bluuebunny/crossref_metadata_2025 huggingface dataset:
Methylene Blue Sorption Equilibria on Hydroxylated Silica Surfaces as Well as on Carbon–Silica Adsorbents (Carbosils)
Authors: Yanishpolskii V.V. , Skubiszewska-Zieba J. , Leboda R. , Tertykh V.A. , Klischar I.V.
Published: October 2002

The adsorption properties of hydroxylated silica gel as well as carbon–silica adsorbents (Carbosils) containing 5 and 18 w/w% carbon, both treated hydrothermally (with hydrogen peroxide solution) (HTT samples) and untreated, towards Methylene Blue (MB) were compared. The equilibrium adsorption of MB solutions of 6.5–7.0 × 10−4 mol/l concentration and its dependence on pH were studied. At this concentration, ca. 30% of the adsorbent surfaces investigated were covered with MB molecules under optimal adsorption conditions. The presence of carbon deposits on the silica surface did not lead to a decrease in the adsorption capacity of Carbosils relative to that of hydroxylated silica. However, such deposits increased the resistance of the adsorbent towards the action of alkalis. Oxidation of the carbon deposit in the HTT process caused a further increase in this resistance. Hence, the adsorption mechanism of MB at equilibrium in individual systems of the type investigated can differ significantly. On the one hand, this mechanism is associated with the differing behaviour of silica over a wide range of pH relative to treated and untreated Carbosils and on the other hand with the specific properties of MB.
Study of Chromium(VI) Adsorption from Aqueous Solution on to Activated Carbon
Authors: Dobrowolski Ryszard , Stefaniak Elżbieta
Published: October 2002

The adsorption of chromium(VI) from dilute aqueous solutions on to activated carbons at natural pH values was investigated. The activated carbons were modified to obtain materials with a well-defined surface containing inorganic impurities at ppb or ppm level. Measurements of the adsorption kinetics relative to the degree of granulation were undertaken. It was found that the reaction rate of the ions on the surface of the activated carbon rather than diffusion was the major process influencing the equilibrium. Surface reduction of CrVI to CrIII appeared to be the principal mechanism for the adsorption of chromium on the activated carbons studied. It was demonstrated experimentally that the presence of oxidizing agents dramatically changed the adsorption capacity of CrVI on the studied carbons. The influence of the ionic strength (controlled by the addition of NaCl) on the adsorption capacity was also studied. Variable and complex influences of the ionic strength on the adsorption capacity were observed.
Biosurfactant-Enhanced Remediation of Oil-Contaminated Environments
Authors: Shulga A. , Karpenko E. , Vildanova-Martsishin R. , Turovsky A. , Soltys M.
Published: October 2002

The development of new efficient cleaning technologies for the bioremediation of the environment and its cleaning from oil products has become a subject of great interest. Surfactants influence the bioremediation of oil and other organic contaminants through increasing their availability. Since surfactant products of a microbial nature are highly efficient in this respect, they have important advantages over synthetic materials. Being biodegradable, they are ecologically safe.

A new washing bioremedy based on surfactant products synthesized microbially from the bacterial strain Pseudomonas sp. PS-17 has been obtained. It contains an unique biocomplex of a glycolipid biosurfactant and an alginate biopolymer and possesses a high surface and emulsifying activity. The washing and antisorptional capacity of this bioremedy has been tested on objects of various natures, viz. bird feathers, animal skins and furs. We have obtained positive results in the remediation of sea sands, birds and animals suffering from ecological catastrophy. It was shown that the bioremedy has mild properties and does not change the structure of the feathers, skins and furs studied. The bioremedy remains active over the temperature range 15–90°C.
Relationship between Stationary and Mobile Phase Composition and its Influence on the Retention Time of Some Analytes in Gas Chromatography
Authors: Nasuto R.
Published: October 2002

A binary methanol vapour/hydrogen gas mixture has been used as the mobile phase in gas chromatography. Through the use of modified frontal analysis (undertaken just before measurements of the retention of the tested analytes), it has been possible to determine the adsorption isotherm of the mobile phase modifier (methanol) under typical conditions for a chromatographic process. It was found that adsorption of the mobile phase modifier on the column packing surface caused a decrease in the retention times of all the analytes tested. Furthermore, as a result of such adsorption, an increase in the degree of hydrophobization of the column packing surface also occurred, leading to a decrease of the selectivity of the packing.
Chemisorption and the Distribution of Acid Y Zeolite Cumene Cracking Products
Authors: Patrylak Lyubov
Published: October 2002

The results obtained for the pulse cracking of cumene in the presence of zeolite-containing acidic catalysts were analyzed taking into account data complications arising because of the chemisorption of the components of the reaction mixture on the acid sites of the catalyst samples. The propene/benzene (P/B) molar ratios in the reaction mixtures, which amounted to 0.60–2.7, deviated considerably from the expected stoichiometry depending on the nature of the samples, their mode of preparation, their preliminary thermal treatment and steaming as well as on the experimental conditions employed. At the same time, the total yields of cracking products and non-converted cumene were, as a rule, 1.5–3-times less than the amounts of cumene fed into the system.

