Adsorption kinetics of hemoglobin onto silicate adsorbents

A comparative study was performed of the adsorption kinetics of hemoglobin onto four silicate adsorbents that differed in parameters of porous structure: industrial silochrome, and three silicates obtained by template synthesis. The existence of a reversible stage of the process preceding irreversible protein binding was shown by kinetic analysis. Rate constants for the reversible stage of the process and the effective constants of first order rate were calculated. It was concluded that the adsorption rate is the highest on silochrome and the lowest on silicate of MCM-41 type, the pore size of which is comparable to the diameter of a hemoglobin molecule. The constant of the desorption rate for the first reversible stage of the process was shown in the case of mesoporous silicates to be lower by a factor of 3.5–4 than in the case of silochrome.     

Adsorption properties of alumina

Summary Besides the three previously reported (3) surface species (i. e. outer, inner complex and a py⁺-species) which are formed on adsorption and desorption of pyridine on dehydroxylated alumina at temperatures above 200 °C, a fourth low temperature species is identified. The dependence of the surface concentrations of the various species and of the acid sites which they occupy is discussed usingPeris, surface model ofγ-Al₂O₃. It can be shown to be highly probable that the inner complex and the py⁺-species are formed solely on triplet oxide defects. These acid sites have to be distinguished with respect to there nearest neighbours. At least two types of triplet defects must be postulated; type A preferentially contains adjoined oxide ions and may possibly correspond toPeris α-sites, type B preferentially contains adjoined hydroxyl ions and therefore exhibits the higherLewis acidity. Whereas the py⁺species is formed on this latter type of triplet defect, outer and inner complexes presumably are formed on all types of triplet oxide vacancies.

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Zusammenfassung Au?er den früher beschriebenen (3) Oberfl?chenverbindungen (?u?erer und innerer Komplex und py⁺-Spezies), die bei der Adsorption und Desorption von Pyridin an dehydroxyliertem Aluminiumoxid bei Temperatur n oberhalb 200 °C gebildet werden. wird eine vierte Spezies bei Adsorption unterhalb 200 °C gefunden. Die Konzentrationsabh?ngigkeit der verschiedenen Spezies und der S?urezentren, an. denen sie gebildet werden, wird im Rahmen desPerischen Modells derγ-Al₂O₃-Oberfl?che diskutiert. Mit hoher Wahrscheinlichkeit werden der innere Komplex und die py⁺-Spezies ausschlie?lich an Dreifachdefekten gebildet. Diese S?urezentren müssen hinsichtlich der Art ihrer n?chsten Nachbarn unterschieden werden. Wenigstens zwei Typen von Dreifachdefekten müssen vorliegen, n?mlich Typ A-Zentren, die bevorzugt Sauerstoff ionen enthalten und m?glicherweise mitPeris α-Zentren verglichen werden k?nnen, und Typ B-Zentren, die bevorzugt Hydroxylgruppen enthalten und daher die h?here Acidit?t besitzen. Die py⁺-Spezies wird ausschlie?lich an den Typ B-Zentren gebildet, innerer und ?u?erer Komplex dagegen an beiden Arten von Dreifachdefekten.

     

Adsorption properties of nanoparticles

Scanning tunneling microscopy and spectroscopy, Auger spectroscopy, and mass spectrometry were used to study the physicochemical properties of nanoparticles of several metals and their oxides. The adsorption properties of the nanoparticles were determined for their interaction with hydrogen, oxygen, and nitrogen.     

Adsorption properties of lamellar silica

Isotherms and heats of adsorption of water, n-heptane, trimethylamine, and methanol (at 303 K) vapors and isotherms of adsorption of nitrogen (at 77 K) on the lamellar silica prepared by removing metals from natural mineral vermiculate were measured. The surface concentration of adsorption sites and their energetic characteristics were found to be similar to those of ordinary silicas. The distinction of the lamellar silica from ordinary silicas manifests itself through extended desorption branches, a feature that makes it possible to classify the lamellar silica under study as a limitedly swellable sorbent.     

