Multicomponent Adsorption Isotherms Research Articles

Competitive Adsorption of Heavy Metals from Aqueous Solution onto Oxidized Activated Carbon Fiber

In this study, the competitive adsorption of Ni(II)–Pb(II) and Ni(II)–Zn(II) on oxidized activated carbon fiber (ACF-Ox) from aqueous solutions was studied. The experimental competitive adsorption data were interpreted by the following multicomponent adsorption isotherms: non-modified, extended, and modified Langmuir; non-modified and modified Redlich-Peterson; extended Freundlich; and Sheindorf-Rebuhn-Sheintuch. The extended Freundlich multicomponent isotherm best fitted the adsorption data for both systems Ni(II)–Pb(II) and Ni(II)–Zn(II) onto ACF-Ox. The single metal adsorption on ACF-Ox showed that the Ni(II) adsorption capacity was 1.12 times greater than that of Zn(II); however, in the competitive adsorption, the Zn(II) presented an intense antagonism to the adsorption of Ni(II) and Ni(II) to Zn(II) too. The single-adsorption isotherms of Pb(II) and Ni(II) on ACF-Ox revealed that the selectivity of Pb(II) towards ACF-Ox was slightly higher than that of the Ni(II). Nevertheless, in the competitive adsorption, the affinity of Pb(II) towards the ACF-Ox was far greater than that of the Ni(II).

An expanded Markham and Benton approach to describe multi-component adsorption of sugars on zeolite beta

Abstract Single- and multi-component adsorption isotherms of sorbitol, fructose, and glucose on zeolite beta (Na+BEA 150) were determined in sodium phosphate buffer using batch experiments. The standard Markham and Benton approach to predict binary isotherms from single-component data significantly overestimated the loading at high concentrations of two or more compounds. Therefore, an interaction parameter was introduced to the Markham and Benton model describing mutual blocking of binding sites in binary mixtures at high concentrations. With these changes, the expanded model was able to describe the multi-component isotherms of different binary mixtures in the concentration range from zero to 100 g/L for each compound. Moreover, the interaction parameters determined from binary isotherm data were used to predict ternary isotherms and a good agreement between model and experiments was achieved.

Nonideality in the Adsorption of Ethanol/Ethyl Acetate/Water Mixtures On ZIF-8 Metal Organic Framework

Fisher esterification of acetic acid (or acetic anhydride) with ethanol (EtOH) is the main industrial process for the synthesis of ethyl acetate (EA). Nonetheless, the separation of the produced ester from ethanol is challenging since these volatile organic compounds (VOCs) form an azeotropic mixture. In this work, the adsorption and separation EtOH/EA/water mixtures on the ZIF-8 metal–organic framework is studied. The present study aims to characterize the adsorptive behavior of ZIF-8 with non-ideal EtOH/EA/water mixtures. Single and multicomponent adsorption isotherms, obtained by gravimetry and breakthrough experiments, show high adsorption capacity and selectivity toward ethyl acetate. Pulse chromatography experiments confirm the higher interaction strength between EA and ZIF-8 in the low-pressure range at a low degree of pore filling (Henry’s region). The breakthrough profiles show development of intermediate plateaus in specific concentration ranges, with complex breakthrough evolution that has been...

Influence of Flexibility on the Separation of Chiral Isomers in STW-Type Zeolite.

Molecular simulation, through the computation of adsorption isotherms, is a useful predictive tool for the selective capacity of nanoporous materials. Generally, adsorbents are modelled as rigid frameworks, as opposed to allowing for vibrations of the lattice, and this approximation is assumed to have negligible impact on adsorption. In this work, this approach was tested in an especially challenging system by computing the adsorption of the chiral molecules 2-pentanol, 2-methylbutanol and 3-methyl-2-butanol in the all-silica and germanosilicate chiral zeolites STW and studying their lattice vibrations upon adsorption. The analysis of single- and multicomponent adsorption isotherms showed the suitability of STW-type zeolites as molecular sieves for chiral separation processes, which pose a challenging task in the chemical and pharmaceutical industries. Moreover, new experimental adsorption data validate the force field employed. The results reveal that the lattice vibrations of the all-silica framework are sorbate-independent, while those of germanosilicate STW show host-guest coupling modulated by uptake and sorbate type that disrupts the chiral recognition sites. This study indicates that the effects of intrinsic flexibility on the selective capacity of nanoporous materials may range from low to high impact, and some of them could not have been foreseen even after examination of the structural dynamics of an empty framework.

