Binary Adsorption Research Articles

The time response of plasmonic sensors due to binary adsorption: analytical versus numerical modeling

In order to allow for multiscale modeling of complex systems, we focus on various approaches to modeling binary adsorption. We consider multiple methods of modeling the temporal response of general plasmonic sensors. We start from the analytical approach. The kinetics of adsorption and desorption is modeled both as a first order reaction and as a second-order reaction. The criteria for their validity and the choice between them in the case of two-component adsorption are established. Due to the nonlinearities of the second-order reactions and the lack of their analytical solutions, computer-aided modeling is considered next, also in multiple ways: the employment of numerical solvers, fitting of experimental results, the stochastic simulation algorithms and the employment of artificial neural networks (ANN). The examples we present illustrate the advantages and disadvantages of the particular approaches. The goal is to aid the concurrent multiscale modeling of adsorption-based devices. Machine learning in ANN performed here is used to estimate the equilibrium values of adsorbed quantities. The obtained results show that to train an ANN for the estimation of the equilibrium adsorption quantities the Levenberg–Marquardt and the Bayesian regularization algorithms are less efficient than the quasi-Newton BFGS (Broyden–Fletcher–Goldfarb–Shanno) algorithm.

Elucidation of Selectivity Reversals for Binary Mixture Adsorption in Microporous Adsorbents.

The adsorption selectivity, Sads, is a key metric that quantifies the efficacy of any adsorbent in mixture separations. It is common practice to use ideal adsorbed solution theory (IAST) for estimating the value of Sads, using unary isotherm data inputs. In a number of experimental investigations, the phenomena of selectivity reversals and adsorption azeotropy (Sads = 1) have been reported in the published literature; such reversals may result from changes in mixture compositions, pressures, or pore loadings. In many cases, IAST is unable to anticipate such selectivity reversals. In this article, configurational-bias Monte Carlo simulations are used to gain insights into the phenomena of selectivity reversals. Two fundamentally different scenarios of selectivity reversals have been identified. In the first scenario, selectivity reversals are caused by inhomogeneous distribution of adsorbates due to preferential location and siting of a guest species in the pore space. For example, CO2 locates preferentially in the side pockets of mordenite and in window regions of DDR, CHA, and LTA zeolites. CO2 also congregates around the extra-framework cations of NaX zeolite. IAST fails to anticipate such selectivity reversals because its development relies on the assumption that the competition between guest species is uniform within the pore space. In the second scenario, selectivity reversals are caused by entropy effects that manifest near pore saturation conditions; the component that is preferentially adsorbed is the one that has the higher packing efficiency. For a homologous series of compounds, the component with the smaller chain length is favored at high pore occupancies. For adsorption of mixtures of alkane isomers within the intersecting channel network of MFI zeolite, the linear isomer is favored on the basis of entropic considerations.

Electrically heated catalyst device

The performance of the MIL-101(Cr) loaded with cuprous oxide (Cu2O) nanoparticles was evaluated in both equilibrium and kinetic conditions for adsorption of propane and propylene via volumetric method. The single-component adsorption isotherms were measured at temperatures of 303, 323, 343 and 363 K and pressures up to 400 kPa. To correlate the experimental isotherm data points, temperature-dependent Sips model was applied, which exhibited high accuracy of prediction. The synthesized samples were characterized by XRD, BET, FE-SEM, EDS mapping and TEM techniques. The binary mixture adsorption behavior and selectivity of propane/propylene were calculated by using the ideal adsorbed solution theory (IAST). Obtained results showed that by increasing the loading of Cu2O nanoparticles up to 15 wt%, the propylene selectivity of MIL-101(Cr) was enhanced from 1.5 to 12.2 at 100 kPa and 303 K. Moreover, the optimum performance in terms of both adsorption capacity and selectivity was achieved using 12%[email protected](Cr) sample. Fast diffusion of the adsorbates, obtained by accurate fitting of the isothermal micropore model to the uptake curves data, along with reusability suggest the 12%[email protected](Cr) as a promising adsorbent for effective separation of propane/propylene mixture.

