RU2806006C1 - Method for producing colloidal silver solution - Google Patents

Abstract

FIELD: chemosynthesis.

SUBSTANCE: synthesis of colloidal solutions of noble metals. A method for producing a solution of colloidal silver by preparing a reaction mixture containing silver nitrate, a stabilizer, a reducing agent, and then holding the reaction mixture according to a given temperature-time schedule is disclosed, while 0.5-1 ml of a sodium silicate solution with a concentration of 23 mg/ml is used as a stabilizer , which corresponds to 106-426% of Ag(I), a solution of glucose, xylose or fructose is used as a reducing agent, the consumption of monosaccharide solutions for preparing the reaction mixture is 0.5-1.5 ml, which corresponds to 28-169% of Ag(I), and the reaction is carried out in a boiling water bath for 5-30 minutes or in a microwave oven for 2 minutes.

EFFECT: expanding the range of stabilizers for colloidal silver solution and eliminating the release of strong-smelling ammonia during the synthesis reaction of colloidal silver solution under heating conditions.

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Description

The invention relates to the synthesis of colloidal solutions of noble metals and concerns methods for producing colloidal solutions of silver using stabilizers. A significant number of methods for the synthesis of colloidal silver solution are based on redox reactions [1].

Application area Links Catalysis [2], [3], [4], [5] Medicine [6], [7] Cosmetology [8] Agriculture [9], [10] Technique [eleven]

There is a known method for producing colloidal silver by reducing Ag(I), according to which a sample of silver nitrate up to 10% by weight of the solution is added to a solution of lignosulfonates (LST) with a concentration of up to 30% with stirring for 10 minutes. Then a reducing agent (sodium borohydride, ethyl alcohol and ascorbic acid) is added to the reaction mixture to 20% by weight of the solution and the reaction mixture is stirred on a magnetic stirrer for 1 hour. This forms a sol of spherical silver nanoparticles, stable for 6 months, with particle size about 20 nm. Instead of sodium borohydride, ethylene glycol (20 ml per 0.1 g of silver nitrate) is used as a reducing agent, and the reduction reaction is carried out at 80°C for one hour. Instead of sodium borohydride, ascorbic acid (700% by weight of AgNO ₃ ) is used, which is added portionwise to the reaction mixture over 30 minutes, after which it is stirred for one hour [12]. The disadvantage of this method is the long duration of the reduction reaction and the use of sodium borohydride, which is a toxic compound.

There is a known method for producing colloidal silver by carrying out the reduction reaction of silver(I) cations using a reducing agent. To do this, sodium lignosulfonate is initially oxidized at high temperature in an alkaline medium, after which the reaction mixture is acidified with sulfuric acid and sulfonated with sodium sulfite. After sulfonation, sodium chloride and starch are added with stirring to obtain a suspension, to which a solution of AgNO ₃ is added and silver(I) cations are reduced with sodium borohydride. After the synthesis of silver nanoparticles, enzymatic destruction of lignin is carried out, and nanosilver is extracted to obtain a paste with a uniform dispersion of nanosilver [13]. The disadvantage is the multi-stage process of obtaining colloidal silver.

There is a known method for producing colloidal silver by carrying out the reduction reaction of silver(I) cations. To do this, add 2.5 ml of silver salt with a concentration of 1 g/l to 1 ml of LST solution with a concentration of 12.5 g/l on a magnetic stirrer. The resulting solution is stirred for 24 hours and left for 7 days to complete the reaction [14]. The disadvantage of this method is the long duration of the reduction reaction.

There is a known method for producing colloidal silver by carrying out the reduction reaction of silver(I) cations using a reducing agent. To do this, an aqueous solution of LST with a concentration of 20 mg/ml (solution A) was prepared using ultrasound. Separately, an aqueous solution of an ammonia silver complex with a concentration of 5 mg/ml Ag(I) ions was prepared from _AgNO3 with a concentration of Ag(I) ions of 10 mg/ml and a 5 M aqueous ammonia solution was added to it. The solution was then diluted until the original volume doubled. Equal volumes of the prepared solutions were mixed, and the reaction was carried out at room temperature without stirring for the required time (from 2 hours to 10 days), which resulted in the formation of stable colloids of silver nanoparticles with an average particle size of 41 nm [15]. The disadvantage of this method is the long duration of the reduction reaction.

