Choong-Lyeal Choi

Adsorption of Divalent Cationic Herbicides from Aqueous Solution by FA-zeolite A and X

The purpose of this study is to elucidate the adsorption properties of fly ash (FA)-derived zeolites A and X for the divalent cationic herbicides, paraquat and diquat. Their adsorption isotherms were well fitted to the Langmuir equation, indicating that adsorption mainly occurred on the crystal surface. FA-zeolite X showed a higher adsorption capacity than that of FA-zeolite A due to wide pore window size in spite of its low CEC. The equilibrium adsorption increased with increasing the reaction temperature because of the enhanced molecule activity and the thermal expansion of zeolite pore windows. Overall, these results demonstrated that the FA-zeolite synthesized from fly ash could be used as a low-cost mineral adsorbent for the removal of environmental cationic organic pollutants from the aqueous solution.

Degradation of Chlorothalonil by Zerovalent Iron-Montmorillonite Complex

Zerovalent iron (ZVI) has been recently used for environmental remediation of soils and groundwaters contaminated by chlorinated organic compounds. As a new approach to improve its reductive activity and stability, zerovalent iron-montmorillonites (ZVI-Mt) complex are synthesized by simple process. Therefore, this study was carried out to elucidate the characteristics of ZVI-Mt complex and to investigate degradation effects of fungicide chlorothalonil. The XRD patterns of ZVI-Mt complex showed distinctive peaks of ZVI and montmorillonite. In ZVI-Mt complex, the oval particles of ZVI were partly surrounded by montmorillonite layers that could prevent ZVI surface oxidation by air. The degradation ratio of chlorothalonil after 60 min exhibited 71% by ZVI and 100% by ZVI-Mt complex. ZVI-Mt21 complex exhibited much higher and faster degradation ratio of chlorothalonil compare to that of ZVI or ZVI-Mt11 complex. Also, degradation rate of chlorothalonil was increased with increasing ZVI or ZVI-Mt complex content and with decreasing initial solution pH.

Degradation of the Chlorothalonil by Functional Zeolite-KCIO 3 Complex

Salt occlusion in Zeolite is a unique phenomenon that takes place only when the salt size is similar to the window size of host zeolite. -occluded Zeolite, as an environment-friendly oxidant, has a high potential for effective removal of various organic pollutants. This study was carried to investigate the characteristics and the removal kinetics of fungicide chlorothalonil by zeolite- complex. About 10% of was occluded in zeolite pores synthesized by salt-thermal method from fly ash, although the occlusion amount was relatively less compared to that of nitrate salts. By occlusion with , no remarkable changes were found in X-ray diffraction patterns of cancrinite, whereas some decrease of overall peak intensities was found with those of sodalite. Different releasing kinetics of ion were observed in distilled water and soil solution from zeolite- complex. Two reactions, hydration and diffusion, seem to be related with the release of . Therefore, the release isotherm of ion well fitted to the power function model which indicate the release was made by hydration and diffusion. The removal of chlorothalonil by zeolite and reached at reaction equilibrium within 6 hours by 18% and 47% respectively. However, the chlorothalonil removal by the zeolite- complex increased slowly and steadily up to 92% in 96 hours. These findings suggested that zeolite- complex could be applied for effective removal of organic contaminants in the soil and aqueous environment.

Photocatalytic Degradation of Fungicide Chlorothalonil by Mesoporous Titanium Oxo-Phosphate

Titanium mesoporous materials have received increasing attention as a new photocatalyst in the field for photocatalytic degradation of organic compounds. The photocatalytic degradation of chlorothalonil by mesoporous titanium oxo-phoswhate (Ti-MCM) was investigated in aqueous suspension for comparison with , (Degussa, P25) using as an effective photocatalyst of organic pollutants. Mesoporous form of titanium Phosphate has been prepared by reaction of sulfuric acid and titanium isopropoxide in the presence or n-hexadecyltrimethylammonium bromide. The XRD patterns of Ti-MCM are hexagonal phases with d-spacings of 4.1 nm. Its adsorption isotherm for chlorothalonil reached at reaction equilibrium within 60 min under dark condition with 28% degradation efficiency. The degradation ratio of chlorothalonil after 9 hours under the UV radiation condition (254 nm) exhibited 100% by Ti-MCM and 88% by . However, these degradation kinetics in static state showed a slow tendency compared to that of stirred state because of a low contact between titanium matrices and chlorothalonil. Also, degradation efficiency of chlorothalonil was increased with decreasing initial concentration and with increasing pH of solution. As results of this study, it was clear that mesoporous titanium oxo-phosphate with high surface area and crystallinity could be used to photo- catalytic degradation of various organic pollutants.