Crosslinking acrylamide with EDTA-intercalated layered double hydroxide for enhanced recovery of Cr(VI) and Congo red: Adsorptive and mechanistic study

We prepared ethylenediaminetetraacetic acid (EDTA)-intercalated MgAl-layered double hydroxide (LDH-EDTA), then grafted acrylamide (AM) to the LDH-EDTA by a cross-linking method to yield a LDH-EDTA-AM composite; we then evaluated its adsorptive ability for Congo red (CR) and hexavalent chromium (Cr(VI)) in single and binary adsorption systems. The adsorption process on LDH-EDTA-AM for CR and Cr(VI) achieved equilibrium quickly, and the removal efficiencies were minimally affected by initial pH. The maximum uptake quantities of CR and Cr(VI) on LDH-EDTA-AM were 632.9 and 48.47 mg/g, respectively. In mixed systems, chromate removal was stimulated by the presence of CR, while the adsorption efficiency of CR was almost not influenced by coexisting Cr (VI). The mechanisms involved electrostatic attraction, surface complexation, and anion exchange for the adsorption of both hazardous pollutants. In the Cr(VI) adsorption process, reduction also took place. The removal efficiencies in real contaminated water were all higher than those in the laboratory solutions.

Removal of Cd(II) and Cu(II) from Aqueous Solution by Na+-Modified Pisha Sandstone

Heavy metals have caused serious environmental issues, which are enriched during open-cast coal mining. It is urgent to develop sustainable remediation materials to protect and restore the contaminated soil and aquifers in mining areas. The feasibility of applying Pisha sandstone (PS) and Na+-modified Pisha sandstone (Na-PS) for adsorption of heavy metals was evaluated. Na-PS exhibited maximum Cd(II) and Cu(II) removal rates of 65.9% and 99.8%, respectively, exceeding the corresponding values for PS (8.2% and 1.3%, respectively) in 1 × 10−3 M solution. Efficient heavy metals adsorption occurred in the pH range 5.0–6.0. The adsorption of Cu(II) and Cd(II) on PS and Na-PS was characterized by kinetic models and adsorption isotherms and was well represented by pseudo-second-order kinetics (R2 > 0.99) and the Langmuir and Freundlich isotherm models. The values of the thermodynamic parameters indicated that the interactions were spontaneous endothermic reactions. Binary solutions adsorption isotherms indicated that the linearity of the adsorption amount and initial concentration of Cu(II) and Cd(II) was better in certain ranges and the adsorbents were selective towards Cu(II) rather than Cd(II). Therefore, PSs can be used as excellent adsorbents for Cu(II) and Cd(II) remediation from contaminated surface water.

Single and Binary Competitive Adsorption of Cobalt and Nickel onto Novel Magnetic Composites Derived from Green Macroalgae

Easily separated novel magnetic composite, derived from a kind of green macroalgae—Enteromorpha prolifera, was employed for effective adsorption of radioactive cobalt (60Co) and nickel (63Ni). The ...

Separation of ethane-ethylene and propane-propylene by Ag(I) doped and sulfurized microporous carbon

Abstract Separation of light olefins from their respective paraffins by adsorption is an attractive strategy due to the sustainable and inexpensive nature of adsorption process. It is well understood that the presence of Ag(I) in the adsorbent favors the adsorption of ethylene and propylene (olefins) over ethane and propane (paraffins) owing to the π - π complexation between Ag(I) and π bond present in olefins. In this research, Ag(I) doped microporous carbons were synthesized from furfuryl alcohol as carbon source. It is also shown that prior sulfurization of the carbon greatly favored Ag(I) content owing to the affinity of sulfur to Ag(I). All the carbons were successfully characterized with pore textural properties, SEM-EDX imaging and x-ray photoelectron spectroscopy (XPS). Only the carbon with highest Ag(I) content (2.5 at.%) and BET specific area (1193 m2/g) favored the adsorption of ethylene and propylene over ethane and propane, respectively. IAST-based selectivity values were also employed to calculate binary adsorption isotherms for ethane-ethylene and propane-propylene mixtures. The IAST-based selectivity values of ethylene/ethane and propylene/propane were in the range of 4.5 to 2.5 and 5 to 2.4, respectively. Finally, column breakthrough and pulse chromatographic peaks were simulated to confirm the separation of paraffin-olefin pairs on thus carbon. To the best of our knowledge, it is the first report of the separation of light paraffin and olefins in a carbon-based adsorbent and by harnessing the π - π complexation.

