Adsorbate-adsorbate Interactions Research Articles

Removal of Mo(VI), Pb(II), and Cu(II) from wastewater using electrospun cellulose acetate/chitosan biopolymer fibers

Environmentally friendly polymers such as cellulose acetate (CA) and chitosan (CS) were used to obtain electrospun fibers for Cu2+, Pb2+, and Mo6+ capture. The solvents dichloromethane (DCM) and dimethylformamide (DMF) allowed the development of a surface area of 148 m2 g−1 for CA fibers and 113 m2 g−1 for cellulose acetate/chitosan (CA/CS) fibers. The fibers were characterized by IR-DRIFT, SEM, TEM, CO2 sorption isotherms at 273 K, Hg porosimetry, TGA, stress-strain tests, and XPS. The CA/CS fibers had a higher adsorption capacity than CA fibers without affecting their physicochemical properties. The capture capacity reached 102 mg g−1 for Cu2+, 49.3 mg g−1 for Pb2+, and 13.1 mg g−1 for Mo6+. Furthermore, optimal pH, adsorption times qt, and C0 were studied for the evaluation of kinetic models and adsorption isotherms. Finally, a proposal for adsorbate-adsorbent interactions is presented as a possible capture mechanism where, in the case of Mo6+, a computational study is presented. The results demonstrate the potential to evaluate the fibers in tailings wastewater from copper mining.

Synthesis and characterization of polyethyleneimine grafted lignocellulosic fibers for improved removal of nitazoxanide and ampicillin from water

The COVID-19 pandemic has led to increased usage of various drugs, impacting both human and environmental health. Detecting these drugs and their metabolites in water sources has become common, presenting challenges for water treatment. Adsorption processes, particularly using vegetal biomass as an adsorbent, offer an environmentally friendly solution. In this study, we chemically grafted polyethyleneimine (PEI) onto Luffa cylindrica (LF) to enhance its adsorption capacity, enabling effective removal of nitazoxanide (NTZ) and ampicillin (AMP), two drugs used in COVID-19 treatment, from water. Characterization analyses confirmed that PEI grafting induced changes in the chemical, thermal, and morphological properties of LF. The resulting grafted material (LF-g-PEI) exhibited improved adsorption capacity compared to unmodified LF for both drugs. Specifically, the adsorption capacity of LF-g-PEI increased by 59 % for NTZ and 43 % for AMP. Removal rates of these drugs from water using LF-g-PEI reached 59 % for NTZ and 23 % for AMP within 60 min. The adsorption of NTZ and AMP on LF-g-PEI demonstrated higher spontaneity and a physisorption nature, primarily due to enhanced adsorbent-adsorbate interactions facilitated by PEI. LF-g-PEI showed excellent potential for reuse, enhancing its practical applicability for adsorption processes. Overall, this study illustrates that grafting PEI onto LF is a dependable strategy to boost the adsorption capacity of this vegetal biomass. The resulting adsorbent material holds promise for efficiently removing drugs commonly used in COVID-19 treatment from water sources.

Understanding and Predicting the Spatially Resolved Adsorption Properties of Nanoporous Materials.

Using knowledge from statistical thermodynamics and crystallography, we develop an image-image translation model, called SorbIIT, that uses three-dimensional grids of adsorbate-adsorbent interaction energies as input to predict the spatially resolved loading surface of nanoporous materials over a broad range of temperatures and pressures. SorbIIT consists of a closed-form differential model for loading-surface prediction and a U-Net to generate spatial differential distributions from the energy grids. SorbIIT is trained using the energy grids and adsorbate distributions (obtained from high-throughput simulations) of 50 synthesized and 70 hypothetical zeolites and applied for predicting the adsorption of carbon dioxide, hydrogen sulfide, n-butane, 2-methylpropane, krypton, and xenon in other zeolites from 256 to 400 K. Employing a quadratic isotherm model for the local differentiation, SorbIIT yields mean R2 values of 0.998 for total adsorption and 0.6904 for local adsorption with a resolution of 0.2 Å, and a value of 0.721 for the structural similarity of the local loading distribution.

