• Environmental Engineering Research
• /
• 제22권1호
• /
• pp.95-107
• /
• 2017

Adsorption equilibrium and kinetic behavior of two toxic heavy metals hexavalent chromium [Cr(VI)] and mercury [Hg(II)] on mustard oil cake (MOC) was studied. Isotherm of total chromium was of concave type (S1 type) suggesting cooperative adsorption. Total chromium adsorption followed BET isotherm model. Isotherm of Hg(II) was of L3 type with monolayer followed by multilayer formation due to blockage of pores of MOC at lower concentration of Hg(II). Combined BET-Langmuir and BET-Freundlich models were appropriate to predict Hg(II) adsorption data on MOC. Boyd's model confirmed that external mass transfer was rate limiting step for both total chromium and Hg(II) adsorptions with average diffusivity of $1.09{\times}10^{-16}$ and $0.97m^2/sec$, respectively. Desorption was more than 60% with Hg(II), but poor with chromium. The optimum pH for adsorptions of total chromium and Hg(II) were 2-3 and 5, respectively. At strong acidic pH, Cr(VI) was adsorbed by ion exchange mechanism and after adsorption reduced to Cr(III) and remained on MOC surface. Hg(II) removal was achieved by complexation of $HgCl_2$ with deprotonated amine ($-NH_2$) and carboxyl (COO-) groups of MOC.

• 공업화학
• /
• 제25권6호
• /
• pp.632-638
• /
• 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.

• Korean Chemical Engineering Research
• /
• 제58권1호
• /
• pp.113-121
• /
• 2020

실로퓨트에 대한 Taxus chinensis 유래 7-에피-10-디아세틸파클리탁셀의 흡착을 회분식 실험에서 연구하였다. 흡착 평형 데이터를 Langmuir, Freundlich, Temkin 및 Dubinin-Radushkevich 등온흡착식에 적용한 결과, Langmuir 등온흡착식이 가장 높은 정확도를 나타내었다. 흡착 용량은 온도가 증가함에 따라 감소하였으며, 실로퓨트에 대한 7-에피-10-디아세틸파클리탁셀의 흡착은 적합한 물리적 공정이었다. 흡착 데이터는 유사 이차 동역학 모델과 매우 잘 일치하였으며, 경계층 확산과 입자 내 확산은 흡착 과정에 거의 영향을 미치지 않았다. 실로퓨트에 대한 7-에피-10-디아세틸파클리탁셀 흡착 과정은 발열이며 비자발적이었다. 또한, 등량흡착열은 흡착량에 의존하지 않아 흡착제의 표면 에너지가 균일함을 알 수 있었다.

• Advances in environmental research
• /
• 제7권1호
• /
• pp.29-37
• /
• 2018

A simple mathematical model for predicting fixed bed adsorption dynamics is described. The model is characterized by a linear adsorption isotherm and a linear driving force expression for mass transfer. Its analytic solution can be approximated with an algebraic equation in closed form which is easily evaluated by spreadsheet computation. To demonstrate one application of the fixed bed model, a previously published adsorption system is used as a case study in this work. The adsorption system examined here describes chromium breakthrough in a fixed bed adsorber packed with imidazole functionalized adsorbent particles and is characterized by a nonlinear adsorption isotherm. However, the equilibrium behavior of the fixed bed adsorber is in essence governed by a linear adsorption isotherm due to the use of a low influent chromium concentration. It is shown that chromium breakthrough is predicted reasonably well by the fixed bed model. The model's parameters can be easily extracted from independent batch experiments. The proposed modeling approach is very simple and rapid, and only Excel is used for computation.

• Carbon letters
• /
• 제9권2호
• /
• pp.97-104
• /
• 2008

In the present study Sisal fiber obtained from the leaves of Agave sisalana has been chosen to validate its viability as an adsorbent for the removal of Nickel from aqueous solutions. The material was also surface modified and its effect on adsorption of Nickel was also studied. Agave sisalana fiber was found to be a cheap and effective adsorbent doing away with the need to activate the material therby reducing processing cost. The equilibrium studies indicated that the adsorption capacity of raw fiber and the surface modified fiber was 8.66 and 9.77 mg/g respectively with the Langmuir isotherm describing the adsorption phenomena better than the Freundlich and Temkin isotherm. The adsorption was found to be exothermic from the thermodynamic studies and the kinetics showed that the adsorption phenomena were second order.

• 한국환경과학회지
• /
• 제12권10호
• /
• pp.1061-1069
• /
• 2003

The adsorption behaviors of strontium and cesium ions on fly ash, natural zeolites, and zeolites synthesized from fly ash were investigated. The zeolites synthesized from fly ash had greater adsorption capabilities for strontium and cesium ions than the original fly ash and natural zeolites. The maximum adsorption capacity of synthetic zeolite for strontium and cesium ions was 100 and 154 mg/g, respectively, It was found that the Freundlich isotherm model could fit the adsorption isotherm. The distribution coefficients (K$\_$d/) for strontium and cesium ions were also calculated from the adsorption isotherm data, The distribution coefficients decreased with increasing equilibrium concentration of strontium and cesium ions in solution. By studying the removal of cesium and strontium ions in the presence of calcium, magnesium, sodium, potassium, sulfate, nitrate, nitrite, and EDTA (in the range of 0.01 - 5 mM) it was found that these coexistence ions competed for the same adsorption sites with strontium and cesium ions.

