The development of adsorption purification technology in industry is divorced from research in the development of new methods for the synthesis and modification of composites, while the efficiency of the adsorbent directly depends on its structural and surface properties. Currently, there is an increasing demand for hydrogel adsorbents used in pharmaceuticals, medicine, and the chemical industry for wastewater treatment. Dash-Salakhlinsky bentonite, a natural clay mineral and activated carbon of the BAU-A brand, was used as an object of study. By intercalation of bentonite with activated carbon, a bentonite-coal composite was obtained. Grinding equipment of medium energy density was used: roller-ring vibrating mill VM-4. Activation time was 15 min. The average particle size of the initial bentonite and bentonite-carbon composite was determined by laser diffraction on a particle size analyzer. During mechanical activation of bentonite, the nature of the distribution of particles indicates the predominant process of aggregation over grinding. The morphology, structure, and textural properties of the composite were studied by the methods of low-temperature nitrogen adsorption-desorption and IR spectroscopy. An increase in the specific surface area and porosity after mechanochemical activation as compared to the calculated values indicates the interaction between the components. IR spectroscopy established the formation of additional functional groups that can act as active centers, which positively affects the adsorption properties. It is shown that the bentonite-charcoal composite has a high sorption activity with respect to the brilliant green dye. The data obtained can be useful in the development of effective sorbents for wastewater treatment from pollution by organic compounds, as well as in medicine and pharmaceuticals.

In the work, an attempt was made to mechanochemically synthesize silicon oxycarbide composites from activated carbon and silica. Structure of the composites was studied using powder X-ray diffraction and IR spectroscopy. Formation of silicon oxycarbides was confirmed by presence of Si-O-C bond. Influence of the raw materials ratio on structural and chemical properties of resulting composites was revealed. With an increase of silica share in the initial mixture, a decrease in specific surface area and pore volume was noted, as well as an increase of the concentration of surface functional groups. Samples of the composites were tested in processes of sorption of methyl orange and fluoride ions. It was established that adsorption capacity for methyl orange decreased, while that for fluoride ions significantly increased comparing to activated carbon.

The powdered bentonite/iron oxide composite material was synthesized by chemical co-precipitation. The grain size composition, morphology, crystal structure, porosity, and thermal stability of the obtained powder were investigated. It was established that iron oxide exists in the composite as the maghemite/magnetite solid solution with the formula Fe 2.950 O 4 . An increase in the viability of the bacterium Escherichia coli M-17 after culturing in the nutrient medium in the presence of the synthesized bentonite/iron oxide powder was found.

An investigation is performed of synthesized halloysite/magnetite composite materials and their porous structure, surface morphology, and physicochemical properties. It is established that the halloysite/magnetite composite samples have values of the effective field of anisotropy and coercive force that are higher than those found for magnetite.

Siliconoxycarbon adsorbent was synthesized by mechanochemical activation of activated carbon BAU and by sol-gel technology by deposition of sodium metasilicate on the surface of coal, followed by drying and calcination of the samples and tetraethoxysilane to remove the solvent. To study the morphology of adsorbent particles, the method of scanning electron microscopy was used, according to which the nature of the interaction of activated carbon with sodium metasilicate and tetraethoxysilane was judged. Mechanochemically modified activated carbon is a fine powder: both large crystal-like particles and small shapeless ones are visible. During the joint mechanical treat-ment of activated carbon and white soot, agglomerates of amorphous white soot are noted, which are layered on activated carbon particles. The adsorbent obtained by the sol-gel method has large clusters of amorphous silicon dioxide covering the coal particles, almost completely "hiding" them. The results of studies of silicon oxycarbon adsorbents by infrared spectroscopy indicate the appear-ance of absorption bands characteristic of vibrations of Si-O-C bonds. For the sol-gel method, the absorption bands are more diffuse. Using the resulting composite as an adsorbent, studies were carried out on the efficiency of extraction of the thiazine dye methylene blue from aqueous solu-tions and defluorination of extractive phosphoric acid. For the mathematical description of the adsorption process, traditional models of adsorption kinetics (pseudo-first and pseudo-second or-ders) were applied. It has been established that the presence of silicon-containing compounds re-duces the defluorination temperature by increasing the proportion of SiF4 in gaseous products. This allows you to increase productivity and reduce energy costs for defluorination.

A halloysite/magnetite composite material is synthesized via the chemical coprecipitation of iron salts in halloysite pores. The efficiency of removing of a methylene blue thiazine dye from aqueous solutions is investigated using the obtained composite as an adsorbent. A unified model that combines the equilibrium and kinetics of adsorption is used to obtain a mathematical description of the adsorption process. It is shown that unlike standard models of adsorption kinetics (pseudo-first and -second order), the unified model allows us to determine the true rate constant of the process, which is independent of the initial concentration of the dye in a solution.

