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Several biocomposites were synthesized by copolymerizing hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) at varied molar ratios in the presence of different wt% of collagen (CLG) and attapulgite (APG) clay. The structure and properties of the biocomposite adsorbents were characterized by Fourier transform infrared apectroscopy, nuclear magnetic resonance, X-ray photo electron spectroscopy, X-ray diffraction, scanning electron microscope, transfer electron microscopy, energy-dispersive X-ray analysis, differential thermal analysis-thermogravimetric analysis, point zero charge analysis, mechanical properties, and pH reversibility tests. The synthesis variables were optimized with a central composite design of response surface methodology (RSM). The biocomposite prepared with an optimized composition of 1.5 wt% CLG, 1.7 wt% APG, and 5:1 molar ratio of HEMA:IA showed an adsorption capacity ([Q.sub.e], mg/g) of 674.4/602.4 for methylene blue (MB)/Rose Bengal (RB) dye from a feed containing 200 mg/L of MB + RB dye mixture in batch mode. In a fixed bed in column mode, the optimized biocomposite showed a removal% of 82.8/71.3 for 100 mg/L inlet concentration, 20 ml/min flow rate, and 20 mm bed height with a breakthrough time of 23/31 min and a mass transfer coefficient ([k.sub.mtc] * [10.sub.5] cm/s) of 8.36/7.67 for MB/RB as single dye solution. KEYWORDS batch and column adsorption, biocomposite adsorbent, collagen and attapulgite, copolymer, mass transfer coefficient, RSM, 1 | INTRODUCTION Natural or semisynthetic polymers such as chitosan, starch, sodium alginate, or collagen (CLG) contain numerous functional groups such as hydroxyl (-OH), ketone (C=O), carboxyl (-COOH), or amines. [...]

An adsorbent doped polyaniline (PANI) has been explored for the elimination of a cationic azodye, basic red 46 (BR-46), from textile effluent. Essential factors from batch mode have been studied to investigate their effect on the removal of BR-46. The investigated data have been applied to two prevalent adsorption isothermal models (i.e., Langmuir and Freundlich). In addition to the coefficients of determination, six different statistical error functions have been used to identify the most appropriate model for the existing process. The Langmuir model has been shown to be the best adsorption isotherm with minimum error values and a high coefficient of determination value ([R.sup.2] > 0.999). The maximum monolayer adsorption capacity observed was 1.83 * [10.sup.-4] mol [g.sup.-1] at 50 [degrees]C. Thermodynamic parameters of Gibb's free energy, enthalpy, and entropy were found to be -30.06 KJ [mol.sup.-1], 374 J [mol.sup.-1], and 97.25 J [mol.sup.-1] [K.sup.-1], respectively. The positive values of enthalpy and entropy indicate the process to be endothermic. The amount of the dye adsorbed increased from 1.02 to 5.42 * [10.sup.-5] g in moving from 30 to 50 [degrees]C. The measured energy of activation was 17.467 kJ [mol.sup.-1]. The maximum percent removal of BR-46 from wastewater has been 93% at pH 8. Key words: adsorption, basic red 46, error analysis, endothermic, entropy. Nous avons étudié une polyaniline (PANI) dopée d'un adsorbant pour l'élimination du colorant azoïque cationique rouge basique 46 (BR-46) des effluents textiles. Nous avons examiné les facteurs essentiels du mode de traitement par lots afin d'évaluer leur effet sur l'élimination du BR-46. Nous avons appliqué les données étudiées à deux modèles d'adsorption isotherme prévalents (c.-à-d. les modèles de Langmuir et de Freundlich). En plus des coefficients de détermination, nous avons utilisé six différentes fonctions d'erreur statistique pour déterminer le modèle le plus approprié au processus existant. Le modèle de Langmuir s'est révélé être le meilleur modèle d'isotherme d'adsorption, avec des valeurs d'erreur minimales et une valeur de coefficient de détermination élevée ([R.sup.2] > 0,999). La capacité maximale d'adsorption monocouche observée était de 1,83 * [10.sup.-4] mol [g.sup.-1] à 50 [degrees]C. Nous avons observé que les paramètres thermodynamiques que sont l'énergie libre de Gibbs, l'enthalpie et l'entropie étaient de -30,06 kJ [mol.sup.-1], de 374 J [mol.sup.-1] et de 97,25 J [mol.sup.-1] [K.sup.-1], respectivement. Les valeurs positives de l'enthalpie et de l'entropie indiquent que le processus est endothermique. La quantité de colorant adsorbé a augmenté, passant de 1,02 à 5,42 * [10.sup.-5] g lorsque la température est passée de 30 à 50 [degrees]C. L'énergie d'activation mesurée était de 17,467 kJ * [mol.sup.-1]. Le pourcentage maximal d'élimination du BR-46 des eaux usées a été de 93% à pH 8. [Traduit par la Rédaction] Mots-clés : adsorption, rouge basique 46, analyse d'erreur, endothermique, entropie., Introduction Textile effluent largely contains dyestuffs from assorted origins such as textiles, plastic, paper, cosmetics, pharma, rubber, printing, and leather industries. (1) Approximately 800 000 tons of synthetic dyes are [...]

