Check out our New Publishers' Select for Free Articles

Adsorption: Journal of the International Adsorption Society (v.16, #4-5)

Professor Andrzej Waksmundzki (1910–1998) by Marek Kosmulski; Jolanta Narkiewicz-Michalek; Marek Pawlik (pp. 183-184).

Evidences for the relationship between surface structure and reactivity of goethite nanoparticles based on advanced molecular-probe methods by Stéphane Stevanovic; Mouhamad AliAhmad; Angelina Razafitianamaharavo; Frédéric Villiéras; Barrès Odile; Bénédicte Prélot; Jerzy Zajac; Jean-Marc Douillard; Corinne Chanéac (pp. 185-195).

Surface properties of two goethites have been studied in order to compare the amount of acid surface sites and their distribution over the various surface domains. For this purpose, ammonia, pyridine and nitrogen were used as basic molecular probes. Calorimetry measurements of ammonia adsorption provided the image of the average surface acidity being moderate. This conclusion was supported by the moderate resistance of the adsorbed pyridine molecules to degassing conditions. Adsorption and desorption of pyridine prior to gaseous nitrogen adsorption resulting in masking/unmasking of acid surface sites on the goethite surface allowed confirmation of the acid character of the specific adsorption sites characterized by the high-energy adsorption of electron-donating molecular nitrogen. The amount of acid sites probed by nitrogen and ammonia were of the same order of magnitude but systematically higher for ammonia. The subsequent analysis of the argon and nitrogen derivatives of first-layer adsorption isotherm led to determine the distribution of {101} and {121} crystallographic faces and discuss the location of acid sites on these surface domains.

Keywords: Goethites; Ammonia; Pyridine; Nitrogen adsorption; Acid sites

Simple model of adsorption on external surface of carbon nanotubes—a new analytical approach basing on molecular simulation data by Sylwester Furmaniak; Artur P. Terzyk; Piotr A. Gauden; Peter J. F. Harris; Marek Wiśniewski; Piotr Kowalczyk (pp. 197-213).

Nitrogen adsorption on carbon nanotubes is wide- ly studied because nitrogen adsorption isotherm measurement is a standard method applied for porosity characterization. A further reason is that carbon nanotubes are potential adsorbents for separation of nitrogen from oxygen in air. The study presented here describes the results of GCMC simulations of nitrogen (three site model) adsorption on single and multi walled closed nanotubes. The results obtained are described by a new adsorption isotherm model proposed in this study. The model can be treated as the tube analogue of the GAB isotherm taking into account the lateral adsorbate–adsorbate interactions. We show that the model describes the simulated data satisfactorily. Next this new approach is applied for a description of experimental data measured on different commercially available (and characterized using HRTEM) carbon nanotubes. We show that generally a quite good fit is observed and therefore it is suggested that the observed mechanism of adsorption in the studied materials is mainly determined by adsorption on tubes separated at large distances, so the tubes behave almost independently.

Keywords: Adsorption; GCMC; Carbon nanotubes; Nitrogen; Surface area

Assessment of surfactant adsorption in oil-based magnetic colloids by Modesto T. López-López; Ana Gómez-Ramírez; Guillermo R. Iglesias; Juan D. G. Durán; Fernando González-Caballero (pp. 215-221).

We describe in this paper different and complementary experimental methods for assessing the adsorption of surfactants on metal particles in oil-based suspensions. Two different kinds of particles are dispersed in mineral oil: iron microparticles and CoNi nanoparticles. The adsorption of oleic acid in the Fe/oil interface in diluted suspensions can be determined by obtaining the adsorption isotherm. In addition, we present a method based on the time evolution of the optical absorbance of suspensions, from which the existence of adsorption can be inferred. For concentrated suspensions, the used of optical methods is not recommended, since they are affected by a significant inaccuracy. We present here a useful alternative based on electromagnetic induction phenomena. The results obtained allow a more comprehensive knowledge of the aggregation process in concentrated suspensions. With the same purpose, a third group of experiments, based on rheological techniques, is carried out in Fe/oil and CoNi/oil concentrated suspensions. In these series of experiments, the effect of three surfactants (oleic acid, aluminum stearate and lecithin) is tested by measuring either the viscosity, or the magnetic field-induced yield stress of the suspensions. The combination of these series of experiments gives us valuable information about the most appropriate surfactant/carrier combination capable of imparting a high stability and a strong magnetorheological response in magnetic colloids.

Keywords: Surfactant adsorption; Iron suspensions; Cobalt–Nickel suspensions; Magnetic colloids; Rheology

Mild pre-heating of organic cation-exchanged clays enhances their interactions with nitrobenzene in aqueous environment by Mikhail Borisover; Nadezhda Bukhanovsky; Isaak Lapides; Shmuel Yariv (pp. 223-232).

