bluuebunny/crossref_metadata_2025 huggingface dataset:
A Theoretical Foundation for the Concept of Differential Urbanization
Authors: Geyer Hermanus S. , Kontuly Thomas
Published: July 2017

This paper develops a theoretical foundation for the notion of differential urbanization, in which groups of large, intermediate-sized, and small cities go through successive periods of fast and slow growth in a continuum of development that spans the evolution of urban systems in developed and less developed countries. A model depicting net migration patterns over time for major metropolitan, intermediate-sized, and small urban areas identifies six stages of differential urbanization. Data from three countries that span the development spectrum are used to test the accuracy of this model. A distinction between mainstream and substream migration flows provides an indicator of the concurrent concentration and deconcentration forces shaping urban systems. Counterurbanization represents the final phase in the first cycle of urban development, and is followed by a second cycle in which urbanization and spatial concentration dominate once again. At advanced levels of urbanization, the model can be used to characterize the degree of development within regions or subregions of a country. Also, precise definitions are suggested for the “clean break,” the end of urbanization, and the beginnings and ends of polarization reversal and counterurbanization.
When Deaths Exceed Births: Natural Decrease in the United States
Authors: Johnson Kenneth M.
Published: July 2017

Natural decrease is no longer rare in the United States. By 1989, 34 percent of all U.S. counties had experienced at least one year of it. Natural decrease is most common in rural areas remote from metropolitan centers. Regional concentrations of natural decrease exist in the Great Plains, the Corn Belt, and East Texas with scattered pockets in the Ozark-Ouachita Uplands, Upper Great Lakes, and Florida. Natural decrease is caused by age structure distortions stimulated by protracted, age-specific migration. Although temporal variations in fertility also contribute to natural decrease, these variations are not due to below average fertility. Natural decrease is symptomatic of fundamental changes in the demographic structure of an area.
Specific Surface Area of Hydrated Silicon Dioxide Measured by Chemisorption
Authors: Gobet J. , Kováts E. sz.
Published: July 2017

Various methods of specific surface area determinations have been compared: the BET-method, Sing's αs-method and the calculation from the monolayer capacity of dense chemisorbed trimethylsiloxy and (3,3-dimethylbutyl)-dimethyl-siloxy layers. It was shown that fume silicas as well as xerogels precipitated from water gave consistent results if the samples underwent a 70 h hydrothermal treatment in boiling water. The methods were calibrated on a similarly hydrated, low surface area fume silica. Slight differences in behaviour were observed between the two classes of silica. Surprisingly, the results disproved any serious dependence of the form of the nitrogen adsorption isotherm on surface curvature.
The n-Nonane Preadsorption Method Applied to Activated Carbons
Authors: Linares-Solano A. , López-González J. D. , Martín-Martinez J. M. , Rodriguez-Reinoso F.
Published: July 2017

The n-nonane preadsorption method has been applied to evaluate the microporosity of two series of activated carbons (prepared from olive stones and almond shells) reacted with air at 623 K to different degrees of burn-off. A detailed study of the experimental conditions needed for the successive removal of the n-nonane preadsorbed has been carried out, showing that the sample outgassed at 673 K is identical to the original. In general, the results obtained with the preadsorption of n-nonane are satisfactory only in carbons with a narrow microporosity. On the other hand, this method has been used to calculate the apparent surface area of the carbons from the n-nonane retained using an Am value of 0.844 nm2, the results being in good agreement with the N2 BET values. An analysis of the evolution with burn-off of the parameters C(BET) and D(DR) has also been carried out and their relationship calculated; both parameters describe reasonably well the evolution of the microporosity of the carbons.
The General Equation of the High Pressure Mercury Porosimetry
Authors: Kadlec O.
Published: July 2017

On the basis of the Gibbs condition of the thermodynamic equilibrium of a heterogeneous system in the field of force, a general expression is derived for the dependence of the pressure p' of the intruded liquid mercury as a function of the equivalent pore radius r. For pore radii greater than 30 nm, this equation goes over into the well known Washburn equation. For pores with r smaller than 2.5 nm sizeable deviations from the Washburn relation occur. It is shown that supermicropores (r from 0.8 to 1.4 nm), communicating with the system of meso and macropores, are filled by mercury at the same pressures pl at which the filling of mesopores (r from 2 to 10 nm) takes place.
Adsorption of Dilute Hydrocarbon Solutes from Aqueous Solutions on Heterogeneous Adsorbents
Authors: Sircar S.
Published: July 2017

A mathematical model for describing adsorption of dilute hydrocarbon solutes from aqueous solutions on energetically heterogeneous activated carbons is developed. It is shown that the commonly observed Freundlich type isotherm can be caused by the adsorbent heterogeneity. Data for adsorption of various hydrocarbon solutes on the CAL activated carbon are analyzed.
Kinetics of Cation Desorption from Heterogeneous Solid Surface at Very Low Coverage
Authors: Thornton Edward W. , Renn Guy
Published: July 2017

