RU2319672C2 - Method of production of the quartz glass - Google Patents

Abstract

FIELD: glass industry; optical industry; other industries; methods of production of the quartz glass.

SUBSTANCE: invention is pertaining to production of the quartz glass for its application in optics and other branches of industry. In the capacity of raw use the siliceous valvar planes of the diatomic algae obtained from their biomass by removal of the organic elements of the cells. The technical result of the invention is simplification of production of the quartz glass from the amorphous silica at the expense of exclusion of the intermediate stage of microcrystallization of the amorphous silica indispensable for the moisture removal, and also for dilation of the raw materials base at the expense of usage of the renewable resources. The method provides for removal of organic elements of the cells of diatomic algae by serial action on algal biomass. At first exercise extraction of the algal biomass by the organic solvent for extraction of the fatty acids fraction. The separated settlings is subjected to action of the solution of SAS and the former of complexes with the subsequent separation of the settlings and its flushing and repeat this process 2-5 times. The produced settlings is treated with the mixture of the concentrated nitrogen and hydrochloric acids within 10-12 hours at the room temperature and boil in the portion of the inorganic acid for 2-3 hours. After boiling the purified settling in the form of the diatomic algae glumes is flushed by water and dried up producing the main product - the amorphous silica directly suitable for manufacture of the transparent quartz glass.

EFFECT: invention ensures production of the main product - amorphous silica directly suitable for manufacture of the transparent quartz glass.

10 cl, 8 dwg, 3 ex

Description

The invention relates to the production of quartz glass for use in optics and other industries.

Quartz glass, which is pure silicon dioxide (SiO ₂ ), has a number of unique properties compared to glasses of a different composition. These include a high melting point (softening point 1300 ° C), resistance to sharp temperature changes, chemical resistance to acids, high light transmission, including in the ultraviolet region of the spectrum. The optical properties of quartz glass have gained particular importance in recent years in connection with the intensive development of fiber optic communications. It should be noted that a necessary condition for obtaining high-quality quartz glass is the high purity of the feedstock, the content of impurities should not exceed 10 ^-6 -10 ^-2 %, depending on the field of application of the final product.

Known methods for producing quartz glass include melting of natural raw materials, which use natural varieties of rock crystal, vein quartz, quartz sand, i.e. crystalline minerals SiO ₂ [Chemical encyclopedia: 5 tons: 4: / Ch. ed. Zefirov N.S. - M .: Big Russian Encyclopedia, 1995. - P.421] [1].

The disadvantages of the known methods include the low prevalence of fairly pure rocks, the need for laborious processes for sorting, removal of surface contaminants by chemical etching in aggressive environments, etc.

Multistage processing of quartz-containing raw materials, including crushing, grinding, electromagnetic separation, scrubbing, flotation and heat treatment [Patent No. 2182113 RU, 2002] [2], makes the process of obtaining the target product time-consuming and material.

A known method of producing silica glass from synthetic polysilicic acid involves the extraction of quartz, its conversion either to volatile silicon compounds, such as chloride, alkoxysilanes, or to soluble salts - metal silicates [Chemical Encyclopedia: 5 tons - T.2 / Ch. ed. Knunyants I.L. - M .: Owls. encycl., 1990. - S. 508, 517, 520] [3].

The known method makes it possible to use traditional methods of purification of chemicals (rectification, crystallization, ion exchange) to obtain a product of the required purity even when using low quality raw materials.

Nevertheless, the complexity and multi-stage of the known method, the need for high temperatures, anhydrous environments, a significant amount of unused waste make the known method economically inefficient and environmentally hazardous.

One of the primary ways to solve the problem of rational production of quartz glass is to search for new sources of available raw materials.

As a source of silica, diatomite, consisting mainly of siliceous cusps of diatoms, is of particular interest. Currently, diatomite is mainly used as a filtering material, a filler of composites. Its direct use for obtaining optical quartz glass is impossible due to the high content of impurities of terrigenous particles. Even after special cleaning [US 006653255, 2003 [4]; US 005656568, 1997 [5]] diatomite contains impurities of iron and aluminum at the level of tenths of a percent and requires further purification, including the conversion into soluble salts of silicic acid [Application JP 2001097711] [6].