There is a known method for producing colloidal silver by carrying out the reduction reaction of silver(I) cations using a reducing agent. At the first stage of the synthesis, a hydrogel of modified sodium lignosulfonates (MSLS) is obtained; for this purpose, 2 g of sodium hydroxide and 6 ml of a 30% aqueous peroxide solution are added to 200 ml of a solution of sodium lignosulfonates (40 mg/ml). The resulting mixture is stirred on a magnetic stirrer for 30 minutes, and then 4 ml of sulfuric acid and 3 g of sodium sulfite are added. The solution is stirred at 90°C for another 90 minutes and cooled to room temperature. After cooling, 70 g of sodium chloride are added with stirring. After 40 minutes, the mixture is filtered under vacuum, the resulting solid is transferred to a watch glass and heated at 135°C in an oven for 90 minutes and then cooled to room temperature. 50 ml of an aqueous solution of sodium hydroxide (0.5 M) is added to the resulting solid and stirred at room temperature for 40 minutes, and then the fine solid from the suspension is separated by centrifugation and washed with deionized water until neutral, thereby obtaining modified LST particles hydrogel. Add 150 ml of deionized water to 8 g of undried particles of the LST-modified hydrogel in a test tube with stirring and disperse the resulting suspension with ultrasound for 150 min, and then add 0.5 ml of silver nitrate solution (0.5 M). The resulting mixture is subjected to supersonic dispersion for 5 minutes, then 2 ml of sodium borohydride (1M) is added and stirred on a magnetic stirrer at 25°C for 30 minutes, after which the resulting colloidal microhydrogel solution containing silver nanoparticles is dried at 40°C under vacuum to constant mass. In this case, spherical silver nanoparticles with a diameter of about 10 nm are obtained [16]. The disadvantage of this method is the long duration of the reduction reaction.

There is a known method for producing colloidal silver by carrying out the reduction reaction of silver(I) cations using a reducing agent. To do this, 1.5 ml of an organic solvent (1,4-dioxane, acetone or N,N-dimethylformamide), 1 ml of sodium lignosulfonate (12.5 g/l) and 2.5 ml of ammonia were added to 0.2 g of silicon dioxide. silver nitrate solution with a concentration of 1 g/l. After stirring for 10 min, the mixture was allowed to settle and the supernatant was removed. The solid was washed with an aqueous-organic solution in a ratio of 2:3 and dried [17]. The disadvantage of this method is the use of organic solvents.

There is a known method for producing colloidal silver by carrying out the reduction reaction of silver(I) cations using a reducing agent. To do this, an aqueous solution of silver nitrate is added dropwise to an aqueous solution of a reducing agent - alginic acid from the sodium salt of brown algae. Also for synthesis, a mixture consisting of 50% alginic acid from the sodium salt of brown algae and 50% LST is used. The synthesis is carried out with stirring for 5 days at room temperature. For each composition, two concentrations of silver ions are obtained, namely 1 wt.% (1Ag) and 5 wt.% (5Ag). It has been established that the optimal duration of synthesis is 72 hours. In this way, spherical silver nanoparticles with an average diameter of 10 nm are obtained [18]. The disadvantage of this method is the long duration of the reduction reaction.

There is a known method for producing a colloidal solution of silver by mixing solutions of silver nitrate, glucose and LST as a stabilizer, followed by alkalization with ammonia water and subsequent heating of the resulting mixture. In this case, the consumption of LST is 0.4...9.3 g per 1 g of silver (I), the consumption of glucose for the reaction is 1.7...25.0 g per 1 g of silver, and the consumption of ammonia water for alkalizing the reaction mixture is 6 ,1…45.8 g per 1 g of silver(I). Heating is carried out in a boiling water bath for 2...5 minutes or in a microwave oven for 45...90 s [19]. The disadvantages of this method are the high consumption of ammonia water and the release of strong-smelling ammonia when the reaction is carried out under heating conditions (prototype).

