Determination Of Adsorption Isotherms Research Articles

Static and dynamic methods to determine adsorption isotherms of hemp seed (Cannabis sativa L.) with different percentages of dockage.

Adsorption and desorption isotherms of hemp seeds with 0%, 5%, 10%, 15%, and 20% of dockage were determined using the salt solution static (SSS) method. The wet hemp seeds with 0% dockage were also dried at 30℃ with 50% RH, 35℃ with 30% and 50% RH, and 40℃ with 30% and 50% RH inside a thin‐layer dryer (thin‐layer dynamic method). The hemp seeds with different percentages of dockage showed hysteresis, and this hysteresis became more obvious with the decrease of temperature. At the same condition, the equilibrium moisture content of hemp seeds with 0% dockage was approximately 0.5 percent points lower than that of the hemp seeds with dockage. The best equation to fit the equilibrium moisture content data under constant temperature and RH was the modified GAB equation for both adsorption and desorption isotherms. The constant rate period of drying was observed for <0.75 hr when drying air RH was 30% or when drying air temperature was 40℃. The Henderson and Pabis model was the best model to fit the thin‐layer drying data. The equilibrium moisture contents measured by the SSS method were lower than those measured by the thin‐layer dynamic method when temperature was ≤35℃.

Formation of Supramolecular Clusters at the Interface of Zeolite X Following the Adsorption of Rare-Earth Cations and Their Impact on the Macroscopic Properties of the Zeolite.

The adsorption behavior of neodymium (Nd3+ ) and yttrium (Y3+ ) cations on synthetic FAU zeolite X in its sodium form (NaX) has been investigated by means of macroscopic (adsorption isotherm determination and thermal analysis) and microscopic measurements (including solid-state NMR spectroscopy and X-ray powder diffraction). The multidisciplinary study reveals some unexpected features. Firstly, adsorption constants of cations are not correlated to their ionic radii or hydration enthalpy. The adsorption constant of Y3+ on NaX was indeed about twice that of Nd3+ , which is the opposite of what could be expected based on the size of the cations. In addition, adsorption was accompanied by partial dealumination of the zeolite framework. The extent of dealumination changed depending on the exchanged cations, with the extent being more significant on the Nd-exchanged zeolite than on the Y-exchanged one. The most interesting finding of this study, however, is the presence of supramolecular clusters composed of water, Nd3+ , residual sodium ions, and extra-framework aluminum at the interface of Nd-exchanged zeolite. The hypothesis that these host-guest complexes are responsible of the significantly different behavior exhibited by NaX towards the adsorption/desorption of Nd3+ and Y3+ has been formulated.

Determination of the absolute adsorption/desorption isotherms of CH4 and n-C4H10 on shale from a nano-scale perspective

Accurate description of absolute adsorption/desorption behavior for hydrocarbons on shale is of critical importance to the understanding of the fundamental mechanisms governing the storage, transport, and recovery of shale gas or shale gas condensate in shale reservoirs. By applying a thermogravimetric method, we first measure the excess adsorption/desorption isotherms of pure CH4 and n-C4H10 on shale samples over the temperature range of 303.15–393.15 K. The maximum test pressures considered for CH4 and n-C4H10 are 50 bar and 2 bar, respectively. Grand Canonical Monte Carlo (GCMC) simulations are then applied to calculate the density of the adsorption phase by considering the fluid-pore surface interactions. We use such calculated density of the adsorption phase to calibrate the excess adsorption/desorption isotherms, which enables us to eventually obtain the absolute adsorption/desorption isotherms. Such approach for estimating the density of the adsorption phase is essentially different from the commonly used approaches in which the density of the adsorption phase is considered to be independent of temperature, pressure, and pore size.The adsorption/desorption test results show that both CH4 and n-C4H10 exhibit more adsorption as temperature decreases or pressure increases. Their adsorption/desorption isotherms exhibit hysteresis phenomenon and this phenomenon weakens as temperature increases. Comparatively, the hysteresis behavior observed for n-C4H10 is more obvious than that for CH4. Compared with CH4, n-C4H10 has higher adsorption capacity under the same condition, indicating its higher affinity towards the shale with organic matters. As for the conventional approaches, the density calculated from the van der Waals constant b or the liquid hydrocarbon density can be used to reasonably well evaluate the absolute adsorption isotherms of n-C4H10 on shale, but tends to underestimate the absolute adsorption of CH4 on shale. GCMC simulations show that the density of the adsorption phase is strongly correlated with system pressure, temperature, and pore size. Compared to the conventional approaches, GCMC simulations can better capture the in-situ density of adsorption phase; on the basis of the in-situ density of adsorption phase, we can then achieve more accurate determination of the absolute adsorption isotherms of a given hydrocarbon on shale. This study raises the imperativeness of leveraging more sophisticated simulation tools (such as GCMC) for more accurate determination of absolute adsorption isotherms.

