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A new pilot plant equipment with application of the ammonium fluorine technology for processing silicon-containing raw materials using the physical effects of sublimation and desublimation has been developed and manufactured. It is shown that the usage of the created device for the processing of metallurgical waste makes it possible to separate amorphous silicon dioxide in the form of a dispersed powder from slags, extract iron oxide, and obtain a collective concentrate of valuable components. The synthesized silicas have been studied by inductively coupled plasma (ICP) mass-spectrometry, scanning electron microscopy, X-ray diffraction, small angle X-ray scattering, laser correlation spectroscopy, and low-temperature nitrogen adsorption–desorption analysis. It has been shown that an increase in hexafluorosilicate concentration by 10 times during the silica synthesis led to increasing effective diameter of silica particles more than four times, and a decrease in the SiO2 yield by ~ 25%. The silica samples have amorphous structure and purity ≥ 99.97%. The specific surface area is equal to 58 m2/g for silica synthesized using copper melting slag and SBET = 10 m2/g for silica synthesized from microsilica prepared using ferrosilicon production waste. The total pore volume is 0.22 cm3/g and 0.08 cm3/g for these silica samples, respectively. There is a fraction of pores inaccessible (closed) for nitrogen molecules that can be detected with the SAXS method since there is a relation SSAXS > SBET. Thus, the use of waste from metallurgical industries allows one to implement a resource-saving technology for producing highly disperse silica with appropriate textural characteristics. [ABSTRACT FROM AUTHOR]

Herein, we present the hydrothermal synthesis of SAPO-56 crystals with relatively controlled crystal/particle size. The effects of water content, aluminum source, gel composition, stirring, crystallization temperature and time, as well as the incorporation of crystal growth inhibitors during synthesis were systematically investigated. The synthesized SAPO-56 crystals displayed BET surface areas as high as ∼630 m g with relative narrow size distribution in the ∼5-60 μm range. Nitrogen BET surface areas in the 451 to 631 m g range were observed. Decreasing the crystallization temperature from 220 to 210 °C helped to decrease the average SAPO-56 crystal size. Diluted gel compositions promoted the formation of smaller crystals. Crystal growth inhibitors were found to be helpful in reducing crystal size and narrow the size distribution. Specifically, ∼5 μm SAPO-56 crystals displaying narrow size distribution were synthesized employing aluminum-tri-sec-butoxide as Al source, high water content, and high stirring rates. [ABSTRACT FROM AUTHOR]

In this study, a suitable route for the selective functionalization of the outer surface of MCM-48-type mesoporous silica nanoparticles (MSNs) and its impact on the physicochemical properties were investigated. The synthesis of MCM-48 nanoparticles with intact cubic ordered mesopore structure and functionalized outer particle surface was managed by postsynthetic and co-condensation modification routes with 3-methacryloxypropyltrimethoxy-silane (MPS). The results of FTIR, 29Si and 13C NMR, thermogravimetric, and elemental analysis confirmed the successful silane surface grafting by both methods. The nitrogen sorption analysis showed the selective outer surface functionalization by the postsynthetic route for the synthesized MCM-48 nanoparticles containing the template still inside the pore channels and in the case of the co-condensation route via late addition of the silane precursors into the synthesis batch containing a fully grown silica. The solvent type in the former approach and silane addition time during the particle growth in the later route showed a significant impact on the silane content and site selective binding. The amount of grafted silane was determined by thermogravimetric and elemental analysis. It was found to increase using toluene in the postsynthetic modification route. The average particle size measured from SEM/TEM analysis ranges from 290 to 350 nm. The cubic ordered pore structure of the final silane grafted MSNs was fully preserved in both functionalization routes as corroborated from XRD analysis. In conclusion, MCM-48 nanoparticles selectively functionalized on the outer particle surface are favorable candidates for the subsequent site selective grafting reactions. [ABSTRACT FROM AUTHOR]