The infringement of the stoichiometry and the considerable material imbalance observed may be attributed to the chemisorption of both cumene and the final conversion products on Lewis acid sites, i.e. coordinatively unsaturated aluminium atoms and zeolite cations, present on the catalyst surface. Chemisorption of the intermediates — phenyl carbocations — on Brönsted acid sites, as well as coke formation as a result of propene polymerization on these sites, must also be taken into consideration. The balance between these various processes and interactions leads to the overall reaction situation observed, thereby enabling conclusions to be drawn regarding both the nature of the catalyst surface and the individual processes, which appear to depend on the strength, amount and correlation between the Brönsted and Lewis acid sites on the samples studied.
Some Physicochemical, Surface and Catalytic Properties of the MoO3/Al2O3 System
Authors: Amin Nabil H.
Published: October 2002

The effects of MoO3 doping on the solid–solid interactions, surface and catalytic properties of Al2O3 solid were investigated using DTA, TG and XRD methods, N2 adsorption at −196°C and the catalytic conversion of isopropanol at 150–400°C using a flow technique under atmospheric pressure. The nominal composition of the mixed solid was 0.5MoO3:Al2O3. Pure and Mo oxide-treated solids were subjected to thermal treatment at 500–1000°C prior to surface and catalytic measurements.

The results showed that the Al2O3 support material when precalcined at 500°C exhibited the highest catalytic activity and selectivity towards isopropanol conversion (100% selective towards propylene formation). Moreover, loading MoO3 on Al2O3, followed by precalcination at 500°C, resulted in the formation of an active catalyst towards dehydration and dehydrogenation, especially for the reaction carried out below 200°C. Further increase in the precalcination temperature of Al2O3 from 500°C to 900°C resulted in a dramatic decrease in its dehydration activity due to the decrease in its surface area and surface acidity. The solids precalcined at 1000°C showed a maximum dehydrogenation activity for the catalytic reaction when the latter was carried out at 400°C.
Comparative Study of the Theoretical Predictions of Mixed-Gas Adsorption Equilibria from Pure Component Adsorption Data: Vacancy Solution Theory
Authors: Nieszporek K.
Published: October 2002

Simple methods for describing mixed-gas adsorption equilibria based on a knowledge of single gas adsorption are still needed for gas separation processes. The present paper describes the possibilities of the Vacancy Solution Theory (VST) approach. The VST predictions are compared with results obtained using the IAS, IE and PT approaches as presented earlier by the author.
Adsorption of Biologically Active Compounds from Aqueous Solutions on to Commercial Unmodified Activated Carbons
Authors: Terzyk Artur P.
Published: October 2002

The paper describes work associated with the continued investigation of the adsorption of paracetamol from aqueous solution at neutral pH. Using previously described carbons, some additional measurements, i.e. FT-IR spectroscopy and XPS, were performed to characterise the chemical composition of the surface. The results of batch-reactor-test kinetic measurements performed at different temperatures (300, 310 and 320 K) are presented and were described using two simple equations. The influence of carbon sieving and surface acidity on the kinetics of paracetamol adsorption is also discussed. The values of the diffusion coefficients (De) were calculated and a mechanism of diffusion is proposed. It is shown that if carbon samples possess a similar porosity, the values of De for paracetamol are higher for diffusion in the pores of the material possessing a more hydrophilic surface, i.e. for that carbon for which the higher value of the enthalpy of immersion in water was obtained.
Equilibrium Benzene Adsorption by Macroreticular Resins in a Countercurrent Multistage Process: A Research Note
Authors: Lin S.H. , Huang C.Y.
Published: October 2002

Experiments were conducted to investigate the equilibrium adsorption of benzene by macroreticular resins. Also tested was the adsorption of benzene by macroreticular resins in a countercurrent multistage adsorption process. The experimental data were employed to verify the theoretical predictions by mass balance equations. The test results indicated that a considerable saving in the amount of adsorption resin may be achieved under most circumstances in a multistage adsorption process in achieving the same extent of organic compound removal as in the single-stage process.
Activated Carbon Fibre Adsorbent Materials
Authors: Osmond Neale M.
Published: October 2002

A review discussing the production, chemical modification and application of activated carbon fibre (ACF) adsorbent materials.
Studies on H2S Adsorption and Carbon Deposition over Mo-Ni/Al2O3 Catalysts
Authors: González Maria G. , Ponzi Esther N. , Ferretti Osmar A. , Quincoces Claudia E. , Marecot P. , Barbier J.
Published: October 2002

The influence of molybdenum on the CO2 reforming of methane, simultaneous sulphur poisoning and carbon formation over alumina-supported Ni catalysts was studied. A series of Ni/Al2O3 catalysts modified by Mo was prepared to enable the effect of molybdenum content on H2S adsorption and the catalytic properties of the solids to be studied. The atomic Mo/Ni ratio in such catalysts varied in the range 0.01–1.00 while the Ni content was maintained constant at 3.3%. The catalysts were characterized by TPR, hydrogen adsorption and TEM methods. The H2S adsorption capacities of the catalysts were determined at 923 K employing a mixture consisting of 50 ppm H2S in a hydrogen stream. The results obtained indicate that the Mo promoter had a very favourable influence on the sulphur resistance of the Ni-based catalyst and led to a reduction in the rate of carbon deposition and the formation of graphitic species over the same.
Surface and Catalytic Properties of MoO3-Treated Co3O4/Al2O3 Solids
Authors: Ghozza A.M. , El-Shobaky G.A. , Mohamed G.M.
Published: October 2002

The surface and catalytic properties of Co3O4/Al2O3 solids treated with different proportions of MoO3 were investigated, the extent of MoO3 added varying between 0.50 mol% and 5.00 mol% (0.63–5.9 wt%). The pure sample was prepared by thermal decomposition at 600°C of aluminium hydroxide impregnated with a calculated amount of Co(NO3)2 dissolved in the least amount of distilled water. The MoO3-treated samples were prepared by thermal decomposition at 600°C of aluminium hydroxide treated with different proportions of ammonium molybdate followed by treatment with Co(NO3)2 solution.

