The paper describes how the conditions of preparing ferrocyanides on hydrated titanium dioxide support affect the surface texture of the resulting materials, their elemental and phase composition, and their ability to sorb cesium. The sorbents prepared under the optimal conditions exhibited increases specificity to Cs (K d = 10 5.6±1.0 ml g -1 ) and high capacity (no less than 270 mg g -1 ).Many-year research and the world practice show that mixed transition metal ferrocyanides are the most specific sorbents for cesium radionuclides. Various procedures for preparing ferrocyanides have been described in the literature: precipitation followed by freeze granulation or drying [1], deposition of thin ferrocyanide films onto the surface of inert (glass, polyethylene terephthalate, Millipore polypropylene membranes) [2][3][4] or sorption-active (clinoptilolite, glauconite) [4-6] supports, preparation of composite sorbents consisting of transition metal ferrocyanides and silica gel [7], alumina gel [8], ion-exchange resins [9], or Taunit carbon nanostructured materials [10], and sol-gel method [11].It is noted in practically all the published papers that each synthesis step strongly affects the sorptionkinetic and service characteristics of the sorbents. The properties of the sorbents prepared are determined by the chemical composition, pore structure, and degree of perfection of the sorbent crystal lattice. By varying the pore structure of the material or the chemical nature of the sorbent surface, it is possible to control and improve the sorption properties.It was shown in [2-6] that thin-layer sorbents exhibit the maximally developed surface, the sorption activity that is maximum possible for granulated materials, and good kinetic characteristics; their sorption capacity is utilized to the largest extent. To solve practical problems in radiochemistry and related fields, it is always possible to choose a support for the subsequent preparation of a sorption material exhibiting a set of the required properties. Apparently, the most promising line in the synthesis of new sorption materials is preparation of sorbents by surface modification of sorption-active supports exhibiting highly developed surface. Our studies showed that in this case it is possible to prepare highly specific polyfunctional and complex sorbents. The relationships in formation of the new sorption-active phase, observed in the course of the modification, resemble those observed not only in the growth of thin films on inert supports, but also in the preparation of sorption reagent systems [12].

Sorption isotherm of caesium from tap water by mixed nickel-potassium ferrocyanide based on hydrated titanium dioxide is obtained for a wide range of concentrations of caesium. It is shown that there are three types of specificity to caesium sorption sites in this sorbent. Sorption chemisms of caesium are studied, factors conditioned high sorption capacity of the sorbent are revealed. It is shown that occupation of sorption sites I and II is well approximated by Langmuir equilibrium and this process can be described within the bounds of theory of ion exchange. The expected sorption chemism of caesium by sorption sites III at high concentrations of caesium ([50 mg L -1 ) is precipitation of mixed nickel-caesium ferrocyanide in pore space of the sorbent.

The kinetics of cesium sorption onto mixed nickel potassium ferrocyanide supported on hydrated titanium dioxide were studied in different ranges of cesium concentrations. At the cesium concentration in solution from 2 × 10 -7 to 5 mg L -1 , the sorption rate is determined by external diffusion of cesium ions in solution, heterogeneous ion-exchange reaction, and internal diffusion of cesium in the pore space of the sorbent. The slowest step is the breakdown of sorption colloids and uptake of the released cesium ions by the sorbent. At the cesium concentration in solution higher than 50 mg L -1 , the rate-determining step is the precipitation of mixed nickel cesium ferrocyanide in the pore space of the sorbent.

Coke-oven gas is produced during coking of charge coal in a coking chamber and it constitutes a mix of different substances. A composition of different components in the gas depends on a composition of the coal charge and conditions of the coking. At a recovery plant, aromatic hydrocarbons are retrieved from the coking gas by absorption oil in packed absorbers. Mass-transfer apparatus demand the equability of the phase distribution. Hydrodynamic conditions, appearing inside contacting apparatus, determinate the effectiveness of the mass-transfer, which means that unbiased evaluation of any given mass-transfer apparatus can be made while simultaneous considering its hydrodynamic and mass-transfer indicators. The different types of column packing have been investigated in this study. The calculations of benzol absorbers have been performed basing on the initial data using the standard methodologies for the recovery plant of JSC EVRAZ NTMK coke and by-product enterprise. For comparison of the results obtained, the complex indexes of effectiveness, that simultaneously take into account the mass-transfer rate, the device capacity, the features of packings and energy cost, have been used.

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