Shape Of Adsorption Isotherms Research Articles

Aspects of Gas Storage: Confined Geometry Effects on the High-Pressure Adsorption Behavior of Supercritical Fluids.

During the last decades, major progress was made concerning the understanding of subcritical low-pressure adsorption of fluids like nitrogen and argon at their boiling temperatures in nanoporous materials. It was possible to understand how structural properties affect the shape of the adsorption isotherms. However, within the context of gas storage applications, supercritical high-pressure gas adsorption is important. A key feature here is that the experimentally determined surface excess adsorption isotherm may exhibit a characteristic maximum at a certain pressure. For a given temperature and adsorptive/adsorbent system, the surface excess maximum (and the corresponding adsorbed amount) is related to the storage capacity of the adsorbent. However, there is still a lack of understanding of how key textural properties such as surface area and pore size affect details of the shape of supercritical high-pressure adsorption isotherms. To address these open questions, we have performed a systematic experimental study assessing the effect of pore size/structure on the supercritical adsorption isotherms of pure fluids such as C2H4, CO2, and SF6 over a wider range of temperatures and pressures on a series of model materials exhibiting well-defined pore sizes, i.e., ordered micro- and mesoporous materials (e.g., NaY zeolite, KIT-6 silica, and MCM-48 silica). A fundamental result of our experiments is a unique fluid-independent correlation between the pressure of the surface excess maximum pmax (at a given temperature) and the pore size (by taking into account the kinetic diameter of the fluid and the underlying effective attractive fluid-wall interaction). Summarizing, our results suggest important structure-property relationships, allowing one to determine, for given thermodynamic conditions, important information related to the optimal operating conditions for supercritical adsorption applications. The insights may also serve as a basis for optimizing and tailoring the properties of nanoporous adsorbent materials for gas storage applications.

An adsorption isotherm identification method based on CNN-LSTM neural network.

The morphology of adsorption isotherms embodies a wealth of information regarding various adsorption mechanisms, rendering the classification and identification methodologies predicated on the shape of adsorption isotherms indispensably crucial. While research on classification techniques has been extensively developed, traditional methods of adsorption isotherm identification grapple with inefficiencies and a high margin of error. Neural network-based methodologies for adsorption isotherm identification serve as a countermeasure to these shortcomings, as they facilitate swift online identification while delivering precise results. In this paper, we deploy a hybrid of convolutional neural networks (CNN) and long short-term memory (LSTM) networks for the identification of adsorption isotherms. Extensive theoretical adsorption isotherms are generated via adsorption equations, forming a comprehensive training database, thereby circumventing the need for time-consuming and costly repetitive experiments. The F1-score, receiver operating characteristic (ROC) curves, and area under the ROC curve (AUC) are introduced as criteria to evaluate the identification performance and generalization ability of the model during the testing phase. The results highlight the model's superlative performance in the task of adsorption isotherm identification, with accuracy rates of 100% in both the training and validation sets. The mean F1-score obtained from the testing set reached 0.8885, with both macro-average and micro-average AUC exceeding 0.95. PyCharm was employed as an experimental and testing platform, with Python 3.9 serving as the programming language. TensorFlow 2.11.0 and Keras 2.10.0 were harnessed for the training and testing of CNN-LSTM, while numpy 1.21.5 and scipy 1.81 were utilized for the creation of training and validation datasets.

Theoretical evaluation of adsorption desalination performance of metal-organic frameworks under varying scenarios

• Adsorption desalination performance of 12 adsorbents was evaluated. • MOFs outperform other adsorbents owing to their higher water transfer amount. • Desalination performance of adsorbents is correlated with adsorption characteristics. • DUT-67 is the most potential candidate under varying operation conditions. Adsorption desalination systems (ADs) driven by low-grade energy are regarded as sustainable alternatives to address water shortages due to their low energy consumption. Adsorbents is the key materials for the performance of ADs. In this work, a numerical study was performed to assess the water production performance of ADs based on metal–organic frameworks (MOFs) and other adsorbents under different working conditions. It is found that the trends in specific daily water production (SDWP) and performance ratio (PR) with hot and chilled water temperature are closely correlated with the adsorption characteristics, i.e., water uptake and the shape of adsorption isotherms. Moreover, considering both SDWP and PR, MOFs outperform other adsorbents owing to their high water transfer amount per cycle under various conditions. Among 12 adsorbents, DUT-67, Al-fumarate and MIL-100(Fe) are the top performers at chilled water temperature of 10 °C, 20 °C and 30 °C respectively with average SDWP (PR) of 3.31 m 3 /ton/day (0.33), 8.05 m 3 /ton/day (0.56) and 13.46 m 3 /ton/day (0.71), increased by 43.8% (32.0%), 65.3% (40%), and 102.7% (44%) compared to traditional silica gel. This work provides helpful insights into the correlation between desalination performance and water adsorption characteristics of adsorbents under varying working conditions, which favors choosing and designing of potential adsorbents for ADs.