Coverage- and Facet-Dependent Multiscale Modeling of O* and H* Adsorption on Pt Catalytic Nanoparticles.

Within computational heterogeneous catalysis, two critical factors exist-coverage and multifaceted effects-which are challenging to incorporate and contribute to differences between the results obtained from computational and experimental studies. Such disparities exist when significant adsorbate-adsorbate interactions are present, particularly when coupled with computationally limited facet sampling. Here, we designed a study to demonstrate the significance of coverage and facet effects on the predicted coverages for O* and H* on Pt nanoparticles. This is accomplished by employing multiscale modeling techniques using a three-pronged approach consisting of density functional theory (DFT), ab initio phase diagrams, and mean-field microkinetic models. Overall, adsorbate-adsorbate interactions are repulsive and far stronger for O*/Pt than for H*/Pt. For O* on Pt(111), repulsive interactions are both two- and three-body, but on Pt(100) and Pt(110), they are predominantly three-body. Through benchmarks to existing experimental literature, we demonstrate that experimentally observed coverages and desorption temperatures can be accurately estimated by computational models when the adsorbate-adsorbate interactions are included. Finally, by combining microkinetic models at the equilibrium limit with kubic harmonic interpolation, we model the impacts of the treatment of adsorbate-adsorbate interactions on the predicted O* and H* coverages over multifaceted Pt nanoparticles. Omitting adsorbate-adsorbate interactions over Pt nanoparticles leads to an overestimation of equilibrium coverages of the adsorbates (maximum of 0.29 and 0.11 ML for O* and H*, respectively) across a wide range of temperatures and pressures relevant to heterogeneous catalysis. Altogether, our work demonstrates that the inclusion of coverage and facet effects increases the accuracy of computational models for heterogeneous catalysts.

Molecular-level insight into the chlorofluorocarbons adsorption by defective covalent organic polymers.

Halocarbons have important industrial applications, howevertheycontributeto global warming and the fact that they can cause ozone depletion. Hence, the techniques that can capture and recover the used halocarbons with energy efficiency methods have recently received greater attention. In this contribution, we report the capture of dichlorodifluoromethane (R12), which has high global warming and ozone depletion potential, using covalent organic polymers (COPs). The defect-engineered COPs were synthesized and demonstrated outstanding sorption capacities, ~226 wt% of R12 combined with linear-shaped adsorption isotherms. We further identified the plausible microscopic adsorption mechanism of the investigated COPs via grand canonical Monte Carlo simulations applied to non-defective and a collection of atomistic models of the defective COPs. The modeling work suggests that significant R12 adsorption is attributed to a gradual increment of porosities due to isolated/interconnected micro-/meso-pore channels and the change of the long-range ordering of both COPs. The successive hierarchical-pore-filling mechanism promotes R12 molecular adsorption via moderate van der Waals adsorbate-adsorbent interactions in the micropores of both COPs at low pressure followed by adsorbate-adsorbate interactions in the extra-voids created at moderate to high pressure ranges. This continuous pore-filling mechanism makes defective COPs as promising sorbents for halocarbon adsorption.

Effect of Co-adsorbed Guest Adsorbates on the Separation of Ethylene/Ethane Mixtures on Metal-Organic Frameworks with Open Metal Sites.

Direct determination of the equilibrium adsorption and spectroscopic observation of adsorbent-adsorbate interaction is crucial to evaluate the olefin/paraffin separation performance of porous adsorbents. However, the experimental characterization of competitive adsorption of various adsorbates at atomic-molecular level in the purification of multicomponent gas mixtures is challenging but rarely conducted. Herein, solid-state NMR spectroscopy is employed to examine the effect of co-adsorbed guest adsorbates on the separation of ethylene/ethane mixtures on Mg-MOF-74, Zn-MOF-74 and UTSA-74. 1H MAS NMR spectra facilitates the determination of equilibrium uptake and adsorption selectivity of ethylene/ethane in ternary mixture systems. The co-adsorption of H2O and CO2 significantly leads to the degradation of the ethylene uptake and ethylene/ethane selectivity. The detailed host-guest and guest-guest interactions are unraveled by 2D 1H-1H spin diffusion homo-nuclear correlation and static 25Mg NMR experiments. The experimental results verify H2O coordinated on the open metal sites can supply a new adsorption site for ethylene and ethane. The effects of guest adsorbates on the adsorption capacity and adsorption selectivity of the ethylene/ethane mixtures are in the following order: H2O > CO2 > O2. This work provides a direct approach for exploring the equilibrium adsorption and detailed separation mechanism of multicomponent gas mixtures using MOFs adsorbents.

