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.

Water adsorption/desorption over metal-organic frameworks with ammonium group for possible application in adsorption heat transformation

An, Hyung Jun,Sarker, Mithun,Yoo, Dong Kyu,Jhung, Sung Hwa Elsevier 2019 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.373 No.-

<P><B>Abstract</B></P> <P>Typical metal-organic frameworks (MOFs) such as UiO-66 and MIL-125 were modified to introduce –NH<SUB>2</SUB> and –NH<SUB>3</SUB> <SUP>+</SUP>Cl<SUP>−</SUP> groups in order to improve their performances for water adsorption and for possible applications in adsorption heat transformation (AHT). Not only adsorption isotherms but also dynamic water adsorption/desorption (in 10 cycles) results showed that the functionalization, especially loading of the –NH<SUB>3</SUB> <SUP>+</SUP>Cl<SUP>−</SUP> group, was very effective for such purposes. Both the adsorption capacity (especially, at low vapor pressure) and dynamic water uptake (via cyclic adsorption/desorption of water) increased notably with the modification of the MOFs. The positive effect could be explained by hydrogen bonding and electrostatic interactions, which are not possible with the pristine MOFs. Therefore, it could be suggested that loading moieties with charge and ample hydrogen (such as ammonium group) is a very effective means of modifying MOFs for water adsorption or for application in AHT.</P> <P><B>Highlight</B></P> <P> <UL> <LI> Metal-organic frameworks were modified to load amino and ammonium groups. </LI> <LI> The modified MOFs showed highly enhanced performances for water adsorption. </LI> <LI> Adsorption capacity and dynamic water uptake increased much with the modification. </LI> <LI> The favorable effect could be explained with H-bonding and electrostatic interaction. </LI> <LI> The modified MOFs were very stable in dynamic adsorption/desorption for 10 cycles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

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.

페리하이드라이트의 산화음이온 흡착 특성과 광물상 변화

김규례(Gyure Kim),김영규(Yeongkyoo Kim) 대한자원환경지질학회 2023 자원환경지질 Vol.56 No.3

페리하이드라이트는 산상광산배수를 포함한 자연 환경에서 쉽게 관찰되는 산화철 광물로 결정도가 낮고 높은 비표면적을 갖고 있어 다른 이온과의 반응성이 매우 우수하여 환경유해물질과의 반응을 통하여 이의 제거가 가능하다. 그러나 페리하이드라이트는 준안정성 광물이기 때문에 표면적이 작고 결정도가 높은 다른 광물로의 상변화로 흡착된 이온들의 방출 가능성도 존재한다. 본 연구에서는 비산염, 크롬산염, 셀레늄산염의 페리하이드라이트에 대한 흡착 특성과 광물상 변화까지 고려한 페리하이드라이트의 산화음이온 제거 효능을 연구하였다. 실험 시 pH 4와 8에서 연구에 사용된 산화음이온들의 흡착은 pH 8에서 셀레늄산염을 제외하고 Langmuir와 Freundlich 두 흡착 모델과 잘 일치하였다. 각 산화음이온의 흡착량은 pH에 따른 표면 전하의 차이로 인하여 pH 4의 경우 pH 8보다 더 높았다. 흡착 량은 비산염, 크롬산염, 그리고 세레늄산염의 순서를 보여주었다. 이러한 흡착모델과 흡착량은 각 산화음이온의 흡착 시 페리하이드라이트 표면에서 일어나는 서로 다른 흡착 기작을 잘 대변한다. 이러한 흡착 특성은 광물상의 변화와도 밀접한 연관성이 있었다. pH 4에서는 침철석 혹은 적철석으로의 상변화를 보여주었으나, pH 8에서는 적철석으로의 상변화만이 관찰되었다. 산화음이온 종 중 비산염은 가장 높은 흡착력을 보여주며, 흡착 후 페리하이드라이트의 실험 기간 내 거의 상변화를 일으키지 않았다. 이와 달리 크롬산염과 셀레늄산염은 비산염에 비하여 광물상 변화가 더 빨랐으며 세 산화음이온 중 셀레늄산염의 지연 효과가 가장 낮았다. 페리하이드라이트는 비산염에 대하여 높은 흡착 능력과 낮은 상변화로 인하여 효과적인 제거가 가능하지만 다른 두 산화음이온 종은 낮은 흡착량과 추가적인 광물상 변화로 비산염에 비하여 제거 효과가 떨어지고 크롬산염의 경우 낮은 pH 환경에서 낮은 농도의 경우에에만 효율적인 제거가 가능할 것으로 판단된다. Ferrihydrite is an iron oxide mineral that is easily found in the natural environment, including acid mine drainage, and has a low crystallinity and high specific surface area, resulting in high reactivity with other ions, and can remove environmentally hazardous substances. However, because ferrihydrite is a metastable mineral, there is a possibility of releasing adsorbed ions by phase transformation to other minerals having low surface area and high crystallinity. In this study, the adsorption characteristics of arsenate, chromate, and selenate on ferrihydrite and the oxyanion removal efficiency of ferrihydrite were studied considering mineral phase transformation. At both pH 4 and 8, the adsorption of oxyanions used in the study were in good agreement with both Langmuir and Freundlich adsorption models except for selenate at pH 8. Due to the difference in surface charge according to pH, at pH 4 a higher amount of ions were adsorbed than at pH 8. The adsorption amount were in the order of arsenate, chromate, and selenate. These different adsorption models and adsorption amounts were due to different adsorption mechanisms for each oxyanions on the surface of ferrihydrite. These adsorption characteristics were closely related to changes in the mineral phase. At pH 4, a phase transformation to goethite or hematite was observed, but only a phase transformation to hematite was observed at pH 8. Among the oxyanion species on ferrihydrite, arsenate showed the highest adsorption capacity and hardly caused phase transformation during the experimental period after adsorption. Contrary to this, chromate and selenate showed faster mineral phase transformation than arsenate, and selenate had the lowest retardation effect among the three oxyanions. Ferrihydrite can effectively remove arsenate due to its high adsorption capacity and low phase transformation rate. However, the removal efficiency for other two oxyanions were low by the low adsorption amount and additional mineral phase transformation. For chromate, the efficient removal is expected only at low concentrations in low pH environments.

