CN113073208B

CN113073208B - Pretreatment method of extracting agent for cobalt-nickel separation and corresponding extraction method

Info

Publication number: CN113073208B
Application number: CN202110333038.0A
Authority: CN
Inventors: 赵云斌; 徐坤坤
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2021-03-29
Filing date: 2021-03-29
Publication date: 2022-06-10
Anticipated expiration: 2041-03-29
Also published as: CN113073208A

Abstract

The invention discloses a pretreatment method of an extracting agent for separating cobalt and nickel and a corresponding extraction method. Wherein the pretreatment method comprises the following steps: the acidic extractant is pretreated by a weak acid strong base salt pretreating agent. The invention can effectively simplify the extraction process, reduce the consumption of acid and alkali in the extraction process and the discharge of secondary pollutants such as salt, organic matters and the like, and has higher extraction separation efficiency and cyclic utilization rate.

Description

Pretreatment method of extracting agent for cobalt-nickel separation and corresponding extraction method

Technical Field

The invention relates to the technical field of extracting agents for separating cobalt and nickel.

Background

Cobalt is a very important nonferrous metal and plays an important role in manufacturing materials such as alloys, lithium ion batteries and the like. The recycling of the ore and the waste resources is a main obtaining way of cobalt, wherein in the aspect of ore obtaining, because the chemical properties of cobalt and nickel are very similar, the phenomena of symbiosis and association of the cobalt and the nickel often exist in an ore deposit, and therefore the cobalt and the nickel need to be separated; in the aspect of recycling waste resources, various cobalt-containing solid wastes often contain nickel, such as waste lithium ion battery anode materials, waste catalysts, nickel smelting converter slag and the like, so that the cobalt and the nickel are more required to be separated, namely the cobalt with high purity is obtained, and the efficient separation of the cobalt and the nickel is often the key of the technology.

The solvent extraction method is a common method for separating cobalt and nickel due to the advantages of high selectivity, high recovery rate, simple process and the like, and the separation principle is as follows: the characteristic that the capacity of the extractant for combining cobalt is stronger than that for combining nickel is utilized, under the condition of controlling a certain acidity, the extractant is used for extracting the water phase containing the mixed ions of cobalt and nickel, the cobalt and the extractant are combined to enter an organic phase, and the nickel still exists in the water phase, so that the separation of the cobalt and the nickel is realized. Acidic organophosphorus extractants P507 and Cyanex272 commonly used for separating cobalt and nickel, pK in 75% ethanol water solution_aThe values are respectively 4.51 and 6.02, the acidity and the extraction capacity of P507 are stronger than those of Cyanex272, but the cobalt extracted by the Cyanex272 has better selectivity. The extraction capacity of the acidic extractant is closely related to the pH value of the water phase, and the higher the pH value of the water phase is, the stronger the extraction capacity of the extractant is, but the poorer the separation effect on metals is.

On the other hand, after the extraction of the metal with the acidic extractant takes place in the extraction reaction (1) as described above, H is liberated⁺The pH value of the feed liquid is reduced, and the extraction rate is obviously reduced. In order to overcome the problem, the prior art generally adopts a treatment means that the extraction agent is saponified by sodium hydroxide to generate saponification reaction (2), so that part of the extraction agent is firstly converted into sodium salt, and then the extraction agent after saponification treatment is extractedWhen the metal ions are taken, an extraction reaction (3) takes place, which reaction is free of H⁺The pH value of the water phase is controlled to be reduced during extraction, and higher extraction rate can be obtained.

However, in this technical solution, when the saponified extractant is used to extract cobalt, the pH of the aqueous phase of the system will rise significantly, and even hydrolysis of metal ions and emulsification of the system will occur, because the partially saponified extractant binds to H in the aqueous phase⁺Enters the organic phase and undergoes reaction (4):

when extracting cobalt, if the pH value of the water phase rises, the nickel is seriously co-extracted, and the separation effect of cobalt and nickel is further affected. In order to avoid the co-extraction phenomenon, a certain amount of acid is required to be added in the reaction to keep the pH value of the water phase relatively stable.