Repulsive Lateral Interaction of Water Molecules at the Initial Stages of Adsorption in Microporous AlPO4-11 According to 27Al NMR and DFT.

Lateral (adsorbate-adsorbate) interactions between adsorbed molecules affect various physical and chemical properties of microporous adsorbents and catalysts, influencing their functional properties. In this work, we studied the hydration of microporous AlPO4-11 aluminophosphate, which has an unusually ordered structure upon adsorption of water vapor, and according to 27Al NMR data, only tetrahedrally or octahedrally coordinated Al sites are present in the AlPO4-11. These 27Al NMR data are consistent with the results of density functional theory (DFT) calculations of hydrated AlPO4-11, which revealed the presence of a strong repulsive lateral interaction at the initial stage of adsorption, suppressing the adsorption of water on neighboring (separated by one -O-P-O- bridge) Al crystallographic sites. As a result, of all the different aluminum sites, only half of the Al1 sites adsorb two water molecules and acquire octahedral coordination.

Enhancing brilliant green dye removal via bio composite chitosan and food-grade algae capsulated ruthenium metal-organic framework: Optimization of adsorption parameters by box-behnken design

A natural material made of chitosan (CS) and algae (food-grade algae, FGA) was cross-linked and loaded onto a ruthenium metal organic framework to create a bio-adsorbent (Ru-MOF@CS/FGA composite sponge) with the aim of adsorbing and eliminating Brilliant green (BG) from aqueous solutions. A range of methods were employed to analyze the Ru-MOF@CS/FGA composite sponge, such as X-ray photoelectron spectroscopy (XPS) for elemental analysis, Fourier transform infrared spectroscopy (FTIR) to ascertain the function groups, and scanning electron microscopy (SEM) to establish the surface morphology, and powder X-ray diffraction (PXRD) to study of single and multi-phase polycrystalline materials. Brunauer-Emmett-Teller surface area (BET) confirmed the adsorbent's high surface area and pore volume (826.85 m2/g and 1.28 cm3/g, respectively) and decreased to 475.62 m2/g and 0.74 cm3/g after adsorption. Determine the several factors that affect the adsorption process, such as pH, the adsorbent's dose, the initial BG concentration, and the effect of salinity. The adsorption process was fitted to pseudo-second-order kinetics and Langmuir isotherms. Dubinin-Radushkevich analysis revealed that the adsorption energy was 23.8 kJ/mol, indicating chemisorption as the mode of adsorption. It was discovered through examining the impact of temperature and computing positive-charged enthalpy and entropy that the adsorption process was endothermic, meaning that it increased in response to temperature. It is possible to reuse the Ru-MOF@CS/FGA composite sponge six times with acceptable efficiency, no change in its chemical composition, and comparable FT-IR, XPS, and XRD data before and after each reuse. Examine the mechanisms of adsorbent-adsorbate interaction, which may involve H-bonding, n-π stacking, electrostatic forces, and pore filling. The adsorption results were optimized with the Box Behnken-design (BBD).

Piper chaba Stem Extract Facilitated the Synthesis of Iron Oxide Nanoparticles as an Adsorbent to Remove Congo Red Dye.

