Interpretation Of Adsorption Isotherms Research Articles

Interpretation of adsorption isotherm and kinetics behind fluorene degradation

The gradual release of slow-degrading polycyclic aromatic hydrocarbons into the environment creates a high level of threat to aquatic and terrestrial life worldwide. Remediation of these PAHs should be designed in such a way that it poses as few or no environmental hazards as possible. In our study, we examined the degradation ability of the synthesized MnO2 nanoparticles against fluorene. The MnO2 nanoparticle prepared was found to be spherical from the SEM analysis. XRD analysis confirms the average crystallite size as 31.8652 nm. Further, the characterization of nanoparticles was confirmed by UV-DRS, FT-IR, DLS, and HPLC techniques. The extent of adsorption potential of the synthesized nanoparticles was established from the batch adsorption studies and the kinetic and isotherm model was interpreted. The antimicrobial properties of the synthesized MnO2 nanoparticles were analyzed.

Free and Bound Water Content in Tight Rocks of Bazhenov Formation

The paper presents data on water content separated into free, physically and chemically bound types for a collection of core samples from the Bazhenov formation. The rock samples came from 3 wells of Nizhnevartovsk arch, Western Siberia, Russian Federation. Each rock sample was a part of whole core with the maximum preserved natural water content. A suite of modern laboratory techniques includes evaporation method, derivatographic, and hygrometric studies. The results show that the content of chemically bound water (0÷6.4 wt.%) exceeds that of free (0÷1.87 wt.%) and physically bound (0÷1.0 wt.%). For the first time, we present the water content of mono-, poly-, and capillary condensation water obtained from the interpretation of adsorption isotherm. These data made it possible to draw a meaningful conclusion on mixed wettability of Bazhenov formation rocks.

Modelling and Interpretation of Adsorption Isotherms

The need to design low-cost adsorbents for the detoxification of industrial effluents has been a growing concern for most environmental researchers. So modelling of experimental data from adsorption processes is a very important means of predicting the mechanisms of various adsorption systems. Therefore, this paper presents an overall review of the applications of adsorption isotherms, the use of linear regression analysis, nonlinear regression analysis, and error functions for optimum adsorption data analysis.

Adsorption isotherm of non-azeotropic solution onto porous adsorbents

Adsorption isotherm is essential component in the understanding of the adsorption process. Several methods of the measurements, analysis and interpretation of adsorption from solution have been reported in the literature. Most of the measurements of adsorption isotherm from solution were involved the measurement of excess isotherm conducted at low region of sorbates concentration. Direct interpretation of excess adsorption isotherm as adsorption isotherm is always been practice. Therefore, in this work a study on the measurement of the adsorption isotherm from solution of non-azeotropic organic solvent mixture onto porous adsorbents for whole range of liquid concentration was conducted. The study included the measurement of excess adsorption isotherm using conventional technique. Theoretical analysis and interpretation of adsorption isotherm from the excess isotherm were conducted using Pseudo Ideal Adsorption, Gibbs Dividing Plane Model and Langmuir-Fruendlich binary isotherm model. For organic solvents, acetone and propanol were chosen as the adsorbates due to the non-azeotropic properties in the mixture. Activated carbon and silicalite were chosen as adsorbents due to the different in their porosity such as macro porous and micro porous structure. The result of the study has revealed that the adsorption isotherm of non-azeotropic mixture onto activated carbon and silicalite can be interpreted as monolayer type of adsorption.

Interpretation of Adsorption Isotherm of Non Azeotropic Mixture onto Porous Adsorbents

Interpretation of Adsorption Isotherm of Non Azeotropic Mixture onto Porous Adsorbents

A non-BET adsorption and its LgBET model

Abstract The paper proposes new mathematical tools for interpretation of adsorption isotherms at relative pressures ranging to 0.95. Adsorption of small (nearly spherical) molecules in microporous adsorbents containing hole-like micropores is considered. In such materials formation of adsorbate clusters more compact than BET stacks is possible that leads to non-BET configurational effects. Additionally, geometrical and energetic constraints for the cluster size may be of significance. The paper shows that such effects can be handled with a rigorous mathematical model based on the BET approach. The derived general formulas may be useful in theoretical studies of effects of pores geometry on the adsorption isotherm shape. The neglecting of the geometrical constraints leads to a BET-like analytical formula (gBET equation). Moreover, an approximating formula is proposed (LgBET equation), taking into account the cluster size constraints represented by an exponential distribution function. The gBET and LgBET models may be used to draw semi-quantitative information on the shape of pores by the examination of adsorption isotherms at high relative pressures (ranging to 0.9). They provide also more reliable information on the adsorbent surface area and adsorption energy than the BET equation. Exemplary results of the new model application to analysis of N2 adsorption on activated carbons are discussed.