It can be seen that the method for separating cobalt from nickel by using saponified acidic extractant has the following disadvantages: (1) the saponification of the extractant requires the consumption of a large amount of sodium hydroxide; (2) in the extraction process, acid is needed to be added to maintain the pH value of a water phase, the consumption of the acid is additionally increased, and high-salinity wastewater is generated; (3) the amount of acid is not easy to control.

In part of the prior art, a new scheme is proposed to improve the above problems, such as a method for adjusting the acidity of an aqueous phase by using a weak acid buffer and separating metal ions by using an acidic extractant, disclosed in patent CN201510379361, "a method for extracting and separating trivalent lanthanide series ions and trivalent actinide series ions"; CN201610837172 discloses a method for purifying and enriching vanadium from stone coal pickle liquor, which comprises adding weak acid salt into water phase to adjust water phase acidity, and extracting vanadium with acidic extractant. In the method, the extractant does not need saponification, the pH value of the water phase is controlled by a weak acid buffer system in the extraction process, the extraction process is simplified, the consumption of acid and alkali is reduced, but the residual water phase contains organic matters and is difficult to recycle, so that a large amount of high-COD extraction wastewater can be generated.

Disclosure of Invention

The invention aims to provide a novel extractant pretreatment method and a corresponding extraction method, which can effectively simplify the extraction process, reduce the consumption of acid and alkali in the extraction process and the discharge of secondary pollutants such as salt, organic matters and the like, and have higher extraction separation efficiency and cyclic utilization rate.

The invention firstly discloses the following technical scheme:

a pretreatment method of an extracting agent for separating cobalt and nickel comprises the following steps: and (2) pretreating the cobalt-nickel separation acid extractant by using a weak acid strong base salt serving as a pretreatment agent to obtain the pretreated extractant, wherein the weak acid strong base salt is a water-soluble salt which does not have a precipitation reaction with cobalt and nickel, and the acidity coefficient pKa of the weak acid strong base salt is 4.5-7.5.

In the above scheme, the weak acid strong base salt, such as sodium salt NaA, and the acidic extractant HR react in the solution during the pretreatment as follows:

compared with the saponification reaction (2), the alkalinity of NaA is far lower than that of NaOH, the reaction (5) is low in degree, the conversion rate of an extracting agent NaR is low, the reaction (4) can be effectively reduced when cobalt is extracted, and the cobalt and nickel separation efficiency is improved.

According to some preferred embodiments of the present invention, the weak acid and strong base salt is selected from one or more of sodium bicarbonate, sodium acetate, sodium citrate, and sodium hydrogen phthalate.

According to some preferred embodiments of the present invention, the acidic extractant is selected from 2-ethylhexyl phosphate mono-2-ethylhexyl ester (P507) and/or bis (2,4, 4-trimethylpentyl) phosphinic acid (Cyanex 272).

According to some preferred embodiments of the present invention, the pretreatment method comprises the steps of:

preparing the extracting agent into an organic solution through a diluent;

and mixing the aqueous solution of the pretreating agent with the obtained organic solution in an equal volume ratio, and then standing for phase separation to obtain an organic phase, namely the pretreated organic phase of the extracting agent.

According to some preferred embodiments of the invention, the diluent is selected from sulfonated kerosene.

According to some preferred embodiments of the invention, the concentration of the extractant in the organic solution is between 0.25 and 0.5 mol/L.

According to some preferred embodiments of the present invention, the concentration of the pretreating agent in the aqueous solution of the pretreating agent is 1.0 to 4.0 mol/L.

According to some preferred embodiments of the present invention, the aqueous pretreatment agent solution and the organic solution are mixed for 10 to 20 min.

The invention further discloses an extraction method applying any one of the pretreatment methods.

According to some preferred embodiments of the present invention, the extraction method comprises: the pH value of the dilute sulfuric acid aqueous solution of the cobalt-nickel mixed feed liquid is 4.0-6.0.

According to some preferred embodiments of the invention, the extractant organic phase is obtained by subjecting a 0.5mol/L sulfonated kerosene organic solution of Cyanex272 to the pretreatment with a 3mol/L aqueous sodium acetate pretreatment solution, and the organic phase contains 2g/L Co²⁺And 2g/L Ni²⁺The cobalt-nickel mixed material liquid is extracted, and the volume ratio of an organic phase to a water phase used for extraction is 1: 1.

