Method of recovering palladium from solutions

FIELD: waste water treatment and hydrometallurgy.

SUBSTANCE: invention relates to recovering palladium from nitric acid, nitric acid-hydrochloric acid, and nitric acid-fluoride-hydrochloric acid solutions used for etching parts and units of equipment for isotope separation chambers. Palladium is sorbed from solutions having nitric acid concentration 30 to 250 g/L with mixture of epoxypolyamine-type low-basicity anionite, containing alternating groups of secondary and tertiary amines, ethers, and alcohols, and high-basicity anionite with quaternary ammonium base groups, content of low-basicity anionite (e.g. AN-31) being 98-99% and that of high-basicity anionite (e.g. AV17*8) 1-2%. Thereafter, anionites are subjected to stepped combustion: first for 2-4 h at 350-400°C and then for 2-4 h at 950-1000°C to produce metallic palladium, which is cooled under vacuum or in an inert gas atmosphere.

EFFECT: increased selectivity of refining process removing polyvalent metal impurities and increased degree of recovery.

6 tbl, 5 ex

 

The present invention relates to the use in isotope production methods extraction of palladium from nitric acid, azotnokremnistyh and nitrogen fluoride-hydrochloric acid solution etching of parts and components of equipment cameras isotope separation and can be used in metallurgical and chemical production of palladium and its compounds, while removing from solutions with high content of impurities.

The method for extracting platinum group metals produced from anode slimes of copper-Nickel production (Wasalamu "Analytical chemistry of platinum group metals" - M Editorial URSS, 2003, s). This method consists in the following. Nitric acid solution obtained after leaching anode slime containing hydrochloric acid, subjected to recover the alcohol. Formed nitrotoluene palladium compounds destroy hot water. Then the solution is treated with excess ammonia. First roll mixed ammonium-chloride complex salt of palladium, which then dissolves in excess ammonia. After dissolution of the palladium compounds in the solution was added hydrochloric acid. In the fall of poorly soluble precipitate of chloropyridazine. For peredishki salt of palladium conduct multiple dissolution of chloropyridazine in ammonia with subsequent besieged the eat hydrochloric acid to obtain a compound of the required purity. Precisely chloropalladite calcined getting spongy palladium.

The disadvantage of this method is that it does not provide selective and complete removal of palladium from solutions with high content of impurities of chromium, iron, titanium, lead, bismuth, tin and other elements. Another significant disadvantage of this method is the high consumption of reagents with a large number of operations, sedimentation, filtration and dissolution, which in turn significantly increases the duration of the process of selection of palladium.

Known analogues of the closest to the technical essence and achieved result, i.e. the prototype of the proposed method is a known method of extraction of palladium from solutions (Patent No. 2111272 MKI722 In 11/00, 3/24). The way the prototype is the following. Nitric acid solutions containing palladium, brought into contact with a macroporous anion exchange resin based on 2-methyl-5-vinylpyridine) - derivatives and divinylbenzene, for example EAP-1P. After sorption of palladium desorption from the resin is performed with the ammonia solution. Eluate are further used in the production of metallic palladium

The known method makes it possible to remove the palladium from nitric acid solutions containing in addition to palladium, the relatively low number of ions is elebra and copper and some other elements, for example, ions of alkali and alkaline earth metals.

The disadvantage of this method is unsatisfactory completeness of extraction of palladium and low selectivity of the anion VP-1P when removing PD from nitric acid solutions with a high concentration of ions of polyvalent metals (Fe(III), CR(VI), Ti(IV), Mo(VI) and others), and in the presence of anions of fluorine and chlorine. According to the method along with palladium is the sorption of ions of chromium, iron, titanium and some other items. In the presence of these impurities, the degree of extraction of palladium does not exceed 92-94%. Obtained from the eluates palladium metal contains up to 4% of impurities, which requires an additional operation prochistki metal.

The technical result of the invention is to eliminate the above disadvantages of the known method and the provision of conditions for enhancing the selectivity of the process of purification from admixtures of polyvalent metals and the degree of extraction of palladium.

The technical result is achieved due to the proposed method of extraction of palladium from nitric acid solutions, which differ from the known fact that the sorption of palladium lead from solutions with concentrations of nitric acid 30-250 g/l of a mixture of weakly basic anion exchange resin epoxypropanol type, with alternating groups of secondary and tertiary amines, ether spirtovyh groups and strong-base anion exchanger with Quaternary ammonium groups of the base, when the content of the weakly basic anion exchange resin, for example, EN-31, 98-99 wt.% and strong-base anion exchanger, for example AV*8, 1-2 wt.% with the next step burning anion exchange resin in the first stage within 2-4 hours at a temperature of 350-400°and 2-4 at a temperature of 950-1000°obtaining metal palladium and its cooling under vacuum or in an atmosphere of inert gas.

