SU1758021A1 - Method of recovering silver from sewage - Google Patents

Abstract

Use: Wastewater treatment during film film regeneration. Summary of the invention: Wastewater is treated with CE-10-12 emulsion, containing May. %: polymethylsiloxane fluid 48; silicon dioxide 2; polyvinyl alcohol 2; distilled water 48, in the amount of 0.01-0.02 ml per 100 ml of wastewater, stirred by air and injected aluminum sulphate. The settling time is 2-3 hours, the residual silver content in the waste water is 5 mg / l. 1 tab.

Description

The invention relates to the treatment of wastewater in the chemical-photographic industry, in particular to a method for recovering silver during film film regeneration.

A known method for extracting silver from silver-containing wastewater is by chemical precipitation.

Iron sulfate is used as a precipitant in a mixture with sodium sulfate at a ratio of 2: 1.

The disadvantage of this method is the significant loss of cerebre during precipitation.

There is also known a method for extracting silver from wash water when film films are regenerated using ion exchange resins.

The disadvantage of this method is the loss of silver during extraction.

Closest to the proposed method is a method of extracting silver from silver-containing wastewater during the regeneration of photographic materials, including the deposition of silver-containing sludge with an aqueous solution of aluminum sulphate.

The disadvantages of this method are the loss of silver due to incomplete chemical precipitation and the presence of abundant foam on the surface of silver-containing waters.

The purpose of the invention is to increase the degree of silver recovery, shorten the deposition time and improve the phase separation conditions.

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For this, an emulsion (QE-10-12) containing May is introduced into the wastewater formed during the regeneration of photographic materials, before they are treated with aluminum sulphate. %:

Polymethylsiloxane

liquid (grade 200A) 48

Silicon dioxide

(brand Aerosil A-380) 2

Polyvinyl alcohol

(marks 8/14) 2

Distilled 48

in the amount of 0.01-0.02 ml per 100 ml of wastewater. Air mixing, precipitation and phase separation.

The emulsion of this composition is a white liquid with a kinematic viscosity of 35 mm2 / s, it mixes well with water.

CE-10-12 emulsion is an affordable product, manufactured by domestic industry according to TU 6-02-819-79. The use of this emulsion in the manufacture of technology, the emulsion does not have a smell, low toxicity, non-combustible and does not require special conditions of safety at work. The use of emulsion does not require installation of additional equipment. The emulsion is sprayed into the wastewater.

Example 1 (prototype).

100 ml of silver-containing water is poured into a cylinder with a capacity of 250 ml, while stirring with compressed air, an alkaline solution is added to a pH of 7.5-8, then a 10% solution of aluminum sulphate is added. The contents of the cylinder is stirred for 10 minutes. Viscosity of the precipitation is assessed. After 3 minutes, the supernatant becomes clear. The water is discharged for 4 hours. During the mixing of silver-containing effluent during the chemical deposition of silver, abundant foam appears, which after 4 hours (during the sedimentation of silver-containing sediment) does not break down, the silver content in the supernatant and sediment 13 mg / l.

Example 2 Into a cylinder with a capacity of 250 g ml, 100 ml of silver-containing water are poured. When mixing on the surface of the water abundant foam appears. For more complete silver precipitation and foam destruction, 0.01 ml of the CE-10-12 emulsion working solution, which contains 0.002 ml of the emulsion, is introduced, and the foam is destroyed. The pH of the effluent is adjusted with an alkali solution to 7.5-8. Then, mixing the contents of the cylinder with compressed air, a 10% solution of sulphate is introduced.

aluminum (alumina) During chemical precipitation, abundant foam reappears when the wastewater is mixed. Therefore, for the process

An insufficient amount of KE-10-12 emulsion was introduced. Time 2 hours,

Examples Zi4. The extraction of silver is carried out under the conditions of example 2, but the emulsion is introduced in amounts, respectively

0 0.004 ml and 0.006 ml per 100 ml of silver-containing effluent.

Example 5. In a cylinder with a capacity of 250 ml pour 100 ml of silver-containing water. When mixing on the surface

5 silver-containing effluent appears abundant foam. KE-10-12 emulsion is introduced in an amount of 0.01 ml per 100 ml of effluent. The foam disappears completely. Drainage is adjusted to ca. 7.5-8 with alkali solution. Mixing the cylinder content with compressed air, a 10% solution of aluminum sulphate (linose earth) is introduced. During the chemical deposition process, no foam appears on the surface of the effluent. Therefore, for the process, the necessary (optimal) amount of KE-10-12 emulsion was introduced; the silver content in the supernatant was 5 mg / l.

Examples 6 and 7. Experiments conducted

0 as in Example 5, but the emulsion is injected in amounts of 0.014 and 0.02 ml, respectively, per 100 ml of silver-containing wastewater.

Examples 8 and 9. Deposition is carried out.

5 silver under the conditions of example 2, but the emulsion was injected in amounts of 0.024 ml per 100 ml of silver-containing wastewater (example 8) and 0.03 ml per 100 ml of serbrosterous wastewater (example 9).

0 The results of anepizov in examples 1-9 are presented in the table.

From the table it follows that with the introduction of the emulsion in insufficient quantities (examples 2-4) the silver content in

5 of the supernatant is 6-9 mg / l and in the process of chemical precipitation the foam appears again.

When a larger amount of emulsion is injected (examples 8 and 9), the silver content in the supernatant does not decrease compared with the silver content in the supernatant in examples 5-7, while mixing silver-containing water during chemical

5 Deposition foam does not reappear.

Thus, as follows from the data in the table, the amount of KE-10-12 emulsion in the range of 0.01-0.02 ml per 100 ml of silver-containing effluent is optimal, since the addition of additional other transboundary amounts does not lead to a decrease in silver losses.

The introduction of the KE-10-12 emulsion into the silver-containing wastewater also makes it possible to shorten the precipitation time and sludge-containing sludge.

- According to the prototype, the time of sedimentation and settling down to the formation of a transparent supernatant is 4-6 hours, according to the proposed method - 2-3 hours.

The introduction of CE-10-12 emulsion also ensures complete destruction of the foam, which facilitates the process of chemical precipitation of silver and contributes to a more productive use of precipitation baths.

Claims (1)

Claims method of extracting silver from wastewater, including treatment with aluminum sulphate, precipitation and phase separation, characterized in that, in order to increase silver recovery, shorten the precipitation time and improve phase separation conditions, emulsion is introduced into the wastewater before aluminum sulphate containing May. %: Polymethylsiloxane fluid48 Silicon dioxide 2 Polyvinyl alcohol2 Distilled water48 in the amount of 0.01-0.02 ml per 100 ml of wastewater.