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Journal ArticleDOI

Derivation and constants determination of the Freundlich and (fractal) Langmuir adsorption isotherms from kinetics

01 Mar 2018-Vol. 333, Iss: 1, pp 012010
TL;DR: In this article, an alternative way of determining the constants in both isotherm equations by kinetics approach was introduced, and the results were then compared with that obtained by the conventional method.
Abstract: The Freundlich adsorption isotherm is mostly presented as an empirical equation and the (fractal) Langmuir adsorption isotherm is derived from kinetics. However, their constants are determined by thermodynamic approach. As yet, both are used as an independent tool for determining the type of adsorption, just physical or chemical adsorption. This study aims to introduce an alternative way of driving Freundlich adsorption isotherm from kinetics, to elaborate its relation with the (fractal) Langmuir adsorption isotherm, and to determine their constants simultaneously by kinetics approach. An alternative way of determining the constants in both isotherm equations by kinetics approach was introduced. The results were then compared with that obtained by the conventional method. The study is theoretical but the validity of determination technique is based on the statistical tests on data adapted from literature. The Freundlich adsorption isotherm is introduced; the isotherm is the (fractal) Langmuir adsorption isotherm at relatively low concentration. It is irrelevant to use both adsorption isotherm separately. The new method is more reliable and its represent the reaction.
Citations
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Book ChapterDOI
20 Mar 2019
TL;DR: In this article, an analytical isotherm equation that describes the multilayer adsorption on fractal surfaces with adsorbate-adsorbate interactions (measured in terms of free energy) different from that of bulk liquid was developed.
Abstract: An analytical isotherm equation that describes the multilayer adsorption on fractal surfaces with adsorbate-adsorbate interactions (measured in terms of free energy) different from that of bulk liquid was developed. Assuming mathematical functionalities for the variation of the free energy, it is possible to evaluate the influence of the adsorbate-adsorbate interactions on the adsorption capacity of solids of high degree of surface irregularity. For those surfaces with relatively low degree of irregularity, it results that the free energy variation with the layer number in the multilayer region affects considerably the sorption capacity of the adsorbent, even for water activities lower than those corresponding to the monolayer moisture content. The energy interactions between adjacent adsorbate layers become less important as the fractal dimension of the adsorbent increases. For a fractal surface, the growing of the multilayer seems to mainly controlled by the degree of surface roughness characteristic of microporous adsorbents, where the volume and pore dimension are the true limitants to the sorption capacity. The isotherm equations obtained were tested fitting published experimental equilibrium data of various water vapor-biopolymer systems.

