RU2526454C1 - Method of obtaining finely-disperse amorphous microsilica - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: method includes preliminary crushing and pounding in an agate mortar of dried and calcined in the muffle furnace diatomite with weight 5-8 g to the powder state, pounding in a porcelain mortar of 6-fold quantity of alkali flux, consisting of a mixture of water-free potassium and sodium carbonates, mixing diatomite and alkali flux in an alundum or corundum crucible, fusion of the obtained mixture in the muffle furnace in the crucible for 40-50 min with further pouring of the melt onto a silicate base, its transfer into a heat-resistant cup, separation of silicic acid first by leaching the melt with distilled water, and then, after carrying out pH control by titration with a 0.1 M solution of potassium hydroxide with methyl orange, its processing with 100-200 ml of distilled water to complete dehydration of silicic acid. Precipitation of silicic acid is carried out by an addition of 30-40 ml of a concentrated solution of hydrochloric acid and after the reaction slowing the solution is evaporated on a sand bath until carbon dioxide release stops. The sediment processing is carried out by addition of 10-20 ml doses of the concentrated solution of hydrochloric acid, after that, 100-200 ml of distilled water are added, after evaporation of the solution on a water bath for 5 min to complete dehydration of hydrated silicon (IV) oxide and control of the medium pH by titration with a 0.1 M solution of potassium hydroxide with methyl orange, separation of silicon (IV) oxide by filtration is performed with collection of filtrate through a non-compact ash-free filter into a cup and washing of the sediment with a 0.5% solution of hydrochloric acid to the negative reaction to ions of iron (III) with rhodanide. Control of the medium pH with titration with a 0.1 M solution of potassium hydroxide with methyl orange is carried out. The sediment drying is carried out on the filter, and then in the Petri dish in an exsiccator at a temperature of 90-120°C.EFFECT: invention makes it possible to reduce labour consumption of the process of melt leaching from the crucible, which is an economical and energy-preserving factor, and increase the output of finely disperse amorphous microsilica.

Description

The invention relates to construction materials, namely the production of modified additives for concrete, mortar, dry mortar, thermal insulation materials.

A known method of producing precipitated silica filler, including the carbonization of a liquid glass solution with carbon dioxide, neutralization, hydromechanical treatment of the resulting suspension, filtering, washing and drying the precipitate. Hydromechanical processing is carried out in a hydrodynamic acoustic apparatus with a rotary emitter at a suspension speed of 1-2 m / s (RU 2023664, IPC C01B 33/18, C09C 1/28, publ. 30.11.1994).

The disadvantage of this method is multioperation, the use of sulfuric acid to neutralize, which causes the formation of sulfate effluents, the cost of the process, the complexity of the hardware design.

The closest in technical essence to the claimed solution is a method for producing finely dispersed amorphous silica fume, which consists in mixing pre-dried to 5-6% humidity and calcined in a muffle furnace at a temperature of 900-1000 ° C silicate rock weighing ~ 1.0 g with 6 -fold amount of alkaline flux, consisting of a mixture of anhydrous potassium and sodium carbonates, fusion of their mixture in a muffle furnace at a temperature of 800 ° C for 30 minutes in a platinum crucible until a liquid mass without grains is formed. The platinum crucible is melted out with a forceps from the muffle furnace, the molten mass is distributed along the walls with a rotary movement, the crucible is quickly immersed in a porcelain cup half filled with distilled water to cool the melt, which is transferred to a heat-resistant glass. To isolate silicic acid, the contents of the crucible are leached with distilled water heated to 70-80 ° C. The treatment of the melt with distilled water is repeated until the silicic acid is completely dehydrated. The last traces of melt are removed by treatment with a small amount of concentrated hydrochloric acid solution. The heat-resistant glass is covered with a watch glass, heated in a water bath, 10 ml of concentrated hydrochloric acid solution is added to precipitate silicic acid. After slowing down the reaction, the solution is stirred, put in a water bath and evaporated until the carbon dioxide evolution ceases. Then the watch glass is removed, rinsed with a minimum amount of water. The resulting solution should be acidic. The separation of silicon oxide (IV) is based on precipitation with mineral acids (hydrochloric or perchloric acid), which are released as a gelatinous hydrogel. At the same time, part of it remains in the colloidal state in the form of a hydrosol. For complete separation of silicon oxide (IV), it is necessary to convert the obtained hydrogel and hydrosol into an insoluble form - into a hydrophobic irreversible colloid. The latter is achieved by dehydration of the gel by at least two treatment of the precipitate by adding 5 ml of concentrated hydrochloric acid solution, close the heat-resistant glass with a watch glass, heat the solution in a water bath, add 50 ml of distilled water at a temperature of 70-80 ° C and evaporate the solution in a water bath for 5 minutes until complete hydration of the hydrated silica (IV). The separation of silicon oxide (IV) is carried out by filtration through a loose ashless filter (white tape), collecting the filtrate in a 400 ml glass and washing the precipitate with a 1% hydrochloric acid solution until the iron (III) ions react with thiocyanate. The precipitate is dried on a filter, then in a Petri dish in an oven at a temperature of 90-120 ° C. The pH of the medium is monitored by titration with a 0.1 M solution of potassium hydroxide with methyl orange after leaching, before filtering and after washing (Sunin A.N., Sedova A.A., Rybkina A.A., Uskova E.N. to the workshop on quantitative analysis. - 3rd ed., rev. and add. - Saransk: Publishing house of Mordov. un-that, 2005. - P.29).

