CS275824B6 - Method of isolating silver ion from solutions - Google Patents

Abstract

An ecologically significant method of isolating silver ions from solutions simultaneously containing alkali metal ions consists in adjusting the pH of the solution to a value higher than 1.5 with alkali metal hydroxide, after which it is brought into contact with a β-chelating sorbent obtained by the reaction of a copolymer of glycidyl methacrylate and ethylene dimethacrylate with diethylamine, and the captured silver ions are displaced with nitric acid.

Description

The present invention relates to a method by which silver ions can be isolated from solutions, using solutions with a very low concentration of silver ions, which also contain a significant proportion of other ions, in particular alkali metals, using a chelating sorbent, thus resolving the attack;

serious national economic problem of precious metal deficit losses

Silver, similar to other precious and precious metals, remains for its extraordinary | properties irreplaceable. However, its extension and very diverse use is not always pro- | adequate technology, which would strictly and thoroughly respect the application of deficit- | metal in the sense of measures guaranteeing maximum economy of operation or return of metal in the form of usable raw material. They mainly deal with chemical plants, which expensive and?

Precious metals are used for the production of catalysts or of spent catalysts you regenerate. Significant losses in these plants represent the leakage of precious and rare metals contained in the effluent

A large part of the work devoted to the isolation of silver ions from solutions deals with the study of:

effective sorbents, in particular chelating agents, which are characterized by increased selectivity for certain ions or groups thereof. Is this selectivity conditioned by the character?

reactive groups which are bound to the organic matrix of the synthetic resin, a considerable mechanical strength is already advantageous.

For example, a styrene-based resin has been applied to bind silver cations;

-divinylbenzene copolymer substituted with urea or iminodiacetic acid,% which reacts with all other heavy metals in addition to silver. A similar procedure has been developed to bind transition metals from contaminated water using a mercaptoethylene vinyl acetate copolymer. A selective ion exchange resin capable of binding heavy metals from industrial wastewater was prepared by alkylphosphonation of a styrene-divinylbenzene copolymer with bound amino groups. For the same purposes, an ion exchange resin based on polyhydroxamic acids and a resin obtained by reacting a styrene-divinylbenzene copolymer with carbamic acid ester derivatives were prepared. Acrylonitrile copolymer was also used as a heavy metal sorbent

and hydroxylamine modified divinylbenzene.

The disadvantages of the described methods are too expensive synthesis of proposed resins for industrial application, relatively low real sorption capacity for silver, application of less common eluents or difficult displacement of sorbed silver from the weakened polymer matrix.

The possibility of isolating silver ions from aqueous solutions was verified on ion exchangers:

which have gained ground in technical practice. However, the application of commercial ion exchangers has not been successful, especially due to the content of sodium ions present in the water. Conventional acidic cations have greater selectivity for alkali metal ions, and silver is virtually unbound.

Disadvantages of the above methods of silver isolation from solutions containing simultaneously:

alkali metal is eliminated by the invention, which consists in adjusting the pH of the solution to a value higher than 1 with an alkali metal hydroxide, after which it is brought into contact with a chelating sorbent of formula

G-COOCH_-CH (OH) -CH _o -N- (C _o H _c ) _o .

'Bbb O wherein G b denotes the polymer backbone, obtained by reacting a copolymer of glycidyl methacrylate and ethylendimetakrylátu diethylamine, containing 1.5 to 2.5 mmol g ^- ^ functional groups ^C H ₂ -CH _3?

^CH 2 ^{-CH 3} Captured silver ions or complex bound silver is recovered by elution with nitric acid after depletion of the sorption capacity of the resin. The sorbent column is regenerated after washing with water: by washing with an alkali metal hydroxide solution, the concentration is preferably 1. mol mol / l. This restores the original sorbent for reuse. . -—

An effective eorbent for use in the present invention is a macroporous copolymer of glycidyl methacrylate and ethylene dimethacrylate, obtained according to. author's certificate 162 535, containing diethylamine groups attached to a polymer backbone.

The isolation of silver ions from the solution by sorption on said resin takes place on the basis of the binding of silver to the complex with amine functional groups, not on the principle of ion exchange. Sodium ions do not participate in the formation of the complex, so they flow through the sorbent without being retained.

The chelating sorbent column is able to capture all silver ions as well as complex bound silver from the solution until its practical capacity is exhausted. When this occurs, the feed of the solution to be treated to the column is interrupted, the resin column is washed with water and a solution of eluting acid, preferably nitric acid with a concentration ranging from 2 to 5 mol 1 ", is introduced, with lower nitric acid concentration, the volume of the eluate increases. The obtained aqueous solution of silver nitrate can be returned, for example, to the catalyst production process or as a starting material for other adequate use.

The sorbent can be reused many times without changing its flow properties, shape and size of individual grains. Or its sorption capacity.

It is clear from the description that said method can be used not only for isolation of silver from waste solutions formed in the production of catalysts or processing of catalysts in case of depletion of their activity, but generally for isolation from solutions with low concentration of silver ions. content of this metal in the outlet water (0.5 to 0.05 mg Ag l ^- ^), and also for the separation of silver solutions, particularly from metals of main group, which do not form complexes, e N-nucleophilic centers sorbent.

The advantage of the process according to the invention is the possibility of capturing silver ions in addition to alkali metal ions, the use of a commercially available eluent and, last but not least, the easy preparation of a sorbent from commercially available substances such as glycidyl methacrylate and ethylene dimethacrylate.

The process for isolating silver ions from the solution according to the invention is documented by the following example.

Example »

1 g of dry sorbent obtained by reacting a glycidyl methacrylate-ethylene dimethacrylate copolymer with diethylamine containing 1.5 mol g of functional groups was charged to a 20 mm column. The height of the column was 50 mm. It flowed through the column within 20 min. 300 ml of a solution of pH = 12, which contained 0.01% by weight. Ag. 29.1 mg of silver were collected on the sorbent. The entire amount of bound metal was eluted with a volume of 20 ml of nitric acid with a concentration of 2 mol of 80 [mu] l of SM-HNO3. The silver ions were completely desorbed from the column packing and recovered as silver nitrate. After washing with water, the sorbent is regenerated with a 1 mol / l sodium hydroxide solution.

Claims (1)

PATENT CLAIMS Process for the isolation of silver ions from solutions containing simultaneously alkali metal ions, characterized in that the pH of the solution is adjusted to more than 1.5 with alkali metal hydroxide and then contacted with a chelating sorbent obtained by reacting a copolymer of glycidyl methacrylate and ethylene dimethacrylate with diethylamine and the trapped silver ions are displaced by nitric acid. 1