Influence of mechanochemical activation on dissolving model corrosion films formed on ion-exchange resins using Trilon B

Inorganic deposits formed during operation and intermediate storage contain radionuclides, whose removal during the chemical decontamination of spent ion-exchange resins used in filters for special water purification at nuclear power plants has proved to be a challenge. In such deposits, radionuclides of the corrosion group (58.60Co, 54Mn, 51Cr) are typically located in the crystal lattice of poorly soluble iron oxides. The present work discusses the possibility of using mechanochemical activation in the decontamination of spent ion-exchange resins polluted with deposits of activated corrosion products from structural materials. Samples of natural and synthesised on the surface of the KU-2-8 cation exchanger in the presence of the 57Co label magnetites were used as model deposits. It was shown that an increase in the duration of mechanochemical activation leads to an increase in the dissolution rate of magnetite in model decontamination solutions based on еthylenediaminetetraacetic acid disodium salt (Trilon B) and nitric acid. It was shown that, when using Trilon B, magnetite dissolves more efficiently, which is explained by the interaction between the oxide surface and organic complexing agents. It can be assumed that solid-phase reactions occur during the mechanochemical activation of magnetite in the presence of dry reagents (Trilon B, oxalic, ascorbic and citric acids). Therefore, a poorly soluble shell formed on the oxide surface hinders the dissolution at a low magnetite/solution ratio. Unlike the reagent-free activation, for magnetite activated in the presence of oxalic acid, an increase in the solution/magnetite ratio promotes the dissolution of iron oxides. Using the example of a model cation exchanger, it was shown that the rate and efficiency of decontamination of spent ion-exchange resins polluted with deposits containing activated corrosion products increase significantly after mechanochemical activation in the presence of oxalic acid.

Mechanochemical Activation Effect on Technogenic Iron Oxide Reduction Kinetics

Understanding the reaction kinetics of iron oxide reduction by carbon is a key task of the theory of metallurgical processes. One of the understudied features of the reaction kinetics of iron oxide solid-phase reduction by carbon is the discrepancy between the reacting substances’ small contact area and the process’s high rate. A convincing theoretical and experimental explanation of this effect has not yet been obtained. The data obtained earlier show that an increase in the scale of the briquetting pressure from 0 to 300 MPa increases the degree of its metallization during heating two-fold, and the metallization temperature decreases by more than 40 °C. Therefore, it was assumed that these effects during heating are a consequence of the mechanochemical activation (MCA) of iron oxides in the scale during its pressing. This paper presents the results of experimental studies on the influence of two types of scale MCA (grinding and pressing) on iron oxide reduction. The study of the MCA effect on the reaction kinetics of scale iron oxide reduction by carbon is a promising way to assess the criteria for scale phase composition changes under external factors. The presented results indicate a decrease in the amount of trivalent iron oxide (Fe2O3) after the MCA and an increase in the amount of one-and-a-half oxide (Fe3O4) and bivalent iron oxide (FeO). The obtained experimental data show that the initial stage of iron oxide reduction, consisting in the transition from higher iron oxides to lower ones, is possible at room temperature without carbon presence.

Study of synthesis of hydrogen and hydrocarbons by mechanochemical activation of the surface of mineral rocks

In the light of the eternal discussion regarding the sources of hydrocarbons for the initial oil and gas-forming substance, it is possible to recognize the legitimacy of both organic matter, which is confirmed by the biogenic theory of the origin of oil, and deep gases, declared by supporters of the theory of the inorganic concept, referring to the extraordinary richness of hydrocarbons in the mantle. But, the catagenic stage, the process of obtaining oil from the initial substance, in which the primary carbonaceous substance (often under such hypothetical concepts as “micron-oil”, “fluids”) passes into hydrocarbons in the form of oil deposits, causes no less scientific interest and also insufficiently studied. The author sees it as fair to attempt to put emphasis on predominantly geodynamic conditions, tectonic stresses, physico-chemical and thermobaric conditions, the generation of hydrocarbons, on the basis of the synthesis of hydrocarbons in any geological period. The article proposes the author’s chemical model describing the low-temperature polycondensation synthesis of hydrocarbons from water and carbon dioxide in the process of mechanical reactions on the surface of a rock model.

Hydrodynamic activation of heavy oil residues

Objectives. Recently, there has been a tendency to increase the volume of high-viscosity heavy oils in the total volume of oil produced. The processing of these oils requires new technological approaches. This task is closely related to the need to increase the depth of oil refining. Among the approaches proposed to solve these problems, mechanochemical activation, which is based on the cavitation effect produced by ultrasonic or hydrodynamic methods, has been suggested. This study evaluated the effects of cavitation in increasing the depth of oil refining.Methods. Straight-run and “secondary” oil products were used as raw materials: vacuum gas oil, catalytic cracking gas oil, and fuel oil. Activation was carried out in a high-pressure disintegrator. The principle of operation was to compress the oil product and then pass it through a diffuser. When the oil was passed through the diffuser, there was a sharp pressure release to atmospheric pressure, which caused cavitation in the hydrodynamic flow. The pressure gradient on the diffuser and the number of processing cycles ranged from 20 to 50 MPa and 1 to 10, respectively. The density, refractive index, and the fractional composition of petroleum products were determined using standard and generally accepted methods.Results. This paper reports the influence of mechanochemical activation of petroleum products on their physical and chemical characteristics. An increase in the pressure gradient and the number of processing cycles leads to a decrease in the boiling point of the petroleum products and their density and an increase in the yield of fractions that boil off below 400 °C. The yield of the fractions with boiling points of 400–480 °C and the remainder were reduced. The density and refractive index of fractions with boiling points up to 480 °C decreased, and the density of the residue increased. The effects of cavitation (an increase in the yield of fractions with boiling points up to 400 °C and a decrease in the density of the petroleum products) increased with increasing pressure gradient and the number of processing cycles.Conclusions. The changes in the density, boiling point, and the yield of fractions increased with increasing the pressure from 20 to 50 MPa and the number of hydrodynamic cavitation cycles from 1 to 5. Increasing the number of processing cycles to more than five had little additional effect. The effects of cavitation increased with increasing initial density of the oil product. The average molecular weight of these fractions was estimated from the densities and boiling points of individual fractions of the petroleum products. The calculation confirmed the assumption regarding the course of cracking reactions of petroleum products under the influence of cavitation and indicates the course of the compaction processes.

Influence of Mechanochemical Activation of Concrete Components on the Properties of Vibro-Centrifugated Heavy Concrete

One of the crucial problems in current construction is energy, resource, and material efficient technologies in both industrial and civil engineering, associated with new material manufacturing and building construction. This article is devoted to developing comprehensive technology for activation effects on concrete made by various production techniques: vibration, centrifugation, and vibro-centrifugation. The possibility of a significant improvement in the microstructure of concrete and obtaining materials with increased specified characteristics, depending on its manufacturing technology, were studied during the complex activation effect exposed to this concrete and its components. Chemical activation of water and mechanical activation of cement were considered. The urgency and prospects of double, complex mechanochemical activation of concrete mixture components were substantiated. It was proven that the complex mechanochemical activation of the concrete mixture components gives a synergistic effect in obtaining concrete composition with an improved structure and improved characteristics. Furthermore, the relationship between concrete production technology and the technology of activation of its components was established. It was revealed that the most effective is the complex mechanochemical activation of vibro-centrifuged concrete, which gives an increase in strength up to 30%. The study results indicate a further direction of development associated with an increase in variatropic characteristics using both prescription and technological factors.