Statistical mechanics of binary mixture adsorption in metal-organic frameworks in the osmotic ensemble.

Although crucial for designing separation processes little is known experimentally about multi-component adsorption isotherms in comparison with pure single components. Very few binary mixture adsorption isotherms are to be found in the literature and information about isotherms over a wide range of gas-phase composition and mechanical pressures and temperature is lacking. Here, we present a quasi-one-dimensional statistical mechanical model of binary mixture adsorption in metal-organic frameworks (MOFs) treated exactly by a transfer matrix method in the osmotic ensemble. The experimental parameter space may be very complex and investigations into multi-component mixture adsorption may be guided by theoretical insights. The approach successfully models breathing structural transitions induced by adsorption giving a good account of the shape of adsorption isotherms of CO2 and CH4 adsorption in MIL-53(Al). Binary mixture isotherms and co-adsorption-phase diagrams are also calculated and found to give a good description of the experimental trends in these properties and because of the wide model parameter range which reproduces this behaviour suggests that this is generic to MOFs. Finally, a study is made of the influence of mechanical pressure on the shape of CO2 and CH4 adsorption isotherms in MIL-53(Al). Quite modest mechanical pressures can induce significant changes to isotherm shapes in MOFs with implications for binary mixture separation processes.This article is part of the theme issue 'Modern theoretical chemistry'.

Thermodynamic analysis of single and binary adsorption of Food Yellow 4 and Food Blue 2 on CC-chitosan: Application of statistical physics and IAST models

The paper is a complementary study of Food Yellow 4 and Food Blue 2 adsorption in single-compound and binary systems on modified chitosan (CC-chitosan), using statistical physics and Ideal Adsorbed Solution Theory (IAST) models. In order to provide new macroscopic interpretations of adsorption mechanisms, three thermodynamic functions were determined, such as configurationally entropy, free enthalpy and internal energy. The configurationally entropy trend showed that the dye molecules have plenty possibilities/positions to be docked on empty receptor sites at low concentrations, but limited possibilities at high equilibrium concentrations. The study of the free enthalpy and internal energy confirmed that the adsorption process in single-compound and binary systems is spontaneous. The second theoretical approach is based on the IAST model to predict the multicomponent adsorption isotherms using single-compound isotherm data. The IAST model provides a very good prediction of binary adsorption data, for both the adsorbates. Best results were obtained for Food Yellow 4 adsorption data; while for Food Blue 2 an increasing deviation between experimental and modeling binary adsorption data can be observed along with increasing concentration. Finally, the IAST model correctly described the decrease in adsorption capacity of both the dyes from single-compound to binary system, due to competition effects.

Modelling of Binary Isotherm Behaviour for the Adsorption of Catechol with Phenol and Resorcinol onto Rice Husk Ash

The present paper assesses the adsorption capability of rice husk ash (RHA) to adsorb catechol (C) along with phenol (P) and resorcinol (R) individually and simultaneously from aqueous solution in both single and binary solutions using batch experiments. Equilibrium isotherm data were collected at 30°C by carrying out experimental runs for 24 h contact time with pre-optimized RHA dosage of 20 mg/L and initial concentration variation of individual components in the range of 50–500 mg/L. The equilibrium adsorption data for single component were fitted in three adsorption isotherm models, namely the Langmuir, the Freundlich and the Redlich–Peterson. Equilibrium adsorption data of binary aqueous solution of catechol–phenol, catechol–resorcinol and the parameter evaluated from single adsorption isotherm were fitted in various multi-component adsorption isotherm models. Extended Langmuir model which assumes overlapping of sites for different adsorbates better represented the binary isotherm data for both catechol–phenol and catechol–resorcinol systems.

