2 (Langmuir, Freundlich, Elovich, Temkin, and Dubinin-Radushkevich) and 3 (Sips and Redlich-Peterson)-parameter isotherm models were applied to evaluated for the applicability of adsorption of Cu(II) and/or phosphate isotherm using chitosan bead. Non-linear and linear isotherm adsorption were also compared on each parameter with coefficient of determination (R2). Among 2-parameter isotherms, non-linear Langmuir and Freundlich isotherm showed relatively higher R2 and appropriate maximum uptake (qm) than other isotherm equation although linear Dubinin-Radushkevich obtained highest R2. 3-parameter isotherm model demonstrated more reasonable and accuracy results than 2-parmeter isotherm in both non-linear and linear due to the addition of one parameter. The linearization for all of isotherm equation did not increase the applicability of adsorption models when error experiment data was included.

The gas adsorption isotherm requires accurate measurement for the analysis of porous materials and is used as an index of surface area, pore distribution, and adsorption amount of gas. Basically, adsorption isotherms of porous materials are measured conventionally at 77K and 87K using liquid nitrogen and liquid argon. The cold volume calibration in this conventional method is done simply by splitting a sample cell into two zones (cold and warm volumes) by controlling the level sensor in a Dewar filled with liquid nitrogen or argon. As a result, BET measurement for textural properties is mainly limited to liquefied gases (i.e. N2 or Ar) at atmospheric pressure. In order to independently investigate other gases (e.g. hydrogen isotopes) at cryogenic temperature, a novel temperature control system in the sample cell is required, and consequently cold volume calibration at various temperatures becomes more important. In this study, a cryocooler system is installed in a commercially available BET device to control the sample cell temperature, and the automated cold volume calibration method of temperature variation is introduced. This developed calibration method presents a reliable and reproducible method of cryogenic measurement for hydrogen isotope separation in porous materials, and also provides large flexibility for evaluating various other gases at various temperature.

We study and describe-from the point of view of the interactions of the adsorbed particles-three types of the adsorption isotherms, namely, Langmuir type adsorption isotherms, phase transition type adsorption isotherms, and adsorption limited type adsorption isotherms, which are observed by experiments. By introducing and using a one dimensional statistical occupancy model, we derived analytical adsorption isotherms for the no force, the attractive force, and the repulsive force exerted on the other adsorbed particles. Our derived adsorption isotherms qualitatively pretty well agree with the experimental results of the adsorption isotherms. To specify each adsorption type, Langmuir type adsorption is a phenomenon that occurs with no forces between the adsorbed particles, phase transition type adsorption is a phenomenon that occurs with the strong attractive forces between the adsorbed particles, and adsorption limited type adsorption is a phenomenon that occurs with the repulsive forces between the adsorbed particles. The theoretical analysis-only using fundamental thermodynamics and occupancy statistics though-qualitatively quite well explains the experimental results.

In order to capture the indoor CO₂ gas from public indoor spaces, a commercial zeolite(4A) was modified with alkali metals useful for adsorption. The prepared sorbents showed somewhat improved adsorption capacity. A few isotherm models were reviewed to characterize the adsorption mechanism of test sorbents. Sips model was found the most appropriate for low level indoor CO₂ adsorption, but revealed a significant error in low pressure regimes and required numerical analysis for quantitative evaluation. Thus, a parameter(qm) in the equation was empirically recorrelated with a operation temperature. As a result, the final model equation including a simple linear function presented less errors for evaluation of the potential capacity of adsorption.

Zeolite material having XRD peaks of Na-A zeolite in the 2θ range of 7.18 to 34.18 can be synthesized from the waste catalyst using a fusion/hydrothermal method. The adsorption rate of Mn ions by a commercial Na-A zeolite and the synthesized zeolitic material increased as the adsorption temperature increased in the range of 10 ~ 40℃. The adsorption of Mn ion were very rapid in the first 30 min and then reached to the equilibrium state after approximately 60 min. The adsorption kinetics of Mn ions by the commercial Na-A zeolite and the zeolitic material were found to be well fitted to the pseudo-2nd order kinetic model. Equilibrium data by the commercial Na-A zeolite and the zeolitic material fit the Langmuir, Koble-Corrigan, and Redlich-Peterson isotherm models well rather than Freundlich isotherm model. The removal capacity of the Mn ions by the commercial Na-A zeolite and the zeolitic material obtained from the Langmuir model was 135.2 mg/g and 128.9 mg/g at 30℃, respectively. The adsorption capacity of Mn ions by the synthesized zeolitic material was almost similar to that of commercial Na-A zeolite. The synthesized zeolitic material could be applied as an economically feasible commercial adsorbent.

