KR20070035789A - The method of precipitation and stripping for cobalt - Google Patents

Abstract

The present invention relates to a method of precipitating-separating cobalt oxalate using a solvent-extracted cobalt oxalic acid as a stripping solution.

Precipitation-Scavenging Method of Cobalt of the Invention Mixing the cobalt organic phase and the oxalic acid solution at a constant ratio; Stirring for a predetermined time; Separating the phases using a centrifuge; And there is a technical feature in that the step consists of collecting and filtering the water phase.

Therefore, the precipitation-removal method of the solvent-extracted cobalt of the present invention has the effect of reducing the manufacturing cost by simplifying the existing two processes of stripping and precipitation in a single process.

Cobalt, oxalic acid, solvent extraction, precipitation, stripping

Description

The method of precipitation and stripping for Cobalt}

1 is the precipitation rate of cobalt over time according to an embodiment of the present invention,

2 is a removal rate of cobalt with respect to pH according to another embodiment of the present invention,

3 is a percentage of cobalt precipitated in stripped cobalt according to the change in equilibrium pH according to another embodiment of the present invention,

4 is a cobalt leaching rate according to the pH effect when oxalic acid is added according to another embodiment of the present invention,

5 is XRD data of a precipitate according to the present invention,

6 is a precipitation rate for the temperature according to another embodiment of the present invention.

The present invention relates to a method of sedimentation-removal of cobalt, and more particularly, to recover cobalt extracted in an oil phase using cobalt oxalate (CoC ₂ O ₄₎ precipitate, using oxalic acid as a stripping solution to precipitate-cobalt solution. It is about how to remove.

Cobalt is present in the crust by about 0.002%, most of which is obtained as a by-product from ores such as copper and nickel, most of which are concentrated in certain countries such as Zambia and Canada.

In particular, since they are not only essential metals for the manufacture of chemicals such as heat and corrosion resistant chemicals and catalysts, they are also produced as strategic metals in most countries, and cobalt supply in the world does not meet demand.

In order to secure new cobalt resources, development of manganese nodules, such as buried in the deep sea, is being promoted, but due to the high cost of mining, it takes a long time to commercialize. Therefore, research on cobalt recovery from cobalt-containing metal waste resources has been actively conducted in recent years. Cobalt used as a provider in waste cemented carbide is an important recovery source, and cobalt recovery from waste catalysts, waste batteries, waste alloys, and the like is also receiving great attention.

Conventionally, the oxidative precipitation method has been mainly used for the separation and premise of cobalt, but the solvent extraction method is widely used in recent years because it is difficult to completely separate from other metals. Particularly, in the case of raw materials containing nickel, it is difficult to separate them by precipitation method or electrolytic method, and most of the solvent extraction method is used to separate nickel and cobalt. The general process of cobalt recovery by this method is to extract the cobalt and to remove the cobalt in an aqueous solution using a strong acid, and then electrolytically collected to recover or crystallize the metal cobalt to obtain a cobalt salt.

However, in the case of electrolytic extraction, a neutralizing agent is required to adjust the pH of the electrolyte, and in the case of cobalt salt production, the cobalt concentration of the stripping solution is low, which requires a lot of energy for crystallization.

Accordingly, the present invention is to solve the above-mentioned disadvantages and problems of the prior art, to provide a cobalt precipitation-removal method that can obtain a high concentration of cobalt precipitate without additional energy consumption for the addition of a neutralizing agent or crystallization. There is this.

The object of the present invention is to mix the cobalt organic phase and oxalic acid solution in a predetermined ratio; Stirring for a predetermined time; Separating the phases using a centrifuge; And collecting and filtering the aqueous phase.

Solvent extractant used in the present invention was used 0.1 ~ 0.2M for cobalt extraction as bis (2,4,4-trimethylpentyl) phosphinic acid. Kerosene, a reagent grade, was used as a diluent. The aqueous phase was dissolved in distilled water with reagent grade CoSO ₄ · 7H ₂ O and used at a Co concentration of 1 to 3.0 g / L. The equilibrium pH was adjusted to 1.5 to 2.0 to increase the extraction rate. Under these conditions, all cobalt in the water phase was extracted into the organic phase.

