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DEVICES AND METHODS OF EXTRACTING COLORFUL AND NOBLE METALS
INVENTION
Patent of the Russian Federation RU2147618

METHOD OF PURIFICATION OF NOBLE METALS FROM IMPURSES

Applicant's name: Lidia Alekseevna Voropanova
The name of the inventor: Lipia Alekseevna Voropanova
The name of the patent holder: Lipia Alekseevna Voropanova
Address for correspondence: 362031, Vladikavkaz, Pr-t. Kosta, 278, kv.127, Voropanova LA
Date of commencement of the patent: 1998.03.10

The invention relates to the extraction of substances by organic extractants from aqueous solutions and can be used in non-ferrous and ferrous metallurgy. The technical result is to create an efficient, inexpensive and selective method for purifying noble metals from impurities using a less volatile and easily accessible extractant. As an extractant, a mixture of oleic acid and triethanolamine is used, the inert diluent is machine oil, and extraction is carried out by continuously adjusting the optimum pH during the extraction. As an extractant, you can use the technical grease SP-3 (GOST 5702-75) , containing an inert diluent with the following ratio of components, mass% : oleic acid 10-12 , triethanolamine 4.5-6.0 , machine oil (inert diluent ) - the rest. By carrying out a fractional extraction with a gradual change in the pH of the solution towards increasing or decreasing and maintaining the altered pH value at each batch extraction operation, selective removal of impurities during the purification of aqueous solutions of noble metals is possible.

DESCRIPTION OF THE INVENTION

The method relates to the purification of aqueous solutions by organic extractants and can be used in non-ferrous and ferrous metallurgy, in the processing of waste from metallurgical industries, secondary raw materials, and for cleaning mine and mine waters, industrial wastewater.

A method is known for extracting noble metals from solutions by precipitation with metallic zinc [ Ripan R., Chetyanu I. Inorganic Chemistry, Part 2. - M .: Mir, 1972 ].

Disadvantages of the method are its complexity and high cost, its effectiveness depends on many factors (concentration, temperature, degree of ore crushing, presence of impurities, etc.).

The closest technical solution is the method of extraction of noble metals from solutions [Maslenitsky IN, Chugayev LV Metallurgy of precious metals. - M.: Metallurgy, 1972] . Quaternary ammonium salts such as trialkylbenzylammonium chloride, trialkylmethylammonium chloride, tetraalkylammonium chloride are used as the extractant. For extraction, these compounds are used as a 5-10% solution in some inert diluent.

Disadvantages of the method are multistage, high cost of the extractants used.

The object of the invention is to provide an inexpensive, efficient and selective method for purifying aqueous solutions of noble metals from impurities using an inexpensive, low-volatility and readily available extractant.

The technical result that can be achieved in the practice of the invention consists in a high degree of purification of solutions of precious metals from impurities with the possibility of selective extraction of the latter with simultaneous economy and safety of the process.

This technical result is achieved by the fact that in a known extraction method involving the addition of an extractant and a diluent in an aqueous solution, stirring, separation and settling of the phases, selective removal of impurities is carried out by extraction with a mixture of oleic acid and triethanolamine using an engine oil as an inert diluent, With continuous regulation of the optimum pH during extraction.

As an extracting agent it is possible to use the technical grease SP-3 (GOST 5702-75) , which contains an inert diluent, with the following ratio of components, mass% : oleic acid 10-12 , triethanolamine 4.5-6.0, machine Oil (inert diluent) - the rest.

By carrying out a fractional extraction with a gradual change in the pH of the solution towards increasing or decreasing and maintaining the altered pH value at each batch extraction operation, selective removal of impurities in the purification of aqueous solutions of noble metals is possible.

The essence of the method is explained with the data of FIG. 1-3 and tables.

METHOD OF PURIFICATION OF NOBLE METALS FROM IMPURITIES. Patent of the Russian Federation RU2147618 METHOD OF PURIFICATION OF NOBLE METALS FROM IMPURITIES. Patent of the Russian Federation RU2147618 METHOD OF PURIFICATION OF NOBLE METALS FROM IMPURITIES. Patent of the Russian Federation RU2147618

In Fig. 1-3 shows the results of extraction from nitric acid solutions of salts of silver ( Fig. 1 ), lead and silver ( Fig. 2 ), lead, copper and silver ( Fig. 3 ) as a function of the pH of the solution during extraction of the concentration of metal ions C , Mg / dm 3 .

