• 한국토양비료학회지
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• 제49권6호
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• pp.789-794
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• 2016

Continuous excessive application of phosphorus (P) fertilizer and manure in plastic film house soils can lead to an accumulation of P in soils. The understanding of P sorption by soils is important for fertilizer management. In this study, 9 samples were collected for acidic and calcareous soils as non-cultivated soil and plastic film house soils as cultivated soil Phosphorus sorption data of acidic soils fit the Langmuir equations, Freundlich equations in calcareous and plastic film house soils. In calcareous and plastic film house soils, the slope of isotherm adsorption changed abruptly, which could be caused P precipitation with $CaCO_3$. The calculated Langmuir adsorption maximum ($S_{max}$) varied from 217 to 1,250, 139 to 1,429, and $714mg\;kg^{-1}$ for acidic soils, calcareous soils, and plastic film house soils with low available phosphate concentration, respectively. From this result, maximum P adsorption by the Langmuir equation could be regarded as threshold of P concentration to induce the phosphate precipitation in soil. Phosphate-sorption values estimated from one-point isotherm for acidic and calcareous soils as non-cultivated soils were comparable with the $S_{max}$ values calculated from the Langmuir isotherm.

• 공업화학
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• 제29권4호
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• pp.369-375
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• 2018

폐감귤박 활성탄(WCAC, waste citrus peel based activated carbon)에 의한 항생제 아목시실린(AMX)의 흡착에서 온도, 초기농도, 접촉시간 및 흡착제 투여량과 같은 운전변수의 영향을 조사하기 위해 회분식 실험을 수행하였다. 흡착 속도 및 등온 실험결과는 각각 유사 2차 속도식 및 Langmuir 등온 모델에 의해 잘 설명될 수 있었다. Langmuir 등온 모델로부터 계산된 WCAC에 의한 AMX의 최대 흡착량은 345.49 mg/g이었다. WCAC에 의한 AMX의 흡착은 흡착 과정에서 막 확산(외부 물질 전달)과 입자 내부 확산이 동시에 일어난다는 것을 보여 주었다. 흡착 속도는 WCAC의 입자 크기가 증가함에 따라 외부 물질 전달보다 입자 내부 확산에 의해 더 영향을 받았고, 입자 내부 확산이 율속 단계였다. 열역학적 파라미터는 WCAC에 의한 AMX의 흡착 반응은 흡열반응이고 자발적인 과정임을 나타내었다.

• Korean Chemical Engineering Research
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• 제54권2호
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• pp.255-261
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• 2016

활성탄을 사용한 Acid Yellow 14 염료의 흡착 실험은 흡착제의 양, pH, 초기농도, 접촉시간과 온도를 흡착변수로 사용하여 수행하였다. 흡착평형자료는 Langmuir, Freundlich 및 Temkin 등온식을 사용하여 해석하였는데, Freundlich 식이 가장 좋은 일치도를 나타냈다. 평가된 Freundlich 상수(1/n=0.129~0.212)와 Langmuir 분리계수($R_L=0.202{\sim}0.243$)로부터 활성탄에 의한 Acid Yellow 14의 흡착조작은 적절한 처리방법이 될 수 있음을 알았다. Temkin의 흡착열관련상수(B)는 5.101~9.164 J/mol로 평가되어, 흡착공정이 물리흡착임을 알았다. 흡착속도실험자료를 유사일차반응속도식과 유사이차반응속도식에 적용해 본 결과, 흡착동력학은 유사이차반응속도식에 잘 맞는 것으로 나타났다. Gibbs 자유에너지(-4.81~-10.33 kJ/mol)와 엔탈피(+78.59 kJ/mol)는 흡착이 자발적이고 흡열공정으로 진행된다는 것을 나타낸다.

• 공업화학
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• 제25권6호
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• pp.632-638
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• 2014

입상활성탄을 사용하여 new fuchsin 염료를 흡착하는데 필요한 흡착등온선과 흡착동역학 및 열역학 파라미터들에 대하여 조사하였다. 흡착평형은 Langmuir 흡착등온식이 가장 잘 맞았으며, 등온흡착평형관계로부터 Langmuir 식과 Freundlich 식의 분리계수를 평가한 결과, 분리계수값이 각각 $R_L$ = 0.023, 1/n=0.198로 입상활성탄에 의한 new fuchsin 염료의 흡착조작이 유효한 처리방법이 될 수 있음을 알았다. Dubinin-Radushkevich 식으로 구한 흡착에너지값(E = 0.002 kJ/mol)과 Temkin 식으로부터 구한 흡착열상수값(B = 1.920 J/mol)으로부터 흡착공정이 물리흡착공정임을 알았다. 흡착공정에 대한 동력학적 해석을 통해 흡착반응은 유사이차반응속도식이 유사일차반응속도식과 비교하여 일치도가 높은 것으로 나타났으며, 입자 내 확산이 흡착공정의 지배단계이었다. 열역학적 해석을 통해 평가된 엔탈피 변화값(92.49 kJ/mol)과 활성화에너지값(11.79 kJ/mol)으로부터 흡착공정이 흡열반응으로 진행되었다. 또한, 엔트로피 변화값이 313.7 J/mol K로 흡착공정의 무질서도가 증가하였다. 온도가 올라갈수록 자유에너지값이 감소하는 것은 활성탄에 대한 new fuchsin 염료의 흡착반응은 온도가 올라갈수록 자발성이 높아지는 것으로 판단되었다.