Aqueous sorption kinetics and equilibrium isotherms of nitrobenzene were studied on two series of sorbents that were prepared by (i) replacing inorganic exchangeable cations in Wyoming bentonite with tetraethylammonium (TEA) and benzyltrimethylammonium (BTMA) and (ii) heating synthesized complexes in air at different temperatures (between 150 and 420°C). The aim of this work was to examine recently observed enhancement of aqueous sorption of a probe organic sorbate on organoclays after mild thermal pre-treatment of sorbents. Thermal pre-treatment of TEA- and BTMA-clays at 150°C results in the maximal enhancement of nitrobenzene–sorbent interactions as compared with treatment of original bentonite and its exchange complexes formed with long-chain quaternary ammonium (n-hexadecyltrimethylammonium, HDTMA). Based on C, N content data and FTIR spectra of TEA- and BTMA-clay complexes, no indications of decomposition of organic matter were found in organoclays heated at 250°C (and below this temperature). Suppressed hydration of pre-heated sorbents resulting in a lessening of water–organic sorbate competition for sorption sites is considered to be responsible for thermally induced enhancement of nitrobenzene–sorbent interactions. In the HDTMA-based organoclays, the long-chain aliphatic groups of the quaternary ammonium can additionally interact with clay surface thus competing with organic sorbate–sorbent surface interactions and, in this way, mitigating the enhancement of nitrobenzene sorption on thermally treated sorbents.

Keywords: Organoclays; Thermal treatment; Sorption enhancement; Montmorillonite; Water-sorbate competition; Clay hydration

Effects of biosurfactants on surface properties of hematite by Agnieszka Szymanska; Zygmunt Sadowski (pp. 233-239).

Application of microorganisms as surface modifiers has focused our attention in recent times. The adsorption of biosurfactants can be a way for the solid surface modification. In the present investigation rhamnolipids produced by Pseudomonas aerugiosa were used to make the hematite surface modification. Experiments were carried out with pure mineral hematite. In this paper, the influence of biosurfactant addition on both the stability and the flotability of hematite suspensions has been studied in detail. The stability experiments were conducted using Turbiscan LAb apparatus, at constant pH conditions and mineral amount. The flotation experiments were carried out using Hallimond tube. The adsorption isotherms of biosurfactant onto the hematite particles were also determined. The experiments were carried out with broth and pure rhamnolipid. The results of those experiments were compared and discussed.

Keywords: Biosurfactants; Rhamnolipid; Adsorption; Sedimentation; Flotation; Hematite

Effects of biosurfactants on surface properties of hematite by Agnieszka Szymanska; Zygmunt Sadowski (pp. 233-239).

Keywords: Biosurfactants; Rhamnolipid; Adsorption; Sedimentation; Flotation; Hematite

Formation and stability of poly-L-lysine/casein multilayers by Lilianna Szyk-Warszyńska; Joanna Piekoszewska; Piotr Warszyński (pp. 241-248).

The aim of our work was to investigate formation of multilayer films containing biocompatible polycation poly-L-lysine (PLL) and α- or β-casein. Since in the neutral pH casein is negatively charged, it has been used as a polyanionic layer for the film build-up. Casein containing films were formed at surface of Si/SiO₂ wafers and their thickness was measured by ellipsometry. The effect of ionic strength of PLL and casein solutions was investigated. After the multilayer films were formed, they were contacted with solutions having various pH and salts to determine film stability under these conditions. Additionally the response of the thickness of PLL/casein films to the temperature variation in the range of 5–45 °C was also analyzed. Formation and stability of casein containing films was also investigated on surfaces of titanium and stainless steel. We used fluorescently labeled protein to monitor the amount of casein in the film and its change after treatment with solutions containing calcium ions.

Keywords: Casein; Layer-by-layer; Polyelectrolyte films; Stability; Multilayers

Formation and stability of poly-L-lysine/casein multilayers by Lilianna Szyk-Warszyńska; Joanna Piekoszewska; Piotr Warszyński (pp. 241-248).

Keywords: Casein; Layer-by-layer; Polyelectrolyte films; Stability; Multilayers

Some data and simple models for the silanated glass-electrolyte interface by J. Lützenkirchen; C. Richter; F. Brandenstein (pp. 249-258).

The interface between silanated glass and aqueous KCl electrolyte solutions was studied by zeta-potential and contact angle measurements. Variation of the pH in the zeta-potential measurements yielded a sharp isoelectric point (IEP) at about pH 4, which was independent of the KCl concentration. This particular pH corresponds to zero electrokinetic potential for many hydrophobic surfaces encompassing Teflon, polyethylene and others.The results are interpreted in terms of hydroxide adsorption at the silanated glass-aqueous interface. A previously developed model for such inert surface—electrolyte interfaces is applied to the experimental data. The model parameters are within the range of those previously obtained for comparable surfaces.Discrepancies were observed in pH dependent contact angle measurements, which were done using both the plate and the drop method: advancing contact angles were always higher than receding contact angles. Advancing contact angles using the drop method yielded no clear tendency as a function of pH and lower values than those obtained by the plate-method. Overall the contact angle data are presented but deemed difficult to interpret in terms of pH dependence and relation to zeta-potentials. A preliminary description of the contact angle data is attempted via the Lippman-Young equation for the different contact angle data sets based on the model potentials. The model results are discussed.Zeta-potential measurements were also performed as a function of salt content within a narrow pH range. As would be expected the presence of a 2:1 electrolyte (BaCl₂) results in lower absolute values when compared to the KCl case.

Keywords: Hydrophobicity; Contact angle; Zeta-potential; Hydroxide ion adsorption

Some data and simple models for the silanated glass-electrolyte interface by J. Lützenkirchen; C. Richter; F. Brandenstein (pp. 249-258).

