The present solution relates to an industrial process for obtaining highly concentrated and purified solutions of nickel(II) nitrate(V) from waste solutions of nickel containing sulphate and/or chlorides. Multicomponent solutions, containing nickel, directed into the process according to the present invention, may be of varying origin, from solutions from liming primary (ores, concentrates, smelting products) and secondary materials (scrap, recycled materials - batteries, catalytic converters) to waste solutions from technological processes (post-rinsing liquid, post-crystallization bases and others).

Highly purified solutions of nickel nitrate obtained according to the present invention are a desirable resource for the chemical industry. The main use of nickel nitrate is the production of catalysts particularly sensitive to sulphur compounds, as well as in the production of nickel-cadmium batteries. It is also used in the manufacturing of products used in the initial processing of metals prior to painting and cold-shaping. In most industrial uses of nickel nitrate, it is inadmissible for it to be contaminated with other metals or salts, particularly sulphates or chlorides.

According to the known, most commonly used method, nickel nitrate is obtained by dissolving metallic nickel in nitric acid. The reaction is performed in a sealed, stainless steel or glass reactor. NO and N02 are released during the reaction. These are removed from the gas stream by rinsing with water in a column forming nitric acid that returns to the process, or catalytically. Solid nickel nitrate is obtained from the solution by concentrating it.

The apparatus is cleaned with water, and the effluent is directed to the municipal sewage system.

Patent PL86221 describes a method of reclaiming nickel from waste baths and sediments in the form of nickel sulphate solutions with a stable pH that ensures the removal of iron, aluminum, chromium, copper and zinc, characterised in that the acidic solution containing nickel sulphate, iron, aluminum, chromium, copper and zinc or acid is put into contact with a suspension of hydroxides, carbonates or basic carbonates of these metals obtained possibly from waste nitrate baths for the electrolytic removal of faulty coatings or passed through a layer formed therefrom.

Patent PL 129 135 describes the reclamation of copper and nickel from acidic solutions, particularly electrolytes taken out of copper electrorefinement. The known method is based on the fact that the acidic solution containing copper and nickel is put into contact with crushed rock containing magnesium and preferably nickel minerals, meaning serpentinite and/or magnesium, in a multi-stage countercurrent system, and between the stages of this contact as well as after its completion copper is extracted using organic compounds or mixtures containing hydroxyl and oxime functional groups. The amount of rock containing magnesium and preferably nickel minerals put into contact with acidic solutions containing copper and nickel, are selected such that the solution directed to copper extraction has pH = 1-3. The aqueous solution obtained following the extraction of copper, containing amongst others nickel sulphate and contaminates from both the initial solution as well as those from the digestion of the rock is neutralised to a solution pH of 3-4 in order to precipitate metal hydroxides, except nickel hydroxide. Nickel is extracted from the purified solution in several steps of a countercurrent system using a 30% 2-hydroxy-5-nonylbenzophone oxime solution in a crude oil fraction. Nickel extraction is conducted by adding ammonia at each stage of the extraction such that the pH of the solution is no lower than 6, such that as the concentration of nickel in the aqueous solutions drops in consecutive stages of the extraction, the pH increases stepwise to 8.5. Next, the organic phase is re-extracted with sulphuric acid solutions in three steps such that the post-extraction pH is above 2.5. Nickel is isolated from such a sulphate solution through electrolysis.

The known methods produce possibly initially purified solutions of nickel sulphate. These are not nickel nitrate sources for industrial use, particularly due to the insufficient degree of purity and highly undesirable sulphate content.

Patent US 6733564 describes a method of reclaiming nickel from used up catalysts. Likewise, this process only results in a purified solution of nickel sulphate.

Despite the existence of fully operational industrial installations for the solvent extraction of nickel, particularly as a sulphate, it is still desirable to deliver novel, industrially useful methods of obtaining highly pure solutions of nickel nitrate. It is particularly desirable to deliver a method which would not require metallic nickel, but that would facilitate the production of purified solutions of nickel nitrate from waste solutions of nickel containing sulphate and/or chlorides.

Unexpectedly, such a method is described in the present invention.

The subject of the present invention is a method of industrially obtaining purified and concentrated solutions of nickel(II) nitrate(V) from waste solutions of nickel containing sulphates and/or chlorides by way of solvent extraction, encompassing cationic ion exchange extraction, characterised in that a waste aqueous solution with a nickel content from 1 to 10 %, by mass, preferably initially heated with active carbon and then filtered, is subjected to extraction with a solution of liquid cationite in heavy dearomatised white spirits, wherein, during the extraction, the ratio of solutions of nickel to cationite solution varies in the range from 0.25 to 2.5, the emulsion pH is maintained in the range from 3.5 to 4.5 and the temperature is from 30 to 50°C, then the organic and aqueous phases are separated, and nickel extraction is performed into solutions of higher aliphatic acids selected from a group encompassing: di-2-ethylhexylphosphoric acid, di(2,4,4-trimethylpentyl)phosphonic acid and mono-2-ethylhexyl ester of 2-ethylhexylphosphorous acid, dissolved in heavy dearomatised white spirits, then the organic phase is rinsed with deionised water until anions are rinsed out and alkali metal ions in the aqueous phase, a then nickel is extracted from the organic phase with a nitric acid solution with a concentration of from 20 to 35%, wherein this results in a nickel nitrate solution with a concentration of about 14 % and a contamination level with other metal salts below 0.01%.

