Single Adsorption Isotherms Research Articles

A statistical physics-based physicochemical study of L-phenylalanine adsorption on activated carbon.

In this comparative study of the adsorption of L-phenylalanine (L-Phe) on two modified low-activated carbons (ACK and ACZ) at four temperatures (293-313K), steric and energetic characteristics of adsorption were investigated. An advanced statistical physics multilayer model involving single-layer and double-layer adsorption scenarios was developed to interpret the L-Phe adsorption phenomenon. Modeling results indicate that two and three L-Phe layers were arranged depending on the tested adsorption systems. The estimated number of L-Phe molecules per leading adsorption site varied from 1.71 to 2.09 and from 1.76 to 1.86 for systems L-Phe-ACK and L-Phe-ACZ, respectively. The results show that a multimolecular adsorption mechanism might connect this amino acid molecule on ACZ and ACK surfaces in a non-parallel location. These parameters changed as follows, according to the adsorbed quantity at saturation analysis: Qasat (L-Phe-ACK) ˃ Qasat (L-Phe-ACZ). This indicates that ACK material was more efficient and valuable for L-Phe adsorption than ACZ. It was also shown that the adsorption capacity decreases as the temperature increases, proving the exothermicity of the adsorption process. This analytical substantiation is confirmed by calculating the binding energies, suggesting the occurrence of physical bonds between L-Phe amino acid molecules and ACK/ACZ binding sites and among L-Phe-L-Phe molecules. Pore size distribution was interpreted and calculated by applying the Kelvin theory to data from single adsorption isotherms. All used temperatures depicted a distribution of pores below 2nm. The docking analysis involving L-Phe and the ACZ and ACK adsorbents reveal a significant resemblance in how receptors detect ligands. Consequently, the findings from the docking process confirm that the calculated binding affinities fall within the spectrum of adsorption energy. This study analyzed the adsorption capacity of the L-Phe through a model proposed by statistical physics formalism. Molecular docking was used to determine the various types of interactions between the two activated carbons. Two aspects, including orientation of L-Phe on the site, number of molecules per site n, interaction energy, density of receptor site, and adsorption capacity, were discussed to elucidate the influence of activation on the two adsorbents.

Design, preparation, and performance of different adsorbents based on carboxymethyl chitosan/sodium alginate hydrogel beads for selective adsorption of Cadmium (II) and Chromium (III) metal ions

Developing cost-effective and efficient adsorbents for heavy metals in multicomponent systems is a challenge that needs to be resolved to meet the challenges of wastewater treatment technology. Two adsorbents were synthesized, characterized, and investigated for the removal of Cd2+ and Cr3+ as model heavy metals in their single and binary solutions. The first adsorbent (ACZ) was a nanocomposite formed of O-Carboxymethyl chitosan, sodium alginate, and zeolite. While, the other (ACL) contained ZnFe layered double hydroxides instead of the zeolite phase. Adsorbents were characterized using XRD, FTIR, SEM, and swelling degree analysis. For single heavy metal adsorption isotherms, data for both adsorbents was best fitted and indicated a multilayer adsorption nature. For binary adsorption, Langmuir model with interacting parameters showed the best results compared to other models for both pollutants. For single system, Avrami model was found to be the best model representing the adsorption kinetics data, which indicates that the mechanism of adsorption follows multiple kinetic orders that may change during duration of adsorption process. Numerous interaction mechanisms can occur between the heavy metals and functional groups in the synthesized hydrogels such as NH2, COOH, and OH groups leading to efficient adsorption of metal ions.

Desolvation-Degree-Induced Structural Dynamics in a Rigid Cerium-Organic Framework Exhibiting Tandem Purification of Ethylene from Acetylene and Ethane.

