SU1606463A1 - Method of recovering silver from effluents - Google Patents

Abstract

The invention relates to wastewater treatment methods and is intended for the recovery of silver from wastewater primarily from the production and / or use of photosensitive photographic materials based on silver halides, as well as from wastewater from non-ferrous metallurgy enterprises and enterprises performing silver plating of metal products. The goal is to increase the degree of extraction of silver present in the wastewater as complex compounds. For carrying out the process, wastewater containing colloid-bound, ionic and complex-bound silver is treated with alkali to PH 10-11, potassium permanganate is added in an amount of 0.001 - 0.002% by weight of silver ions, aluminum sulfate in an amount of 0.5 - 0.7 g / l and bubbled with air. The resulting precipitate is separated. The process time is 80 minutes. The residual content of silver ions is 0.008 mg / l. 1 hp f-ly, 1 tab.

Description

The invention relates to methods for treating wastewater and is intended to extract silver from wastewater primarily from enterprises producing and / or using photosensitive photographic materials based on silver halides, as well as from wastewater from enterprises of nonferrous metallurgy and enterprises performing galvanic silvering of metallic materials. and non-metallic products.

The aim of the invention is to increase the degree of attraction by providing the possibility of extracting the silver present in the wastewater as complex compounds.

C p and meer. For the experiments, a mixture of real wastewater from the production of silver-containing photosensitive emulsions containing, according to the analysis, mg / l is used:

Colloid-bound silver21, 75

Ion silver .9,62

Complex io-c hp nn silver 15.38

s

Serial experiments on the recovery of silver from wastewater of the composition indicated are carried out according to the following general procedure. An aqueous solution of potassium permanganate containing 0.0005 mg of this syrup (O, 002% of the sum of the masses of ionic and complex-bound silver in a given volume of wastewater) is poured to 1 l of wastewater with continuous bubbling of compressed air and temperature. then aluminum sulphate is introduced in the amount of 0.5-0.7 g / l and the bubbling of the formed suspension with air is continued until the silver content in the liquid phase of the reaction mass ceases to decrease. For this purpose, samples (25-30 ml) are taken from the reaction suspension, they are filtered through a blue filter paper and the silver content is determined by atomic adsorption spectroscopy.

In the control series of experiments carried out according to the same method, instead of potassium permanganate, wastewater was injected with the same amount of selenous acid (a known method).

.Comparative results obtained under identical conditions are presented in the table,

From the data of the table, it follows that at room ambient temperature (20 + 2 ° C) and pH value of medium 10, the complex-bound silver ions are practically not destroyed by air oxygen in the presence of a catalytic amount of selenous acid, but remain completely in solution (see experiments .4-6). Under the same conditions, but in the presence of potassium permanganate, complete oxidation of simple and

five

0

five

0

five

40

complex-bound silver ions with atmospheric oxygen to double-divalent and trivalent silver (AgO Ag O-) practically insoluble in water (AgO Ag O-) ° C < D = 300% minimum residual silver content in the solution (0.008 mg / l); experiments 1-3).

Thus, the use of potassium permanganate as a catalyst, all other conditions being the same with the prototype method, increases the recovery of silver from the wastewater of enterprises producing and / or using photosensitive photographic materials due to the simultaneous precipitation of simple and complex-bound silver ions present in the original wastewater ..

Claims (2)

1. A method of extracting silver from wastewater, including oxidizing with air oxygen in an alkaline medium in the presence of a catalyst, introducing coagulant aluminum sulfate and separating sedimentation sediment, characterized in that, in order to increase the recovery rate, due to the possibility of extracting silver present waste water in the form of complex compounds, potassium permanganate is used as a catalyst. 2. Method POP1, characterized in that the process is carried out at a pH of 9-11, and the catalyst is introduced in an amount of 0.001-0.002% by weight of silver ions in the wastewater.