The resulting method facilitates the production of highly pure nickel nitrate from various sources that currently constitute industrial waste with a high nickel content. In particular, these may be: solid or liquid galvanic wastes, nickel sulphate from copper production, expired solutions of nickel salts in solid and liquid form, all manner of solid nickel waste (cakes, slag) from various branches of industry or nickel alloy scrap. In the case of solid waste, it is desirable to initially process them to obtain initial solutions containing nickel sulphate or chloride. These may be obtained using any known simple methods, such as elution with sulphuric or hydrochloric acid solutions.

Example 1.

Nickel solutions with a nickel content from 1 to 10 %, by mass and containing sulphate and/or chlorides are filtered following heating with activated carbon.

The four-stage extraction cascade is loaded with a filtered solution of nickel and a liquid cationite solution in heavy dearomatised white spirits. The ratio of nickel solution to cationite solution varies in the range from 0.25 to 2.5.

During the extraction the emulsion pH is controlled and corrected if needed using alkali solutions to 3.5 to 4.5.

The extraction process is conducted at a temperature of 30 to 50°C.

After separating the streams (aqueous phase/organic phase) the post-extraction nickel solution is centrifuged (to remove organic phase residues) and introduced into a periodic reactor in which nickel is extracted by higher aliphatic acids, selected from a group encompassing: di-2-ethylhexylphosphoric acid, di(2,4,4-trimethylpentyl)phosphonic acid and mono-2-ethylhexyl ester 2-ethylhexylphosphorous acid, dissolved in heavy dearomatised white spirits. Preferably use is made of a mono-2-ethylhexyl ester 2-ethylhexylphosphorous acid solution in heavy dearomatised white spirits.

This process is meant to separate anions from the nickel (in particular: sulphates, chlorides phosphates and other anions).

After the phase separation (aqueous phase/organic phase) - the organic phase is rinsed with deionised water, until anions and alkali metal ions are rinsed out.

After this process, nickel is extracted from the organic phase with a nitric acid solution with a concentration of 20- 35 %.

This results in a nickel nitrate solution with a concentration of 10-11 % per 100% nickel. To obtain more concentrated solutions or crystals of nickel (II) nitrate from highly purified solutions obtained according to the present invention, one may use common knowledge means (i.e. encompassing the following sequence of stages: heating - filtration - concentration - crystallization - centrifugation).

Example 2. Comparative examples

In general, a method according to the present invention encompasses two extraction stages:

1) extraction of contamination from a nickel solution - removal of such contaminants as iron, zinc, copper, manganese etc.

2) extraction of nickel into an organic phase, encompassing the simultaneous removal of alkali metals such as sodium and potassium, and undesirable anions, in particular,: sulphate, chlorides, nitrate, phosphates, citrates; derivatives of amidosulphonic acid, boric acid, tartaric acid and possibly other modifiers and surfactants used in industry.

The method according to the present invention is the effect of multi-stage experimentation, meant to design optimal parameters for the process that are of particular significance for industrial processes. In particular, we determined the composition of solutions for extraction in the range from 5 to 15 % of extract content in the organic phase; We selected the optimal organic solvent and evaluated various extracting agents. We determined the final pH of the process and a method of reaching it, optimised the process temperature according to the extraction rate and safety (the higher the temperature, the faster the extraction but with increasing risk of fire and/or explosion). We optimised the number of extraction stages depending on the end product requirements, and we determined the optimal extraction time for each extraction stage.

The resulting process according to the present invention, which is a product of the above criteria, was completely non-obvious to the specialist. Below, we describe the results of tests of selected key parameters for the process designed. Solvent choice

Solvent optimization consisted of selecting an industrial solvent so as to meet several criteria

- Extractant solubility is good, in the range 5-20% [V/V]

- Solvent density - optimally below 0.8 g/cm3

- Ignition temperature is above 80 °C

- Appropriate solvent/extractant viscosity after the extraction

- Appropriate phase separation time in an aqueous solution/organic phase system

- Extractant/solvent mixture ignition temperature above 80 °C

The experiments designed to identify the optimal solvent were performed using the following scheme. We prepared a solution of initially selected industrial extractants (P 507, Cyanex 272 and DEHPA) with a concentration of 5% (v/v), 10% (v/v) and 15% (v/v).

DEHPA constituted di-2-ethylhexylphosphoric acid (CAS No 298-07-7), Cyanex 272 to di(2,4,4-trimethylpentyl)phosphonic acid (CAS No 83411-71-6), a P 507 to mono-2- ethylhexyl ester 2-ethylhexylphosphorous acid (CAS No 3658-48-8).

