RO123501B1 - Process for recovering nickel and cobalt from spent catalysts - Google Patents

Abstract

The invention relates to a process for recovery of nickel and cobalt from spent catalysts, based on a hydrometallurgical process. The process according to the invention comprises the following steps: the leaching of the exhausted catalyst solid mass with a dilute inorganic acid solution; contacting the leached solution obtained with a selective ion exchange resin to extract nickel and cobalt; washing the resin containing nickel and cobalt, and stripping it with a dilute inorganic acid solution; contacting the eluted solution containing nickel and cobalt with a selective organic solvent for the extraction of cobalt, the nickel remaining in the aqueous phase; contacting the cobalt-containing organic phase with a dilute acid solution to obtain pure cobalt aqueous solution and finally recovering nickel and cobalt from their aqueous solutions electrolytically or by precipitation.

Description

The invention relates to a process for recovering nickel and cobalt from spent catalysts.

Catalysts are considered a big business all over the world. Most industries depend on the use of catalysts, the effects being found in improving living conditions for people. A brief analysis found that in the chemical industry alone, for example, over 80% of processes use catalysts, costing tens of millions of dollars, and in the last 2-3 years, catalyst sales have increased by approximate

5 ... 10%, for each year. Overall, the global costs of producing these materials amount to hundreds of billions of dollars.

Catalysts have an enormous impact on industry processes, as they make certain processes possible, which in their absence would not take place or would take place very slowly, with low efficiency. They also increase the selectivity of processes, leading to increased profits and helping to protect the environment, by reducing the toxic agents resulting from chemical processes. The technical characteristics of the catalysts are activity, selectivity and service life. In most catalysts, the active species is a transition metal or a noble metal. Given the high costs used to obtain these metals and the fact that tons of catalytic materials are discarded annually due to reduced catalytic activity in processes and the fact that they become waste and produce negative effects on the environment, worldwide - intensified research to find solutions to recover the metal content of depleted catalysts and to reduce the degree of environmental pollution with such waste. Nickel and cobalt are such transition metals, with strong catalytic activity, being commonly used in catalysts used in many chemical processes. Being low-spread metals, naturally, their recovery and recycling is particularly important. Pure metallic nickel can be recovered by electrolysis of aqueous solutions of nickel salts, such as nickel chloride and or nickel sulphate. In order to produce pure metallic nickel, 99.8% purity, it is necessary that the impurities formed by transition metals such as copper, iron, manganese and cobalt be at extremely low levels in the electrolyte containing nickel ions. Also, other metals such as chromium, iron, aluminum and calcium can cause significant damage to the physical properties of nickel metal cathodes, making the process of electrolytic separation of nickel impractical. Thus, in commercial practice, it is usually necessary to use extremely pure nickel electrolyte. Other nickel recovery processes, for example, the reduction of nickel solution with hydrogen, in order to obtain nickel in powder form, also require the use of pure nickel solution.

Cobalt appears in association with nickel in many types of catalysts, on different supports, such as alumina, silica, coal, dolomite, etc. In these catalysts, the nickel and cobalt content varies from 0.5 to 10 ... 15%. For the recovery of cobalt from the solid mass of spent catalysts, it is necessary to separate it from nickel and other metallic impurities that come from the composition of the catalyst support material.

The method based on the hydrometallurgical process is specific to the field of extractive metallurgy, involving the use of the chemistry of aqueous solutions, for the recovery of the metal from ores, concentrates and residual or recycled materials. Hydrometallurgy comprises the following stages, which constitute individual operations:

- leaching (dissolution of the catalyst fraction containing the required chemical element);

- concentration and purification of solutions;

- metal recovery.

The successful processing of catalytic materials containing nickel and cobalt, for the recovery of these metals at high purity, includes the operations mentioned above, but also requires an effective step of separation of nickel from cobalt. Unfortunately, the similarity of the chemical properties between nickel and cobalt makes their separation very difficult.