Predicting Multicomponent Adsorption Isotherms in Open-Metal Site Materials Using Force Field Calculations Based on Energy Decomposed Density Functional Theory.

For the design of adsorptive-separation units, knowledge is required of the multicomponent adsorption behavior. Ideal adsorbed solution theory (IAST) breaks down for olefin adsorption in open-metal site (OMS) materials due to non-ideal donor-acceptor interactions. Using a density-function-theory-based energy decomposition scheme, we develop a physically justifiable classical force field that incorporates the missing orbital interactions using an appropriate functional form. Our first-principles derived force field shows greatly improved quantitative agreement with the inflection points, initial uptake, saturation capacity, and enthalpies of adsorption obtained from our in-house adsorption experiments. While IAST fails to make accurate predictions, our improved force field model is able to correctly predict the multicomponent behavior. Our approach is also transferable to other OMS structures, allowing the accurate study of their separation performances for olefins/paraffins and further mixtures involving complex donor-acceptor interactions.

Multicomponent adsorption modeling: isotherms for ABE model solutions using activated carbon F-400

Biobutanol has attracted significant interest in recent decades and is seriously considered as a potential biofuel to partly replace gasoline. However, some production challenges must be addressed to make butanol economically viable such as the low product concentration and product toxicity inhibiting the microorganism. To alleviate these limitations, several in situ or ex situ separation techniques have been investigated in view of their integration to the biobutanol production process to enhance its economic viability. One of these techniques is adsorption which is one of the most energy-efficient techniques used for biobutanol separation. Considering the number of chemical species present in the ABE fermentation broth, it is essential to develop multicomponent adsorption isotherms for all components as a first step to design a high performance adsorption process. Few multicomponent isotherm models have been proposed such as multicomponent Langmuir and Freundlich. In this study, these two models as well as artificial neural networks were used to model the isotherms of each component in an ABE fermentation broth as a function of the equilibrium concentrations of all components for activated carbon F-400. Results showed that the multicomponent Langmuir model was not accurate due to the many simplifying assumptions. The multicomponent Freundlich and feedforward neural network (FFNN) isotherm models were able to predict the behavior of multicomponent systems very well. Indeed, the predictive model of the experimental data had a coefficient of determination (R2) of 0.97 and 0.99, for multicomponent Freundlich and FFNN isotherm models, respectively.

Modeling of single and competitive adsorption of cadmium and zinc onto activated carbon

This paper describes an experimental and modeling analysis of cadmium and zinc adsorption from aqueous solutions in single and binary systems on activated carbon. Batch tests were performed at constant pH (6.8 ± 0.3) and temperature (20 °C), in order to assess the adsorption capacity in experimental conditions simulating real wastewater. In particular, binary tests were carried out at same pH and temperature, with different initial concentration ratios of the two analytes (\(C_{Zn}^{0}\):\(C_{Cd}^{0}\)), in order to emphasize the competition phenomena while minimizing the effect of pH. Experimental results indicate that zinc is adsorbed to a greater extent than cadmium, both in single and binary systems. In binary systems, zinc adsorption capacity is not influenced by the presence of cadmium, regardless of its concentration. On the contrary, an increase in zinc concentration in solution brings about a decrease in cadmium adsorption capacity. The experiments were interpreted by using both the rigorous and the extended Langmuir multicomponent adsorption isotherms and the Vacancy Solution Theory. The latter provided a satisfactory and simultaneous description of the experimental data for both zinc and cadmium adsorption, also accounting for the possible interactions between the two analytes and between the solvent (water) and the single analyte.