Removal of dye from synthetic textile wastewater using agricultural wastes and determination of adsorption isotherm

Reactive dyes have been applying extensively in textile industries. The treatment of textile industry waste waters is one of the main concerns of environmental health experts due to having excessive dyes and pollution. The aim of this study was to remove the Reactive Black 5 (RB5) dye from synthetic textile waste waters using agricultural wastes and determination of adsorption isotherm. In this research, Glycyrrhiza glabra root ash was prepared in laboratory condition and graded by standard sieve. The reactive Black 5 dye removals from textile synthetic wastewater using this adsorbent were tested. The effect of some parameters such as contact time (10–180 min), initial dye concentration (20, 40 and 60 mg/g) adsorbent dosage (0.2–2 g) and pH (2–12) were evaluated. Measurements were performed using an ultra violet-visible spectrophotometer at a wavelength of 597 nm and adsorption isotherm analyses were carried out. The results showed that data follow better the Langmuir adsorption model and the RL = 0.1123 was in the range of 0 to 1. Adsorption efficiency was reduced with increasing initial dye concentration and decreasing the adsorbent dosage. According to the results, the remaining root as an agricultural waste showed proper efficiency economically for the removal of dyes from textile industry wastewater

Adsorption behavior of optical brightening agent on microfibrillated cellulose studied through inverse liquid chromatography: The need to correct for axial dispersion effect

Inverse liquid chromatography is a technique for studying solid/liquid interaction and most specifically for the determination of solute adsorption isotherm. For the first time, the adsorption behaviour of microfibrillated cellulose was assessed using inverse liquid chromatography. We showed that microfibrillated cellulose could adsorb 17 mg/g of tetrasulfonated optical brightening agent in typical papermaking conditions. The adsorbed amount of hexasulfonated optical brightening agent was lower (7 mg/g).The packing of the column with microfibrillated cellulose caused important axial dispersion (Da = 5e-7 m²/s). Simulation of transport phenomena in the column showed that neglecting axial dispersion in the analysis of the chromatogram caused significant error (8%) in the determination of maximum adsorbed amount. We showed that conventional chromatogram analysis technique such as elution by characteristic point could not be used to fit our data. Using a bi-Langmuir isotherm model improved the fitting, but did not take into account axial dispersion, thus provided adsorption parameters which may have no physical significance. Using an inverse method with a single Langmuir isotherm, and fitting the transport equation to the chromatogram was shown to provide a satisfactory fitting to the chromatogram data. In general, the inverse method could be recommended to analyse inverse liquid chromatography data for column packing with significant axial dispersion (Da > 1e-7 m²/s).

Interpretation of Gibbs surface excess model for gas adsorption on heterogeneous coal particle

Sorption kinetics measurement is the essential prerequisite of constructing adsorption isotherms in the research field of coalbed methane production and CO2 injection, however, Difficulty arises from the fact that sorption kinetics measurement is found to be accompanied by thermodynamic effect (e.g. fluctuation of temperature and pressure); that is, it has a strong dependence on the accuracy of models and methods of adsorption isotherm. In this regard, a new model analogous to Gibbs surface excess (GSE) adsorption is presented in this study for gas adsorption on heterogeneous coal particle in the interest of interpretation and application the GSE theory to the sorption kinetics measurement. According to this model, alternative method of adsorption isotherm calculation is developed in this paper, which suggests that thermodynamic parameters of adsorption measurement are detected in a contrasting and synchronous manner and thus enable the validity of adsorption data to be judged more accurately. Furthermore, feasibility tests were performed and results showed that the current model and method of adsorption isotherm determination could be used to improve experimental accuracy for the integral and incremental sorption step measurements.