Numerical Simulation of the Effect of Injected CO2 Temperature and Pressure on CO2-Enhanced Coalbed Methane

The injection of CO2 to displace CH4 in coal seams is an effective method to exploit coalbed methane (CBM), for which the CO2 injection temperature and pressure are important influential factors. We performed simulations, using COMSOL Multiphysics to determine the effect of CO2 injection temperature and pressure on CO2-enhanced coalbed methane (CO2-ECBM) recovery, according to adsorption/desorption, seepage, and diffusion of binary gas (CO2 and CH4) in the coal seam, and deriver a thermal–hydraulic–mechanical coupling equation of CO2-ECBM. The simulation results show that, as CO2 injection pressure in CO2-ECBM increases, the molar concentration and displacement time of CH4 in the coal seam significantly decrease. With increasing injection temperature, the binary gas adsorption capacity in the coal seam decreases, and CO2 reserves and CH4 production decrease. High temperatures are therefore not conducive for CH4 production.

Separation of propane/propylene mixture using MIL-101(Cr) loaded with cuprous oxide nanoparticles: Adsorption equilibria and kinetics study

The performance of the MIL-101(Cr) loaded with cuprous oxide (Cu2O) nanoparticles was evaluated in both equilibrium and kinetic conditions for adsorption of propane and propylene via volumetric method. The single-component adsorption isotherms were measured at temperatures of 303, 323, 343 and 363 K and pressures up to 400 kPa. To correlate the experimental isotherm data points, temperature-dependent Sips model was applied, which exhibited high accuracy of prediction. The synthesized samples were characterized by XRD, BET, FE-SEM, EDS mapping and TEM techniques. The binary mixture adsorption behavior and selectivity of propane/propylene were calculated by using the ideal adsorbed solution theory (IAST). Obtained results showed that by increasing the loading of Cu2O nanoparticles up to 15 wt%, the propylene selectivity of MIL-101(Cr) was enhanced from 1.5 to 12.2 at 100 kPa and 303 K. Moreover, the optimum performance in terms of both adsorption capacity and selectivity was achieved using 12%Cu@MIL-101(Cr) sample. Fast diffusion of the adsorbates, obtained by accurate fitting of the isothermal micropore model to the uptake curves data, along with reusability suggest the 12%Cu@MIL-101(Cr) as a promising adsorbent for effective separation of propane/propylene mixture.

Cellulose Nanofibril/Carbon Nanomaterial Hybrid Aerogels for Adsorption Removal of Cationic and Anionic Organic Dyes.

Advances in nanoscale science and engineering are providing new opportunities to develop promising adsorbents for environmental remediation. Here, hybrid aerogels are assembled from cellulose nanofibrils (CNFs) and carbon nanomaterials to remove cationic dye methylene blue (MB) and anionic dye Congo red (CR) in single and binary systems. Two classes of carbon nanomaterials, carbon nanotubes (CNTs) and graphene nanoplates (GnPs), are incorporated into CNFs with various amounts, respectively. The adsorption, mechanics and structure properties of the hybrid aerogels are investigated and compared among different combinations. The results demonstrate CNF–GnP 3:1 hybrid exhibits the best performance among all composites. Regarding a single dye system, both dye adsorptions follow a pseudo-second-order adsorption kinetic and monolayer Langmuir adsorption isotherm. The maximal adsorption capacities of CNF–GnP aerogels for MB and CR are 1178.5 mg g−1 and 585.3 mg g−1, respectively. CNF–GnP hybrid show a superior binary dye adsorption capacity than pristine CNF or GnP. Furthermore, nearly 80% of MB or CR can be desorbed from CNF–GNP using ethanol as the desorption agent, indicating the reusability of this hybrid material. Hence, the CNF–GnP aerogels show great promise as adsorption materials for wastewater treatment.

