Showing papers in "Adsorption Science & Technology in 1995"
TL;DR: Bansal and de Sousa as mentioned in this paper were grateful to the Ministerio de Educacion y Ciencia, Government of Spain for a financial grant for their stay at the Instituto Nacional del Carb6n in Oviedo, Spain.
Abstract: The authors thank DGICYT (Project PB90-0067) and FICYT for financial support. R. C. Bansal
is grateful to the Ministerio de Educacion y Ciencia, Government of Spain for a financial grant
for his stay at the Instituto Nacional del Carb6n in Oviedo, Spain. J.C. de Sousa also thanks the
Univ. Est. de Maringa and CNPq (Brazil) for a grant.
53 citations
TL;DR: In this paper, the ability of sawdust to adsorb chromium(VI) from waste solutions has been studied in a batch reactor under forced convection conditions, where the rotational speed of the sawdust was investigated.
Abstract: The ability of sawdust to adsorb chromium(VI) from waste solutions has been studied in a batch reactor under forced convection conditions. Variables investigated were the rotational speed of the im...
43 citations
TL;DR: In this article, the adsorption of cationic dyestuffs (Basic Blue 69 and Basic Red 22) from aqueous solution by natural and activated clays has been investigated.
Abstract: The adsorption of cationic dyestuffs (Basic Blue 69 and Basic Red 22) from aqueous solution by natural and activated clays has been investigated. The maximum adsorption capacity (qmax) of BB 69 and...
23 citations
TL;DR: In this paper, the electric properties of sintered polycrystalline samples of V2O5 under a CH3OH atmosphere and without added extra oxygen has been performed as a function of time.
Abstract: A study of the electric properties of sintered polycrystalline samples of V2O5 under a CH3OH atmosphere and without added extra oxygen has been performed as a function of time. The gas composition ...
18 citations
TL;DR: In this article, the entropy of adsorption of water vapour on untreated and oxidized carbons, at different adorption temperatures, has been calculated, and the authors have shown that at 300-320 K, the adsoration is mainly physical and the isosteric heat decreases continuously as the surface coverage increases.
Abstract: The textural properties (surface area and porosity) of activated carbons change upon treatment with oxidizing solutions. The extent of this change is related to the strength of the oxidizing agent. Oxidation also changes the chemistry of the surface by forming carbon–oxygen groups which are the sites upon which the initial adsorption of water vapour takes place. The adsorption of water vapour at 300–320 K is mainly physical and the isosteric heat of adsorption decreases continuously as the surface coverage increases. The entropy of adsorption of water vapour on untreated and oxidized carbons, at different adsorption temperatures, has been calculated.
17 citations
TL;DR: In this paper, activated carbon was prepared from nut shells using a conventional two-stage method: carbonization followed by activation, where activation with steam or carbon dioxide as activating agent produced a range of chars of different burnoff.
Abstract: Activated carbon was prepared from nut shells using a conventional two-stage method: carbonization followed by activation. Activation with steam or carbon dioxide as activating agent produced a range of chars of different burn-off. These were characterized for their total and micropore surface areas, and benzene adsorption capacity. Benzene adsorption measurement provided an insight into the effect of porosity development on the adsorptive properties of the adsorbent. It was found that activated carbon products from nut shells were comparable, in terms of adsorption characteristics, with activated carbons from other lignocellulosic precursors. The evolution of porosity of the resulting carbons shows that carbon dioxide is the preferable agent for the production of activated carbon with a narrow micropore size distribution.
16 citations
TL;DR: The porous structures of synthetic active carbons have been examined in detail on the basis of nitrogen adsorption isotherms at 77 K using the αS method, the Dubinin-Stoeckli approach and the regularization technique as discussed by the authors.
Abstract: The porous structures of synthetic active carbons have been examined in detail on the basis of nitrogen adsorption isotherms at 77 K using the αS method, the Dubinin–Stoeckli approach and the regularization technique. Analysis of the porosity of synthetic active carbons shows that carbons obtained under identical conditions have dissimilar adsorption properties depending on the size of the granule. The application of the Dubinin–Stoeckli equation for the characterization of strongly heterogeneous carbons overestimates the maximum amount adsorbed in the micropores. In contrast to the Dubinin–Stoeckli equation, the regularization method gives a two-peak micropore size distribution and enables adsorbents with a bimodal porous structure to be estimated.