2 citations

Proceedings ArticleDOI
02 Jun 2020
TL;DR: In this article, the Freundlich Adsorption Isotherm (FAI) was introduced with kinetics approach, but without adequate explanation on the relationship of n with b and k with K.
Abstract: The Freundlich Adsorption Isotherm (FAI), has been introduced with kinetics approach, but without adequate explanation on the relationship of n with b and k with K. Conventionally, data is obtained by varying the weight of adsorbent with the same amount of adsorbate (or conversely) and measured at the same contact time. There is no restriction in the number of adsorbents and adsorbates used. An adsorption is confirmed as FAI or Langmuir Adsorption Isotherm (LAI) based on the regression-coefficient of its linear plot which is closer to ± 1.000. This study aims to explain relation between FAI and Differential Method (DM) and to show inconsistencies in the determination techniques and to create alternatives. The study was conducted theoretically and the validity of the new technique was tested by applying the technique to literature data. The result shows that both are interconnected. The FAI equation can be derived from the rate equation of DM. Validity test shows that the average percentage difference of n with b is 1.06 % and k with K is 2.41%.
Book ChapterDOI
24 Jan 2022
TL;DR: In this article , a finite element (FE) modeling of advection-dispersion transport of HMs by leachate movement along with Freundlich isotherm adsorption parameters is presented.
Abstract: World research results indicate that untreated leachate contains high contents of heavy metals (HM) that are likely to pollute the soil and groundwater (GW) environment and contribute to the increase of HMs in soil and GW. The Freundlich isotherm adsorption parameters are essential to soil input parameters for modelling of HMs’ transport to access the soil skeleton and soil pore water contamination by HMs. Finite element (FE) modelling of advection-dispersion transport of HMs by GW movement along with Freundlich isotherm adsorption parameters which continuously change with space in the model domain and with time is sophisticated to accurately evaluate the HMs’ concentrations in soil skeleton and pore water. The chapter describes the background of the existing isotherm adsorption theory, the adaptation of the Freundlich isotherm adsorption in the soil skeleton and soil pore water contamination by HMs, method of determination of the Freundlich isotherm adsorption parameters, the FE procedure of modelling of advection-dispersion transport of HMs by GW movement in general and along with Freundlich isotherm adsorption parameters in particular. A case study modelling has been demonstrated.
Journal ArticleDOI
01 Jun 2020
TL;DR: In this paper, the authors provide a theoretical basis for the use of the isolation method in conjunction with Langmuir Adsorption Isotherm (LAI) for FAI fitting-constant determination and provide suggestions for data analysis techniques.
Abstract: Determination of Freundlich Adsorption Isotherm (FAI) fitting-constant is mostly carried out using different amounts of adsorbent with fixed amount of adsorbates, calculated for 1 g or 1 mgr, and measured at the same contact time. This technique is used together with Langmuir Adsorption Isotherm (LAI). It is considered empirical but, kinetically, it is similar to the Isolation Method (IM). The purpose of this study is to provide a theoretical basis for the use of the IM approach in conjunction with LAI based for FAI fitting-constant determination and provide suggestions for data analysis techniques. The study was carried out theoretically, while the validity test was carried out by applying the findings to the literature data which were supplemented by statistical tests. The results show that the present technique is somewhat dubious. The technique is not suitable for every adsorbent-adsorbate pair (violating the basic assumptions of the LAI kinetics aspect) and the non-linear analysis technique give an order-reaction that is not always consistent with the adsorption condition. A new technique has been introduced. This new technique gives a value of b = n (Percentage Difference, PD, is less than 5%).
References
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Book
02 Nov 1995
TL;DR: In this article, an overview of the evolution of Soil Chemistry is presented, with a case study of Pollution of Soils and Waters and a discussion of the role of organic compounds in soil chemistry.
Abstract: Environmental Soil Chemistry: An Overview: Evolution of Soil Chemistry. The Modern Environmental Movement. Contaminants in Waters and Soils. Case Study of Pollution of Soils and Waters. Soil Decontamination. Inorganic Soil Components: Pauling's Rules. Primary Soil Minerals. Secondary Soil Minerals. Specific Surface of Soil Minerals. Surface Charge of Soil Minerals. Identification of Minerals by X-Ray Diffraction Analyses. Use of Clay Minerals to Retain Organic Contaminants. Chemistry of Soil Organic Matter: Effects of Soil Formation Factors on SOM Contents. Composition of SOM. Fractionation of SOM. SOM Structure. Functional Groups and Charge Characteristics. Humic Substance-Metal Interactions. SOM-Clay Complexes. Retention of Pesticides and Other Organic Substances by Humic Substances. Soil Solution-Solid Phase Equilibria: Measurement of the Soil Solution. Speciation of the Soil Solution. Ion Activity and Activity Coefficients. Dissolution and Solubility Processes. Sorption Phenomena on Soils: Introduction and Terminology. Surface Functional Groups. Surface Complexes. Adsorption Isotherms. Equilibrium-Based Adsorption Models. Surface Precipitation. Sorption of Metal Cations. Sorption of Anions. Points of Zero Charge. Desorption. Use of Spectroscopic and Microscopic Methods in Determining Mechanisms for Sorption-Desorption Phenomena. Ion Exchange Processes: Characteristics of Ion Exchange. Cation Exchange Equilibrium Constants and Selectivity Coefficients. Thermodynamics of Ion Exchange. Relationship between Thermodynamics and Kinetics of Ion Exchange. Kinetics of Soil Chemical Processes: Rate-Limiting Steps and Time Scales of Soil Chemical Reactions. Rate Laws. Determination of Reacti

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01 Jul 2019

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01 Jan 1978
TL;DR: In this article, the basic concepts from general chemistry for environmental engineering are presented, as well as fundamental concepts from physical chemistry and equilibrium chemistry for the analysis of wastewater and wastewater in the field of environmental engineering.
Abstract: Part 1 Fundamentals of chemistry for environmental engineering: basic concepts from general chemistry basic concepts from physical chemistry basic concepts from equilibrium chemistry basic concepts from organic chemistry biochemistry colloid chemistry nuclear chemistry Part 2 Wastewater and wastewater analysis: basic concepts form quantitative analysis instrumental methods of analysis turbidity colour standard solutions pH acidity alkalinity hardness disinfection chlorides dissolved oxygen biochemical oxygen demand chemical oxygen demand nitrogen residue iron and magnganese flouride sulfate phosphorous and phosphate grease volatile acids volatile organics trace inorganics

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Book
27 Aug 2002
TL;DR: In this article, the authors focused on the aspects of chemistry that are particularly valuable for solving environmental problems, and laid the groundwork for understanding water and wastewater analysis-a fundamental basis of environmental engineering practice and research.
Abstract: This is the definitive text in a market consisting of senior and graduate environmental engineering students who are taking a chemistry course The text is divided into a chemistry fundamentals section and an applications section In this new edition, the authors have retained the thorough, yet concise, coverage of basic chemical principles from general, physical, equilibrium, organic, biochemistry, colloid, and nuclear chemistry In addition, the authors have retained their classic two-fold approach of (1) focusing on the aspects of chemistry that are particularly valuable for solving environmental problems, and (2) laying the groundwork for understanding water and wastewater analysis-a fundamental basis of environmental engineering practice and research

741 citations