The objective of the invention is to expand the range of stabilizers for colloidal silver solution and eliminate the release of strong-smelling ammonia during the synthesis reaction of colloidal silver solution under heating conditions.

This is achieved by the fact that the reduction of silver(I) cations is carried out by heating according to a given temperature-time schedule in a microwave oven or in a boiling water bath (KBW) using a reducing agent, which is used as: glucose, xylose or fructose in the presence of sodium silicate , which is a stabilizer of a colloidal solution of silver. When performing syntheses, we used solutions whose characteristics are presented in Table 1.

Table 1 - Characteristics of solutions No. Substance Dimension Concentration 1 Sodium silicate mg/ml 23 2 Xylose mg/ml 6.1 3 Fructose mg/ml 6.0 4 Glucose mg/ml 6.1 5 Silver nitrate mg Ag/ml 10.8

The proposed method is carried out as follows. Initially, prepare a solution containing silver nitrate AgNO ₃ , a stabilizer, and a reducing agent. A colloidal solution of silver is formed by heating the reaction mixture according to a given temperature-time schedule in a boiling water bath (KBW) or in a microwave oven. 0.5-1 ml of sodium silicate solution with a concentration of 23 mg/ml is used as a stabilizer, which corresponds to 106-426% of Ag(I), a solution of glucose, xylose or fructose is used as a reducing agent, the consumption of monosaccharide solutions for preparing the reaction mixture are 0.5-1.5 ml, which corresponds to 28-169% of Ag(I). The reaction is carried out in a boiling water bath for 5-30 minutes or in a microwave oven for 2 minutes.

To control the formation of colloidal silver, photometric determination of the optical density of the solution at a wavelength of 430 nm was used. The choice of wavelength was made based on studying the electronic spectra. As can be seen from the figures shown in Fig. 1 of the electronic spectra, during the reaction a new absorption band appears with a maximum at 430 nm. These results are consistent with the data published in [20].

In addition, electronic spectra of silver nitrate solutions were recorded:

Example 1. In a 25 ml measuring tube, 0.5 ml of a glucose solution with a concentration of 6.1 mg/ml, which corresponds to 28% of the mass of Ag, and 0.5 ml of a sodium silicate solution with a concentration of 23 mg/ml, which corresponds to 106 % by weight of Ag, and 1 ml of silver nitrate solution with a concentration of 10.8 mg Ag(I)/ml, was heated on KVB for 5 min. After which the reaction mixture was cooled, the volume of the solution was brought to 25 ml with distilled water. As a result, a transparent colored solution was obtained and its optical density was measured at 430 nm on an Expert-003 photometer in a cuvette with a working layer length of 10 mm. The measured optical density at 430 nm was 0.449.

Example 2. Preparation of a colloidal solution of silver under the conditions of example 1, characterized in that the reaction time was 10 minutes. As a result, a transparent colored solution was obtained. The measured optical density at 430 nm was 1.057.

Example 3. Preparation of a colloidal solution of silver under the conditions of example 1, characterized in that the reaction time was 15 minutes. As a result, a transparent colored solution was obtained. The measured optical density at 430 nm was 1.189.

Example 4. Preparation of a colloidal solution of silver under the conditions of example 1, characterized in that the reaction time was 20 minutes. As a result, a transparent colored solution was obtained. The measured optical density at 430 nm was 1.310.

Example 5. Preparation of a colloidal solution of silver under the conditions of example 1, characterized in that the reaction time was 30 minutes. As a result, a transparent colored solution was obtained. The measured optical density at 430 nm was 1.434.

Example 6. Preparation of a colloidal solution of silver under the conditions of example 1, characterized in that the prepared reaction mixture was not kept in a boiling water bath (KBW), but the optical density was immediately measured. The measured optical density at 430 nm was 0.006.

Example 7. Preparation of a colloidal solution of silver under the conditions of example 6, characterized in that the reaction mixture was prepared without the use of a glucose solution; the prepared reaction mixture was kept on KVB. The heating duration was 30 minutes. The measured optical density at 430 nm was 0.001.

