Chang-Han Lee

Breakthrough analysis of carbon dioxide adsorption on zeolite synthesized from fly ash

Zeolite (FAZ) was synthesized by the fusion method using coal fly ash to adsorb carbon dioxide. The experimental adsorption was operated batchwise in a laboratory-scale packed-bed adsorber to obtain the breakthrough curves of CO2 under conditions such as adsorption temperatures (20–80 °C), flow rates of gaseous mixture of carbon dioxide and nitrogen (40–100 cm3/min), and concentration of CO2 (3000–10000 ppmv) at atmospheric pressure of 101.3 kPa. The influence of the experimental conditions, such as the gas flow rate, concentration of CO2 and adsorption temperature on adsorption behavior, was discussed. The deactivation model, combined the adsorption with the deactivation of adsorbent, was used to analyze the physicochemical properties, such as the adsorption kinetics, capacity and heat of adsorption, by fitting the experimental data of the breakthrough curves to this model. The adsorptive activity and capacity of FAZ were as almost same as those of the commercial zeolite of Wako 4A.

Control of properties of PLA-PFPE-PLA triblock copolymers using stereocomplex between l-LA and d-LA sequences

ABSTRACT Two type of triblock copolymers [poly(l-lactide)-b-perfluoro polyether-b-poly(l-lactide) (fluoro l-PLA) and poly(d-lactide)-b-perfluoro polyether-b-poly(d-lactide) (fluoro d-PLA)] (fluoro PLAs) were synthesized by ring-opening polymerization. The synthesized triblock copolymers showed more hydrophobic properties than pristine l-PLA due to the perfluoro polyether (PFPE). To control the surface properties, the blends were prepared by mixing fluoro PLAs with l-PLA. The degradation rates of the fluoro PLAs/l-PLA blends were retarded due to the surface segregation of PFPE which has lower surface energy. In case of the fluoro d-PLA/l-PLA blends, however, the stereocomplex formation between the l-lactide and d-lactide sequences enhanced the thermal and enzymatic stabilities of l-PLA. As a result, the biodegradability of l-PLA can be controlled by copolymerization or the formation of a stereocomplex.

Synthesis of Na-A zeolite from Jeju Island scoria using fusion/hydrothermal method

Na-A zeolite (Z-S1) was synthesized from scoria found on Jeju Island, Korea using the fusion/hydrothermal method. The influences of NaOH/scoria ratio, SiO2/Al2O3 molar ratio, and particle sizes on the synthesis of zeolite were studied by analyzing crystals morphology and crystallinity. According to XRD analysis, it was confirmed that the zeolitic materials were synthesized in the range of NaOH/Scoria ratio from 0.6 to 2.4. As the ratio of NaOH/Scoria increased from 0.6 to 1.2, the crystallinity of Z-S1 gradually increased from 8.85% to 57.53%, then became almost constant at 61.80% as the ratio of NaOH/Scoria exceeded 1.8. The particle size of the zeolite crystals tended to decrease with increasing the alkali content of NaOH/Scoria from 0.6 to 1.8. It was possible to synthesize tine crystals having the particle size about 1.0 ㎛ or less at a NaOH/Scoria ratio of 1.8. This study has shown that the fusion/hydrothermal method is a very effective technique for synthesizing Z-S1 from scoria and provides a potential application for obtaining commercial products from natural materials.

Synthesis of β-hydroxyalkylamide by using microwave and its performance for powder coating

ABSTRACT Among the curing hardeners for powder coating, β-hydroxyalkylamide is widely used due to its easy handling, excellent exterior durability, good mixing with other chemicals, flexibility, hardness, and especially non-toxic property. In this study, β-hydroxyalkylamide which is normally produced by oil bath heating was synthesized by microwave heating system. For synthesis, it takes 300 min of reaction time for heating system of oil bath but the microwave heating requires only 100 min of reaction time because of the internal heating. Performances of products obtained by both heating systems showed very similar properties. These results suggest that the microwave as a heating source is an effective tool for the reaction of β-hydroxyalkylamide.

Preparation of nano-magnesium oxide from seawater bittern using decarboxylation/precipitation method

ABSTRACT The nanoparticles of magnesium oxide used mainly for additives were synthesized through precipitation method in the presence of precipitants. The effects of preparation parameters, such as NaOH and Ca(OH)2 concentrations, dilution rate, rotation speed on size and morphology of the nanoparticles were investigated. The magnesium oxide was produced from magnesium hydroxide in the waste-seawater bittern. The properties of the obtained nanoparticles were analyzed by XRD and SEM. The obtained magnesium oxide crystals showed a wide distribution of globular structure including sphere or cubic-like morphology. Also size and crystallinity of magnesium oxide crystals increased from 50 to 180 nm with increasing a rotation speed.