight of the chitosan.

• Journal of Energy Engineering
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• v.29 no.3
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• pp.34-41
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• 2020

Used disposable diapers have been considered for a long time as a type of waste difficult to recycle and valorize due to their composite nature including plastic, cellulose pulp, a super absorbent polymer and either urine, feces or both. Therefore, the fate of disposed diapers often is either incineration or landfill burial which both have various adverse environmental impacts. However, used disposable diapers contain nutrients: cellulose is an organic matter while urine and feces contain non negligible amounts of nitrogen, phosphorus and potassium which are primary nutrients included in most chemical fertilizers used in agriculture. In a scope of waste recycling and valorization, this study focuses on developing a method to achieve nutrient solution extraction from used disposable diapers. The experiment essentially consists in shredding the diapers and letting them macerate in solutions of sodium hydroxide with various concentrations to allow breaking down of the cellulose and super absorbent polymer and release of urine and feces before sterilizing the solutions in an autoclave to remove potential coliform bacteria. At the end of the experiment, a set of parameters is measured for the final solution to identify concentrations of nutrients as well as presence or absence of harmful substances. Results are discussed and directions for future studies are suggested, which include mechanization of the diapers shredding process or added aeration to enhance nitrification and absorption of extracted nutrients from plants.

• Carbon letters
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• v.13 no.4
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• pp.212-220
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• 2012

Orange peel (OP) exhibits a sorption capacity towards anionic dyes such as reactive blue 19 (RB19). Cetyltrimethylammonium bromide (CTAB) as a cationic surfactant was used to modify the surface nature of OP to enhance its adsorption capacity for anionic dyes from an aqueous solution. Four adsorbents were investigated: the OP, sodium hydroxide-treated OP (SOP), CTAB-modified OP and CTAB-modified SOP. The physical and chemical properties of these sorbents were determined using nitrogen adsorption at 77 K and by scanning electron microscope and Fourier transform infrared spectroscopy techniques. The adsorption of the RB19 dye was assessed with these sorbents at different solution pH levels and temperatures. The effect of the contact time was considered to determine the order and rate constants of the adsorption process. The adsorption data were analyzed considering the Freundlich, Langmuir, Elovich and Tempkin models. The adsorption of RB19 by the assessed sorbents is of the chemisorption type following pseudo-first-order kinetics. CTAB modification brought about a significant increase in RB19 adsorption, which was ascribed to the grafting of the sorbent with a cationic surfactant.