The disadvantages of this method include the complexity of the leaching process of the melt from the crucible, a small yield of finely dispersed amorphous silica fume from silicate rock due to the use of a small weight of the sample.

The technical result consists in reducing the complexity of the process of leaching the melt from the crucible, which is an economical and energy-saving factor, as well as in increasing the yield of finely dispersed amorphous silica fume.

The essence of the invention lies in the fact that the method includes mixing pre-dried and calcined silica-containing raw materials in a muffle furnace with 6 times the amount of alkaline smoothing, fusing their mixture in a muffle furnace in a crucible, transferring the melt into a heat-resistant glass, releasing silicic acid by leaching the melt with distilled water, treatment of the melt with distilled water until complete dehydration of silicic acid, precipitation of silicic acid with a concentrated solution of hydrochloric acid, evaporation of p solution until the carbon dioxide evolution ceases, two-, three-fold treatment of the precipitate by adding concentrated hydrochloric acid solution, pouring distilled water and evaporating the solution in a water bath until the hydrated silicon oxide (IV) is completely dehydrated, the silicon oxide (IV) is separated by filtration, collecting the filtrate in a glass and washing the precipitate with a solution of hydrochloric acid until a negative reaction to iron (III) ions with thiocyanate, the precipitate is dried on a filter, then in a Petri dish in a dryer cabinet, control the pH of the medium by titration with a 0.1 M solution of potassium hydroxide with methyl orange after leaching, before filtering and after washing. Diatomite weighing 5-8 g is used as a silica-containing raw material, after mixing it with an alkaline smoothing alloy, the mixture is fused in a muffle furnace in an alundum or corundum crucible for 40-50 minutes, followed by pouring the melt onto a silicate base. After transferring the melt into a heat-resistant glass and isolating silicic acid by leaching the melt with distilled water, it is treated with 100-200 ml of distilled water, precipitation of silicic acid is carried out by adding 30-40 ml of concentrated hydrochloric acid solution and the solution is evaporated until the carbon dioxide is stopped in the sand bath. The precipitate is treated at least twice by adding 10-20 ml of concentrated hydrochloric acid solution, then 100-200 ml of distilled water is poured, after evaporation of the solution, silicon oxide (IV) is separated by filtration, washing the precipitate with a 0.5% hydrochloric acid solution .

Diatomite is a silica-containing raw material, a cemented rock of light gray color. A yellow tint appears in the powder. Diatomite powder is insoluble in acids (HCl, HNO ₃ , H ₂ SO ₄ ) and refers to acidic rocks. To transfer it to the solution, fusion is necessary. To obtain finely dispersed amorphous silica fume, the Atemar diatomite deposit (Republic of Mordovia) was used.

The method is as follows. Pre-crushed and ground in an agate mortar to a powder state, dried to 5-6% humidity and calcined in a muffle furnace at a temperature of 900-1000 ° C, diatomite weighing 5-8 g. A 6-fold amount of alkaline smoothing is ground in a porcelain mortar, consisting of from a mixture of anhydrous potassium and sodium carbonates (Na ₂ CO ₃ + K ₃ CO ₃ ). Diatomite and alkaline fluff are mixed in an alundum or corundum crucible.