RO 123501 Β1

A commercial process for the recovery of nickel and cobalt is described by Μ. E. 1

Chalkley and I. L. Toirac, in The acid pressure leach process for nickel and cobalt laterite.

Part I: Review of operation at Moa in Hydrometallurgy and Refining of Nickel and Cobalt, 3 edited by W. C. Cooper and I Mihaylov, Proceedings of 27th Annual Hydrometallurgical

Meeting, The Metallurgical Society of CIM, Canada, 1997, pp. 341-353. In this process, leaching with sulfuric acid under pressure is used to solubilize nickel and cobalt in the form of sulphates, while much of the iron contained in the ore precipitates as ferric oxide. Other impurities in the ore, such as copper, manganese, magnesium, calcium, chromium and aluminum, are completely or partially dissolved. Therefore, nickel and cobalt must be separated from all these impurities before the pure forms of nickel and cobalt can be recovered. The first step in this purification process includes the precipitation of 11 nickel and cobalt plus copper and zinc impurities, as a mixture of sulfides, by introducing hydrogen sulfide gas under pressure and at a slightly high temperature (around 13 of 120 ° C). This step is quite effective for separating nickel and cobalt from manganese, magnesium, calcium, chromium, aluminum and iron, because the last elements specified 15 above do not precipitate. Purified solid nickel and cobalt sulfide is separated from the solution by sedimentation and filtration. Unfortunately, the sulfide mixture must be redissolved and further purified, before the separation of nickel and cobalt, and the recovery of pure metals. Redissolution and further purification is generally accompanied by relaying and mixing of sulfide with water or aqueous solution of ammonia and ammonium sulphate and air or oxygen under pressure and in the case of leaching with water a high temperature is also required (around 21

180 ... 200 ° C). Thus, in this method, obtaining a relatively pure nickel-cobalt solution from the solid ore mass requires three successive steps of solid-liquid separation at high pressure 23, which make the process quite complex and difficult. Moreover, the process uses hydrogen sulfide gas, which is expensive and very toxic. 25

Another way is to use the selective extractants described in the patents

US 5378262 and 5447552/1995. The extractants are organic phosphinic and thiophosphinic acids, and have a high separation coefficient, ranging from 5 to> 2500 for nickel and cobalt in sulfate systems. The separation coefficient S compares the distribution of two metals between an aqueous phase 29 and an organic one, and is defined as:

S = D _a / D _b 31 where D _a and D _B are the distribution coefficients of the two metals A and B at equilibrium. The distribution coefficient is defined as: 33

D = [concentration of metal in the organic phase] / [concentration of metal in the aqueous phase]. The extraction depends on the pH of the aqueous solution. Thus nickel and cobalt can be easily separated by extracting cobalt from the aqueous solution, at a pH of about 5.5, with Cyanex 272 [bis (2, 4, 4-trimethylpentyl)] phosphinic acid. At this pH value, the extraction of nickel from the aqueous solution is negligible and the extraction of cobalt is almost complete. Unfortunately, a substantial amount of copper and manganese is also extracted at this pH value of 39. Magnesium and calcium can also cause problems in the extraction process with organic solvent, as these elements are extracted at pH values very close to that at which cobalt is extracted. Another proposed process for the extraction of nickel and cobalt from various solid ores also uses leaching with sulfuric acid under pressure, step 43 followed by extraction with an organic solvent. This process is described in U.S. Patent No. 5,759,512/1998. This process has an important disadvantage, namely that the extractant cannot be reused in the presence of iron.