Hybrid silicate-hydrochar composite for highly efficient removal of heavy metal and antibiotics: Coadsorption and mechanism

A novel cost-effective hydrochar composite (MgSi-HC) prepared by a simple one-step process using waste sawdust, inexpensive silicate and magnesium salts as raw materials was used to remove Cu(II), Zn(II), and tetracycline (TC) from aqueous solution. The novel hydrochar material was characterized by SEM, TEM, XRD, BET specific surface area, ATR-FTIR spectra, and X-ray photoelectron spectroscopy. The values of surface area (107.7 m2/g) and pore volume (0.489 cc/g) of MgSi-HC indicated that it had a large specific surface area and well-developed pore structure. Adsorption isotherm showed that the maximum adsorption capacity of MgSi-HC for Cu(II), Zn(II), and TC was 214.7 mg/g, 227.3 mg/g, and 361.7 mg/g, respectively. In addition, the effects of heavy metals and tetracycline on each other in binary adsorption systems were different. Meanwhile, the study of mechanism indicated that various interactions might be involved in the adsorption process, and the adsorption mechanisms of heavy metal and TC were different. The potential of MgSi-HC for practical environmental remediation was evaluated, the result demonstrated that MgSi-HC still had high performance after 5 adsorption-desorption cycles, and it had stable adsorption ability in different water samples (150.2–156.2 mg/g for Cu, 159.6–167.4 mg/g for Zn, and 183.9–189.8 mg/g for TC), implying that the novel hydrochar could be a promising adsorbent for removal of heavy metal and antibiotics from real wastewater. This work provided a reference on the coadsorption of heavy metal and antibiotics, and indicated the potential application of MgSi-HC in complex pollutant adsorption.

Single and binary component adsorption of endocrine disrupting chemicals from aqueous solutions using calcium alginate/apricot stone-activated carbon composite beads

Single and binary component adsorption of endocrine disrupting chemicals from aqueous solutions using calcium alginate/apricot stone-activated carbon composite beads

Determination of the adsorption isotherms and transport diffusivities of gases in mixtures inside zeolitic crystals using Infra-Red Micro-imaging

Different regions of Infra-Red (IR) light absorption by guest molecules inside a zeolitic crystal are measured and quantified to determine binary adsorption isotherms and transport diffusivities. This has been achieved using a vacuum capable setup which includes an Infra-Red Microscope (IRM) and Fourier Transform Infra-Red (FTIR) Spectrometer. By utilizing IR light and FTIR spectroscopy, this method can be used to describe the behavior of low concentrations of relatively fast molecules inside zeolitic crystals as an alternative to chromatographic pulse methods. To demonstrate the capabilities of this method, binary adsorption isotherms and transport diffusivities of CO2 in mixtures composed of CO2 and N2 inside silicalite have been determined. From the fundamental measurements determined using this method, complex gas separation processes such as swing adsorption and multi stage membrane systems can be designed for novel zeolite materials. This method can also be used to develop models for complex adsorption and diffusion systems, and validate sophisticated molecular simulation models.•IR microimaging with static gas dosing system for measuring transient uptake, diffusion and chemical reactions of gases and their mixtures in individual crystals or particles of nanoporous materials•Using giant crystals the setup allows to study adsorption and transport of single components and mixtures in nanoporous materials also for fast diffusing guest molecules

Grand Canonical Monte Carlo Modeling of Anesthetic Xe Separation from Exhale Gas Mixtures Using Metal Organic Frameworks

Xe has been shown to be a promising candidate for anesthetic applications. However, its high price prevents its usage in clinical industry. An alternative approach is to recover Xe from anesthetic exhale gas mixture and recycle it to the inhale gas stream. Although, many membranes and/or adsorbents have been proposed for recovering anesthetic Xe, using metal organic frameworks (MOFs) for adsorption based separation of anesthetic Xe exhale gas mixtures has been newly studied. MOFs have tunable pore sizes, large surface areas, and high porosities which make them potential candidates for gas separation applications. Currently, very little is known about anesthetic Xe recovery performances of MOFs. We theoretically investigate adsorption based separation of single component and binary mixtures of CO2, Xe, and N2 in three MOFs, namely CECYOY, SUDBOI, and ZUQPOQ. Single component and binary adsorption isotherms and adsorption selectivities are calculated using Grand Canonical Monte Carlo simulations for each MOF in order to characterize their performances as adsorbents. Results suggest that while MOFs prefer adsorption of CO2 for CO2/Xe mixture, Xe adsorption is favorable in the case of Xe/N2 mixture. While SUDBOI shows significantly large CO2 adsorption selectivity for CO2/Xe mixture, ZUQPOQ has the largest adsorption selectivity for Xe/N2 mixture.