Known solutions in which silicon-containing plants are proposed to be used as a source of silica [Application US 20030133863 [7]; Application WO 2004073600 [8]]. In the known methods there is also a significant number of preliminary stages for the isolation and purification of silicon compounds, in which the carbonization of the plant mass, the conversion of silica to soluble salts of alkali metals, their purification and subsequent preparation of polysilicic acid from them are carried out.

In addition, the last stages of the preparation of polysilicic acid are the so-called "wet" process, which consists in the hydrolysis of alkoxysilanes or in the precipitation of the target product by the action of mineral acids on aqueous solutions of alkali or alkaline earth metal silicates [Euler R. Silica Chemistry // Trans. from English M .: Mir, 1982. [9]; Brinker C.J., Scherer G.W. Sol-gel science: the physics and chemistry of sol-gel processing // London: Academic Press, 1990 [10]].

The disadvantage of this approach is the fact that the final polysilicic acid obtained as a reaction of hydrolysis of alkoxysilanes [Application US 2005019243 [11]; Application US 2003157011 [12]; EP 1167309, 2002 [13]; CN 1458064, 2003 [14]] and by precipitation from solutions of silicates [US 006716408, [15]; Application US 2003131536 [16]; Application US 2003003041 [17]], has a developed spongy surface and contains a significant amount of bound water and silanol groups (Si-OH), which, when heated, condense to form siloxane bonds and release water.

The direct use of such a material in the production of transparent quartz glass is impossible due to the formation of micro- and nanobubbles arising from the evaporation of water. The resulting product has a spongy structure, poor mechanical and optical properties.

To eliminate this, it was proposed to convert amorphous polysilicic acid to crystalline quartz under the influence of catalytic amounts of metals and high temperatures [Application JP 2002020111] [18]. During this transformation, the content of water and silanol groups is significantly reduced, which allows the use of similar synthetic quartz to obtain glass. At the same time, the introduction of crystallization catalysts lowers the purity of the final products and thus narrows the scope of their possible application [Application US2003124044] [19].

There is a method in which it is proposed to synthesize polysilicic acid by the sol-gel method and crystallize it by heating at temperatures of 1300-1700 ° C for several days in the presence of noble metals [Application US2004089024] [20]. This method allows to obtain a microcrystalline product suitable for melting into optical quartz glass, but retaining all of the above disadvantages associated with the multi-stage process and the complexity of the individual steps.

The inventive method has no close analogue.

The technical result of the invention is to simplify the production of quartz glass from amorphous silica by eliminating the intermediate stage of microcrystallization of amorphous silica (obtaining quartz grains) necessary to remove moisture, as well as expanding the raw material base for its production through the use of renewable resources, increasing the degree of processing of biological raw materials.

The technical result is achieved by the fact that to obtain silica glass from amorphous silica, silica cusps of diatoms isolated from their biomass by removing organic cell components are used as raw materials.

The method involves the removal of the organic components of diatom cells by sequential chemical treatment of the algae biomass. To do this, first, the algae biomass is extracted with an organic solvent to extract the fatty acid fraction with separation of the sediment. After that, the separated precipitate is exposed to a solution of a surfactant and a complexing agent, followed by separation of the precipitate and its washing. The above process of exposure to the precipitate is repeated several times depending on the degree of purity of the feedstock. As a rule, it is enough to repeat the process 2-5 times. After that, the resulting precipitate is treated with strong mineral acids for 10-12 hours. It is possible to further purify the precipitate of diatoms with mineral acids with additives or their mixture to remove unwanted inclusions. The treated precipitate is separated and boiled in a new portion of a mineral acid or mixture of acids for 2-3 hours. After boiling, the purified precipitate in the form of valves of diatoms is washed with water and dried, obtaining the target product - amorphous silica.

The method may include additional purification of diatom valves after the stage of processing the precipitate by boiling in mineral acid or a mixture of acids. Moreover, their processing is carried out with a mixture of concentrated nitric and hydrochloric acids in a ratio of 1: 3.

A mixture of methanol and chloroform in the ratio of these components 2: 1 is used as an organic solvent for the extraction of the fatty acid fraction.

The impact of a surfactant solution and a complexing agent is carried out by heating to 95-100 ° C for 2-3 hours.

Sodium dodecyl sulfonate is used as a surfactant, and Trilon B as a complexing agent with their content of 20 g and 0.3 g per 1 liter of water, respectively.

As raw materials, diatoms grown under artificial conditions, for example, in a photobioreactor, are used.