Adsorption properties of membrane catalysts

A method for adsorption measurements on catalysts with small surface areas has been devised. The adsorption of argon has been examined on membrane catalysts made from Pd–Ni and Pd–Ru alloys before and after catalytic experiments. A sharp change of the adsorption properties and an increase in the surface areas of catalysts after reactions have been observed.

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. Pd–Ni Pd–Ru . - .

     

Adsorption properties of porous silicophosphate

Isotherms of low-temperature physical adsorption-desorption of nitrogen for silicophosphate samples obtained at pH of the sol-gel transition varied from 5 to 9 in the presence of a template (cetylpyridinium chloride) were measured. The isotherms obtained were reconstructed in the form of t-graphs. The parameters of the micro- and mesopore structure of the samples were determined.     

Adsorption properties of microporous silica

The study of CCl₄ adsorption shows that the increase of dispersion potential can increase the specific adsorption in pores up to 3 nm in size.

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CCl₄ , 3 .

     

Adsorption properties of ultradispersed diamonds

The adsorption capacity of ultradispersed diamonds for synthetic dyes and medicinal preparations was studied.     

Adsorption properties of GaAs-CdS system

The adsorption properties of GaAs-CdS solid solutions and the constituent binary systems with respect to CO and NH₃ were studies by piezoquartz microweighing, temperature-programmed desorption, and IR spectroscopy. On the basis of an analysis of the measured α _p = f(T), α _T = f(p), and α _T = f(t) dependences, the thermodynamic and kinetic characteristics of adsorption, earlier obtained acid-base and other physicochemical characteristics of adsorbents, and the electronic properties of the adsorbate molecules, the mechanism and regularities of the adsorption processes at various conditions and compositions of the system were established. A comparison of the adsorption properties of the GaAs and CdS individual binary compounds with their (GaAs)_x(CdS)_1?x solutions, multicomponent systems, revealed common and distinctive features. Optimal compositions of adsorbents suitable for manufacturing primary transducers in sensors for medical and environmental purposes were determined.     

Adsorption properties of thermally pretreated porasils

Summary A simple modification was employed by thermal or hydrothermal treatment of silica gel (Porasil). In this way chromatographic materials with advantageous properties were prepared. The changes of the adsorbent under different thermal and hydrothermal treatment were studied in more detail. The experimental results show that under controlled conditions material with required chromatographic properties can be prepared.     

Adsorption and catalytic properties of peroxidase

The adsorption of peroxidase was studied on ten silicate adsorbents, aluminosilicate, and alumina. It was shown that its value depended on both the parameters of the porous structure and the nature of the adsorbent. The maximum adsorption values were obtained on biporous silicate adsorbents and biporous aluminosilicate. It was established that the adsorbed peroxidase layers on these adsorbents had the best catalytic properties as well. It was shown that the specific activity of the enzyme depended on the degree of the surface filling.     

Adsorption properties of CdS-CdTe system semiconductors

The adsorption of carbon(II) oxide and ammonia on nanofilms of solid solutions and binary compounds of the CdS-CdTe system is studied by means of piezoquartz microweighing, FTIR IR, and measuring electroconductivity. Allowing for the conditions and composition of semiconductor systems, we determine the mechanisms and principles of adsorption processes by analyzing the α _p = f(T), α _T = f(p), and α _T = f(t) experimental dependences; IR spectra; the thermodynamic and kinetic characteristics of adsorption; the acid-base, electrophysical, and other characteristics of adsorbents; the electron nature of adsorbate molecules; and the obtained acid-base characteristics: the composition and adsorption characteristics and composition state diagrams. Previous statements on the nature and retention of local active centers responsible for adsorption and catalytic processes upon changes in their habitus and composition (as components of systems of the A^IIIB^V-A^IIB^VI and A^IIB^VI-A^IIB^VI types) on the surface of diamond-like semiconductors are confirmed. Specific features of the behavior of (CdS) _x (CdTe)_{1 ? x} solid solutions are identified in addition to general features with binary compounds (CdS, CdTe), as is demonstrated by the presence of critical points on acid-base characteristics-composition and adsorption characteristics-composition diagrams. On the basis of these diagrams, the most active adsorbents (with respect to CO and NH₃) used in designing highly sensitive and selective sensors are identified.     