The table shows the values ​​of the distribution coefficients K of metal ions between the oil and water phases, as well as the separation coefficients P of metal ions through the extraction day. The distribution coefficient K was calculated as the ratio of the metal ion concentration between the oil (excluding the inert diluent) and the aqueous phase. The partition coefficient P was calculated as the ratio of the distribution coefficients of lead and silver ions ( P Pb / Ag ), copper and silver ( P Cu / Ag ).

Extraction was carried out from aqueous nitric acid solutions of silver, or mixtures of lead and silver in a Pb: Ag ratio of 1: 1 , or lead, copper and silver in a Pb: Cu: Ag ratio of 1: 1: 1 , with a solution concentration of 500 Mg / dm 3 by the metal ion or by the sum of metal ions.

AgNO 3 , Pb (NO 3 ) 2 salts and Cu (NO 3 ) 2 · 5H 2 O crystalline hydrate were used for the preparation of the initial solutions. The extractant was added to the aqueous solution of the salts in an amount providing an oil-water emulsion with 5% by weight of the SP-3 technical lubricant.

Extraction was performed at different pH values ​​of the solutions. The pH was monitored with a pH- meter of the pH-121 grade. During extraction, the pH of the solutions varied, so the pH was adjusted to a given initial value by the acid HNO 3 or alkali NaOH . The regulation time is not more than an hour, because In the future, the acid-base characteristics of the solution changed insignificantly.

After a day or more, the oil phase was separated from the aqueous phase, then the aqueous phase was passed through a medium-density filter. In the filtered aqueous phase, the concentration of the metal ion was determined: lead by volumetric molybdate method, silver by titration with potassium thiocyanate, copper by volumetric iodometric method. The metal concentration in the organic oil phase was determined from the difference between the concentrations of metal ions in the initial solution and in the filtered aqueous phase.

Extraction was studied at room temperature.

EXAMPLES OF THE SPECIFIC PERFORMANCE OF THE METHOD

Example 1 (Figure 1, Table)
The extraction of silver ions from the nitric acid solution was studied in the interval 0 <pH <10 . The best extractions ( K = 29 and 105 ) were obtained respectively at pH = 6 and 9 . The minimum concentrations of silver ions in solution ( C = 424 and 270 mg / dm 3 ) were obtained at pH = 6 and 9, respectively. At pH 2 silver is not extracted. The extraction time is one day at pH 3-6 and two days at pH 7-9 .

Example 2 (Figure 2, Table)
The extraction of lead and silver ions from a nitric acid solution when they were combined was investigated in the range 0 <pH 8 . The best indices of silver ion extraction ( K Ag = 11-15 ) were obtained at pH5-6 , lead ions ( K = 30 and 120-446 ) at pH = 3 and 5-6, respectively. The minimum concentrations of silver ions ( C Ag = 236 mg / dm 3 ) and lead ( C Pb = 45 mg / dm 3 ) were obtained at pH7. The best separation indices P Pb / Ag = 10.94 - 30.40 were obtained at pH = 5-6 . Extraction time of 22 days at p H 1-2 , two days at pH3-4 , one day at p H = 5-6, 46 days at pH 7 . At pH> 8, there were difficulties in separating and settling the oil and water phases. At pH 2, after 22 days, a powdery precipitate of burgundy-violet color precipitates, and at pH7 after 46 days a powdered lilac-burgundy (black) color precipitates, with the concentrations of silver and lead ions in solution decreasing, as noted in Fig. 2 by the dotted line.

Example 3 (Figure 3, Table)
Extraction of lead, copper and silver ions from a nitric acid solution in their joint presence was studied in the range 0 <pH 8 . The best extraction indices of lead ions ( K Pb = 933-6127 ) were obtained at pH 6-8 , copper ( K Cu = 174-2694 ) at pH 5-8 and silver ( K Ag = 53 ) at pH = 1 and 6 -8 . The minimum concentrations of lead ions ( C Pb = 2-6 mg / dm 3 ) were obtained at pH 7-8 , copper ( C Cu = 4 mg / dm 3 ) at pH 8 and silver ( C Ag = 86 mg / dm 3 ) At pH = 1 and 6-8 . At pH3, silver is not extracted. The best separation indices of lead and copper ions ( P Pb / Cu = 14.04-22.70 ) were obtained at pH = 3-5 , lead and silver ( P Pb / Ag = 17.67-116 ) at pH 6-8 And 3 , copper and silver ( P Cu / Ag = 11.25-51.00 ) at pH = 5-8 and 3 . The extraction time is two days at pH = 1-3 and 7, six days at pH = 4 and 8 , one day at pH = 5-6 . After 35 days, a small powdered brownish-black precipitate precipitates in the filtered solution, with a slight decrease in the content of lead ions in the solution at pH4 , silver at pH 7 , the copper content is unchanged, the corresponding change in the concentrations of these ions in Fig. 3 is shown in phantom. At pH> 8, there were difficulties in separating and settling the oil and water phases.

