Carbon-mineral adsorbents adsorption

Keywords fumed oxides silica gels activated carbons carbon-mineral adsorbents toxic and narcotic compounds explosives dynamic and static adsorption... 

Abstract. A variety of pyrocarbon/silica gel adsorbents were prepared using commercial mesoporous silica gels Si-40, Si-60, and Si-100 as matrices modified by carbon deposits from pyrolysis of several organic precursors. The second type of hybrid carbon-mineral adsorbents was synthesized using spent natural palygorskite utilized in paraffin purification. The adsorbents were then heated, hydrothermally treated, or modified by additional deposition of carbon. Changes in the structural and adsorption characteristics of hybrid adsorbents before and after treatments were analyzed by microscopy, p-nitrophenol and nitrogen adsorption isotherms, and TG, TEM, XRD, and XRF methods. 

Carbon-mineral adsorbents are of interest because of their potential applicability in practice, and as model adsorbents in research. Such composite materials can be applied for the adsorption of both polar and nonpolar compounds.1,2 These adsorbents have been utilized in chromatography, trace analysis, environmental protection, technology of water and sewage purification, and in other processes.1... 

There is an important problem related to the utilization of spent adsorbents and catalysts, especially natural zeolites, used in chemical, petrochemical and food industries after adsorbing large amounts of organic substances.5-7 As a whole they can be used as raw materials to prepare carbon-mineral adsorbents.8 Therefore, the aim of this work was to elucidate the influence of different factors such as the kind of organic precursors and inorganic matrices, including spent adsorbents, and the preparation and modification techniques on the structural and adsorption properties of carbon-mineral adsorbents. 

SYNTHESIS AND STRUCTURAL/ADSORPTION CHARACTERISTICS OF UNMODIFIED AND MODIFIED HYBRID CARBON/MINERAL ADSORBENTS... 

The process of carbon deposit formation in complex carbon-mineral adsorbents may be initiated and terminated in any stage or stages of scheme 1. This is dependent on the chemical nature of the carbonized substance, porous structure and chemical nature of adsorption and catalytic sites of the mineral matrix, etc. For this reason, the complex adsorbents prepared by the third and fourth methods have the carbon deposits consisting of the substances of different chemical and physical structure formed during the defined stages of Scheme 1. 

Leboda, R. and Dabrowski, A. 1996. Complex carbon mineral adsorbants Preparation, surface properties and their modification. In Dabrowski, A., and Tertykh, V.A. (Eds.) Adsorption on New and Modified Inorganic Sorbents, Smdies in Surface Science and Catalysis, Vol. 99. Amsterdam, the Netherlands Elsevier, pp. 115-146. 

Chemisorption raises basic questions for the carbonate geochemist about the boundary between sorption and coprecipitation. If the adsorption reaction takes place in a solution that is also supersaturated with respect to the carbonate mineral substrate, then the adsorbed ions can be buried in the growing layers of the mineral and become coprecipitates. This mechanism can result in distribution coefficients that are dependent on growth rates. Also, when chemisorption is involved, an entirely new phase or a coprecipitate can form in the near-surface region of the carbonate (e.g., see Morse, 1986 Davis et al 1987). A classic example is apatite formation on calcite in dilute solutions (e.g., Stumm and Leckie, 1970). 

Surface complexation — is complexation of metal ions by ligands immobilized on the electrode surface (-> electrode surface area). The ligands may be incorporated in the structure of a -> carbon paste electrode, covalently bound to the surface of a chemically modified electrode (-> surface-modified electrodes), or adsorbed (-> adsorption) on the electrode surface etc. Surface complexation is not confined to electrodes. It can occur on many surfaces, e.g., minerals, when in contact with metal ion solutions or solutions containing complexing ions (in the first case, the surface provides the ligand and the solution the metal ion, whereas in the second case, the surface provides the metal ion and the solution the ligand). Surface complexation can be an important step in the dissolution of solid phases [ii]. 

The method of adsorption sites topography regulation discussed here does not permit to prepare the adsorbents of random type topography due to a poor transformation of alcohols into carbon matter. Another noteworthy type of reaction consists in the decomposition of methylene chloride on the surface of mineral adsorbents [35,36] ... 

In terms of this adsorption, properties of various adsorbents, among them the inorganic sorbents can be determined. It must be emphasized that inorganic sorbents such as silica, alumina, titania, complex carbon - mineral sorbents, apatites, e.t.c., are both structurally and energetically heterogeneous. Their total heterogeneity may be described by the kinds of adsorption potential distribution function which is one of the most significant characteristics of the aforementioned solids. 

Chapter 4 deals with hybrid carbon-mineral materials. These materials are interesting objects with respect to the interfacial phenomena becanse of the mosaic structure of their surfaces. This can resnlt in strong clusterization of adsorbates and appearance of unusnal properties of the materials in adsorption and other phenomena. 

The chemical composition of the porous media fundamentally influences the adsorption. The rocks abundant in bi- and multivalent cations (carbonates and clay minerals) adsorb more polymer than the sandstones and silica type minerals do. 

Serious science started in Russian empire in the middle of the XVIII century. The first known Russian scientist M.V. Lomonosov obtained (in the I750sJ experimental data on the preservation of the mass of substances in chemical reactions. T.E. Lovits discovered adsorption from solutions he used wood carbon as an adsorbent. Among other scientists, Lovits detected compounds using characteristic forms of their crystals. V.M. Severgin published a book on analysis of mineral raw materials. 

SO as to end the air mixture to adsorber No. 2. The system is then fully automatic. Solvents which have been successfully recovered by the activated carbon adsorption method include methanol, ethanol, butanol, chlorinated hydrocarbons including perchlorethylene, which boils at 121 C (250 °F), ethyl ether, isopropyl ether, the acetates up to amyl acetate, benzene, toluene, xylene, mineral spirits, naphtha, gasoline, acetone, methyl ethyl ketone, hexane, carbon disulfide, and others. 

Exchangeable ions (EXC), sometimes including ions nonspecifically adsorbed and specifically absorbed on the surface of various soil components, such as carbonate, organic matter, Fe, Mn, Si, and Al oxides, and clay minerals. This part is controlled by adsorption-desorption processes. 

The dispersant used in these studies is Chevron Chemicals OLOA 1200, a polybutene of about 70 carbon atoms attached to a succinic acid group which is reacted with diethylene triamine to provide the basic anchoring group. Film balance studies showed that the adsorbed films have a film thickness of 50 X. This dispersant is supplied as a 50 w% solution in a mineral oil. It can be deoiled by adsorption from toluene onto silica with elution by acetone. In this paper the w% of dispersant refers to the deoiled material. 

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