Precipitation-removal of cobalt was performed by using an oxalic acid solution as a stripping solution to recover CoC ₂ O ₄ in CoC _n O _{n +2} series as a precipitate from 1 to 3 g / l of cobalt extracted as an organic phase.

First, the organic phase and the oxalic acid solution were mixed at a constant ratio, and then stirred at a constant time at 200 to 400 rpm using a stirrer, and then solid / liquid separation was performed using a centrifuge. After phase separation, the aqueous phase was collected, filtered, and the pH was measured. The cobalt content in the aqueous phase and the precipitate was measured by EDTA titration, and their stripping rate and precipitation rate were obtained as follows. Conditions for the reaction were 5 ~ 15% NaOH and 35 ~ 55% H ₂ SO ₄ to adjust the temperature 25 ℃, O / A 1.0 and pH. And all the process except the reaction was done at 25 ℃.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that it can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

Example 1

Precipitation of cobalt over time was carried out under the same process sequence and conditions as described above. The result shows the precipitation rate of cobalt in the state of reacting 2 equivalents of oxalic acid with an O / A ratio of 1 in the organic phase loaded with cobalt as shown in FIG. 1. Initially, the cobalt precipitation rate (precipitation%) increases with time, but the precipitation rate is constant when the reaction time is 10 minutes or more. This was enough time to react for 5 minutes when only stripped, but it took time to settle with cobalt oxalate.

Example 2

The cobalt was stripped according to the pH of the oxalic acid solution as the stripping solution under the same process sequence and conditions as described above.

The stripping-precipitation of cobalt from the organic phase occurs by stripping reaction (Equation 1) and precipitation of cobalt ions stripped with oxalic acid to cobalt oxalate (Equation 2).

2RH (org) + Co + 2 (aq) = R2Co (org) + 2H + (aq) Equation (1)

R2Co (org) + H2C2O4 (aq) = 2RH (org) + CoC2O4 (aq) Equation (2)

As can be seen in equations (1) and (2), as the pH of the stripping solution is lower, the stripping rate of cobalt increases and the precipitation rate to CoC ₂ O ₄ decreases.

FIG. 2 shows the stripping and precipitation of cobalt under the influence of equilibrium pH (Eq.pH) under conditions of O / A ratio 1, using two equivalents of oxalic acid. 1eq, 2eq and 3eq mean 1 equivalent, 2 equivalents and 3 equivalents of oxalic acid relative to cobalt, respectively. During the reaction, 100% cobalt is removed until the equilibrium pH is about 1.5, but when the pH is increased above, the removal rate is gradually lowered, and when the equilibrium pH is 4.0, the removal rate is only about 80%. On the other hand, cobalt hardly precipitates at a pH of 0.5, but if it is higher than that, the precipitation rate rapidly increases, reaches a maximum value near pH 1.5, and starts to decrease again. The precipitation rate is about 65%. The cobalt sedimentation rate decreases above pH 1.5 because the cobalt stripping rate decreases at high pH.

Figure 3 shows the percentage of cobalt precipitated in stripped cobalt with changes in equilibrium pH. Up to about 2.0, the amount of cobalt precipitated in the stripping solution increased rapidly with increasing pH, but more slowly than that. This is in good agreement with FIG. 4 which shows the precipitation according to the equilibrium pH (Equilibrium pH) effect upon addition of oxalic acid in an aqueous solution containing cobalt.

Example 3

As described above, cobalt was precipitated and stripped according to the amount of oxalic acid added under the same process sequence and conditions.

When the addition amount of oxalic acid is 2 equivalents to 1 equivalent of cobalt, the precipitation rate of cobalt increases and there is no big difference thereafter. Therefore, the amount of oxalic acid added is effective in the amount of 1 to 2 equivalents of cobalt. On the other hand, the equivalent ratio of oxalic acid added does not affect the removal rate of cobalt, because the removal rate is determined by the pH of the stripping solution. Experimental results show that at the equilibrium pH 1.5 of the stripping solution, 76% of cobalt precipitates when oxalic acid is added in a 2 equivalent ratio of cobalt.

5 is XRD data of a precipitate produced at this time. Comparing the position of the peak with the data value (¤) of the JCPDS card, it can be seen that the obtained precipitate is CoC ₂ O ₄ · 2H ₂ O.