METHOD OF PURIFICATION OF NOBLE METALS FROM IMPURITIES. Patent of the Russian Federation RU2147618

Depending on the pH of the solutions during the extraction process, the color of the oil phase in silver nitrate solutions changed - yellow at pH 5 and light brown at pH> 5 , in systems: lead-silver-brown with yellow inclusions at pH = 1-2 , light brown at pH = 3-4 , beige-yellow at pH 5-6 and brown at pH PH = 7-8 ; Lead-copper-silver-beige-yellow at pH 3 , beige with gray-lilac divorces at pH 4 , yellow-green at pH5 , green at pH = 6-7 , green with gray-lilac divorces at pH 8 .

The color of the aqueous phase in silver solutions is practically colorless, except for a slightly pink pH7 in the lead-silver-lilac system at pH1 and yellowish at pH> 1 ; in the lead-copper-silver system, the color of the aqueous phase is slightly salad throughout the pH range .

The change in the color of the oil, and in some cases of the aqueous phase, depending on the pH of the solution during the extraction process, is in accordance with the extraction pH interval of metal ions, which indicates the participation of metal hydroxo complexes during the extraction process.

The extraction mechanism is associated with the formation of complexes involving hydrated metal ions, triethanolamine and oleic acid.

The change in the pH of the solutions during the extraction process and the need to adjust it to maintain a constant pH during the extraction testify to the significant influence of the acid-base characteristics on the extraction course.

It has been experimentally established that, in comparison with individual solutions, the joint presence of lead and silver ions reduces the extraction rates of both ions at pH 6 ; at other pH values, the extraction parameters practically remain unchanged; The combined presence of lead, copper and silver ions does not change the extraction of lead, but increases those for copper and silver ions. The noted mutual influence of metal ions both improving the extraction results (synergism) and weakening the results of extraction (antagonism) provides additional opportunities for deeper extraction of the metals studied.

From the data of Examples 1-3, the following conclusions can be drawn:

1. High values ​​of the distribution coefficients of K metal ions in a certain pH range indicate the possibility of their deep extraction from aqueous solutions using this extractant.

2. Significant differences in the separation coefficients P of metal ions from unity made it possible to determine the conditions for the selective extraction and separation of these metals in their joint presence.

3. Taking into account that the metal separation coefficient depends on the extraction pH , by performing fractional extraction with a gradual change in the pH value of the solution towards increasing or decreasing and maintaining the changed pH value at each batch extraction operation, it is possible to selectively remove impurities in the purification of precious metal solutions.

4. A mixture of oleic acid and triethanolamine, a technical lubricant of grade SP-3 used as an extractant, are easily accessible and inexpensive compared to the usual extractants.

5. Engine oil contained in the composition of the lubricant and used in the extraction as an inert diluent is less volatile and therefore less flammable than commonly used.

The proposed method in comparison with the prototype is a more effective way of purification of aqueous solutions of precious metals from impurities with the possibility of their selective extraction with simultaneous economy and safety of the process.

The proposed method can be used for processing technological solutions, for treating wastewater from the ions under consideration, for purifying solutions of precious metal salts from impurities during the processing of slurries in metallurgical industries, and for secondary waste.

CLAIM

  1. A method for purifying aqueous solutions of noble metals from impurities by extraction, comprising introducing an extractant and an inert diluent into the aqueous solution, mixing, separating and settling the phases, characterized in that as a extractant a mixture of oleic acid and triethanolamine is introduced and extraction is carried out by continuously adjusting the optimum pH in Extraction process.

  2. The process of claim 1, wherein an inert diluent is machine oil.

  3. The process according to claim 1, characterized in that a lubricant containing oleic acid, triethanolamine and machine oil is used as an extractant and an inert diluent with the following component ratio, by weight :

    Oleic acid - 10 - 12

    Triethanolamine 4.5 - 6.0

    Engine oil (inert diluent) - Other

  4. The method according to any one of claims 1 to 3, characterized in that a fractional extraction is carried out with a gradual change in the pH of the solution and maintaining the changed pH of the solution at each batch extraction operation.

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Date of publication 05.12.2006гг