Due to the industrial requirements for high production and high quality of ethylene, efficient purification of ethylene from acetylene and ethane is of prime importance but challenging. Dynamic metal-organic frameworks (MOFs) have demonstrated intriguing structural dynamics and diverse applications recently. Among them, although a few flexible ones have exhibited interesting ethylene purification capability, rigid ones were yet barely investigated for such purpose. In this regard, a cerium(III)-based MOF was solvothermally synthesized, which is rigid and assembled from rod molecular building blocks associated with coordinative N,N-dimethylformamide (DMF) molecules. After liberating different degrees of DMF ligands via heating under vacuum or acetone exchange, both partially desolvated compounds of Ce-MOF-1 and Ce-MOF-2 were concertedly isolated in a fashion of single-crystal to single-crystal transformation. Although both newly generated materials crystallize in the same space group, they exhibit dissimilar unit cell parameters and slightly distinct ultramicropore sizes and pore microenvironments, thanks to the discrepancy in the desolvation degree. Consequently, Ce-MOF-1 and Ce-MOF-2 individually demonstrate C2H2- and C2H6-selective adsorption behavior, resulting in the potential tandem separation of C2H4 from C2H2 and C2H6 mixtures. The above results were successfully supported by not only single gas adsorption isotherms but also grand canonical Monte Carlo (GCMC) calculation studies and dynamic breakthrough experiments. The present work may pave the way for rigid MOFs aiming at advancing applications via solid-state structural dynamics.

Competitive adsorption of Alizarin Red S and Bromocresol Green from aqueous solutions using brookite TiO2 nanoparticles: experimental and molecular dynamics simulation.

In this work, the effective adsorption and the subsequent photodegradation activity, of TiO2 brookite nanoparticles, for the removal of anionic dyes, namely, Alizarin Red S (ARS) and Bromocresol Green (BCG) were studied. Batch adsorption experiments were conducted to investigate the effect of both dyes' concentration, contact time, and temperature. Photodegradation experiments for the adsorbed dyes were achieved using ultraviolet light illumination (6W, λ = 365nm). The single adsorption isotherms were fitted to the Sips model. The binary adsorption isotherms were fitted using the Extended-Sips model. The results of adsorption isotherms showed that the estimated maximum adsorption uptakes in the binary system were around 140mgg-1 and 45.5mgg-1 for ARS and BCG, respectively. In terms of adsorption kinetics, the uptake toward ARS was faster than BCG molecules in which the equilibrium was obtained in 7min for ARS, while it took 180min for BCG. Moreover, the thermodynamics results showed that the adsorption process was spontaneous for both anionic dyes. All these macroscopic competitive adsorption results indicate high selectivity toward ARS molecules in the presence of BCG molecules. Additionally, the TiO2 nanoparticles were successfully regenerated using UV irradiation. Moreover, molecular dynamics computational modeling was performed to understand the molecules' optimum coordination, TiO2 geometry, adsorption selectivity, and binary solution adsorption energies. The simulation energies distribution exhibits lower adsorption energies for ARS in the range from - 628 to - 1046 [Formula: see text] for both single and binary systems. In addition to that, the water adsorption energy was found to be between - 42 and - 209 [Formula: see text].

A Microporous Potassium‐Organic Framework for Efficient C2H2/CO2 Separation

AbstractA novel potassium‐based metal organic framework (TCBPA‐K) was prepared by using a C3‐symmetric organic building block tris(4′‐carboxybiphenyl)amine (TCBPA). The compound has a rectangular like channel along the b axis and exhibits good selective adsorption performance. The single component gas adsorption isotherms indicated that the adsorption capacity of C2H2 is much higher than that of CO2 at 298 K and 1 bar. The isosteric adsorption enthalpies of TCBPA‐K for C2H2 and CO2 are 30.6 kJ/mol and 9.1 kJ/mol respectively. Ideal adsorbed solution theory calculation recorded the separation selectivity of C2H2/CO2 (50/50, v/v) as 3.5.

Effectiveness of a simple biomixture for the adsorption and elimination of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide and its metabolite, 2,4-dichlorophenol (2,4-DCP), for a biobed system