Simultaneous adsorption of Cr(VI) and phenol onto tea waste biomass from binary mixture: Multicomponent adsorption, thermodynamic and kinetic study

During this investigation simultaneous removal of Cr(VI) and phenol using tea waste biomass is studied in a batch reactor. The influences of process parameters such as pH, adsorbent quantity, contact time, initial concentration on the percentage removal have been studied. The optimal pH condition for the adsorption of Cr(VI) was found acidic while that for phenol was basic but at pH 7 both phenol and Cr(VI) were adsorbed to maximum extent simultaneously onto the surface of tea waste biomass. At an optimum pH 7, temp 30°C, adsorbent dose 15gL−1, 99.19% of 100mgL−1 Cr(VI) and 95.07% of 50mgL−1 phenol were removed. The equilibrium was reached after 12h for Cr(VI) and 24h for phenol. The maximum adsorption capacity of tea waste biomass, according to extended Langmuir isotherm model was 199.523 and 9.487mgg−1 for Cr(VI) and phenol, respectively. Multicomponent adsorption isotherms such as non modified competitive Langmuir, modified competitive Langmuir, extended Langmuir, extended Freundlich, competitive non modified Redlich Peterson and competitive modified Redlich Peterson model were used to study the equilibrium process at the initial concentration range of 100–450mgL−1 of Cr(VI) and 50–225mgL−1 of phenol. The experimental results demonstrated that both Cr(VI) and phenol were well described by pseudo second order model. Thermodynamic study depicted that adsorption of phenol onto tea waste biomass was spontaneous and exothermic while for Cr(VI) was endothermic in nature.

Experimental Study of the Competitive Adsorption of HNO3 and H2O on Surfaces by Using Brewster Angle Cavity Ring-Down Spectroscopy in the 295–345 nm Region

The competitive adsorption of HNO3 and H2O from the gas phase onto fused silica surfaces is investigated. Brewster angle cavity ring-down spectroscopy is used to measure absorption of a laser probe beam by the HNO3/H2O coadsorbed on fused silica surfaces as a function of the mixture pressure. The laser absorption measurements were made in the 295-345 nm region. Langmuir adsorption constants for nitric acid and water were found to be 107 ± 17 and 562 ± 21 Torr(-1), respectively. A method has been developed for calculating absorption by HNO3 and H2O codeposited on the surface as a function of the HNO3/H2O mixture pressure using multicomponent Langmuir adsorption isotherms and absorption cross-sections at a given wavelength for surface-adsorbed HNO3 and H2O. The validity of this treatment has been evaluated both as a function of wavelength and as a function of mixing ratio.

Isotherm model for high-temperature, high-pressure adsorption of and on K-promoted hydrotalcite

Sorption-enhanced water-gas shift (SEWGS) combines the water–gas shift reaction with in situ adsorption of CO2 on potassium-promoted hydrotalcite (K-HTC) and thereby allows production of hot, high pressure H2 from syngas in a single process. SEWGS is a cyclic process, that comprises high pressure adsorption and rinse, pressure equalisation, and low pressure purge. In order to design the SEWGS process, the equilibria and kinetics of adsorption must be known for the entire pressure range. Here, a multicomponent adsorption isotherm is presented for CO2 and H2O on K-HTC at 400 °C and 0.5–24 bar partial pressure, that has been derived from integrated experimentally determined breakthrough curves with special attention being given to the high pressure interaction. The experimental results can be well described by assuming that the isotherm consists of a low partial pressure surface adsorption part and a high partial pressure nanopore adsorption part. Surface adsorption occurs at specific and different sites for CO2 or H2O. In contrast, the nanopore adsorption mechanism is competitive and explains the interaction observed in the capacity data at partial pressures over 5 bar. Based on the characteristics of the sorbent particles, a linear driving force relation has been derived for sorption kinetics. Adsorption isotherm and linear driving force kinetics have been included in a reactor model. Model predictions are in agreement with breakthrough as well as regeneration experiments.