Cations desorb from solid surfaces into elecrolyte solutions slowly at very low coverages. The kinetics of this slow desorption were studied using radioactive tracers in a flow cell experiment. On a number of real adsorbents the kinetics are explained by rate limiting desorption from random, weakly heterogeneous surface sites. Slow desorption is not liquid phase diffusion-controlled. The distribution of adsorption site energies which accounts for the desorption kinetics also gives rise to the Freundlich adsorption isotherm. Desorption rates into simple electrolytes depend upon pH and ionic strength; a primitive model of the interfacial region accounts for yttrium ion desorption rates from a polyurethane into NaNO3 + HNO3/NaOH solutions.
Cu(II) EPR: A Complementary Method for the Thermodynamic Description of Surface Complexation
Authors: Motschi H.
Published: July 2017

Static EPR parameters of adsorbed Cu2+aq ions onto hydrous oxide surfaces indicate the formation of inner sphere type complexes with surface functional groups. The formed complexes are suggested to be of the type (≡MeO)4– nCu(H2O) n+2, n = 2 for δ-Al2O3, one type of SiO2, (≡MeO)4Cu(H2O) for TiO2(Anatase), and one type of SiO2. An empirical relationship has been found between thermodynamic stability constants of the complex and the EPR-parameter g‖. This method is applied in a series of ternary complexes on δ-Al2O, of the type (≡AlO)2Cu L1L2(H2O)2(L1L2 = bidentate ligand) to yield information about speciation of Cu(II) and the corresponding stability constants. The copper hyperfine data are interpreted in terms of an LCAO-MO – approach. New possibilities arise for the interpretation of the behaviour of Cu(II) in biological systems. An alternative description is presented to the current picture of cation adsorption in layer silicates and systems of interest in catalysis (e.g. zeolites). ENDOR spectroscopy of copper(II) complexes on δ-alumina confirms the conclusions reached at EPR stage.
Liquid/Solid Interfaces: Studies of Kinetics of Isotope Exchange
Authors: Kosmulski M. , Jaroniec M. , Szczypa J.
Published: July 2017

Many radiotracer methods based on the phenomenon of isotope exchange are used in the studies of interfaces. These methods enable an investigation of heterogeneous systems at equilibrium. Studies of the kinetics of isotope exchange also give valuable information about systems in which ions appearing in the solution are at the equilibrium state with the same ions adsorbed on the solid particles or built into their crystalline lattice. Such systems, in which the solids are either ionic crystals or ion-exchanger beads, are taken into account in the present paper. In spite of wide applications, the phenomenon of heterogeneous isotope exchange is rather poorly understood and the fragmentary results reported in the literature do not lead to unambigous conclusions concerning the mechanism of this phenomenon. In the present review, the theoretical models of isotope exchange are discussed and compared with experimental results. The results are also discussed with respect to enlargement of applications of isotope exchange to investigation of heterogeneous systems, e.g. containing porous solid particles.
n-Decane adsorption on SiO2-adsorbents
Authors: Jänchen J. , Stach H.
Published: July 2017

The equilibrium of n-decane adsorption on microporous and mesoporous SiO2-adsorbents (silicalite, SiO2-faujasite US-Ex, aerosil 200) was investigated using isoteric measurements. Following the comparison of the dispersion energy for porous and non-porous adsorbents carried out by Barrer (1966) and theoretical investigations of de Boer & Custers (1934) experimental data were analysed. A simple empirical correlation between the pore diameter of the adsorbents and the initial isosteric adsorption heat was found. The equation parameters are the condensation heat of the adsorbate, the diameter of the adsorbate molecule and an empirical constant.
The NO Chemisorption Activity of δ-FeOOH Having Different Magnetic Properties
Authors: Kaneko K. , Inouye K.
Published: July 2017

δ-FeOOH samples of various magnetic susceptibilities from paramagnetic to ferromagnetic region have been prepared. The correlation rate for paramagnetic NO molecules and magnetic susceptibility of the δ-FeOOH samples have been studied. In addition the electrical conductivity of the δ-FeOOH samples was measured at 303 K and various frequencies (d.c., 200–10 M Hz). The NO chemisorption rate decreases with increasing the magnetic susceptibility of δ-FeOOH. The paramagnetic δ-FeOOH of small crystallite size has the highest chemisorption rate of all FeOOH modifications. The rate-determining step in the NO chemisorption is assumed to be an electron-transfer from δ-FeOOH crystal to an NO molecule, which is governed by the magnetic ordering of spins in δ-FeOOH.
Adsorption Properties of the AlPO4-5 molecular sieve
Authors: Lohse U. , Noack M. , Jahn E.
Published: July 2017

The adsorption properties of AlPO4-5 samples have been studied by kinetic and equilibrium measurements using hydrocarbons and water as adsorbates. From the adsorption of hydrocarbons a non-polar surface of the AlPO4-5 molecular sieve is concluded. The peculiarities of water uptake are interpreted taking into account n.m.r. results as due to the formation of a crystal hydrate.
Carbonization of Olive Wood: Evolution of Surface Area and Porosity with Treatment Temperature
Authors: López-González J. de D. , Valenzuela-Calahorro C. , Navarrete-Guijosa A. , Gomez-Serrano V.
Published: July 2017

A study has been made of the influence of pyrolysis temperature on the surface area and porosity of carbonized samples prepared by heating olive tree wood in flowing N2 (100 cm3, min−1) at different temperatures (473, 573, 673, 773, 873, 973, 1073, 1173 and 1273 K using a heating rate of 5 K per min). At temperatures above 723 K carbon is produced. The adsorptive properties of the samples have been determined by N2 adsorption of 77 K. Meso and macroporosity have been followed by mercury porosimetry. Surface area was found to increase up to 873 K, and thereafter to remain practically constant to 1173 K. The average pore diameter was not influenced.
Analysis of Cationic Surface Active Agents Using DME and Its Relevance to Their Adsorption
Authors: Matysik J. , Kroszka H. , Persona A.
Published: July 2017