• Corrosion Science and Technology
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• 제8권1호
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• pp.1-10
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• 2009

The influence of Schiff bases on the corrosion inhibition of mild steel in 1 M $H_2SO_4$ have been investigated by weight loss, gasometry, impedance and polarization techniques. The results obtained reveal that these compounds act as good inhibitors. The inhibition efficiency of Schiff bases increased with concentration and synergistically increased on addition of chromate, sulphate and halide ions. Potentiodynamic polarization measurements clearly reveal that the investigated inhibitors are of mixed type but they are more cathodic in nature. The adsorption of these compounds on mild steel surface for both the acids were found to obey Langmuir adsorption isotherm. The surface morphology was studied by SEM and UV reflectance spectra.

• Journal of Electrochemical Science and Technology
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• 제4권2호
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• pp.81-87
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• 2013

Inhibition of corrosion of mild steel in sulphuric acid by acidic extract of Jatropha Curcas leaves has been studied using weight loss and thermometric measurements. It was found that the leaves extract act as a good corrosion inhibitor for mild steel in all concentrations of the extract. The inhibition action depends on the concentration of the Jatropha Curcas leaves extract in the acid solution. Results for weight loss and thermometric measurements indicate that inhibition efficiency increase with increasing inhibitor concentration. The adsorption of Jatropha curcas leaves extract on the surface of the mild steel specimens obeys Langmuir adsorption isotherm. Based on the results, Jatropha curcas leaves extract is recommended for use in industries as a replacement for toxic chemical inhibitors.

• 한국재료학회지
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• 제23권8호
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• pp.462-468
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• 2013

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.

• Advances in environmental research
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• 제1권2호
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• pp.143-151
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• 2012

Nitrate removal from aqueous solution was investigated using $ZnCl_2$ and phosphoric acid activated carbon developed from pomegranate peel with particle size 0.4 mm. Potassium nitrate solution was used in batch adsorption experiments for nitrate removal from water. The effects of activated carbon dosage, time of contact, and pH were studied. The equilibrium time was fond to be 45 min. Two theoretical adsorption isotherms namely Langmuir and Freundlich were used to describe the experimental results. The Langmuir fit the isotherm with the theoretical adsorption capacity ($q_t$) was fond 78.125 mg g-1. Adsorption kinetics data were modeled using the pseudo-first, pseudo-second order, and intraparticle diffusion models. The results indicate that the second-order model best describes adsorption kinetic data. Results show activated carbon produced from pomegranate is effective for removal of nitrate from aqueous solution.

• 전기화학회지
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• 제12권4호
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• pp.311-316
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• 2009

인공해수에서 일어나는 Al의 부식에 대하여 alanine과 methionine의 부식억제 효과를 조사하였다. 이들 아미노산의 낮은 덮힘율로 보아 Al 표면에 alanine과 methionine는 Langmuir adsorption isotherm에 따른 흡착이 일어나며, 아미노산 안의 카르복시 이온만이 Al에 흡착하는 것으로 보인다.

• 한국환경보건학회지
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• 제29권3호
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• pp.50-58
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• 2003

Removal of heavy metal ions (Cd$^{2+}$, Cr$^{3+}$, Cu$^{2+}$, Pb$^{2+}$) by several chitosans was studied and the molecular weight of chitosan was investigated in order to examine the effect of autoclaving. Chitosan were divided into 3 groups (A type, controlled chitosan; B type, autoclaved for 15 min; C type, autoclaved for 60 min). The heavy metal removal capacity and rate of B type chitosan were higher than those of A type and B type chitosan. The molecular weight of chitosan was decreased by the increase of autoclaving time. Therefore, the heavy metal capacity was not well correlated to the molecular weight. Freundlich and Langmuir isotherm was determined from the experimental results of equilibrium adsorption for individual heavy metal ions on chitosan. Langmuir isotherm was well fitted to this experimental data. The heavy metal removal capacity of B type chitosan was in the order of Pb$^{2+}$ > Cu$^{2+}$ > Cd$^{2+}$> Cr$^{3+}$.3+/.$.3+/.