The boronic acid functionalization metal-organic frameworks (MOFs), as unique boronate affinity adsorbents, have desired specific molecular affinity for the separation and enrichment of cis-diol-compounds. Herein, the boronic acid functionalized Zn-based MOF adsorbent (MOF-BA) was synthesized through a simple one-step microwave method and used for the recognition and isolation of steviol glycosides (SGs). This MOF-BA exhibits the same spherical structure and isostructure with the parent framework composed only of the primitive ligand as verified by SEM and XRD characterization. It was confirmed that changing the ratio of ligands could achieve the adjustability of the boron content in the framework. At the same time, the MOF-BA-1.0 showed a suitable pore size (4.69 nm), and the presence of boric acid functional groups showed favorable selectivity for stevioside (STV). The static adsorption results showed that adsorption performances of rebaudioside A (RA) and STV from crude sugar solution (5.0 mg [mL.sup.-1], pH 8) on MOF-BA-1.0 were investigated at 303 K for 15 h. The adsorption capacities for STV and RA were 42.93 mg [g.sup.-1] and 22.96 mg [g.sup.-1], respectively, and the adsorption selectivity ([[alpha].sub.STV/RA]) reached 4.35. The adsorption isotherm and kinetic data of MOF-BA-1.0 for RA and STV obeyed the Langmuir isotherm model and pseudo second order kinetic model, respectively. The study demonstrated that MOF-BA-1.0 adsorbent could be used as a potential adsorbent to purify the active ingredients of stevia and obtain a high concentration of RA products. Key words: boronic acid functionalized metal organic framework (MOF-BA), separation, stevioside, rebaudioside A. Les réseaux métallo-organiques (MOF, metal-organic frameworks) fonctionnalisés par un acide boronique, employés comme adsorbants possédant une affinité pour un boronate en particulier, présentent une affinité moléculaire spécifique qui est souhaitable pour effectuer la séparation et l'enrichissement des composés cis-diol. Dans le présent article, nous avons synthétisé un adsorbant consistant en un MOF à base de Zn fonctionnalisé par un acide boronique (MOF-BA) au moyen d'une méthode simple en une étape, fondée sur les micro-ondes, et nous avons utilisé cet adsorbant pour effectuer la reconnaissance et l'isolation des glycosides du stéviol (GS). Ce MOF-BA présente la même structure sphérique et isostructure que le MOF parent, qui se compose uniquement du ligand primitif, tel que le confirme la caractérisation par microscopie électronique à balayage (MEB) et par diffraction des rayons (DRX). Nous avons démontré qu'il est possible de moduler la teneur du bore dans le MOF en variant le rapport des ligands. Par ailleurs, le MOF-BA-1.0 présentait une taille de pores appropriée (4,69 nm), et la présence de groupes fonctionnels àbase d'acide borique a conféré à ce composé une sélectivité favorable pour le stévioside (STV). Les performances d'adsorption statique sur le MOF-BA-1.0 du rébaudioside A (RA) et du stévioside (STV) dans une solution de sucre brut (5,0 mg [mL.sup.-1], pH 8) ont été évaluées à 303 K pendant 15 h. Les résultats ont montré que la capacité d'adsorption du STV et du RA était respectivement de 42,93 mg [g.sup.-1] et de 22,96 mg [g.sup.-1], et que la sélectivité d'adsorption ([[alpha].sub.STV/RA]) atteignait 4,35. L'isotherme d'adsorption et les données cinétiques du MOF-BA-1.0 pour l'adsorption du RA et du STV obéissaient au modèle de l'isotherme de Langmuir et au modèle cinétique de pseudo-second ordre, respectivement. L'étude a permis de montrer que le MOF-BA-1.0 pouvait éventuellement servir d'adsorbant pour purifier les ingrédients actifs du stévia et obtenir une concentration élevée de RA. [Traduit par la Rédaction] Mots-clés: réseau métallo-organique fonctionnalisé par un acide boronique (MOF-BA), séparation, stévioside, rébaudioside A., Introduction Steviol glycosides (SGs) extracted from Stevia rebaudiana Bertoni leaves are a high-quality natural sweetener and dietary supplement. (1,2) Owing to their high sweetness (250-450 times sweeter than sugar), zero [...]

Thermal lens spectrometry in a coaxial configuration is used for the direct determination of adsorbates on a planar surface of polyethylene terephthalate (PET). A possibility of the direct measurement of the rate of adsorption from solutions and the determination of the parameters of the adsorbed layer is demonstrated by the example of an investigation of the adsorption of iron(II) tris(1,10-phenantrolinate) on a PET surface. The adsorption isotherm of iron(II) tris(1,10-phenantrolinate) on the PET surface is described by the Langmuir equation and is linear in the concentration range in solution from 0.02 to 0.7 mM. The method for calculating the thermal perturbation in surface-absorbing solids was used to interpret the results of the adsorption study, and a possibility of determining iron(II) tris(1,10-phenantrolinate) on the surface at a level smaller than a monolayer was shown. Thermal lens spectrometry enables the determination of the absorption of the surface layer at a level up to 5 x [10.sup.-5] absorbance units, which corresponds to the surface concentration of iron(II) tris(1,10-phenanthrolinate) 2 x [10.sup.-13] mol/[cm.sup.2]. Using the example of the adsorption of 4-(2-pyridylazo)resorcinol on the PET surface, it is demonstrated that, in the case of strong absorption of the surface layer, the thermal destruction of substance and the deformation of the substrate may occur. A local increase in temperature in the layer is also confirmed by theoretical calculations. Keywords: thermal lens spectrometry, spectrophotometry, Thermal lens spectrometry (TLS) enables the measurement of the absorption of solid samples at the levels unattainable in spectrophotometry [1-5], including samples with surface absorption [6-9]. However, the methodology of [...]

Thermal lens spectrometry was used to study Langmuir--Blodgett films of a weakly absorbing Nafion polyelectrolyte membrane on the surface of inert polyethylene terephthalate (PET) and glass substrates and to estimate the amount of Nafion (number of layers) using a change in the thermal characteristics of the sample. The sensitivity of thermal lens measurements at the wavelength of the exciting radiation 532.0 nm is comparable to that of solid-state spectrophotometry in the region of the maximum absorbance of Nafion (275 nm). However, the high locality of thermal lens spectrometry (the area of the signal generation zone is 100 [micro][m.sup.2]) ensures the estimation of the uniformity of the deposition of the polyelectrolyte layer. To increase the absorbance of the layer of the applied polyelectrolyte, the latter is saturated with a colored compound (ferroin). The adsorption of ferroin into the Nafion layer on the PET surface was confirmed; the absorbance of ferroin in the Nafion layer is in the range of 1 x [10.sup.-5] - 5 x units of absorbance, which corresponds to the surface concentration of ferroin 1 x [10.sup.-11] - 4 x [10.sup.-10] mol/[cm.sup.2]. Keywords: thermal lens spectrometry, Nafion, Langmuir-Blodgett films, solid- phase spectrophotometry DOI: 10.1134/S1061934818060102, The development of analytical methods based on the use of reagents of various classes in combination with absorption spectroscopy techniques provides analytical chemists with a wide range of options for [...]