PENJERAPAN ZAT WARNA SINTETIS MENGGUNAKAN KARBON AKTIF KELAPA SAWIT DAN PENGEMBANGANNYA SEBAGAI BAHAN AJAR

This study aims to: (1) explain the ability of the active carbon absorption of Palm Oil Palm as a dye adsorbent Reactive Red and Direct Green (2) determines the pH, contact time, and weight of the optimum adsorbent and the influence of temperature using activated carbon. Reactive Red and Direct Green dyestuffs. (3) to explain the influence of video media usage on the improvement of learning result and critical thinking ability of students in Chemistry class XI MIPA E at SMAN 2 Kota Bengkulu. The procedure in this study is the activation of activated carbon of palm oil and activated, activated carbon characterization using FTIR, Determination of maximum wavelength (?), Calibration curve creation, Adsorption of substance by activated carbon of palm oil: determining pH, contact time, adsorbent weight, , adsorption isotherms, Determination of temperature effect, Adsorption Isotherm Determination, Determination of adsorption kinetics, Applications on dyestuffs. The data were analyzed. The result of pH variation, variation of adsorbent weight, and contact time were made curve so that pH, adsorbent weight, concentration and optimum contact time were obtained using Excel program. Using ANAVA one way, followed by KR-20 test and one sample t test. The results showed that there were: reactive red optimum wavelength 496 nm, optimum pH 3, optimum time 40 min, absorbent weight 150 mg, maximum absorbency KAPKS 32,73 mg / gr and direct green optimum wavelength 613 nm, with optimum pH 5, optimum time 40 minutes, absorbent weight 150 mg, maximum absorbency KAPKS 32.825 mg / gr. there is an increase of chemistry learning outcomes during the enrichment hours or outside of class hours and critical thinking skills of grade XI IPA E SMAN2 Kota Bengkulu using audio-visual media with average pretest score of 75 and average post test score 82.27 with four criteria critical thinking skills are less critical by 26%, critical enough 43%, critical 23% and very critical at 8%.

Penjerapan Zat Warna Sintetis Menggunakan Karbon Aktif Kelapa Sawit Dan Pengembangannya Sebagai Bahan Ajar

This study aims to: (1) explain the ability of the active carbon absorption of Palm Oil Palm as a dye adsorbent Reactive Red and Direct Green (2) determines the pH, contact time, and weight of the optimum adsorbent and the influence of temperature using activated carbon. Reactive Red and Direct Green dyestuffs. (3) to explain the influence of video media usage on the improvement of learning result and critical thinking ability of students in Chemistry class XI MIPA E at SMAN 2 Kota Bengkulu. The procedure in this study is the activation of activated carbon of palm oil and activated, activated carbon characterization using FTIR, Determination of maximum wavelength (?), Calibration curve creation, Adsorption of substance by activated carbon of palm oil: determining pH, contact time, adsorbent weight, , adsorption isotherms, Determination of temperature effect, Adsorption Isotherm Determination, Determination of adsorption kinetics, Applications on dyestuffs. The data were analyzed. The result of pH variation, variation of adsorbent weight, and contact time were made curve so that pH, adsorbent weight, concentration and optimum contact time were obtained using Excel program. Using ANAVA one way, followed by KR-20 test and one sample t test. The results showed that there were: reactive red optimum wavelength 496 nm, optimum pH 3, optimum time 40 min, absorbent weight 150 mg, maximum absorbency KAPKS 32,73 mg / gr and direct green optimum wavelength 613 nm, with optimum pH 5, optimum time 40 minutes, absorbent weight 150 mg, maximum absorbency KAPKS 32.825 mg / gr. there is an increase of chemistry learning outcomes during the enrichment hours or outside of class hours and critical thinking skills of grade XI IPA E SMAN2 Kota Bengkulu using audio-visual media with average pretest score of 75 and average post test score 82.27 with four criteria critical thinking skills are less critical by 26%, critical enough 43%, critical 23% and very critical at 8%.