• 한국지반환경공학회 논문집
• /
• 제11권1호
• /
• pp.45-51
• /
• 2010

본 연구는 hydroxyapatite(HAP) 첨가 활성탄(HAP sorbent)의 카드뮴에 대한 흡착특성을 조사하였다. HAP 첨가량의 변화에 따른 카드뮴의 제거특성은 HAP 첨가량이 증가 할수록 카드뮴의 제거량은 흡착에 의한 영향으로 증가하는 것으로 나타났다. 이러한 결과는 HAP에 의한 이온교환능력의 증가에 의한 것으로 사료된다. 동역학적 흡착과 흡착평형에 관한 연구는 연속적인 회분식 실험을 통하여 조사하였다. 조사된 흡착평형 데이터는 Langmuir와 Freundlich isotherm mode을 사용하여 살펴보았으며, 초기 흡착질의 농도 변화에 따른 HAP 첨가 활성탄의 카드뮴의 흡착은 Freundlich isotherm model에 적합한 것으로 나타났다. Cd의 흡착반응의 동역학적 연구를 위하여 유사 1차 반응속도와 유사 2차 반응속도 모델을 사용하 Cd 흡착반응의 흡착 메커니즘을 조사하였다. 유사 2차 반응속도를 따르며, 유사 2차 반응속도 상수는 활성탄에 HAP의 첨가량이 증가할수록 증가하는 것을 확인할 수 있었다. 또한, intraparticle diffusion model을 사용하여 수용액상의 흡착질과 흡착매질과의 흡착 메커니즘을 조사하였다. 수용액상 카드뮴의 흡착 메커니즘은 흡착질과 흡착매질에서 표면흡착반응과 입자내 확산이 동시에 일어나는 것으로 확인되었다.

• 한국물환경학회지
• /
• 제16권4호
• /
• pp.555-563
• /
• 2000

The study was conducted to evaluate the adsorption equilibrium of heavy metals on bone charcoal made of livestock bone which was sintered at $550{\sim}600^{\circ}C$. Analysis of bone charcoal by XRD and FT-IR showed that crystal structure was similar to that of synthetic hydroxyapatite. Adsorption equilibrium capacity of single component (Pb, Cd, and Zn) on bone charcoal could be expressed as Langmuir, Freundlich, and Sips equations. Sips isotherm was best among the three isotherms. The values predicted by IAST(ideal adsorbed solution theory) showed good relationship to the experimental data in multicomponent adsorption equilibrium. Adsorption affinity was in order of Pb, Cd, and Zn. The order was same in case of activated carbon or synthetic hydroxyapatite. Through the study results. it would be expected that bone charcoal made of livestock could be used in field of wastewater treatment plants as adsorbent to remove heavy metal.

• Advances in environmental research
• /
• 제3권2호
• /
• pp.131-149
• /
• 2014

Two different model selection indices, the Akaike information criterion (AIC) and the coefficient of determination ($R^2$), are used to discriminate competing isotherm equations for aqueous pollutant removal systems. The former takes into account model accuracy and complexity while the latter considers model accuracy only. The five types of isotherm shape in the Brunauer-Deming-Deming-Teller (BDDT) classification are considered. Sorption equilibrium data taken from the literature were correlated using isotherm equations with fitting parameters ranging from two to five. For the isotherm shapes of types I (favorable) and III (unfavorable), the AIC favors two-parameter equations which can easily track these simple isotherm shapes with high accuracy. The $R^2$ indicator by contrast recommends isotherm equations with more than two parameters which can provide marginally better fits than two-parameter equations. To correlate the more intricate shapes of types II (multilayer), IV (two-plateau) and V (S-shaped) isotherms, both indices favor isotherm equations with more than two parameters.

• 한국안전학회지
• /
• 제15권4호
• /
• pp.88-94
• /
• 2000

The adsorption characteristics of Tharonil on granular activated carbon were experimentally investigated in an adsorber and in a packed column. It was estabilished that the adsorption equilibrium of Tharonil on granular activated carbon was more successfully fitted by Freundlich isotherm equation than Langmuir isotherm equation in the concentration range from 1 to 1000 mg/1. Intraparticle diffusivities (pore and surface diffusivity) of Tharonil were estimated by the concentration-time curve and adsorption isotherm. The estimated values of pore diffusivity and surface diffusivity are $6.70{\times}10^{-6}$ and $2.0{\times}10^{-9}cm^2/s$, respectively. From comparison of intraparticle diffusivities, it was found that surface diffusion was the limiting step for adsorption rate. The break time and breakthrough curve predicted by constant pattern-linear driving force model were shown to agree with the experimental results.