In this study, a straightforward, eco-friendly, and facile method for synthesizing iron oxide nanoparticles (IONPs) utilizing Piper chaba steam extract as a reducing and stabilizing agent has been demonstrated. The formation of stable IONPs coated with organic moieties was confirmed from UV-vis, FTIR, and EDX spectroscopy and DLS analysis. The produced IONPs are sufficiently crystalline to be superparamagnetic having a saturation magnetization value of 58 emu/g, and their spherical form and size of 9 nm were verified by XRD, VSM, SEM, and TEM investigations. In addition, the synthesized IONPs exhibited notable effectiveness in the removal of Congo Red (CR) dye with a maximum adsorption capacity of 88 mg/g. The adsorption kinetics followed pseudo-second-order kinetics, meaning the adsorption of CR on IONPs is mostly controlled by chemisorption. The adsorption isotherms of CR on the surface of IONPs follow the Langmuir isotherm model, indicating the monolayer adsorption on the homogeneous surface of IONPs through adsorbate-adsorbent interaction. The IONPs have revealed good potential for their reusability, with the adsorption efficiency remaining at about 85% after five adsorption-desorption cycles. The large-scale, safe, and cost-effective manufacturing of IONPs is made possible by this environmentally friendly process.

Removal of lead ions (Pb2+) from aqueous solution using chitosan/starch composite material: Experimental and density functional theory findings

AbstractTreatment of wastewater has become vital to prevent environmental pollution in recent years. Adsorption is an easily applicable, low-cost and efficient method and is the subject of this study. In this study, an adsorbent was synthesized to be used in heavy metal removal using chitosan and starch. The composite was characterized by Fourier transform infrared (FTIR) spectrophotometry, X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis. It was determined that the composite had an amorphous and compact structure. Adsorption experiments were carried out under the optimized parameters such as solution pH, concentration, adsorbent amount, equilibrium time, and temperature. It shows that during adsorption, with the increase in pH, the adsorption efficiency and adsorption capacity first increase and then a fluctuation occurs. The highest adsorption efficiency and Q value were reached at pH 3.46 as 78% and 0.038 mol/kg, respectively. Moreover, the adsorption capacity (Q) reached its highest value with a value of 0.067 mol/kg in the presence of 30 mg adsorbent. Equilibrium experiments were validated by the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. To investigate the adsorption mechanism, pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models were used. It was determined that the adsorption process followed the D-R isotherm (R2 = 0.99) and PSO (R2 = 0.99). Therefore, the existence of chemical adsorption can be mentioned. Thermodynamic parameters enthalpy (∆H), Gibbs free energy (∆G) and entropy change (∆S) were investigated. The adsorbate-adsorbent interactions were studied by density functional theory (DFT).

In Situ Single-crystal X-ray Diffraction Studies of Physisorption and Chemisorption of SO2 within a Metal-Organic Framework and Its Competitive Adsorption with Water.

Living on an increasingly polluted planet, the removal of toxic pollutants such as sulfur dioxide (SO2) from the troposphere and power station flue gas is becoming more and more important. The CPO-27/MOF-74 family of metal-organic frameworks (MOFs) with their high densities of open metal sites is well suited for the selective adsorption of gases that, like SO2, bind well to metals and have been extensively researched both practically and through computer simulations. However, until now, focus has centered upon the binding of SO2 to the open metal sites in this MOF (called chemisorption, where the adsorbent-adsorbate interaction is through a chemical bond). The possibility of physisorption (where the adsorbent-adsorbate interaction is only through weak intermolecular forces) has not been identified experimentally. This work presents an in situ single-crystal X-ray diffraction (scXRD) study that identifies discrete adsorption sites within Ni-MOF-74/Ni-CPO-27, where SO2 is both chemisorbed and physisorbed while also probing competitive adsorption of SO2 of these sites when water is present. Further features of this site have been confirmed by variable SO2 pressure scXRD studies, DFT calculations, and IR studies.

KOH-mediated structural modification of activated charcoal by heat treatment for the efficient adsorption of organic dyes