The remediation of point-source contamination of herbicides in productive fields can be addressed with biopurification systems which require biomixtures of natural materials with effectiveness for the adsorption and degradation of such compounds. A biomixture of wheat stubble and soil was tested for the adsorption and degradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and one of its main metabolites, 2,4-dichlorophenol (2,4-DCP). Single-contaminant kinetic studies were performed, being the pseudo-second order kinetic model the most suitable to describe the adsorption of both compounds. Although the adsorption of 2,4-D was faster, the adsorption of 2,4-DCP was three times higher. Single and competitive adsorption isotherms were also obtained. The later were acquired from a complete factorial experimental design varying the concentration of both solutes. Mathematical models were applied to describe the single solute isotherms, given a maximum monolayer adsorption capacity of 155.7 mg kg−1 for 2,4-D and 371.6 mg kg−1 for 2,4-DCP. Multicomponent models for bi-solute isotherms showed a clear reduction of 2,4-D adsorption in the presence of 2,4-DCP, although no adsorption displacement for the 2,4 DCP metabolite was observed. A stagnant degradation study was run and the contaminants were surveyed during 30 days. The biomixture was successful in degrading the 2,4-D, with a removal effectiveness > 96% after 15 days. The 2,4-DCP was not detected, suggesting a very fast degradation as soon as generated.

8-hydroxyquinoline grafted triazole derivatives as corrosion inhibitors for carbon steel in H2SO4 solution: Electrochemical and theoretical studies

The inhibition capacity of carbon steel (CS) in 0.5M H2SO4 by three 8-hydroxyquinoline grafted triazole derivatives (EHTC, AHTC, and MHTC) have been investigated using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PPD), and weight loss measurements (WLM) at 298 K. Generally, the results clearly show that the inhibition performance (η %) increases with an increase in the concentration of EHTC, MHTC, and AHTC, reaching a maximum value of 95.5% (EHTC), 95.1% (MHTC), and 94.1% (AHTC) at the optimal concentration (10−3 M) for PPD technical. The PPD shows that EHTC, AHTC, and MHTC behave as mixed-type inhibitors. In addition, the inhibitor obeys the single layer adsorption isotherm of Langmuir. Scanning electron microscopy (SEM) analysis of the CS has also been investigated and discussed. The theoretical calculations and MD simulations show a better correlation with the experimental results for the studied triazole derivatives.

Selective CO2 Sorption Using Compartmentalized Coordination Polymers with Discrete Voids*.

Carbon capture and storage with porous materials is one of the most promising technologies to minimize CO2 release into the atmosphere. Here, we report a family of compartmentalized coordination polymers (CCPs) capable of capturing gas molecules in a selective manner based on two novel tetrazole-based ligands. Crystal structures have been modelled theoretically under the Density Functional Theory (DFT) revealing the presence of discrete voids of 380 Å3 . Single gas adsorption isotherms of N2 , CH4 and CO2 have been measured, obtaining a loading capacity of 0.6, 1.7 and 2.2 molecules/void at 10 bar and at 298 K for the best performing material. Moreover, they present excellent selectivity and regenerability for CO2 in mixtures with CH4 and N2 in comparison with other reported materials, as evidenced by dynamic breakthrough gas experiments. These frameworks are therefore great candidates for separation of gas mixtures in the chemical engineering industry.

Energy-Saving and Sustainable Separation of Bioalcohols by Adsorption on Bone Char

The separation of ethanol, propanol, and butanol from aqueous solutions was studied using adsorption on bone char. Adsorption kinetics and thermodynamic parameters of this separation method were studied at different conditions of pH and temperature. Results showed that the maximum adsorption capacities of these bioalcohols were obtained at pH 6 and 20°C. An exothermic separation was identified, which can be mainly associated to hydrophobic interactions between bone char surface and bioalcohols. Binary adsorption studies were also performed using mixtures of these bioalcohols. An antagonistic adsorption was observed for all bioalcohols where the ethanol and propanol separation was significantly affected by butanol. A model based on an artificial neural network was proposed to correlate both single and binary adsorption isotherms of these bioalcohols with bone char. It was concluded that the bone char could be an interesting adsorbent for the sustainable separation and recovery of bioalcohols from fermentation broths, which are actually considered emerging liquid biofuels and relevant industrial chemicals.