Non-ionic surfactants adsorption: structure and thermodynamics

Abstract Adsorption of non-ionic surfactants from aqueous solutions has been studied for years because of its industrial relevance. These surfactants, made of an aliphatic part attached to a hydrophilic and polar chain, play an important role in diverse applications. Modelling of the adsorption mechanisms of surfactants has traditionally been based on the interpretation of adsorption isotherms. However, this first level of investigation is not sufficient for a complete understanding. Direct inspection of the adsorbed layer of non-ionic surfactant molecules at the solid–liquid interface is needed. This is an active field of research for almost 15 years, even if the subject is not completely settled down. The aim of this paper is to present a short review of this topic. I will restrict this paper to the case of non-ionic adsorption onto hydrophilic or polar solid interfaces. In the first part, I comment some experimental studies of non-ionic adsorption layer, including fluorescence spectroscopy, neutron scattering and atomic force microscopy. In the second part, a theoretical discussion about thermodynamics of adsorption is presented. A model involving an aggregative adsorption process is proposed. This last part will permit to raise some interesting questions concerning the role of the so-called ‘normal interaction’ (surfactant/solid interaction) to select the optimal surface aggregate curvature. To cite this article: P.E. Levitz, C. R. Geoscience 334 (2002) 665–673.

Steric effects on molecular adsorption at columnar surfaces. A model for the adsorption of pyridine on gold electrodes

Results for pyridine (Py) adsorption on columnar-structured (cs) gold substrates from acid solutions at different potentials and 298 K are compared to the predictions of a recently proposed Langmuirian adsorption model at columnar surfaces. The difference in the apparent adsorption Gibbs energy derived from the adsorption isotherm of Py on cs- and smooth gold substrates was accounted for by a correction factor (f) that depends on the roughness (R) of the substrate according to f∝R−n, as expected from Monte Carlo simulation of the model. This agreement indicates that the substrate geometry plays a key role in the interpretation of adsorption isotherms.

Interfacial Adsorption of Polymers and Surfactants: Implications for the Properties of Disperse Systems of Pharmaceutical Interest

This review considers basic aspects of the interfacial adsorption of polymers and surfactants, with particular reference to the relevance of these processes for the formulation of pharmaceutical disperse systems. First, we discuss different approaches to the interpretation of adsorption isotherms, paying particular attention to systems containing more than one adsorbate. Second, we consider the implications of adsorption for the properties of suspensions, emulsions, and colloidal systems, particularly as regards the use of polymers and surfactants for stabilizing disperse systems, for controlling flocculation, and for modifying the biopharmaceutical behavior of colloidal drug carriers. Finally, we present a number of representative examples of the importance of adsorption of macromolecules in pharmaceutical systems.

The characterisation of solids by adsorption and immersion techniques and by AFM/STM

The surface of porous and non-porous solids can be characterised by a variety of techniques. Basic information is provided by the interpretation of adsorption isotherms, which can be combined with immersion calorimetry. Adsorption in micropores is described by Dubinin's theory, which applies to carbons, as well as other solids, but it appears that this theory can also be extended to non-porous solids. In this case, it takes the form of the Dubinin-Radushkevich and Kaganer (DRK) equation. For a number of systems, a good agreement is found with the BET method and the data obtained from vapour adsorption and from immersion calorimetry shows selfconsistency. The structural data derived from adsorption and immersion techniques is also compared with the direct observation of the surface by atomic force and scanning tunnelling microscopies. The relation with the fractal character D of a surface is also considered.

Packing effects in the adsorption at the liquid-solid interface

We report a study of the dense hard-sphere fluid near a wall with a square well adsorbing potential. We use Monte Carlo simulations, integral equations and density functional theory in the smoothed-density approximation to determine the structure of the fluid as a function of the wall potential. We propose a theory which relates the properties of the adsorbed layer to those of an effective 2-d fluid which takes into account the presence of the bulk liquid. Some consequences for the interpretation of adsorption isotherms at the liquid-solid interface are discussed.