In this study, the adsorption behaviors of methanol, methanal, toluene, ethylbenzene, and styrene molecules in FAU, FER, CON, and MWW zeolites were investigated. The adsorption isotherms of the five adsorbates in the four zeolites at 298 and 350 K were simulated using grand canonical Monte Carlo simulations. Moreover, binary component adsorptions were considered. The results revealed that the saturated adsorption capacity ofsingle components in different zeolites decreased in the order of FAU > MWW > CON > FER, and the adsorption capacity of the five adsorbates in the same zeolite decreased in the order of methanal > methanol > toluene > styrene > ethylbenzene. The equilibrium adsorption capacity slightly decreased with increasing temperature. In terms of binary component adsorption, intense competition existed between the smaller adsorbed molecules. As the differences among the molecular structures increased, the competition in adsorption became more intense. Key words: zeolite, adsorption, grand canonical Monte Carlo simulation, adsorption isotherm, molecular simulation. Dans le cadre des present travaux, nous avons etudie le comportement d'adsorption des molecules de methanol, de methanal, de toluene, d'ethylbenzene et de styrene sur des zeolites de structure FAU, FER, CON et MWW. Nous avons simule les isothermes d'adsorption des cinq adsorbats sur les quatre zeolites a 298 K et a 350 K en utilisant la methode Monte-Carlo dans l'ensemble grand canonique. En outre, nous avons etudie le cas des adsorptions de composantes binaires. En ce qui concerne les composantes uniques, les resultats ont revele que la capacite de saturation de leur adsorption sur differentes zeolites diminuait selon l'ordre FAU > MWW > CON > FER et que la capacite d'adsorption des cinq adsorbats sur une meme zeolite diminuait selon l'ordre methanal > methanol > toluene > styrene > ethylbenzene. La capacite d'adsorption a l'equilibre diminuait legerement en fonction de l'augmentation de la temperature. En ce qui concerne l'adsorption de composantes binaires, la competition pour l'adsorption etait plus forte entre les molecules de plus petite taille. A mesure que la difference entre les structures moleculaires augmentait, la competition pour l'adsorption s'intensifiait. [Traduit par la Redaction] Mots-cles: zeolite, adsorption, simulation de Monte-Carlo dans l'ensemble grand canonique, isotherme d'adsorption, simulation moleculaire., Introduction Styrene is an important monomer that is industrially applied for the synthesis of plastics and rubbers. (1) It is traditionally synthesized from benzene and ethylene, which is a complicated [...]

The review is devoted to the consideration of adsorption preconcentration of synthetic anionic food dyes for their subsequent determination in various samples. The main classes of adsorbents and their features, conditions for extraction and desorption of the compounds to be determined in batch and dynamic modes, characteristics of procedures using adsorption preconcentration, and examples of their application to the determination of dyes in various food products are given. Keywords: synthetic dyes, adsorption preconcentration, determination, adsorbents, food products, Synthetic organic dyes are widely used in the food industry to impart color to products, such as alcoholic and nonalcoholic beverages, sweets, and confectionery and also in the production of [...]

Abstract: The adsorption of ferroin by graphite oxide was studied by changing different parameters, i.e., pH, duration, concentration of ferroin, adsorbent dose, and temperature. The removal of ferroin in aqueous [...]

The adsorption and heat-energy-aid desorption of methylene blue (MB) on a thermo-sensitive adsorbent of methyl cellulose/calcium alginate beads (MC/CABs) has been studied. The addition of methyl cellulose intensified the desorption ability of adsorbent, and boosted the difference of adsorption capacity of adsorbent between low temperature and high temperature. At the mass ratio of methyl cellulose to sodium alginate of 2:1, the difference of adsorption capacity of MC/CABs between 20 and 60°C reached 20.48 mg [g.sup.-1]. The effects of temperature, time and initial MB concentration on adsorption performance were investigated in detail. The MB adsorption on MC/ CABs followed the pseudo-second-order kinetic model. The equilibrium data was fitted well with Langmuir isotherm. The maximum adsorption capacity of 336.70 mg [g.sup.-1] exhibited MC/CABs had a good adsorption capability. Thermodynamic analyses showed high temperature was not favorable to MB adsorption, and MC/CABs had a distinct superiority in desorption of adsorbate with heat-energy-aid. Lastly, the possible mechanisms involving in adsorption and heat-energy-aid desorption were presented., INTRODUCTION Cationic dyes known as basic dyes are extensively used in dyeing of textile fibers such as cotton and polyester [1]. The complex aromatic molecular structures and xenobiotic properties of [...]

The adsorption of oxygen ([O.sub.2]) and chlorine ([Cl.sub.2]) on pristine and impurity X atom (X = C, Al, Si, Ca, Mn, Fe, Co, Ni, Cu or Ge) doped (10,0) and (6,6) boron nitride nanotubes (BNNTs) has been theoretically studied using first-principles approach based on density functional theory. Comparing with the formation energy, the distance between gas molecule and X atoms, the Bader charge transfer, and the elevation of the dopant atom, we find that the [O.sub.2] or [Cl.sub.2] molecule undergoes weakly physical adsorption on the pristine (10,0) and (6,6) BNNTs, and the Al, Si, and Mn atoms are suitable dopants to modify BNNTs to enhance the reactivity of the tube to gas molecules. This work reveals that the sensitivity of BNNT-based chemical gas sensors for [O.sub.2] and [Cl.sub.2] can be drastically improved by introducing appropriate dopant, and Al-, Si-, and Mn-doped BNNTs can be used as [O.sub.2] and [Cl.sub.2] gas sensor manufacturing raw materials. Key words: oxygen molecule, chlorine molecule, boron nitride nanotube, molecule sensor, first principles. Nous utilisons une approche de principes premiers, basee sur la theorie de la fonctionnelle de densite, pour calculer l'adsorption de l'oxygene ([O.sub.2]) et du chlore ([Cl.sub.2]) sur des nanotubes de nitrure de bore (10,0) et (6,6) (BNNTs) qui sont, soit parfaits, soit dopes par impurete atomique X (X = C, Al, Si, Ca, Mn, Fe, Co, Ni, Cu ou Ge). Comparant avec l'energie de formation, la distance entre les molecules de gaz et les atomes X, le transfert de charge de Bader et l'elevation/profondeur des atomes dopants, nous trouvons que les molecules [O.sub.2] et [Cl.sub.2] sont sujettes aune faible adsorption sur les BNNTs parfaits (10,0) et (6,6), alors que les atomes Al, Si et Mn sont des dopants appropries pour modifier les BNNTs et augmenter la reactivite du tube aux molecules de gaz. Ce travail indique que la sensibilite aux gaz [O.sub.2] et [Cl.sub.2] des detecteurs de gaz chimiques bases sur des BNNTs peuvent etre sensiblement ameliores en introduisant les dopants appropries et que les BNNTs dopes a Al, Si et Mn peuvent etre utilises pour la detection a l'echelle industrielle de [O.sub.2] et de [Cl.sub.2]. [Traduit par la Redaction] Mots-cles : molecule d'oxygene, molecule de chlore, nitrure de bore, detecteur de molecules, principes premiers., 1. Introduction Boron nitride nanotubes (BNNTs) are a broad band gap semiconductor with unique physicochemical properties, such as heat resistance, relative chemical inertness, and uniformity of electronic properties, and thus [...]

