JPS6086220A - Method for separating palladium from aqueous hydrochloric acid solution - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for separating palladium from an acidic aqueous solution of hydrochloric acid containing mainly P. spp. by a solvent extraction method.

A hydrochloric acid acidic aqueous solution containing gold and platinum group metals such as gold, palladium, platinum, and rhodium is produced, for example, in a copper electrolytic slime treatment process in copper refining.

When copper electrolytic slime is decomposed with nitric acid, a silver extract and a residue are obtained. When this silver extract is neutralized and a precipitate is obtained, which is dissolved in hydrochloric acid, gold, platinum, rhodium, and palladium are obtained. , an acidic hydrochloric acid aqueous solution containing a base metal is obtained.On the other hand, the above-mentioned acidic hydrochloric acid aqueous solution can also be obtained by subjecting this residue to acid treatment using hydrochloric acid and hydrogen peroxide.

The hydrochloric acid acidic aqueous solution thus obtained has a composition roughly as described above. That is, gold: sg7 is hereinafter referred to as #20. 7g/l or less, palladium: left ~ gOg/l, platinum 7
．． 2-3 o g7t, rhodium: O. , 2-10
g/l, bismuth:! ～go yt, tellurium: S～g (7 g/l N copper 10 g71 or less, lead: &g
/l or less, approximately 1 mole of hydrochloric acid.

Chemical precipitation separation methods have traditionally been used to separate gold, palladium, platinum, and rhodium contained therein from the above-mentioned hydrochloric acid acidic aqueous solution.
In practice, this method has a low separation efficiency for these metals, and not only does it require a complex and highly skilled process, but it also results in a low direct yield and a loss of time and money during the process. There were problems such as being large, so
Recently, it has become possible to simplify and shorten the processing process.
Solvent extraction methods, which have advantages such as sensitive selective separation of metals and easy purification and recovery of separated metals, have attracted interest, and various specific methods have been proposed.

As a method for separating gold, palladium, platinum, and rhodium contained therein from an acidic hydrochloric acid aqueous solution using a solvent extraction method, ferrous sulfate is added to precipitate gold, and the precipitate is separated. A method for separating the organic phase from which palladium has been extracted and the aqueous phase by contacting the obtained filtrate with an organic solvent containing di-n-hexyl sulfide as an extraction solvent is disclosed in JP-A-Sho! ;/ -g'
Publication l'102, JP-A-Sho & 7-7q/, 3! It is known from Publication No. r.

In addition, before solvent extraction of palladium using di-n-hexyl sulfide as an extraction solvent as described above, it is better to change the ionic state of platinum in the aqueous solution containing nosiladium from divalent to davalent. , the extraction and separation of palladium becomes more selective.
e 2/ p 2'l ~ 3/ "Se/active
SOノvgnt E+xtraatants for
the Refining of Pja-tinum
Metals J.

However, di-n-sulfide solution containing platinum, rhodium, palladium, bismuth, and tellurium in an acidic aqueous solution of hydrochloric acid
When palladium is extracted into the organic phase using an organic solvent containing hexyl, bismuth is also likely to be extracted into the organic phase, and the bismuth is then used to back-extract palladium in the organic phase with aqueous ammonia. This made phase separation difficult.

The present invention solves the problems of the conventional methods described above and provides a method capable of separating palladium from an acidic hydrochloric acid aqueous solution mainly containing platinum, rhodium, bismuth, palladium, and tellurium with good selectivity and efficiency. It is intended for the purpose of
This objective was achieved by using di-n-hexyl sulfide as the extraction solvent.

The present invention will be explained in detail below.

In order to separate palladium from a hydrochloric acid aqueous solution containing gold, platinum, rhodium, bismuth, palladium, and tellurium by the method of the present invention, gold is first separated, and then the platinum and rhodium contained therein are separated from the remaining liquid. After bringing it to a highly oxidized state, palladium is separated.

First, the gold is separated. If the gold is not separated, in the next step, when palladium is solvent extracted with di-n-hexyl sulfide, all of the gold will be extracted, and the extracted gold will be removed in the subsequent palladium back extraction with aqueous ammonia. This is because not only does it become a precipitate and contribute to the formation of crud, but it also contaminates the recovered palladium.

To separate gold, a known solvent extraction method using dibutylcarpitol as an extractant or a precipitation separation method using a reducing agent such as hydrazine, ferrous salt, hydrogen peroxide, oxalic acid, or sulfur dioxide gas can be applied. . Palladium is extracted with a solvent using gold, but some of the platinum and rhodium contained in the residual liquid as covalent and trivalent ions are partially extracted at the same time, reducing the separation efficiency of palladium. Before solvent extraction, each of the above divalent platinum and trivalent rhodium was
It is necessary to oxidize it to valence and hexavalence. This oxidation treatment
If covalent platinum and trivalent rhodium are present in trace amounts, they can be omitted. Suitable oxidizing agents to be used include chlorine gas, alkali metal hypochlorites, chlorates, perchlorates, and the like. Sulfide as an extraction solvent
When extracting palladium using hexyl, aromatic solvents such as Scherzol AB (trade name of Shell Chemical Co., Ltd.), which are immiscible with water, and Dosubu-dou Shersol T (both trade names of Shell Chemical Co., Ltd.) are recommended. Di-n-hexyl sulfide is diluted with an aliphatic solvent before use, and the present invention involves adding 3 to 10% of a higher alcohol by external volume to an extraction solvent consisting of such an extraction solvent and a diluent. This makes it possible to extract palladium while minimizing the extraction of bismuth into the organic phase.