As raw materials, diatoms of the species Synedra Acus grown in a freshwater culture medium are used.

The method provides for the possibility of using diatoms collected in a natural body of water.

Silica obtained by melting it in a high-temperature flame forms transparent quartz glass.

Diatoms (Diatomeae), proposed in this invention as a source of silica to obtain silica glass, are unicellular photosynthetic organisms that are widespread in natural reservoirs (ocean, lakes, rivers) and other habitats (snow, soil, tree bark). Ocean diatoms provide up to 20% of all primary photosynthetic production of the Earth and the same proportion of oxygen produced by plants. The number of species of diatoms, according to various estimates, ranges from 10 to 100 thousand. Their distinctive feature is the ability to assimilate silica from the environment and build from it its external skeleton, and the silica content in the mass of diatoms is 40-50%. Silicic acid in the form of a neutral molecule is captured from water and transferred into the cytoplasm of diatoms using a special membrane protein SIT [Hildebrand M., et.al. // Nature 1997, V.385. P.688; Grachev M.A. and others // Mol. Biology 2002, T.39, S.303; Grachev M.A. et al. // Diatom Res. 2005, V 20, P.409]. The selectivity of the transfer of silicic acid in the form of a neutral molecule determines the high purity of silica fume.

Diatoms are photoautotrophs, that is, only carbon dioxide, inorganic salts, mainly nitrates and silicates, as well as light, are needed for their nutrition. In this regard, the cultivation of diatoms in bioreactors does not require significant costs. At the first stage of the food chain, diatoms produce nutrients that are absorbed by other organisms. Such compounds include not only proteins, polysaccharides and nucleic acids, but also complex lipids, for example, essential polyunsaturated fatty acids, the isolation of which from diatoms is carried out to obtain medical and cosmetic preparations [Shahidi and Wanasundara, 1998; Food Sci. Technol. - v. 9, 230-240; Horrocks and Yeo, 1999, Pharm. Res. v.40, 211-225; patents FR 2795959, 2000; JP 57054595, 1982]. The extraction of such valuable products does not impede the use of silica diatoms for the production of quartz glass and provides integrated processing of raw materials.

Shutters of diatoms can be considered as a special form of amorphous silica with transparency [JDPickett-Heaps et. al. Diatoms: Life in Glass Houses // DVD Teacher's Textbook, Univ. Melbourne, 2003] [21] and high density - 2.07 g / cm ³ [Lisitsyn A.P. / Geochemistry of silica // Ed. N.M. Strakhov. M .: Nauka, 1966. - P.90] [22], which brings it closer in properties to quartz glass (density 2.2 g / cm ³ ) and indicates a low moisture content in it.

Figures 1-8 show microphotographs that clearly demonstrate the advantages of using silica from diatom valves compared to polysilicon feed.

Figure 1 shows electron micrographs of the cusps of diatoms Synedra Acus from Lake Baikal. The dense “smoothed” structure of diatom valves is clearly visible, due to their formation under strict control of biological systems and significantly different from the morphology of silica precipitated from sodium silicate shown in FIG. 2.

Figures 3 and 4 show a partial fusion of diatom leaflets in a high temperature flame. The dense smooth structure of the valves is visible.

Figure 5 shows the samples obtained by melting the valves of diatoms, made in reflected light on a dark background

Figure 6 shows photographs in reflected light on a dark background of samples obtained by melting polysilicic acid obtained by the action of hydrochloric acid on a solution of sodium silicate.

7 is a micrograph of a sample in transmitted light obtained by melting the valves of diatoms.

On Fig shows a sample of polysilicic acid in transmitted light.

The micrographs clearly show that the process of obtaining quartz glass in the framework of this invention proceeds without the formation of microbubbles, and typical for diatom micropores are delayed, which indicates the practical absence of water in the mass of diatomic silica. Fusion of diatom valves at a higher temperature makes it possible to obtain transparent silica glass, while fusion under the same conditions of polysilicic acid precipitated from sodium silicate results in an opaque, inhomogeneous, and brittle product (Figs. 6 and 8).

Example 1

To obtain silica glass, silica is obtained from the valves of Synedra Acus diatoms cultured in a photobioreactor.