The paper describes an application of dropping mercury electrode (DME) for analytical determination of certain cationic surface active agents and their mixtures and presents obtained thermodynamical data of adsorption of investigated substances.
Adsorption of Para Substituted Anilines from Cyclohexane Solution on Sepiolite
Authors: Gonzalez-Pradas E. , Valverde-Garcia A. , Villaranca-Sanchez M. , Del F. , Bueno Rey
Published: July 2017

The adsorption processes of different para-substituted anilines from cyclohexane solution on natural sepiolite have been studied. The adsorption isotherms may be classified as type L-2 of the Giles classification in the p-bromoaniline and p-toluidine cases, and as type H-2 in the p-acetylaniline case.

The experimental data points have been fitted to the Langmuir equation and the adsorption capacities, surface areas available to the amine molecules and apparent equilibrium constants have been calculated. The apparent thermodynamic magnitudes corresponding to the adsorption processes have also been determined.
Remarks on the Adsorption of Alcohols from Ternary Solutions in Benzene and n-Heptane on Silica Gel
Authors: Goworek J.
Published: July 2017

Adsorption equilibria of binary and ternary solutions of alcohols in benzene and n-heptane on silica gel have been studied in order to clarify the mechanism of adsorption process of these compounds. The excess adsorption isotherms have been measured for hydrocarbon solutions of methanol, ethanol, butanol and pentanol. Interpretation of the experimental data was performed in terms of material balance relationships between bulk and surface phase. In the case of n-heptane solutions the multilayer surface structure is formed and the surface phase contains the alcohol molecules only. For benzene and ternary (alcohol + benzene + n-heptane) solutions the mixed character of the surface phase is observed. The composition of this phase is determined by competition of liquid components for the silica surface as well as its complexing tendency. Moreover, the extent of adsorption in methanol systems is connected with miscibility of liquid components.
Texture Studies on Chromium Oxide Doped Catalysts
Authors: El-Salaam K.M. Abd , El-Awad A.M.
Published: July 2017

Physisorption of N2 gas at 77 K has been used to determine the surface area (SBET) and porosity of Cr2O3 impregnated with Li2O in molar ratios extending from 0.25 to 50 mol %. Calcination of catalysts was affected in air flow in temperature range of 473-773 K. Variation of the SBET-calcination temperature relationship was interpreted according to the possible lattice rearrangements via a solid-state reaction leading to Li2CrO4 phase formation for Li2O rich samples and by creation of cation vacancies in case of Li2O trace samples. The cumulative calculations together with Va-t plots showed a mesoporous surface nature of samples.
Determination of the Texture of Narrow-Pore Zeolites by the Dynamic Desorption Method
Authors: Pospisil J. , Patzelova V.
Published: July 2017

This work describes the first application of the desorption of nitrogen under dynamic conditions to characterize the texture of a natural zeolite. These dynamic conditions are very similar to those in actual sorption and catalytic processes. It was found that, under the experimental conditions described, nitrogen is desorbed from narrow-pore zeolites with a kinetic parameter comparable with the diameter of the nitrogen molecule in two separate steps that can be both qualitatively and quantitatively assigned to the amorphous and microporous fractions of the test zeolite.
Adsorption Equilibrium of Xylene Isomers and p-Diethylbenzene in the Liquid Phase on a Y Zeolite
Authors: Hsiao H.C. , Yih S.M. , Li M.H.
Published: July 2017

The saturated adsorptive capacity, adsorption equilibrium constant and adsorption isotherms of p-xylene, m-xylene, ethylbenzene (EB) and p-diethylbenzene (PDEB) on a K–BaY zeolite with n-heptane as the solvent have been studied at 25°C. The adsorption isotherms of the six binary pairs of these solutes with n-heptane as the solvent have also been determined at 25°C. The data cover a concentration range of xylene isomers from 0.05–0.3 mmol/ml. The molar adsorption capacity of the K–BaY zeolite for the different sorbates was found to be in the order: p-xylene > EB > m-xylene ≈ PDEB. PDEB is normally used as the desorbent for the Parex process. Three types of isotherm model, i.e. Langmuir, Freundlich and Langmuir–Freundlich, have been used to fit the data. The results indicate that the Langmuir–Freundlich isotherm provides a reasonable representation of the equilibrium data for the xylene isomers on a K–BaY zeolite.
The Adsorption of Cement Superplasticizers on to Mineral Dispersions
Authors: Pierre A. , Mercier R. , Foissy A. , Lamarche J.M.
Published: July 2017

The adsorption of polymeric sulphonated naphthalene formaldehyde (SNF) and sulphonated melamine formaldehyde (SMF) on to titanium dioxide and calcium carbonate has been measured in aqueous media. The magnitude of these adsorptions is strongly dependent on electrostatic interaction irrespective of the pH value. This result has been established by studying the adsorption of the polyelectrolytes from solutions of different composition. The calcium ion plays a prominent role in the process of adsorption, especially at high pH where electrical interactions do not favour the reaction.