Influence of Salinity on the Removal of Ni and Zn by Phosphate-Intercalated Nano Montmorillonite (PINM)

The salinity influence on the adsorptions of Ni and Zn onto phosphate-intercalated nano montmorillonite (PINM) were investigated. Single adsorption isotherm models fitted the single adsorption data well. The adsorption capacity of Ni was higher than that of Zn onto PINM at different salinities. The single adsorption parameters from Langmuir model (QmL and bL) were compared with the binary adsorption (QmL* and bL*). The QmL* of Zn was lower than that of Ni. The simultaneous presence of Ni and Zn decreased the adsorption capacities. The single and binary adsorptions onto PINM were affected by the salinity. The competitive Langmuir model (CLM), P-factor, Murali and Aylmore (M−A) models, and ideal adsorbed solution theory (IAST) were satisfactory in predicting the binary adsorption data; the CLM showed the best fitting results. Our results showed that the PINM can be used as an active Ni and Zn adsorbent for a permeable reactive barrier (PRB) in the remediation of saline groundwater.

Optimal artificial neural network design for simultaneous modeling of multicomponent adsorption

In this work, ultrasound-modified chitin (UM-chitin) was used to adsorb cobalt (Co2+), methylene blue (MB), and nickel (Ni2+) in single, binary and ternary systems, at different temperatures. The single adsorption isotherms showed that the affinity of the UM-chitin towards the metals was higher than that of the dye. Antagonist adsorption was found for the binary adsorption of Co2+ and MB; however, the presence of Ni2+ in the ternary system promoted the adsorption of MB and inhibited the adsorption of Co2+. Therefore, an optimal artificial neural network was developed to predict these synergistic and antagonistic interactions simultaneously. Different ANN configurations were tested using the initial concentration of each adsorbate (0–650 mg L−1) and the solution temperature (298–328 K) as input variables. The optimal ANN structure, which uses 2 hidden layers with 5 and 10 neurons, tangent sigmoid activation function (tansig) at both hidden and output layers, and Bayesian Regulation as its backpropagation algorithm demonstrated suitable ability in simultaneously predict the adsorption capacity for each adsorbate (MSE < 0.0003 and R > 0.9995).

Sulfonyl PIM‐1: A diverse separation membrane with dilation resistance

AbstractA sulfone modified variant (soPIM‐1) of the first polymer of intrinsic microporosity has been studied through molecular simulations to analyze its applicability for adsorption‐based separations of diverse nonpolar, quadrupolar, and dipolar adsorbate species. Single component gas phase adsorption isotherms of each adsorbate are provided. The adsorptive properties of soPIM‐1 are reported from the application of two methods: (a) traditional grand canonical Monte Carlo (GCMC) simulations and (b) a combination of Monte Carlo and molecular dynamics (GCMC/MD) techniques, which accounts for sorption‐induced polymer dynamics. The calculated isosteric heats of adsorption are compared to those from the parent PIM‐1 structure and reveals increased CO2 affinity with relatively no change in hydrocarbon affinity. Moreover, to quantify soPIM‐1's resistance to dilation the evolution of the microporous structure across the adsorption isotherm loading pressures has been evaluated. Relatedly, nonequilibrium MD simulations have been utilized to determine that soPIM‐1 is approximately twice as stiff as PIM‐1.

5,5-DIPHENYL-2-THIOXOIMIDAZOLIDIN-4-ONE METHODOLOGICAL MECHANISM TO CORROSION INHIBITION FOR MILD STEEL DISSOLUTION IN HCL: DFTS, MOLECULAR DYNAMICS AND EXPERIMENTAL PROCEDURES

Continuing to study the inhibition of corrosion, 5,5-diphenyl-2-thioxoimidazolidin-4-one (PTI) has been tested as a corrosion inhibitor for mild steel (MS) in an aggressive 1 M HCl solution by chemical and electrochemical techniques: weight loss, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis, UV-Visible. Inhibitory efficacy increases with increasing inhibitor concentration and decreases with increasing temperature. The studied inhibitor is more efficient (99.2%) at 298 K at an optimal concentration of 1[Formula: see text]mM. The PDP study revealed that PTI behaved as mixed type of inhibitor. In addition, the PTI inhibitor obeys the single layer adsorption isotherm of Langmuir. The quantum chemical calculations, molecular dynamic (MD) simulation studies fairly well agreed with the experimental measurements.