Screening PIM-1 performance as a membrane for binary mixture separation of gaseous organic compounds

Developing microporous polymeric membranes for the separation of a diverse set of organic species can have a profound impact on many industrial fields. This study reports data for unary/binary adsorption and membrane separation performance for acetaldehyde, acetone, methane, methanethiol, propane, and propene studied with PIM-1. The data is reported at 300 K for the pure gases, 15 unique binary pairs, and at 3 molar fractions (45 pairs in all), which required a total of 2633 independent simulations. Based on the potential complexities associated with binary adsorption processes, we describe a statistical approach that can be broadly applicable in identifying system equilibration and overall contribute to predictions with increased fidelity, enabling high-throughput screening. We provide correlations from available experimental porous polymer data that can predict diffusivity as a function of the membrane fractional free volume for propane and propene. Using these results, several PIM-1 binary mixture membrane performance metrics, such as permselectivity, are reported for paraffin/olefin separation. These relations are essential for experimental and computational studies because they allow researchers to assess gas diffusivity/permeability results while avoiding expensive methods needed to otherwise quantify gas transport.

A cost-effective β-cyclodextrin polymer for selective adsorption and separation of acetophenone and 1-phenylethanol via specific noncovalent molecular interactions

To separate acetophenone (AP) and 1-phenylethanol (PE), a kind of cost-effective β-cyclodextrin based polymeric sorbent (CE-CDP) was constructed by crosslinking β-cyclodextrin with toluene-2,4-diisocyanate trimer. According to the characteristic results, the structure of the CE-CDP consisting of β-cyclodextrin cavity, aromatic urethane bond and unique isocyanurate ring was proved substantially. It was shown that crosslinking process would enhance the thermal stability, and the incorporation of the unique crosslinking units into CE-CDP's network potentially improved the selective adsorption performance compared to analogous polymer with non-isocyanurate ring structure. The static adsorption performance of CE-CDP in single solute system was investigated. The adsorption capacity of AP was much higher than that of PE, indicating that CE-CDP exhibits much stronger affinity toward AP over PE. Based on the results, we found that the spontaneous adsorption processes of AP and PE onto CE-CDP could be well described by pseudo-second order kinetics, Langmuir and Freundlich isotherm models. And the preferential AP adsorption over PE (selectivity≈6) was further verified through binary competitive adsorption. In addition, the density functional theory calculations showed that the coexistence of β-cyclodextrin cavity, aromatic urethane bond and isocyanurate ring endows CE-CDP with high AP adsorption capacity and selectivity. The theoretical results also indicated that the noncovalent interactions involving the intermolecular hydrogen bonding, π-π interactions and electrostatic interaction are favorable for binding AP rather than PE. In conclusion, CE-CDP was proved to be a good adsorbent for selective separation of AP and PE with mass producibility, low cost, high reusability and wide application prospect.

Use of bone char prepared from an invasive species, pleco fish (Pterygoplichthys spp.), to remove fluoride and Cadmium(II) in water

In this study, bone char (BC) from pleco fish (Pterygoplichthys spp.) was synthesized, and their textural and physicochemical properties, as well as its adsorption capacity towards fluoride and Cd(II) from single and binary aqueous solutions, were determined. The results showed that the properties of the BCs were independent of the type of bone used and the surface areas were close to 110 m2 g−1. The effect of solution pH revealed that the adsorption capacity of BC towards fluoride from water raised by decreasing the solution pH. This trend was attributed to the electrostatic interaction between the positively charged surface and the fluoride in aqueous solution. On the contrary, the capacity of BC for adsorbing Cd(II) was enhanced by increasing the solution pH, indicating that electrostatic interactions were also essential but with a contrary effect in comparison with fluoride adsorption due to the negatively charged surface at pH above the point zero charge (pHPZC = 8.16). The experimental data for binary adsorption of fluoride and Cd(II) were interpreted satisfactorily using the modified Freundlich multicomponent isotherm (EFMI), and the experimental data revealed that Cd(II) have an antagonistic effect on the adsorption of fluoride, whereas the presence of fluoride does not affect the capacity of BC for adsorbing Cd(II). Thermogravimetric, XRD diffraction and IR spectroscopy analysis corroborated that the adsorption of fluoride in BC is due to electrostatic attractions, ion exchange or chemisorption and physisorption. Besides, the removal of Cd(II) occurs by physical adsorption and ion exchange. It was concluded that BC is an alternative material for the removal of fluoride and Cd(II) from aqueous solutions, and it is a possible application for using the bones of this invasive fish species.