Adsorptive removal of wide range of pharmaceuticals and personal care products from water using bio-MOF-1 derived porous carbon

Bhadra, Biswa Nath,Jhung, Sung Hwa Elsevier 2018 Microporous and mesoporous materials Vol.270 No.-

<P><B>Abstract</B></P> <P>Bio-MOF-1 was pyrolyzed at 1000 °C to obtain highly porous carbon containing oxygen and nitrogen. The bio-MOF-derived carbons (BMDCs) were firstly applied in the adsorptive removal of four pharmaceuticals and personal care products (PPCPs), with a wide range of acidities or basicities, from water. BMDC-12 h, obtained by pyrolysis for 12 h, was very competitive in the adsorption of PPCPs, in terms of both adsorption rate and adsorbed quantity. More importantly, carbon showed the highest adsorption capacities for both basic atenolol (ATNL; 552 mg/g) and acidic clofibric acid (CLFA; 540 mg/g) among all the adsorbents reported so far. The recyclability of BMDC-12 h in adsorption was also confirmed (after solvent washing) by both adsorption and characterization (by nitrogen adsorption and FTIR analyses). The plausible adsorption mechanism was also suggested based on the effect of solution pH on the adsorbed amounts of PPCPs. Electrostatic interaction was the primary mechanism for the adsorption of ATNL. However, CLFA adsorption could be explained mainly by H-bonding, where CLFA was the acceptor for hydrogen donated from BMDC-12 h. BMDC-12 h was suggested as a promising adsorbent for the removal of a wide range of PPCPs from water, based on the remarkably high adsorption capacity, rapid adsorption, and stable reusability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Porous carbon derived from Bio-MOF-1 was applied in removal of PPCPs. </LI> <LI> Bio-MOF-1-derived carbon showed the highest atenolol and clofibric acid adsorption. </LI> <LI> The principal adsorption mechanisms could be defined for each adsorbate. </LI> <LI> The adsorbent showed perfect reusability for successive adsorptions in water. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Adsorption Behavior and Mechanism of Tripolyphosphate on Synthetic Goethite

Zhong, Yong,Sheng, Dandan,Xie, Fazhi,Li, Guolian,Li, Hui,Han, Xuan,Xie, Wenjie,Oh, Won-Chun The Korean Ceramic Society 2019 한국세라믹학회지 Vol.56 No.2

In order to study the transport behavior of tripolyphosphate (TPP) in aqueous solutions, the adsorption process of TPP on synthetic goethite, which exists stably in supergene environment, has been systematically studied. The adsorption properties under different conditions (pH, electrolyte presence, and temperature) were investigated. The adsorption of TPP in the presence of humic acid (HA)/fulvic acid (FA) has also been discussed in this paper. The results indicated that the adsorption capacity quickly increased within the first hour and equilibrium was reached within 24 h. The adsorption capacity decreased from 1.98 to 0.27 mg·g^-1 upon increasing the pH from 8.5 to 11.0, whereas the adsorption of TPP on goethite hardly changed with increasing electrolyte concentration. The results of analysis of the kinetic and isothermal models showed that the adsorption was more in accord with the pseudo second-order equation and Freundlich model. The adsorption capacity decreased obviously regardless of the order of addition of TPP, HA, and goethite. Subsequent addition of FA led to a large increase in the adsorption capacity, which might be attributed to the adsorption ability of FA. According to the predictions of the kinetic and isothermal models and the spectroscopic evidence (X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM)), the adsorption mechanism may be mainly based on surface complexation and physical adsorption.