Feasibility Study of Vacuum Pressure Swing Adsorption for CO2 Capture From an SMR Hydrogen Plant: Comparison Between Synthesis Gas Capture and Tail Gas Capture

In this paper, a feasibility study was carried out to evaluate cyclic adsorption processes for capturing CO2 from either shifted synthesis gas or H2 PSA tail gas of an industrial-scale SMR-based hydrogen plant. It is expected that hydrogen is to be widely used in place of natural gas in various industrial sectors where electrification would be rather challenging. A SMR-based hydrogen plant is currently dominant in the market, as it can produce hydrogen at scale in the most economical way. Its CO2 emission must be curtailed significantly by its integration with CCUS. Two Vacuum Pressure Swing Adsorption (VPSA) systems including a rinse step were designed to capture CO2 from an industrial-scale SMR-based hydrogen plant: one for the shifted synthesis gas and the other for the H2 PSA tail gas. Given the shapes of adsorption isotherms, zeolite 13X and activated carbon were selected for tail gas and syngas capture options, respectively. A simple Equilibrium Theory model developed for the limiting case of complete regeneration was taken to analyse the VPSA systems in this feasibility study. The process performances were compared to each other with respect to product recovery, bed productivity and power consumption. It was found that CO2 could be captured more cost-effectively from the syngas than the tail gas, unless the desorption pressure was too low. The energy consumption of the VPSA was comparable to those of the conventional MDEA processes.

Water adsorption isotherms on soil external particle surface by molecular simulation

Water adsorption isotherm describes soils’ ability in retaining water under given relative humidity and isothermal conditions, and is frequently utilized to characterize soils’ engineering properties. Fundamentally, the water adsorption isotherm on soil external particle surface is the macroscopic manifestation of atomistic scale soil–water interaction mechanisms, including van der Waals, surface hydration, cation hydration, and electrical double layer. Yet, the quantitative link between these mechanisms and water adsorption isotherms remains obscure, and it still lacks effective approaches to probe these mechanisms. Here, a general framework based on Grand Canonical Monte Carlo simulation was developed to directly obtain water adsorption isotherms on soil external particle surface from the interatomic potentials. The simulated adsorption isotherm agrees well with existing experimental and numerical results, confirming the validity of the proposed framework. The proposed framework facilitates a quantitative assessment of the impact of atomistic scale soil–water interaction mechanisms on the macroscale water adsorption isotherms. It reveals that the atomistic scale soil–water interaction mechanisms dictate the shape of adsorption isotherms, i.e., an ‘S’ shape by prevailing cation hydration and a concave shape by prevailing surface hydroxyl hydration; and divalent cations exhibit a much more intensive interaction with water molecules than univalent cations, increasing the adsorption capacity up to 9.5 times.

Adsorption scaling theory for investigation of distance between clay-layers with adsorbed polymer and adsorption-isotherm versus polymer-concentration: Comparison to experiment