The crystalline phases produced by thermal treatment of the pure and treated samples precalcined at 600°C were characterized using an XRD technique. The surface and catalytic properties of the various catalysts were studied using nitrogen adsorption at −196°C and CO oxidation by O2 at 100–150°C.

The results obtained revealed that molybdena treatment of the Co3O4/Al2O3 solids followed by precalcination at 600°C resulted in a decrease in the degree of crystallinity of the Co3O4 phase produced. This treatment effected a progressive small increase in the specific surface area of the treated solids (ca. 10%). However, the catalytic activity was found to be increased considerably by increasing the amount of MoO3 added (184%), reaching a maximum limit at 1.00 mol% MoO3.

The activation energies of the catalytic reaction calculated for both the pure and MoO3-treated solids suggested that MoO3 treatment did not modify the energetic nature of the active sites (surface cobalt species) but increased their concentration.
The Kinetic Parameters of Carbonaceous Materials Activated with Potassium Hydroxide
Authors: Yong Zou , Bu-Xing Han
Published: October 2002

On the basis of micropore formation in carbonaceous materials, the activation energy for the potassium hydroxide activation of Chinese petroleum coke and coal has been deduced theoretically as dB0/dt = A exp(–Ea∈/RT), where ∈ is the formation energy for the metastable solid formed at the activation temperature. The kinetic parameters (frequency factor, A, and apparent activation energy, Ea) were calculated from this equation as being 5.319 mg/(g min), 36.51 kJ/mol and 6.64 mg/(g min), 49.46 kJ/mol, respectively, for the two carbonaceous materials studied.
The Non-Ideality of the System Benzene + 1,2-Dichloroethane Adsorbed in Microporous Carbons at 293 K
Authors: Stoeckli F. , Couderc G. , Lavanchy A. , Wintgens D. , Girardin P.
Published: October 2002

In the case of simple vapour mixtures adsorbed by active carbons, the activity coefficients seem to depend essentially on the composition of the adsorbed phase, rather than on the degree of micropore filling. Consequently, the liquid–solid adsorption equilibrium of benzene + 1,2-dichloroethane mixtures has been investigated at 293 K, using a typical active carbon and following earlier work for adsorption from the vapour phase. This system has the advantage that the mixture is ideal in the liquid state, which provides a convenient reference for the study of the adsorbed phase. The activity coefficients, as well as the excess enthalpy of immersion of the carbon into the liquid mixtures, provide information on the modifications in the adsorbed state with respect to the ideal mixture. It is also shown that the introduction of the activity coefficients derived from the solid–liquid equilibrium increases considerably the accuracy of the Myers–Prausnitz–Dubinin model for the adsorption of the vapour mixtures.
Γ-Al2O3-Supported XMo6 Anderson Heteropolyoxomolybdates: Adsorption Studies for X = TeVI, AlIII, CoIII, CrIII and NiII by DR Spectroscopy and TPR Analysis
Authors: Cabello Carmen I. , Botto Irma L. , Cabrerizo Franco , González Maria G. , Thomas Horacio J.
Published: October 2002

The support–overlayer adsorptive interactions, generated when solutions of Anderson heteropolyoxomolybdates were supported as a monolayer on γ-Al2O3 by means of the equilibrium adsorption method, were studied by XRD analysis, DR spectroscopy, electron microscopy (SEM–EDAX) and TPR methods. The adsorption isotherms and corresponding adsorption parameters (number of active sites and adsorption constants) of the γ-Al2O3-supported ammonium heptamolybdate were obtained and discussed. The following sequence of adsorption strength was suggested: CoMo6 > CrMo6 > TeMo6 ~ AlMo6 > NiMo6. The effectiveness of the TPR technique as a tool for elucidating interaction effects was clearly demonstrated. The formation of a γ-Al2O3-supported Te–Mo mixed valence oxide appears to provide new and interesting catalytic possibilities.
The Influence of Carrier on the Critical Phenomena in CO Oxidation over NiO
Authors: Yatsimirsky Vitaly K. , Budarin Vitaly L. , Diyuk Vitaly Y. , Matzui L.Y. , Zacharenko M.I.
Published: October 2002

The influence of thermo-exfoliated graphite (TEG) on the catalytic activity of nickel in the CO oxidation process has been investigated. It was shown that nickel supported on the thermo-exfoliated graphite surface was more active catalytically than the bulk metal. Alternate oxidation–reduction on the Ni–NiO phase boundary occurred at temperatures higher than 633 K (Curie temperature of pure nickel). Using a magnetogravimetric method, it was found that the nickel catalyst was transformed by the reaction mixture into a heterophase (Ni/NiO) system both in the presence of a carrier and in its absence. Hence the carrier did not influence the size of the Ni particles. The high catalytic activity of the catalyst supported on graphite may be explained by an increase in the number of Ni particles. Ni/TEG and Ni/NiO samples were studied via X-ray diffraction, Auger spectroscopy and electron microscopy methods.
Studies of the Separation of Nitrate Complexes of Samarium(III) from Neodymium(III) in the C2H5OH-7 M HNO3 System on the Strongly Basic Anion Exchanger Wofatit SBW
Authors: Hubicki Z. , Olszak M.
Published: October 2002