A method of the selective removal of certain anions from the eluate in an ion chromatographic experiment (the adsorption column method) is proposed for the qualitative and quantitative determination of the removed anions and/or coeluted unadsorbed sample components. The method is suitable for some complex cases of anion analysis ([F.sup.-]/I[O.sup.-.sub.3], [Cl.sup.-]/N[O.sup.-]) using a METROHM ion chromatograph. Keywords: ion chromatography, selective anion analysis, The reversible transfer of part of capacity of an cation exchanger in a suppression column to a special salt form ensures the selective removal of individual anions from the eluate [...]

Using the noncovalent immobilization of some thiacalix[4]arene derivatives on the surface of silanized silica, we obtained efficient adsorption materials for the extraction of Eu(III) ions from aqueous solutions of medium mineralization. The specific surface area of the adsorbents is 200-370 [m.sup.2]/g. It is shown that adsorbents containing thiacalix[4]arenes with phosphoryl groups selectively extract up to 99% of europium ions from aqueous solutions at pH 5.5-6; they are characterized by adsorption capacity of 7.5-14.5 mg/g and high distribution coefficients. The studied adsorbents exhibit high selectivity with respect to Eu(III) ions, wherein the distribution coefficients for Cs, Sr, Tb(III), Sm(III), Gd(III), La(III), and U[O.sup.2+.sub.2] are five times or more smaller. Keywords: adsorption, silica, thiacalix[4]arene, modified adsorbents, Eu(III) DOI: 10.1134/S1061934816050063, Calix[n]arenes are universal molecular platforms having great potential for modification. The unique structure of the macrocycle enables the construction of specific receptors capable of recognizing with high selectivity the substrates [...]

We consider the use of adsorption and extraction as methods of preconcentration increasing the sensitivity and selectivity of the determination of elements and organic substances in solutions, in flow-through analytical systems. Various applications of these methods in flow-through systems are reviewed; the peculiarities of a combination of preconcentration and determination are discussed; and examples of hybrid assay systems are given. Keywords: adsorption, extraction, flow-through analytical systems, determination of organic and inorganic substances DOI: 10.1134/S1061934815110167, Preconcentration of trace components (elements and organic substances) is used in flow-through analysis primarily in the cases where the sensitivity of direct determination is insufficient. Furthermore, because of the insufficient [...]

Graphene is a newly discovered material and is considered to be the new wonder material for many applications. The recent possibility of obtaining pure and fully characterized graphene opens the door to the study of the adsorption of toxic materials on graphene. The adsorption behavior of p-nitrophenol on graphene was studied in aqueous medium. The effect of each of pH, temperature, and dosage was emphasized. The highest calculated adsorption capacity of 4-nitrophenol was found to be 15.5 mg/g, assuming Langmuir fitting starting from 11.1 mg/g initial concentration at 298 K and pH = 6. Fitting the data using the Freundlich isotherm model predicted a favorable adsorption process (n > 1). The rise and saturation areas of the isotherms were fitted as pseudo first-order and pseudo second-order processes, respectively, with relatively good fit ([k.sub.1] = 0.0023/s, [k.sub.2] = 0.68 g [mg.sup.-1] [s.sup.-1]). The thermodynamic properties indicated a spontaneous and exothermic process. Key words: p-nitrophenol, adsorption, graphene, kinetics, thermodynamics. Resume : Le graphene est un materiau recemment decouvert et percu comme la nouvelle merveille pour une multitude d'applications dans le domaine des materiaux. La recente possibilite d'obtenir du graphene pur et entierement caracterise ouvre la voie a l'etude de l'adsorption de substances toxiques sur du graphene. Nous avons etudie les caracteristiques d'adsorption du p-nitrophenol sur le graphene en milieu aqueux. Nous avons mis l'accent sur les effets de chacun des parametres suivants: le pH, la temperature et la concentration. Nous avons calcule que la capacite d'adsorption maximale du 4-nitrophenol etait de 15,5 mg/g, en considerant un ajustement de Langmuir a partir d'une concentration initiale de 11,1 mg/g a 298 K et a pH = 6. L'ajustement des donnees a l'aide du modele isotherme de Freundlich a permis de predire un processus d'adsorption favorable (n > 1). Les surfaces d'elevation et de saturation des isothermes ont ete ajustees selon des cinetiques de pseudo premier ordre et de second ordre, respectivement, avec une correspondance relativement etroite ([k.sub.1] = 0,0023/s, [k.sub.2] = 0,68 g [mg.sup.-1] [s.sup.-1]). Les proprietes thermodynamiques indiquaient un processus spontane et exothermique. [Traduit par la Redaction] Mots-cles: p-nitrophenol, adsorption, graphene, cinetique, thermodynamique., Introduction Graphene is considered to be the strongest, most conductive, and thinnest material on earth. (1) The sp2 carbon atoms are bonded to each other on six-membered rings to form [...]

The adsorption of Sunset Yfellow FCF food dye (Orange Yellow S, E-110) from aqueous solutions on silica adsorbents modified by alkyl groups and on γ-[Al.sub.2][O.sub.3] is studied. The adsorption attains a maximum in the range 1 M HCl-pH 1 on Diasorb-130-C16 (79-87%), 0.5 M HCl-pH 6.8 on Diasorb-130-C16 and Diasorb-100-C8 in the presence of trimethylammonium bromide (92-98%), and pH 1-5.6 on γ-[Al.sub.2][O.sub.3] (72- 87%). Calibration graphs of the dependence of the Kubelka-Munk function F on the dye concentration in aqueous solutions are built. The possibility of the preconcentration of trace amounts of the dye from large volumes of solutions is shown. A method of dye determination is proposed based on its separation by adsorption followed by determination by diffuse reflectance spectroscopy directly in the adsorbent phase and used in the analysis of the O! Orange drink. The accuracy of the determination is verified by comparison with the results obtained by the GOST P 52470-2005 procedure. Keywords: Sunset Yellow FCF (Orange Yellow S), alumina, Diasorb-130-C16, Diasorb-100-C8, adsorption, diffuse reflectance spectroscopy DOI: 10.1134/S1061934815060131, The appearance and color of products are features by which users can judge about the quality of a product. Natural dyes are unstable and can easily decompose under the conditions [...]