The purpose of this paper is to introduce an adsorption scaling theory for explaining the experimental results dealt with the clay-polymer hybrids. The main problem to apprehend is the evolution of two interesting physical quantities which are the equilibrium adsorbed quantity (adsorption-isotherm), Qeq, and the clay-layer-spacing, d001 upon the initial bulk-polymer-density, Cd. In the present investigation, we are concerned with the case where the polymers are highly attracted by the clay-layers (strong adsorption). For such an attractive case, the adsorption-isotherm shape and scenario of the interlaminar-space are explained using an elaborated adsorption scaling theory, and we show the existence of distinct regimes depending on the value of the initial bulk-polymer-density with water as host liquid. Within each density-regime, we give explicit expressions for the quantities QeqCd and d001Cd. On the other hand, the present adsorption scaling theory was tested and compared with two practical cases concerning bentonite-polygycols (PEGs) and montmorillonite-polycarboxylate ethers (PCEs) hybrids. For the two systems, the interlayer-distance was measured as a function of the polymer-amount based on X-ray Diffraction (XRD) analysis. We find that, quantitatively, these experiments are in good agreement with the adsorption scaling theory. Also, it is noted that such a theory is more general and powerful than the classical Langmuir adsorption theory. Finally, we state that the present theory can be applied to any polymer–clay hybrid, independently on its chemical and physical details.

Adsorption of Organic Dyes on Magnetic Iron Oxide Nanoparticles. Part I: Mechanisms and Adsorption-Induced Nanoparticle Agglomeration.

This series of two papers is devoted to the effect of organic dye (methylene blue, MB; or methyl orange, MO) adsorption on the surface of either bare or citrate-coated magnetic iron oxide nanoparticles (IONPs) on their primary agglomeration (in the absence of an applied magnetic field) and secondary field-induced agglomeration. The present paper (Part I) is focused on physicochemical mechanisms of dye adsorption and adsorption-induced primary agglomeration of IONPs. Dye adsorption to oppositely charged IONPs is found to be mostly promoted by electrostatic interactions and is very sensitive to pH and ionic strength variations. The shape of adsorption isotherms is correctly reproduced by the Langmuir law. For the particular MB/citrated IONP pair, the maximum surface density of adsorbed MB seems to correspond to the packing density of an adsorbed monolayer rather than to the surface density of the available adsorption sites. MB is shown to form H-aggregates on the surface of citrate-coated IONPs. The effective electric charge on the IONP surface remains nearly constant in a broad range of surface coverages by MB due to the combined action of counterion exchange and counterion condensation. Primary agglomeration of IONPs (revealed by an exponential increase of hydrodynamic size with surface coverage by MB) probably comes from correlation attractions or π-stacking aromatic interactions between adsorbed MB molecules or H-aggregates. From the application perspective, the maximum adsorption capacity is 139 ± 4 mg/g for the MB/citrated IONP pair (pH = 4–11) and 257 ± 16 mg/g for the MO/bare IONP pair (pH ∼ 4). Citrated IONPs have shown a good potential for their reusability in water treatment, with the adsorption efficiency remaining about 99% after nine adsorption/desorption cycles.

ADSORPTION OF ETHOXYLATED ISONONYLPHENOLS ON CARBON NANOTUBES FROM AQUEOUS SOLUTIONS

One of the approaches to solving the problem of carbon nanotubes dispersions obtaining is the use of nonionic surfactants in the processes of ultrasonication of carbon nanostructures in aqueous solutions. The effect of nonionic surfactants on dispersing and stabilizing is determined by the adsorption interaction of surfactant molecules with a graphene surface, the study of which can reveal important patterns of stable carbon nanotubes dispersions obtaining during ultrasonic treatment in liquid media. The aim of this work was to study the adsorption of ethoxylated isononylphenols with a variable average degree of ethoxylation on single-walled and multi-walled carbon nanotubes from aqueous solutions. The value of adsorption of nonionic surfactants on carbon nanotubes was calculated on the basis of changes in the equilibrium concentration of ethoxylated isononylphenols in the solution at presence of carbon nanotubes. The equilibrium concentration of nonionic surfactants was determined by absorption spectroscopy. It was found that the shape of adsorption isotherms of the ethoxylated isononylphenols on carbon nanotubes from aqueous solutions before ultrasonic treatment corresponds to the Langmuir adsorption isotherm L2. The values of maximum adsorption of ethoxylated isononylphenols were shown to decrease with an increase in the average degree of ethoxylation. Obviously, this is due to conformational changes in the polar chain, showed in the sizes of ethoxylated isononylphenols micelles, in the structure of the adsorption layer. It has been established that the hydrophobic interaction of the surfactants hydrocarbon radical with a graphene surface is the main mechanism for the adsorption of ethoxylated isononylphenols on carbon nanotubes. The dispersions of carbon nanotubes in micellar solutions of nonionic surfactants were obtained and studied. It was shown that ultrasonic treatment leads to a change in the mechanism of nonionic surfactants adsorption on carbon nanotubes.