In this preferred embodiment, the optimum cobalt extraction rate and cobalt-nickel separation factor can be obtained.

The invention has the following beneficial effects:

the pretreatment method provided by the invention has the advantages that weak acid radicals in the pretreatment agent are not consumed, only a small amount of NaOH needs to be supplemented, and the weak acid radicals can be recycled for infinite times, so that the consumption of alkali can be greatly reduced and the extraction cost is reduced compared with the saponification pretreatment method in the prior art.

The pretreatment method and the extraction method provided by the invention do not need to regulate and control the pH value of the feed liquid in the extraction process, the extraction process is simplified, and meanwhile, high-salinity wastewater is basically not generated.

According to the pretreatment method and the extraction method provided by the invention, the weak acid salt of the treating agent is not added into the feed liquid, so that the treating agent can be recycled, and the extraction wastewater containing organic matters is not generated.

When the cobalt-nickel mixed feed liquid is extracted by some preferred embodiments of the invention, the single extraction rate of the obtained cobalt is more than 98.8 percent and can further reach 99.26 percent, and the separation factor of the obtained cobalt and nickel is more than 177 and can further reach 321.1; and after the pretreatment agent is recycled for multiple times, the cobalt extraction rate can still be kept above 90%.

Drawings

FIG. 1 is a schematic diagram of a specific extraction process according to the present invention.

FIG. 2 is a graph showing the relationship between the concentrations of P507 and Cyanex272 and the extraction rates of cobalt and nickel in examples 2-6.

FIG. 3 is a graph showing the relationship between the concentration of P507 and Cyanex272 and the cobalt-nickel separation factor in examples 2-6.

Detailed Description

The present invention is described in detail below with reference to the following embodiments and the attached drawings, but it should be understood that the embodiments and the attached drawings are only used for the illustrative description of the present invention and do not limit the protection scope of the present invention in any way. All reasonable variations and combinations that fall within the spirit of the invention are intended to be within the scope of the invention.

Example 1

The extractant pretreatment is carried out by the following steps:

sulfonated kerosene is used as a diluent, and a plurality of groups of organic phases with the concentration of 0.25mol/L are respectively prepared from an extracting agent P507 and Cyanex 272;

mixing the sodium acetate aqueous solutions with different concentrations shown in Table 1 with the above extractant organic phase at equal volume ratio for 15min, standing for phase separation, and collecting the obtained organic phase as pretreated extractant.

In the above procedure, the pH of the aqueous sodium acetate solution was tested before and after use for pretreatment, and the results are shown in table 1:

TABLE 1 pH variation of extractant treated with sodium acetate solutions of different concentrations

It can be seen that the sodium acetate solution after treatment with the acidic extractant, was freed from H by the extractant⁺The pH dropped and P507 was more acidic than Cyanex272, with a greater drop in pH after treatment of P507.

After the sodium acetate solution is added with NaOH to neutralize generated acetic acid, the sodium acetate solution can be recycled as a pretreating agent of the extracting agent.

After the extractant is treated by the sodium acetate solution, part of the extractant is converted into a NaR form from an HR form, and the higher the concentration of the sodium acetate is, the higher the conversion rate is.

Example 2

The pretreated extractant obtained by pretreating 0.25mol/L P507 with 3mol/L sodium acetate solution in example 1 is used for extracting and separating the mixed feed liquid of cobalt and nickel, wherein the feed liquid contains 2g/L Co²⁺And 2g/L Ni²⁺The extraction conditions of the dilute sulfuric acid aqueous solution are as follows: the temperature is 25 ℃, the ratio of O/A is 1R1, the extraction equilibrium time is 15min, the extraction process is shown as the attached figure 1, the extraction result is shown as the table 2, the following table and the following examples show that the extraction rate is the extraction rate obtained by the same extraction of the mixed solution with coexisting cobalt and nickel:

TABLE 2 extraction results

It can be seen that the pH values of the raffinates obtained from different feed liquids with initial pH values in the range of 4.60-5.80 are the same, and the extraction effects are similar, which indicates that the pretreatment method of the invention is applied, the acidity of the feed liquid does not need to be strictly controlled before extraction, and no acid or alkali needs to be added in the extraction process for acidity adjustment. The primary extraction rate of the cobalt obtained by the method is more than 98%, the separation factor of the cobalt and the nickel is more than 175, the extraction efficiency is high, and the separation effect is good.