Keywords: Hydrophobicity; Contact angle; Zeta-potential; Hydroxide ion adsorption

Irreversible adsorption of latex particles on fibrinogen covered mica by Z. Adamczyk; M. Nattich; M. Wasilewska (pp. 259-269).

Physicochemical properties of bovine plasma fibrinogen (Fb) in electrolyte solutions were characterized. These comprised the diffusion coefficient (hydrodynamic radius), determined by the DLS method, electrophoretic mobility and the isoelectric point. The hydrodynamic radius of Fb was 12 nm for pH<5. The number of uncompensated (electrokinetic) charges on the protein N c was calculated from the electrophoretic mobility data. It was found that for pH<5.8 the electrokinetic charge was positive, independently of the ionic strength and negative for pH>5.8. For pH=3.5 the value of N c, was 26 for 10⁻³ M. Similar electrokinetic measurements were performed for the mica substrate using the streaming potential cell. It was shown that for pH=3.5 and 10⁻³ M, the zeta potential of mica remained negative (−50 mV). This promoted an irreversible, electrostatically driven adsorption of Fb, which was confirmed in experiments carried out under diffusion-controlled transport. The surface concentration of Fb on mica was determined directly by AFM counting. By adjusting the time of adsorption, Fb monolayers of desired coverage were produced. Independently, the presence of Fb on mica was determined quantitatively by the colloid enhancement method, in which negatively charged latex particles were used, having the diameter of 800 nm. It was found that for Fb coverage below 0.05 the method was more sensitive than other indirect methods. The experimental data obtained in latex deposition experiments were adequately interpreted in terms of the random site model used previously for polyelectrolytes. It was shown that adsorption sites consisted of a cluster of two Fb molecules. It was concluded that the colloid enhancement method can be successfully used for detecting the presence of proteins at solid substrates and to determine the uniformity of monolayers in the nanoscale.

Keywords: Fibrinogen monolayers on mica; Colloid enhancement of protein layers; Adsorption of latex on fibrinogen; Irreversible adsorption of colloid particles

Irreversible adsorption of latex particles on fibrinogen covered mica by Z. Adamczyk; M. Nattich; M. Wasilewska (pp. 259-269).

Keywords: Fibrinogen monolayers on mica; Colloid enhancement of protein layers; Adsorption of latex on fibrinogen; Irreversible adsorption of colloid particles

Changes of methylated silica surfaces on ageing by Nora Schreithofer; Janusz S. Laskowski; Kari Heiskanen (pp. 271-277).

Silica rendered hydrophobic by organosilanes is a widely used model material in colloid chemistry, biological research, catalysis, etc. However, it is often overlooked that the surface properties of silica, and silica made hydrophobic be reacting with silane, change with time when the substrate is immersed in aqueous solution. Therefore the experimental conditions when such model systems are employed have to be carefully assessed.This paper summarizes the findings of the force measurement tests between air bubbles and silica particles hydrophobized with organosilanes such as trimethylchlorosilane and 1,1,1,3,3,3-hexamethyl-disilazane. The results showed that the attractive forces as well as the adhesion between the air bubbles and silica particles decrease with the time of aging in aqueous solution. The silica surfaces rendered hydrophobic with organosilanes become hydrophilic with time due to hydration. The hydrophobicity could be restored by heating the samples at 190 ^○C.The atomic force microscopy imaging on silica plates revealed that in addition to hydration, decomposition of the organosilane layer also takes place.

Keywords: Silica; Silica surface; Hydration; Methylated silica; AFM

Changes of methylated silica surfaces on ageing by Nora Schreithofer; Janusz S. Laskowski; Kari Heiskanen (pp. 271-277).

Keywords: Silica; Silica surface; Hydration; Methylated silica; AFM

Study of chromium(VI) adsorption onto modified activated carbons with respect to analytical application by Ryszard Dobrowolski; Magdalena Otto (pp. 279-286).

Two different types of modification of activated carbon, by treatment with concentrated solution of HNO₃ and outgassing treatment at high temperature, were studied in order to obtain the most effective adsorption of chromium(VI) ions from water solution. The basic parameters affecting the adsorption capacity of Cr(VI) ions on modified activated carbons were studied in details and the effect of modifications of activated carbons has been determined by studying the initial runs of adsorption isotherms. The obtained Cr(VI) adsorption isotherms were well fitted in the Freundlich equation. The reduction of Cr(VI) to Cr(III) and further ion exchange mechanism of adsorption onto oxidizing activated carbon and surface precipitation to Cr(OH)₃ in case of outgassing activated carbon were found as the main adsorption mechanisms of Cr(VI) ions onto modified activated carbons. Presence of chlorides and nitrates in studied adsorption system strongly decreased the adsorption ability of Cr(VI) onto outgassing activated carbon and mechanism of this behavior is proposed.

Keywords: Chromium adsorption; Modified activated carbons; Enrichment; Atomic absorption spectrometry

Study of chromium(VI) adsorption onto modified activated carbons with respect to analytical application by Ryszard Dobrowolski; Magdalena Otto (pp. 279-286).

Keywords: Chromium adsorption; Modified activated carbons; Enrichment; Atomic absorption spectrometry

Separation selectivity of some phenolic acids in RP HPLC systems with binary mobile phase comprised various modifiers by Anna Klimek-Turek; Tadeusz H. Dzido (pp. 287-294).