The polymeric nature of the fluidizing agents is demonstrated by an increase in adsorption with molecular weight and by adsorption/desorption experiments where the reaction has been shown to be irreversible. The amount adsorbed at maximum coverage does not depend on the nature of the mineral, but mainly on electrical interactions between the monomer units.
Two-Phase Flow in a Two-Dimensional Bidisperse Anisotropic Pore Network Model
Authors: Schweighart Peter J. , Nicholson David
Published: July 2017

A two-dimensional network model for a heterogeneous material in which ‘micro’-porous particles are compacted so as to leave a mesoporous interparticle space has been constructed. In this paper the model is used to study the transport of an adsorbable gas. The two-phase flow consists of a Knudsen gas-phase component and a surface-phase component with adsorption in the Henry's law region. The results are expressed in terms of the structure factors which relate the behaviour of the model to that of a single cylindrical capillary having the same internal area and porosity. The response to pure gas-phase flux is dominated by the mesoporous network, but when flux exchange between gas and surface phases can occur, the ‘micro’-pore distribution can become important for certain bidisperse distributions.
Adsorption of Chloropicrin onto Humidified Activated Carbon Surfaces
Authors: Anstice P.J.C. , Halliday N. , Alder J.F.
Published: July 2017

Humidified activated charcoal samples have been exposed to chloropicrin-charged test atmospheres under controlled conditions of concentration, temperature, relative humidity and flow rate.

The molar ratio of displaced water:adsorbed chloropicrin was observed to increase with chloropicrin loading.

Estimates were made of the adsorption face areas and molecular volumes of the chloropicrin and water molecules. The ratios of adsorption face areas and molecular volumes were estimated as 3.4:1 and 7.7:1, respectively.

Early in the sample challenge molar ratios up to about 3.4:1 were observed; it is proposed that these result from the adsorption of chloropicrin onto vacant sites or onto water monolayers with readsorption of water occurring elsewhere on the surface. As these pores become full, chloropicrin adsorbs in water-filled pores displacing water molecules of approximately the same total volume.
External Mass Transport Processes during the Adsorption of Basic Dyestuffs onto Maize Cob
Authors: El-Geundi Mohammad S.
Published: July 2017

A simple kinetic model has been developed to explain the external mass transport of the basic dyestuffs (Basic Blue 69 and Basic Red 22) from aqueous solutions onto maize cob. The model enables the external mass-transfer coefficients, KS, to be determined and these are characteristic of the rate of mass transport of dye across the boundary layer surrounding the adsorbent particle. The external mass-transfer coefficient has been found to vary linearly with agitation, initial dye concentration, particle size range and mass of maize cob, according to the general equation KS = X(variable)Y.
Preformed Zeolite Products to be Used in Adsorption Heat Pumps. Part 1. Preparation Methodology and Adsorption Measurements
Authors: Cacciola G. , Czepirski L. , Restuccia G. , Giordano N.
Published: July 2017

Recent results on adsorption heat pumps have indicated the technical feasibility of these types of systems, although the problems related to the inefficient thermal transmission between the external energy vector and the solid adsorbent still remain. In order to solve these problems, a prefixed-shaped form of the solid adsorbent has been prepared by a patented procedure developed in this Institute. In the present paper the preparation methodology, the material and the adsorption measurements are described.
Calculating Surface Fractal Dimensions of Adsorbents
Authors: Neimark Alexander V.
Published: July 2017

A critical analysis of different methods for determining surface fractal dimensions using adsorption measurements is presented. A new method for calculating surface fractal dimensions from capillary condensation or mercury porosimetry data is proposed. This method does not use any model of adsorption on the fractal surface. It is based on the thermodynamic relationship between the surface area of the interface and the amount of the adsorbate. The formulae obtained for surface fractal dimensions do not contain any additional parameters except the experimental data. A typical example of calculating the surface fractal dimensions of an active carbon sample is presented.
Adsorptive and Membrane-type Separations: A Bibliographical Guide 1991
Authors: Ray Martyn S.
Published: July 2017

This article provides a bibliographic listing of published papers concerned with adsorptive, membranes and associated separations during 1991. The references are taken from the 40 most important chemical engineering journals. This paper provides an update to the literature as provided in a previous bibliographic paper by Ray (1990). A complete bibliography of the chemical engineering literature for 1991 has been published by the author (Ray, 1992). The following topics are included in this paper: theory; design data; adsorbents; PSA and cyclic systems; systems and applications; liquid-phase adsorption; membrane separations; ion exchange, reverse osmosis, chromatography, etc.
Parameters for the Adsorption of Tungsten from Metatungstate Solution on to Alumina
Authors: Pizzio L.R. , Cáceres C.V. , Blanco M.N.
Published: July 2017

The adsorption of tungsten from aqueous solutions of ammonium metatungstate on to alumina has been studied, an adsorption isotherm at 20°C being obtained. The isotherm had a sigmoidal shape and reached a flat plateau region at an adsorbed concentration of 100 mg W/g Al2O3 within the range of initial concentrations used (up to 70,000 ppm W). A proposed relationship between the adsorbed concentration and the equilibrium solution concentration has enabled the adsorption equilibrium parameters to be estimated.