The biomass of diatoms is cultivated in a photobioreactor, which is a tank equipped with a light source, a device for automatically maintaining and continuously recording a constant temperature of 15 ° C, an air sparging system, an agitator to prevent sedimentation of diatoms, while maintaining the integrity of their siliceous exoskeletons and a medium supply device for replenishment of the consumption of nutrients and obligate microcomponents.

As the culture medium using an aqueous solution of the following composition (mg / l): Ca (NO ₃ ) ₂ · 4H ₂ O - 20; KH ₂ PO ₄ - 12.4; MgSO ₄ · 7H ₂ O - 25; NaHCO ₃ -16; Na ₂ · EDTA - 2.25; H ₃ VO ₃ - 2.48; MnCl ₂ · H ₂ O - 1.39; (NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O - 1; vitamin B12 - 0.04; thiamine hydrochloride (vitamin B1) - 0.04; biotin - 0.04; Na ₂ SiO ₃ · 9H ₂ O - 28.4; FeCl ₃ - 1.6.

The constant composition of the medium is maintained by replenishing diverging nutrients. Biomass is sampled by filtering the culture fluid through a 60 micron filter.

To isolate lipids containing a fraction of polyunsaturated fatty acids, the biomass is extracted with a mixture of methanol with chloroform at a ratio of 2: 1. Removal of the remaining organic components of diatom cells is carried out by heating at 95-100 ° C in a solution (25 ml per 1 g of dry diatoms) containing 20 g of sodium dodecyl sulfonate and 0.3 g of Trilon B per 1 l of water for 2 hours, followed by separation of the precipitate filtering and rinsing with water. This operation is repeated 4 times. The resulting precipitate is treated with concentrated nitric acid brand "osch." quantitatively, 25 ml of acid per 1 g of precipitate for 12 hours at room temperature, after which it is poured with a fresh portion of acid and boiled for 2 hours. The resulting precipitate, which is a shutter of diatoms, is filtered off, washed with distilled water and dried at 120 ° C. All manipulations on the allocation of the valves are carried out in polyethylene, teflon or quartz dishes. The silica yield is 0.44 g per 1 g of the original dry diatom cells (yield is 44%).

The resulting silica is fused into glass using a high-temperature burner, for example, oxygen-propane. To do this, a quartz wand (diameter 3 mm) is heated before melting, immersed in a precipitate, melted in a burner flame, repeat this procedure at least five times until a quartz ball with a diameter of 6-8 mm is obtained, which is melted and stretched to form a colorless, transparent quartz threads.

Example 2

Synedra Acus diatom biomass is cultured in a bioreactor similarly to the method described in Example 1.

The selection of biomass is carried out periodically by filtering the culture fluid. After lipids are extracted by extraction with a mixture of methanol and chloroform at a ratio of 2: 1, the precipitate is kept at a temperature of 98-100 ° C in a solution (25 ml per 1 g of dry diatoms) containing 20 g of sodium dodecyl sulfonate and 0.3 g of Trilon B in 1 l of water for 2.5 hours, followed by separation of the precipitate by filtration and washing with water. The above operation is repeated 3 times. After processing the precipitate obtained with concentrated nitric acid of the brand “osch.” in a quantitative ratio of 25 ml of acid per 1 g of the precipitate, for 10 hours, the precipitate is poured with a mixture of concentrated nitric and hydrochloric acids in a quantitative ratio of 1: 3, respectively, and incubated for 5 hours. At room temperature. After separation of the precipitate, it is boiled in a fresh portion of mineral acid or a mixture of acids for 2-3 hours. After washing the precipitate and drying it, the desired product is obtained, alloying which gives high-quality quartz glass.

Example 3

The biomass of diatoms from Lake Baikal is harvested by trawling using a Jedi network with a mesh size of 80 microns.

To isolate lipids, in particular the fatty acid fraction, the algae biomass is extracted with a methanol-chloroform mixture (2: 1). Removal of the remaining organic components of diatom cells is carried out by heating at 95-100 ° C in a solution (25 ml per 1 g of dry algae) containing 20 g of sodium dodecyl sulfonate and 0.3 g of Trilon B per 1 l of water for 3 hours, followed by separation precipitate by filtration and washing with water. This operation is repeated 5 times. The resulting precipitate is treated with concentrated nitric acid brand "osch." in the amount of 25 ml of acid per 1 g of precipitate. It is kept for 12 hours at room temperature, after which it is poured with a fresh portion of acid and boiled for 2 hours.