RO 123501 Β1

The present invention eliminates these disadvantages in that it comprises the following steps:

a. leaching of spent catalysts, placed on a bed of rubber or asphalt covered with an impermeable material, with a 1 ... 2 M aqueous solution, diluted, of acid selected from sulfuric, nitric, hydrochloric acid or a mixture thereof, when the metals present in the catalyst dissolve and pass them into solution, in the form of ions;

b. collecting the solution resulting from step a. and storing it in a tank equipped with a stirrer, in order to prevent the deposition of the entrained solid particles and then its passage in a decanter, where, after a sedimentation time of 30 ... 40 min, the deposition of solid particles takes place;

c. passing the solution resulting from step b. through an ion exchange column with a volume velocity of 30 ... 40 ml / min, the column being filled with a cation exchange resin, selective for nickel and cobalt ions, containing , as the primary chelating group, an amine selected from bis-picolylamine, bis- (2-picolyl) amine, N-methyl-2-picolylamine, N- (2-hydroxyethyl) -2-picolyl-amine or N- (2-hydroxypropyl ) -2-picolylamine or a mixture thereof, when nickel and cobalt are retained on the cation exchange resin and the other metals remain in the solution which is either further processed for the recovery of other metals or recirculated to the primary leaching stage;

d. Recovery of nickel and cobalt ions from the cation exchange resin by washing with demineralized water, followed by stripping with a 1 ... 2 M aqueous, dilute solution of sulfuric, nitric or hydrochloric acid;

e. passing the solution eluted from step d. into an extractor, where it is brought into contact with a cobalt-selective organic solvent, preferably bis (2,4,4-trimethylpentyl) phosphinic acid, when the cobalt is extracted in the phase organic, followed by the separation of the two phases, the organic phase containing cobalt and the aqueous phase containing nickel;

f. processing of the aqueous phase containing nickel resulting from step e., for the recovery of nickel either electrolytically, when high-purity metallic nickel is obtained, or by precipitation, in the form of one of its salts, which is used as such or is decomposed , to obtain nickel oxide, which can be reduced, to obtain metallic nickel;

g. processing of the organic phase containing cobalt, by extraction with a 1 ... 2 M aqueous solution, diluted, with sulfuric, nitric or hydrochloric acid, when the cobalt passes into the aqueous phase, which is subsequently processed, either electrochemically or by precipitation, followed by decomposition and reduction .to obtain metallic cobalt, the organic phase being recirculated in the primary circuit of the organic solvent, and the aqueous phase resulting from steps f. and g. being recirculated as eluent for the ion exchange column.

The process for recovering nickel and cobalt from solid materials, in particular from used catalytic residues according to the present invention, has the following advantages:

- it is simple, uses raw materials that are easy to purchase at advantageous costs, allows nickel and cobalt to be obtained at high purity, with an efficiency of over 85%, is non-polluting for the environment, the reagents used can be reused;

- recovery and recycling of metals from solid waste contributes to the depollution of the environment and reduces the costs related to the extraction and concentration of metals from natural ores;

- the process can be applied to all solid residues containing nickel and cobalt, and can be extended to the recovery of other metals from solid residues, by the appropriate selection of ion exchange resins and solvents used in the extraction operation.

RO 123501 Β1

Another advantage of the present invention is that the direct recovery, 1 by ion exchange, of nickel and cobalt is carried out as pure solutions, separated from the solution resulting from the leaching of the solid mass of spent catalyst. 3

This technique is very effective for the recovery of ionic compounds in the form of an eluted, purified and much more concentrated solution. An advantage of ion exchangers is their ability to operate, in the sense that after the metal ions have been retained in the resin mass by exchanging it with its base ions, they can be eluted by washing the resin and captured in the solution used for washing. .

Other advantages of ion exchangers are the ease of storage of the solid resin bed and the chemical stability of the resin at high temperatures. In solvent extraction, evaporation and flammability of the organic compound may limit the usual operating temperature to less than 50 ° C. Many ion exchange resins can easily be kept at a higher temperature, up to the normal boiling point of the solutions used in the process, 13 temperature which improves the kinetics of resin separation and metal separation. The ability to operate at a higher temperature also allows immediate treatment of the processing solution, as most leaching solutions have temperatures above 50 ° C. For example, in the case of leaching with sulfuric acid or other acid, the resulting solution has a temperature close to the normal boiling point of the solution, well above 50 ° C. Thus, expensive cooling steps are not necessary and greater economic efficiency is possible by reducing energy consumption due to the elimination of the cooling step.