Example 8. In a 25 ml measuring tube, 0.5 ml of a xylose solution with a concentration of 6.1 mg/ml, which corresponds to 56% of the mass of Ag, and 1 ml of a sodium silicate solution with a concentration of 23 mg/ml, which corresponds to 426% of the weight of Ag, were mixed. mass of Ag and 0.5 ml of silver nitrate solution with a concentration of 10.8 mg Ag(I)/ml, were heated on KVB for 1.5 min. After which the reaction mixture was cooled, the volume of the solution was brought to 25 ml with distilled water. As a result, a transparent colored solution was obtained and its optical density was measured at 430 nm on an Expert-003 photometer in a cuvette with a working layer length of 10 mm. The measured optical density at 430 nm was 0.776.

Example 9. In a 25 ml measuring tube, 0.5 ml of a fructose solution with a concentration of 6.0 mg/ml, which corresponds to 56% of the mass of Ag, and 1 ml of a sodium silicate solution with a concentration of 23 mg/ml, which corresponds to 426% of mass of Ag and 0.5 ml of silver nitrate solution with a concentration of 10.8 mg Ag(I)/ml, were heated on KVB for 1.5 min. After which the reaction mixture was cooled, the volume of the solution was brought to 25 ml with distilled water. As a result, a transparent colored solution was obtained and its optical density was measured at 430 nm on an Expert-003 photometer in a cuvette with a working layer length of 10 mm. The measured optical density at 430 nm was 0.711.

Example 10. In a 25 ml measuring tube, 0.5 ml of a glucose solution with a concentration of 6.1 mg/ml was mixed, which corresponds to 56% of the mass of Ag, 1 ml of a sodium silicate solution with a concentration of 23 mg/ml, which corresponds to 426% of mass of Ag, and 0.5 ml of silver nitrate solution with a concentration of 10.8 mg Ag(I)/ml, were heated in the microwave (power 800 W) for 2 min. After which the volume of the solution was brought to 25 ml with distilled water by gravimetric method. As a result, a transparent colored solution was obtained and its optical density was measured at 430 nm on an Expert-003 photometer in a cuvette with a working layer length of 1 mm. The measured optical density at 430 nm was 0.755.

Example 11. Preparation of a colloidal solution of silver under the conditions of example 1, characterized in that the reaction was carried out without using a sodium silicate solution, and the reaction duration was 20 minutes. As a result, a silver mirror appeared on the walls of the measuring tube

Example 12. Preparation of a colloidal solution of silver under the conditions of example 1, characterized in that the consumption of the sodium silicate solution was 0.1 ml with a concentration of 23 mg/ml, which corresponds to 21% by weight of Ag, and the reaction duration was 20 minutes. As a result, a silver mirror formed on the walls of the measuring tube and a precipitate formed.

Example 13. Preparation of a colloidal solution of silver under the conditions of example 12, characterized in that the consumption of the sodium silicate solution was 0.2 ml with a concentration of 23 mg/ml, which corresponds to 43% by weight of Ag. As a result, the reaction mixture acquired a brown color, and the release of coarse particles was observed.

Example 14. Preparation of a colloidal solution of silver under the conditions of example 12, characterized in that the consumption of the sodium silicate solution was 0.3 ml with a concentration of 23 mg/ml, which corresponds to 64% by weight of Ag. As a result, the reaction mixture acquired a brown color, and the release of coarse particles was observed.

Example 15. Preparation of a colloidal solution of silver under the conditions of example 12, characterized in that the consumption of the sodium silicate solution was 0.4 ml with a concentration of 23 mg/ml, which corresponds to 85% by weight of Ag. As a result, the reaction mixture acquired a brown color, and the release of coarse particles was observed.

Example 16. Preparation of a colloidal solution of silver under the conditions of example 10, characterized in that the consumption of the glucose solution was 1 ml with a concentration of 6.1 mg/ml, which corresponds to 56% by weight of Ag. As a result, a transparent colored solution was obtained, and the optical density at 430 nm was 0.212.

