Project results in 2021
The work analyzes the scientific and technical literature and patent search on the topic related to the use of organic and inorganic man-made waste to obtain sorption-active materials. Based on this work, two review articles have been prepared.
An algorithm is proposed that links the characteristics of raw materials (waste) and their processing parameters with the properties of the resulting sorbing materials. Their directions of use are also determined by the parameters of these processes. Based on the qualitative composition of the waste used to produce sorption materials, the optimal production technology is selected. It includes interrelated stages that determine the strength and sorption properties of materials and allows to obtain various types of sorption materials that can be used in the processes of physical adsorption, chemisorption, ion exchange and catalysis.
The schematic diagram of obtaining sorption materials includes the following stages:
- selection of raw materials (composition and properties of raw materials are determined);
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preparation of raw materials (physical, chemical, physico-chemical treatment);
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shaping (obtaining powdered, crushed or granular material, the stage may be final);
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increasing strength (pyrolysis, carbonation, heat treatment, degassing in an inert atmosphere in the temperature range from 600 to 850°C);
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development of porosity (steam-gas activation at a temperature of 700 to 900°C using water vapor or carbon dioxide as an activating agent; chemical activation at a temperature of 250 to 700°C using acids, alkalis, salts, etc., as activating agents);
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ready-made sorbent (evaluation of properties, determination of application areas).
These approaches provide a wide range of applications for the obtained materials in the purification of gas, liquid, and solid media from various classes of toxicants. The conditions of each stage of processing determine the chemical structure, porous structure, and sorption properties of adsorbents.
The following waste for the production of highly active sorption materials: hydrolysis lignin (waste from the pulp and paper industry), coal dust (waste from the extraction of fossil coal), carbon black (a semi-product of the processing of automobile tires); iron—containing waste, silicate-calcium sludge, sewage sludge, clay; specific waste—fullerene black (waste from the production of fullerenes).
The conducted studies show that such materials, with the exception of fullerene bilge, practically do not have a porous structure. Their elemental composition varies. The elemental composition of lignin is as follows (%): C — 69.67; O — 23.29; H — 5.04; Fe — 0.60; N — 0.42; Si — 0.27; Na — 0.21; Ca — 0.18; Al — 0.14; S — 0.07. According to the RF data, the TPP ashes are represented by 3Al2O3×2SiO2 mullite, quartz SiO2, coal and iron compounds in the form of hematite Fe2O3 and magnesite Fe3O4 (0.5%). The optically isotropic round-shaped phase with a diameter of 4-80 microns (nNa2O×mSiO2×gAl2O3) resembles zeolite, which causes the adsorption of non-ferrous metal cations by the mechanism of ion exchange. This is confirmed by the results obtained in the work on the sorption of copper ions by thermal power plant ashes under static conditions. The static capacity for copper ions of fly ash is 102 mg/g and is not inferior to the capacity for KU 2-8 grade cationite, the static capacity for copper ions of bottom ash is 184 mg / g and allows to achieve a purification efficiency of 84%.
Taking into account the proposed conceptual scheme, sorption-active materials of various compositions were obtained: "ash — clay materials", "sludge — clay materials", "coal dust — resin", "lignin — resin", “lignin”, "carbon black — clay materials", "fullerene black — clay materials", and "carbon black, fullerene black — clay materials". The conditions of the production process (molding with the addition of binder, carbonation, and activation) were selected based on the type of raw material used.
A series of activated carbons based on hydrolytic lignin with preliminary alkaline treatment was obtained and their sorption properties and porous structure parameters were investigated. The influence of the parameters of the process of obtaining activated carbon (duration of carbonization and activation, activation temperature, and water vapor flow rate) on their properties is shown. To sum up, the maximum volume of the sorption space varies from 0.30 to 0.75 cm3/g, the maximum volume of the adsorption space from 0.19 to 0.55 cm3/g, the specific surface area from 774 to 2100 m2/g, methylene blue activity from 170 to 240 mg/g, iodine from 36 to 52%, and mechanical abrasion strength varies from 30 to 70%. Based on these results, the optimal parameters for obtaining activated carbon from hydrolyzed lignin were determined: carbonation for 1 hour at a temperature of 660–680°C, activation at 820–840°C for 40 minutes at a water vapor consumption rate of 7 g per 1 g of carbonized material.
Possible fields of application of the obtained materials were determined. Namely, a sample with a developed porous structure (the maximum volume of the sorption space is 0.75 cm3/g, the maximum volume of the adsorption space is 0.55 cm3/g, the specific surface area is 2100 m2/g), but with low strength (30%), can be used to remove toxic compounds from soils, while samples with higher strength properties of up to 70% can be used in dynamic adsorption processes.
The paper considers the possibility of increasing the mechanical strength of activated carbons from hydrolyzed lignin by introducing a binder in the form of a phenol-lignin-formaldehyde resin into the composition of raw materials at the mixing stage. The resulting activated carbon in terms of the parameters of the porous structure is not inferior to industrial Russian coals (the volume of macropores is 0.41 cm3/g, mesopores — 0.16 cm3/g, and micropores — 0.36 cm3/g) exceeding them in terms of mechanical abrasion strength by 1.1–1.7 times.
The paper investigates the possibility of using the obtained activated carbons for purification from radioactive noble gases. Their adsorption capacity for krypton in the entire temperature range exceeds the sorption capacity of SKT-3 coal. The krypton adsorption coefficient for the lignin+60% FLA-4 composite varies from 105 cm3/cm3 at +20°C to 363 cm3/cm3 at 60°C, and for activated carbon of the SKT-3 brand from 36 to 332 cm3/cm3, respectively.
