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Adsorption
Journal Prestige (SJR): 0.703  Citation Impact (citeScore): 2 Number of Followers: 5  Hybrid journal (It can contain Open Access articles)ISSN (Print) 1572-8757 - ISSN (Online) 0929-5607 Published by Springer-Verlag  [2352 journals]
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- Correction to: Prediction of the sorption coefficient for the adsorption
of PAHs on MWCNT based on hybrid QSPR-molecular docking approach- Abstract: The original version of the article contained mistakes in equations. The corrected equations are given below.
PubDate: 2019-03-21
- Abstract: The original version of the article contained mistakes in equations. The corrected equations are given below.
- Application of titania based adsorbent for removal of acid, reactive and
direct dyes from textile effluents- Abstract: In the present study, the titania based adsorbent (Adsorbsia As500) was used for removal of three textile dyes such as C.I. Acid Red 18, C.I. Reactive Blue 21 and C.I. Direct Yellow 50 from aqueous solutions. The dye sorption was investigated by the batch and column methods. The experimental data were analyzed by the Langmuir, Freundlich and Temkin models of adsorption. Adsorbsia As500 exhibited the highest affinity towards DY50 as the monolayer sorption capacity were equal to 109.71 mg/g. The kinetic data obtained at different dyes concentrations were fitted to the pseudo-first order, pseudo-second order and Elovich equations. The dyes desorption experiments were investigated, too.
PubDate: 2019-03-21
- Abstract: In the present study, the titania based adsorbent (Adsorbsia As500) was used for removal of three textile dyes such as C.I. Acid Red 18, C.I. Reactive Blue 21 and C.I. Direct Yellow 50 from aqueous solutions. The dye sorption was investigated by the batch and column methods. The experimental data were analyzed by the Langmuir, Freundlich and Temkin models of adsorption. Adsorbsia As500 exhibited the highest affinity towards DY50 as the monolayer sorption capacity were equal to 109.71 mg/g. The kinetic data obtained at different dyes concentrations were fitted to the pseudo-first order, pseudo-second order and Elovich equations. The dyes desorption experiments were investigated, too.
- The first evaluation of the dynamic hydration number of hydrated ions
confined in mesoporous silica MCM-41- Abstract: Ion hydration in narrow pores is important in engineering, biology, and chemistry. The structures of hydrated ions confined in nanospaces have been studied by X-ray diffraction and X-ray absorption spectroscopy, and these confined hydrated ions have been found to have anomalous structures. On the other hand, the dynamic behavior has been studied only by molecular dynamics (MD) simulations, which have revealed the unique dynamics of hydration in nanospaces. However, no experimental studies of the dynamics of confined hydrated ions have been carried out. Here, we focus on the dynamic hydration number (nDHN) used in bulk solutions to evaluate the dynamic behavior of electrolyte solutions confined in nanospaces. To evaluate nDHN in nanospaces, we derived the molality dependence of the 2H spin–lattice relaxation time of D2O confined in nanospaces by considering the contribution of water bound to the pore surface. Next, we applied this to electrolyte solutions confined in mesoporous silica MCM-41 and evaluated nDHN. The absolute value of the dynamic hydration number in mesopores is significantly larger than that in the bulk solution; thus, the confinement effect drastically enhances the dynamic hydration properties (positive and negative hydration). This result supports the compressed hydration structure of ions with positive hydration character reported by previous structural and simulation studies. Our new approach for the evaluation of nDHN in nanospaces can be expected to give new insights in the investigation of electrolyte solutions confined in nanospaces from the viewpoint of the experimental verification of dynamic features of the hydration structure.
PubDate: 2019-03-21
- Abstract: Ion hydration in narrow pores is important in engineering, biology, and chemistry. The structures of hydrated ions confined in nanospaces have been studied by X-ray diffraction and X-ray absorption spectroscopy, and these confined hydrated ions have been found to have anomalous structures. On the other hand, the dynamic behavior has been studied only by molecular dynamics (MD) simulations, which have revealed the unique dynamics of hydration in nanospaces. However, no experimental studies of the dynamics of confined hydrated ions have been carried out. Here, we focus on the dynamic hydration number (nDHN) used in bulk solutions to evaluate the dynamic behavior of electrolyte solutions confined in nanospaces. To evaluate nDHN in nanospaces, we derived the molality dependence of the 2H spin–lattice relaxation time of D2O confined in nanospaces by considering the contribution of water bound to the pore surface. Next, we applied this to electrolyte solutions confined in mesoporous silica MCM-41 and evaluated nDHN. The absolute value of the dynamic hydration number in mesopores is significantly larger than that in the bulk solution; thus, the confinement effect drastically enhances the dynamic hydration properties (positive and negative hydration). This result supports the compressed hydration structure of ions with positive hydration character reported by previous structural and simulation studies. Our new approach for the evaluation of nDHN in nanospaces can be expected to give new insights in the investigation of electrolyte solutions confined in nanospaces from the viewpoint of the experimental verification of dynamic features of the hydration structure.