If the amount of higher alcohol added is less than 3%, extraction of bismuth into the organic phase cannot be ignored, and phase separation becomes difficult when back-extracting palladium from the organic phase.

Furthermore, if the addition exceeds 72%, platinum coexisting in the aqueous solution is likely to be reduced to covalent, and platinum is likely to be extracted into the organic phase, resulting in a decrease in selective separation of palladium extraction. Note that it is better to use di-n-hexyl sulfide with a purity of about 97% by weight to suppress the extraction of bismuth and platinum into the organic phase than to use a purity of about 9 AMMk%. Although it is preferable in this sense, palladium can be extracted with sufficient selective separation even if the purity is about 96% by weight.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example / As a test aqueous solution, hydrochloric acid having the components and composition shown in Table 1 was obtained by dissolving in hydrochloric acid the precipitate generated by neutralizing the silver extract obtained by decomposing silver electrolytic slime with nitric acid. An acidic aqueous solution was used.

Table 1: After heating 7 parts of this solution to θC, add 100g of this solution,
/l of hydrazine hydrochloride, its redox potential is 7gOm
From V (saturated permanent electrode standard, omitted below) to Om
The gold was reduced by adding up to V. After filtering, washing, and drying the precipitated gold powder, what is the purity of the gold? It was 3.0% by weight. Further, gold removal liquid 7°31 having the components and composition shown in Table 2 was obtained.

Table a) Divide this gold removal solution into Otsu 0g and 0.31g, and the former solution is oxidized (ie, hypochlorous acid containing 3% by weight of available chlorine).
Add IJum aqueous solution to increase its redox potential.
After making m'V, the latter solution was used as a palladium solvent extraction test solution without being subjected to the oxidation treatment as described above. io of this test solution for each test.

Me was collected, and palladium was extracted from it using a 0 volume % solution of di-n-hexyl sulfide dissolved in Sherzol AB at a phase ratio (aqueous phase: organic phase, hereinafter omitted). I did it. 80% of the mixture of gold removal solution and organic solution
The mixture was stirred for 60 minutes and allowed to settle. The above organic solution had a purity (weight R%) as shown in Table 3, and n-hexyl alcohol was added as a higher alcohol (outer volume %). The extraction rate of this extraction into the organic solution is shown in the upper row of each column in Table 3.

Table 3: Back extraction of palladium from the extracted organic phase obtained:
This was carried out using a 6% by volume ammonia aqueous solution at a phase ratio of 2:3. The mixture of both solutions was stirred on the SC for 10 minutes to settle. The extraction rate into the aqueous phase by this back extraction is shown at the bottom of each column in Table 3. In this back extraction, formation of crud was observed in all comparative examples, and clear phase separation was difficult in Test A3, and clear phase separation was impossible in Tests A left and B.

Table 3 shows that if oxidation treatment is not performed, part of platinum and rhodium will be extracted at the same time as palladium, reducing the separation efficiency of palladium and n-hexyl-
It can be seen that without the addition of alcohol, bismuth is extracted at the same time as palladium to a large extent during extraction.

Example A hydrochloric acid acidic solution having the components and composition shown in Table y was obtained by subjecting the residue obtained by decomposing copper electrolytic slime with nitric acid to acid treatment using hydrochloric acid and hydrogen peroxide as a test aqueous solution. An aqueous solution was used.

After heating this solution to 60C, add 700g7
t of hydrazine hydrochloride was added to increase the redox potential to 900
The gold was reduced from mV to 630 mV. After filtering, washing and drying the precipitated gold powder, the purity of the gold was 9.
g, 0% by weight. In addition, 7.7 pieces of gold removal liquid having the components and composition shown in Table 5 was obtained.

Table 5 This degold solution was divided into two parts, 7.01 and 0.7, and the former was oxidized, i.e., an aqueous sodium hypochlorite solution containing 5% by weight of available chlorine was added, and its oxidation-reduction potential was was used as goomV, and the latter solution was used as a palladium solvent extraction test solution without being subjected to the oxidation treatment as described above. 100 ml (l) of this sample solution was sampled for each test, and the extraction of palladium from this was carried out using Scherzol AB with a phase ratio of /:/.
Di-n-hexyl sulfide was dissolved in and a 20% by volume solution was used.

Claims (2)

[Claims] (1) A hydrochloric acid acidic aqueous solution containing mainly platinum, rhodium, palladium, and base metals is brought into contact with an organic solvent containing 3 to 72% higher alcohol by volume and using di-n-hexyl sulfide as an extraction solvent. , a method for separating palladium from an aqueous hydrochloric acid solution, which comprises separating palladium from an aqueous solution in an organic solvent. (2) Claim (1), wherein the hydrochloric acid acidic aqueous solution that is brought into contact with the organic solvent is one in which the platinum and rhodium contained therein are oxidized to the states of valent and hexavalent ions, respectively. A method for separating palladium from an acidic aqueous solution of hydrochloric acid.