Nitric acid is removed by decantation, the precipitate is poured with a mixture of concentrated nitric and hydrochloric acids in a ratio of 1: 3 in the calculation of 25 ml of acid per 1 g of precipitate and incubated for 2 hours at room temperature. The resulting precipitate, which is a leaflet of diatoms, is filtered off, washed with distilled water and dried at 120 ° C. All manipulations to clean diatom leaflets are carried out in polyethylene, teflon or quartz dishes. The silica yield is 0.44 g per 1 g of the original dry diatom cells (yield 44%).

The resulting product is fused into quartz glass as in example 1.

The inventive method opens up the possibility of obtaining quartz glass from amorphous silica without an intermediate stage of its microcrystallization (obtaining quartz grains), which is possible when diatoms are used as silica. One of the advantages of the proposed method is the possibility of the integrated use of renewable resources to produce valuable organic products, such as polyunsaturated fatty acids.

Information sources

1. Chemical encyclopedia: In 5 volumes. -: Volume 4: / Ch. ed. Zefirov N.S. - M.: Big Russian Encycl., 1995. - P.421.

2. Patent No. 2182113 RU, 2002.

3. Chemical encyclopedia: In 5 t .: - T.2: / Ch. ed. Knunyants I.L. - M: Owls. encycl., 1990 - S. 508, 517, 520.

4. US 006653255, 2003.

5. US 005656568, 1997.

6. Application JP 2001097711.

7. Application US 20030133863.

8. Application WO 2004073600.

9. Euler R. Chemistry of silica // Transl. from English M .: Mir, 1982.

10. Brinker C.J., Scherer G.W. Sol-gel science: the physics and chemistry of sol-gel processing // London: Academic Press, 1990.

11. Application US 2005019243.

12. Application US 2003157011.

13. EP 1167309, 2002.

14. CN 1458064, 2003.

15. US 006716408, 2004.

16. Application US 2003131536.

17. Application US 2003003041.

18. Application JP 2002020111.

19. Application US 2003124044.

20. Application US 2004089024.

21. J. D. Pickett-Heaps et. al. Diatoms: Life in Glass Houses // DVD Teacher's Textbook, Univ. Melbourne, 2003.

22. Geochemistry of silica // Ed. N.M. Strakhov. M .: Nauka, 1966 .-- p.90.

Claims (10)

1. A method of producing quartz glass from amorphous silica, characterized in that the silica flaps of diatoms isolated from their biomass are used as raw materials by removing the organic components of the cells, mainly by chemical means, for this purpose, the algae biomass is first extracted with an organic solvent in order to isolate the fraction fatty acids, then the separated precipitate is affected by a solution of surfactant and complexing agent, followed by separation of the precipitate and its washing, the process The precipitate is repeated several times, the resulting precipitate is treated with concentrated mineral acid or a mixture of acids, then the precipitate is separated and boiled in a new portion of mineral acid, the precipitate separated in the form of diatom leaves is washed with water and dried, obtaining the target product, alloying which get quartz glass. 2. The method according to claim 1, characterized in that after processing the precipitate with concentrated mineral acid or a mixture of acids or after boiling in a new portion of mineral acid, the precipitated precipitate in the form of valves of diatoms is further treated with a mixture of concentrated nitric and hydrochloric acids in a ratio of 1: 3. 3. The method according to claim 1, characterized in that the exposure to a surfactant solution and a complexing agent is carried out by heating to 95-100 ° C for 2-3 hours 4. The method according to claim 1, characterized in that the process of exposure to the precipitate is repeated 2-5 times. 5. The method according to claim 1, characterized in that the treatment with concentrated mineral acid or a mixture of acids is carried out for 10-12 hours, and boiling in a new portion of mineral acid for 2-3 hours 6. The method according to claim 1, characterized in that a mixture of methanol and chloroform in the ratio of these components is 2: 1 as an organic solvent, sodium dodecyl sulfonate is used as a surfactant, and Trilon B is used as a complexing agent. 7. The method according to claim 1, characterized in that use diatoms grown in artificial conditions 8. The method according to claim 1, characterized in that use diatoms grown in a photobioreactor. 9. The method according to claim 1, characterized in that use diatoms of the species Synedra Acus grown in a freshwater culture medium. 10. The method according to claim 1, characterized in that diatoms collected in a natural body of water are used.

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