• Korean Chemical Engineering Research
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• 제58권4호
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• pp.624-634
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• 2020

The ability of natural and modified clay to adsorb phenol was studied. The clay samples were analyzed by different technical instruments, such as X-ray fluorescence (XRF), X-ray diffraction (XRD) and FT-IR spectroscopy. Surface area, pore volume and average pore diameter were also determined using B.E.T method. Up to 73 and 99% of phenol was successfully adsorbed by natural and activated clay, respectively, from the aqueous solution. The experiments carried out show that the time required to reach the equilibrium of phenol adsorption on all the samples is very close to 60 min. The amount of phenol adsorbed shows a declining trend with higher pH as well as with lower pH, with most extreme elimination of phenol at pH 4. The adsorption of phenol increases proportionally with the initial phenol concentration. The maximum adsorption capacity at 25 ℃ and pH 4 was 29.661 mg/g for modified clay (NaMt). However, the effect of temperature on phenol adsorption was not significant. The simple modification causes the formation of smaller pores in the solid particles, resulting in a higher surface area of NaMt. The equilibrium results in aqueous systems were well fitted by the Freundlich isotherm equation (R² > 0.98). Kinetic studies showed that the adsorption process is best described by the pseudo-second-order kinetics (R² > 0.99). The adsorption of phenol on natural and modified clay was spontaneous and exothermal.

• 대한토목학회논문집
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• 제13권2호
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• pp.279-285
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• 1993

여러 오염물질 사이의 흡착 경쟁, 평형, 물질확산의 상호 연관성을 이해하는 것은 효율적인 활성탄 흡착탑 설계 및 운전을 위하여 중요하다. 흡착탑내에서의 오염물질의 확산 및 흡착 현상을 동역학적 및 수학적으로 예측하기 위하여 "Micro-Diameter-Depth Adsorption System" Technique을 개발하여 평형 및 물질확산 계수들을 측정하였다. 활성탄 입자의 외부 "Film Transfer"와 입자 내부에서의 "Surface Diffusion"을 고려한 오염 물질 사이의 흡착경쟁, 탈착, Chromatographic Displacement Effect 등을 Homogeneous Surface Diffusion Model(HSDM)을 이용하여 예측했다. p-Chlorophenol(PCP)/p-Nitrophenol(PNP)의 Breakthrough Curve에서 PCP는 PNP에 의해 Displace되는 현상을 볼 수 있었으며 HSDM은 이를 잘 예측하였다. Dodecylbenzenesulfonate (DBS)는 흡착된 DBS의 일부분이 비가역적 흡착반응을 보인다는 가정하에서 HSDM에 의해 잘 예측될 수 있었다.

• Advances in environmental research
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• 제6권1호
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• pp.1-14
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• 2017

New technologies or improvement of the existing technologies are required to enhance the efficiency of removal of pollutants from wastewater. In this study we attempted to produce and test the activated carbon produced from the refused tea waste for the removal of dyes from wastewater. The objectives of this investigation were to produce activated carbon from refused tea waste by chemical activation, evaluate its performance for the removal of color produced from Acid Yellow 36, and the modeling of its dye removal with the kinetic study. The activation was performed in two steps namely carbonization at $375{\pm}25^{\circ}C$ and chemical activation with HCl at $800^{\circ}C$ under the absence of Oxygen. Adsorption isotherms and kinetic studies were performed with a textile dye, Acid Yellow 36, at different concentrations (20-80 mg/L). The maximum dye removal (~90%) observed at 80 mg/L dye concentration and it reduced at low dye concentrations. Maximum adsorption (71.97 mg/g) was recorded at 96 h at $29{\pm}1^{\circ}C$. Low pH increased the dye adsorption (pH=2; 78.27 mg/g) while adsorption reduced at high pH levels indicating that the competition occurs in between OH- ions and AY36 molecules for the adsorption sites in RTAC. The Langmuir isotherm model clearly explained the dye adsorption, favorably, by RTAC. Moreover, kinetic studied performed showed that the pseudo second order kinetic model clearly describes the dye adsorption. Based on the results obtained in this study, it can be concluded that RTAC can be used for the removal of textile dyes.

• Journal of Applied Biological Chemistry
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• 제43권1호
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• pp.25-30
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• 2000

The main form of nitrogen fertilizer applied to lowland rice is urea, but little is known about its transport in waterlogged soil. This study was conducted to investigate the transport of urea in waterlogged soil column using WAVE (simulation of the substances Water and Agrochemicals in the soil, crop and Vadose Environment) model which includes the parameters for urea adsorption and hydrolysis, The adsorption distribution coefficient and hydrolysis rate of urea were measured by batch experiments. A transport experiment was carried out with the soil column which was pre-incubated for 45 days under flooded condition. The urea hydrolysis rate (k) was $0.073h^{-1}$. Only 5% of the applied urea remained in soil column at 4 days after urea application. The distribution coefficient ($K_d$) of urea calculated from adsorption isotherm was $0.21Lkg^{-1}$, so it was assumed that urea that urea was a weak-adsorbing material. The maximum concentration of urea was appeared at the convective water front because transport of mobile and weak-adsorbing chemicals, such as urea, is dependent on water convective flow. The urea moved down to 11 cm depth only for 2 days after application, so there is a possibility that unhydrolyzed urea could move out of the root zone and not be available for crops. A simulated urea concentration distribution in waterlogged soil column using WAVE model was slightly different from the measured concentration distribution. This difference resulted from the same hydrolysis rate applied to all soil depths and overestimated hydrodynamic dispersion coefficient. In spite of these limitations, the transport of urea in waterlogged soil column could be predict with WAVE model using urea hydrolysis rate (k) and distribution coefficient ($K_d$) which could be measured easily from a batch experiment.