Steel-Making dust as a potential adsorbent for the removal of lead (II) from an aqueous solution

The presence of high concentrations of toxic heavy metals such as lead Pb(II) in water is a major hazard to human health and may have a detrimental effect on the aquatic life and the environment. Implementing an efficient and economical treatment method for the reduction of Pb(II) is a major challenge that is being addressed through employing such processes as adsorption, utilizing low cost adsorbents. In this study, Steel-Making dust obtained from a local Steel Factory was utilized for the adsorption of lead Pb(II) from an aqueous solution. The determination of optimum pH condition, adsorption isotherms and kinetics studies were carried out. The experimental data were fitted to five different isotherms, including Langmuir, Freundlich, Sips, Dubinin-Radushkevich and exponential models; while the kinetic data were fitted to Pseudo-first order, Pseudo-second order, Elovich’s and intraparticle diffusion models. The fitting of the isotherm experimental data to the five isotherm models was compared through the Akaike Information Criterion (AIC). The Dubinin-Radushkevich model was found to best describe the experimental data for the adsorption of lead ions onto Ladle furnace and cyclone steel dust with high Akaike weight (wi) of 0.91 and 0.83, respectively. The optimum pH range was found to be around 4–5; working within this range prevents lead precipitation during the adsorption process. The maximum adsorption capacity for lead on Steel Dust as obtained from the Langmuir isotherm was 208.9 mg/g for the Ladle Furnace steel dust, and 39.8 mg/g for the Cyclone steel dust. Overall, the Steel-Making dust gave a high efficiency for the reduction of lead concentration in the aqueous solutions and thus could be utilized in industrial adsorption processes.

Sensitive Detection of Competitive Molecular Adsorption by Surface-Enhanced Raman Spectroscopy

Surface adsorption plays a critical role in a wide variety of fields from surface catalysis to molecular separation. Despite the importance, limited access to simultaneously sensitive and selective detection mechanisms has hampered the acquisition of comprehensive and versatile experimental data needed to understand the complex aspects of mixture adsorption, calling for a molecular detection method capable of obtaining the surface adsorption isotherms over a wide range of concentrations as well as distinguishing the competitive adsorption of different adsorbates. Here, we test surface-enhanced Raman spectroscopy (SERS) as an effective analysis tool of surface adsorption phenomena. Using a sensitive SERS substrate, we characterize the adsorption isotherms of chemical species of various binding energies. We obtained the isotherms for strongly binding species in a concentration range from subpicomolar to micromolar. A log-sigmoidal dependency of the SERS signals to the analyte concentration could be modeled by surface binding theories accurately using molecular dynamics simulations, thereby bringing out the potential capability of sensitive SERS for describing a single-compound adsorption process. SERS also enabled the determination of competitive adsorption isotherms from a multiple-compound solution for the first time. The successful demonstration of the sensitive and selective characterization of surface adsorption lends SERS adaptability to a cheap, facile, and effective solution for chemical analysis.

Adsorption of methylene blue and malachite green on micro-mesoporous carbon materials

The aim of this work was to investigate the determination of adsorption kinetics and adsorption isotherms for methylene blue (MB) and malachite green (MG) from aqueous solutions, on micro-mesoporou...

Adsorption of sulfur dioxide and mixtures with nitrogen at carbon nanotubes and graphene: molecular dynamics simulation and gravimetric adsorption experiments

The adsorption of sulfur dioxide (SO\(_{2}\)), nitrogen (N\(_{2}\)) and mixtures of both on carbon nanotubes (CNTs) and graphene was studied by molecular dynamic simulation. Experimental results from gravimetric adsorption of SO\(_{2}\) and N\(_{2}\) on CNTs are compared to simulated data. CNTs with a rigid and a flexible model and the diameters 1.48 and 2.69 nm were simulated. For graphene, SO\(_{2}\) and N\(_{2}\) rigid models were applied. Besides the CNT diameters, different system temperatures, compositions of SO\(_{2}\)/N\(_{2}\) mixtures were considered for selected cases of CNTs and graphene. By examining the local SO\(_{2}\) and N\(_{2}\) densities on the CNTs and graphene, adsorption could be observed. SO\(_{2}\) shows an enhanced adsorption compared to N\(_{2}\) on both CNTs and graphene. By varying the starting configurations of the simulation, different system pressures could be achieved, which allowed the determination of adsorption isotherms at different temperatures.

