Adsorption equilibrium, kinetics and mechanism studies of mercury on coal-fired fly ash

Qiang Zhou,Yufeng Duan,Chun Zhu,Jun Zhang,Min She,Hongqi Wei,Yaguang Hong 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.7

Fly ash samples were collected from the electrostatic precipitator (ESP) of a 600MW pulverized coal boiler firing Zhungeer bituminous coal in China to evaluate and explore its mercury adsorption capacity and mechanism. Samples characterization was conducted to feature their morphologies correlated to mercury content, and experimental studies on mercury adsorption in a fixed-bed apparatus were carried out to further verify its mercury adsorption availability. Based on the experimental data, adsorption isotherm was modeled with Langmuir, Freundlich, and Temkin equations. Adsorption kinetic analysis was also performed. The results show that mercury content of fly ash samples is associated with particle size, unburned carbon content and functional groups of Al-O/Si-O or Si-O-Si/Si-O-Al tetrahedron on fly ash. Increase of initial mercury concentration is beneficial to promote mercury adsorption due to the enhancement of mercury diffusion force onto the fly ash surface, mercury intraparticle diffusion rate and initial mercury adsorption rate. Fly ash with medium size displays better mercury adsorption capacity. Smaller particle size results in higher specific surface area, but brings about low specific surface area utilization rate for mercury adsorption. Freundlich isotherm equation presents better fitting result, indicating that fly ash surface is non-uniform. Mercury adsorption on fly ash at 120 oC is mainly physisorption enhanced by chemisorption with ΔG at −36.73 kJ/mol. The pseudo-first-order kinetic model can describe the adsorption process more accurately and predict mercury adsorption capacity of fly ash preferably, showing that mercury adsorption on fly ash surface in fixed-bed is controlled dominantly by external mass transfer.

Kinetic and Isothermal Studies of Uranium Adsorption on Phosphate- Functionalized Mesoporous Silica Microsphere Composite

Hye Ran Noh,Suk-Bon Yoon,Tae-Hyeong Kim,Dong-Woo Lee,Jeongmook Lee,Sang Ho Lim,Jong-Yun Kim 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

Bis (2-ethylhexyl)phosphoric acid (HDEHP) is a renowned extractant, favored for its affinity to selectively remove uranium via its P=O groups. We previously synthesized HDEHP-functionalized mesoporous silica microspheres for solid-phase uranium adsorption. Herein, we investigated the kinetic and isothermal behavior of uranyl ion adsorption in mesoporous silica microspheres functionalized with phosphate groups. Adsorption experiments were conducted by equilibrating 20 mg of silica samples with 50 mL of uranium solutions, with concentrations ranging from 10 to 100 mgU L−1 for isotherms and 100 mgU L−1 for kinetics. Three distinct samples were prepared with varying HDEHP to TEOS molar ratios (x = 0.16 and 0.24) and underwent hydrothermal treatment at different temperatures, resulting in distinct textural properties. Contact times spanned from 1 to 120 hours. For x = 0.16 samples, it took around 50 and 11 hours to reach equilibrium for the hydrothermally treated samples at 343 K and 373 K, respectively. Adsorbed quantities were similar (99 and 101 mg g-1, respectively), indicating consistent functional group content. This suggests that the key factor influencing uranium adsorption kinetics is pore size of the silica. The sample treated at 373 K, with a larger pore size (22.7 nm) compared to 343 K (11.5 nm), experienced less steric hindrance, allowing uranium species to diffuse more easily through the mesopores. The data confirmed the excellent fit of pseudo-second-order kinetic model (R2 > 0.999) and closely matched the experimental value, suggesting that chemisorption governs the rate-controlling step. To gain further insights into uranium adsorption behavior, we conducted an adsorption isotherm analysis at various initial concentrations under a constant pH of 4. Both the Langmuir and Freundlich isotherm models were applied, with the Langmuir model providing a superior fit. The relatively high R2 value indicated its effectiveness in describing the adsorption process, suggesting homogenous sorbate adsorption on an energetically uniform adsorbent surface via a monolayer adsorption and constant adsorption site density, without any interaction between adsorbates on adjacent sites. Remarkably, differences in surface area did not significantly impact uranium removal efficiency. This observation strongly suggests that the adsorption capacity is primarily governed by the loading amount of HDEHP and the inner-sphere complexation with the phosphoryl group (O=P). Our silica composite exhibited an impressive adsorption capacity of 133 mg g-1, surpassing the results reported in the majority of other silica literature.