It should be particularly noted that the high degree of extraction of palladium at high selectivity of the process is not observed at a particular anion exchange resin. Experiments have shown that if you use only weakly basic anion exchange resin epoxypropanol type, sorbed about 94-96% of palladium. When used to extract only the strong-base anion-exchange along with palladium observed sorption of ions of impurities of chromium (VI), iron (III), titanium (IV). And only a mixture of anion exchange resin in the specified proportions provides a degree of extraction of palladium and 99.8-99.9% of the high selectivity of the process. Chrome compounds of iron, titanium and other impurities practically not retrieved by this mixture of anion exchange resin.

The use of a mixture of anion exchange resin is a necessary but insufficient condition for achieving the objectives of this invention is the complete removal of the high selectivity of the process. Experiments showed that this goal is realized only when following three conditions:

see the camping anion exchange resin;

- a certain acidity of a solution;

- burning a mixture of anion exchange resins under certain temperature conditions obtaining palladium metal and cooling it in a vacuum or in an atmosphere of inert gas.

When the concentration of the nitric acid below 30 g/l is observed, along with the growth of sobiraemosti palladium, high sobiraemosti impurities, in particular ions of chromium and iron, which leads to significant contamination of palladium. Subsequent washing of the anion exchange resin solutions of nitric acid with a higher concentration of NGO3not only leads to desorption of the impurities, but also partial desorption of palladium. When the acid concentration of more than 250 g/l is drastically reduced sobiraemosti palladium. Moreover, prolonged contact with the mixture of anion exchange resin with a solution containing more than 250 g/l NGO3there is a partial destruction of the anion exchange resin with a transition of a certain number of adsorbed palladium in solution.

Sorbed mixture of anion exchange resin palladium has a fairly high degree of purity (at least 99%), so the anion exchange resin is advisable to undergo thermal degradation with obtaining metal. Complete burnout of the anion exchange resin is at a temperature of 950-1000°C. With palladium is a catalyst for a complete burnout of the anion exchange resin. In the absence of metal, the anion exchange resin is not completely burn out. The amount of ash after combustion is pure anion exchange resin ranges from 20-25%. However, incineration of ion-exchange resin at a temperature of 950-1000°With results in large losses (20%) of the metal with the exhaust gases. Therefore, the main thermal decomposition, at a temperature of 350-400°C. When this burns out about 40-45% of the anion exchange resin. Subsequent oxidation of the resin is carried out at a temperature of 950-1000°C. In this mode, the combustion anion exchange losses of palladium was observed. Cooling the obtained metal should be carried out in vacuum or in an atmosphere of inert gas to prevent oxidation of the parts of palladium.

Thus, the analysis of the proposed technical solution shows that between features of the proposed method and achieve this result there is a new cause-and-effect relationship: the presence of a characteristic set of features provides a positive effect, and the absence of any signs proposed technical solution makes it possible to obtain a positive effect of increasing the degree of extraction of palladium at high selectivity of the process.

In the patent and scientific literature there is no information about the possibility of increasing the degree of extraction of palladium while increasing the selectivity of the process by sorption of palladium on a mixture of base and strong base anion exchanger from nitric acid solutions with concentration is the situation of nitric acid 30-250 g/l with the subsequent receipt of metallic palladium thermal degradation of anion exchangers with cooling of the metal under vacuum or in an atmosphere of inert gas. Therefore, the proposed technical solution is characterized by novelty and has significant differences.

Comparison of the performance of the proposed and previously known methods (analogue and prototype), as well as a quantitative justification of the ratio of the anion exchange resin in the mixture, the pH of the solution at adsorption and thermal decomposition of the examples.

The proposed method is as follows.

Nitrate solution containing palladium and impurities, lead contact in static or dynamic conditions (e.g., passed through the sorption column) with a mixture of anion exchange resin (basic epoxypropanol type, with alternating groups of secondary and tertiary amines, ether and alcohol groups) and strong-base anion exchanger with Quaternary ammonium groups of the base. Sorption in static conditions are within 72 hours, and in dynamic conditions before the advent of palladium ions in the filtrate with a concentration of 3 mg/l After sorption of the anion exchange resins are washed with water, dried in air and subjected to thermal decomposition with production of metal palladium.