Example 3

The pretreated extractant obtained by pretreating 0.25mol/L P507 with 2mol/L sodium acetate solution in example 1 is used for extracting and separating the mixed feed liquid of cobalt and nickel, wherein the feed liquid contains 2g/L Co²⁺And 2g/L Ni²⁺The extraction conditions and procedure were the same as in example 2, except for the pH of the dilute aqueous sulfuric acid solution (2).

After extraction, the raffinate of this example was tested to have a pH of 5.01, cobalt and nickel extractions of 94.62% and 17.34%, respectively, and a separation factor of 83.76.

Example 4

The pretreated extractant obtained by pretreating 0.25mol/L P507 with 4mol/L sodium acetate solution in example 1 is used for extracting and separating the mixed feed liquid of cobalt and nickel, wherein the feed liquid contains 2g/L Co²⁺And 2g/L Ni²⁺The extraction conditions and procedure were the same as in example 2, with a dilute aqueous sulfuric acid solution having a pH of 5.40.

After extraction, the pH of the raffinate in this example was 5.83, the cobalt and nickel extraction rates were 99.26% and 51.30%, respectively, and the separation factor was 127.90.

Example 5

The pretreated extractant obtained by pretreating 0.25mol/L Cyanex272 with 3mol/L sodium acetate solution in example 1 is used for extracting and separating the mixed feed liquid of cobalt and nickel, wherein the feed liquid contains 2g/L Co²⁺And 2g/LNi²⁺The extraction conditions and procedure were the same as in example 2, with a dilute aqueous sulfuric acid solution having a pH of 5.40.

After extraction, the pH of the raffinate in this example was 4.55, the cobalt and nickel extraction rates were 58.80% and 5.05%, respectively, and the separation factor was 26.98, as determined by testing.

Example 6

Extracting and separating the cobalt and nickel mixed feed liquid by using the pretreated extractant obtained by pretreating 0.5mol/L Cyanex272 by 3mol/L sodium acetate solution in the same pretreatment process as the example 1, wherein the feed liquid contains 2g/L Co²⁺And 2g/L Ni²⁺The extraction conditions and procedure were the same as in example 2, with a dilute aqueous sulfuric acid solution having a pH of 5.40.

After extraction, the pH of the raffinate was 5.10, the cobalt and nickel extraction rates were 97.66% and 11.20%, respectively, and the separation factor was 321.1.

The results of statistical comparison of the P507 and Cyanex272 concentrations and the cobalt and nickel extraction rates in examples 2-6 are shown in fig. 2, and the results of statistical comparison of the P507 and Cyanex272 concentrations and the cobalt and nickel separation factors in examples 2-6 are shown in fig. 3. The data of the examples and the accompanying figures 2 and 3 show that the extraction rate and the separation factor are significantly affected by the type and concentration of the extractant and the concentration of the pretreatment solution.

Example 7

The extraction agent which is obtained after pretreatment and is newly prepared by repeatedly and circularly pretreating 3mol/L sodium acetate solution in example 1 and is 0.25mol/L P507 and Cyanex272 extracting agent is used for extracting and separating cobalt and nickel mixed feed liquid, namely, residual water phase after the extracting agent is treated each time is directly used as the pretreating agent for next pretreatment of the extracting agent, wherein the feed liquid is Co containing 2g/L²⁺And 2g/L Ni²⁺The extraction conditions and procedure were the same as in example 2, with a dilute aqueous sulfuric acid solution having a pH of 5.40. The cycle times of sodium acetate and the extraction effect of the extractant are shown in table 3 below:

TABLE 3 influence of the number of times of the extraction of the sodium acetate solution in the circulating treatment of the extractant on the extraction

The pH value of the water phase of the pretreating agent is reduced due to the generation of the product acetic acid, the extracting effect is slightly reduced by treating the extracting agent again, and the pretreating effect of the extracting agent can be maintained by neutralizing the acetic acid with a small amount of NaOH.