Halloysite is modified with magnetite nanoparticles by the chemical coprecipitation of iron salts. To characterize the surface and study the physical-chemical properties of the resulting composite and its components (halloysite and magnetite), we use dynamic light scattering, electron microscopy, the low-temperature adsorption–desorption of nitrogen, X-ray diffraction analysis, Mössbauer and IR (infrared) spectroscopy, and magnetic measurements. Energy-dispersive analysis data and X-ray diffraction patterns confirm the modification of halloysite by magnetite nanoparticles, changing the zeta potential and the adsorption capacity of the surface. IR spectral analysis of the studied composites reveal shifts in the characteristic bands of halloysite and magnetite during their formation. The halloysite/magnetite composite samples have a higher field strength of effective anisotropy and coercive force compared to magnetite.

Halloysite/magnetite composite was synthesized by chemical coprecipitation. To evaluate the crystal structure, texture, surface morphology, and magnetization of the composite, electron microscopy, low-temperature nitrogen adsorption–desorption, X-ray diffraction analysis, and magnetic measurements were used. Granulometric analysis of the obtained materials showed that larger particles appear when halloysite is modified with magnetite. It was revealed that the studied samples of halloysite and composite belong to mesoporous bodies. An increase in the size of magnetite crystallites was found in the structure of magnetized clay. It is shown that samples of magnetized halloysite are characterized by higher values of the coercive force and lower values of the specific saturation magnetization compared to those found for magnetite.

The effect exerted on the chemical properties and structure of activated carbon by the mechanical treatment as a modification procedure was studied. Mechanochemical modification of carbon samples was performed in a roller–ring vibration mill for 5 to 30 min. Samples were studied by X-ray diffraction, IR spectroscopy, and low-temperature nitrogen adsorption. X-ray diffraction analysis shows that the supply of mechanical energy increases the extent of structural disordering of activated carbon, which is manifested in an increase in microstrains. The mechanical treatment for more than 5 min led to a decrease in the specific surface area of the samples with a simultaneous increase in the total pore volume. The mechanical treatment for 5 min and less led to an increase in the specific surface area and to a decrease in the pore volume. The results of potentiometric titration and Boehm titration show that the modification leads to an increase in the concentration of phenolic and carboxyl groups. It is concluded that mechanochemical modification of activated carbon in air leads to its intense oxidation resulting in formation of oxygen-containing groups and in their decomposition.

The environmental problems of the production of extraction phosphoric acid and the effect of fluorine on the human body are discussed in the article. The creation of the industry of phosphoric fertilizers on the basis of processing of fluorine-containing phosphate raw materials and fluorine-containing compounds, the development of their application require the study of environmental consequences arising from this, because fluorine is characterized by high mobility in the biological cycle of metabolism. For the purification of phosphoric acid from fluorine was used carbon adsorbents such as active charcoal brand BAU, natural graphite deposits Kyshtymsky, P514 soot, charcoal. Experiments on the purification was carried out on non-evaporated half-hydrated extraction phosphoric acid which was produced by joint stock company «Apatit» in Cherepovets city in Russia. The following analyses were carried out: IR-Fourier spectrometry, research of acid–base properties of carbon materials by potentiometric titration, potentiometric method of fluorine determination in extraction phosphoric acid. It is mentioned that the carbon black P514 is the most efficient adsorbent for purification of extraction phosphoric acid. The total number of functional groups on its surface is 0.62 mmol/g, the degree of purification from fluorine compounds is 94.8%.

The kinetic and dynamic characteristics of the sorption of rare earths metals (REE) from no evaporated extration phosphoric acid (EPA) of dihydrate production on macroporous strongly acidic cation Rurolite C150 were investigated. The process of sorption of rare earth metals was established to take place in the external diffusion region.