Synthesis, characterization and corrosion inhibition potential of newly benzimidazole derivatives: Combining theoretical and experimental study

Three new heterocyclic benzimidazole derivatives and has been synthesized and characterized via different spectroscopic methods (1H, 13C NMR) and study their inhibitory properties of three benzimidazole derivatives, namely: 2- (2- (4-chlorophenyl) -1H-benzo [d] imidazol-1-yl) -N- (p-tolyl) acetamide (CBIN-1), 2- (2- (4-chlorophenyl) -1H) benzo [d] imidazol-1-yl) -N- (3,5-dimethylphenyl) acetamide (CBIN-2) and 2- (2- (4-chlorophenyl) -1H-benzo [d] imidazol-1-yl)) -N-phenylacetamide (CBIN-3) for carbon steel (CS) in 1 M HCl solution using electrochemical impedance spectroscopy, potentiodynamic polarization and weight loss measurements at 298 K. The experimental results show that the inhibition increases with the concentration and can reach a limit value of 95.0% for the inhibitorCBIN-2 at 10−3 M. The polarization curves show that the benzimidazole derivatives (CBIN-1, CBIN-2 and CBIN-3) are of mixed type. The increase in temperature may have a decrease in the inhibition efficacy of the compounds studied. In addition, the inhibitors obey the single layer adsorption isotherm of Langmuir. It is found that the experimental parameters confirmed those obtained by theoretical studies. Surface morphology using SEM coupled and UV–visible spectroscopy of the carbon steel treated was investigated and discussed.

The GCMC simulations of adsorption of ethanol and water in zeolitic imidazolate frameworks

The adsorption mechanism of ethanol and water in five zeolitic imidazolate frameworks (ZIFs) has been investigated using grand canonical Monte Carlo (GCMC) method. The single adsorption isotherm and the selectivity of mixture adsorption of ethanol and water in ZIFs have been obtained. The results show that, at lower pressures (<10kPa), the adsorption amounts decrease in the order of ZIF-2>-10>-6≈-8≈-4. However, when the pressure is higher than 10kPa, the uptakes order is ZIF-10>-2>-6>-8>-4. And the water uptake decrease with the order of ZIF-10>-2>-4>-6>-8. However, the water uptakes for all the ZIFs is very small. The mixture adsorption of ethanol and water shows that, at a given lower pressure, the selectivity decreases as ZIF-2>-8>-10>-6>-4. However, at a given higher pressure, the selectivity is in the order of ZIF-10>-2≈-6≈8>-4. It can be concluded that ZIF-2 and -10 are suitable for the adsorption and separation of biofuel of ethanol. The total interaction energy distribution of ZIFs with ethanol/water has also been analyzed to interpret the adsorption mechanism of ethanol and water in ZIFs.

Understanding adsorption behavior of α-chymotrypsin onto cation exchanger using all-atom molecular dynamics simulations

The interest for a better understanding of ion-exchange mechanisms at the atomic level has strongly increased over the past decades. Indeed, molecular-level information about physico-chemical mechanisms could help optimizing chromatographic processes for protein purification, which are sub-optimized due to the lack of predictive models. A promising approach is based on the use of Molecular Dynamics (MD) simulations to study local phenomena inside adsorbents which can then be challenged against experimental results. In this work, macroscopic experimental data, consisting in the ion-exchange uptake of α-chymotrypsin onto SP Sepharose FF, have been compared to the adsorption behavior predicted by MD simulations. The chromatographic surface, represented as a uniform distribution of ligands with a counterion layer, in the presence of the protein was modeled using all-atom representation. The SMA formalism was used to describe single adsorption isotherms and to relate macroscopic observations with molecular simulations. Two SMA parameters based on physical principles, the characteristic charge n and the steric factor σ, have been estimated by both experiments and MD simulations. At pH 5 and NaCl concentration of 100 mM, our study shows a fairly good agreement between both results, especially for the characteristic charge. It is shown that the steric factor calculation is strongly dependent on the ligand density on the adsorbent surface, whose value must be carefully determined in order to obtain reliable predictions. In addition, four binding patches were identified as being involved in the adsorption, which have been confirmed through binding free energy calculations.

Interplay of Tri- and Bidentate Linkers to Evolve Micropore Environment in a Family of Quasi-3D and 3D Porous Coordination Polymers for Highly Selective CO2 Capture.