Impregnation of flat thin layers of alumina with concentrated tungstate solutions (5,100, 31,200 and 72,800 ppm W) has also been studied. Fits between the experimental tungsten concentration profiles and those obtained via a theoretical model of the impregnation phenomena allowed the adsorption kinetic parameters to be obtained. These parameters are useful in predicting the concentration profiles resulting from the pore-filling impregnation of pellets provided a suitable theoretical model is employed.
Investigation of Nickel Ion Removal by Means of Activated Clay
Authors: Hawash S. , Farah J.Y. , El-Geundi M.S.
Published: July 2017

Natural and activated clays have been investigated as adsorbents for the removal of nickel from wastewater. Analysis of the natural clay under test showed that it was composed, approximately of 51% kaolinite, 46% montmorillonite and 3% illite, having a specific surface area of 65 m2/g.

The natural clay was treated with different activators (HCl, NaCl and H2O2) to enhance its adsorption capacity towards nickel. The efficiency of such activation was greater by 16.0% and 23.2% in the case of NaCl and H2O2, respectively, relative to untreated clay. No significant increase in the adsorption capacity was brought about by HCl treatment.

A limited comparison has been made between clay and activated carbon by performing isotherm studies under similar conditions. The results indicate that the adsorption capacity of clay activated with H2O2, clay activated with NaCl and natural clay is 216.9%, 204.2% and 176.1% that of activated carbon, respectively.

Based solely on the adsorption capacity, an economic analysis demonstrates that natural clay is the cheapest material, followed by clay activated with NaCl and clay activated with H2O2. The relative costs of removing nickel using natural clay, clay activated with NaCl and clay activated with H2O2 were found to be 2.8%, 5.4% and 25.4%, respectively, that of activated carbon.
Adsorption Characteristics of Organic Dyes on Alumina Powder from Aqueous Solutions
Authors: Saleem M. , Afzal A. , Naeem T.M. , Mahmood F.
Published: July 2017

Adsorption of industrially important dyes (Acid Red 88, Acid Orange 8 and Bismark Brown R) on alumina from aqueous media has been investigated as a function of shaking time, amount of adsorbent, concentration of adsorbate and temperature. It is noted that the adsorption of Acid Red 88, Acid Orange 8 and Bismark Brown R on alumina decreases with an increase in temperature. The results obtained show that the adsorption isotherms at different temperatures are S-type and obey the Freundlich type of adsorption equation. Isosteric heats of adsorption (qst) have also been calculated at different coverages from the adsorption isosters and have been interpreted. The qst values for all the adsorption systems decrease with increasing surface coverage indicating that the alumina used possessed a heterogeneous surface with sites of different activities. The results also indicate that initial adsorption, whether by chemical or physical means, occurs first on the most active sites and then, as the concentration of adsorbate is increased, on sites of lesser activity.
The Porosity of Carbon Materials as Estimated by Thermogravimetric Analysis
Authors: Goworek J. , Stefaniak W. , Swiatkowski A.
Published: July 2017

The thermal desorption of benzene has been measured using a thermal analyzer. Pore size distributions of active carbons and carbon blacks have been determined on the basis of thermogravimetric curves using the Kelvin equation. Calculated distributions and total pore volumes have been compared with those derived from adsorption/desorption isotherms of nitrogen and benzene vapour.
Effect of Cationic and Anionic Surfactants on the Electrokinetic Potentials of Cassiterite and Quartz in the Presence of Polyvalent Cations
Authors: Taha Fouad , Attyia Khairy M.E. , Saleh Mohamed B. , Khalaf Moustafa M.R.
Published: July 2017

The effect of different polyvalent electrolytes (FeCl3, AlCl3, LaCl3, CeCl3 and ThCl4) on the adsorption of different surfactants (primary amine hydrochloride, sodium oleate, sodium dodecyl sulphate and phenyl disodium orthophosphate) on cassiterite and quartz particles has been studied using microelectrophoresis. The zeta potentials of the oxides and their isoelectric points were determined as a function of pH in the presence of constant concentrations of both surfactants and electrolytes. The mechanism of adsorption of surfactants on cassiterite and quartz surfaces modified by salt cations is discussed. In general, in the presence of the above-mentioned salts, the zeta potentials and the isoelectric points (IEPs) of the oxides are considerably changed on addition of different surfactants.
Adsorption Study on the Corrosion Inhibition of Steel in H3PO4/Organic Solvent Mixtures
Authors: Khamis E. , Hosny A.
Published: July 2017

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.
Utilization of Palm-Fruit Bunch Particles for the Adsorption of Dyestuff Wastes
Authors: Nassar Mamdouh M. , Hamoda Mohamed F. , Radwan Gamil H.
Published: July 2017

Particles prepared from palm-fruit bunches have been used in batch tests for the adsorption of a basic dye (BR 18) over a range of initial dye concentrations with adsorbent particle sizes varying in the range 106–300 μm. The results revealed the potential of palm-bunch particles as low-cost adsorbents. The uptake of the basic dye was higher at smaller adsorbent particle sizes. The adsorption isotherm followed both the Langmuir and Freundlich models. Values of the separation factor, R, indicate favourable adsorption for the basic dye/palm-fruit bunch particle system, i.e., 0 < R < 1 and n > 1.
Removal of Ammonia from Aqueous Solution Using Activated Carbons
Authors: El-Nabarawy Th. , Fagal G.A. , Khalil L. B.
Published: July 2017

The surface areas of non-activated, activated and modified activated carbons were determined from the adsorption of nitrogen at −196°C and of carbon dioxide at 25°C. The base neutralization capacities were determined from the adsorption of NaOH, Na2CO3, NaHCO3 and NH4OH. The amount of oxygen combined to the carbon surface was estimated by measuring the pressure of CO and CO2 obtained on outgassing the carbon sample in the temperature range 300–1000°C.