Optimizing experimental binary adsorption of aniline–nitrobenzene onto granular activated carbon packed bed by Taguchi’s methodology

Herein a new statistical approach based on Taguchi’s methodology was developed for optimizing continuous simultaneous adsorption of aniline (AN) and nitrobenzene (NB) from their binary aqueous solution in a column packed with granular activated carbon (GAC). Effects of column design parameters such as feed flow rate (Q), bed height (Z) and bed diameter (D) were studied for the breakthrough curve performance using Taguchi’s L9 orthogonal array design. The parameters were optimized at three levels with the higher-is-better type response characteristics. Further, the Thomas model was used to predict column breakthrough curve and breakthrough time. Higher sorption affinity of NB over AN towards GAC surface implied favorable attachment of NB molecules. Quicker breakthrough attainment was observed at higher Q, lower Z and lower D owing to faster saturation of sorption sites. Maximum individual equilibrium adsorption uptake for AN and NB was found to be 0.29 mg/g and 3.91 mg/g, respectively, at Q = 0.02 L/min, Z = 60 cm and D = 2.54 cm. The average total equilibrium adsorption uptake (qtot) from the experimental runs was found to be 4.2 mg/g which is closer to the predicted qtot value of 4.17 mg/g.

Single and competitive adsorption studies of two cationic dyes from aqueous mediums onto cellulose-based modified citrus peels/calcium alginate composite

Acetic acid-modified powdered and encapsulated cellulose-based modified citrus peels CPAA and CPAA-A were easily prepared and characterized using FTIR, DRX, BET, SEM, pHPZC and Boehm analysis, to investigate the single and binary adsorption of MB and CV dyes.Many parameters that affect adsorption phenomena were investigated: pH (3–11) of initial dyes solution, contact time, and initial dyes concentration (25–300 mg·L−1).Kinetics modeling shows that the adsorption of MB and CV onto adsorbents was well described by pseudo-first-order. CV and MB adsorption capacities on CPAA-A were respectively 881.36 and 923.07 mg·g−1 found by Langmuir model showing homogeneous and monolayer adsorption of MB and CV. The removal of dyes in the binary system shows that adsorption was slightly or nether affected by the simultaneous presence of the dyes in solution. CPAA-A and CPAA show very high adsorption capacities proving to be very useful in the field of water treatment in single or binary systems.

Binary adsorption of Cu(II) and Ni(II) on Lai'yang bentonite: Kinetics, equilibrium, competition quantitative and mechanisms investigation

AbstractIn this study, the competitive adsorption of Cu(II) and Ni(II) adsorption onto bentonite were investigated. The effects of initial adsorbate concentration, pH, contact time, temperature on adsorption and the kinetics, thermodynamic, quantification of adsorption competition and competitive mechanisms have been studied. The results indicated that Cu(II) has a higher affinity than Ni(II) for adsorption on bentonite. But the inhibition effect was not noticeable under alkaline conditions. The Langmuir and pseudo‐second‐order kinetics models can be applied to simulate the isothermal adsorption and adsorption dynamic, respectively. Under a single system/binary system, the maximum adsorption capacity of bentonite for Cu(II) and Ni(II) is 12.76/10.57 and 11.12/9.11 mg/g, respectively. The equilibrium adsorption capacity reduction rate is suitable for quantitative characterization of adsorption competition under any concentration conditions; adsorption competition coefficient is more suitable for low concentration adsorption; although the distribution coefficient is not suitable for quantitative adsorption competition at high concentrations, it can be used to characterize the variation of adsorption competitiveness of Cu(II) at different concentrations. The higher electronegativity, lower first hydrolysis constant and Misono softness, and a better “guest‐host” consistency between Cu(II)O6 and the vacancies in the montmorillonite octahedral sheet make the higher affinity of Cu(II) to bentonite and result in the possible ion exchange between Cu(II) in solution and adsorbed Ni(II). In addition, at high concentrations, Cu(II) and Ni(II) precipitates formed on the surface of montmorillonite may cause remained Cu(II) ions in the solution unable to enter the internal space of the montmorillonite octahedron.