In the design and construction of porous materials, these with exceptional structure and composition are often highly expected, as they may offer unique nanopore space for desired applications. Here, a new family of quasi-3D and a 3D porous coordination polymers (PCPs) (termed NTU-43 to NTU-50) were constructed via an evolution strategy from a layered structure (termed NTU-42). Single gas adsorption isotherms of CO2, N2, and CH4 display the dependency of gas capacity on optimized effects of pore size, functionality, and charged framework of these quasi-3D PCPs, where NTU-45 and NTU-46, the two with NH2-BDC and OH-BDC bidentate linkers (NH2-BDC = 2-aminoterephthalic acid and OH-BDC = 2-hydroxyterephthalic acid) have demonstrated outstanding ability for selective CO2 uptake. To the best of our knowledge, this is the first time to well explore the synergistic effects toward gas adsorption on a platform of quasi-3D frameworks. More importantly, the efficient CO2 capture from CO2/CH4 and CO2/N2 mixtures has been also validated by breakthrough experiments under continuous and dynamic conditions at 298 K.

Adsorption of phenolic contaminants from water on activated carbon: An insight into single and multicomponent adsorption isotherms

AbstractThe study focuses on the single and multicomponent adsorption of phenolic compounds from solution onto an activated carbon in the concentration range of 50–500 ppm at room temperature. The observed adsorption isotherms were correlated using various predictive and nonpredictive single and multicomponent adsorption isotherm equations. A strong influence of interadsorbate repulsion was evident based on the model proposed using Nitta's adsorption isotherm model.

Understanding the adsorption mechanism of phenol and 2-nitrophenol on a biopolymer-based biochar in single and binary systems via advanced modeling analysis

In this paper, the adsorption of phenol and 2-nitrophenol on a biopolymer-based biochar in single and binary systems was investigated at 298–328 K and pH 5. Experimental results indicated that the adsorption capacities of phenol were significantly reduced from single to binary systems compared to those obtained for 2-nitrophenol. This experimental evidence suggested an antagonistic effect between both adsorbates generating an inhibitive adsorption. In terms of modeling analysis, the single and binary adsorption isotherms were well reproduced by monolayer and competitive monolayer statistical physics models, respectively. These two models showed that phenol and 2-nitrophenol molecules have been mainly docked with an inclined and horizontal positions in single and binary systems, respectively. A detailed analysis of the number of captured phenol (n1) and 2-nitrophenol (n2) molecules per site in the binary systems demonstrated that its corresponding evolution varied with a completely inverse way thus corroborating the inhibition effect between phenol and 2-nitrophenol molecules. The monolayer and competitive monolayer models were used to estimate two adsorption energies to characterize the single and binary adsorption mechanisms. The analysis of the energetic parameters suggested that the adsorption process was a physisorption. The interpretation of all monolayer and competitive monolayer model parameters provided new insights that contributed to understand the single and binary adsorption mechanisms of phenol and 2-nitrophenol molecules on tested adsorbent.

Impact of MOF defects on the binary adsorption of CO2 and water in UiO-66

Metal organic frameworks are frequently examined as potential solutions to complex gas phase separations problems. In many cases, the gas phase adsorption properties of these materials are quantified using single component gas adsorption isotherms and breakthrough experiments. In adsorption separations, however, it is common that the adsorbent participates in a multicomponent adsorption event. In the literature there is a general absence of multicomponent adsorption data with most data predicted via the Ideal Adsorbed Solution Theory or molecular simulations. Therefore, in this work, binary adsorption data of CO2 and water on UiO-66 were measured experimentally using a volumetric method at three different water loadings. Molecular simulations of isotherms were compared to the experimental measurements and the impact of two different MOF defect sites on the multicomponent CO2/H2O adsorption behavior was determined. The experimental data show a slight enhancement of CO2 loading when CO2 is co-adsorbed with water, which is a result that was confirmed via molecular simulations. Also, the simulation results show that defect sites can have a greater influence on low-pressure CO2 adsorption in MOFs than the co-adsorption of water. Furthermore, the simulations provide a molecular-level understanding of the role of these defects on the single and binary adsorption behavior.