The application of frontal analysis for the purification of SmIII from NdIII in aqueous nitric acid/alcohol medium was studied. This problem was investigated by purifying quantities of samarium(III) from 1% neodymium(III) in the Ln(NO3)3–90% v/v C2H5OH-10% v/v 1 or 7 M HNO3 system (concentration ca. 5.231 g Ln2O3/dm3) on strongly basic anion exchangers with different degrees of crosslinkage. The anion exchangers studied can be categorized in terms of their order of applicability: thus, in the system 90% v/v C2H5OH-10% v/v 1 M HNO3, Lewatit MP 5080 > Wofatit SBW × 8% DVB > Wofatit SBW × 6% DVB > Wofatit SBW × 12% DVB ≥ Wofatit SBW × 4% DVB ≥ Wofatit SBW × 7% DVB > Wofatit SBW × 2% DVB > Wofatit SBW × 16% DVB, whilst in the system 90% v/v C2H5OH-10% v/v 1 M HNO3, Lewatit MP 5080 > Wofatit SBK × 7% DVB ≥ Wofatit SBW × 6% DVB ≥ Wofatit SBW × 4% DVB > Wofatit SBW × 8% DVB ≥ Wofatit SBW × 2% DVB ≥ Wofatit SBW × 12% DVB = Wofatit SBW × 16% DVB. The most effective results were obtained with the anion exchanger Lewatit MP 5080. Using a 1 dm3 bed of this anion exchanger, it was possible to purify 0.2 kg Sm2O3 and achieve a decrease in its neodymium content from 1% to < 0.001%.
Catalytic Decomposition of H2O2 on Co3O4 Doped with Ag2O or ZnO
Authors: El-Shobaky Gamil A. , Turky Abd. El-Mohsen M.
Published: October 2002

The effects of doping Co3O4 with Ag2O (0.40–3.00 mol%) or ZnO (0.75–6.00 mol%) on the surface and catalytic properties of the solid were investigated via nitrogen adsorption at −196°C and the decomposition of H2O2 at 30–50°C. Pure and doped samples were prepared by the thermal decomposition in air at 500–900°C of pure cobalt carbonate and carbonate samples treated with different proportions of silver or zinc nitrates. The results showed that Ag2O doping followed by precalcination at 500–900°C resulted in a significant decrease (ca. 25%) in the BET surface areas of the treated Co3O4 samples. Treatment of Co3O4 with ZnO followed by precalcination over the same temperature range effected a corresponding increase in the specific surface areas (ca. 28%). The addition of Ag2O to Co3O4 effected a record increase in the corresponding catalytic activity towards the decomposition of H2O2. Thus, the maximum increase noted in the catalytic rate constant (k) measured at 30°C over Co3O4 doped with 3.00 mol% Ag2O exhibited a 36-fold, 26-fold and 3.5-fold increase for catalysts precalcined at 500°C, 700°C and 900°C, respectively. Treatment of Co3O4 with ZnO also effected an increase in the catalytic activity of the resulting solid. Thus, treatment of Co3O4 with 6.00 mol% ZnO followed by precalcination at 500°C, 700°C and 900°C effected an increase of 109%, 28% and 36%, respectively, in the catalytic activity expressed in terms of the reaction rate constant measured at 30°C. The doping process did not modify the activation energy of the catalyzed reaction but increased the concentration of catalytically active constituents considerably without changing their energetic nature. Doping with Ag2O or ZnO led to an increase in the concentration of Co3+–Co2+ ion pairs in the system and also generated corresponding Ag+–Co2+ and Zn2+–Co3+ ion pairs, thereby increasing the number of active constituents involved in the catalytic decomposition studied.
The Effects of Li2O Doping on the Surface and Catalytic Properties of CuO/Al2O3 Solids
Authors: El-Shobaky Gamil A. , Radwan Farouk M. , Turky Abd. El-Mohsen , El-Moemen Ayman Abd.
Published: October 2002

The effects of doping CuO/Al2O3 solids with Li2O on their surface and catalytic properties were investigated using nitrogen adsorption at −196°C, the decomposition of H2O2 at 20–40°C and the oxidation of CO by O2 at 175°C. The pure solids were prepared by wet impregnation of finely powdered solid Al(OH)3 which had been precalcined at 400°C; the resulting material was then dried and calcined at 500°C with copper nitrate dissolved in the least amount of distilled water. The amount of copper oxide in such solids was fixed at 13.5 wt% while the amounts of Li2O added varied between 0.19 wt% and 3.80 wt%.

The results obtained showed that such Li2O doping enhanced the crystallization of the CuO phase to an extent proportional to the amount of dopant added and increased the concentration of surface OH groups. This treatment led to a progressive small increase in the BET surface areas (SBET) of the treated solids, which attained a maximum limit at 0.76 wt% Li2O but decreased upon increasing the dopant concentration above this limit. The addition of 0.76 wt% Li2O effected an increase of 14.6% in the SBET values of the treated solids while the addition of 3.80 wt% Li2O led to a corresponding decrease of 38.5% in this value.

Doping with Li2O resulted in a progressive decrease in the catalytic activity of the solids towards CO oxidation by O2 while the presence of 3.80 wt% Li2O effected a decrease of 72.5% in the value of the reaction rate constant measured at 175°C. In contrast, such treatment of CuO/Al2O3 solids with Li2O brought about a progressive increase in their catalytic activity towards H2O2 decomposition, which reached a maximum limit in the presence of 1.90 wt% Li2O and then decreased when the amount of Li2O added was increased above this limit, falling to values which were smaller than those measured for the pure catalyst samples.