In the present work, graphite nanostructures are prepared by thermolysis of a prepared polyacrylamide gel. The gel was prepared by radical chain polymerization and the synthesis of the nanostructures was done by step annealing at different temperatures. The structural of the prepared materials was studied by X-ray diffraction (XRD). The presence of carboxylic and phenolic functional groups on the graphite surface was confirmed by FT-IR analysis. Batch adsorption experiments were conducted to study the effect of equilibration time, initial metal cation concentration, and solution pH for the removal of Cs(I) and Co(II) from aqueous solutions. Kinetic data of Cs(I) adsorption was found to be well fitted with a pseudo-first-order kinetic model. The obtained isotherm data were correlated with the Langumir and Freundlich isotherm models. The effect of temperature on the equilibrium distribution values was utilized to evaluate the change in the standard thermodynamic quantities of enthalpy ([DELTA][H.sup.o]), entropy ([DELTA][S.sup.o]), and Gibbs free energy ([DELTA][G.sup.o]). Key words: adsorption, Cs(I), Co(II), graphite, aqueous solution. Dans ce travail, on a prepare des nanostructures de graphite par thermolyse d'une preparation de gel de polyacrylamide. Le gel a ete prepare par la technique de la polymerisation radicalaire en chaine alors que la synthese des nanostructures a ete realisee par la technique de recuisson a diverses temperatures. Les caracteristiques structurales des materiaux obtenus ont ete etudiees par diffraction des rayons-X (DRX). La presence des groupes fonctionnels carboxyliques et phenoliques sur la surface de graphite a ete confirmee par analyse infrarouge par transformation de Fourier (IR-TF). On a fait appel a des experiences d' adsorption globale pour etudier l' effet du temps d' equilibre, de la concentration initiale du cation metallique et du pH de la solution pour l'elimination des ions Cs(I) et Co(II) a partir de solutions aqueuses. On a trouve que les donnees cinetiques d'adsorption du Cs(I) s'ajustent bien avec un modele cinetique de pseudo-premier ordre. On a pu etablir une correlation entre les donnees d' isothermes et les modeles isothermes de Langmuir et Freundlich. On a utilise l' effet de la temperature sur les valeurs de distribution d'equilibre pour evaluer le changement des quantites thermodynamiques standard d'enthalpie ([DELTA][H.sup.o]), d'entropie ([DELTA][S.sup.o]) et l'energie libre de Gibbs ([DELTA][G.sup.o]). Mots-cles : adsorption, Cs(I), Co(II), graphite, solution aqueuse. [Traduit par la Redaction], Introduction The toxicity and the biological effects of hazardous materials, which are dangerous to public health and the environment, are attracting progressively more attention. The most hazardous pollutants identified in [...]

A metal-clad waveguide (MCWG) sensor comprised of a nanoporous waveguiding layer on a metal cladding layer is advantageous in sensing of biomolecules because of a high surface area of nanopores and a sharp dip in the reflection spectrum due to characteristics of the MCWG mode. Here, a porous anodic alumina (PAA)/aluminum (Al) film was fabricated on a glass substrate as a MCWG sensor with the Kretschmann geometry, and the sensor response was examined for both colorless bovine serum 'albumin (BSA) and colored metal complexes by measurements of reflection spectra and Fresnel calculations. The BSA adsorption on the PAA layer induced a parallel redshift of the waveguide coupling dip in the reflection spectrum. The experimental results were well simulated by the five-phase Fresnel calculations which indicated that the redshift of the dip was linearly dependent on the adsorbed amount of BSA. When the response of a MCWG sensor with a PAA layer was compared with that of a MCWG sensor with a nonporous alumina layer, the former showed larger redshift than the latter, due to a large adsorbed amount of BSA in the PAA layer with high surface area. For the adsorption of colored Ru[[[Bphen.sub.3]].sup.2+] and Fe[[[Phen.sub.3]].sup.2+], the effect of both the real and imaginary parts of the complex refractive index on the sensor response was examined. As a result, a redshift of the waveguide coupling dip was observed for both metal complexes irrespective of the wavelength region examined; tiffs could be ascribed to the changes in the real part of the refractive index due to the adsorption of metal complexes on the PAA layer. Meanwhile, an increase in the reflectivity was observed when the coupling wavelength was close to that of the absorption 'bands of the metal complexes; this could be ascribed to the changes in the imaginary part of the refractive index of the PAA layer. Using the sensor response caused by the changes in the imaginary part, absorption spectral profiles of metal complexes could be reproduced. 10.1021/ac100654b

Ion-interaction chromatography utilizes the addition of amphiphilic (surfactant) molecules to the mobile-phase solution in order to bring about the retention and separation of hydrophilic ionic analytes on reversed-phase liquid chromatographic stationary phases. The mechanism by which retention and separation in ion-interaction chromatagraphy is accomplished remains unclear, although two primary mechanisms of this phenomenon have been proposed: preadsorption of the hydrophobic counterions to the hydrophobic stationary phase followed by interaction with the ionic analyte or adsorption of ion-paired species to the hydmphobic surface. There is evidence that both mechanisms contribute to ionic retention and separations. In this work, ion interactions at a [C.sub.18] stationary-phase interface are investigated by confocal Raman microscopy of individual stationary-phase particles, which is capable of quantifying surface concentrations of surfactants and model solutes. Raman spectra taken within the interior of the particle indicate that preadsorption of the hydrophobic surfactant cetylpyridinium to the stationary-phase interface is sensitive to ionic strength and concentration of organic modifier in the mobile phase. It was also determined that the presence of low concentrations of a model, ionic solute, nitrobenzenesulfonate, leads to greater adsorption of cetylpyridinium ion at the hydrophobic interface. As the concentration of nitrobenzenesulfonate is increased, the 1:1 increase in the cetylpyridinium ion interfacial concentration provides evidence of ion pairs forming at the stationary-phase surface. 10.1021/ac100781p