Retention of phenolic acid has been correlated for reversed-phase high-performance liquid chromatography systems with different binary mobile phases containing methanol, acetonitrile or tetrahydrofuran as modifiers and buffer at pH 3.0, 4.6 and 5.0. The changes of separation selectivity of solutes, when one modifier is replaced by another in the eluent, has been explained taking into consideration molecular interactions of the solutes with components of the stationary phase region, i.e. extracted modifier, and ordering of the stationary phase by the modifier.

Keywords: Modifier selectivity; Mechanism of separation selectivity in reversed phase liquid chromatography; Phenolic acids

Separation selectivity of some phenolic acids in RP HPLC systems with binary mobile phase comprised various modifiers by Anna Klimek-Turek; Tadeusz H. Dzido (pp. 287-294).

Keywords: Modifier selectivity; Mechanism of separation selectivity in reversed phase liquid chromatography; Phenolic acids

Adsorption of alkali metal cations and halide anions on metal oxides: prediction of Hofmeister series using 1-pK triple layer model by Wojciech Piasecki; Piotr Zarzycki; Robert Charmas (pp. 295-303).

Adsorption of electrolyte ions on metal oxides significantly affects the interfacial charge distribution. The general procedure for the prediction of surface charge on oxides in salt solutions was given by Sverjensky for the 2-pK Triple Layer Model (2-pK TLM) (Sverjensky, Geochim. Cosmochim. Acta 69:225–257, 2005). Based on his parameters values and by assuming parameters transferability (Piasecki, J. Colloid Interface Sci. 302:389–395, 2006) we have predicted the adsorption constants for three monovalent ions (Rb⁺, F⁻, Br⁻) for eight oxides within the framework of the 1-pK Triple Layer Model (1-pK TLM). The obtained parameters values along with the previously reported ones (Piasecki, J. Colloid Interface Sci. 302:389–395, 2006) allowed us to compare the adsorption affinities of alkali metal cations and halide anions, and construct the following Hofmeister series for the cations (Cs⁺≈ Rb⁺≈ K⁺< Na⁺< Li⁺) and for the anions (F⁻≫ Cl⁻≈ Br⁻< I⁻) for investigated oxides. The same lyotropic series was predicted by the 2-pK TLM. It indicates that Hofmeister series is invariable during parameter transfer between surface complexation models.

Keywords: Hofmeister series; Ion adsorption; Metal oxides; 1-pK model

Changes of zeta potential and particles size of silica caused by DPPC adsorption and enzyme phospholipase A₂ presence by E. Chibowski; A. Szcześ; L. Hołysz (pp. 305-312).

The changes in electrokinetic properties of silica suspensions in the presence of 1,2-dipalmitoyl-sn-glycero-3-phospshocholine (DPPC) were investigated via zeta potential, mean diameter and transmittance determinations. Silica particles were precovered with monolayer (ML) or bilayer (BL) of the phospholopid from chloroform solution (SiO₂/DPPC) or covered by DPPC adsorption from aqueous solution (SiO₂+DPPC). The zeta potential and mean diameter of SiO₂/DPPC suspension were measured as a function of NaCl concentration and due to the phospholipase A₂(PLA₂) action in 10⁻³ M NaCl solution and buffer Tris at pH=8 and 9. It was found that the DPPC adsorption onto silica surface decreases its the zeta potential, however the suspensions were stable during the experiment time, probably because of steric stabilization. During PLA₂ enzyme action the changes in zeta potential were observed, which were caused by the hydrolysis products, especially palmitic acid molecules, which also had influence on the stability of these systems.

Keywords: DPPC; Silica; Phospholipase A₂ ; Zeta potential; Transmittance; Particle size; Stability

Changes of zeta potential and particles size of silica caused by DPPC adsorption and enzyme phospholipase A₂ presence by E. Chibowski; A. Szcześ; L. Hołysz (pp. 305-312).

Keywords: DPPC; Silica; Phospholipase A₂ ; Zeta potential; Transmittance; Particle size; Stability

Types of particles recovery—water recovery entrainment plots useful in flotation research by Zaklina Konopacka; Jan Drzymala (pp. 313-320).

This review paper deals with graphical representation of entrainment experienced by fine particles during passing, either barren or mineralized, bubbles through flotation cells. Entrainment, also called mechanical carryover or mechanical flotation, is harmful because it reduces the quality of flotation concentrates. It was presented in the paper that it is convenient to show the results of entrainment as upgrading separation plots relating recovery of fines vs. water recovery. The shape of the entrainment separation curves significantly depends on the way flotation test is performed, type of flotation machine, kinetics of process, froth collecting time, concentration of frothers, collectors and modifiers, amount of air in flotation, density of pulp, amount of supplied water etc. Five types of entrainment separation plots were distinguished and presented in the paper. They were categorized as linear (type 1), linear shifted down (type 2), reaching plateau (type 3), increasing (type 4) and linear shifted up (type 5). The plots are useful for determination of appropriate entrainment coefficients characterizing the process.

Keywords: Entrainment; Mechanical carryover; Mechanical flotation; Froth flotation

Types of particles recovery—water recovery entrainment plots useful in flotation research by Zaklina Konopacka; Jan Drzymala (pp. 313-320).

Keywords: Entrainment; Mechanical carryover; Mechanical flotation; Froth flotation

Influence of solution pH on stability of aluminum oxide suspension in presence of polyacrylic acid by S. Chibowski; M. Wiśniewska; T. Urban (pp. 321-332).