The process according to the invention is an economical process for the substantial recovery 21 of nickel and cobalt from the solution with which the spent catalysts were leached, a solution which was passed over ion exchange resins, which retained nickel and cobalt, which were further taken from the solid mass of the resin, by washing with an aqueous solution of mineral acids, and then, from this solution, by selective extraction with organic extractants, cobalt was extracted and the nickel remained in the aqueous solution with which the resin was eluted , without degradation of the organic solvent, which could limit its repeated use. 27 Pure nickel and cobalt solutions are sent for the recovery of these metals by electrolytic extraction or other techniques. 29

The following is a detailed embodiment of the invention in connection with the figure showing the scheme of the method based on a hydrometallurgical process for recovering nickel and cobalt from solid materials, in particular from catalytic residues. 33 in general, over the solid mass of spent catalysts 3, with a nickel and cobalt content of at least 0,5%, which is placed in a pile, on a bed, which usually consists of 35 rubber or asphalt covered with an impermeable material, is sent, through the distributor 2, the leaching solution 1, consisting of an aqueous solution, diluted with acid, sulfuric, nitric, hydrochloric 37 or a mixture of these acids, 1 molar or 2 molar, 1-2 M. This solution dissolves the metals present in the mass of the catalyst, passing them into solution in ionic form. The leached solution containing 39 metal ions of nickel, cobalt as well as metal ions, which constitute impurities such as manganese, magnesium, aluminum, calcium, iron, chromium, copper, from the catalytic support, is 41 collected in the storage 4, which is equipped with an agitator, to prevent the sedimentation of solid particles entrained during the leaching operation. From the storage tank 4, the solution is passed to the decanter 5, where the separation of the solution from any solid particles entrained takes place. The sediment in separator 5 is non-toxic and is removed on route 11. It can be reused, in particular, as a building material.

30 ... 40 min, after which the leached solution, clear, from decanter 5, is passed through 47

RO 123501 Β1 route 12, through column 6, with a volume speed of 30 ... 40 ml / min. Column 6 is equipped with cationic ion exchange resin, selective for nickel and cobalt ions, and contains bis-picolyl amine, as the primary chelating group, or bis- (2-picolyl) amine, N-methyl-2-picolylamine, N- (2-hydroxyethyl) -2-picolyl-amine and N- (2-hydroxypropyl) -2-picolylamine and their mixture.

Thus, nickel and cobalt ions are retained in the resin mass, while the residual solution, which contains impurities formed from manganese, magnesium, aluminum, calcium, iron, chromium, copper ions, etc., is removed on route 13, as residual solution, solution that can be further processed, for the recovery of metallic impurities, if they have a content that makes their economic recovery, otherwise, it is reused in the primary leaching process, being reintroduced into the circuit, through route 20. Nickel and cobalt ions are recovered from the resin mass by washing it with demineralized water and then stripping it with an aqueous solution, diluted with sulfuric, nitric or hydrochloric acid (1-2 M), for elution, from the resin mass, of retained nickel and cobalt ions. The eluted solution, charged with nickel and cobalt metal ions, is passed to the extractor 7, where it is contacted with an organic solvent, selective for the extraction of cobalt. The extractant is bis (2,4,4-trimethylpentyl) phosphinic acid, which selectively extracts cobalt ions from the aqueous solution and leaves the nickel in the acidic solution, which is a pure aqueous solution of nickel. The aqueous solution of pure nickel is passed on to the nickel recovery unit 9, which is finally collected in point 10. The unit 9 may be an electrolytic cell, when the aim is to obtain high purity nickel, or a recovery unit for nickel. nickel, by precipitating, in the form of salt, the acid used in leaching. The resulting nickel salt can be used as such in other chemical applications or can be decomposed to oxide and further reduced in an inert atmosphere to metallic nickel. The organic phase of the extractor 7, charged with cobalt ions, is passed to the extractor 8, for a new extraction of cobalt, this time from the organic phase to the aqueous phase. In the extractor 8, the contact of the organic phase containing cobalt takes place with a solution of dilute sulfuric, nitric or hydrochloric acid (1-2M) to obtain the aqueous solution of pure cobalt. The organic phase, free of cobalt ions, is reused by reintroducing it on path 18 into the primary circuit of the organic solvent 15. The aqueous phase charged with cobalt ions in the extractor 8 is sent, via path 17, to the recovery unit 9 and follows the same recovery procedure described for nickel. The aqueous solution, free of nickel or cobalt ions, from the separation unit 9, is reintroduced into the process, as an elution solution, in the ion exchange column. It reaches the primary circuit of the elution solution 14 via route 19. The process for recovering nickel and cobalt from solid materials, in particular from used catalytic residues, according to the present invention is simple, using raw materials that are easy to procure at advantageous costs, allows to obtain nickel and cobalt at high purity, with efficiency over 85%, is non-polluting for the environment, the reagents used can be reused. Also, the recovery and recycling of metals from solid waste contributes to the depollution of the environment and reduces the costs related to the extraction and concentration of metals from natural ores. This method can be applied to all solid residues containing nickel and cobalt, and can be extended to the recovery of other metals from solid residues, by the appropriate selection of ion exchange resins and solvents used in the extraction operation.