Adsorption of nitrate using diatomite-supported ferric oxide nanoparticles: determination of optimum condition, kinetics, and adsorption isotherms

Adsorption of nitrate using diatomite-supported ferric oxide nanoparticles: determination of optimum condition, kinetics, and adsorption isotherms

Review on the Determination of Frumkin, Langmuir, and Temkin Adsorption Isotherms at Electrode/Solution Interfaces Using the Phase-Shift Method and Correlation Constants

This review article described the electrochemical Frumkin, Langmuir, and Temkin adsorption isotherms of over-potentially deposited hydrogen (OPD H) and deuterium (OPD D) for the cathodic H2 and D2 evolution reactions (HER, DER) at Pt, Ir, Pt-Ir alloy, Pd, Au, and Re/normal (H2O) and heavy water (D2O) solution interfaces. The Frum-kin, Langmuir, and Temkin adsorption isotherms of intermediates (OPD H, OPD D, etc.) for sequential reactions (HER, DER, etc.) at electrode/solution interfaces are determined using the phase-shift method and correlation constants, which have been suggested and developed by Chun et al. The basic procedure of the phase-shift method, the Frumkin, Lang-muir, and Temkin adsorption isotherms of OPD H and OPD D and related electrode kinetic and thermodynamic param-eters, i.e., the fractional surface coverage (0 ≤ θ ≤ 1) vs. potential (E) behavior (θ vs. E), equilibrium constant (K), interaction parameter (g), standard Gibbs energy (ΔGθ˚) of adsorption, and rate (r) of change of ΔGθ˚ with θ (0 ≤ θ ≤ 1), at the interfaces are briefly interpreted and summarized. The phase-shift method and correlation constants are useful and effective techniques to determine the Frumkin, Langmuir, and Temkin adsorption isotherms and related electrode kinetic and thermodynamic parameters (θ vs. E, K, g, ΔGθ˚, r) at electrode/solution interfaces.

Adsorption of Butanol and Water Vapors in Silicalite-1 Films with a Low Defect Density.

Pure silica zeolites are potentially hydrophobic and have therefore been considered to be interesting candidates for separating alcohols, e.g., 1-butanol, from water. Zeolites are traditionally synthesized at high pH, leading to the formation of intracrystalline defects in the form of silanol defects in the framework. These silanol groups introduce polar adsorption sites into the framework, potentially reducing the adsorption selectivity toward alcohols in alcohol/water mixtures. In contrast, zeolites prepared at neutral pH using the fluoride route contain significantly fewer defects. Such crystals should show a much higher butanol/water selectivity than crystals prepared in traditional hydroxide (OH-) media. Moreover, silanol groups are present at the external surface of the zeolite crystals; therefore, minimizing the external surface of the studied adsorbent is important. In this work, we determine adsorption isotherms of 1-butanol and water in silicalite-1 films prepared in a fluoride (F-) medium using in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. This film was composed of well intergrown, plate-shaped b-oriented crystals, resulting in a low external area. Single-component adsorption isotherms of 1-butanol and water were determined in the temperature range of 35-80 °C. The 1-butanol isotherms were typical for an adsorbate showing a high affinity for a microporous material and a large increase in the amount adsorbed at low partial pressures of 1-butanol. The Langmuir-Freundlich model was successfully fitted to the 1-butanol isotherms, and the heat of adsorption was determined. Water showed a very low affinity for the adsorbent, and the amounts adsorbed were very similar to previous reports for large silicalite-1 crystals prepared in a fluoride medium. The sample also adsorbed much less water than did a reference silicalite-1(OH-) film containing a high density of internal defects.The results show that silicalite-1 films prepared in a F- medium with a low density of defects and external area are very promising for the selective recovery of 1-butanol from aqueous solutions.