The quartz crystal microbalance (QCM) has become a popular method to study the formation of surface-confined films that consist of discrete biomolecular objects--such as proteins, phospholipid vesicles, virus particles--in liquids. The quantitative interpretation of QCM data-frequency and bandwidth (or, equivalently, dissipation) shifts--obtained with such films is limited by the lack of understanding of the energy dissipation mechanisms that operate in these films as they are sheared at megahertz frequencies during the QCM experiment. Here, we investigate dissipation mechanisms in such films experimentally and by finite-element method (FEM) calculations. Experimentally, we study the adsorption of globular proteins and virus particles to surfaces with various attachment geometries: direct adsorption to the surface, attachment via multiple anchors, or attachment via a single anchor. We find that the extent of dissipation caused by the film and the evolution of dissipation as a function of surface coverage is not dependent on the internal properties of these particles but rather on the geometry of their attachment to the surface. FEM calculations reproduce the experimentally observed behavior of the dissipation. In particular, a transient maximum in dissipation that is observed experimentally is reproduced by the FEM calculations, provided that the contact zone between the sphere and the surface is narrow and sufficiently soft. Both a small-angle rotation of the sphere in the flow field of the background fluid (rocking) and a small-amplitude slippage (sliding) contribute to the dissipation. At high coverage, lateral hydrodynamic interactions between neighboring spheres counteract these modes of dissipation, which results in a maximum in dissipation at intermediate adsorption times. These results highlight that, in many scenarios of biomolecular adsorption, the dissipation is not primarily determined by the adsorbate itself, but rather by the link by which it is bound to the substrate.

Recent experimental and theoretical results have firmly established the existence of enhanced concentrations of selected ions at the air/water interface. Ion adsorption to aqueous interfaces involving complex organic molecules is relevant to biology in connection with the familiar but incompletely understood Hofmeister effects. Here, we describe resonant UV second harmonic generation (SHG) studies of the strongly chaotropic thiocyanate ion adsorbed to the interface formed by water and a monolayer of dodecanol, wherein the Gibbs free energy of adsorption was determined to be -6.7 [+ or -] 1.1 and -6.3 [+ or -] 1.8 kJ/mol for sodium and potassium thiocyanate, respectively, coincident with the value determined for thiocyanate at the air/water interface. Interestingly, near 4 M and higher concentrations, the resonant SHG signal increases discontinuously, indicating a structural change in the interfacial region. buried interface | Langmuir model | nonlinear optics | self-assembled monolayer | surface spectroscopy

Problem statement: The aim of this study was to investigate the removal of methyl red, a mutagenic monoazo dye, from various aqueous solutions using banana pseudostem fibers of the size 212-350 micron. Approach: The parameters studied were the effect of pH, amount of adsorbent, contact time, concentration of adsorbate and agitation speed. Results: Equilibrium data were fitted to the Langmuir and Freundlich isotherm models. The data were best represented by the latter with an adsorption capacity and adsorption intensity of 0.351 and 0.302, respectively. Conclusion/Recommendations: Specific rate constants of the processes were calculated by kinetic measurements and a pseudo second order adsorption kinetics was obtained for all cases. Key words: Sorption, methyl red, biotransformation, mutagenic, banana pseudostem fibers, INTRODUCTION Rapid progress in industrial activities during recent years has led to the discharge of unprecedented amount of wastewater containing synthetic dyes, which pollutes the rivers and consequently causes harm [...]

Problem statement: Further study is recommended to improve the immobilization technique and the immobilized lipase's performance as catalysis in transesterification reaction. Approach: To investigate the ability of immobilized lipase on chitosan beads to catalyze the transesterification of cooking oil to an ester. The porous bead of chitosan was used for immobilization of lipase from Candida rugosa by physical adsorption. Parameters like reaction time and oil to methanol molar ratios were studied to compare the transesterification performance between free lipase and immobilized lipase. Results: The experimental result showed that the maximum conversion of ester using immobilized lipase and free lipase were 72.25 and 76.5% respectively which was obtained at conditions of 1:4 molar ratios and reaction time of 48 h. Conclusion: Even though the conversion of ester was higher in free lipase than in immobilized lipase, it is still feasible to use immobilized lipase to catalyze the transesterification process provided it's easier to separate the end product and high potential to be reused. Immobilize lipase also tolerated the water content of oil and increases product yield by avoiding the soap formation. Key words: Immobilization of lipase, physical adsorption, chitosan beads, transesterification, ester, INTRODUCTION Many efforts have been made over the years to develop the catalytic activity and operational stability of industrial enzymes through the use of genetic engineering, immobilization and/or process alterations. [...]

Charge states of atoms can be investigated with scanning tunneling microscopy, but this method requires a conducting substrate. We investigated the charge-switching of individual adsorbed gold and silver atoms (adatoms) on ultrathin NaCl films on Cu(111) using a qPlus tuning fork atomic force microscope (AFM) operated at 5 kelvin with oscillation amplitudes in the subangstrom regime. Charging of a gold atom by one electron charge increases the force on the AFM tip by a few piconewtons. Moreover, the local contact potential difference is shifted depending on the sign of the charge and allows the discrimination of positively charged, neutral, and negatively charged atoms. The combination of single-electron charge sensitivity and atomic lateral resolution should foster investigations of molecular electronics, photonics, catalysis, and solar photoconversion.