Hiding extra-framework cations in zeolites L and Y by internal ion exchange and its effect on CO2 adsorption

La-exchange of zeolites by combined aqueous and solid-state cation exchange enables control of their CO2 adsorption isotherm shape.

Synthesis of micro-mesoporous glass-analcime composite structure with soda–lime–silica glass as raw material

The micro-mesoporous composite phase structure of the analcime and the glass phase was successfully synthesized at 200∘C by using hydrothermal method, in which the soda–lime–silica glass was used as the silica source and the sodium hydroxide and aluminum oxide were used as additive. The TEM and SEM results showed that the obtained rod-shaped analcime was growing on the surface of glass particles. Thermogravimetric analysis indicated that they are stable and the adsorption isotherm shape indicated the coexistence of micropores and mesopores.

Decoding gas-solid interaction effects on adsorption isotherm shape: II. Polar adsorptives

A unique set of 6 polar adsorptives of relatively large dipole moment and of increasing kinetic diameter were used to probe pore volumes available and their mechanism of adsorption on a well-characterised microporous carbon. Multiple adsorption isotherm measurements were made and repeatable results with relatively small standard deviations in amount adsorbed at low relative pressures were obtained. Inconsistencies were observed between calculated Gurvitsch volumes. Sources of these were analysed and identified as contributions from one or more of: (a) molecular sieve effects; (b) molecular packing effects, and; (c) 2D molecular structure formation due to hydrogen bonding. These inconsistencies were further studied by comparison with pore volumes derived via the Dubinin-Radushkevich (DR) equation. Qualitative analyses of the micropore filling processes were proposed, and substantiated by complementary DR analyses. Although most of the isotherms showed Type I character, recasting the relative pressure axis in logarithmic format highlighted clear differences as contributions from fluid-fluid and fluid-solid interactions during pore filling. Overall, the adsorptives were classified into three groups: (a) polar adsorptives with primarily specific interactions adsorbing as a condensation process over a relatively narrow relative pressure range in a medium and late pressure range (iso-PrOH, MeOH, 2-methyl, 2-butanol, H2O); (b) polar adsorptives with potential for non-specific interactions adsorbing as a condensation process over a relatively narrow pressure range in a medium pressure range (pyridine, iso-PrOH, 2-methyl, 2-butanol); and, (c) halogenated adsorptives adsorbing with an S-shaped uptake extending over a broad relative pressure (dichloromethane).

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'.

Decoding gas-solid interaction effects on adsorption isotherm shape: I. Non-polar adsorptives

A suite of non-polar adsorptives of different kinetic diameters and shape were used to determine adsorption and pore filling mechanism of a well-characterised poly(furfuryl alcohol)-based activated carbon. Triplicate measured Type I adsorption isotherms for each adsorptive were averaged to provide standard deviation in relative pressures and associated amounts adsorbed. Plateau amounts adsorbed for N2, Ar, CH4, and C6H6, provided Gurvitsch volumes averaged to 0.368 ± 0.015 cm3(liq)/g. The calculated Gurvitsch volumes were compared with those derived via the Dubinin-Radushkevich (DR) equation. Additional adsorptives were CO2, iso-butane and SF6. The results of these 7 adsorptives were used to qualitatively analyse and decode a micropore filling adsorption mechanism. The DR equation was also used for further analysis of the pore filling mechanism. Based on the adsorbate-adsorbate and adsorbate-adsorbent interactions, adsorbates were classified into three groups: (a) Non-polar with non-specific interactions (no dipole, no quadrupole, not readily polarizable: Ar, N2, CH4 and iso-butane), adsorbing as a continuous uptake over the observed relative pressure range; (b) Non-polar adsorptives with potential for specific interactions (no dipole, quadrupole moment: CO2 and C6H6), adsorbing as a condensation process over a relatively narrow relative pressure range in a medium pressure range; (c) Halogenated adsorptives (no dipole, no quadrupole, polarizable: SF6), adsorbing with an S-shaped uptake extending over a relatively broad relative pressure range.