석탄 비산재로 합성한 Na-A형 제올라이트에 의한 구리와 아연 이온의 동역학적 흡착 특성

이창한 한국환경과학회 2011 한국환경과학회지 Vol.20 No.12

The adsorption performance of cupper and zinc ions(Cu^(2+) and Zn^(2+)) in aqueous solution was investigated by an adsorption process on reagent grade Na-A zeolite(Z-WK) and Na-A zeolite (Z-C1) prepared from coal fly ash. Z-C1 was synthesized by a fusion method with coal fly ash from a thermal power plant. Batch adsorption experiment with Z-C1 was employed to study the kinetics and equilibrium parameters such as initial metal ions concentration and adsorption time of the solution on the adsorption process. Adsorption rate of metal ions occurred rapidly and adsorption equilibrium reached at less than 120 minutes. The kinetics data of Cu^(2+) and Zn^(2+) ions were well fitted by a pseudo-second-order kinetics model more than a pseudo-first-order kinetics model. The equilibrium data were well fitted by a Langmuir model and this result showed Cu^(2+) and Zn^(2+) adsorption on Z-C1 would be occupied by a monolayer adsorption. The maximum adsorption capacity(qmax) by the Langmuir model was determined as Cu^(2+) 99.8 mg/g and Zn^(2+) 108.3 mg/g, respectively. It appeared that the synthetic zeolite, Z-C1, has potential application as absorbents in metal ion recovery and mining wastewater.

활성탄에 의한 작용기가 다른 염료의 흡착: 파라미터 및 경쟁 흡착

이종집,Lee, Jong Jib 한국공업화학회 2022 공업화학 Vol.33 No.2

In this paper, parameter characteristics such as pH effect, isotherm, kinetic and thermodynamic parameters and competitive adsorption of dyes including malachite green (MG), direct red 81 (DR 81) and thioflavin S (TS), which have different functional groups, being adsorbed onto activated carbon were investigated. Langmuir, Freundlich and Temkin isotherm models were employed to find the adsorption mechanism. Effectiveness of adsorption treatment of three dyes by activated carbon were confirmed by the Langmuir dimensionless separation factor. The mechanism was found to be a physical adsorption which can be verified through the adsorption heat calculated by Temkin equation. The adsorption kinetics followed the pseudo second order and the rate limiting step was intra-particle diffusion. The positive enthalpy and entropy changes showed an endothermic reaction and increased disorder via adsorption at the S-L interface, respectively. For each dye molecule, negative Gibbs free energy increased with the temperature, which means that the process is spontaneous. In the binary component system, it was found that the same functional groups of the dye could interfere with the mutual adsorption, and different functional groups did not significantly affect the adsorption. In the ternary component system, the adsorption for MG lowered a bit, likely to be disturbed by the other dyes meanwhile DR 81 and TS were to be positively affected by the presence of MG, thus resulting in much higher adsorption.

Adsorption of pharmaceuticals onto trimethylsilylated mesoporous SBA-15

Bui, Tung Xuan,Pham, Viet Hung,Le, Son Thanh,Choi, Heechul Elsevier 2013 Journal of hazardous materials Vol.254 No.-

<P><B>Abstract</B></P> <P>The adsorption of a complex mixture of 12 selected pharmaceuticals to trimethylsilylated mesoporous SBA-15 (TMS-SBA-15) has been investigated by batch adsorption experiments. The adsorption of pharmaceuticals to TMS-SBA-15 was highly dependent on the solution pH and pharmaceutical properties (i.e., hydrophobicity (log <I>K</I> <SUB>ow</SUB>) and acidity (p<I>K</I> <SUB>a</SUB>)). Good log–log linear relationships between the adsorption (<I>K</I> <SUB>d</SUB>) and pH-dependent octanol–water coefficients ( K ow pH ) were then established among the neutral, anionic, and cationic compounds, suggesting hydrophobic interaction as a primary driving force in the adsorption. In addition, the neutral species of each compound accounted for a major contribution to the overall compound adsorption onto TMS-SBA-15. The adsorption kinetics of pharmaceuticals was evaluated by the nonlinear first-order and pseudo-second-order models. The first-order model gave a better fit for five pharmaceuticals with lower adsorption capacity, whereas the pseudo-second-order model fitted better for seven pharmaceuticals having higher adsorption capacity. In the same group of properties, pharmaceuticals having higher adsorption capacity exhibited faster adsorption rates. The rate-limiting steps for adsorption of pharmaceuticals onto TMS-SBA-15 are boundary layer diffusion and intraparticle diffusion including diffusion in mesopores and micropores. In addition, the adsorption of pharmaceuticals to TMS-SBA-15 was not influenced by the change of initial pharmaceutical concentration (10–100μgL<SUP>−1</SUP>) and the presence of natural organic matter.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Trimethylsilylated SBA-15 for adsorptive removal of a mixture of 12 pharmaceuticals. </LI> <LI> Hydrophobic interaction as a primary driving force in the adsorption. </LI> <LI> The rate-limiting steps were diffusion through boundary layer, mesopores and micropores. </LI> <LI> Adsorption efficiency was not changed as pharmaceutical concentration varied. </LI> <LI> Adsorption efficiency was not influenced by the presence of natural organic matters. </LI> </UL> </P>