12 citations
TL;DR: The effect of temperature on the adsorption of p-nitrophenol (PNP) from aqueous solution has been determined at various initial phenol concentrations as discussed by the authors.
Abstract: The effect of temperature on the adsorption of p-nitrophenol (PNP) from aqueous solution has been determined at various initial phenol concentrations. Eight activated carbons were tested, being laboratory-prepared from apricot stone shells impregnated with H3PO4 and carbonized at 300–500°C. The adsorption capacity increased as a function of the percentage of activating acid added as well as the temperature of carbonization. The PNP surface areas evaluated were generally lower than the nitrogen BET surface areas due to restricted adsorption inside certain pores. Enthalpies of adsorption of 20–24 kJ/mol were estimated in all cases, except for one carbon which exhibited 'activated', diffusion-controlled adsorption. Greater than 90% desorption was observed at 100 ppm levels of PNP, but this decreased considerably at higher phenol levels.
10 citations
TL;DR: In this article, waste FeIII/CrIII hydroxide, generated from the treatment of CrVI in fertiliser industry effluent, was used as an adsorbent for the removal of toxic ions such as AsIII, HgII, CrIII and PO43, from aqueous solutions.
Abstract: 'Waste' FeIII/CrIII hydroxide, generated from the treatment of CrVI in fertiliser industry effluent, was used as an adsorbent for the removal of toxic ions such as AsIII, HgII, CrIII and PO43–, and dyes such as Rhodamine-B and Procion Orange M2R, from aqueous solutions. The removal was efficient except for Procion Orange.
10 citations
TL;DR: In this article, the impregnation technique was used to obtain catalysts of the type Co3O4/Al2O3, NiO/NiO/Al 2O3 and Co3 O 4/Co2O 3 with different chemical compositions and subjected to different calcination temperatures.
Abstract: Catalysts of the type CuO/Al2O3, NiO/Al2O3 and Co3O4/Al2O3 with different chemical compositions and subjected to different calcination temperatures were prepared using the impregnation technique.Th...
9 citations
TL;DR: In this article, the effect of physicochemical parameters characteristic for the adsorption system on changes in the surface diffusion coefficient was analyzed in a mixer tank with a constant solution volume, where modified activated carbons with chemically different surfaces were used as an adsorbent.
Abstract: The effective surface diffusion coefficient DS for model adsorption systems was determined experimentally in a mixer tank with a constant solution volume. As an adsorbent, modified activated carbons with chemically different surfaces were used. The adsorbates were single and binary aqueous solutions of 10 phenolic compounds. The effect of the physicochemical parameters characteristic for the adsorption system (pure energy of adsorption, dipole moment, molar reaction, parachor, solubility, molecular diffusion coefficient in water) on changes in the DS values was analyzed. It was observed that the extent to which DS decreased for adsorption from binary solutions relative to single solutions depended on the adsorbent–adsorbate interactions and the content of oxygen on the activated carbon surfaces.
TL;DR: In this paper, the sorption of cobalt on Haro river sand has been optimized with respect to shaking time, amount of sand and concentration of the cobalt, achieving a v/w ratio of 90 cm3/g.
Abstract: The sorption of cobalt on Haro river sand has been optimized with respect to shaking time, amount of sand and concentration of cobalt. Maximum sorption (>94%) was achieved from deionized water at a v/w ratio of 90 cm3/g. Among the ions tested, EDTA, citrate, thiosulphate, tartrate, PbII, ZnII, CrIII, AlIII, CdII and MnII reduced the sorption significantly. Manganese(II), ZnII, SeIV, CrIII and HlIV showed low sorption affinity towards the sand whereas ScIII, AuIII and ZrIV were strongly sorbed. Cobalt, along with elements having higher sorption, could be separated from metal ions showing low sorption. The sand could be used for the preconcentration and removal of cobalt from aqueous solutions. The sand may be exploited for wastewater treatment and water pollution abatement. The sorption data followed the Freundlich adsorption isotherm. The characteristic parameters 1/n = 0.81 ± 0.03 and A = 14.2 ± 0.5 mmol/g were evaluated for the system.
TL;DR: Water vapour adsorption on activated carbon has been investigated by an analysis of the nitrogen isotherms determined on carbon samples after their initial wetting at the same relative pressure followed by freezing.