POTENTIAL OF CORN HUSK LEAVES FOR THE CO-REMOVAL OF PHENOL AND CYANIDE FROM WASTE WATER USING SIMULTANEOUS ADSORPTION AND BIODEGRADATION

Application of biosorbents has gained a great importance in the present scenario of waste water purification. The present work concentrates on the potential of biosorbent, Corn husk leaves, for the co-removal of phenol and cyanide from coke waste water by simultaneous adsorption and biodegradation (SAB). The microbe used in the present study is the bacteria of Serratia Sp. The entire SAB process was carried out at 30 0 C and for 60 h. Theoptimum process parameters i.e. pH, initial concentration of both phenol and cyanide, adsorbent dose of corn husk leaves were analysed and their impact on the entire process were also studied. At the range of initial concentration of phenol between 100-1000 mg/L and cyanide between 10-100 mg/L, the optimum pH was obtained between 6.57 and an optimum adsorbent dose of 6 g/L. Multicomponent adsorption isotherms applied were Non-modified Langmuir, Modified Langmuir, Extended Langmuir and Extended Freundlich. Out of the four isotherms applied non-modified Langmuir isotherm proved to be the best fit for phenol and modified Langmuir isotherm was found to be best fit for cyanide. Phenol showed a removal percentage of 75 % by SAB process and cyanide showed a removal percentage of 83 %. The data was also non-linearly modelled for kinetic studies. Kinetic studies revealed that for both phenol and cyanide simultaneous adsorption and biodegradation took place by physisorption as well as by chemisorption. Surface diffusion is dominating for the simultaneous adsorption and biodegradation of phenol whereas in case of cyanide intraparticle diffusion is the dominating factor.

Competitive adsorption of phenol and resorcinol onto rice husk ash

The present study deals with the adsorptive removal of phenol and resorcinol from aqueous solution onto rice husk ash. The competitive adsorption equilibrium of the binary mixtures (phenol/resorcinol) was determined by conducting batch experiments with initial concentration varying in the range of 50 to 1000 mg/L. In order to evaluate multicomponent adsorption isotherm parameters, individual adsorption equilibrium studies were also carried out. Langmuir, Freundlich and Redlich-Peterson equilibrium isotherm models were used for single compound equilibrium sorption data modeling. All three models almost similar fit for single compound equilibrium data. Binary equilibrium adsorption data and the parameter evaluated from single adsorption data were fitted to various multicomponent isotherm models by minimizing the sum of square of error. The extended Langmuir model gave the better fit to the experimental adsorption data of phenol and resorcinol from binary systems onto rice husk ash. It seems that both phenol and resorcinol compete for the same adsorption sites on rice husk ash. The net interactive effect of phenol and resorcinol on the adsorption of resorcinol by rice husk ash was found to be antagonistic.

Investigation on the montmorillonite adsorption of biocidal compounds incorporating thermodynamical-based multicomponent adsorption isotherm

Sublethal concentration of biocides, namely triclosan and benzalkonium chloride, have been known to raise severe environmental problems such as pathogens resistance and the existence of the toxic compounds in reclaimed water. Simple adsorption process of those biocides onto the bentonite modified by dodecyltricetyl ammonium bromide (DTAB) cation, show a remarkable increase on the removal efficiency of triclosan, regardless of the pH value. It was found that organophilic cation facilitates the anchoring of hydrophobic triclosan, but slightly limits the adsorption of benzalkonium chloride by occupying the active cation exchange site in the bentonite structure. Adsorption of a single system can be described properly by Langmuir isotherm equation. Incorporation of the Gibb’s free energy on the affinity constant of the extended Langmuir equation may attribute robust predictive ability on the binary adsorption model.

Mass-Spectrometric Analysis during Evacuation of H2O, CH4 and D2 in Cryopump

Multi-component adsorption isotherm is determined experimentally when He, H2 (or D2) and CH4 are adsorbed on activated carbon (AC) plated on a cryopanel cooled at cryogenic temperature and desorbed at room one. It is correlated to the Langmuir-Freundlich-type one. The equilibrium isotherms for their respective single-component adsorption processes are correlated in terms of the Langmuir-Freundlich-type ones, and the isotherm when the three components of He, H2 and CH4 are adsorbed at the same time is correlated in terms of a naturally-extended multi-component one without any changes in the original constants included in the single-component one. Rates of the isotopic exchange reaction of D atom between CH4 and D2 on AC between 10 K and room temperature are also determined. After eliminating the effects of natural isotope of 13C included in CH3D, CH2D2, CHD3, CD4 on mass-spectrometric measurements, it was found that the isotopic exchange rate of CH4 + D2 = CH3D +HD and so on was found to be so late that any detectable effect was not observed.