The doping process did not modify the activation energy of the catalyzed H2O2 reaction but modified the concentration of the catalytically active constituent present in the system.
Peculiarities in the Hydration of Cellulose in Air and Water Suspensions as Studied by 1H NMR Spectroscopy
Authors: Shulga O.V. , Dollimore D. , Turov V.V.
Published: October 2002

Bound water layers in hydrated powders and aqueous suspensions of microcrystalline cellulose were investigated by 1H NMR methods. The characteristics of such layers were calculated and the magnitude of the interfacial energy (γs) at the cellulose/water interface in an aqueous environment determined. It was found that the concentration of strongly bound water and the value of γs were strongly dependent on the concentration of cellulose in suspension. This is probably due to the strong interaction between cellulose particles. At very high suspension concentrations, the concentration of water inside the cellulose filament decreased by more than three-times while the value of γs decreased from 31 J/g to 9 J/g as a result of surface forces.
Studies of H+-Mg2+ and H+-Ca2+ Exchanges on Acrylic Carboxylic Cationites from the Viewpoint of the Exchange Equilibrium Theory
Authors: Mamchenko A.V. , Valuiskaya E.A. , Klimova G.V.
Published: October 2002

The sorption of Mg2+ and Ca2+ ions by the H-form of the acrylic carboxylic cationite Lewatit CNP 80 as the magnesium sulphate or calcium chloride concentration in the external solution was varied by two orders of magnitude has been considered from the viewpoint of the ion-exchange equilibrium theory. The experimental data were obtained using a method which provided high precision measurements of the potentiometric titration curve over a wide range of resinate compositions for the ionite gel phase. The strong dependence of the effective equilibrium constant on the resinate solution composition was described satisfactorily by the exchange equilibrium theory. The selectivities towards Ca2+ and Mg2+ ion sorption by the H-type of carboxylic cationite studied were close. An explanation for this phenomenon was proposed.
The History and Present State of Dubinin's Theory of Adsorption of Vapours and Gases on Microporous Solids
Authors: Kadlec Ondřej
Published: October 2002

The famous Russian scientist Mikhail Mikhailovich Dubinin had a substantial influence on the state of the present theory of physical adsorption of vapours and gases on microporous solids. He was born in Moscow on the first day of the 20th century and had the good fortune to be active in surface science — an extremely interesting branch of physical chemistry — during the period of its rapid development from his 20th year up to the last days of his long and fruitful life in 1993. As a student at Charles University, the author of the present article had the good fortune to become acquainted with Dubinin during the latter's first visit to Prague in May 1955 and later to be involved in extensive scientific contact with him up to the last days of his life. The author feels that he has a moral duty to record for readers of Adsorption Science & Technology not only some historically important features of the development of the universal theory of adsorption of vapours on microporous solids but also an explanation of the present state of this theory.
Preparation of Activated Carbons from Chinese Coal and Hydrolysis Lignin
Authors: Zou Yong , Han Bu-Xing
Published: October 2002

Activated carbons from Chinese coal and Chinese hydrolysis lignin have been prepared by chemical activation with potassium hydroxide. The following aspects of these activated materials have been analyzed: raw material; pre-treatment of raw material; activation agent, activation temperature and time, and the activation agent/raw material ratio. Activated carbons with BET specific surface areas of the order of 2400–2600 m2/g which exhibited substantial microporosity, a total pore volume of over 1.30 cm3/g and a Methylene Blue adsorption capacity of over 440 mg/g were obtained.
Influence of Magnetic Fields on Adsorption and Ion Exchange from Aqueous Solutions
Authors: Baran B.A.
Published: October 2002

The influence of magnetic fields on the adsorption of some dyes and other substances from aqueous solution by activated carbon was studied. In a similar manner, the influence of magnetic fields on barium ion sorption by some zeolites from ordinary (H2O) and heavy (D2O) water was investigated. The data obtained suggest that the presence of a magnetic field decreases the hydrogen bonding energy between water molecules.
A New Way to Increase Catalyst Activity
Authors: Glikin M.A. , Kutakova D.A. , Glikina I.M. , Volga A.I.
Published: October 2002

A new method for conducting a heterogeneous catalytic reaction in the gaseous phase is discussed. It eliminates the use of carriers and allows catalysis to be conducted via an aerosol of finely milled active catalytic materials. Problems associated with the strength and thermal stability of catalysts are thereby avoided. A high and constant catalytic activity is ensured for the aerosol catalyst by integrating the chemical reaction zone and the mechanical treatment zone. Thus, solid particles that move with the reactant flow or special devices that allow mechanical treatment of the catalyst particles may be located in the reactor. Such aerosol catalysis has been tested in processes involving partial and complete oxidation, recovery, vinylation, chlorination and dechlorination. Relative to traditional systems, i.e. placement of the active catalytic active material on the carrier, the reaction rate was increased by 4–5 orders of magnitude. The production of catalysts and the implementation of chemical reactions are thereby both simplified simultaneously.
Effect of MgO Addition on the Surface and Catalytic Properties of the CuO/Al2O3 System
Authors: Deraz Nasr-Allah M.
Published: October 2002

The effect of MgO on the solid–solid interactions, surface and catalytic properties of CuO/Al2O3 solids was investigated using XRD methods, nitrogen adsorption at −196°C and oxidation of CO by O2 at 150–300°C. The nominal composition of the pure mixed solid was 0.20CuO:Al2O3 and the amounts of MgO added varied between 0.43 wt% and 3.30 wt%. The pure and MgO-treated solids were subjected to precalcination (thermal treatment) at 600°C and 800°C, respectively.