Preparation and characterization of functionalized MWCNTs‑COOH with 3‑amino‑5‑phenylpyrazole as an adsorbent and optimization study using central composite design

Mobina Alimohammady,Mansour Jahangiri,Farhoush Kiani,Hasan Tahermansouri 한국탄소학회 2019 Carbon Letters Vol.29 No.1

Carboxylated multi-wall carbon nanotubes (MWCNTs-COOH) was functionalized with 3-amino-5-phenylpyrazole (MWCNTs- f) and characterized by FTIR, EDX, SEM, XRD and TGA. The MWCNTs-COOH and MWCNTs-f were used for the adsorption of Cd(II), Hg(II), and As(III) ions from aqueous solutions. Additionally, to study the influence of pH, adsorbent dose, and initial ions concentration on the adsorption process, the central composite design (CCD) was applied. The quadratic model was used for analysis of variance and indicated that adsorption of metal ions strongly depends on pH. Timedependent adsorption can be described by the pseudo-second-order kinetic model, and adsorption process was modeled by Langmuir isotherm for the adsorbents. Thermodynamic analysis showed that the adsorption of Cd(II), Hg(II) and As(III) ions were spontaneous and endothermic. Moreover, the competitive adsorption capacities of the heavy metal ions were slightly lower than noncompetitive ones. The same affinity order was observed under noncompetitive and competitive adsorption: As(III) > Cd(II) > Hg(II) in the case of MWCNTs-f. Desorption study revealed the favorable regeneration ability of adsorbents powders, even after three adsorption–desorption cycles.

Applicability of Composite Beads, Spent Coffee Grounds/Chitosan, for the Adsorptive Removal of Pb(II) from Aqueous Solutions

Choi, Hee-Jeong The Korean Society of Industrial and Engineering C 2019 공업화학 Vol.30 No.5

An experiment was conducted to evaluate the adsorptive removal of Pb(II) from an aqueous solution using a mixture of spent coffee grounds and chitosan on beads (CC-beads). Various parameters affecting the adsorption process of Pb(II) using CC-beads were investigated. Based on the experimental data, the adsorption kinetics and adsorption isotherms were analyzed for their adsorption rate, maximum adsorption capacity, adsorption energy and adsorption strength. Moreover, the entropy, enthalpy and free energy were also calculated by thermodynamic analysis. According to the FT-IR analysis, a CC-bead has a very suitable structure for easy heavy metal adsorption. The process of adsorbing Pb(II) using CC-beads was suitable for pseudo-second order kinetic and Langmuir model, with a maximum adsorption capacity of 163.51 (mg/g). The adsorption of Pb(II) using CC-beads was closer to chemical adsorption than physical adsorption. In addition, the adsorption of Pb(II) on CC-beads was exothermic and spontaneous in nature. CC-beads are economical because they are inexpensive and also the waste can be recycled, which is very significant in terms of the continuous circulation of resources. Thus, CC-beads can compete with other adsorbents.

Excellent toluene removal via adsorption by honeycomb adsorbents under high temperature and humidity conditions

Min-Whee Cho,Jongjin Kim,Jeong Min Jeong,Bongbeen Yim,Hyun-Jae Lee,Yoonjong Yoo 대한환경공학회 2020 Environmental Engineering Research Vol.25 No.2

Removal through adsorption is the most widely used and effective treatment method for volatile organic compounds (VOCs) in exhaust gases. However, at high temperatures and humidity, adsorption is competitive due to the presence of moisture and unsmooth physical adsorption thereby deteriorating adsorption performance. Therefore, water adsorption honeycomb (WAH) and VOCs adsorption honeycomb (VAH) were prepared to improve VOCs adsorption at high temperatures and humidity. Adsorbed toluene amounts on single honeycomb (SH), containing only VAH, and combined honeycomb (CH), containing WAH and VAH, were determined. Further, the toluene adsorption rates of honeycomb adsorbents mounted on rotary systems, VAH-single rotor (SR) and WAH/VAH-dual rotor (DR) were determined. Toluene adsorption by WAH/VAH-CH (inlet temperature: 40-50℃; absolute humidity: 28-83 gH₂O/kg-dry air) was 1.6 times that by VAH-SH, and the water adsorption efficiency of WAH/VAH-CH was 1.7 times that of VAH-SH. The adsorption/removal efficiency of the WAH/VAH-DR (inlet temperature: 45℃; absolute humidity: 37.5 gH₂O/kg-dry air) was 3% higher than that of VAH-SR. This indicates that the WAH at the rotor inlet selectively removed water, thereby improving the adsorption efficiency of the VAH at the outlet.

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>