Multicomponent adsorption of chlorhexidine gluconate in presence of a cationic surfactant: Role of electrostatic interactions and surface complexation

The modified competitive Langmuir-like model and the LeVan-Vermeulen model are applied for the adsorption of chlorhexidine gluconate and cetrimide (present in various antiseptic solutions) using Granular Activated Carbon (GAC). Parameters of each of these models are estimated using NAG E04USA subroutine, based on minimizing the sum of squares (SSQ). The GACs are physically and chemically characterized. A good fit for the Langmuir adsorption isotherm, for both the pure components, confirms the applicability of both the multicomponent adsorption isotherm models. Kinetic study, pore and film diffusion modelling are also applied. The goodness of the fits in the pseudo-second order model and the film diffusion model helps conclude that film diffusion is the rate controlling step for the adsorption of chlorhexidine gluconate and cetrimide by GAC after around 15h. The surface remaining negative beyond the pHpzc(=2.185), a pH of approximately 7–8 is maintained for all the experiments of batch adsorption. This helps in much larger adsorption of cetrimide, which exists as cetrimonium ion in the model antiseptic solution. Results demonstrate that specific chemical interactions between chlorhexidine gluconate and surface functional groups, in combination with electrostatic forces, play the major role in the adsorption mechanism.

Binary adsorption of heavy metals from aqueous solution onto natural clays

The binary adsorption of Cd(II)–Ni(II) on bentonite, Zn(II)–Cd(II) on sepiolite and Pb(II)–Cu(II) on vermiculite was investigated in this work. The experimental binary adsorption data were interpreted using the following multicomponent adsorption isotherms: non-modified, extended and modified Langmuir; non-modified and modified Redlich–Peterson; extended Freundlich; and Sheindorf–Rebuhn–Sheintuch. The modified Redlich–Peterson multicomponent isotherm best fitted the adsorption data of Cd(II)–Ni(II) on bentonite and Pb(II)–Cu(II) on vermiculite, while the modified Langmuir multicomponent isotherm best fitted the data of Zn(II)–Cd(II) on sepiolite. The competitive adsorption of Cd(II)–Ni(II) on bentonite revealed that both metals presented very similar antagonism toward the adsorption of the other metal. The single metal adsorption on sepiolite showed that the Cd(II) adsorption capacity of sepiolite was 1.3 times greater than that of Zn(II); however, in the binary adsorption, the Zn(II) presented a strong antagonism to the adsorption of Cd(II), but Cd(II) did not affected the adsorption of Zn(II). The single adsorption isotherms of Cu(II) and Pb(II) on vermiculite revealed that the affinity of the vermiculite towards Pb(II) was slightly higher than that of the Cu(II). However, in the competitive adsorption, the affinity of Pb(II) towards the vermiculite was much higher than that of the Cu(II).

Monte Carlo Simulation and Exact Statistical Mechanical Lattice Models as a Development Tool for Zeolite Multi-Component Adsorption Isotherm Derivation

Developing a suitable separation and purification procedure for multi-component gas mixtures is a ubiquitous problem. Very little is known experimentally about multi-component adsorption isotherms, yet these are crucially important for designing separation processes. Multi-component adsorption isotherms over a wide range of composition, pressure and temperature are virtually unknown. Adsorption onto zeolites is widely used in adsorptive separation processes due to the unique characteristics of its structural pores which may be engineered to permit adsorption to take place on the basis of molecular shape and size. In this article, we discuss the methodological development of rapidly obtaining multicomponent adsorption isotherms using the interplay between the essentially exact (in the statistical mechanical sense) lattice model and configurational bias Monte Carlo simulations. The latter technique has the known capability of being able to reproduce experimental isotherms reliably, but can be very time co...