Abstract: Water vapour adsorption on activated carbon has been investigated by an analysis of the nitrogen isotherms determined on carbon samples after their initial wetting at the same relative pressure followed by freezing. The simplified equation for micropore size distribution has been used. A relatively narrow range of pre-adsorbed water values has been found, within which the microporous space of the initial activated carbon changes as a result not only of filling but also of elimination (blocking) of parts of the texture.
TL;DR: In this article, the textural properties of the catalysts were determinable by thermal treatment in air at 500°C and at 25°C with varying amounts of CuO.
Abstract: CuO–AlPO4 samples containing varying amounts of CuO were prepared at 25°C. The catalysts were obtained by thermal treatment, in air, at 500°C. The textural properties of the catalysts were determin...
TL;DR: In this article, the interaction of anionic surfactants with multivalent cations leads to precipitation of the surfactant followed by redissolution of the precipitate, which is called adsorption.
Abstract: The interaction of anionic surfactants with multivalent cations leads to precipitation of the surfactant followed by redissolution of the precipitate. The adsorption of anionic surfactants from aqu...
TL;DR: In this paper, the authors investigated the effect of triphenyl phosphine (TPP) and carboethoxy methylene Triphenyl Phosphorane (CMTPP) on acid corrosion inhibitors.
Abstract: Phosphine compounds were investigated for their possible use as acid corrosion inhibitors. Electrochemical, weight loss and gasometry methods were employed to study the protective effect of triphenyl phosphine (TPP) and carboethoxy methylene triphenyl phosphorane (CMTPP). The inhibiting effect of TPP is estimated as 100% for an inhibitor concentration of 0.0005 M. Potentiodynamic polarization data indicate that both compounds act predominantly as cathodic inhibitors. The maximum inhibition efficiency was afforded by CMTPP at low concentrations, whereas at higher concentrations the protection efficiency of TPP increases. This was discussed on the basis of steric hindrance. The mode of adsorption of the inhibitors on the steel surface is proposed, as well as empirical kinetic equations based on the cathodic reaction. These were supported by fitting the experimental data to the Temkin adsorption isotherm and to the thermodynamic/kinetic model of adsorption. The free energy of adsorption, the binding constant, the lateral interaction and the number of active sites are reported and discussed.
TL;DR: In this article, the effect of heat treatment of manganese oxide/alumina catalysts on structural and textural properties and the catalytic decomposition of hydrogen peroxide were investigated.
Abstract: The effect of heat treatment of manganese oxide/alumina catalysts of various manganese content on the structural and textural properties and the catalytic decomposition of hydrogen peroxide were investigated. The FT-IR results have shown that depending on the calcination temperature and metal loading MnO2 and MnO3 are formed on the investigated samples. No spinel structure was detected under the experimental conditions. The surface areas were found to decrease with increasing calcination temperature and metal content up to 30 wt.% Mn. The mean pore radius increased with both calcination temperature and Mn content. The rate of catalytic decomposition of H2O2 was found to depend on the pH, the calcination temperature and the state of Mn on the catalyst surface.
TL;DR: In this article, the physicochemical characteristics of the modifying reagent pressures, the preparation conditions for the silica surface, the reaction temperature, the reagent pressure, the duration of treatment and the method employed for the modification process were studied.
Abstract: The effect of the following factors on the chemical and geometrical modification of aerosilogel (prepared from aerosil) was studied: the physicochemical characteristics of the modifying reagent pressures, the preparation conditions for the silica surface, the reaction temperature, the reagent pressures, the duration of treatment and the method employed for the modification process. The course of the surface reaction was followed by IR spectroscopy, differential thermal analysis and adsorption. During high-pressure modification, the geometrical parameters of the porous silica structure may be changed.
TL;DR: The surface properties of all the calcination products were determined from adsorption of nitrogen at 77 K and the chemisorption pyridine at 423 K using DTA and XRD techniques as mentioned in this paper.
Abstract: Pure alumina, CuO/Al2O3 and ZnO/Al2O3 have been calcined in the temperature range 500–1000°C and the phase changes involved followed using DTA and XRD techniques. The surface properties of all the calcination products were determined from the adsorption of nitrogen at 77 K and the chemisorption of pyridine at 423 K. The catalytic conversion of isopropanol on all the thermal products was also investigated.The surface areas of CuO/Al2O3 and ZnO/Al2O3 decreased while the pore radii increased with increasing calcination temperature from 500°C to 1000°C. CuAl2O4 forms above 800°C while ZnAl2O4 crystallizes at 600°C The acidity of the surface decreased when the calcination temperature was increased above 500°C. The conversion of isopropanol proceeds via dehydration of the alumina catalysts. CuO/Al2O3 and ZnO/Al2O3 surfaces catalyze both the dehydration and dehydrogenation of this alcohol.