- Continuous-flow separation of cesium ion by ammonium molybdophosphate
immobilized in a silica microhoneycomb (AMP-SMH)- Abstract: Monolithic cesium ion (Cs+) adsorbents were synthesized via the directional freezing of a silica hydrogel containing ammonium molybdophosphate (AMP) particles, followed by freeze-drying. The adsorbents have a honeycomb-like structure with nearly straight microchannels (approximately 21 µm in diameter) running through them and with AMP particles partially embedded intact within the channel walls. Because of its honeycomb-like structure, the adsorbent, denoted as AMP silica microhoneycomb (AMP-SMH), achieves a significantly lower pressure drop than a typical column packed with spherical particles with similar diffusion path lengths for Cs+ when water was passed through it (about 35-times lower). Comparison of breakthrough curves between the AMP-SMH and columns packed with particles by numerical simulation also indicates that AMP-SMH shows shorter length of unused bed values. These results demonstrate that the AMP-SMH shows a high performance in the continuous separation of Cs+ due to their unique microhoneycomb structure.
PubDate: 2019-03-19
- Abstract: Monolithic cesium ion (Cs+) adsorbents were synthesized via the directional freezing of a silica hydrogel containing ammonium molybdophosphate (AMP) particles, followed by freeze-drying. The adsorbents have a honeycomb-like structure with nearly straight microchannels (approximately 21 µm in diameter) running through them and with AMP particles partially embedded intact within the channel walls. Because of its honeycomb-like structure, the adsorbent, denoted as AMP silica microhoneycomb (AMP-SMH), achieves a significantly lower pressure drop than a typical column packed with spherical particles with similar diffusion path lengths for Cs+ when water was passed through it (about 35-times lower). Comparison of breakthrough curves between the AMP-SMH and columns packed with particles by numerical simulation also indicates that AMP-SMH shows shorter length of unused bed values. These results demonstrate that the AMP-SMH shows a high performance in the continuous separation of Cs+ due to their unique microhoneycomb structure.
- Removal of Cu(II) ions from aqueous solutions using petroleum coke-derived
microporous carbon: investigation of adsorption equilibrium and kinetics- Abstract: Petroleum coke (PC)-derived porous carbons were developed through chemical activation using KOH and applied to adsorb Cu(II) ions from aqueous solutions. The effects of KOH/PC mass ratio and activation temperature on the preparation and physical properties of porous carbon were studied. Also, the effects of the initial solution pH, contact time, operating temperature, dosage of adsorbent, and initial Cu(II) concentration on adsorption were investigated in detail. A maximum Cu(II) ion adsorption capacity of 89.85 mg g−1 was attained at 30 °C using PCK3-450, the porous carbon sample prepared using a KOH/PC mass ratio of 3:1 at 450 °C. Adsorption isotherms were analyzed using the Langmuir, Freundlich, and Temkin models, and the experimental data fit well with the Freundlich model. Pseudo first-order, pseudo second-order, Elovich, and intra-particle diffusion models were used to describe the adsorption kinetics, and the rate of adsorption conformed to the pseudo second-order kinetic model. The activation energy of Cu(II) ion adsorption on PCK3-450 was estimated at 29.61 kJ mol−1, and thermodynamic parameters were discussed. The porous carbon adsorbents developed in this study are inexpensive and effective for Cu(II) ion removal from aqueous solutions.
PubDate: 2019-03-19
- Abstract: Petroleum coke (PC)-derived porous carbons were developed through chemical activation using KOH and applied to adsorb Cu(II) ions from aqueous solutions. The effects of KOH/PC mass ratio and activation temperature on the preparation and physical properties of porous carbon were studied. Also, the effects of the initial solution pH, contact time, operating temperature, dosage of adsorbent, and initial Cu(II) concentration on adsorption were investigated in detail. A maximum Cu(II) ion adsorption capacity of 89.85 mg g−1 was attained at 30 °C using PCK3-450, the porous carbon sample prepared using a KOH/PC mass ratio of 3:1 at 450 °C. Adsorption isotherms were analyzed using the Langmuir, Freundlich, and Temkin models, and the experimental data fit well with the Freundlich model. Pseudo first-order, pseudo second-order, Elovich, and intra-particle diffusion models were used to describe the adsorption kinetics, and the rate of adsorption conformed to the pseudo second-order kinetic model. The activation energy of Cu(II) ion adsorption on PCK3-450 was estimated at 29.61 kJ mol−1, and thermodynamic parameters were discussed. The porous carbon adsorbents developed in this study are inexpensive and effective for Cu(II) ion removal from aqueous solutions.