Applying the wave theory to fixed-bed dynamics of Metal-Organic Frameworks exhibiting stepped adsorption isotherms: Water/ethanol separation on ZIF-8

Zeolitic Imidazolate Framework-8 (ZIF-8) is a promising material for the energy-efficient recovery of bio-alcohols from aqueous mixtures. Its adsorption isotherms have inflection points and breakthrough curves obtained in dynamic column separation experiments exhibit stepped profiles. With the aim to optimize this adsorptive alcohol recovery process using ZIF-8, the correlation between the shape of the adsorption isotherms and the breakthrough curves was further explored in this work by means of liquid phase batch measurements and breakthrough experiments, with diluted ethanol/water mixtures. The shape of the concentration profiles, in adsorption mode as well in desorption mode, have been carefully analyzed making use of simple theoretical tools, including an axial dispersion model and a wave theory based approach. It was shown that, as a direct expression of the adsorption isotherm and the feed concentration, the concentration profiles were composed of different “shock waves” and “dispersive waves” propagating at different velocities along the column length. The description of the breakthrough and desorption curves in terms of propagation velocities enabled to gain insights into the fundamental role of the adsorption isotherm into the characteristics and the formation of the concentration profiles. The concept of “fractional used bed capacity” (FUBC) was introduced to illustrate the effect of the adsorption isotherm shape on the dynamic capacity at breakthrough point. According to the shape of the adsorption isotherm, efficient desorption could be achieved with the ZIF-8 material. This work provides, with limited computational effort, new perspectives for the further development and optimization of adsorptive separation processes with MOF materials, such as the recovery of bio-alcohols from aqueous mixtures with the ZIF-8 adsorbent.

Availability and interconnectivity of pores in mesostructured ZSM-5 zeolites by the adsorption and diffusion of mesitylene

Probing the mesopore architecture in mesoporous zeolites is of importance for large scale applications of the materials. In this work, the adsorption and diffusion of mesitylene with larger molecule size in mesoporous ZSM-5 zeolites were carried out, in order to acquaint the availability and interconnectivity of mesopores in zeolite crystals. The comparisons of the shape of adsorption isotherms and the mesopore volume calculated from mesitylene and N2 adsorption in mesoporous ZSM-5 zeolites with different mesoporosities can be used to discriminate two cases of mesopores: accessible mesopores connected to external surface of the zeolite crystals and non-accessible meso-voids that are occluded in the microporous matrix. Furthermore, the effective diffusivity and activation energy of mesitylene in mesoporous ZSM-5 extracted from ZLC desorption curves as a function of mesopore volume calculated from mesitylene adsorption reveal the enhancement of mesopore interconnectivity to molecule diffusion in zeolite crystals.

Surface-Energetic Heterogeneity of Nanoporous Solids for CO2 and CO Adsorption: The Key to an Adsorption Capacity and Selectivity at Low Pressures.

This study has been focused on surface energetic heterogeneity of zeolite (H-mordenite, "HM"), activated carbon ("RB2") and metal-organic framework family ("Z1200") materials and their isotherm features in adsorption of CO2 and CO at 25 degrees C and low pressures ≤ 850 Torr. The nanoporous solids showed not only distinctive shape of adsorption isotherms for CO2 with relatively high polarizability and quadrupole moment but also different capacities in the CO2 adsorption. These differences between the adsorbents could be well correlated with their surface nonuniformity. The most heterogeneous surfaces were found with the HM that gave the highest CO2 uptake at all pressures allowed, while the Z1200 consisted of completely homogeneous surfaces and even CO2 adsorption linearly increased with pressure. An intermediate character was indicated on the surface of RB2 and thus this sorbent possessed isotherm features between the HM and Z1200 in CO2 adsorption. Such different surface energetics was fairly consistent with changes in CO2/CO selectivity on the nanoporous adsorbents up to equilibrated pressures near 850 Torr.