Modification of the structural features of activated charcoal by KOH-mediated heat treatment is reported. Improved adsorption of rhodamine B (RhB) and methyl orange (MO) is observed, which is dependent on the KOH/precursor ratio. At the optimum ratio of 2:1, the removal of RhB is (92 ± 2)% and that of MO is (82 ± 1)% in 15 min. The influence of contact time, adsorbent dose, adsorbate concentration and temperature on the adsorption are analyzed. The kinetics and equilibrium studies are also carried out. The process follows pseudo-second-order kinetics for both the dyes. The Langmuir isotherm results in the best linear fit with a monolayer adsorption capacity of 312.5 mg g-1 in the case of RhB adsorption and 188.7 mg g-1 for MO adsorption. Thermodynamic studies reveal the predominance of chemisorption in the removal of RhB, whereas in the case of MO, physisorption is favoured. The versatility in removing various organic dyes is evident from the ∼100% removal of methylene blue (MB), malachite green (MG), crystal violet (CV) dyes as well as a 1:1 mixture of RhB and MO. The structure and chemical composition before and after activation is analyzed. The activation results in a significant improvement in specific surface area from 787.9 to 975.4 m2g-1 and an enhancement in the number of nanopores. The mechanism of adsorption is discussed in terms of the improved specific surface area, surface functionalization and the resultant adsorbent-adsorbate interactions.

Measurement of Surface Diffusion at Electrochemical Interfaces Using in Situ Linear Optical Diffraction

Surface diffusion processes play an important role in many reactions at electrode surfaces and are of relevance to electrocatalysis, electrodeposition, and many other areas. Such processes have therefore been extensively studied on solids under vacuum conditions with a variety of different methods. In sharp contrast, only few studies exist to measure surface diffusion in electrochemical environment due to the lack of suitable methodology. We aim on partially filling this gap by introducing the all-optical in situ LOD methodology, which allows to measure surface diffusion rates over a wide range and thus overcomes limitations of established methods that are mostly restricted to slow diffusion rates. The method is based on the generation of a periodic spatial modulation of adsorbates using two interfering laser pulses. The subsequent equilibration of this pattern and thus the diffusion rate of adsorbates is probed by the linear optical diffraction (LOD) signal from a second laser.First proof-of-principle measurements were performed on sulfur diffusion on the Pt(111) electrode. For this purpose, the optical and electrochemical properties of this systems were investigated first, including studies of the optical reflectance change induced by chemisorbed sulfur (Sad) and investigations of the Sad oxidation mechanism. The subsequent studies of Sad surface diffusion revealed potential and coverage dependent diffusion rates which were at least an order of magnitude faster than under vacuum conditions. Supported by numerical simulations, the implications of strong adsorbate-adsorbate interaction combined with different grating modulation depths to the temporal evolution of the LOD signal were demonstrated and data accuracy and pitfalls of the method were discussed.Kattwinkel and Magnussen, ACS Meas. Sci. Au, in press (2023), https://doi.org/10.1021/acsmeasuresciau.2c00066Kattwinkel and Magnussen, Electrochimica Acta 434, 141297 (2022), https://doi.org/10.1016/j.electacta.2022.141297

Design of Cu-based bimetals for ammonia catalytic combustion via DFT-based microkinetic modeling

Copper and its oxides possess excellent performance for ammonia catalytic combustion, but further improving the catalytic performance is still impeded by the limited understanding of the reaction mechanism. Herein, a density functional theory-based microkinetic study by considering the adsorbate-adsorbate interactions was performed to uncover the reaction mechanism under experimental conditions and further design the superior Cu-based bimetal catalysts. Our calculations demonstrate that the partially oxidized Cu(111) covered by oxygen atoms is the active phase. The ammonia consumption rate is not only constrained by strong adsorption of NH and O species but also suppressed by elementary reactions of NH coupling and O-assisted NH3 dehydrogenation from 400 to 800 K. Subsequently, two Cu-based bimetal catalysts, CuAg3 and CuAu3, cautiously designed by weakening the adsorption of NH and O species and reducing the activation barriers of the two rate-determining steps, possess superior catalytic performance than the copper in ammonia catalytic combustion. Overall, our studies not only reveal the reaction mechanism of ammonia catalytic combustion on Cu(111) but also provide important insights for the design of optimal catalysts including two predicted Cu-based bimetal catalysts.