- Insight into adsorbate–adsorbent interactions between aromatic
pharmaceutical compounds and activated carbon: equilibrium isotherms and
thermodynamic analysis- Abstract: The adsorption of phenol, salicylic acid and methylparaben on activated carbon is carried out using solvents with different pH, the adsorption and calorimetric data are analyzed in order to determine the effect of the substituent on the adsorption capacity. The adsorption isotherms were adjusted to the Langmuir model, which allows to assume the formation of specific adsorbate–adsorbent interactions between groups present in the adsorbate molecules, the substituents of the aromatic ring, and chemical groups on the activated carbon. According to the Lagmuir model the formation of specific interactions generates the monolayer adsorption so it is possible to correlate the adsorption capacity with changes in the interactions present in the system. It was determined that the adsorption process is disadvantaged at extremes pH values. From the Langmuir model it was calculated that the maximum adsorbed capacity of phenol and methylparaben in activated carbon granular activated carbon using water as solvent was 3.11 and 1.58 mmol g−1 respectively. The adsorption process of salicylic acid does not adjust to the Langmuir model due to the presence of different interactions that includes repulsion forces. From thermodynamic calculations and calorimetric data, it was determined that the immersion enthalpies vary between − 8.33 and − 59.3 J g−1, while the change in the enthalpy associated with interactions substituents-activated carbon is between − 15.1 and 6.40 J g−1 for the carboxylic acid and between − 0.50 and 20.0 J g−1 for the ester group.
PubDate: 2019-03-15
- Abstract: The adsorption of phenol, salicylic acid and methylparaben on activated carbon is carried out using solvents with different pH, the adsorption and calorimetric data are analyzed in order to determine the effect of the substituent on the adsorption capacity. The adsorption isotherms were adjusted to the Langmuir model, which allows to assume the formation of specific adsorbate–adsorbent interactions between groups present in the adsorbate molecules, the substituents of the aromatic ring, and chemical groups on the activated carbon. According to the Lagmuir model the formation of specific interactions generates the monolayer adsorption so it is possible to correlate the adsorption capacity with changes in the interactions present in the system. It was determined that the adsorption process is disadvantaged at extremes pH values. From the Langmuir model it was calculated that the maximum adsorbed capacity of phenol and methylparaben in activated carbon granular activated carbon using water as solvent was 3.11 and 1.58 mmol g−1 respectively. The adsorption process of salicylic acid does not adjust to the Langmuir model due to the presence of different interactions that includes repulsion forces. From thermodynamic calculations and calorimetric data, it was determined that the immersion enthalpies vary between − 8.33 and − 59.3 J g−1, while the change in the enthalpy associated with interactions substituents-activated carbon is between − 15.1 and 6.40 J g−1 for the carboxylic acid and between − 0.50 and 20.0 J g−1 for the ester group.
- Mathematical model for the encapsulation of Alanine amino acid inside a
single-walled carbon nanotube- Abstract: Carbon nanotubes play a significant role in facilitating and controlling the transportation of drugs and bio-molecules through their internal and external surfaces. Carbon nanotubes are also selective nano-devices because of their outstanding properties and huge potential use in many bio-medical and drug delivery applications. The proposed model aims to investigate the encapsulation of Alanine molecule inside a single-walled carbon nanotube, and to determine the minimum energy which is arising from the Alanine interacting with single-walled carbon nanotubes with variant radii r. We consider two possible structures as models of Alanine molecule which are a spherical shell as a continuum configuration and discrete configuration modelled as comprising three components: the linear molecule, cylindrical group, and CH3 molecule as a sphere, all interacting with infinite cylindrical single-walled carbon nanotube. The adsorption of Alanine amino acid and magnitude of total energy for each orientation calculated based on the nanotube radius r and the orientation angle \(\phi\) which the amino acid makes with central axis of the cylindrical nanotube. Our results indicate that the Alanine molecule encapsulated inside the nanotubes of radius greater than 3.75 Å, which are in excellent agreement with recent findings.
PubDate: 2019-03-14
- Abstract: Carbon nanotubes play a significant role in facilitating and controlling the transportation of drugs and bio-molecules through their internal and external surfaces. Carbon nanotubes are also selective nano-devices because of their outstanding properties and huge potential use in many bio-medical and drug delivery applications. The proposed model aims to investigate the encapsulation of Alanine molecule inside a single-walled carbon nanotube, and to determine the minimum energy which is arising from the Alanine interacting with single-walled carbon nanotubes with variant radii r. We consider two possible structures as models of Alanine molecule which are a spherical shell as a continuum configuration and discrete configuration modelled as comprising three components: the linear molecule, cylindrical group, and CH3 molecule as a sphere, all interacting with infinite cylindrical single-walled carbon nanotube. The adsorption of Alanine amino acid and magnitude of total energy for each orientation calculated based on the nanotube radius r and the orientation angle \(\phi\) which the amino acid makes with central axis of the cylindrical nanotube. Our results indicate that the Alanine molecule encapsulated inside the nanotubes of radius greater than 3.75 Å, which are in excellent agreement with recent findings.
