• Environmental Engineering Research
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• v.22 no.2
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• pp.149-156
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• 2017

Chromium(III) recovery from tanning wastewater by means of adsorption on activated carbon and elution with sulfuric acid was studied. Tests were carried out at laboratory scale on an effluent of industrial origin. Initially, proteinaceous materials and fats were separated via sieving followed by ultrafiltration. The chemical composition of the sample thus precleansed was (in g/L): 1.09 chromium(III); 10.36 sulfate; 11.10 sodium; 9.57 chloride; 0.40 proteinaceous materials; and 0.20 fats. Adsorptions were made at 20, 30, and $40^{\circ}C$, establishing what temperature favored chromium(III) uptake. At $40^{\circ}C$, the maximum cation fixation was 40.2 mg/g, and the lowest content in an equilibrium solution was 3.9 mg/L. As regards sodium, chloride, and sulfate, the concentrations before and after the treatment were similar. Likewise, it was found that protons were also retained, modifying the pH of the liquid medium. Adsorption isotherms were analyzed using the Langmuir, Temkin, and Freundlich models. Finally, the extraction of the adsorbed tanning agent with sulfuric acid was evaluated. A recovery of 96.5% was achieved with 0.9 N at $70^{\circ}C$ (13.23 g/L $Cr^{3+}$; 42.98 g/L sulfate; and 0.40 g/L NaCl).

• Korean Journal of Plant Resources
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• v.13 no.1
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• pp.48-53
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• 2000

Lacquer tree can be proliferated by root or stem cutting, and seed. In case of proliferation by seed, however, the germination rate is very low. Thus, the present study was carried out to obtain aspceptic lacquer plant in vitro from seed because natural tissue culture was highly defiled by unknown fungi and bacteria. First seed grading on distilled water was 50.7% and second seed grading was 20.8% after 98% sulfuric acid treatment for 2 hours. Removal of inner seed coat was higher with 32.4% than non-removal of outer seed coat and removal outer seed coat in rooting rate. In germination rate according to pre-treatment, growth regulators were not effective at all, but sulfuric acid was effective a little with 3%. Removal outer seed coat was increased about 4%, that germinated about 10% in MS medium supplemented with 1.0mg/L BA and 0.05mg/L NAA, 1.0mg/L BA. Lacquer tree seeds germinated after 10 days in MS medium, and aspceptic seedling of lacquer tree were obtained after 3 weeks in vitro. Germination rate, however, was lower about 10%.

• Journal of the Korean Ceramic Society
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• v.12 no.2
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• pp.26-30
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• 1975

The experiment has been carried out to clarify the condition of acid treatment for preventing the crack formation caused by swelling and shrinking during acid leaching process. The borosilicate glass contained phosphorous pentoxide was chosen as the sample, which is recognized to be more homogeneous in phase separation. The various effects, such as kind, cocentration and acid temperature, were investigated. The experimental results are summerized as follows. (1) Sulfuric acid is more stable than hydrochrolic acid for preventing the crack. (2) The optimum concentration of acid lies in the range of 0.1~0.3N. (3) Higher temperature of the acid to treat the separated glass was more stable than lower temperature. (4) The rate of crack decreased with the longer period and the higher temperature of the heat treatment.

• Journal of the Korean Ceramic Society
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• v.24 no.5
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• pp.437-446
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• 1987

In this study the attempts were made to investigate the possibilities of using domestic clay minerals and zeolite, which are available in almost unlimitted quantities, for preparation of aluminum sulfate, white carbon and silica gel. Aluminum sulfate was obtained by the method of sulfuric acid treatment. White carbon and silica gel were prepared by utilizing crystalline silica which was obtained as a by product during preparing the aluminum sulfate. White carbon was obtained by reacting 5.0 weight percent sulfuric acid solution with water glass which was a reaction product of crystalline silica and soldium hydroxide in a autoclave, while silica gel was obtained by reaction 10.0 weight percent acetic acid solution with water glass.

• Journal of Surface Science and Engineering
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• v.47 no.3
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• pp.128-136
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• 2014

In the present study, we successfully developed an eco-friendly chemical etching solution and proper condition for plating on ABS material. The mechanism of forming Ni plating layer on ABS substrate is known as following. In general, the etching solution used for the etching process is a solution of chromic acid and sulfuric acid. The etching solution is given to the surface resulting in elution of butadiene group, so-called anchor effect. Such a rough surface can easily adsorb catalyst resulting in the increase of adhesion between ABS substrate and Ni plating layer. However a use of chromic acid is harmful to environment. It is, therefore, essential to develop a new alternative solution. In the present study, we proposed an eco-friendly etching solution composed of potassium permanganate, sulfuric acid and phosphoric acid. This solution was testified to observe the surface microstructure and the pore size of electrical Ni plating layer, and the adhesive correlation between deposited layers fabricated by electro Ni plating was confirmed. The result of the present study, the newly developed, eco-friendly etching solution, which is a mixture of potassium permanganate 25 g/L, sulfuric acid 650ml/L and phosphoric acid 250ml/L, has a similar etching effect and adhesion property, compared with the commercially used chromium acid solution in the condition at $70^{\circ}C$ for 5 min.