The nonspecific adsorption of charged nanoparticles onto single-component phospholipid bilayers bearing phosphocholine head-groups is shown, from fluorescence and calorimetry experiments, to cause surface reconstruction at the points where nanoparticles adsorb. Nanoparticles of negative charge induce local gelation in otherwise fluid bilayers; nanoparticles of positive charge induce otherwise gelled membranes to fluidize locally. Through this mechanism, the phase state deviates from the nominal phase transition temperature by tens of degrees. This work generalizes the notions of environmentally induced surface reconstruction, prominent in metals and semiconductors. Bearing in mind that chemical composition in these single-component lipid bilayers is the same everywhere, this offers a mechanism to generate patchy functional properties in phospholipid membranes. fluorescence | adsorption | phase transition

The phosphoric acid activated carbon (PAC) was derived from waste wooden pallets by a two-step chemical activation technique, carbonization and phosphoric acid activation in sequence. A widely used commercial activated carbon, Calgon Filtrasorb 400 (F400), was studied in parallel for comparison. The physical properties and surface chemistry of the activated carbons were characterized using BET-[N.sub.2] adsorption, elemental analysis, Boehm's titration, Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy. PAC possessed physical properties (surface area and pore volume) that were comparable to those of F400, but displayed distinct surface chemistry in terms of [pH.sub.PZC] surface acidity and basicity, and surface functional groups. Batch studies were conducted to evaluate the methylene blue (MB) and phenol adsorption capacity of PAC and F400 and their dependence on pH, contact time, and initial adsorbate concentration. Experimental results showed that the solution pH slightly influenced the adsorption of MB and phenol on F400, whereas it had no effect on their adsorption on PAC. Equilibrium adsorption data were fitted with an Langmuir isotherm equation. In comparison with F400, PAC showed a higher adsorption capacity for MB but lower for phenol. Given the comparable physical properties of PAC and F400 and the polar nature of MB and phenol, surface chemistry of the two carbons appeared to determine the adsorption mechanism and capacity. The strongly negative surface of PAC, due to phosphoric acid activation, facilitated the adsorption of positively charged MB, whereas the presence of oxygen-containing functional groups on PAC inhibited phenol adsorption. DOI: 10.106l/(ASCE)0733-9372(2008)134:5(338) CE Database subject headings: Adsorption; Wood; Activated carbon; Phenol.

The rapid small-scale column test (RSSCT) has become a popular method for sizing granulated activated carbon (GAC) systems and columns for water treatment facilities. In this procedure, the GAC is ground and a specific size fraction is used for the RSSCT. Since GAC is produced and activated using different processes from different starting materials (e.g., bituminous, lignite, wood, etc.), the possibility exists that the extent of activation and, hence, the adsorptive capacity and surface reactivity may vary throughout the GAC particles. This would be the case if there were less activated inner cores in the GAC particles. If there is a variation in the sorption properties throughout the GAC particles, then grinding the GAC may result in smaller particles that have different properties than the bulk GAC. This study was carried out to test this commonly assumed hypothesis that the limited-sized ground particles represent the same adsorptive properties as the bulk GAC. Four activated carbons (manufactured from different source carbons) were studied. Gas adsorption tests determined the physical morphology, Boehm's titrations checked the chemical nature of the surface oxides, and the Mohs hardness test was performed on all bulk GACs and ground fractions. No apparent differences were found in the total surface area, cumulative pore volume, or pore size volume of fractions generated by grinding activated carbons. In addition, the Boehm technique did not identify any significant differences in the chemical nature of the surfaces of the various size fractions of GAC. The Mohs hardness test did not indicate any variations in the hardness of the bulk GAC, the ground fractions, and the unground core. Based on the methods and materials used, the underlying assumption in the RSSCT analysis--that there are no variations in the different size fractions of the ground GAC--appears to be correct. DOI: 10.1061/(ASCE)0733-9372(2008)134:3(216) CE Database subject headings: Activated carbon; Columns; Water treatment plants; Adsorption.

Biodegradability of chlorinated aliphatic (carbon tetrachloride) and aromatic (chlorophenol) compounds under acidogenic condition was investigated at pH of 5.0 to 5.5. Batch tests were used to evaluate biodegradability, adsorption capacity, and inhibitory effects of the chlorinated compounds on the fermentative microbial consortium. The biodegradability of carbon tetrachloride differed from that of the chlorophenols tested. Carbon tetrachloride was degraded to dichloromethane, and its adsorption onto the biomass was minimal. Inhibition of the acidogenic process was not observed for carbon tetrachloride at 10 mg/L. Chlorophenols (penta, tri, di, and mono) were not degraded at all, even after addition of vitamin supplements, increased incubation time, and increased primary to secondary substrate ratio. Chlorophenol removed from the aqueous phase by adsorption can be recovered from the acidogenic sludge. Pentachlorophenol was inhibitory to the acidogenic culture, whereas 2-chlorophenol was not. Microbial community analysis revealed the bacteria therein were primarily rumen and enteric bacteria. The results showed that it is possible to dechlorinate at least an aliphatic chlorinated compound under acidogenic conditions. DOI: 10.1061/(ASCE)0733-9372(2008)134:3(177) CE Database subject headings: Adsorption; Degradation; Chlorination.

Endosulfan, one of the most widely used pesticides in various sectors including agriculture, has been reported posing a threat to the ecology as well as to the environment. Contamination of groundwater and surface water sources with various pesticides is well documented, and this problem is prominent, particularly in rural areas. In the present study, efforts are made to remove endosulfan from water using wood charcoal, a local and low cost adsorbent. It gave removal efficiency of more than 90%. Equilibrium time was found to be around 5 h. Wood charcoal showed an uptake capacity of 0.53 mg/g with initial endosulfan concentration in the range of 0.25-5 mg/L and 1.77 mg/g for the range of 2-50 mg/L. Langmuir isotherm gave a better prediction of adsorption capacity than the Freundlich. The Langmuir isotherm fit also gave a better correlation with the experimental data. In the desorption study carried out, 10% solutions of acetone, methanol, acetic acid, saturated EDTA solution, and distilled water were used as eluents. Ten percent methanol solution was found performing well with an adsorbent regeneration of more than 80% after four cycles of adsorption desorption. Desorption was found to follow a zero order equation in the case of 10% solutions of both acetone and methanol. DOI: 10.1061/(ASCE)0733-9372(2008)134:2(102) CE Database subject headings: Adsorption; Desorption; Equilibrium; Abatement and removal; Ecology; Pesticides; Water pollution.

