V. V. Gur’yanov

Preparation of Spherical Activated Carbon from Furfural, Its Properties and Prospective Applications in Medicine and the National Economy

The peculiarities of the porous structure and adsorption properties of an extraordinarily high-strength ashless carbon adsorbent composed of spherical particles produced from synthetic furfural according to a principally new technique are considered. The adsorbents are shown to have a developed structure of sorbing micro- and mesopores and are characterized by increased hydrophobicity. The adsorbents are promising materials in the high-performance adsorption recuperation of organic solvents, in preparing high-purity substances, in purifying gaseous discharge, and in a number of other processes, especially under severe operation conditions, such as the adsorption in flowing and liquefied layers at a heightened moisture content in the gas flow. Furthermore, the high chemical purity, high adsorptivity with respect to substances with diverse physicochemical properties, and high mechanical strength of the adsorbents, as well as the smooth and antimisting surfaces of their grains, make them promising compounds for hemo- and enterosorption in detoxification of a living organism in case of diverse poisoning or disease.

Effect of temperature on adsorption of phenol on microporous activated FAS-type carbons

Phenol adsorption from aqueous solutions is studied on activated FAS-type carbons. It is shown that the limiting adsorption value grows at an increase in the temperature from 293 to 318 K. The anomalous character of the temperature dependence of adsorption is related to competition between two simultaneous processes, i.e., activated and physical adsorption. The obtained adsorption isotherms are well described by the Dubinin-Radushkevich (DR) equation with an exponent of 2. It is shown that, in the case of phenol adsorption on FAS microporous carbons of different porosity, temperature invariance of the characteristic curve of the DR model is observed. Parameters of the DR equation are determined for the studied systems. Isosteric adsorption heat is calculated based on the temperature dependence of adsorption.

Hydrogen adsorption on nanoporous carbon adsorbents prepared from furaldehyde by thermochemical synthesis

Hydrogen adsorption on two samples of active carbon (FAS) produced from furaldehyde by the thermochemical synthesis method is investigated. Maximum hydrogen adsorption on these active carbons at hydrogen boiling temperature of 20.38 K and a pressure of 0.101 MPa is calculated in terms of the theory of the volume filling of micropores. Hydrogen adsorption on FAS-1-05 active carbon at temperatures of 77, 196, and 300 K and pressures of 7 and 20 MPa is calculated using the condition of linear isosteres. The calculated data are compared with the experimental results obtained for the same adsorbent at temperatures of 77 and 293 K and pressures below 5.1 and 16.1 MPa, respectively. The maximum adsorption value of hydrogen on FAS-1-05 amounts to 6.2 wt % at 5.1 MPa and 77 K.

Prediction of the micropore structure parameters and adsorption properties of activated carbons

A regularity govering variations of volume and linear size of micropores in carbon adsorbents during their vapor-gas activation was found. A parameter was proposed that characterizes the degree of development of the micropore system in activating carbons and an initial carbonized material. The parameter is defined as the number (or surface area) of micropores in the volume unit of the micropore zones. This parameter allows one to rationalize the choice of carbonized materials for the preparation of activated carbons with specified adsorption properties and to establish the range of activation beyond which the structure of the micropores loses stability. Furthermore, the parameter serves to predict how activation affects micropore structure parameters and adsorption properties of carbons. This in turn indicates the optimal degrees of microporosity of carbons needed to attain required adsorption properties.

Methane adsorption on microporous carbon adsorbent with wide pore size distribution

Methane adsorption on a microporous carbon adsorbent with a bimodal pore size distribution is studied at temperatures of 303–333 K at pressures up to 30 MPa. The total micropore volume of the adsorbent, as determined by the Dubinin method, is as large as 1.02 cm3/g. Maximum values of methane adsorption of ≈18 mmol/g are attained at a temperature of 303 K and a pressure of 30 MPa. Methane adsorption isosteres are plotted based on experimental data, and adsorption equilibria at low temperatures are calculated using the linearity of the plots. Experimental isotherms of methane adsorption are compared with the isotherms calculated by the Dubinin–Nikolaev equation with variations in parameters E and n. Temperature dependences of these parameters are determined. Specific characteristics of methane adsorption accumulation are calculated.

Effect of the porous structure of activated carbon on the adsorption kinetics of gold(I) cyanide complex

The effect the porous structure of activated carbons obtained from furfural and coconut shells has on the kinetics of [Au(CN)2]− ion adsorption is studied. Effective diffusion coefficients for [Au(CN)2]− anions in transport and adsorbing pores and mass transfer coefficients in a transport system of the pores and in microporous zones are calculated using the statistical moments of the kinetic curve.

Description of polymolecular adsorption on energetically heterogeneous surfaces

The Dubinin-Radushkevich equation is used for description of the first and subsequent adsorption layers in the case of polymolecular adsorption on energetically heterogeneous surfaces. It is found possible to predict adsorption isotherms of various vapors on nonporous and macroporous adsorbents on the basis of the minimal scope of experimental data. The derived two-parameter equation of multilayer adsorption describes the adsorption equilibria in almost the whole range of mono- and polymolecular adsorption, which is not complicated by capillary condensation, specific adsorption, or adsorption in micropores. When there are micropores and specific interactions between the adsorbate and the surface, the equation in the polymolecular range (beyond point B) enables one to characterize the surface and porosity of the adsorbent with respect to diverse adsorbates without information about standard adsorption isotherms, which makes the applicability field of the adsorption methods much broader and more valuable.

Sorbostriction of FAS-3 microporous carbon adsorbent upon vapor adsorption from a flow of nitrogen carrier gas

Sorbostriction (adsorption-induced deformation) of FAS-3 microporous carbon adsorbent is investigated under dynamic conditions upon adsorption of benzene, carbon tetrachloride, and n-hexane vapors from a flow of nitrogen carrier gas at 573 K. The values of maximum deformation and corresponding times depend on the amount of an adsorptive. The peak time of sorbostriction curves is different for each substance under study, which makes it possible to use the effect of wavelike sorbostriction for the development of sensors for the control of qualitative and quantitative compositions of gas mixtures.

Adsorption of [Au(CN)2]− ions from aqueous solutions on an activated carbon surface

Sorbent capacity and kinetics of the adsorption process on synthetic carbons (FAS grade) and commercial coconut shell activated carbons were studied in the system activated carbon-aqueous solution of sodium dicyanoaurate(I). The effect of progressive activation of carbons on the adsorption value was analyzed. The method of moments was used to calculate the internal diffusion coefficients and show their relation to the structure of activated carbons.