- Vacuum pressure swing adsorption system for N 2 /CO 2 separation in
consideration of unstable feed concentration- Abstract: In this study, an efficient PID control system has been designed for a vacuum pressure swing adsorption (VPSA) process which used silica gel to capture CO2 from dry flue gas. Changes of CO2 composition in feed gas are set as disturbances and vary from 12.0 to 15.0% to make simulation work more closely to reality. Meanwhile, adsorption step time duration was set to change consistently according to the feedback of CO2 purity in product. PID control strategy built in software gPROMS is employed in this paper. The competence of the control system is firstly analyzed by a transient impulse of CO2 content in feed gas (15.0% dropped to 12.0%). Then random pulse is added to test the ability of the control system to reject the unknown disturbances and track the set point. Detailed changes in bed under open and closed-loop are listed and made comparisons. Results demonstrate that the model shows an enhanced performance in the presence of random disturbances under closed-loop control compared with the open-loop operation. And this proves that closed-loop feedback PID control can be used to improve the CO2 capture of VPSA process operations.
PubDate: 2019-03-14
- Abstract: In this study, an efficient PID control system has been designed for a vacuum pressure swing adsorption (VPSA) process which used silica gel to capture CO2 from dry flue gas. Changes of CO2 composition in feed gas are set as disturbances and vary from 12.0 to 15.0% to make simulation work more closely to reality. Meanwhile, adsorption step time duration was set to change consistently according to the feedback of CO2 purity in product. PID control strategy built in software gPROMS is employed in this paper. The competence of the control system is firstly analyzed by a transient impulse of CO2 content in feed gas (15.0% dropped to 12.0%). Then random pulse is added to test the ability of the control system to reject the unknown disturbances and track the set point. Detailed changes in bed under open and closed-loop are listed and made comparisons. Results demonstrate that the model shows an enhanced performance in the presence of random disturbances under closed-loop control compared with the open-loop operation. And this proves that closed-loop feedback PID control can be used to improve the CO2 capture of VPSA process operations.
- Nitrogen adsorption at ca . 77.4 K on partially hydrated and
anhydrous α-Al 2 O 3- Abstract: N2 adsorption isotherms at ca. 77 K on macroporous α-Al2O3 have been measured and analyzed in the frameworks of the classic thermodynamic approach, with independent experimental data obtained by means of SEM-EDX, XRD, TGA, helium pycnometry, and mercury porosimetry taken into account. It is shown, that presence of adsorbed water considerably influences N2 adsorption, which gradually increases with temperature of the degas treatment. Simultaneously, the shape of the isotherms has a trend to change from Type II to Type VI, that assumes changing of adsorption mechanism from progressive increasing of the adsorbed layer thickness towards layer-by-layer adsorption. Corrected and smoothed isotherms are presented in the tabular form as reference for subsequent more comprehensive analysis using molecular statistical approaches.
PubDate: 2019-03-13
- Abstract: N2 adsorption isotherms at ca. 77 K on macroporous α-Al2O3 have been measured and analyzed in the frameworks of the classic thermodynamic approach, with independent experimental data obtained by means of SEM-EDX, XRD, TGA, helium pycnometry, and mercury porosimetry taken into account. It is shown, that presence of adsorbed water considerably influences N2 adsorption, which gradually increases with temperature of the degas treatment. Simultaneously, the shape of the isotherms has a trend to change from Type II to Type VI, that assumes changing of adsorption mechanism from progressive increasing of the adsorbed layer thickness towards layer-by-layer adsorption. Corrected and smoothed isotherms are presented in the tabular form as reference for subsequent more comprehensive analysis using molecular statistical approaches.
- Density functional theory study towards investigating the adsorption
properties of the γ-Fe 2 O 3 nanoparticles as a nanocarrier for delivery
of Flutamide anticancer drug- Abstract: In this work, we perform density functional theory studies to comprehend the structure and energetics of the interaction of γ-Fe2O3 nanoparticles with Flutamide (FLU) anticancer drug. Quantum mechanics calculations by two methods including B3LYP/6-31G** and M06-2X/6-31G** have been used to obtain the details of energetic, geometric, and electronic features of the drug molecule interacting with the surface of the maghemite nanoparticles in water solution. The obtained calculations of M06-2X/6-31G** method approved the observation of the strongest adsorption within the hydrogen bond interactions between two considered molecules are predominate, while the adsorption process of drug on the nanoparticles in B3LYP/6-31G** method is endothermic and hence, the adsorbed structures are unstable. The quantum theory of atoms in molecules analysis illustrates closed shell interactions between the drug molecule and the γ-Fe2O3 nanoparticles. The natural bond orbital analysis demonstrated that the drug molecule has the ability to be adsorbed on the nanoparticle surface with the transfer of charge from the drug molecule to maghemite nanoparticles. Moreover, quantum mechanical descriptors within the drug-nanoparticles systems were investigated and it was implied that binding of FLU molecule with γ-Fe2O3 nanoparticles is thermodynamically favorable. Therefore, γ-Fe2O3 nanoparticles can be introduced as efficient systems for the delivery of the drug molecule.
