Papers by Author: Beom Goo Lee

Abstract: In this study, mine tailings obtained in a region near to Youngwol Sangdong(Korea) was used to investigate the contamination of heavy metal ions. Some amount of mine tailings and lignin(AE agent) were added in the general cement pastes, of which the compressive strength and leaching rate were investigated. X-ray fluorescence analysis shows that the major constituents of mine tailings are 56.9wt% of SiO2, 10.8wt% of Fe2O3, 11.2wt% of CaO and 11.4wt% of Al2O3, and the major phases are quartz and calcite. In the content of heavy metal ions, the concentration of As ion is the highest as 257.261mg/ℓ. When mine tailings and lignin were added in cement pastes, the compressive strength was higher in the cement pastes adding only lignin. Lignin addition significantly improved the compressive strength of cement pastes by approximately 15% when being cured in distilled water. The compressive strength was lower in the cement pastes adding mine tailings than in the cement pastes not adding. The leaching rates of Cr, Pb and As ion in distilled water were decreased in the cement pastes adding lignin, compared to in the cement pastes not adding. The leaching rates of all heavy metal ions in the cement pastes curing for 28 days were within the maximum permitted limits in KSLT and EPT method. Therefore, it is thought that mine tailings can be used as an ecological material.

Abstract: In this study lignocellulosic fibers, such as kenaf bast, kenaf core, sugar cane bagasse, cotton, coconut coir, and spruce, which are environment friendly natural materials, were tested for their ability to remove copper, nickel and zinc ions from aqueous solutions. The fibers were analyzed for Klason lignin content, water sorption capacity and dry volume. The fiber with the highest level of heavy metal removal in the separate and mixed solution was kenaf bast.. In the mixed solution kenaf bast, sugar cane bagasse and cotton removed more copper and nickel ion than in the separate solution, and the amounts of removed heavy metal ions were changed in some lignocellulosic fibers, compared to those of the separate solution. In the mixed solution heavy metal ions may compete with one another for sorption sites on the surface of lignocellusic fiber. In kenaf bast to remove heavy metal ions most, Klason lignin content was the second lowest, and water sorption and dry volume were the lowest in all tested lignocellulosic fibers. It showed that removal of heavy metal ions does not correlate with any chemical and physical factors, but may be affected by the cell wall structure of lignocellulosic fibers and how many free phenolic groups in lignin, which are considered as the heavy metal ion binding site, are exposed on the surface of fibers. Cotton, with about 1% Klason lignin, was very low in heavy metal ion removal, while all other fibers containing greater than about 10% lignin did remove heavy metal ions. It showed that even the lignin content of lignocellulosic fibers does not correlate with heavy metal ion removal but lignin does play a role in heavy metal ion removal.

Abstract: Kenaf core was tested for its ability to sorb diesel oil from the pure diesel oil bath and the diesel oil containing water bath after extracting with diethyl ether to remove wax from fiber surface, grinding to disrupt lumen structure and presoaking in water. Oil sorption capacity was the highest as 8.0 g/g in diethyl ether extracted fiber in oil bath, and the lowest as 1.3 g/g in water soaked kenaf core in water bath. Diesel oil sorption capacity was much higher in oil bath than in water bath. In diethyl ether extraction the diesel oil sorption capacity was not changed much in kenaf core, compared to that of control. Also, even after grinding and passing through 20 mesh screen (0.86mm) the diesel oil sorption capacity was almost same. When kenaf core was presoaked in water the oil sorption capacity was decreased to about half of control as 1.3g/g in water bath. Grinding, extracting and water presoaking all contributed to the changes in oil sorption capacity. The results show that if in lignocelluloscic fiber like kenaf core the fiber structure is not disrupted during processing and the intact lumen structure can be kept, the oil sorption capacity may not be affected much by physical and chemical changes.