Comparative example 1

Directly extracting 2g/LCo with pH values of 4.60, 5.00, 5.40 and 5.80 by using 0.25mol/L P507 as an extracting agent without any treatment²⁺And 2g/L of Ni²⁺The conditions and procedures of the dilute aqueous sulfuric acid solution were the same as those of example 2. After extraction, the pH value of the raffinate is reduced to about 2.85, and the extraction rate of Co is about 10%.

Using 0.25mol/L Cyanex272 without any treatment as extractant to directly extract 2 g/LCo-containing solution with pH values of 4.60, 5.00, 5.40 and 5.80²⁺And 2g/L of Ni²⁺The extraction conditions of the dilute aqueous sulfuric acid solution of (3) were the same as those of example 2. After extraction, the pH value of the raffinate is reduced to 3.20, and the extraction rate of Co is improved<10％。

Comparative example 2

0.25mol/L P507 and Cyanex272 were each saponified with NaOH to a degree of saponification of 50%, and then the treated two extractants were used to saponify a mixture containing 2g/LCo at pH 4.60, 5.00, 5.40, and 5.80²⁺And 2g/L of Ni²⁺The diluted sulfuric acid aqueous solution of (2) was subjected to extraction under the same conditions and in the same manner as in example 2.

After extraction, the saponified P507 was found to be turbid and hydrolyzed; the organic phase of the solution using the saponified Cyanex272 as the extractant is seriously emulsified and difficult to separate. Therefore, when P507 or Cyanex272 having a saponification rate of 50% is used for extraction, it is necessary to control the pH of the aqueous phase by adding an acid.

The above examples are merely preferred embodiments of the present invention, and the scope of the present invention is not limited to the above examples. All technical schemes belonging to the idea of the invention belong to the protection scope of the invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention, and such modifications and embellishments should also be considered as within the scope of the invention.

Claims

1. An extraction method, characterized in that: it includes: adding the pretreated organic phase of the extracting agent into a dilute sulfuric acid aqueous solution of a cobalt-nickel mixed feed liquid, and extracting for separating cobalt and nickel at room temperature, wherein the obtaining of the pretreated extracting agent comprises the following steps: pretreating the cobalt-nickel separation acid extracting agent by using weak acid and strong base salt as a pretreatment agent; wherein, the weak acid strong alkali salt is water-soluble salt which does not have precipitation reaction with cobalt and nickel, and the acidity coefficient pKa of the salt is 4.5-7.5; the pH value of the dilute sulfuric acid aqueous solution of the cobalt-nickel mixed feed liquid is 4.0-6.0; the weak acid strong alkali salt is selected from one or more of sodium bicarbonate, sodium acetate, sodium citrate, sodium hydrogen citrate and sodium hydrogen phthalate, and the acidic extracting agent is selected from 2-ethylhexyl phosphate mono-2-ethylhexyl and/or di (2,4, 4-trimethylpentyl) phosphinic acid.

2. The extraction process according to claim 1, characterized in that: wherein the obtaining of the pretreated extractant organic phase comprises the following steps:

preparing the extracting agent into an organic solution through a diluent;

3. The extraction process according to claim 2, characterized in that: the diluent is selected from sulfonated kerosene; the concentration of the extracting agent in the organic solution is 0.25-0.5 mol/L; the concentration of the pretreating agent in the aqueous solution of the pretreating agent is 1.0-4.0 mol/L; the mixing time of the pretreatment agent aqueous solution and the organic solution is 10-20 min.

4. The extraction process according to claim 1, characterized in that: the extractant organic phase is obtained by pretreating 0.5mol/L sulfonated kerosene organic solution of extractant Cyanex272 by 3mol/L sodium acetate pretreatment agent aqueous solution, and the organic phase contains 2g/L Co relatively²⁺And 2g/L Ni²⁺The cobalt-nickel mixed feed liquid is extracted, and the extraction is carried outThe volume ratio of the organic phase to the aqueous phase was 1: 1.