• 한국지하수토양환경학회지:지하수토양환경
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• 제13권1호
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• pp.101-109
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• 2008

국내 화학회사에서 발생되는 연마분진 폐기물에 대한 흡착제로서의 재이용성을 평가하기 위하여 연마분진을 $550^{\circ}C$에서 하소시켜 얻어진 무정형 알루미늄 산화물(AMA-L)을 이용하여 양이온 중금속인 구리, 카드뮴, 납 등에 대한 흡착특성을 파악하였으며 MINEQL + 프로그램을 적용하여 AMA-L과 양이온 중금속 이온간의 표면흡착결합 반응을 모사하여 흡착실험결과와 비교하였다. 구리와 카드뮴, 납의 단일성분에 대한 AMA-L의 흡착실험결과, 납 > 구리 > 카드뮴의 순서로 친화력의 차이가 발생하는 것을 확인하였다. 구리와 카드뮴의 농도변화에 따른 AMA-L 흡착실험 결과 구리와 카드뮴의 농도를 증가시킴에 따라 두 성분의 흡착효율은 모두 감소되는 것으로 나타났으며 구리와 카드뮴이 동시에 존재하는 이성분계 흡착의 경우에는 단일성분으로 존재하는 경우와 유사한 흡착율을 나타내었으며 경쟁이온의 영향을 거의 받지 않는 것으로 확인이 되었다. 또한, AMA-L에 대한 흡착특성에 대한 MINEQL+를 이용한 모사결과 단일성분과 이성분계 흡착에 대한 흡착특성은 비교적 잘 일치하는 것으로 나타났다.

• 한국재료학회지
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• 제26권6호
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• pp.298-305
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• 2016

In this work, recent progress on graphene/metal oxide composites as advanced materials for $HgCl_2$ and $CO_2$ capture was investigated. Density Functional Theory calculations were used to understand the effects of temperature on the adsorption ability of $HgCl_2$ and water vapor on $CO_2$ adsorption on CaO (001) with reinforced carbon-based nanostructures using B3LYP functional. Understanding the mechanism by which mercury and $CO_2$ adsorb on graphene/CaO (g-CaO) is crucial to the design and fabrication of effective capture technologies. The results obtained from the optimized geometries and frequencies of the proposed cluster site structures predicted that with respect to molecular binding the system possesses unusually large $HgCl_2$ ($0.1-0.4HgCl_2g/g$ sorbent) and $CO_2$ ($0.2-0.6CO_2g/g$ sorbent) uptake capacities. The $HgCl_2$ and $CO_2$ were found to be stable on the surface as a result of the topology and a strong interaction with the g-CaO system; these results strongly suggest the potential of CaO-doped carbon materials for $HgCl_2$ and $CO_2$ capture applications, the functional gives reliable answers compared to available experimental data.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권1호
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• pp.67-71
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• 2006

This paper compares regression and neural network modeling approaches to predict competitive biosorption equilibrium data. The regression approach is based on the fitting of modified Langmuir-type isotherm models to experimental data. Neural networks, on the other hand, are non-parametric statistical estimators capable of identifying patterns in data and correlations between input and output. Our results show that the neural network approach outperforms traditional regression-based modeling in correlating and predicting the simultaneous uptake of copper and cadmium by a microbial biosorbent. The neural network is capable of accurately predicting unseen data when provided with limited amounts of data for training. Because neural networks are purely data-driven models, they are more suitable for obtaining accurate predictions than for probing the physical nature of the biosorption process.

• Journal of Microbiology and Biotechnology
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• 제15권1호
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• pp.40-47
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• 2005

Modeling and simulation for simultaneous saccharification and fermentation (SSF) process in bioconversion of paper mill sludge to lactic acid was carried out. The SSF process combined the enzymatic hydrolysis of paper mill sludge into glucose and the fermentation of glucose into lactic acid in one reactor. A mathematical modeling for cellulose hydrolysis was developed, based on the proposed mechanism of cellulase adsorption deactivation. Another model for simple lactic acid fermentation was also made. A whole mathematical model for SSF was developed by combining the above two models for cellulose hydrolysis and lactic acid fermentation. The characteristics of the SSF process were investigated using the mathematical model.

• 한국암석학회:학술대회논문집
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• 한국암석학회 1999년도 춘계학술대회
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• pp.107-111
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• 1999

• 환경생물
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• 제39권3호
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• pp.298-310
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• 2021

Prediction of the behavior of heavy metals over time is important to evaluate the heavy metal toxicity in algae species. Various modeling studies have been well established, but there is a need for an improved model for predicting the chronic effects of metals on algae species to combine the metal kinetics and biological response of algal cells. In this study, a kinetic dynamics model was developed to predict the copper behavior(5 ㎍ L^-1, 10 ㎍ L^-1, and 15 ㎍ L^-1) for two freshwater algae (Pseudokirchneriella subcapitata and Chlorella vulgaris) in the chronic exposure experiments (8 d and 21 d). In the experimental observations, the rapid change in copper mass between the solutions, extracellular and intracellular sites occurred within initial exposure periods, and then it was slower although the algal density changed with time. Our model showed a good agreement with the measured copper mass in each part for all tested conditions with an elapsed time (R² for P. subcapitata: 0.928, R² for C. vulgaris: 0.943). This study provides a novel kinetic dynamics model that is compromised between practical simplicity and realistic complexity, and it can be used to investigate the chronic effects of heavy metals on the algal population.