PubDate: 2019-03-13
- Abstract: In this work, we perform density functional theory studies to comprehend the structure and energetics of the interaction of γ-Fe2O3 nanoparticles with Flutamide (FLU) anticancer drug. Quantum mechanics calculations by two methods including B3LYP/6-31G** and M06-2X/6-31G** have been used to obtain the details of energetic, geometric, and electronic features of the drug molecule interacting with the surface of the maghemite nanoparticles in water solution. The obtained calculations of M06-2X/6-31G** method approved the observation of the strongest adsorption within the hydrogen bond interactions between two considered molecules are predominate, while the adsorption process of drug on the nanoparticles in B3LYP/6-31G** method is endothermic and hence, the adsorbed structures are unstable. The quantum theory of atoms in molecules analysis illustrates closed shell interactions between the drug molecule and the γ-Fe2O3 nanoparticles. The natural bond orbital analysis demonstrated that the drug molecule has the ability to be adsorbed on the nanoparticle surface with the transfer of charge from the drug molecule to maghemite nanoparticles. Moreover, quantum mechanical descriptors within the drug-nanoparticles systems were investigated and it was implied that binding of FLU molecule with γ-Fe2O3 nanoparticles is thermodynamically favorable. Therefore, γ-Fe2O3 nanoparticles can be introduced as efficient systems for the delivery of the drug molecule.
- Fe 2+ adsorption on iron oxide: the importance of the redox potential of
the adsorption system- Abstract: We have demonstrated that the redox potential of the solution containing an inert electrolyte, ferrous ions, and metal oxide allows a much better understanding of the process of Fe(II) adsorption on oxide with the increase of pH. We tested two oxides: γ-Fe2O3 (maghemite) and TiO2 (the mixture of anatase and rutile). For both of them, we determined proton surface charge, Fe(II) uptake curves, electrokinetic potential, and redox potential in solution. The all measured quantities except the last, behaved in an almost identical manner for ferric oxide and titanium dioxide. The redox potential strongly depends on the pH of the solution and stabilizes when the adsorption process is finished (pH above 6). We observed that for the solution consisting only of 0.2 mM Fe(II) and 0.1 KCl the redox potential in the pH range 3–6 can be expressed by the formula: \(Eh[mV]=1120 - 3 \times 59 \times {\text{pH}} - 59 \times \log (a\_{\text{Fe}}({\text{II}}))\) .
PubDate: 2019-03-13
- Abstract: We have demonstrated that the redox potential of the solution containing an inert electrolyte, ferrous ions, and metal oxide allows a much better understanding of the process of Fe(II) adsorption on oxide with the increase of pH. We tested two oxides: γ-Fe2O3 (maghemite) and TiO2 (the mixture of anatase and rutile). For both of them, we determined proton surface charge, Fe(II) uptake curves, electrokinetic potential, and redox potential in solution. The all measured quantities except the last, behaved in an almost identical manner for ferric oxide and titanium dioxide. The redox potential strongly depends on the pH of the solution and stabilizes when the adsorption process is finished (pH above 6). We observed that for the solution consisting only of 0.2 mM Fe(II) and 0.1 KCl the redox potential in the pH range 3–6 can be expressed by the formula: \(Eh[mV]=1120 - 3 \times 59 \times {\text{pH}} - 59 \times \log (a\_{\text{Fe}}({\text{II}}))\) .
- Experimental evaluation of simulated moving bed reactor for
transesterification reaction synthesis of glycol ether ester- Abstract: This work presents an experimental evaluation of multi-column simulated moving bed reactor (SMBR) technology for transesterification of glycol ether ester for the first time. An industrially relevant solvent, propylene glycol methyl ether acetate (DOWANOL™ PMA) was produced using a laboratory-scale SMBR unit packed with a base catalyst. The catalyst selected in this study, a Type-II anion exchange resin, was found to be resistant to deactivation through our experimental runs. To design the SMBR process, single-column experiments were first carried out to develop a mathematical model and estimate model parameters. Using this model, the optimal SMBR process was found by a multi-objective optimization technique to maximize the productivity while achieving high conversions. The optimal operating conditions found in this manner were implemented in the lab-scale SMB unit, which achieved conversions ranging from 47.3 to 57.7%. Furthermore, using the experimental data obtained from these experimental runs, the prediction of the model was improved via Tikhonov regularization, which was successfully validated in an additional run at an even higher conversion of 74.6%.