The effect of solution pH and molecular weight of polyacrylic acid (PAA) on its adsorption as well as on stabilization-floculation properties of the colloidal Al₂O₃ and electrolyte solution systems was studied.The measurements showed that at pH = 6, the presence of the polymer of molecular weight 2 000 and 240 000 does not change stability of Al₂O₃ suspension. However at pH =3 and 9 the effect of polyacrylic acid is significant. At pH = 3 it creates destabilization of the suspension while at pH = 9 PAA it improves significantly the stability of Al₂O₃.It was shown that the increase in solution pH affects conformation of adsorbed macromolecules which causes the decrease in PAA adsorbed amount and thickness of polymer adsorption layer.By comparing the values of diffusion layer and surface charges, main effects responsible for the decrease in surface charge and ζ potential of the solid in the presence of the polymer as well as suspension stability were determined.

Keywords: Polymer adsorption; pH influence; Polyacrylic acid; Suspension stability; Alumina

Influence of solution pH on stability of aluminum oxide suspension in presence of polyacrylic acid by S. Chibowski; M. Wiśniewska; T. Urban (pp. 321-332).

Keywords: Polymer adsorption; pH influence; Polyacrylic acid; Suspension stability; Alumina

Some properties of milled vanadium phosphates by Władysław Janusz; Svetlana Khalameida; Volodymyr Sydorchuk; Ewa Skwarek; Valery Zazhigalov; Jadwiga Skubiszewska-Zięba; Roman Leboda (pp. 333-341).

Mechanochemical modification of vanadium phosphates doped with Bi, Zr, Mo has been studied. Milled samples have been investigated by means of XRD, DTA-TG, FTIR, nitrogen adsorption, electrokinetic measurements. It was found that phase composition of the phosphates does not change upon the mechanochemical modification process. Milling in water causes formation of porous materials. Modification of surface results in changes of the electrokinetic and adsorption properties of the milled samples.

Keywords: Vanadium phosphates; Mechanochemical treatment; Potential ζ; Ni(II); Adsorption

Simple model of surface-induced electrolytic dissociation of weak acids in organic solvents by Marek Kosmulski (pp. 343-349).

The electric conductivity of solutions of oxalic and phosphoric acid (up to 0.025 M) in ethanol and methanol has been studied in the presence of TiO₂ (1–10% by mass). TiO₂ enhanced the conductivity of solutions of oxalic and phosphoric acid in the both alcohols. The experimentally observed behavior was successfully modeled using a model with two types of surface sites. Sites of the first type bind the acids in molecular form. Sites of the second type bind the acids in form of hydrogen oxalate and dihydrogen phosphate anions, respectively, and protons are released to the solution, and contribute to enhanced conductivity. The adsorption model properly reflects the electrokinetic potential of titania particles in alcoholic solutions of oxalic and phosphoric acid.

Keywords: Organic solvents; Non-aqueous solvents; Degree of dissociation; Electrolytic dissociation; Adsorption; Surface heterogeneity; Zeta potential

How does mechanism of biosorption determine the differences between the initial and equilibrium adsorption states? by Władysław Rudzinski; Wojciech Plazinski (pp. 351-357).

The analysis of various models assumed to represent the influence of pH on heavy metals biosorption equilibrium is presented. It shows that all of them lead to the same mathematical expressions (e.g. the Langmuir or the Flory adsorption isotherm equations) when the pH effects are neglected. Even if considering the pH effects, some of them (competitive adsorption and ion-exchange models, for instance) still lead to analogical expressions for sorption isotherm equations. The accepted mechanism of biosorption may, however, influence strongly the differences between the initial and equilibrium states of biosorption system.

Keywords: Biosorption; Ion exchange; Competitive adsorption; Non-competitive adsorption; pH

How does mechanism of biosorption determine the differences between the initial and equilibrium adsorption states? by Władysław Rudzinski; Wojciech Plazinski (pp. 351-357).

Keywords: Biosorption; Ion exchange; Competitive adsorption; Non-competitive adsorption; pH

Studies of adsorption equilibria and kinetics of o-, m-, p-nitro- and chlorophenols on microporous carbons from aqueous solutions by Anna Derylo-Marczewska; Katarzyna Miroslaw; Adam W. Marczewski; Dariusz Sternik (pp. 359-375).

The studies of adsorption of o-, m-, and p-nitrophenols and chlorophenols from aqueous solutions on microporous activated carbon are presented. The adsorption isotherms were measured at different temperatures: 288, 298, 308 and 318 K. The thermal analysis was applied in order to find the differences in solute interactions with adsorbent surface. The kinetic dependences were measured and the relations between position of adsorbate functional groups and adsorption rate were discussed. The adsorption data are analyzed in terms of the theory of physical adsorption on energetically non-homogeneous solids. The relations between the adsorbate structure and adsorption effectiveness, and the influence of temperature are discussed.

Keywords: Adsorption from solutions; Adsorption equilibria and kinetics; Microporous carbon

Adsorption properties of phenolic resin-based mesoporous carbons obtained by using mixed templates of Pluronic F127 and Brij 58 or Brij 78 polymers by Jerzy Choma; Anna Żubrowska; Joanna Górka; Mietek Jaroniec (pp. 377-383).