The results obtained revealed that CuO underwent solid–solid interactions with pure and doped alumina at temperatures of 600°C and above to yield a poorly crystalline copper aluminate (CuAl2O4) phase. The amount of copper aluminate produced increased on increasing the precalcination temperature to 800°C. Magnesium oxide inhibited the formation of CuAl2O4 at 600°C but enhanced this reaction at 800°C, the inhibiting and enhancing effects depending on the amount of MgO present. Doping with MgO effected a measurable increase in both the specific surface areas and catalytic activities of the solids precalcined at 600°C. The reverse effect was observed for the doped solids preheated in air at 800°C. Doping at 600°C and 800°C modified the concentration of catalytically active constituents involved in chemisorption and catalysis of the CO oxidation reaction.
Elimination of Odours from the Gaseous Phase on CrIII- and FeIII-modified Y-type Zeolites
Authors: Sarbak Zenon
Published: October 2002

Modified NaY-type zeolites, in which a portion of the sodium ions had been exchanged for chromium(III) or iron(III) ions, were studied as adsorbents. The modified zeolites were tested with respect to the adsorption of n-butylamine or n-butylthiol via the pulse method employing a column micro-adsorber directly attached to a gas chromatograph. Thus, 200 mg portions of the adsorbent were activated by heating at 400°C for 2 h after which the temperature was decreased to 200°C. The column was held at this temperature for 1 h and then 10 μl portions of n-butylamine and n-butylthiol were injected on to it at 15-min intervals. It was found that the zeolites containing iron(III) ions were much more effective as adsorbents (by 30%) than those containing chromium ions, with this difference reaching 60% in the case of n-butylthiol. Furthermore, zeolites containing iron(III) ions underwent much less deactivation than those with chromium(III) ions. Increasing the iron → sodium or chromium → sodium ion exchange led to increased adsorption of the organic compounds studied. It was shown that Y-type zeolites modified with iron(III) are effective adsorbents for deodorising atmospheric air.
Adsorption of Tributyl Phosphate on Silica Gel
Authors: Sazonova V.F. , Kojemyak M.A. , Perlova O.V.
Published: October 2002

The adsorption behaviour of tributyl phosphate (TBP) on silica gel was studied. It was found that the adsorption isotherm shapes were complicated, being considered as S- and L-type isotherms according to the Giles classification. Adsorption itself was polymolecular and of a physical nature, the first adsorptive layer involving hydrogen bonding between the protons of surface silanol groups and the electron-donating oxygen atom of the adsorbate molecule. Subsequent adsorption layers were formed via van der Waals interaction. The free energy of adsorption of the system lay between −22.1 kJ/mol and −23.8 kJ/mol. The enthalpy change was negative and very small, i.e. −6.3 kJ/mol, while the entropy change was positive and in the range 53.9 J/(mol K) to 55.4 J/(mol K). The increase in entropy was explained in terms of the mobility of the TBP molecules in the adsorptive layer arising from their replacement on the silica gel surface by water molecules derived from the aqueous medium.
Power Laws in Adsorption and the Characterization of Heterogeneous Substrates
Authors: Bulnes F. , Ramirez-Pastor A.J. , Zgrablich G.
Published: October 2002

The adsorption of particles with repulsive nearest-neighbour interactions was studied through Monte Carlo simulation on bivariate surfaces characterized by patches of weak and strong adsorbing sites of size l. Patches were either arranged in a deterministic chessboard structure or in a random way. Quantities were identified which scale obeying power laws as a function of the scale length l. The consequences of these findings were discussed for the determination of the energetic topography of the surface from adsorption measurements.
Adsorption of Dyes on Magnesium Hydroxide
Authors: Soldatkina L.M. , Purich A.N. , Menchuk V.V.
Published: October 2002

The basic adsorption regularities of water-soluble dyes (acid, direct and basic) on magnesium hydroxide were studied. The dyes were shown to be better adsorbed on magnesium hydroxide precipitated from an aqueous solution of magnesium sulphate than on magnesium hydroxide precipitated from aqueous solutions of magnesium chloride. It was demonstrated thermodynamically that magnesium hydroxide is an effective adsorbent of acid and direct dyes.
Influence of Palladium Crystallite Size on the Course of the DENOX Reaction
Authors: Ćwikła-Bundyra Wiesława , Nazimek Dobiesław
Published: October 2002

Catalysis is one of the important fields in the industry where small metal particles are applied. The effect of the metal crystallite size in the catalytic reduction process has investigated for palladium, the present paper reporting on the effect of the Pd dispersion on the course of the reaction between NO and CO. Such studies also allowed changes in the activity and selectivity of the process and the concentration of B5 sites on the surface of Pd catalysts to be traced.
Effect of Carbon Deposits on the Structure of Hybrid C/TiO2/SiO2 Adsorbents
Authors: Leboda R. , Gun'ko V.M. , Marciniak M. , Grzegorczyk W. , Skubiszewska-Zięba J.
Published: October 2002