Regulating the electronic microenvironment of adsorption sites in nanofiber for promoting In(III) capture performance

Enhancing adsorbent-adsorbate interactions via rational construction of adsorption sites is essential for the capture of the strategic metal indium. Herein, a nanofiber (PCA-Nanofiber) was successfully fabricated for In(III) ions recovery by introducing an electronegative fluorine-containing group to modulate the electronic structure of adsorption sites. Adsorption experiments exhibited that the maximum adsorption of PCA-Nanofiber for In(III) ions (116.3 mg/g) was 3.3 times higher than that of the pre-regulated nanofiber, exceeding most of the reported adsorbents. The PCA-Nanofiber maintained stable performance in five consecutive adsorption–desorption experiments and exhibited excellent selectivity. Furthermore, advanced spectroscopic characterization revealed that the adsorbed complex presented in a six-coordinated octahedral configuration, resembling an anti-triangular prism configuration centered on In(III) ions. The density functional theory demonstrates that the excellent adsorption performance benefits from the electronegative F atoms modulating the electronic microenvironment of the adsorption sites and optimizing the band-gap energy for charge migration, resulting in efficiently driven charge transfer. This work offers ideas for the rational design of adsorption sites in nanofiber from the perspective of regulation of electronic microenvironmental.

IMPREGNATED ACTIVATED CARBON MATERIALS FOR RESPIRATORY PURPOSE. CHEMISORPTION OF SULFUR DIOXIDE

The review is devoted to the use of impregnated activated carbon materials as chemisorbents of sulfur (IV) oxide. General methods for obtaining ordinary activated carbon, preparation of raw materials, their chemical activation with alkalis and acids followed by heat treatment (carbonization) in an inert environment or in the presence of a gaseous oxidizer, the role of acid-base and redox catalysts in this process are considered. The influence of the chemical composition of the activated carbon surface, the presence of functional groups, and their acid-base properties, as well as the products of surface reactions on the peculiarities of sulfur (IV) oxide adsorption is analyzed from the point of view of SO2 removal efficiency and the possibility of SO2 regeneration. An important role in these processes is played by the pore size, the possibility of co-adsorption of water, and the presence of an oxidant. The nature of adsorbent-adsorbate interactions on the surface of activated carbon, their ener­gy, in particular, the contribution of so-called "physical" adsorption, van der Waals forces, hydrogen bonding, and the influence of surface functional groups are discussed. The activation of carbon raw materials with nitrogen-containing compounds leads to the N-doping of the surface, which increases the efficiency of SO2 adsorption, facilitating not only van der Waals and electrostatic interactions, but also S←N binding. The influence of oxygen and oxygen-containing functional groups on SO2 adsorption is also discussed. To obtain impregnated activated carbon for SO2 absorption, the original activated carbon of the required quality is impregnated with solutions of inorganic and organic compounds that remain on the inner surface of the activated carbon after drying. Impregnation blocks partly the porosity of activated carbon, but makes it more capable of chemical adsorption. Chemisorption, in which certain chemical bonds are formed between the surface of the activated carbon and the compound being adsorbed, is more selective than physical adsorption, where the size of molecules is critical for an effective capture process. It can be noted that unlike inorganic alkalis, which spoil the porous structure of activated carbon, treatment with a solution of ammonia or organic N-containing bases promotes SO2 absorption. A special place in gas purification is occupied by activated carbon impregnated with ionic liquids, non-aqueous solvents being used for impregnation. A separate issue of the chemisorption of sulfur (IV) oxide by samples of impregnated activated carbon based on d-metals will be discussed in detail below.

Investigating Spillover Energy as a Descriptor for Single-Atom Alloy Catalyst Design.

The identification of thermodynamic descriptors of catalytic performance is essential for the rational design of heterogeneous catalysts. Here, we investigate how spillover energy, a descriptor quantifying whether intermediates are more stable at the dopant or host metal sites, can be used to design single-atom alloys (SAAs) for formic acid dehydrogenation. Using theoretical calculations, we identify NiCu as a SAA with favorable spillover energy and demonstrate that formate intermediates produced after the initial O-H activation are more stable at Ni sites where rate-determining C-H activation occurs. Surface science experiments demonstrated that NiCu(111) SAAs are more reactive than Cu(111) while they still follow the formate reaction pathway. However, reactor studies of silica-supported NiCu SAA nanoparticles showed only a modest improvement over Cu resulting from surface coverage effects. Overall, this study demonstrates the potential of engineering SAAs using spillover energy as a design parameter and highlights the importance of adsorbate-adsorbate interactions under steady-state operation.