Example 1. 100 ml of nitric acid solution with a concentration of NGO363 g/l of palladium - 1.5 g/l of chromium (VI) - 10 g/l, iron (III) - 15 g/l, titanium (IV) 1 g/l, was brought into contact with 1 g of anion exchange resin. After 72 hours, the solution was separated from the of Orbeta and analyzed for the residual content of components. According to the difference of concentrations of components in the original solution and the solution after contact with the ion exchangers were determined sobiraemosti metal ions.

It follows from the presented results the greatest sobiraemosti palladium is observed on a mixture of anion exchange resin an-31 (98-99 wt.%) and AB-h (1-2 wt.%), at high selectivity. Sorption of impurities in a mixture of anion exchange resin was not found.

The results obtained are shown in table 1.

The increase in the content of strong-base anion exchanger AV-h leads to sorption of ions of impurities of chromium, iron, titanium. Use only slightly basic anion an-31 significantly reduces the degree of extraction of palladium, although there is a high selectivity of the extraction of PD(II).

Example 2. Solutions (100 ml)containing palladium ions and impurities and with different concentrations of nitric acid was brought into contact with the anion exchange resin (1 g) for 72 hours. After adsorption in solutions was determined by the residual concentration of metals in solution. The results of the experiments are presented in table 2.

The resulting set of experiments, the data show that the mixture of the anion an-31 (98%) and AB-17 (2%) provide a high degree of extraction of palladium from nitric acid solutions, while maintaining high selectivity in the concentration range of NGO330-250 g/L. in Addition, there is a considerable excess sorption of ballad which I compared with the anion exchange resin VP-1P (prototype).

Example 3. A mixture of anion exchange resin of the proposed method and the anion exchange resin VP-1P (prototype) was brought into contact with various etching solutions of palladium isotope. The composition of these solutions on the main components are given in table 3.

As follows from the data presented, the solutions are complex composition with a high content of impurities. The results of the sorption of palladium are shown in table 4

Data in table 4 reflect a significant advantage in the sorption properties of a mixture of anion exchange resin of the proposed method in comparison with the known technical solution. A very significant reduction in sobiraemosti palladium by ion-exchange resin EP-1P may occur if nitrate solutions are anions of fluorine and chlorine.

Example 4. Comparison of the sorption of palladium in dynamic conditions was carried out on the solution. Column 15 mm diameter were loaded with a mixture of anion exchange resin an-31 and AB-17 (proposed method) and anion exchange resin VP-1P (prototype). The solution was filtered through a bed of anion exchange resin at a rate of 1 ml/min·cm2to equalize the concentrations in the initial solution and the filtrate. When conducting this experience was defined dynamic exchange capacity (the capacity of the anion exchange resin to slippage of palladium in the filtrate) and the full dynamic exchange capacity. The results of the experiments are presented in table 5.

Thus, before ageme technical solution has a significant advantage over known as the degree of extraction of palladium from nitric acid solutions of complex composition due to higher capacitive characteristics of the mixture of anion exchange resin, and the selectivity of the extraction RD.

Example 5. Burning a mixture of anion exchange resin was carried out at different modes. After adsorption of the anion exchange resin was rinsed with water from the mother liquor, in order to remove impurities from the phase sorbent from the mother liquor. After that, the resin was dried in air to a moisture content of 25-30%. After that was loaded into lundbye crucibles and subjected to thermal degradation at different temperature regimes. The heating rate muffle furnace averaged 10°in a minute. Card temperature processing with the release of palladium after the destruction of the anion exchange resin presented in table 6.

As follows from the obtained data, the maximum yield of metallic palladium was achieved in 2 and 3 experiments, i.e. by pre-exposure of the resin at a temperature of 350-400°C for 2-4 hours, followed by oxidation of the anion exchange resin during the same time at a temperature of 950-1000°C. it Should be noted that during cooling of the metal in the air was the oxidation of palladium and oxygen content in the metal reached 5-11%. When cooled under vacuum or in an argon atmosphere oxidation did not occur and cooled in the metal, resulting in the form of powder color is on almost were not found.

The method of sorption extraction of palladium from nitric acid solutions, including sorption resin, characterized in that the sorption of palladium lead from solutions with concentrations of nitric acid 30-250 g/l of a mixture of weakly basic anion exchange resin epoxypropanol type, with alternating groups of secondary and tertiary amines, ether and alcohol groups, and strong-base anion exchanger with Quaternary ammonium groups of the base, when the content of the weakly basic anion exchange resin, for example, EN-31, 98-99 wt.% and strong-base anion exchanger, for example AVG, 1-2 wt.%, followed step by burning a mixture of anion exchange resin in the first stage for 2-4 hours at a temperature of 350-400°and the second for 2-4 hours at a temperature of 950-1000°obtaining metal palladium and its cooling in vacuum or in an atmosphere of inert gas.



 

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