In this study, zeolite (Z-C2) was synthesized using a fusion/hydrothermal method on coal fly ash (FA) discharged from a thermal power plant in the Ulsan area and then analyzed via scanning electron microscopy (SEM) and X-ray diffraction (XRD). The Z-C2 was characterized in terms of mineralogical composition and morphological analysis. The XRD results showed that its peaks had the characteristics of Na-A zeolite in the range of 2θ of 7.18~34.18. The SEM images confirmed that the Na-A zeolite crystals had a chamfered-edge crystal structure almost identical to that of the commercial zeolite. The adsorption kinetics of Cu, Co, Mn and Zn ions by Z-C2 were described better by the pseudo-second-order kinetic model more than by the pseudo-first-order kinetic model. The Langmuir model fitted the adsorption isotherm data better than the Freundlich model did. The maximum adsorption capacities of Cu, Co, Mn and Zn ions obtained from the Langmuir model were in the following order : Cu (94.7 mg/g) > Co (77.7 mg/g) > Mn (57.6 mg/g) > Zn (51.1 mg/g). These adsorption capacities are regarded as excellent compared to those of commercial zeolite.

The adsorption characteristics of Sr ions and Cs ions in single and binary solution by zeolite A were investigated in batch experiment. The adsorption rate of Sr ions and Cs ions by zeolite A obeyed pseudo-second-order kinetic model in single and binary solution. The initial adsorption rates (h) and adsorption capacities of both ions obtained from pseudo-second-order kinetic model, and the values were decreased with increasing concentration of the competitive ions (0~1.5 mM). Also, adsorption isotherm data in binary solution were well fitted to the extended Langmuir model, the maximum adsorption capacities of Sr and Cs calculated from the model were 1.78 mmol/g and 1.64 mmol/g, respectively. The adsorption of Sr and Cs ions by zeolite A was carried out in the presence of other cations such as Na+, K+, Mg2+, and Ca2+. The results showed that the zeolite A can maintain a relatively high adsorption capacity for Sr and Cs ions and exhibits a high selectivity in the presence of competitive cations. The effect of competition had an order of Ca2+>K+>Mg2+>Na+ for Sr ions and K+>Ca2+>Na+>Mg2+ for Cs ions at the same cation concentration.

본 연구에서는 세계적으로 문제가 되고 있는 하천 및 수계내의 중금속 오염 방지와 대책을 강구하기 위해 고로슬래그가 중금속흡착에 유리한 물리, 화학적 특성을 지녔다고 판단하여 흡착제로서의 중금속흡착능이 충분한지에 대해 검토하였다. 흔히 중금속흡착제로 알려진 활성탄의 경우 제거효율은 좋지만, 경제적인 부담감을 안고 있으며, 현재 최근 활발한 산업 활동으로 인하여 나오는 건설폐기물이나 산업부산물의 문제를 해결하기 위해 이를 이용한 중금속 제거 기술이 보고되고 있다. 특히, 고로슬래그의 경우 선철 1t당 0.5~1t정도의 양이 배출되며, 이에 고로슬래그의 흡착제로서의 사용 검토가 된다면 제철부산물의 처리와 하천 및 수계내의 수질개선에도 도움이 된다고 판단했다. 고로슬래그는 체가름시험을 통하여 1.2~2.5mm의 치수를 사용하였으며, 중금속은 Cd, Cu, Pb, Zn으로 선정하여 등온흡착실험을 진행하였다. 중금속의 초기농도는 1ppm, 2ppm, 5ppm로 설정하고 120분간 128rpm으로 교반하여 진행하였으며, 일정 시간간격을 두어 샘플을 채취하여 시간 당 중금속의 부하량을 산정하였다. 그 결과 Cd의 경우 120분간 선형의 그래프를 나타내며 제거 되었으며, Cu, Pb, Zn은 20~30분까지 급격하게 중금속의 농도가 감소하다가 120분까지 서서히 감소되었다. 초기농도에 관계없이 120분동안 중금속 제거량은 총 1ppm 정도였으며, 결과적으로 고로슬래그의 중금속 흡착제로서의 흡착능이 뛰어나다고 판단된다. 이를 통해 하천 및 수계내의 수질개선을 위한 비점오염저감시설이나 장치의 흡착제나 또는 여과저류지등의 여재로 이용할 수 있을 것으로 기대된다.