Chemically activated microporous carbons derived from petroleum coke: Performance evaluation for CF₄ adsorption

Yuan, XiangZhou,Choi, Seung Wan,Jang, Eunji,Lee, Ki Bong Elsevier 2018 Chemical engineering journal Vol.336 No.-

<P><B>Abstract</B></P> <P>CF<SUB>4</SUB> is considered to be a significant global-warming compound and has a fairly long atmospheric lifetime, which exacerbates climate change. Adsorption is considered a promising technology for capturing CF<SUB>4</SUB> and appropriate adsorbent is one of key factors for successful development of adsorption method. In this study, CF<SUB>4</SUB> adsorption using microporous carbon materials was investigated from both equilibrium and kinetic perspectives. Petroleum coke (PC) was utilized for developing CF<SUB>4</SUB> adsorbents by carbonization and KOH-activation processes. The carbonization temperature and KOH/PC mass ratio were varied from 300 to 600 °C and from 1 to 3, respectively. Varying the carbonization temperature and KOH/PC mass ratio had a dramatic effect on the textual properties of the prepared samples. CF<SUB>4</SUB> adsorption was well fitted by the Langmuir isotherm model, and the CF<SUB>4</SUB> uptake was remarkably dominated by the surface area and pore volume of narrow micropores below 0.8 nm in diameter. The experimental CF<SUB>4</SUB> adsorption data were well described by the pseudo-second-order kinetic model, compared with the Elovich and intra-particle-diffusion models, and CF<SUB>4</SUB> adsorption appeared to be mainly controlled by physisorption. The PC450-K2 adsorbent, prepared using a carbonization temperature of 450 °C and a KOH/PC mass ratio of 2, exhibited the highest CF<SUB>4</SUB> adsorption uptake of 2.79 mol kg<SUP>−1</SUP> at 25 °C and 1 atm, in addition to good CF<SUB>4</SUB>/N<SUB>2</SUB> selectivity at relatively low CF<SUB>4</SUB> pressures, excellent recyclability, easy regeneration, and rapid adsorption-desorption kinetics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Microporous carbons were prepared from petroleum coke by carbonization and activation. </LI> <LI> The synthesized microporous carbon showed high CF<SUB>4</SUB> adsorption uptake. </LI> <LI> Fast adsorption-desorption kinetics and excellent cyclic stability were achieved. </LI> <LI> The effects of textural properties on CF<SUB>4</SUB> adsorption uptake were investigated. </LI> </UL> </P>

입상 활성탄에 대한 New Fuchsin 염료흡착의 등온선, 동력학 및 열역학 파라미터에 관한 연구

이종집 ( Jong Jib Lee ) 한국공업화학회 2014 공업화학 Vol.25 No.6

Batch adsorption studies including equilibrium, kinetics and thermodynamic parameters for the adsorption of new fuchsin dye using granular activated carbon were investigated with varying the operating variables such as initial concentration, contact time and temperature. Equilibrium adsorption data were fitted into Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherms. Adsorption equilibrium was mostly well described by Langmuir Isotherm. From the estimated separation factor of Langmuir (RL = 0.023), and Freundlich (1/n = 0.198), this process could be employed as an effective treatment for the adsorption of new fuchsin dye. Also based on the adsorption energy (E = 0.002 kJ/mol) from Dubinin-Radushkevich isotherm and the adsorption heat constant (B = 1.920 J/mol) from Temkin isotherm, this adsorption is physical adsorption. From kinetic experiments, the adsorption reaction processes were confirmed following the pseudo second order model with good correlation. The intraparticle diffusion was a rate controlling step. Thermodynamic parameters including changes of free energy, enthalpy, and entropy were also calculated to predict the nature of adsorption. The change of enthalpy (92.49 kJ/mol) and activation energy (11.79 kJ/mol) indicated the endothermic nature of adsorption processes. The change of entropy (313.7 J/mol K) showed an increasing disorder in the adsorption process. The change of free energy found that the spontaneity of process increased with increasing the adsorption temperature.