• Journal of the Korean Wood Science and Technology
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• v.45 no.2
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• pp.195-201
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• 2017

This study was conducted to evaluate the resistance of heat-treated wood using the catalyst to decay caused by fungi for sapwood and heartwood of two tree species, Korean red pine (Pinus densiflora) and Japanese larch (Larix kaempferi), respectively. Wood samples were immersed for 10 min in sulfuric acid (7.5%) and then heat-treated at $130^{\circ}C$ for 90 min. Fomitopsis palustris, a brown-rot fungus, was used to examine the decay resistance of Korean red pine and Japanese larch wood. Weight and density of wood from the all conditions increased after heat treatment using the catalyst. Weight loss after decay resistance test was also dropped with a heat treatment. The lowest weight loss indicated at heat-treated heartwood of Japanese larch. Heat treatment using the catalyst effectively increased the resistance of wood to decay caused by fungi.

• Bulletin of the Korean Chemical Society
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• v.25 no.8
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• pp.1189-1194
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• 2004

The adsorption isotherms of N2 onto the metallic silver treated activated carbon fiber samples after acid treatment are Type I with a small amount of capillary condensation hysteresis. Increasing amount of acid treatment leads to a decrease in SBETs and external surface area. But, micropore volume and average pore diameter are presented in constant regular values with increasing amount of sulfuric acid treatment. SEM observes the surface morphology and crystal grown state of metal on the fiber surface. The results of EDX of Ag-activated carbon fiber pre-treated with acid show the spectra corresponding to almost all samples rich in silver with increasing the amount of acid treated. The FT-IR spectra of Ag-activated carbon fiber show that the acid pre-treatment is consequently associated with the homogeneous dispersion of metal with the increased surface acidity of the activated carbon fiber. The type and quality of oxygen groups are determined with Boehm titration method. From the those results, a positive influence of the acidic groups on the carbon fiber surface by acid treatment is also demonstrated by an increase in the contents of metallic silver with increasing of acidic groups.

• Analytical Science and Technology
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• v.30 no.4
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• pp.205-212
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• 2017

Rice endosperm, the portion that remains after milling, is the part of the rice seed that is primarily consumed as a source of nutrients. There have been many studies on polysaccharides, such as hemicellulose, cellulose, and pectins, derived from the cell walls of various plant groups. It has been reported that the acidic polysaccharide fractions, which contain water-soluble pectins that have been shown to have pharmacological effects in vivo and in vitro, have common chemical structures that include galacturonic acid polymers, rhamnose, arabinose, and galactose. However, few studies have been conducted on the acidic polysaccharides contained in the endosperm of rice. In this study, we quantitatively compared the differences in the acidic polysaccharide contents from samples from two of the main varieties of rice consumed as staple foods, japonica and indica, using a colorimetric method. Rice samples were collected from 39 different regions in Korea, China, Thailand and Vietnam. Acidic polysaccharide fractions were obtained by precipitation of the alcohol-insoluble residue (AIR) and enzyme treatment of each sample. The total amount of carbohydrates and uronic acid in each acidic polysaccharide fraction were measured using the phenol-sulfuric acid method and the carbazole-sulfuric acid method, respectively. The differences in the total polysaccharide contents in the acidic polysaccharide fractions were not statistically significant (p = 0.07), but the uronic acid contents were significantly different between the two groups (p = 0.04).

• Applied Biological Chemistry
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• v.37 no.5
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• pp.315-319
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• 1994

Use of a solid superacid (Nafion) in hydrolysis of rice straw was investigated focusing on the fermentability of the hydrolyzates by Pichia stipitis CBS 5776. Comparisons were made with the hydrolyzates produced by a conventional method of sulfuric acid treatment. The Nafion-catalyzed hydrolyzates of rice straw exhibited low level of inhibition for both cell growth and fermentation in comparison to the hydrolyzates produced by sulfuric acid. Pichia stipitis cells were able to produce ethanol by fermentation of Nafion-catalyzed hydrolyzates when the inoculum level exceeded 3.2 g dry cells/l.

• Journal of Electrochemical Science and Technology
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• v.12 no.3
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• pp.297-301
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• 2021

Microbial fuel cells (MFCs) convert chemical energy to electrical energy via electrochemically active microorganisms. The interactions between microbes and the surface of a carbon electrode play a vital role in capturing the respiratory electrons from bacteria. Therefore, improvements in the electrochemical and physicochemical properties of carbon materials are essential for increasing performance. In this study, a microwave and sulfuric acid treatment was used to modify the surface structure of graphite granules. The prepared expandable graphite granules (EGG) exhibited a 1.5 times higher power density than the unmodified graphite granules (1400 vs. 900 mW/m³). Scanning electron microscopy and Fourier transform infrared spectroscopy revealed improved physical and chemical characteristics of the EGG surface. These results suggest that physical and chemical surface modification using sulfuric acid and microwave heating improves the performance of electrode-based bioprocesses, such as MFCs.