Adsorption properties and surface chemistry of MgO

The adsorption properties of MgO, which is used as a sorbent and catalyst support, were studied using gas chromatography. The test absorbents used were n-alkanes (which show only nonspecific dispersion interactions when physisorbed on any adsorbent) and adsorbates whose molecules are capable of specific interactions with the surface reactive sites of MgO. Adsorption isotherms were measured for CHCl₃, CH₃NO₂, CH₃CN, (CH₃)₂CO, CH₃COOC₂H₅, and (C₂H₅)₂O on MgO at 50–100°C. Differential molar enthalpy changes (?ΔH), equal to molar heats of adsorption, were determined. For polar adsorbates, contributions from dispersive and specific interactions into ?ΔH were determined. The electron-acceptor and electron-donor abilities of the MgO surface were estimated.     

Adsorption properties of iodine-doped activated carbon fiber

Iodine-doped activated carbon fibers (ACFs) were prepared by the iodine immersion method on pitch-based ACF. Then iodine-doped ACFs were heated in argon at 523 K for 4 h and at 673 K for 2 h. The iodine structure of the resultant iodine-doped ACFs was examined using X-ray photoelectron spectroscopy. The micropore structures were determined by N(2) adsorption at 77 K. The surface area and micropore volume of iodine-doped ACFs are less than those of pristine ACFs. However, the pore width does not change with the iodine doping. The effects of iodine doping on adsorption properties of ACFs for H(2)O and NO at 303 K were examined. The iodine doping affected remarkably the adsorptivities of ACFs for H(2)O and NO. In particular, iodine-doped ACFs treated at 673 K show enhanced adsorptivities for H(2)O and NO. This result suggests that iodine molecules doped on the micropores should be charged by heat treatment at 673 K.     

Adsorption and gas-chromatographic properties of silver-modified silicas

Ag⁰ and Ag(I) nanoparticles are immobilized on the surface of a macroporous silica and amino silica. The adsorption kinetics of a basic dye, methylene blue (MB), from aqueous solutions and the adsorption isotherms of alkyne phenylacetylene from an octane solution are measured. The dependence of the rate constants of MB adsorption on the conditions of immobilization and silver reduction is considered. Silica containing immobilized Ag(I) is shown to have a high adsorption activity with respect to phenyl acetylene. By gas chromatography, it is shown that silver-modified silica has a higher selectivity with respect to alkenes. The reduction of silver on the silica surface and the complexation of silver ions with aminopropyl groups of amino silica lead to a significant decrease in the selectivity of composites.     

Adsorption properties of low-silica zeolite ZK-5

Water vapor, methanol, and argon adsorption isotherms, as well as the heat of adsorption of ammonia, methanol, and carbon dioxide have been determined on zeolite types A, ZK-4, and ZK-5. The results are explained by the distribution and the bond lengths of cations in the zeolite crystal lattice. It was shown that the exchange of 10–15% of the Na⁺ ions with Li⁺ in zeolite ZK-5 leads to a deformation of the 8-membered ring impeding the diffusion of adsorbed molecules. Cations contained in the 8-membered ZK-5 zeolite ring are bound more strongly to the framework, than in zeolite NaA, resulting in their smaller adsorption capacity.I. V. Grebenshchikov Institute of Silicate Chemistry, Russian Academy of Sciences, 199164 St. Petersburg, Russia. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2494–2500, November, 1992.