활성탄에 의한 Acid Fuchsin 염료의 흡착에 대한 등온선, 동력학 및 열역학 특성치에 대한 해석

이종집 ( Jong Jib Lee† ) 한국화학공학회 2020 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.58 No.3

Isotherms, kinetics and thermodynamic properties for adsorption of acid fuchsin (AF) dye by activated carbon were carried out using variables such as dose of adsorbent, pH, initial concentration and contact time and temperature. The effect of pH on adsorption of AF showed a bathtub with high adsorption percentage in acidic (< pH 5) and basic ( >pH 8). Isothermal adsorption data were fitted to the Freundlich, Langmuir, and Dubinin-Radushkevich isotherm models. Freundlich isothem model showed the highest agreement and confirmed that the adsorption mechanism was multilayer adsorption. It was found that adsorption capacity increased with increasing temperature. Freundlich’s separation factor showed that this adsorption process was an favorable treatment process. Estimated adsorption energy by Dubinin-Radushkevich isotherm model indicated that the adsorption of AF by activated carbon is a physical adsorption. Adsorption kinetics was found to follow the pseudo-second-order kinetic model. Surface diffusion at adsorption site was evaluated as a rate controlling step by the intraparticle diffusion model. Thermodynamic parameters such as activation energy, Gibbs free energy, enthalpy entropy and isosteric heat of adsorption were investigated. The activation energy and enthalpy change of the adsorption process were 21.19 kJ / mol and 23.05 kJ / mol, respectively. Gibbs free energy was found that the adsorption reaction became more spontaneously with increasing temperature. Positive entropy was indicated that this process was irreversible. The isosteric heat of adsorption was indicated physical adsorption in nature.

Isotherm, kinetic and thermodynamic studies on the adsorption of paclitaxel onto Sylopute

Kim, Ye-Sol,Kim, Jin-Hyun Elsevier 2019 The Journal of chemical thermodynamics Vol.130 No.-

<P><B>Abstract</B></P> <P>Batch experimental studies were carried out on the adsorption of paclitaxel onto Sylopute, with the data then being fit to the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. A comparison of the results revealed that, among the four isotherm models considered, the Freundlich isotherm model could account for the adsorption isotherm data with the highest accuracy. From the analysis of adsorption isotherms, it was found that the adsorption capacity increased with an increasing temperature and the adsorption of paclitaxel onto Sylopute was favourable. The obtained kinetics data for paclitaxel adsorption with Sylopute agreed well with the pseudo-second-order model. In addition, according to the intraparticle diffusion model, intraparticle diffusion played a dominant role in paclitaxel adsorption. Thermodynamic parameters revealed the endothermic, irreversible, and nonspontaneous nature of the adsorption.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Freundlich isotherm accounted for adsorption data of paclitaxel on Sylopute. </LI> <LI> The adsorption process was physical in nature. </LI> <LI> The kinetics data agreed well with the pseudo-second-order model. </LI> <LI> The adsorption process was endothermic, irreversible and nonspontaneous. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Isotherm, kinetic and thermodynamic studies on the adsorption of 13-dehydroxybaccatin III from <i>Taxus chinensis</i> onto Sylopute

Lim, Yeon-Su,Kim, Jin-Hyun Elsevier 2017 The Journal of chemical thermodynamics Vol.115 No.-

<P><B>Abstract</B></P> <P>Batch experimental studies were carried out on the adsorption of 13-dehydroxybaccatin III (13-DHB III) using Sylopute while varying parameters such as initial 13-DHB III concentrations, contact times and adsorption temperatures. Out of Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models, adsorption data with the highest accuracy were best described by the Langmuir isotherm. It was found that the adsorption capacity decreased with an increasing temperature and the adsorption of 13-DHB III onto Sylopute was favourable. The adsorption kinetics were well described by the pseudo-second-order kinetic model, while intraparticle diffusion and boundary layer diffusion did not play a dominant role in 13-DHB III adsorption according to the intraparticle diffusion model. Thermodynamic parameters revealed the exothermic, irreversible and non-spontaneous nature of adsorption. The isosteric heat of adsorption was constant even with variations in surface loading, indicating a heterogeneous surface.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Langmuir isotherm accounted for adsorption data of 13-dehydroxybaccatin III on Sylopute. </LI> <LI> The adsorption process was physical in nature. </LI> <LI> The kinetics data agreed well with the pseudo-second-order model. </LI> <LI> The adsorption process was exothermic, irreversible and nonspontaneous. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>