Claims (1)

Claim 1 Process for the recovery of nickel and cobalt from spent catalysts by leaching 3 masses of spent catalyst, followed by processing the solution containing nickel and cobalt ions, characterized in that it comprises the following steps: a. leaching of spent catalysts, placed on a bed of rubber or asphalt covered with an impermeable material, with a 1 ... 2 M aqueous solution, diluted, of acid selected 7 from sulfuric, nitric, hydrochloric acid or a mixture thereof , when the metals present in the catalyst dissolve and pass them into solution, in the form of ions; 9 b. collecting the solution resulting from step a. and storing it in a tank equipped with a stirrer, in order to prevent the deposition of entrained solid particles, and then 11 passing it in a decanter where, after a sedimentation time of 30 ... 40 min, solid particles are deposited; 13 c. passing the solution resulting from step b. through an ion exchange column, with a volume velocity of 30 ... 40 ml / min, the column being filled with a cation exchange resin, selective for nickel and cobalt ions, containing, as the primary chelating group, an amine selected from bis-picolylamine, bis- (2-picolyl) amine, N-methyl-2-picolylamine, N- (2-17-hydroxyethyl) -2-picolyl-amine or N - (2-hydroxypropyl) -2-picolylamine or a mixture thereof, where nickel and cobalt are retained on the cation exchange resin and the other metals 19 remain in the solution which is either further processed for the recovery of other metals or recycled to primary leaching stage; 21 d. recovery of nickel and cobalt ions from the cation exchange resin by washing with demineralized water, followed by stripping with a 1 ... 2 M aqueous, dilute solution of 23 sulfuric, nitric or hydrochloric acid; e. passing the solution eluted from step d. in an extractor, where it is brought into contact with an organic solvent, selective for cobalt, preferably bis (2,4,4-trimethylpentyl) phosphinic acid, when the cobalt is extracted in the phase organic, followed by the separation of the two phases, the organic phase containing cobalt and the aqueous phase containing nickel; 29 f. processing the aqueous phase containing nickel, resulting from step e., for the recovery of nickel either electrolytically, when high-purity metallic nickel 31 is obtained, or by precipitation in the form of one of its salts, which is used as such, or is decomposed to obtain nickel oxide, which can be reduced to obtain metallic nickel; g. processing of the organic phase containing cobalt by extraction with a 1 ... 2 M 35 aqueous solution, diluted, of sulfuric, nitric or hydrochloric acid, when the cobalt passes into the aqueous phase, which is subsequently processed, either electrochemically or by precipitation, followed by decomposition and reduction, to obtain metallic cobalt, the organic phase being recirculated in the primary circuit of the organic solvent, and the aqueous phase, resulting from stages f. and g., being recirculated as eluent for the ion exchange column.