The fusion of their mixture in a muffle furnace in an alundum or corundum crucible at a temperature of 800 ° C is carried out for 40-50 minutes, followed by pouring the melt on a silicate base. The melt is transferred to a heat-resistant glass, silicic acid is isolated by leaching of the melt with distilled water, heated to 70-80 ° C. The pH of the medium is monitored by titration with a 0.1 M solution of potassium hydroxide (KOH) with methyl orange. Processing of the melt is carried out with 100-200 ml of distilled water until complete dehydration of silicic acid (Si _n O _n-1 (OH _2n + 2)). Precipitation of silicic acid (Si _n O _n-1 (OH _{2n + 2} )) is carried out by adding small portions of 30-40 ml of a concentrated solution of hydrochloric acid (HCl) and after slowing down the reaction (NaKCO ₃ + 2HCl → CO ₂ ↑ + NaCl + Н ₂ O) evaporate the solution in a sand bath until the evolution of carbon dioxide (CO ₂ ) ceases. The precipitate is treated at least twice by adding 10-20 ml of concentrated hydrochloric acid (HCl) solution, then 1 100-200 ml of distilled water heated to 70-80 ° C is added, and the solution is evaporated in a water bath for 5 min. complete dehydration of hydrated silicon dioxide (IV) (SiO ₂ ). The pH of the medium is monitored by titration with a 0.1 M solution of potassium hydroxide (KOH) with methyl orange. The separation of silicon oxide (IV) (SiO ₂ ) is carried out by filtration, collecting the filtrate through a loose ashless filter (white tape) in a glass with a capacity of 400-600 ml and washing the precipitate with a 0.5% solution of hydrochloric acid (HCl) until a negative reaction to ions iron (III) with thiocyanate. The pH of the medium is monitored by titration with a 0.1 M solution of potassium hydroxide (KOH) with methyl orange. The precipitate is dried on a filter, then in a Petri dish in an oven at a temperature of 90-120 ° C.

The particle size of the obtained fine amorphous silica fume is determined using an optical microscope Nikon-LV-150. It was established that the obtained silica fume from the Atemara diatomite deposit has a size of 5-10 microns. The product yield from diatomite is 70-80%, the amount of moisture is up to 30%. The thermographic method proved that when the diatomite powder is heated from 70 to 165 ° C, the sample loses approximately 21% of its mass due to the removal of adsorption water. With increasing temperature to 250-400 ° C, the mass loss is 5.7%, probably due to the removal of pore water. With increasing temperature to 420 500 ° C, the mass loss is 1.7%. A further increase in temperature to 1200 ° C is not accompanied by a change in mass.

Compared with the known solution, the proposed solution allows to reduce the complexity of the process of leaching the melt from the crucible, which is an economical and energy-saving factor. In addition, it allows to increase the yield of finely dispersed amorphous silica fume up to 70-80%.

Claims (1)

A method of producing finely dispersed amorphous silica fume, including mixing pre-dried and calcined silica-containing raw materials with a 6-fold amount of alkaline fluff, fusing their mixture in a muffle furnace in a crucible, transferring the melt to a heat-resistant glass, releasing silicic acid by leaching the melt with distilled water, processing distilled water until complete dehydration of silicic acid, precipitation of silicic acid with a concentrated solution of hydrochloric acid, evaporating the solution until the carbon dioxide evolution ceases, processing the precipitate by adding concentrated hydrochloric acid solution, pouring distilled water and evaporating the solution in a water bath until the hydrated silicon oxide (IV) is completely dehydrated, separating silicon oxide (IV) is carried out by filtration, collecting the filtrate in a glass and washing the precipitate with a solution of hydrochloric acid until a negative reaction to iron (III) ions with rhodanide, the precipitate is dried on a filter, then in a Petri dish in an oven y carry out the monitoring of the pH of the medium by titration with a 0.1 M solution of potassium hydroxide with methyl orange after leaching, before filtering and after washing, characterized in that diatomite weighing 5-8 g is used as a silica-containing raw material, after mixing with alkaline fluff it is produced fusion of the mixture in a muffle furnace in an alundum or corundum crucible for 40-50 minutes, followed by pouring the melt onto a silicate base, transferring it to a heat-resistant glass, and isolating silicic acid first in By leaching the melt with distilled water, and then treating it with 100-200 ml of distilled water, silicic acid is precipitated by adding 30-40 ml of a concentrated hydrochloric acid solution, the solution is evaporated until the carbon dioxide is stopped in a sand bath, the precipitate is treated by adding 10-20 ml concentrated hydrochloric acid solution, then 100-200 ml of distilled water is poured, and after evaporation of the solution, silicon oxide (IV) is separated by filtration, washing the precipitate with a 0.5% solution of sal acid acid.