The Effects of Concentrations of Zirconium(IV) Sulphate and Sulphuric Acid on Sorption of Zirconium(IV) and Hafnium(IV) on Purolite S-957 Resin. Adsorption Isotherms of Zirconium(IV) and Hafnium(IV) Ions

The optimal conditions of separation of zirconium(IV) from hafnium(IV) on Purolite S-957 ion-exchange resin in their sulfate aqueous solutions using a static method has been determined to be 0,07 M Zr(SO4)2 (containing 2% Hf) in 0,5 M H2SO4. Higher Zr(IV) concentration causes a lowering of the Zr/Hf separation efficiency due to the oligocondensation of mononuclear Zr(IV) and Hf(IV) ions resulting in the formation of Zr(IV) or mixed Zr(IV)-Hf(IV) oligohydroxo-sulfato ions, which is not prevented by the parallel increase of acidity of the solution. The same effect can be observed when analyzing the shapes of adsorption isotherms, which are similar for both Zr(IV) and Hf(IV).

Structural, textural and adsorption characteristics of bentonite-based composite

An application of coatings composed of mixed (hydr)oxides over bentonite particles in aqueous suspension, in narrow range of pH, has been proven as a useful method for obtaining bentonite based composite with a developed, specific surface area and pronounced adsorption features toward cationic pollutants. This paper deals with detailed characterization of structure as well as textural and adsorption properties of bentonite based composite. The structure of the composite was examined by using XRD technique providing results that confirm changes in orientation of layered quasi-crystalline particles of montmorillonite, which is the most common component of bentonite clay. Surface area and pore volumes were determined by N2 adsorption at −196°C using BET, t-plot, αs-plot, Dubinin Radushkevich and Dollimore–Heal method. The results have revealed that the specific surface area for composite is about two times higher than for starting bentonite. Moreover, modification of bentonite leads to significant changes in the meso- and microporosity. Adsorption properties of the composite were studied by analyzing the adsorption of dye methylene blue which was used in this study as a model of cationic pollutant in water. The most prominent role in the mechanism of dye molecules retention on the surface, interlayers and in the pores of the adsorbent is ascribed to establishing of electrostatic, van der Waals and hydrogen bonds. The shape of adsorption isotherm indicates that methylene blue can be adsorbed onto composite in more than one layer.

Adsorption of polyethyleneimine (PEI) on hematite. Influence of magnetic field on adsorption of PEI on hematite

A research on influence of magnetic field of various inductions on adsorption of polyethyleneimine (PEI) onto hematite is presented. Properties of the adsorbent surface (Magnetic Force Microscopy images and nitrogen adsorption data) and its behaviour in a water solution (particle size distribution) are also studied. Moreover, new analytical approach is proposed to compare the shape of the isotherms (e.g. presence of plateaus) by calculating a reciprocal derivative.A proposal of adsorption mechanism that explains a multilayer character of the adsorption itself as well as shapes of adsorption isotherms is presented. Changes in the before-mentioned mechanism due to exposure to magnetic field are also explained. Study revealed that in most cases presence of magnetic field decreases an amount of PEI adsorbed and this decrease is not a linear function of magnetic field strength – the tendency is reversed for the strongest field investigated (what is consistent with literature data).

Partial pyrolysis of olive wood to improve its sorption of chlorophenols and nitrophenols

Partial pyrolysis alters the chemical and textural properties of the lignocellulosic material. This work reports the effect of partial pyrolysis of olive wood on adsorption isotherms, kinetics and thermodynamics of chloro and nitrophenols. Shape of adsorption isotherms of the partially pyrolyzed sorbents was L3 for phenol; L2 for 2-nitrophenol and 2,4-dinitrophenol; H3 for 2-chlorophenol, 3-chlorophenol and 4-nitrophenol; and H2 for 4-chlorophenol. The pyrolyzed olive wood sorbents obeyed Langmuir and Freundlich models. Pyrolysis raised adsorption capacity, favorability and spontaneity; the adsorption became more exothermic; the randomness decreased. The adsorption was mainly physical; it occurred first by film diffusion then by pore-filling. Adsorption followed second-order rate kinetics. Adsorption of phenols on olive wood seemed to be governed by hydrophobic interaction. Washing the pyrolyzed olive wood with ethanol caused a decrease in adsorption capacity, favorability and spontaneity, and the adsorption became less exothermic. This indicated that pyrolysis produced species on the olive wood surface that played a significant role in phenols adsorption.