Example 17. Preparation of a colloidal solution of silver under the conditions of example 16, characterized in that the consumption of the glucose solution was 1.5 ml with a concentration of 6.1 mg/ml, which corresponds to 85% by weight of Ag. As a result, a transparent colored solution was obtained, and the optical density at 430 nm was 0.297.

Example 18. Preparation of a colloidal solution of silver under the conditions of example 16, characterized in that fructose with a concentration of 6.0 mg/ml was used as a reducing agent, which corresponds to 56% by weight of Ag. As a result, a transparent colored solution was obtained, and the optical density at 430 nm was 0.839.

Example 19. Preparation of a colloidal solution of silver under the conditions of example 18, characterized in that xylose with a concentration of 6.1 mg/ml was used as a reducing agent, which corresponds to 113% by weight of Ag. As a result, a transparent colored solution was obtained, and the optical density at 430 nm was 0.898.

Example 20. Preparation of a colloidal solution of silver under the conditions of example 18, characterized in that the consumption of the fructose solution was 1.5 ml with a concentration of 6.0 mg/ml, which corresponds to 83% by weight of Ag. As a result, a transparent colored solution was obtained, and the optical density at 430 nm was 1.212.

Example 21. Preparation of a colloidal solution of silver under the conditions of example 19, characterized in that the consumption of the xylose solution was 1.5 ml with a concentration of 6.1 mg/ml, which corresponds to 169% by weight of Ag. As a result, a transparent colored solution was obtained, and the optical density at 430 nm was 1.344.

The results obtained are summarized in table. 1.

Thus, the invention makes it possible to eliminate the release of strong-smelling ammonia when carrying out the reaction under heating conditions and to obtain a stable solution of colloidal silver, stabilized with sodium silicate, the consumption of which is at least 106% by weight of Ag.

Table 1 Example Reducing agent Consumption of reagent solutions, ml Heating A ₄₃₀ reducing agent Na ₂ SiO _{3 AgNO3} duration, min way 1 glucose 0.5 0.5 1 5 KVB 0.449 2 glucose 0.5 0.5 1 10 KVB 1.057 3 glucose 0.5 0.5 1 15 KVB 1,189 4 glucose 0.5 0.5 1 20 KVB 1,310 5 glucose 0.5 0.5 1 thirty KVB 1.434 6 glucose 0.5 0.5 1 - without heating 0.006 7 - 0 0.5 1 thirty KVB 0.001 8 xylose 0.5 1 0.5 1.5 KVB 0.776 9 fructose 0.5 1 0.5 1.5 KVB 0.711 10 glucose 0.5 1 0.5 2 microwave oven 0.755 eleven glucose 0.5 - 1 20 KVB * 12 glucose 0.5 0.1 1 20 KVB ** 13 glucose 0.5 0.2 1 20 KVB ** 14 glucose 0.5 0.3 1 20 KVB ** 15 glucose 0.5 0.4 1 20 KVB ** 16 glucose 1 0.5 1 2 microwave oven 0.212 17 glucose 1.5 0.5 1 2 microwave oven 0.297 18 fructose 1 0.5 1 2 microwave oven 0.839 19 xylose 1 0.5 1 2 microwave oven 0.898 20 fructose 1.5 0.5 1 2 microwave oven 1.211 21 xylose 1.5 0.5 1 2 microwave oven 1,344

Notes: * - the silver mirror stood out; ** - a colored suspension with sedimenting coarse particles has formed.

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Claims (1)

A method for producing a solution of colloidal silver by preparing a reaction mixture containing silver nitrate, a stabilizer, a reducing agent, then holding the reaction mixture according to a given temperature-time schedule, characterized in that 0.5-1 ml of a sodium silicate solution with a concentration of 23 mg/ is used as a stabilizer. ml, which corresponds to 106-426% of Ag(I), a solution of glucose, xylose or fructose is used as a reducing agent, the consumption of monosaccharide solutions for preparing the reaction mixture is 0.5-1.5 ml, which corresponds to 28-169% of Ag (I), and the reaction is carried out in a boiling water bath for 5-30 minutes or in a microwave oven for 2 minutes.