Composite sorbing materials of the composition "carbon black — bentonite clay" have been obtained and subjected to heat treatment in various modes. It was shown that an increase in the processing temperature from 450 to 850°C leads to an increase in Ws from 0.55 to 0.70 cm3/g, with an almost unchanged value of W0 (0.05–0.06) cm3/g. The specific surface area of the materials is in the range of 150-200 m2/g. An increase in the processing temperature, including in the presence of water vapor as an oxidizer, leads to the development of a mesoporous structure and contributes to an increase in water resistance and strength of materials, which reaches 70-80%.
Technologies of extraction of active components such as transition metals and REE from spent catalysts of oil refining (cracking, alkylation, hydroprocesses, conversion of hydrocarbons) are evaluated. Possible options for introducing valuable components into the composition of block catalysts for oxidation and denitrification are considered, both with their extraction from spent catalysts and without extraction (using the entire catalyst mass with its preliminary purification from pollutants and mechanochemical activation). The technology of thermo– and mechanochemical processing of spent catalysts containing active components suitable for the creation of oxidation catalysts (Co, Ni, Mn, Cu, Zn, Cr, REE) and denitrification (Cu, W, V) has been selected. The proposed method includes the following stages: first, removal of accumulated pollutants from spent catalysts such as sulfur compounds (in the form of sulfur); second, removal of coke deposits (by their deep oxidation); and third, preparation of catalyst mass containing transition and/or REE metals (by mechanochemical activation) as a component of a coating suspension for the formation of a thin-layer oxide catalytic coating on primary metal carriers.
In order to create a primary metal carrier for block catalysts of oxidation and denitrification of high-intensity industrial emissions, a technology for preparing a primary carrier is proposed, which consists in a metal frame of disordered structure with the required permeability. The following developments were made:
- the process of preparing metal blocks: that is, cross-porous primary carriers of block catalysts from metal construction waste and similar materials (foil trimmings with a thickness of 50–100 microns, plates, chips, wire, and mesh), sorted by appearance and grades of metals and alloys, including fehral X15Y5, X23Y5, steel X18N10T, nichrome X20N80, copper M1, brass L63, aluminum L5;
- conditions of the gas corrosion process: the oxidizing agent used (air oxygen), its flow rate, temperature, mode and duration of treatment and their effect on the thickness of the resulting oxide film on the metal surface of the primary carrier depending on the material of the metal frame and its gas permeability.
To study the gas corrosion process, the following steps were formulated:
- oxidation and study (by X-ray, IR spectroscopy, electron probe and elemental microanalysis) of the chemical and phase composition of oxide films formed during the oxidation of various metallic materials intended for use in the preparation of a metal frame;
- evaluation of kinetic parameters of the oxidation process of various wastes generated during the processing of metal materials.
It was established that the kinetics and growth of the oxide film is due to the direct-flow diffusion of metal cations along the interstices of the crystal lattice to the oxide-gas boundary (Fe3+, Al3+, Cr3+ for fehrales; Fe3+, Ni2+, Cr3+ for chromium-nickel alloys; Cu1+, Cu2+, Zn2+ for copper and brass; and Al3+ for aluminum) and the countercurrent diffusion of O2- ions to the "oxide-gas" boundary.
It was shown that oxidation on wires and chips occurs at a higher rate than on plates, which leads to a greater increase in the mass of the oxide film at relatively low temperatures and over a shorter period. For the synthesis of block oxidation catalysts, it is more expedient to use metal waste in the form of wire and chips.
The principal technologies for complex processing of spent catalysts for hydrotreating petroleum raw materials and reforming oil have been developed. The first technology includes operations of oxidative firing of catalysts, two-stage countercurrent decomposition of catalysts with sulfuric acid solutions, clarification of solutions, and sequential sorption of molybdenum first on a macroporous weakly basic anionite. This is followed by desorption with ammonia solution and separation from desorbate in the form of ammonium paramolybdate. Next, sorption of cobalt or nickel on chelating ionite with bis-picolylamine functional groups, followed by desorption with sulfuric acid solution and separation from desorbates in the form of basic cobalt or nickel carbonates. Then follows the sorption purification of Al2(SO4) solutions from iron impurity on iminodiacetate ionite. The second technology includes operations of oxidative firing of catalysts, grinding, selective leaching of rhenium with sodium bicarbonate solution, and extraction by sorption on the rhenium selective anionite Puromet MTA 1701. It is followed by desorption with an ammonia solution and separation from the desorbate in the form of ammonium perrenate, complete decomposition of the catalyst after extraction of rhenium with a HCl solution with the addition of H2O2 and the separation of platinum from the clarified solution by cementation on metallic aluminum. Solutions of Al2(SO4)3 or AlCl3 can be used directly in water treatment processes or (after purification from iron impurities) in the form of corresponding salts after their separation from solutions by crystallization. Alternatively, they can be used as precursors for the synthesis of artificial cryolite or (refers to Al2(SO4)3) aluminum-ammonium or aluminum-potassium alum.
As a result of the research carried out in 2021, 12 articles were published in journals indexed in the international databases Web of Science and Scopus, which allowed to achieve the established target. A Young Scientists’ School seminar on the subject of "Energy-resource. efficient combined waste recycling technologies of hazard classes 3–5" was held.