The surface area of activated carbon is not a determining factor in its ammonia adsorption. The surface acidity of the active carbon is a good measure of its capacity for ammonia removal. Ammonia adsorption increases appreciably upon surface oxidation of carbons with oxidizing gases and solutions. The acidic groups on the surface of carbons differ in their strength. Only a fraction of the surface covered by the carbon–oxygen groups is responsible for the capacity of the carbon towards ammonia. Most of the adsorbed ammonia is recovered upon treatment with dilute hydrochloric acid leaving the surface free for successive ammonia adsorption cycles.
Effect of Different Cations on the Adsorption of Dy3+, Gd3+, Eu3+ and Sm3+ Ions on Activated Charcoal from Aqueous Solutions
Authors: Qadeer Riaz , Hanif Imtiaz , Hanif Javed
Published: July 2017

The effect of different cations on the adsorption of Dy3+, Gd3+, Eu3+ and Sm3+ ions on activated charcoal from aqueous solutions (pH = 4.0) has been studied at room temperature (295 ± 1 K). Their effect on the adsorption of the metal ions has been correlated with the charge density (Z/r) of the cations. It was observed that cations with a larger Z/r value reduced the adsorption of metal ions more than cations with smaller Z/r values. It was also observed that the ease of adsorption of the metal ions followed the sequence: Dy3+ > Gd3+ > Eu3+ > Sm3+. Such data are important in relation to the recovery of metal ions from solution.
Adsorption Equilibria of Cadmium on Algal Biomass
Authors: Hashim M.A. , Chu K.H. , Phang S.M. , Ong G.S.
Published: July 2017

Adsorption equilibria of cadmium on the non-living algal biomass of Chlorella vulgaris were studied using batch stirred-tank methods. The adsorption process was rapid, achieving equilibrium in a few minutes. Environmental factors such as pH, biomass dosage and buffer concentration had a considerable influence on the equilibrium isotherms. The adsorption capacity of the biomass increased with increasing pH. This behaviour was attributed to decreased protonation of the binding sites and decreased competition for binding between the cadmium ions and protons with increasing pH. The equilibrium data measured at different pH values were consistent with the influence of pH on the zeta potentials of the biomass, indicating that the dominant binding mechanism is likely to involve electrical attractions.
Adsorption of H+, OH− and Background Electrolyte Ions on Alumina — Point of Zero Charge, Triple Layer Model (TLM) Parameters and Thermodynamic Parameters
Authors: Taiwei Chu , Jinzhou Du , Zuyi Tao
Published: July 2017

The surface charge σ0 on aqueous suspensions of alumina was measured as a function of pH in various NaNO3 concentrations and at different temperatures. The values of the point of zero charge (p.z.c.), pK1(int), pK2(int), pKNa+(int) and pKNO3–(int) for alumina suspended in NaNO3 solutions were obtained in the temperature range 17–45°C from potentiometrie titration data. The values of ΔS0 and ΔH0 of the dissociation equilibria and complexation equilibria were calculated from these equilibrium constants. Standard Gibbs energies, enthalpies and entropies for proton adsorption on alumina were also obtained. The surface charge σ0 on aqueous suspensions of alumina was measured as a function of pH and concentration of Ca(NO3)2 or Na2SO4 solution.
Surface and Catalytic Properties of γ-Irradiated Cr2O3/Al2O3 Solids
Authors: El-Shobaky G.A. , Ghozza A.M. , Mohamed G.M.
Published: July 2017

Two samples of Cr2O3/Al2O3 were prepared by mixing a known mass of finely powdered Al(OH)3 with a calculated amount of CrO3 solid followed by drying at 120°C and calcination at 400°C. The amounts of chromium oxide employed were 5.66 and 20 mol% Cr2O3, respectively. The calcined solid specimens were then treated with different doses of γ-rays (20–160 Mrad). The surface and catalytic properties of the different irradiated solids were investigated using nitrogen adsorption at −196°C and the catalysis of CO oxidation by O2 at 300–400°C.

The results revealed that γ-rays brought about a slight decrease in the BET surface area, SBET (15%), and in the total pore volume, Vp (20%), of the adsorbent containing 5.66 mol% Cr2O3. The same treatment increased the total pore volume, Vp (36%), and the mean pore radius, r̄ (43%), of the other adsorbent sample without changing its BET surface area. The catalytic activities of both catalyst samples were found to increase as a function of dose, reaching a maximum value at 80–160 Mrad and 40 Mrad for the solids containing 5.66 and 20 mol% Cr2O3, respectively. The maximum increase in the catalytic activity measured at 300°C was 59% and 100% for the first and second catalyst samples, respectively. The induced effect of γ-irradiation on the catalytic activity was an increase in the concentration of catalytically active sites taking part in chemisorption and in the catalysis of CO oxidation by O2 without changing their energetic nature. This was achieved by a progressive removal of surface hydroxy groups during the irradiation process.
Adsorption of p-Nitrophenol on Inshas Incinerator Ash and on the Pyrolysis Residue of Animal Bones
Authors: Daifullah Abd. El-Hakim , El-Reefy Sohir , Gad Hamdy
Published: July 2017