PubDate: 2019-03-11
- Abstract: This work presents an experimental evaluation of multi-column simulated moving bed reactor (SMBR) technology for transesterification of glycol ether ester for the first time. An industrially relevant solvent, propylene glycol methyl ether acetate (DOWANOL™ PMA) was produced using a laboratory-scale SMBR unit packed with a base catalyst. The catalyst selected in this study, a Type-II anion exchange resin, was found to be resistant to deactivation through our experimental runs. To design the SMBR process, single-column experiments were first carried out to develop a mathematical model and estimate model parameters. Using this model, the optimal SMBR process was found by a multi-objective optimization technique to maximize the productivity while achieving high conversions. The optimal operating conditions found in this manner were implemented in the lab-scale SMB unit, which achieved conversions ranging from 47.3 to 57.7%. Furthermore, using the experimental data obtained from these experimental runs, the prediction of the model was improved via Tikhonov regularization, which was successfully validated in an additional run at an even higher conversion of 74.6%.
- Investigation of computational upscaling of adsorption of SO 2 and CO 2 in
fixed bed columns- Abstract: Fixed bed adsorption is an economical method of removing harmful gases, such as SO2 and CO2, from industrial flue gas. It is possible to reduce the cost and environmental impact of fixed bed adsorption by repurposing waste materials to be used as adsorbents, such as semi-coke derived from oil shale, a possible alternative to fossil fuels. Fixed bed adsorption systems are difficult and time consuming to characterize experimentally, especially on large scales. Computational fluid dynamics (CFD) can expand researchers understaning of how these systems are affected by material selection and operating conditions. This study uses CFD to characterize fixed bed adsorption of SO2 and CO2. The research primarily focuses on SO2 adsorption on semi-coke, with an extension to CO2 adsorption on commercial carbon. The CFD modeling was able to describe the amount of the pollutants each material was able to adsorb over time based on a variety of inputs on a larger scale than experimental research. The model was further able to give more detailed comparisons of materials and operating conditions than the experiments, particularly the SO2 and semi-coke system.
PubDate: 2019-03-09
- Abstract: Fixed bed adsorption is an economical method of removing harmful gases, such as SO2 and CO2, from industrial flue gas. It is possible to reduce the cost and environmental impact of fixed bed adsorption by repurposing waste materials to be used as adsorbents, such as semi-coke derived from oil shale, a possible alternative to fossil fuels. Fixed bed adsorption systems are difficult and time consuming to characterize experimentally, especially on large scales. Computational fluid dynamics (CFD) can expand researchers understaning of how these systems are affected by material selection and operating conditions. This study uses CFD to characterize fixed bed adsorption of SO2 and CO2. The research primarily focuses on SO2 adsorption on semi-coke, with an extension to CO2 adsorption on commercial carbon. The CFD modeling was able to describe the amount of the pollutants each material was able to adsorb over time based on a variety of inputs on a larger scale than experimental research. The model was further able to give more detailed comparisons of materials and operating conditions than the experiments, particularly the SO2 and semi-coke system.
- Influence of mechanochemical treatment on thermal and structural
properties of silica–collagen and hydroxyapatite–collagen composites- Abstract: The paper presents the results of research on a series of composite materials based on hydroxyapatite, silica gel and collagen as biologically active substances. Their preparation was made using mechanical energy in accordance with the principles of “green chemistry”. Mechanochemical treatment was conducted in a planetary mill with different rotations of milling (200 and 400 rpm) and various periods of time (30, 60 and 120 min). Temperature and pressure changes generated during the mechanochemical treatment were recorded. The obtained composites were analyzed using the low-temperature nitrogen adsorption/desorption method and thermal analysis (TG/DTA). Very interesting and promising results were obtained encouraging further research in this area.
PubDate: 2019-03-08
- Abstract: The paper presents the results of research on a series of composite materials based on hydroxyapatite, silica gel and collagen as biologically active substances. Their preparation was made using mechanical energy in accordance with the principles of “green chemistry”. Mechanochemical treatment was conducted in a planetary mill with different rotations of milling (200 and 400 rpm) and various periods of time (30, 60 and 120 min). Temperature and pressure changes generated during the mechanochemical treatment were recorded. The obtained composites were analyzed using the low-temperature nitrogen adsorption/desorption method and thermal analysis (TG/DTA). Very interesting and promising results were obtained encouraging further research in this area.
- Adsorption mechanism of poly(vinyl alcohol) on the surfaces of synthetic
zeolites: sodalite, Na-P1 and Na-A- Abstract: The structure of poly(vinyl alcohol)—PVA layers adsorbed on the synthetic zeolites surfaces was determined. Three zeolites: sodalite, Na-P1 and Na-A were obtained using hydrothermal conversion of fly ash with aqueous sodium hydroxide. The effects of solution pH and zeolite type on the adsorption mechanism of the polymer were examined. The analysis of the results obtained by means of spectrophotometric and microelectrophoretic measurements as well as potentiometric titrations enabled description of interfacial behaviour of adsorbed macromolecules. It was shown that the presence of poly(vinyl alcohol) layers modifies the surface properties of applied zeolites. The evidence of this are changes in the surface charge density and zeta potential of solid particles observed in the polymer presence. Moreover the PVA chains exhibit different adsorption affinity for the examined zeolites depending mainly on the mean pore size of these aluminosilicates which is very important for penetration of internal zeolite structure by polymeric macromolecules.