All of the extractants dissolved completely. Such solutions were mixed in a mixer for 5 minutes with deionised water, acidified with nitric acid to pH 4 +/-0.2 at a ratio of W/O 1 : 1 and left to separate. All of the mixtures possessed a satisfying separation time below 60 minutes. We observed that for lower solution concentrations these times were lower. The experiments were performed at a temperature of 20 °C. The results are shown in the table below.

* solvent: B-white spirits; Ex-Exxsol D80 (heavy dearomatised white spirits, C11-C14 hydrocarbon mixture, CAS Nr: 64742-47-8) Next we determined that the optimal temperature for the selected extractants is in the range 40-50°C. The increased temperature results in a shortened time and improved separation of the aqueous and organic phases.

Based on the results obtained, for subsequent industrial work we selected Exxol D80 due to its higher ignition temperature (for white spirits > 27 °C and for Exxol D80 > 70 °C). Since the process can be conducted at a temperature of up to 50 °C, for safety reasons it becomes necessary to use a solvent with a higher ignition temperature.

As another selection criteria we also took into account extractant losses due to its solubility in of aqueous solutions. For selected solvents we determined that losses for P 504 stem from solubility in the aqueous phase and are at a level of 45 g/m3 of solution, which at the planned rate of production yields 50 kg/year, whereas for Cyanex 272 this is 35 g/m3 of solution, which at the planned rate of production yields 40 kg/year, and the losses for DEHPA are 100 g/m3 of solution, which at the planned rate of production yields 100 kg/year.

Experiments designed to select the optimal extractant based on nickel losses depending on pH of solutions were conducted as follows:

An extractor was loaded with 250 cm3 of nickel solution containing 5.9 % nickel at pH 4,0 and heated to 60 °C and then we added 250 cm3 of extractant solution with a content of 10 % [V/V]. During mixing, the solution pH dropped to 1.5 to 2.5. We supplemented the solution portion-wise with 30 % sodium hydroxide until the pH was stable at a level of 3 +/-0.1 and after this we continued to mix the mixture for 5 minutes while controlling the pH. After this time, the mixture was settled for 60 minutes to separate. The nickel solution after separation was separated again as described above. The nickel solution was extracted thrice. We repeated the tests with an end pH of 4 and 5.

We obtained the following results:

An extractor was loaded with 250 cm3 of nickel solution containing 5.9 % nickel at pH 4,0 and heated to 60 °C and then we added 250 cm3 of extractant solution with a content of 10 % [V/V]. During mixing, the solution pH dropped to 1.5 to 2.5. We supplemented the solution portion-wise with 30 % sodium hydroxide until the pH was stable at a level of 4 +/-0.1 and after this we continued to mix the mixture for 5 minutes while controlling the pH. After this time, the mixture was settled for 60 minutes to separate. The nickel solution after separation was separated again as described above. The nickel solution was extracted thrice.

We obtained the following degrees of separation:

Due to the results above, for further research we selected P 507 due to its lower price and results closely matching those of the more expensive Cyanex 272 .

For this extractant we performed tests of the whole process:

1/ We prepared solution nickel

21 We prepared three extraction solutions of extractant, 10 % P 507

3/ We prepared the extraction of nickel from the aqueous phase into the organic phase using a solution of this aliphatic acid in Exxsol

4/ The organic phase after re-extracting the nickel was washed thrice in deionised water 5/ Using 30 % nitric acid we extracted the nickel to the aqueous phase

The table below shows the results. For the comparative process, we used real solutions from industrial waste and obtained products of the following compositions after the completion of the process: Initial Solution Product solution

Solution Solution Degree of Percent contaminant

Working Final solution

recalculated to recalculated separation removal solution (product)

14% to 14% [%]

Nickel 5,9 % 14,0 % 8,8 % 14,0

content

Sulphate 3,0 % 7, 11 % 0,0013 % 0,0021 "A 3 386 99,9 content

Chloride 0,4 % 0,948 % 0,007 % 0,01 "A 95 98,9 content

Lead content 0,001 % 0,0024 % 0,00002 % 0,00003 °/ 80 98,8

Cadmium 0,001 % 0,0024 % 0,00002 % 0,00003 °A 80 98,8 content

Copper 0,075 % 0, 1778 % 0,0006 % 0,00095 °/ 187 99,5 content

Iron content 0,08 % 0, 190 % 0,0006 % 0,00095 °A 200 99,5

Content 0,017 % 0,0403 % 0,0007 % 0,0011 °/ 37 97,3 magnesium

Cobalt 0, 161 % 0,3816 % 0,0003 % 0,00048 °/ 795 99,9 content

Zinc content 0,0989 % 0,2344 % 0,0001 % 0,00016 °A 1465 99,9

Sodium 1 , 175 % 2,7848 % 0,0015 % 0,00239 °/ 1165 99,9 content

Calcium 0,024 % 0,0569 % 0,0077 % 0,0122 °A 5 78,6 content