TL;DR: In this article, the adsorption of cobalt on lead dioxide from aqueous solutions has been optimized with respect to the shaking time, the amount of adsorbent, the pH and the concentration of ads absorbate at 293 K.
Abstract: The adsorption of cobalt on lead dioxide from aqueous solutions has been optimized with respect to the shaking time, the amount of adsorbent, the pH and the concentration of adsorbate at 293 K. Under such optimum conditions, the adsorption of cobalt on lead dioxide has been studied at different temperatures and the process found to be endothermic with the distribution coefficient (KD) increasing with increasing temperature. The data fitted very well to the Langmuir, Freundlich and Dubinin–adushkevich isotherms, allowing the corresponding constants to be calculated. Values of ΔH0 and ΔS0 were calculated from the slope and intercept of the plots of In KD versus 1/T. The value of ΔG0, which decreased with increasing temperature, showed that the adsorption is more favourable at higher temperatures.
TL;DR: In this article, the model of partially mobile adsorption on microporous solids has been formulated for the cases of energetically homo- and heterogeneous adsorbents.
Abstract: The model of partially mobile adsorption on microporous solids has been formulated for the cases of energetically homo- and heterogeneous adsorbents. Ethane and xenon adsorption isotherms on various forms of zeolite have been described by relationships derived from the proposed adsorption model.
TL;DR: Adsorption equilibrium data for the systems acetone/activated carbon and cumene/activated Carbon measured over the pressure ranges 0.2-20 500 Pa and 2-420 Pa, respectively and over the temperature...
Abstract: Adsorption equilibrium data for the systems acetone/activated carbon and cumene/activated carbon measured over the pressure ranges 0.2–20 500 Pa and 2–420 Pa, respectively and over the temperature ...
TL;DR: In this article, the effect of added cations, anions and other metal ions was investigated, and the conditions for maximum adsorption were optimized, and ytterbium was found to separate well from solutions containing CoII, EuIII and ZnII under given conditions.
Abstract: Adsorption studies of ytterbium on sand from dilute nitric acid solutions have been studied in relation to the properties of both adsorbate and adsorbent. The conditions for maximum adsorption were optimized. The effect of added cations, anions and other metal ions were also investigated. Ytterbium was found to separate well from solutions containing CoII, EuIII and ZnII in appreciable amounts under given conditions.
TL;DR: "~~1 ~ ~~'il_, ~~l>JI c..,LJI ullz.-:.; 4 ~l; ~~_, t) JJ.i~l i.
Abstract: "~~1 ~ ~~'il_, ~~l>JI c..,LJI ullz.-:.; 4 ~l; ~~_, t) JJ.JI~I_, ~~~ -w~_,~l j.i~l i~~ ul;~l>JI ~~_,J)tl_, 4~~~ d~~) J..A~l i;~..~..c.
TL;DR: In this article, an extensive study on the determination of the hydrodynamic layer thickness of polymer solutions and melt polymers was conducted with a surface force apparatus, and it appeared that in contrast to the molecular weight, polymer concentration has little effect on the relative hydrodynamic layer thickness (LH/2RH, LH/2Rg).
Abstract: An extensive study on the determination of the 'hydrodynamic' layer thickness of polymer solutions and melt polymers was conducted with a surface force apparatus. For different concentrations and polymer molecular weights, a 'hydrodynamic layer' of fluid was detected on each solid surface which did not contribute to the flow. These thicknesses, denoted as LH, are compared to the characteristic polymer dimensions and the hydrodynamic (RH) and gyration (Rg) radii. It appears that in contrast to the molecular weight, polymer concentration has little effect on the relative hydrodynamic layer thickness (LH/2RH, LH/2Rg). Indeed, this ratio indicates that two coils of low molecular weight and one coil of high molecular weight are 'immobile' on the solid surfaces. The mechanism responsible could be entanglement of the free (unattached) chains in the bulk with immobilized chains on the surface.