PubDate: 2019-03-07
- Abstract: The structure of poly(vinyl alcohol)—PVA layers adsorbed on the synthetic zeolites surfaces was determined. Three zeolites: sodalite, Na-P1 and Na-A were obtained using hydrothermal conversion of fly ash with aqueous sodium hydroxide. The effects of solution pH and zeolite type on the adsorption mechanism of the polymer were examined. The analysis of the results obtained by means of spectrophotometric and microelectrophoretic measurements as well as potentiometric titrations enabled description of interfacial behaviour of adsorbed macromolecules. It was shown that the presence of poly(vinyl alcohol) layers modifies the surface properties of applied zeolites. The evidence of this are changes in the surface charge density and zeta potential of solid particles observed in the polymer presence. Moreover the PVA chains exhibit different adsorption affinity for the examined zeolites depending mainly on the mean pore size of these aluminosilicates which is very important for penetration of internal zeolite structure by polymeric macromolecules.
- Evaluation of simplified pressure swing adsorption cycles for bio-methane
production- Abstract: Pressure swing adsorption (PSA) is a mature technique for biogas upgrading. However, it constitutes the most expensive step to obtain fuel-quality bio-methane, particularly in small-scale units. To reduce the cost of upgrading in small-scale plants, we have evaluated different PSA cycles with two and three columns (less than commercial units). An equalization tank was used to perform one asynchronous pressure equalization step and keep the process fed continuous even in the case of using two columns. The effect of the purge step was also evaluated. Carbon molecular sieve was used as adsorbent. The feed composition was 40% CO2/60% CH4 and pressure swinging between 5 and 0.1 bar in the adsorption and blowdown steps, respectively. Four performance indicators (methane purity and recovery, productivity and energy consumption) were used to evaluate the PSA cycles. The mathematical model could predict the experimental PSA performance. Bio-methane with purity higher than 97.5% (specification) and recovery higher than 90% was obtained experimentally using a PSA with two columns and an equalization tank. When a third column is used (implementing an additional pressure equalization), the recovery increases in approx. 4% showing the importance of pressure equalization to reduce the methane slip.
PubDate: 2019-03-07
- Abstract: Pressure swing adsorption (PSA) is a mature technique for biogas upgrading. However, it constitutes the most expensive step to obtain fuel-quality bio-methane, particularly in small-scale units. To reduce the cost of upgrading in small-scale plants, we have evaluated different PSA cycles with two and three columns (less than commercial units). An equalization tank was used to perform one asynchronous pressure equalization step and keep the process fed continuous even in the case of using two columns. The effect of the purge step was also evaluated. Carbon molecular sieve was used as adsorbent. The feed composition was 40% CO2/60% CH4 and pressure swinging between 5 and 0.1 bar in the adsorption and blowdown steps, respectively. Four performance indicators (methane purity and recovery, productivity and energy consumption) were used to evaluate the PSA cycles. The mathematical model could predict the experimental PSA performance. Bio-methane with purity higher than 97.5% (specification) and recovery higher than 90% was obtained experimentally using a PSA with two columns and an equalization tank. When a third column is used (implementing an additional pressure equalization), the recovery increases in approx. 4% showing the importance of pressure equalization to reduce the methane slip.
- Influence of bridged monomer on porosity and sorption properties of
mesoporous silicas functionalized with diethylenetriamine groups- Abstract: Mesoporous organosilicas functionalized simultaneously with both pendant amine groups and ethylene/phenylene bridges, were synthesized to evaluate the effect of the bridges incorporated in the silica framework on the structure, porosity and adsorption properties of final materials. It turned out that the presence of the bridges enhanced the formation of porosity but adversely affected the efficiency of amination. DFT theoretical calculation showed that the amine groups can be partially bonded by phenyl groups of the bridges. The obtained materials were tested as sorbents of diclofenac, which is considered as one of the most prominent hazardous pharmaceuticals. High uptakes of diclofenac reaching 842 mg g−1 proved that the obtained materials could be applied for removal of drugs from waters and wastewaters, particularly when high concentrations of pharmaceutical are considered. For the phenylene bridged-based materials the diclofenac adsorption occurs only in the pores while for the others also on the external surface as indicated by different diclofenac desorption kinetics—this observation can be used to modulate the releasing profiles of drugs via proper design of the surface.
PubDate: 2019-03-07
- Abstract: Mesoporous organosilicas functionalized simultaneously with both pendant amine groups and ethylene/phenylene bridges, were synthesized to evaluate the effect of the bridges incorporated in the silica framework on the structure, porosity and adsorption properties of final materials. It turned out that the presence of the bridges enhanced the formation of porosity but adversely affected the efficiency of amination. DFT theoretical calculation showed that the amine groups can be partially bonded by phenyl groups of the bridges. The obtained materials were tested as sorbents of diclofenac, which is considered as one of the most prominent hazardous pharmaceuticals. High uptakes of diclofenac reaching 842 mg g−1 proved that the obtained materials could be applied for removal of drugs from waters and wastewaters, particularly when high concentrations of pharmaceutical are considered. For the phenylene bridged-based materials the diclofenac adsorption occurs only in the pores while for the others also on the external surface as indicated by different diclofenac desorption kinetics—this observation can be used to modulate the releasing profiles of drugs via proper design of the surface.