The structural characteristics of pyrocarbon/X (X = fumed silica, mesoporous silica gel, fumed titania/silica, CVD-TiO2/fumed silica, CVD-TiO2/silica gel) prepared using several precursors [CH2Cl2, cyclohexene and TiO(AcAc)2, where Ac = acetylacetonate] were studied using the nitrogen adsorption/desorption method and an improved technique to allow the calculation of pore size distributions applying regularization procedures. Various pore models were used for the carbon phase. The pyrocarbon structure and distribution on the TiO2/SiO2 supports depends primarily on the structural features of the titania phase which exhibits catalytic activity in the pyrolysis of organic materials. The formation of relatively large concentrations of pyrocarbon typically reduces the porosity and specific surface area of the hybrid adsorbents produced.
A New Adsorption Isotherm for Heterogeneous Sorbents
Authors: Shkilev V.P. , Brei V.V.
Published: October 2002

An adsorption isotherm has been suggested for the intended description of the experimental isotherms for the adsorption of gases and vapours on heterogeneous surfaces. Two parameters of the suggested equation, which characterize the heterogeneity of a sorbent, were expressed in the form of explicit functions of temperature as well as of variance and the excess coefficient for the corresponding energy distribution of adsorption sites. The presence of such explicit expressions allowed the application of the suggested equation for the description of the dependence of the adsorption not only on pressure but also on temperature. The adsorption of N2 on TiO2 was considered as an example. It was shown that the suggested equation could be used as the thermal equation of state for a real adsorption system over quite wide ranges of temperature and pressure.
Studies of the Polar and Apolar Liquid Film Properties of Pure and Modified Activated Carbons by Thermal Analysis and Sorptiometric Methods
Authors: Głażewski Dariusz , Staszczuk Piotr , Leboda Roman
Published: October 2002

Thermal analysis was used to investigate the adsorbed water layers and surface properties of various pure and modified commercial activated carbons. In addition, the thermodesorption of n-butanol, n-octane and benzene from samples saturated in a vacuum desiccator was studied under quasi-isothermal conditions. The mass loss Q-TG and differential mass loss Q-DTG curves obtained consisted of steps and inflections which were associated with the mechanism of wetting, adsorption and porosity properties of the studied surfaces. Adsorption/desorption isotherms of nitrogen on the activated carbon samples were measured using a sorptiomatic method. The specific surface areas, pore sizes, pore volumes and pore-size distribution functions have been calculated for the various samples. A correlation between the porosity parameters obtained from thermogravimetric and sorptiometric methods is presented.
Physicochemical Study of ‘Dolomitic’ Sorbents Prepared under Different Thermal Conditions. Part III. The Influence of Carbon Dioxide Content over a Heated Sample
Authors: Stefaniak Ełżbieta , Biliński Bogdan , Dobrowolski Ryszard , Staszczuk Piotr
Published: October 2002

The physicochemical properties of ‘dolomitic’ sorbents formed through the partial decomposition of dolomite have been discussed in two papers published previously dealing with the influence of temperature and the time of heating. When carried out at 800°C, the newly formed solid consisted of spongelike calcite and finely powdered magnesium oxide which was resistant mechanically and exhibited considerably greater porosity than the raw material. Long-term heating led to a decrease in the porosity and to the partial elimination of pores. The corresponding ‘dolomitic’ sorbents prepared in an inert atmosphere showed even greater porosity and a different internal structure when compared to those formed in the presence of carbon dioxide. However, no changes were observed as far as the chemical composition was concerned.
Physicochemical and Catalytic Properties of Vanadia/Titania Catalysts. II. Textural Properties
Authors: El-Nabarawy Th. , Alaya M.N. , Ahmed S.A. Sayed , Youssef A.M.
Published: October 2002

Titania gels, Ta and Tb, were precipitated from aqueous solutions of titanium tetrachloride at pH values of 3.0 and 9.0, respectively. Calcination products were obtained from these gels by thermal treatment at 300–1000°C. Vanadia/titania catalysts were obtained by impregnating Ta and Tb with ammonium vanadate to give products containing 4–12 wt% V2O5. These products were calcined at 400°C or 600°C, respectively. The adsorption of nitrogen at −196°C was followed and the isotherms thus obtained analyzed to enable the determination of the textural characteristics of the catalysts through the use of conventional methods of textural analysis.

The specific surface area and total pore volume of titania decreased and its mean pore radius increased on increasing the calcination temperature from 400°C to 1000°C. Titania precipitated at pH 3.0 and calcined at 1000°C exhibited non-porous characteristics as indicated by the absence of hysteresis in the corresponding adsorption isotherm. The textural changes were attributed to the anatase → rutile transformation and also to the sintering of rutile.

The specific surface area and porosity of vanadia/titania catalysts changed with increasing calcination temperature and with increasing vanadia content. However, the effect of calcination temperature was more pronounced.
Catalytic Conversion of Ethanol and Isopropanol on γ-Irradiated Co3O4/Al2O3 Solids
Authors: Doheim M.M. , El-Boohy H.A. , El-Shobaky G.A.
Published: October 2002

The catalytic conversion of ethanol and isopropanol was conducted over Co3O4/Al2O3 solids (19.3 wt% Co3O4) precalcined at 400°C and subjected to different doses of γ-radiation. The reaction was studied at different temperatures in the range 250–400°C and monitored using nitrogen as a carrier gas flowing at a rate of 18 cm3/min. The γ-ray doses employed were 0.2, 0.4, 0.8 and 1.6 MGy, respectively.

