Papers by Author: Jei Won Yeon

Abstract: In this study, we modified the surface of nanoporous carbons with carboxymethylated polyethyleneimine (CM-PEI) of a high charge density in order to increase the Pt loading on the nanoporous carbons in an aqueous solution. We carried out equilibrium adsorption tests of Pt(IV) on the pure nanoporous carbon and the CM-PEI-coated carbons and evaluated the adsorption isotherm on the CM-PEI-coated carbon using various isotherm models. It was found that the adsorption of Pt(IV) onto the CM-PEI-coated carbons obeys the Langmuir isotherm model.

Abstract: In the present work, TiO2 and Ag-TiO2 catalysts were prepared by an ultrasonic assisted sol-gel method. The physico-chemical characteristics studies of the newly synthesized catalysts were carried out by XRD, TEM, EDX, XPS, UV-Visible absorption spectra and an optical ellipsometry. In order to find out the optical absorption properties of the catalysts, theoretical simulations have been carried out by using the Tauc-Lorentz oscillator model. Photodegradation and mineralisation of the chlorophenols were confirmed by the HPLC and TOC measurements. The rate of a mineralisation trend was observed in the order of P < 2-CP < 2,4-DCP < 2,6-DCP < 4-CP < 2,4,6-TCP by using the Ag-TiO2 catalyst. The concentration of the main aromatic intermediate products was considerably lower for the Ag-TiO2 photocatalysts than for pure TiO2. This experiment demonstrated that the presence of Ag on TiO2 catalysts could enhance the photocatalytic oxidation of chlorophenols in an aqueous suspension. It was found that the degradation of the chlorphenols by these catalysts followed the pseudo- first order kinetic model.

Abstract: The condition of a heat transfer surface with boiling is composed of three environmental components; high temperature, high pressure and water vapor. In general an autoclave or a high temperature loop system is used for maintaining the required condition. The thermodynamic relationship of chemical reactions states that the free energy difference (ΔG) is clearly dependent on the reaction temperature and independent of the reaction pressure if the reaction has no volume change: (∂ΔG/∂P)T = ΔV ~ 0. Based on the above relationship, the high-pressure term was removed from the environmental components of the heat transfer surface. A vacuum quartz capsule with a moisturized metal oxide powder was used to study the formation of nickel ferrite. The feasibility of this simplified method to simulate a heat transfer surface was confirmed by an analysis of the FT-IR spectra and XRD pattern during the transformation of a nickel and iron mixed oxide into nickel ferrite.

Abstract: We present the preparation and Cu(II) adsorption characteristics of a new and innovative composite which was composed of a carboxymethylated polyethyleneimine (CM-PEI) and an activated carbon with a nanopore less than 2 nm in diameter. In this study, we examined the adsorption phenomena of Cu(II) on the CM-PEI/F400 composite and evaluated the adsorption data using three kinds of isotherm models (Langmuir, Freundlich, and Temkin isotherms). It was found that the adsorption of Cu(II) on the CM-PEI/F400 composite obeys the Langmuir isotherm model. Furthermore, The Cu element mapping results showed that Cu was well distributed throughout all the surface of the composite particle, suggesting that the surface of the F400 particle was uniformly covered with CM-PEI.

Abstract: We applied a polymer-based surface modification technique to the surface treatment of a microporous activated carbon. We used a new chelating polymer, carboxymethylated polyethyleneimine (CM-PEI), as a functional polymer to modify the carbon surface. In this study, we examined the adsorption phenomena of the CM-PEI on an activated carbon with a nanopore less than 2 nm in diameter and evaluated the adsorption mechanism using three kinds of models; Langmuir, Freundlich, and Redlich-Peterson isotherm. It was found that the adsorption of CM-PEI on the F400 follows the Freundlich isotherm model. Furthermore, desorption experiments of the CM-PEI were carried out to examine the stability of the CM-PEI adsorption on the F400 and to estimate the applicability of the CM-PEI-coated F400 to the adsorbents. It was observed that most of the CM-PEI remains on the F400 for 7 days in the pH range of 3 to 7. Especially, the adsorption amount of CM-PEI on the F400 did not change after 3 days at the pH range of 5 to 7, indicating that the CM-PEI strongly adheres to the F400.