- Heat capacity and heat of adsorption at orientational phase transition in
nitrogen monolayer on graphite- Abstract: In this paper, we report a simulation study of the effect of the herringbone orientational phase transition on the isosteric heat of adsorption and the heat capacity of the nitrogen adsorption monolayer on graphite surface. We use the previously proposed regression equations of state for phases with the short- and long-ranged orientational ordering (Ustinov et al. in J Phys Chem C 122:2897–2908, 2018). The proposed approach allows one to give an exhaustive thermodynamic description of the isobaric phase transition without direct estimation of the chemical potential, using only the pVT data obtained in a canonical Monte Carlo simulation. The herringbone orientational phase transition is indicated by a peak in the temperature dependence of the heat capacity. Its height and shape is close to those observed experimentally. In addition, the heat spike is observed on the isosteric heat curves near the transition region. It decreases with increasing temperature and completely disappears at a temperature close to the melting point in the gas-crystal system. A combined analysis of the heat capacity and isosteric heat of adsorption demonstrates that the nitrogen monolayer on graphite surface has similar features inherent in a three-dimensional system and, therefore, the translational and rotational degrees of freedom normal to the surface are involved in the mechanism of the long-to-short-ranged orientational transition.
PubDate: 2019-03-06
- Abstract: In this paper, we report a simulation study of the effect of the herringbone orientational phase transition on the isosteric heat of adsorption and the heat capacity of the nitrogen adsorption monolayer on graphite surface. We use the previously proposed regression equations of state for phases with the short- and long-ranged orientational ordering (Ustinov et al. in J Phys Chem C 122:2897–2908, 2018). The proposed approach allows one to give an exhaustive thermodynamic description of the isobaric phase transition without direct estimation of the chemical potential, using only the pVT data obtained in a canonical Monte Carlo simulation. The herringbone orientational phase transition is indicated by a peak in the temperature dependence of the heat capacity. Its height and shape is close to those observed experimentally. In addition, the heat spike is observed on the isosteric heat curves near the transition region. It decreases with increasing temperature and completely disappears at a temperature close to the melting point in the gas-crystal system. A combined analysis of the heat capacity and isosteric heat of adsorption demonstrates that the nitrogen monolayer on graphite surface has similar features inherent in a three-dimensional system and, therefore, the translational and rotational degrees of freedom normal to the surface are involved in the mechanism of the long-to-short-ranged orientational transition.
- Complete analysis of phase diversity of the simplest adsorption model of a
binary gas mixture for all sets of undirected interactions between nearest
neighbors- Abstract: In this paper, a complete analysis of the phase diagrams of the model of adsorption of a binary gas mixture on a square lattice in the ground state for all sets of near undirected interactions between particles was performed. Using the principle of minimum of a large thermodynamic potential in a stable phase, the partition of the model parameter space (the energies of lateral interactions) into regions differing by the type of the phase diagram was constructed. Also, for some regions, partial and total coverages as functions of chemical potentials of the gases were calculated through transfer-matrix method and presented. The work is an extension of the work (Fefelov in Phys Chem Chem Phys 20(15): 10359–10368, 2018).
PubDate: 2019-03-05
- Abstract: In this paper, a complete analysis of the phase diagrams of the model of adsorption of a binary gas mixture on a square lattice in the ground state for all sets of near undirected interactions between particles was performed. Using the principle of minimum of a large thermodynamic potential in a stable phase, the partition of the model parameter space (the energies of lateral interactions) into regions differing by the type of the phase diagram was constructed. Also, for some regions, partial and total coverages as functions of chemical potentials of the gases were calculated through transfer-matrix method and presented. The work is an extension of the work (Fefelov in Phys Chem Chem Phys 20(15): 10359–10368, 2018).
- Ambiguity in actual amount adsorbed
- Abstract: It is demonstrated that various combinations of models describing the adsorbed phase volume and the actual amount adsorbed (AAA) can be used to describe the experimental Gibbsian surface excess isotherm data for adsorption of a pure gas. Thus, the resulting AAA isotherm and the other adsorptive properties estimated by this approach can be ambiguous and artificial.
PubDate: 2019-03-05
- Abstract: It is demonstrated that various combinations of models describing the adsorbed phase volume and the actual amount adsorbed (AAA) can be used to describe the experimental Gibbsian surface excess isotherm data for adsorption of a pure gas. Thus, the resulting AAA isotherm and the other adsorptive properties estimated by this approach can be ambiguous and artificial.