Example 4

The precipitation rate of cobalt according to the ratio of organic phase and water phase (O / A) was investigated. The O / A ratio was changed to 3, 2, 1, 1/2, 1/3 at the oxalic acid addition amount 2 equivalence ratio and equilibrium pH 1.5.

Table 1 shows the precipitation rate according to the ratio (O / A) of the valuable phase and the water phase in the stoichiometric non-cobalt precipitation of oxalic acid and cobalt.

The lower the O / A, the lower the cobalt precipitation rate is due to the lower concentration of oxalic acid in the water phase.

 O / A  3  2  One  1/2  1/3  oxalic acid conc. (g / L)  12.84  5.56  4.28  2.14  1.43  Co precipitation (%)  95.1  90.7  79.7  2.14  1.43

Table 2 shows the cobalt precipitation rate according to the amount of oxalic acid. To confirm this, 2 equivalents of oxalic acid was added to the cobalt solution with varying concentrations.

It can be seen that the lower the concentration of the added oxalic acid, the lower the precipitation rate of cobalt, which is attributed to the concentration of oxalic acid O / A and cobalt.

 oxalic acid conc. (g / L)  17.2  8.6  4.3  2.9  oxalic acid soln. (g / L)  10  20  40  60  Co precipitation (%)  91.6  76.5  73.7  66.8

Example 5

As described above, cobalt was precipitated according to the reaction temperature under the same process sequence and conditions, and the results are shown in FIG. 6 to show the precipitation rate (precipitation%) of cobalt according to temp.

In order to investigate the stripping rate and precipitation rate of cobalt at the reaction temperature, 2 equivalents of oxalic acid were stripped and precipitated at an O / A ratio of 1.0. The precipitation rates of cobalt increased to 78.2%, 83.0%, 85.9% and 86.4%, respectively, at temperatures of 25 ° C, 40 ° C, 55 ° C and 70 ° C. This is because the stripping rate increases with higher temperature.

Therefore, the cobalt precipitation-removal method of the present invention simplifies the process of removing the solvent-coated cobalt and preparing the precipitate in a single process, thereby reducing the cost.

Claims (13)

In the method of precipitating and removing cobalt, Mixing the cobalt and oxalic acid solution; Stirring; Separating the phases using a centrifuge; And Collecting and filtering the aqueous phase Cobalt precipitation-removal method using a solvent extraction method comprising a. The method of claim 1, The cobalt is extracted into the organic phase and the weight is 1 to 3g / ℓ cobalt precipitation-stripping method using a solvent extraction method. The method of claim 2, The organic phase is a cobalt precipitation-removal method using a solvent extraction method of bis (2,4,4-trimethylpentyl) phosphicin acid as a solvent extractant. The method of claim 2, Cobalt precipitation-removal method using a solvent extraction method of the equilibrium pH is 1.5 to 2.0 when extracted into the organic phase. The method of claim 2, Cobalt precipitation-removal method using a solvent extraction method of the molar concentration of the cobalt is 0.1 to 0.3M. The method of claim 5, Cobalt precipitation-removal method using a solvent extraction method using kerosene as a diluent to adjust the molar concentration of the cobalt. The method of claim 1, The amount of oxalic acid is a cobalt precipitation-removal method using a solvent extraction method of 1 to 2 times the equivalent of cobalt. The method of claim 1, The stirring is cobalt precipitation-removal method using a solvent extraction method of stirring at a rotational speed of 200 to 400rpm using a stirrer. The method of claim 1, The aqueous phase is a cobalt precipitation-removal method using a solvent extraction method using CoSO ₄ · 7H ₂ O dissolved in distilled water as a reagent grade. The method of claim 9, The water phase is cobalt precipitation- stripping method using a solvent extraction method using a concentration of 1 to 3.0 g / l Co. The method of claim 1, Cobalt precipitation-removal method using a solvent extraction method of further mixing NaOH and H ₂ SO ₄ for pH control of the stirring step. The method of claim 11, The concentration of NaOH is 5 to 15%, the concentration of H ₂ SO ₄ is 35 to 55% cobalt precipitation- stripping method using a solvent extraction method. The method of claim 1, The material precipitated through the above steps is CoC _n H _{n + 2} based cobalt precipitation-removal method using a solvent extraction method of CoC ₂ H ₄ .

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