수열반응에 의한 석탄회로부터 제올라이트(K-Chabazite)의 생성기작 및 물질특성 규명
Formation and Characterization of K-Chabazite from Coal Fly Ash by Hydrothermal Reaction
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In this study, the formation and physicochemical properties – such as the cation exchange capacity (CEC) and crystalline phases – of zeolite produced from coal fly ash (CFA) by the alkali hydrothermal reaction were investigated by performing XRD and SEM analyses. The hydrothermal reaction was carried out using alkali solutions with various KOH concentrations (M), liquid/solid ratio (L/S ratio; L/kg), and reaction times at a constant temperature (100°C). The results show that K-Chabazite (ca 40%) with CEC values of 220~240 meq/100 g was obtained at 3~4 M KOH concentration, 5~10 L/S ratio, and >48 h reaction time. The three steps in the alkali hydrothermal reaction for K-Chabazite formation – namely, the dissolution of Al and Si ions in CFA, condensation of the ions, and crystallization – were analyzed on the basis of the reaction time. The adsorption capacity (% removal) of the zeolite product for the removal of mixed heavy metals (Cu, Cd, Cr, and Pb; each at a concentration of 100 mg/L at pH 5.0) in a solution was also evaluated, and the efficacy of the zeolite product as an adsorbent was discussed.
Abstract
In this study, the formation and physicochemical properties – such as the cation exchange capacity (CEC) and crystalline phases – of zeolite produced from coal fly ash (CFA) by the alkali hydrothermal reaction were investigated by performing XRD and SEM analyses. The hydrothermal reaction was carried out using alkali solutions with various KOH concentrations (M), liquid/solid ratio (L/S ratio; L/kg), and reaction times at a constant temperature (100°C). The results show that K-Chabazite (ca 40%) with CEC values of 220~240 meq/100 g was obtained at 3~4 M KOH concentration, 5~10 L/S ratio, and >48 h reaction time. The three steps in the alkali hydrothermal reaction for K-Chabazite formation – namely, the dissolution of Al and Si ions in CFA, condensation of the ions, and crystallization – were analyzed on the basis of the reaction time. The adsorption capacity (% removal) of the zeolite product for the removal of mixed heavy metals (Cu, Cd, Cr, and Pb; each at a concentration of 100 mg/L at pH 5.0) in a solution was also evaluated, and the efficacy of the zeolite product as an adsorbent was discussed.
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