The potential use of (a) Inshas incinerator ash and (b) the pyrolysis residue of animal bones for removing p-nitrophenol (PNP) from aqueous solutions by adsorption has been investigated. The experimental results have been fitted to the Langmuir and Freundlich isotherms. The maximum adsorptive capacity of Inshas incinerator ash was found to be 116 mg/g and of the pyrolysis residue of animal bones to be 111 mg/g. The extent of removal was dependent on the pH and the temperature of the solution and on the type and mass of adsorbent employed. Desorption results indicated that not more than 15% of the adsorbed amounts of PNP are released from the loaded matrix into the bulk solution. The activation energy of the process was 5.67 kcal/mol which shows that the rate-controlling step is intraparticle diffusion.
Adsorption Characteristics of Humic Acids by Granular Activated Carbon
Authors: Lin S.H. , Lin C.M.
Published: July 2017

The adsorption of humic acids on granular activated carbon has been investigated. A commerically available humic acid and that extracted from the bottom sludge of a dam were employed in the studies. Both batch and continuous adsorption experiments were conducted. A simplified competitive adsorption model in conjunction with the Freundlich isotherm was employed to represent the batch multicomponent adsorption system and a homogeneous surface diffusion model utilized to describe the continuous adsorption system in a packed-bed column. The model parameters were obtained by best fit of the models to the experimental adsorption data. The results indicated that the liquid-phase mass-transfer resistance, surface diffusion coefficient and the amount of adsorption on the activated carbon decreased with increasing molecular weight of the humic acid. It was also found that the adsorption of humic acid on the activated carbon was primarily a surface diffusion-controlled process.
The Effect of Sulphur Dioxide on the Adsorption Properties of Activated Carbon towards Chloropicrin
Authors: Anstice P.J.C. , Alder J.F.
Published: July 2017

Sulphur dioxide is believed to be adsorbed on activated carbons in both physically and chemically bound states. Sulphuric acid and a variety of oxygenated and hydrated sulphur oxide species are believed to be present on humidified carbons exposed to sulphur dioxide. Samples of ASC/T impregnated carbons were exposed to sulphur dioxide mixtures in humid air at 80% RG and 22°C. The sulphur dioxide-loaded carbons were then exposed to chloropicrin challenge at 5 mg/dm3 in air at 80% RH and 22°C and the chloropicrin breakthrough times measured.

A relationship was found between the extra mass gain of the carbons (due to oxygen and water) with increasing sulphur dioxide loading, as predicted by other workers. The effect of sulphur dioxide loading on the chloropicrin breakthrough times was a gradual reduction to about one-third the time for unexposed carbon, with an adsorbed mass of sulphur dioxide equal to ca. 10% of the carbon mass in a 20 mm bed-depth filter.
Potential Use of Bone Charcoal in the Removal of Antimony and Europium Radioisotopes from Radioactive Wastes
Authors: Raouf M.W. Abdel , Daifullah A.A.M.
Published: July 2017

Bone charcoal has been shown to be a good sorbent for 124SbIII and 124SbV from liquid organic radioactive wastes and for the retention of 152EuIII from aqueous wastes. Physical sorption was suggested to be the main mechanism operating for radioantimony isotopes with appreciably higher fixation on the sorbent when loaded from the liquid organic radwaste. In contrast, chemisorption was postulated as the main operating mechanism for 152EuIII with a higher and irreversible fixation on bone charcoal from a neutral aqueous medium.
Surface and Catalytic Properties of NiO and Fe2O3 Solids
Authors: El-Aal A. Abd. , Ghozza A.M. , El-Shobaky G.A.
Published: July 2017

The surface characteristics, viz., the specific surface area SBET, the total pore volume Vp and the mean pore radius r̄, of NiO and Fe2O3 were determined from N2 adsorption isotherms conducted at −196°C for the different adsorbents preheated in air at temperatures in the range 300–800°C. The catalytic activities exhibited in CO oxidation by O2 on the various solids were investigated at temperatures varying between 150°C and 400°C. The effect of heating the NiO and Fe2O3 solids in CO and O2 atmospheres at 175–275°C on their catalytic activities was also studied.

The results showed that increasing the calcination temperature in the range 300–800°C resulted in a progressive decrease in the SBET value of NiO and Fe2O3. The computed values of the apparent activation energy for the sintering of the oxides were 71 and 92 kJ/mol, respectively. The sintering of NiO and Fe2O3 took place mainly via a particle adhesion mechanism.

