Relationship between Commonly Used Adsorption Isotherm Equations Impedes Isotherm Selection

Dorkó, Zsanett; Szakolczai, Anett; Tóth, Blanka; Horvai, George

doi:10.3311/ppch.10103

Cited by 8 publications

(4 citation statements)

References 21 publications

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“…The estimated values of b are less than a unit, and about the same (0.30−0.32 L mg −1 ) for both particle mass. It can be found in the literature that the adsorption equilibrium of cationic dyes-such as methylene blue-follows the Langmuir isotherm [16,18,25,31,34,36]. Similar results were reported for the adsorption isotherms of various pollutants onto different adsorbent types [21,37].…”

Section: Discussionsupporting

confidence: 78%

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Methylene Blue Adsorption Study on Microcline Particles in the Function of Particle Size Range and Temperature

2019

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In this paper, the adsorption process of methylene blue has been investigated on microcline particles as a function of particle size and temperature. The characterization of microcline in the particle size ranges of 1−71 μm and 71−315 μm gained by sieving was proved using X-ray diffraction (XRD) and scanning electron microscopy combined with energy-dispersive detector (SEM-EDS) in powder form, over laser diffraction measurements in aqueous suspension. The optimum dosage of adsorbent was 13.5 g/L in dye adsorption and the adsorption isotherms on both microcline size fractions were determined at this adsorbent concentration. The maximum adsorption capacities were in the range of 1.5–3.1 mg g−1 on microcline particles with supplementing evaluation of isotherms using the Langmuir model. Considering the problems of linearization of equations, the non-linear least-squares estimation can be strongly recommended for modeling adsorption-equilibrium. The adsorption isotherm determined at elevated temperature of 60−65 °C represents a breakpoint at around 20 mg L−1 of equilibrated dye concentration due to performing of a potential process of dye self-association. According to our experiments, the increase in temperature has an adverse effect on adsorption.

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Section: Discussionsupporting

confidence: 78%

“…The Langmuir isotherm is valid for monolayer adsorption onto a surface with a finite number of identical sites [32][33][34]. It is given as an equation:…”

Section: Discussionmentioning

confidence: 99%

Methylene Blue Adsorption Study on Microcline Particles in the Function of Particle Size Range and Temperature

2019

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“…Experimental support for these ideas comes mainly from isotherm measurements which are interpreted by mathematical decomposition into Langmuir sites. The isotherm measurements need to be extremely accurate and precise if useful data are to be extracted from them about the assumed, but unproved, Langmuirian binding sites [49]. Most of the published isotherm data are, however, of a lower precision than would be optimal [49].…”

Section: Discussionmentioning

confidence: 99%

New Methods to Study the Behavior of Molecularly Imprinted Polymers in Aprotic Solvents

et al. 2018

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This work presents three new experimental methods for studying molecular imprinting. The electric conductivity measurements of the pre-polymerization mixture of amine templates in an aprotic solvent provide evidence of ionic dissociation of the pre-polymerization complexes. The displacement measurement of the template propranolol from its molecularly imprinted polymer (MIP) using a quaternary ammonium ion in toluene, shows that this MIP behaves as an ion exchanger even in a non-polar solvent. The same experiment also shows that template binding to the MIP from toluene involves ionic interaction. The third experimental method introduced here serves to study the models of template binding on MIPs. To this end the binding isotherm of propranolol (PR) has been measured on a polymer mixture consisting of non-imprinted control polymer (NIP) and a stronger binding acidic polymer, respectively. All three methods are suitable for studying several other imprinting systems.

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“…An alternative possibility for evaluating adsorption isotherms consists of fitting some isotherm equation to the measured data, and comparing the constants of the equations between different adsorbed compounds or between different polymers. We have demonstrated recently that the necessary conditions for the accurate determination and for the correct interpretation of these constants are rarely satisfied by isotherm measurements on MIPs [ 27 ]. The selectivity ladder method presented here requires much less and also less demanding experimentation.…”

Section: Theorymentioning

confidence: 99%

The Selectivity of Polymers Imprinted with Amines

et al. 2018

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One of the main reasons for making molecularly imprinted polymers (MIPs) has been that MIPs interact selectively with a specific target compound. This claim is investigated here with the example of a widely used type of noncovalent MIP, the MIP for the beta blocker propranolol. Adsorption isotherms of this MIP and of a nonimprinted control polymer (NIP), respectively, have been measured with a series of compounds in the porogen solvent acetonitrile. The results, visualized as “selectivity ladders”, show that the MIP binds propranolol and many other amines better than the NIP does, but the selectivity of the MIP is actually inferior to that of the NIP. The selectivity of either polymer for propranolol is modest against many amines, but is remarkable with respect to other compounds. The contribution of imprinting towards selectivity can be better appreciated when three MIPs, made with different amine templates, are compared among themselves. Each MIP is seen to bind its own template slightly better than the other two MIPs do. In media different from the porogen, the selectivity patterns may change substantially. Propranolol seems to have properties that make it stand high on the selectivity scale in different solvents, albeit for different reasons.

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Relationship between Commonly Used Adsorption Isotherm Equations Impedes Isotherm Selection

Abstract: Abstract

Cited by 8 publications

References 21 publications

Methylene Blue Adsorption Study on Microcline Particles in the Function of Particle Size Range and Temperature

Methylene Blue Adsorption Study on Microcline Particles in the Function of Particle Size Range and Temperature

New Methods to Study the Behavior of Molecularly Imprinted Polymers in Aprotic Solvents

The Selectivity of Polymers Imprinted with Amines

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