Abstract: Cotton, a lignocellulosic fiber and environment friendly natural material, was tested for its ability to sorb diesel oil from the pure diesel oil bath and the diesel oil containing water bath. The fiber was ground to disrupt the lumen structure or extracted with diethyl ether to remove wax from cotton. Diethyl ether is an organic solvent and extracts only extractives in the cell wall. Oil sorption capacity was the highest in control as 30.6 g/g in the pure diesel oil bath, and the lowest in ground cotton as 0.8 g/g in the diesel oil containing water bath. Cotton is mainly composed of hydrophilic components and sorb water more easily than oil. As a result diesel oil sorption capacity was much higher in the oil bath than in the water bath. However, after grinding and passing through 20 mesh screen (0.86 cm), wax is preserved but the lumen structure of cotton, of which the fiber length is about 18 mm, is disrupted by grinding and can not hold oil. Therefore, the diesel oil sorption capacity of cotton was decreased significantly to 5.2 g/g in the pure diesel oil bath, and to 0.8 g/g in the water bath, compared to those of control. And because wax is removed but lumen structure is not destroyed after diethyl ether extraction, the diesel oil sorption capacity decreased slightly to 27.7 g/g in the oil bath and to 7.5 g/g in the water. When cotton was presoaked in water, cotton sank during the presoaking process, and so the oil sorption capacity could not be determined. Grinding, extractingand presoaking all contributed to the changes in oil sorption capacity. The most significant change is attributed to the reduction in the particle size of cotton.

Abstract: It is investigated whether ginseng can be milled into super fine powder below 50μm, changing the circumferential velocity of impeller of a turbo mill(100, 110 and 120m/s). The mean particle size is 113.3μm in control but is decreased abruptly into 11.9μm at 120m/s. The largest particle diameter at 97% of volume distribution is reduced into below 32μm at 120m/s from below 725μm at control. The particle size distribution between d(0.1) and d(0.9) is 334μm at control, but is decreased into less than 26μm in all conditions after milling. It shows that ginseng can be milled into super fine powder by the turbo mill, which has the narrow particle size distribution.

Abstract: Kenaf bast, coconut coir, and cotton, which are lignocellulosic fibers and environment friendly natural materials, were tested for their ability to remove copper, nickel, and zinc ions from aqueous solutions according to their physical and chemical changes by solvent extraction. The order of the lignin and xylose content in unextracted fibers is coconut coir>kenaf bast>cotton. The fiber with the highest level of heavy metal removal, however, was kenaft bast. It showed that removal of heavy metals does not correlate with lignin and xylose content. Cotton, with about 1.1% lignin and 0.3% xylose, was very low in heavy metal ion sorption while other two fibers containing lignin and xylose did remove heavy metal ions. It indicates that lignin and xylose play a role in heavy metal ion sorption. Extraction with the various solvents removed different cell wall components and changed the cell wall structure, and thus did change the heavy metal ions removal capacity of lignocellulosic fibers.

Abstract: This study investigates the influence of viscoelastic properties of a series of ethylene-vinyl acetate copolymer on impact noise and vibration damping of wood/polymer/wood sandwich composites. It was found that the impact noise and vibration damping of composites are very sensitive to the state of molecular motion of polymer. The noise and vibration damping of composites was better when the polymer was in the glass transition state (vinyl acetate 55~75%) at the test-temperature, and it was worse when the polymer was in rubbery state (vinyl acetate 47~20%) or in glassy state (vinyl acetate100~87%). The impact noise decreased by about 6-12dB when the glass transition state of polymer was sandwiched between wood panels.

Abstract: Kenaf bast, which is lignocellulosic fiber and environment friendly natural material, was tested for its ability to remove copper, nickel and zinc ions from aqueous solutions. The fiber was analyzed for xylose, lignin content, weight loss and dry volume, and extracted with diethyl ether, ethyl alcohol, hot water, or 1% sodium hydroxide to change physical and chemical characteristics of keanf bast. Diethyl ether and ethyl alcohol are organic solvents, which extract only extractives in the cell wall. The weight losses are less than 4.1%, the dry volumes increase up to 0.68 cm3/g, and the changes of lignin content are less than 0.6%. The differences of the heavy metal ions removal capacities are less than 0.05 mg/g, compared to those of control. Hot water and 1% sodium hydroxide remove cell wall components as well as extractives in the cell wall. In addition, during the extraction process the cell wall is swollen by the delamination of cell wall layers, xylose and lignin are exposed. The weight losses increases up to 24.0%, the dry volumes increase up to 1.20 cm3/g, and the changes of lignin content are less than 0.6%. The difference of the heavy metal ions removal capacities of kenaf bast increase up to 0.14 mg/g, and are much higher than those of diethyl ether and ethyl alcohol. The above results show that to increase the heavy metal ions removal capacities, the extraction chemicals may swell the cell wall more than water does and remove the cell wall components as well as extractives to change cell wall chemistry and architecture.