Economic synthesis of highly dispersed amorphous silicon dioxide from technogenic wastes and its textural properties

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 silicon dioxide synthesis led to increasing effective diameter of silica particles more than four times, and a decrease in the SiO yield by ~25 %. The silica samples have amorphous structure and purity ≥ 99.97 %. The specific surface area (S ) is equal to 64 m /g for silica synthesized using copper melting slag and S = 10 m /g for silica synthesized from microsilica prepared using ferrosilicon production waste. The total pore volume is 0.22 cm /g and 0.08 cm /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 S > S . 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.

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