Phenolic resin-based mesoporous carbons were synthesized by using mixed templates of Pluronic F127 and Brij 58 or Brij 78. For the purpose of comparison three samples of nanoporous carbons were prepared by using single templates of Pluronic F127, Brij 58 and Brij 78 polymers, respectively. Adsorption properties of the aforementioned carbons were studied by nitrogen adsorption at −196 °C. The resulting carbons featured high specific surface areas ranging from 641 m²/g for the sample obtained in the presence of Brij 58 polymer to 825 m²/g for the carbon prepared by using a mixed template containing 23% of Pluronic F127 and 77% of Brij 58 and from 588 m²/g for the sample obtained in the presence of Brij 78 polymer to 813 m²/g for the carbon prepared by using Pluronic F127 only. It was shown that the width of mesopores increases with increasing amount of Brij 58 or Brij 78 in the mixture of one of these polymers with Pluronic F127, suggesting that Brij polymers act also as micelle expanders.

Keywords: Mesoporous carbons; Soft templating; Mixed polymeric templates; Adsorption properties; Phenolic resin

Adsorption properties of ordered mesoporous silicas synthesized in the presence of block copolymer Pluronic F127 under microwave irradiation by Bogna E. Grabicka; Mietek Jaroniec (pp. 385-396).

Ordered mesoporous silicas (OMSs) were prepared at different temperatures by using tetraethyl orthosilicate (TEOS) as a silica source, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (Pluronic F127) as a structure directing agent and sodium chloride as an additive under acidic conditions and microwave irradiation. The small angle X-ray diffraction patterns of these samples indicate the presence of ordered mesopores, while adsorption studies show that they possess high volumes of pores, bimodal pore size distributions and large pore sizes. There is an interesting change in the hysteresis loop of nitrogen adsorption isotherms with increasing temperature of hydrothermal treatment; a delayed desorption characteristic for cage-like mesostructures is observed for the OMS samples treated at 100 and 120 °C, while the hydrothermal treatment at 140 and 160 °C leads to the samples having hysteresis loops characteristic for channel-like materials.

Keywords: Mesoporous ordered silica; Microwave-assisted synthesis; Nitrogen adsorption; Cage-like mesostructures; Channel-like mesostructures

Adsorption properties of ordered mesoporous silicas synthesized in the presence of block copolymer Pluronic F127 under microwave irradiation by Bogna E. Grabicka; Mietek Jaroniec (pp. 385-396).

Keywords: Mesoporous ordered silica; Microwave-assisted synthesis; Nitrogen adsorption; Cage-like mesostructures; Channel-like mesostructures

Selectivity in normal-phase liquid chromatography with binary mobile phase by Małgorzata Borówko; Barbara Ościk-Mendyk (pp. 397-403).

A simple theoretical approach to normal-phase liquid chromatography with binary mobile phase is presented. In the model used the driving force for the retention is competitive adsorption of solutes and both solvents. A new expression for the separation factor is proposed and discussed. An influence of different parameters on the selectivity is shown. The theoretical concepts are illustrated by the selected experimental data.

Keywords: Retention mechanism; Liquid–solid chromatography; Selectivity; Adsorption from solutions

Selectivity in normal-phase liquid chromatography with binary mobile phase by Małgorzata Borówko; Barbara Ościk-Mendyk (pp. 397-403).

Keywords: Retention mechanism; Liquid–solid chromatography; Selectivity; Adsorption from solutions

Electrical interfacial layer at TiO₂/poly(4-styrene sulfonate) aqueous interface by Davor Kovačević; Darko Mazur; Tajana Preočanin; Nikola Kallay (pp. 405-412).

The interfacial properties of the system titanium(IV) oxide/poly(4-styrenesulfonate) (PSS) over a broad pH region in the presence of different alkali metal chlorides of different concentrations were investigated by means of electrokinetic, adsorption and surface potential measurements. Adsorption and electrokinetic data were obtained with colloid TiO₂ particles, while surface potential data were obtained using a single crystal rutile electrode with the 001 plane exposed to the liquid medium. The electrokinetic and surface potentials of TiO₂ were measured in the absence and presence of PSS. Since the presence of PSS did not significantly affect surface potentials, it was concluded that negative PSS molecules adsorbed at the surface by forming an outer-sphere surface complex rather than inner-sphere complex. The adsorption decreases significantly with pH, while the electrokinetic potential in the presence of PSS is negative in the whole investigated pH region. Amount of adsorbed PSS molecules is limited by the electrostatic repulsion which suppresses further adsorption, i.e. above critical potential of −50 millivolts. In the acidic region, where the surface is originally positively charged the amount of adsorbed PSS molecules is high since negative PSS molecules should at first compensate original positive charge and in the second step reverse the charge to reach the critical potential. In the basic region the surface charge is already negative so that small amount of adsorbed PSS molecules creates critical potential that prevents further adsorption.

Keywords: Titanium oxide; Poly(4-styrene sulfonate); Surface potential; Adsorption; Zeta potential

Electrical interfacial layer at TiO₂/poly(4-styrene sulfonate) aqueous interface by Davor Kovačević; Darko Mazur; Tajana Preočanin; Nikola Kallay (pp. 405-412).

Keywords: Titanium oxide; Poly(4-styrene sulfonate); Surface potential; Adsorption; Zeta potential

A review of boron enhanced nanoporous carbons for hydrogen adsorption: numerical perspective by B. Kuchta; L. Firlej; S. Roszak; P. Pfeifer (pp. 413-421).

