Adsorbent carbon-mineral

OXIDE, CARBON, AND CARBON/MINERAL ADSORBENTS FOR TOXIC, EXPLOSIVE, AND NARCOTIC COMPOUNDS -SYNTHESIS, PROPERTIES, AND APPLICATIONS... 

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

V. M. Gun ko, R. Leboda, V. V. Turov, B. Charmas, and J. Skubiszewska-Zifba, Structural and Energetic Heterogeneities of Hybrid Carbon-Mineral Adsorbents, Appl. Surf. Sci. 191, 286-299 (2002). 

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. 

Keywords carbon-mineral adsorbents, pyrolysis, hydrothermal treatment, CCI4 vapors, waste material, utilization, structural characteristics, pore size distribution... 

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. 

To determine the effect of the procedures C and M on the properties of carbon-mineral adsorbents, reference carbon adsorbents were prepared using paraffins treated under the C and C + M procedures. 

R. Leboda, B. Charmas, J. Skubiszewska-Zi ba, S. Chodorowski, P. Oleszczuk, V. M. Gun ko, and V. A. Pokrovskiy, Carbon-mineral adsorbents prepared by pyrolysis of waste materials in the presence of tetrachloromethane vapours, J. Colloid Interface Sci. 284, 39-47 (2005). 

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

Complex carbon-mineral adsorbents preparation, surface properties and their modification. 

The studies on preparation of carbon mineral adsorbents, modification of their surface properties as well as application carried out up to 1990 were presented in two comprehensive review papers [1,2]. Tarasevich published also an interesting paper on application of complex adsorbents in water purification technology [3]. The papers by Kamegawa and Yoshida [4,5], Kyotani et al. [6], Sonobe et al. [7-10], Fenelonov and Okkel [11], Bandosz et al.[12-16], Putyera et al. [17], Vissers et al. [18] as well as Baumgart and co-workers [19] are worth mentioning as they constitute a new trends in the studies and application of complex 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. 

The formation of carbon-mineral adsorbents containing carbon deposits in the form of dendrites, whiskers or carbon black is not advantageous because of the poor mechanical properties of these deposits. The morphology of the coke depends on the mechanism and conditions of its formation on the mineral surface. Two main mechanisms of formation of carbon deposits can be distinguished consecutive reactions and carbide-forming. The latter mode consists in the thermal decomposition of hydrocarbons. 

Methods of modification of surface properties of complex carbon-mineral adsorbents distinguishing those used on the commercial scale and on the laboratory scale are presented in the review paper [2]. However, not all methods can be applied in both cases. Some attention is paid to the latest publications not included in the quoted paper. 

The rate of the oxidation process is determined by the reactivity of the starting carbon and oxidizer. The greater the reactivity of the substrates the lower the temperature of the process in which uniform formation of the pores in the granules is observed. In the case of carbonaceous materials the cokes of brown coals show the greatest reactivity, and the cokes of hard coals the smallest activity. The cokes of pit coals show an intermediate reactivity. This is connected with the earlier mentioned ordering of the crystallographic structure of carbon, which is of significant importance in the case of modification of carbon deposits contained in the carbon-mineral adsorbents in which the carbonaceous compound may be characterized by a differentiated chemical and physical structure. Thus the surface properties of hydrothermally modified complex adsorbents are defined by the course of three processes ... 

Pyrocarbon (Cc 10 wt%) grafted onto nanooxides changes C(pH) differently for C/ST and C/AST (Figure 2.54c and d carbon-mineral adsorbents will be analyzed in detail in Chapter 4). 

Gun ko, V.M., Leboda, R., Turov, V.V., Charmas, B., and Skubiszewska-Zi ba, J. 2002b. Structural and energetic heterogeneities of hybrid carbon-mineral adsorbents. Appl. Surf. Sci. 191 286-299. 

Leboda, R. 1992. Carbon-mineral adsorbents—New type of sorbents. Part I. The methods of preparation. Mater. Chem. Phys. 31 243-255. 

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