Review on Moringa oleifera, a green adsorbent for contaminants removal: characterization, prediction, modelling and optimization using Response Surface Methodology (RSM) and Artificial Neural Network (ANN)

Moringa oleifera utilization in water treatment to eliminate emerging pollutants such as heavy metal ions, pesticides, pharmaceuticals, and pigments has been extensively evaluated. The efficacy of Moringa oleifera biosorbent has been investigated in diverse research work using various techniques, including its adsorption capacity kinetic, thermodynamic evaluation, adsorbent modifications, and mechanism behind the adsorption process. The Langmuir isotherm provided the most remarkable experimental data fit for batch adsorption investigations, whereas the best fit was obtained with the pseudo-second order kinetic model. Furthermore, only a few papers that combined batch adsorption with fixed-bed column investigations were examined. In the latter articles, the scientists modified the adsorbent to increase the material’s adsorption capacity as determined by analytical methods, including IR spectroscopy, scanning electronic microscope (SEM), and X-ray diffraction (XRD). However, the raw material can show appreciable adsorption capacity values, proving moringa’s potency as a biosorbent. Hydrogen bonds, electrostatic interaction, and van der Waals forces were the main processes in the found and reported adsorbent-adsorbate interactions. These mechanisms could change depending on the physiochemical nature of adsorption. Although frequently employed for heavy metal ions and dye adsorption, Moringa oleifera can still be explored in pesticide and medication adsorption investigations due to the few publications in this comprehensive review. This study, therefore, examined different Adsorbents from the Moringa oleifera plant, as well as parameters and models for enhancing the adsorption process.

Unary Adsorption Equilibria of Hydrogen, Nitrogen, and Carbon Dioxide on Y-Type Zeolites at Temperatures from 298 to 393 K and at Pressures up to 3 MPa.

The equilibrium adsorption of CO2, N2, and H2 on commercially available Zeolite H-Y, Na-Y, and cation-exchanged NaTMA-Y was measured up to 3 MPa at 298.15, 313.15, 333.15, 353.15, and 393.15 K gravimetrically using a magnetic suspension balance. The chemical and textural characterization of the materials was carried out by thermogravimetric analysis, helium gravimetry, and N2 (77 K) physisorption. We report the excess and net isotherms as measured and estimates of the absolute adsorption isotherms. The latter are modeled using the simplified statistical isotherm (SSI) model to evaluate adsorbate-adsorbent interactions and parametrize the data for process modeling. When reported per unit volume of zeolite supercage, the SSI model indicates that the saturation capacity for a given gas takes the same value for the three adsorbents. The Henry's constants predicted by the model show a strong effect of the cation on the affinity of each adsorbate.

Interaction mechanism of phytic acid functionalized graphene oxide with ionic dyes

Phytic acid functionalized graphene oxide (PA-GO) has fascinating application in environmental remediation. Herein, PA-GO was facilely prepared via hydrothermal method and utilized as adsorbent to remove aqueous Congo red (CR) and malachite green (MG). The adsorbent-adsorbate interaction mechanism was elaborately scrutinized based on the hard and soft acid base (HSAB) principle, spectroscopic analysis and adsorption fitting. Result shows, after five consecutive cycles, PA-GO maintains adsorption quantity 242.82 mg·g−1 and 117.53 mg·g−1 for CR and MG, respectively. The HSAB principle illuminates, primary interaction of PA-GO with both CR and MG is provided by phytic acid moiety (PA). For CR adsorption, electron of N atom in –NH2 group flows towards O atom in OH and O(-O-) of PA. While for MG adsorption, electron of N atom in (CH3)2N– group flows towards O atom in OH and O(-O-) of PA. FTIR, UV–Vis analyses supports the HSAB principle prediction. In brief, the hydroxyls and phosphoric groups introduced by PA functionalization enhance the adsorption affinity of GO. Adsorption of CR, MG by PA-GO under favorable pH is thermodynamically chemical but kinetically impelled by electrostatic interaction. This work may promote the development of efficient adsorbent based on PA-GO architecture for environmental remediation.