The results obtained indicated that γ-irradiation effected a progressive decrease in the catalytic activity of the solids towards alcohol conversion, reaching a minimum value after 0.8 MGy irradiation. The irradiation process also effected a measurable decrease in the dehydration selectivity towards the alcohols investigated and an increase in their dehydrogenation selectivity. These results were discussed in terms of an effective decrease in the concentration of sites exhibiting Brönsted acidity brought about by γ-irradiation, which also generated a small decrease in the particle size of the Co3O4 crystallites and a measurable increase in the specific surface areas of the solids investigated.
Adsorption and Desorption of Radioiodine in a Calcareous Soil
Authors: Xiangke Wang , Wenming Dong , Zhijun Guo , Huibin Gao , Jinzhou Du , Zuyi Tao
Published: October 2002

The adsorption and desorption of radioiodine in a calcareous soil from Jiuquan County of Gansu Province (China) was studied using batch and column experiments. The adsorption and desorption isotherms and the breakthrough curves for the untreated soil and for soil treated to remove organic matter were determined at pH 8.1 and in the presence of CaCl2, respectively. It was found that radioiodine is a very mobile nuclide in calcereous soil, that the organic matter of the soil is the main component for the retention of radioiodine at very low concentration and that intra-organic diffusion of matter is the predominant rate-limiting step in the adsorption of the I− ion. It may be concluded that organic matter is a significant sink for radioiodine in calcareous soil.
Surface and Catalytic Properties of the γ-Irradiated ZnO-Treated Co3O4/Al2O3 System
Authors: Doheim M.M. , El-Boohy H.A. , Mokhtar M. , El-Shobaky G.A.
Published: October 2002

Pure and ZnO-doped Co3O4/Al2O3 catalysts were subjected to γ-irradiation (0.2–1.6 MGy). These catalysts were employed for the conversion of ethanol and isopropanol at 250–400°C using micropulse techniques. The results obtained showed that ZnO treatment increased the activity and selectivity towards dehydrogenation of the alcohols studied. On the other hand, γ-irradiation resulted in a progressive decrease in activity which fell to a minimum value at 0.8 MGy and then increased back to the original (unirradiated) value on increasing the dose further. γ-Irradiation of ZnO-treated catalysts also led to a decrease in their catalytic activity. However, in this case, the extent of such a decrease as a function of the dose applied decreased as the amount of ZnO in the catalysts increased up to 2.63 wt%. This finding was observed when the catalyzed reaction was conducted at 250–350°C, but the reverse trend was exhibited when the reaction was conducted at 350–400°C.
Determination of the Specific Surface Areas of Non-Porous and Macroporous Carbons
Authors: Choma J. , Jaroniec M.
Published: October 2002

The current work is focused on the examination of a new method for the determination of the specific surface areas of non-porous and macroporous carbons from gas adsorption isotherms. This method has rigorous foundations since it utilizes the adsorption potential distribution which is a unique thermodynamic characteristic for a given adsorption system. Nitrogen adsorption isotherms at 77 K for a series of low-surface area graphitized and non-graphitized carbons were used to examine this method and to compare it with the BET procedure. Additional testing was undertaken for argon, nitrogen and krypton adsorption isotherms at 87 K on a highly graphitized carbon. It was shown that surface area analysis based on the adsorption potential distribution is very promising for the characterization of various carbons.
The Diffusion of Chlorinated Hydrocarbons in Particles of Activated Carbon
Authors: Bobok Daniel , Besedová Eva
Published: October 2002

Computed values of the effective diffusion coefficient, De, ranging from 4.93 × 10−10 to 5.96 × 10−10 m2/s were obtained from kinetic data for the adsorption of 1,2-dichloropropane from a mixture with air on to activated carbon particles at concentrations within the range 14.94–31.51 g/m3. Such kinetic adsorption data were obtained over the temperature range 24.1–25.8°C. Using the dependence De = f(CA0), it was possible to compare the calculated values of De for 1,2-dichloropropane with the experimental data for 1,2-dichloroethane obtained from adsorption measurements. The values of the effective diffusion coefficients for 1,2-dichloropropane as calculated from its desorption by pure air were within the range 1.67 × 10−10–2.01 × 10−10 m2/s at temperatures of 24.0–24.2°C. The considerable difference between the values of the effective diffusion coefficient for 1,2-dichloropropane in activated carbon particles as estimated from adsorption and desorption data may be associated with the non-linear course of the adsorption isotherm.
Temperature Dependence of the Isosteric Heat of Adsorption
Authors: Cao D.V. , Sircar S.
Published: October 2002

Direct calorimetric measurements of the isosteric heats of adsorption of (a) pure CO2 on a strongly heterogeneous adsorbent (silicalite with an alumina binder) and (b) pure N2 on a mildly heterogeneous adsorbent (5A zeolite) at different temperatures and adsorbate loadings demonstrated the validity of the conventional assumption that isosteric heats are very weak functions of temperature. A simple thermodynamic model for the adsorption of a pure gas on an adsorbent containing two different energetic sites also validated the same assumption in the Henry's law region.
Adsorption of Aromatic Compounds by Activated Carbon: Effects of Functional Groups and Molecular Size
Authors: Nouri Sirous , Haghseresht Fouad , Lu Max
Published: October 2002

The adsorption of three aromatic compounds on to an untreated carbon was investigated. The solution pH was lowered in all experiments so that all the solutes were in their molecular forms. It was shown that the difference in the maximum adsorption of the solutes was mainly a result of the difference in the sizes of the molecules and their functional groups. Furthermore, it was illustrated that the packing arrangement was most likely edge-to-face (sorbate–sorbent) with various tilt angles. On the other hand, the affinity and heterogeneity of the adsorption systems were apparently related to the pKa values of the solutes.