The catalytic activity of NiO decreased progressively on increasing its calcination temperature from 300°C to 800°C, due to a decrease in its SBET value and the progressive removal of excess O2 which was present as non-stoichiometric NiO. This treatment also decreased the catalytic activity of Fe2O3. The decrease was, however, more pronounced when the temperature increased from 300°C to 400°C which was a result of the crystallization of the ferric oxide into the α-Fe2O3 phase. An increase in the calcination temperature for both oxides from 300°C to 800°C did not modify the mechanism of oxidation of CO by O2 over the various solids but rather changed the concentration of catalytically active sites. Heating NiO and Fe2O3 in CO and O2 atmospheres at 175–275°C modified their catalytic activities, with Fe2O3 being influenced to a greater extent than NiO.
A Study on the Interaction of FeCl3 with Montmorillonite Suspensions
Authors: Chen Guangming , Han Buxing , Yan Haike
Published: July 2017

Calorimetric and static techniques were employed to study the interaction of FeCl3 with sodium montmorillonite in dilute aqueous suspension. The results show that the amount adsorbed and the adsorption enthalpy are strong functions of the pH and temperature. The adsorption mechanism was discussed on the basis of the experimental data.
A Modified BET Equation for Polylayer Adsorption
Authors: Kats B.M. , Kutarov V.V.
Published: July 2017

A three-parameter equation was obtained in the BET theory framework taking into account the correction suggested by the authors. This equation allows the description of adsorption isotherms in the range of polylayer adsorption as well as in the range of cluster formation. This equation was demonstrated as true for a number of adsorption systems in the relative pressure range 0.05 ≤ x ≤ 0.97 for nitrogen, benzene and water vapour.
Ion Capacity of Siliceous Sorbents with Surface Polymer Layers Composed of Different Dextran—Triethylenetetraamine Mixtures (Ion Capacity of Sorbents with Surface Polymer Layers)
Authors: Dawidowicz Andrzej L. , Wianowska Dorota , Pikus Stanislaw , Kobylas Elżbieta , Radkiewicz Stanislaw
Published: July 2017

The formation of a polymer layer on the surface of a siliceous support employed for chromatography is one of the methods available for protecting the silica skeleton from dissolution in the mobile alkaline phase and for eliminating the negative influence of silanol groups on separated molecules. A polysaccharide-polyimine copolymer can play the role of the surface layer, especially in siliceous materials, for high performance affinity chromatography. The results presented here demonstrate the utility of the material with such a copolymer layer as a sorbent for metal ions. The ion capacity of sorbents with a copolymer layer composed of triethylenetetraamine-dextran can be changed both by the composition of the mixture and by the amount of crosslinking agent present. The presence of a transition layer on the polymer layer surface explains the distinctions between the ion capacity of sorbents and the concentration of electron-donor nitrogen atoms existing in the material.
Porous Structure and Surface Chemistry of Active Carbons
Authors: Dubinin M.M. , Polyakov N.S. , Petukhova G.A.
Published: July 2017

The adsorbability on active carbons of substances with different physicochemical properties has been investigated and a comparative analysis of the pore structure parameters of the active carbons as estimated from the sorption of substances with various molecular diameters has been made. The influence of the surface chemistry of carbon sorbents on the adsorption of water vapour has also been studied. The need for a quantitative analysis of the pore structure parameters and the surface chemistry of active carbons as a basis for their universal characterization is discussed.
Dubinin–Radushkevich Equation as the Equation for the Excess Adsorption Isotherm
Authors: Serpinski V.V. , Jakubov T.S.
Published: July 2017

A modified Dubinin–Radushkevich (D–R) equation is proposed for the excess adsorption isotherm. It is shown that the equation describes the experimental excess adsorption isotherm excellently over a very wide range of gas equilibrium pressures. An algorithm is presented for the convertion of measurable values of excess adsorption to absolute values.
Application of the Dubinin–Radushkevich Equation for Describing Adsorption from Solutions on to Various Carbons
Authors: Dabrowski A. , Nieszporek K. , Fekner Z. , Leboda R. , Garbacz J.K.
Published: July 2017

Dozens of papers have been published recently describing adsorption processes from solutions on to solid surfaces, but a certain lack of understanding of this problem is still observed. This article deals with the description of adsorption from binary solutions of non-electrolytes on to solids. This description covers adsorption both on homogeneous and heterogeneous surfaces from ideal and non-ideal liquid mixtures. Some important factors determining the adsorption process, i.e. the heterogeneity of the solid surface, interactions between the species in the bulk and surface phases, differences in molecular sizes of the adsorbate molecules, etc., have been discussed. The main attention has been focused on the Dubinin–Radushkevich equation and its application in the description of adsorption from solutions on to energetically, heterogeneous adsorbents. Numerous model calculations have been reported for this equation and several experimental systems have been analyzed. The application of the Dubinin–Radushkevich equation in characterizing liquid adsorption on to various carbons has been demonstrated.
The Characteristic Curve in Physical Adsorption
Authors: Bakaev V.A. , Steele W.A.
Published: July 2017

The concept of the characteristic curve in physical adsorption and the rule of its temperature invariance is traced from the potential theory of adsorption by Polanyi to the Frenkel–Halsey–Hill equation, the theory of volume filling of micropores by Dubinin et al. and the theory of adsorption on heterogeneous surfaces. A computer simulation of an irregular atomic configuration at the surface of amorphous carbon is presented. In the submonolayer region, the isotherms of argon adsorption simulated on that surface are shown to correspond to the Freundlich equation and are close to the experimental isotherms on a diamond dust sample. Simulated isosteric heats of adsorption are also reasonably close to the experimental data for argon on a real carbon black. The BET C constant for the simulated isotherm is lower than for the real isotherm on untreated carbon black. However, the isotherms at two temperatures can be described by one absolute isotherm of adsorption.