An adjoint method in inverse problems of chromatography

How to determine adsorption isotherms is an issue of significant importance in chromatography. A modern technique of obtaining adsorption isotherms is to solve an inverse problem so that the simulated batch separation coincides with actual experimental results. In this work, as well as the natural least-square approach, we consider a Kohn–Vogelius type formulation for the reconstruction of adsorption isotherms in chromatography, which converts the original boundary fitting problem into a domain fitting problem. Moreover, using the first momentum regularizing strategy, a new regularization algorithm for both the Equilibrium-Dispersive model and the Transport-Dispersive model is developed. The mass transfer resistance coefficients in the Transport-Dispersive model are also estimated by the proposed inverse method. The computation of the gradients of objective functions for both of the two models is derived by the adjoint method. Finally, numerical simulations for both a synthetic problem and a real-world problem are given to show the robustness of the proposed algorithm.

Real-time adaptive input design for the determination of competitive adsorption isotherms in liquid chromatography

Abstract The adaptive input design (also called online redesign of experiments) for parameter estimation is very effective for the compensation of uncertainties in nonlinear processes. Moreover, it enables substantial savings in experimental effort and greater reliability in modeling. We present theoretical details and experimental results from the real-time adaptive optimal input design for parameter estimation. The case study considers separation of three benzoate by reverse phase liquid chromatography. Following a receding horizon scheme, adaptive D-optimal input designs are generated for a precise determination of competitive adsorption isotherm parameters. Moreover, numerical techniques for the regularization of arising ill-posed problems, e.g. due to scarce measurements, lack of prior information about parameters, low sensitivities and parameter correlations are discussed. The estimated parameter values are successfully validated by Frontal Analysis and the benefits of optimal input designs are highlighted when compared to various standard/heuristic input designs in terms of parameter accuracy and precision.

Synthesis, characterization of a metal organic framework: MIL-53 (Fe) and adsorption mechanisms of methyl red onto MIL-53 (Fe)

In this paper, MIL-53 (Fe), was synthesized and the adsorption interaction between this MOF and methyl red (MR) in an aqueous solution was studied. The structural characteristics, surface area, and thermal analysis of the synthesized MIL-53 (Fe) was carried out using XRD, TGA, TEM, and BET methods. The effects of the parameters such as initial concentration, contact time, adsorbent dosage, and temperature on the adsorption capacity were investigated for the determination of the best fit adsorption isotherm, adsorption kinetics, adsorption thermodynamics, and equilibrium time. It was found that the adsorption kinetics obeyed the pseudo-second-order kinetic model and an intraparticle diffusion model was also applied to understand the adsorption mechanism. The Langmuir and Freundlich adsorption isotherm models were also investigated. The results of the adsorption thermodynamics revealed that the adsorption of MR by selected MOF was a spontaneous and exothermic process. MIL-53 (Fe) opens its pores only in the presence of guest molecules. Its flexible structure leads to high adsorption capacities for MR.

Development and characterization of microwave-assisted activated carbons from Parkinsonea aculeata wood

Fil: Nunell, Gisel Vanesa. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

A surface thermodynamics approach to modelling single-file adsorption in ultramicroporous materials

A new thermodynamic approach is proposed to interpret adsorption equilibrium in ultramicropores with single-file adsorption. By considering the adsorbed phase as a one-dimensional fluid, phase equilibria thermodynamics can be used to derive a one-dimensional analogue of the monocomponent Gibbs adsorption isotherm. Equations such as Langmuir, Volmer, Fowler–Guggenheim or Hill–de Boer can thus be used as representations of phenomenological models of the one-dimensional adsorption system, rather than just as mathematical correlations. The bidirectional relation between the equations of state characterising the adsorbed phase and the adsorption isotherm equations allow great insight to be had simply by adsorption isotherm determination. In order to show the potential and limitations of this approach, the adsorption isotherms of Xe and CO2 in four crystalline hydrophobic dipeptides of the VA-class are analysed with this approach. It was possible to assess that adsorbate–adsorbate interactions are relevant for adsorption of both species, being attractive for Xe and repulsive for CO2; Xe adsorption is mainly distributed while CO2 adsorption is mainly localised.