The qualification of phosphoric acid is carried out depending on the use of phosphates of various deposits and the necessary quality of the final products. An acquisition of phosphoric acid of the required quality should be carried out taking into account three aspects: resource-energy, ecology and complex processing. Solving the problems of one aspect entails solving the problems of the other aspects. The rational use of natural resources and the reduction of environmental pollution is the determining factor in the choice of technological regimes for complex processing of raw materials with a reduction in the volume of waste of all kinds or transferring them into forms easily recyclable or specially stored. The absence of economically sound technologies for processing phosphogypsum determines its preferential warehousing. The second component that requires recycling is fluorine. In this regard, the purification of phosphoric acid from fluorine should use technologies that realize the trapping of fluorine compounds released into the gas phase. This is relevant from the point of view of the complexity of processing raw materials with the extraction of rare-earth elements. The use of mechanochemical activation makes it possible to achieve a nanoscale level. To a lesser extent, this aspect relates to the stage of sulfuric acid decomposition, proceeding with the participation of three phases: solid, liquid and gas. In turn, the surface structure of the gas-liquid layer plays the role of an energy barrier for evaporation. To establish the basic energy patterns of concentration and defluorination n the disc apparatus and to optimize the process, a thermophysical model was developed in which the range of effective parameters was determined by the joint solution of a number of equations for the desired ingredients in the phosphoric acid concentration range of 52-65%. The solution of the problem of complex purification of wet-process phosphoric acid can be carried out by adsorption methods that allow to remove to some extent almost all impurities.For citation:Smirnov N.N., Smirnova D.N., Ilyin A.P., Kochetkov S.P. Problems and prospects of production and qualification of phosphoric acid. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 7. P. 48-56.

The basis of production of extraction phosphoric acid is two simultaneous processes: dissolving phosphate raw material in a mixture of sulfuric and phosphoric (formed in the process) acids and crystallization of calcium sulfate (phosphogypsum). Phosphogypsum is an inevitable large-tonnage and cumbersome waste at sulfuric acid processing of apatite, which is of interest not only as a source of building gypsum, but also as an alternative rare earth raw material does not have a natural activity and containing rare-earth elements as a cerium and yttrium groups. As a raw material for the production of rare earth elements, calcium sulfate of three types has been used: phosphogypsum from a sludge accumulator, calcium phosphate phospho-hemihydrate and calcium sulfate phosphate dihydrate from a carousel filter produced by extraction phosphoric acid at JSC "PhosAgro-Cherepovets". The extraction of rare-earth elements from phosphogypsum from a sludge accumulator by leaching (percolation) with inorganic acids with subsequent sorption on cation-exchange resins is considered. As an adsorbent for extracting REE from leach solutions, cationite "Purolite" S-150 is used. A static exchange capacitance of cation exchanger is found that is the capacity of the resin when equilibrium is reached with a solution of a certain volume and composition. The static capacity of cation exchanger for rare-earth elements is 1.57%, which indicates a good absorbing capacity. Desorption of rare-earth elements from the cation exchanger is carried out with a solution of ammonium nitrate. The optimal solution for leaching was found to be sulfuric acid with a concentration of 5% by weight. The degree of extraction of rare-earth elements from phosphogypsum with sulfuric acid is about 82%.Forcitation:Artamonov A.V., Smirnova D.N., Smirnov N.N., Ilyin A.P. Extraction of rare earth elements from solid waste of production of phosphoric acid followed by sorption on cation exchange resins. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 10. P. 87-93

A well-chosen process conditions of defluorination with the use of adsorption purification of phosphoric acid (EPA) allow not only remove objectionable content, fluorine, silicon, but also realize the selective extraction of scarce raw materials - rare earth elements (REE). Perspective direction of modification of carbon materials is the approach associated with the fixing on the surface functional centers by treatment with organic acids.

Extraction phosphoric acid is a multicomponent product. Nowadays it is actual the usage of adsorbents for acid cleaning. Mechanochemical method of preparation of carbon adsorbent with the usage of silica with different activity was considered. Under mechanochemical activation compounds of silicon carbide and oxycarbide are formed. At phosphoric acid cleaning on the obtained silicon-carbon adsorbents was shown to increase in a defluorination degree.

Extraction phosphoric acid is a multicomponent product. Using sorbents for acid purification and removal from it rare earth elements (REE) is actuality today. Mechanochemical synthesis of carbon adsorbent using the silica with different activity was considered. At mechanochemical activation the compounds of carbide and silicon oxycarbide are formed. It was shown that at extraction phosphoric acid purification on obtained oxycarbon adsorbents the degree of defluorination is increased with REE adsorption on the adsorbent surface.

The analysis of methods for producing purified phosphoric acid indicates that the main problem is the decomposition and removal of soluble complex compounds of fluorine with metals. The required product quality is achieved by using universal methods of complex purification of extraction phosphoric acid by applying carbon adsorbents. The efficiency of the proposed method of production of purified phosphoric acid was shown to achieve by combination of venting stapes of fluoride compounds, adsorption purification and simultaneous extraction of rare earth elements.

The approach to data processing the potentiometric titration of aqueous suspensions of carbon materials, enabling to construct of desorption isotherms of the proton, the pK spectra, determining the point of zero charge, i.e parameters which are a measure of acidic and basic properties of the carbon surface in aqueous solution. The experimental technique and calculation was worked out on the activated carbon BAU and technical carbon P 514.