We review the current achievements in the numerical studies of adsorption of molecular hydrogen in boron substituted nanoporous carbons. We show that the enhanced attraction of H₂ by boron-substituted all-carbon structures may allow designing new porous materials with modulated capacity for hydrogen adsorption. Such new structures are characterized by modification of energy landscape of adsorbing surfaces extending beyond the vicinity of substituted atom over several graphene carbon sites, and show strong surface heterogeneity. Although the theoretical conception and description of boron-substituted carbons made a considerable progress during the last decade, the preparation of these materials involves tedious procedures and still needs to be improved.

Keywords: Hydrogen; micro-pores; Boron; Adsorption

A review of boron enhanced nanoporous carbons for hydrogen adsorption: numerical perspective by B. Kuchta; L. Firlej; S. Roszak; P. Pfeifer (pp. 413-421).

Keywords: Hydrogen; micro-pores; Boron; Adsorption

Influence of pH of the BSA solutions on velocity of the rising bubbles and stability of the thin liquid films and foams by J. Zawala; R. Todorov; A. Olszewska; D. Exerowa; K. Malysa (pp. 423-435).

Influence of pH of the BSA solutions on velocity of the rising bubbles, stability of foams, and properties of single foam and wetting films was studied. It was found that the solution pH affected significantly the BSA surface activity and properties of the protein adsorption layer under dynamic and static conditions. At pH close to the isoelectric point (pH_IEP=4.8) the BSA showed the highest surface activity. The equilibrium microscopic foam films of thicknesses of 64–80 nm, depending on the BSA concentration, were obtained at pH=5.8. Under dynamic conditions the bubble rising velocity was reduced in a highest degree and the foam formed were most stable at the solutions pH-5.8 and 4.8. Lowering the bubble velocity shows that the BSA adsorption layer was formed, which retarded fluidity of the bubble surface. When the solution pH was significantly lower (pH=3.9) or much higher (pH=10) than the pH_IEP then the BSA practically had no influence on the bubble velocity and the foam stability was drastically reduced. Moreover, the pH variations affected also the time of the three-phase contact (TPC) formation on mica surface covered by the BSA adsorption layers. These pH dependent changes in the BSA surface activity indicate that the BSA linear conformers, existing at pH far away from the pH_IEP, have much higher affinity to aqueous phase resulting from higher net electrical charge present over the extended BSA molecule conformers.

Keywords: Bovine serum albumin; BSA conformers; Adsorption layer; BSA surface activity; Bubble velocity; Foam film thickness; Foam stability

Influence of pH of the BSA solutions on velocity of the rising bubbles and stability of the thin liquid films and foams by J. Zawala; R. Todorov; A. Olszewska; D. Exerowa; K. Malysa (pp. 423-435).

Keywords: Bovine serum albumin; BSA conformers; Adsorption layer; BSA surface activity; Bubble velocity; Foam film thickness; Foam stability

Influence of temperature and pressure on the preferential adsorption of component of hydroorganic mobile phase in liquid chromatography by Bogusław Buszewski; Szymon Bocian; Rafał Zera (pp. 437-445).

The excess isotherms of methanol and acetonitrile were measured on the series of C18 bonded phases. The measurements were done using the minor disturbance method. The goal of our work was to determine the influence of the temperature on the adsorption of two commonly used solvents. The influence on the mobile phase flow rate on the both organic solvent adsorption was also investigated. The effect of these two parameters was compared on the octadecyl packed columns with different coverage density and on the monolithic Chromolith column. Adsorption of both solvents decreases with the increase of the temperature. The increase of the pressure increases adsorption of methanol but decreases adsorption of acetonitrile.

Keywords: Solvent adsorption; Stationary phase; Excess isotherm; Flow rate; Temperature

Adsorption of sodium lignosulfonates on hematite by Balakrishnan Nanthakumar; Esau Arinaitwe; Marek Pawlik (pp. 447-455).

The adsorption of three sodium lignosulfonates on hematite was studied as a function of pH in the range from 4 to 10.5, and in the presence or absence of calcium ions (10⁻³ mol/L calcium choride). Intrinsic viscosity measurements demonstrated that the effective size of the macromolecules was not significantly affected under the experimental conditions. The adsorption results showed that electrostatic forces between the anionic polyelectrolytes and the hematite surface controlled the adsorption process although substantial non-electrostatic interactions were also clearly observed. The adsorption density inversely correlated with the anionicity of the tested lignosulfonates, especially with the content of sulfonic groups, with the least anionic polyelectrolyte producing the highest adsorption level. It was suggested that lateral repulsive electrostatic forces between the adsorbed macromolecules prevented dense adsorption of more anionic lignosulfonates. From this point of view, the effect of calcium on adsorption was attributed not only to its specific adsorption and surface charge reversal, but also to screening the anionic groups of lignosulfonates and minimizing the lateral repulsive interactions especially at high pH.

Keywords: Lignosulfonates; Hematite; Intrinsic viscosity; Adsorption

Adsorption of sodium lignosulfonates on hematite by Balakrishnan Nanthakumar; Esau Arinaitwe; Marek Pawlik (pp. 447-455).