Electrokinetic remediation technology is one of the developing technologies that offers great promise for the cleanup of soils contaminated with heavy metals. However, the performance of an electrokinetic remediation system depends on the interaction of a complex set of interrelated system variables and parameters. Many of these interactions were addressed in this study by incorporating geochemical reactions into electrokinetic remediation modeling. A one-dimensional transport model was developed to predict the transport and speciation of heavy metals (chromium, nickel, and cadmium) in soil during electrokinetic remediation as a function of time and space. The model incorporates: (1) pH-dependent adsorption of contaminants to the soil surface; (2) sensitivity of soil surface potential and electroosmotic flow to the pore water properties; and (3) synergistic effects of multiple chemical species on electrokinetic remediation. The model considers that: (1) Electrical potential in the soil is constant with time; (2) surface complexation reactions are applicable in the highly concentrated clay suspensions; (3) the effect of temperature is negligible; and (4) dissolution of soil constituents is negligible. The predicted pH profiles, electroosmotic flow, and transport of chromium, nickel, and cadmium in kaolin soil during electrokinetic remediation were found to reasonably agree with the bench-scale electrokinetic experimental results. The predicted contaminant speciation and distribution (aqueous, adsorbed, and precipitated) allow for an understanding of the transport processes and chemical reactions that control electrokinetic remediation. DOI: 10.1061/(ASCE)1090-0241(2008)134:1(91) CE Database subject headings: Electrokinetics; pH; Heavy metals; Kaolin; Adsorption; Remedial action.

Analytical technique using organic resins has already been well-developed, and its applications are employed in various fields; nevertheless, the chemical phenomena occurring inside the resin remain unclear for the most part. In the present study, we apply EXAFS spectroscopy to elucidate the adsorption and separation phenomena of metal ions by organic resin. That is, the chemical species of trivalent lanthanides (Ln(III)) adsorbed in a tertiary pyridine resin from hydrochloric acid and nitric acid solutions have been determined by EXAFS. The results in HCl solutions suggest that Ln(III) ions are partly dehydrated in the resin phase, enabling the pyridine groups of the resin and chloride ions to coordinate to the Ln(III) ions in their primary coordination sphere. On the other hand, Ln(III) ions are tightly coordinated by several nitrate ions in HN[O.sub.3] solutions and they keep forming the nitrate complex even in the resin phase. The lighter Ln of Nd tends to form an anionic nitrate complex, [[Nd[(N[O.sub.3]).sub.4]*n[H.sub.2]O].sup.-], in the resin phase, while the middle Ln of Sm exists as a cationic nitrate complex, [[Sm[(N[O.sub.3]).sub.2]*n[H.sub.2]O].sup.+], for the most part. On the basis of these EXAFS results, the adsorption and separation mechanisms of the pyridine resin in HCl solutions are interpreted as the direct coordination of pyridine groups to metal ions, while the mechanisms in HN[O.sub.3] solutions are mainly dominated by the anion-exchange reaction between the protonated pyridine groups and the anionic nitrate complexes of Ln(III). The obtained results demonstrate that the hydration of metal ions weakens, and instead, other complexations are enhanced in the resin phase.

The adsorption potential of the kaolinite clay for the removal of lead ions from aqueous solutions was tested. The measured adsorption isotherms at the different temperatures 298.15 K, 308.15 K and 318.15 K were found to be perfectly fit to the Langmuir isotherm equation. A high adsorption capacity was calculated. An increase in the retention capacity with increasing temperature was measured. The adsorption process was found to be endothermic with an estimated mean enthalpy change of 135.2 kJ/mol. The measured adsorption kinetic data at different temperatures proved that not only intraparticle diffusion controls the adsorption process but also surface adsorption contributes to the control of rate of adsorption. The influence of pH in the acidic range was investigated. The measured increase in the adsorption rate at higher pH values (4.9) was explained through the influence of [H.sup.+] ions on the complex ion formation. Key words: Adsorption, Kaolinite, Clay, Lead, Aqueous Solution, pH, INTRODUCTION Contamination of water with lead heavy metal ions is a large environmental concern associated with the increasing of industrial processes which discharge aqueous effluents containing lead ions. Lead ions [...]

The adsorption equilibria of methanol from diluted solutions of the alcohol in dichloromethane (the weak solvent of the binary mixture) have been investigated in normal-phase conditions on an hybrid polymeric chiral stationary phase. This was done by analyzing the shapes of nonlinear perturbations of methanol, measured with a refractive index detector from a column in equilibrium with pure dichloromethane. Experiments have been set up to demonstrate the displacement effect, predictable from the adsorption data, by a nonlinear pulse of methanol on a racemic mixture of temazepam injected at trace level. A most used method in fundamental studies of band behavior in chromatography has been used for modeling the system. An extraordinary increase of the apparent column efficiency has been observed due to the displacement phenomenon, with the peak of the second eluted enantiomer noticeably higher and narrower than that of the first eluted component.

Electrochemical oxidation of 2'-deoxyguanosine has been performed on boron-doped diamond (BDD) electrodes, resulting in a strong adsorption of the formed oxidized products onto the BDD surface. The adsorption behavior has been investigated by studying the electrochemical behavior of a redox probe ([[Ir[Cl.sub.6]].sup.3-]) using cyclic voltammetry. The most probable situations are the formation of (A) an insulating adsorbed film resulting in a partially blocked electrode behavior, (B) a porous film, or (C) an overall conductive film. Different parameters such as the standard rate constant, the charge-transfer coefficient, the electrode/adsorbed products/solution interface resistance, and the formal potential of the redox couple were determined. Through comparison of theoretical current-potential curves obtained by analytical calculations with experimental cyclic voltammograms, we found that the oxidized products of 2'-deoxyguanosine form a continuous conductive film on BDD.

Proton and metal ion binding to humic acids has been recognized as an important factor in controlling metal speciation and mobility in aqueous and soil environments. The binding and competition behavior of humics has not been fully described, however, due to the polydisperse mixtures of natural organic polyelectrolytes with different functional groups. The simplified discrete binding group type of model (Model A) was used in this study. Model A was applied to describe three single metals and their competitive binding on the humic acids. Model A considers only a single carboxyl group type and a single phenolic hydroxyl group type with a variable electrostatic interaction factor that is expressed as a polynomial equation. Metal binding experiments were performed using a batch-type dialysis equilibration method, and mass and charge balance expressions were used to calculate individual components of the system. The fit of Model A suggested that the major binding site for the three metal ions tested (Cd, Zn, and Cu) was a bidentate chelate of the carboxyl groups. Model A described two- and three-metal competition on the humic acids using the intrinsic stability constant for the single metal ion. The model used in this study adequately described the competition of two metals; however, it showed weaknesses when applied to more complex systems, especially when metals with substantially different binding characteristics were present. Model A presented a better prediction with adjusted Cu concentration (2:1:1 Cu/Cd/Zn). Abbreviations: HA, humic acid.