TL;DR: In this paper, the surface area, micropore and total pore volumes were determined from nitrogen adsorption on metal impregnated charcoal using a continuous flow method using a Quantasorb sorption system, and it was observed that metal impregnation did not contribute any extra surface area to the charcoal.
Abstract: Nitrogen adsorption on metal (Ni, Cu, Zn) impregnated charcoal has been carried out at 77 K by the continuous flow method using a Quantasorb sorption system. It was observed that such metal impregnation did not contribute any extra surface area to the charcoal. The values of the surface area, micropore and total pore volumes determined from nitrogen adsorption follow the sequence Ni–charcoal < Cu–charcoal < Zn–charcoal < charcoal. Their behaviour is discussed in terms of the ionic radii of the metal ions concerned. The pore size distribution curves demonstrate the microporous nature of the charcoal, with the micropores contributing significantly to the total pore volume.
TL;DR: In this article, the effect of chloride ions (HCl and CaCl2) on the rate of dissolution of steel in the presence of mixtures of phosphoric acid and alcohol has been investigated.
Abstract: The corrosion behaviour of mild steel has been evaluated by accurate weight loss measurements in aerated phosphoric acid/organic solvent mixtures. The media studied were butanol, butane 1,4-diol, isopropyl alcohol, butane 1,3-diol and propylene glycol. The results show that the organic solvents improved the corrosion resistance of mild steel to an extent depending on the concentration of the acid and the solvent as well as on the different protic and stereochemistry properties of the alcohols considered. The inhibition efficiency increased in the order: butanol > butane 1,4-diol > isopropyl alcohol > butane 1,3-diol > propylene glycol. The effect of chloride ions (HCl and CaCl2) on the rate of dissolution of steel in the presence of mixtures of phosphoric acid and alcohol has been investigated. Aqueous solutions containing Cl– ions inhibit the dissolution of steel in phosphoric acid, such inhibition being enhanced in the presence of propylene glycol or butanol. The corrosion rate of steel in phosphoric acid was also measured as a function of the concentration of aniline derivatives. It was found that 3% vol/vol inhibitor was sufficient to level off the protection efficiency. The order of inhibition efficiency was n,n-dimethyl aniline > n-methyl aniline > aniline. Good agreement was obtained between the kinetic–thermodynamic and Flory–Huggins models. At 35% and 50% phosphoric acid concentration, each molecule of the inhibitor occupied more or less than one active site on the metal surface depending on the molecular structure of the inhibitor. The corresponding negative values of the free energy of adsorption varied between 21.5 and 23.3 kJ/mol and 17.0 and 21.1 kJ/mol respectively for inhibitors at low and high acid concentrations.
TL;DR: A technical silica gel was impregnated with a solution of the titled heteropoly acid (1-20 w/w%) and calcined at 400, 600 or 800 °C as discussed by the authors.
Abstract: A technical silica gel was impregnated with a solution of the titled heteropoly acid (1–20 w/w%) and calcined at 400, 600 or 800 °C. Dehydration of the alcohol generally increased with the loaded acid, and decreased almost linearly with the reaction temperature (360–260°C). The best alcohol decomposition was achieved over the 600°C-calcined catalysts when over 90% conversion to propene was attained. The apparent activation energies decreased with the degree of loading and attained a value of 22 kJ/mol on the 600°C-calcined 20% HPMo-supported catalyst (half that on the solids calcined at 400°C and 800°C). The catalytic dehydration cannot be described by means of a proton-involved mechanism on the severely treated catalysts at ≥600°C. An outer surface mechanism might be effective involving terminal oxygens and MoV ions.
TL;DR: In this article, the textural properties of calcined catalysts have been determined from nitrogelectric samples of nickel on alumina (1.1-10.4 wt.% Ni) were prepared by impregnating alumina in hydrated nickel nitrate.
Abstract: Samples of nickel on alumina (1.1–10.4 wt.% Ni) were prepared by impregnating alumina in hydrated nickel nitrate. The textural properties of the calcined catalysts have been determined from nitroge...
TL;DR: In this article, the catalytic conversion of cyclohexane over Ni/Al2O3 was investigated using a microcatalytic pulse technique, and the nickel content was varied between 7.9-34.3 wt.% NiO and the reaction temperat...
Abstract: The catalytic conversion of cyclohexane over Ni/Al2O3 has been investigated using a microcatalytic pulse technique. The nickel content was varied between 7.9–34.3 wt.% NiO and the reaction temperat...