Keywords: Lignosulfonates; Hematite; Intrinsic viscosity; Adsorption

Studies of the structure and chemistry of SBA-15 organosilicas functionalized with amine, thiol, vinyl and phenyl groups by Mariusz Barczak; Andrzej Dąbrowski; Stanisław Pikus; Janusz Ryczkowski; Piotr Borowski; Maciej Kozak (pp. 457-463).

SBA-15 organosilicas containing amine, thiol, vinyl and phenyl pendant groups were synthesized by co-condensation of tetraethoxysilane and appropriate alkoxysilanes in the presence of Pluronic P123 surfactant. The obtained materials have usually well-developed porous structure—values of specific surface area are in the range 820–950 m²/g. Sizes of the ordered mesopores are in the range 7.5–9.1 nm while the interconnecting pores are 2.3–3.1 nm in size. It was establish that size of the mesopores strongly depends even on small amounts of co-monomers co-condensing with tetraethoxysilane. Several instrumental techniques such as infrared spectroscopy, X-ray diffraction, nitrogen sorption measurements, elemental analysis, transmission electron microscopy. FT-IR photoacoustic spectroscopy (FT-IR/PAS) was used to determine chemical composition of the final materials and to monitor the efficiency of the template removal.

Keywords: Organosilicas; SBA-15; Ordered mesoporous materials; OMOs; Functionalization; Pluronic P123; Adsorption; Porosity

A family of ordered mesoporous carbons derived from mesophase pitch using ordered mesoporous silicas as templates by Liang Cao; Michal Kruk (pp. 465-472).

A variety of ordered mesoporous carbons (OMCs) were synthesized using ordered mesoporous silicas (OMSs) as hard templates and the mesophase pitch (MP) as a carbon precursor. The synthesis included the mixing of OMS with MP, the infiltration of OMS with MP at 450–550 °C and the carbonization of MP in OMS/MP composite followed by the dissolution of the OMS template. OMCs with structures of two-dimensional hexagonal arrays of nanorods and three-dimensional arrays of nanospheres were obtained through the replication of silica templates, including large-pore SBA-15, KIT-6, large-pore FDU-12 and SBA-16. In particular, 2-D hexagonal array of carbon nanorods (CMK-3 carbon) with (100) interplanar spacing of ∼13 nm as well as an array of carbon nanospheres arranged in the face-centered cubic structure with the unit-cell parameter of 33 nm were successfully prepared. The specific surface areas of the resulting carbons were up to 400 m²/g, and the total pore volumes were up to 0.43 cm³/g, with the highest values achieved when the MP infiltration temperature was 500 °C. The OMCs exhibited narrow mesopore size distributions. As inferred from XRD, the frameworks of OMCs featured semi-graphitic structures even though moderate carbonization temperature (850 °C) was employed.

Keywords: Ordered mesoporous carbon; Templated synthesis; Ordered mesoporous silica; Mesophase pitch; High-surface-area solid

A family of ordered mesoporous carbons derived from mesophase pitch using ordered mesoporous silicas as templates by Liang Cao; Michal Kruk (pp. 465-472).

Keywords: Ordered mesoporous carbon; Templated synthesis; Ordered mesoporous silica; Mesophase pitch; High-surface-area solid

Molecularly imprinted adsorbents for preconcentration and isolation of progesterone and testosterone by solid phase extraction combined with HPLC by Júlia Ričanyová; Renata Gadzała-Kopciuch; Katarina Reiffova; Yaroslav Bazel; Bogusław Buszewski (pp. 473-483).

The use of a novel procedure of solid-phase extraction with molecularly imprinted polymers (MISPE) has been described. A MISPE procedure relying on tailor-made, artificial-mimic materials capable of selectively rebinding target analytes (steroids) based on a combination of recognition mechanisms, such as size, shape and functionality, was custom designed for progesterone and testosterone. The combination of MISPE with LC/DAD is a simple and an efficient method for the determination and quality control of progesterone and testosterone in human urine samples.

Keywords: Steroids; Molecularly imprinted adsorbents; MISPE; HPLC; DAD

The impact of microwave energy on the results of silica gel hydrothermal modification by J. Skubiszewska-Zięba (pp. 485-493).

Two series of the hydrothermally treated (HTT) silica gel samples using the microwave reactor or the classical autoclave have been prepared. The HTT modification processes have been performed under the liquid water layer or in the water vapour. The initial and HTT silica samples were examined by means of adsorption (N₂), thermogravimetric (TG) and infra red (FTIR-ATR) methods. On the basis of the obtained results it was stated that even a short time of HTT modification using microwaves is enough to make distinct changes in the porous structure of silica. The time and pressure are the most influential parameters during HTT using microwaves. However, in the case of the samples modified in the classical autoclave the most important factors are temperature and time. The hydrothermally modified silica samples possess different concentration of intraglobular water dependently on applied treatment conditions and water state.

Keywords: Silica gel; Hydrothermal treatment; Microwaves; Water vapour; Porous structure

The impact of microwave energy on the results of silica gel hydrothermal modification by J. Skubiszewska-Zięba (pp. 485-493).

Keywords: Silica gel; Hydrothermal treatment; Microwaves; Water vapour; Porous structure

Sections

Personal tools

Adsorption: Journal of the International Adsorption Society (v.16, #4-5)

Sections

Personal tools

Local resources

Adsorption: Journal of the International Adsorption Society (v.16, #4-5)