Kwinam Park

Removal characteristics of trace compounds of landfill gas by activated carbon adsorption.

The removal characteristics of trace compounds and moisture in raw landfill gas (LFG) were studied. The LFG from the extraction well was saturated with water and moisture was eliminated by physical methods including cyclone-type dehydrator and compressor. The moisture removal efficiency of dehydrator and compressor was above 80%. As the moisture contents of LFG decreased, the toxic compounds like aromatics and chlorinated compounds were effectively removed by using the granular activated carbon. The breakthrough time and adsorption capacity of benzene, toluene, and ethyl benzene decreased rapidly when the relative humidity is over 60%. The effect of moisture was more pronounced at lower adsorbate concentrations tested than at higher concentrations. The breakthrough curves for multi-component mixtures show displacement effects. In the course of competing adsorption, adsorbates with strong interaction force to displace weakly bounded substances. Adsorption by activated carbon is in descending order of xylene, ethylbenzene, toluene, tri or tetrachloroethylene, benzene, carbon tetrachloride and chloroform in LFG, respectively.

Saccharification and adsorption characteristics of modified cellulases with hydrophilic/hydrophobic copolymers.

Saccharification and adsorption characteristics of native and modified cellulases were investigated. Copolymers, containing polyoxyalkylene and maleic anhydride (MA) were used to modify cellulase. Amino groups of the cellulase were covalently coupled with the MA. As the degree of modification (DM) increased, the activity of modified cellulase slightly decreased. At the maximum DM, the modified cellulase activity retained more than 75% of the unmodified native cellulase activity. In saccharification, native cellulase rapidly adsorbed onto the substrate at initial reaction time. Native cellulase adsorbed tightly onto the substrate surface and did not desorb as reaction time proceeded. The strong adsorption of cellulase onto the substrate can, however, be controlled by the modification. As the hydrophilicity of modified cellulase increased, free modified enzyme concentration also increased. As a result, the conversion rate of modified cellulase was higher than the native one.

Characteristics of LDPE pyrolysis

Pyrolysis of low-density polyethylene (LDPE) was studied in order to relieve environmental pollution and recover the monomer or fuel. LDPE was thermally decomposed with and without catalyst. First, efficiency of oil production was analyzed according to the variation of reaction conditions such as reaction temperature, types of additives and catalyst, and contacting method. In non-catalytic LDPE pyrolysis, isothermal reaction was almost similar to non-isothermal reaction. Light oil was produced with low reaction temperature (430 °C) in the isothermal reaction, but low heating rate caused light oil production in the non-isothermal reaction. When pyrolyzed polyethylene (PE oil) was applied as an additive, no significant effect showed in the isothermal reaction. In catalytic LDPE pyrolysis (10%NiO/S-A) with additives, efficiency greatly increased especially with polystyrene (PS) addition. It was also found that the molecular weight distribution of product oil could be controlled by applying different additives. When a catalytic reactor was used, the amount of the low molecular weight compound increased as flow rate of thermally decomposed gas was lowered.

Improvement of the physical properties of reprocessed paper by using biological treatment with modified cellulase

A primary need for waste paper reprocessing is to preserve optical properties and the physical strength of the paper fibers. In this study, modified cellulase with copolymer, polyethylene oxide (PEO) derivatives and maleic anhydride (MA) was applied to the reprocessing of mixed office waste (MOW). Modified cellulase was prepared by a chemical reaction between amino groups of the cellulase and the MA functional groups of the copolymer. In MOW reprocessing, modified cellulase improved several physical properties of the paper including freeness, optical properties, and physical strength compared to the conventional process. Even though native cellulase improved the physical properties, paper treated with modified cellulase exhibited an increase in physical properties such as tensile strength and internal bond over those of unmodified cellulase. From these results, modified cellulase method is a new biological treatment that will save pulp resources, which are added to waste paper reprocessing to maintain the strength of paper.

Three-dimensional architectural and structural analysis—a transition in concept and design from Delaire's cephalometric analysis

The aim of this study was to present a systematic sequence for three-dimensional (3D) measurement and cephalometry, provide the norm data for computed tomography-based 3D architectural and structural cephalometric analysis, and validate the 3D data through comparison with Delaires two-dimensional (2D) lateral cephalometric data for the same Korean adults. 2D and 3D cephalometric analyses were performed for 27 healthy subjects and the measurements of both analyses were then individually and comparatively analyzed. Essential diagnostic tools for 3D cephalometry with modified definitions of the points, planes, and measurements were set up based on a review of the conceptual differences between two and three dimensions. Some 2D and 3D analysis results were similar, though significant differences were found with regard to craniofacial angle (C1-F1), incisal axis angles, cranial base length (C2), and cranial height (C3). The discrepancy in C2 and C3 appeared to be directly related to the magnification of 2D cephalometric images. Considering measurement discrepancies between 2D and 3D Delaires analyses due to differences in concept and design, 3D architectural and structural analysis needs to be conducted based on norms and a sound 3D basis for the sake of its accurate application and widespread adoption.

Biological Reprocessing of Mixed Office Waste (MOW) Using Modified Cellulase by Production of Functional Copolymer

Copolymer containing functional groups such as polyethylene oxide (PEO) and maleic anhydride (MA) was synthesized to modify the cellulase. MA was attached to PEO allyl ester, which was the product of the reaction between PEO allyl alcohol and lauric acid. The number of ethylene oxide (EO) units in one PEO chain was varied from 10 to 40. MA groups of the copolymer formed the chemical bond with the amino acid groups of the cellulase in the modification reaction. When cellulase was modified with synthesized copolymer, modified enzyme showed high relative activity regardless of high degree of modification compared with other modification methods. In mixed office waste reprocessing, modified cellulase improved many physical properties of the paper including freeness, optical properties, and strengths compared to the conventional process. Even though native cellulase improved the physical properties, modified cellulase showed an increased tensile strength and internal bond over those of unmodified cellulase. From these results, modified cellulase method is an effective biological treatment that would save pulp resources in the reprocessing.

Modification of lipase fromCandida rugosa with poly(ethylene oxide-co-maleic anhydride) and its separation using aqueous two-phase partition system

A copolymer was synthesized from polyethylene oxide (PEO) and maleic acid anhydride (MA). Number of ethylene oxide units was varied from 10 to 40. Lipase fromCandida rugosa was modified through chemical bonding of MA with amino group of lipase. Degree of modification increased with a decrease in EO unit and increase in copolymer/ enzyme ratio. The relative activity of modified enzyme increased with increase in EO unit. It was more than native lipase (100%) when copolymer/enzyme weight ratio was less than 3 for all copolymers. It might be due the conformation change of the lipase molecules on modification that would have exposed the catalytic sites making them more easily accessible. At the highest DM (39%), modified lipase retained more than 50% relative activity. Partitioning of native and modified lipase was also studied by using aqueous two phase synthesized copolymer/dextran system: modified lipase (with EO 30 and 40) showed better separation than the native one. Partition coefficient increased with increase in copolymer/enzyme weight ratio.