Method for removing uranium and recovering cobalt in low-cobalt high-impurity solution system

Abstract

A method for removing uranium and recovering cobalt in a low-cobalt high-impurity solution system comprises the following steps: adding lime milk and sodium persulfate into a solution to be subjected to uranium removal until the pH value is 3.6-4.8, and carrying out solid-liquid separation to obtain an iron-removed solution; lime milk and a dilute phosphoric acid solution are added, wherein the dilute phosphoric acid solution is dropwise added; and after the dilute phosphoric acid solution is added, continuously reacting until the pH value is 4.5-6.2, and carrying out solid-liquid separation to obtain uranium-removed slag and uranium-removed liquid after uranium removal. According to the method, efficient recovery of cobalt is achieved while cobalt and uranium are separated, the uranium removal effect in the low-cobalt and high-impurity solution reaches 98% or above, and the content of impurity uranium in the finally produced rough cobalt hydroxide product can be reduced to 70 ppm or below; uranium is highly enriched into uranium removal slag, the total amount of generated hazardous waste is small, and later-stage further harmless treatment is facilitated; the method is efficient, economical and environmentally friendly, and the comprehensive recovery level of cobalt resources can be remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cobalt hydrometallurgy, and particularly relates to a method for removing uranium and recovering cobalt from a low-cobalt high-impurity solution. BACKGROUND

[0002] Cobalt, as a core metal of new energy industry, is a key component of lithium-ion battery cathode material, high-temperature alloy and high-end catalyst. About 70% of global cobalt resources are concentrated in copper-cobalt deposits in the Democratic Republic of the Congo, and in addition to the main metal cobalt, impurity elements such as uranium, iron, manganese and aluminum are often associated. In recent years, with the upgrading of the Democratic Republic of the Congo government's export standards for cobalt products (such as the uranium content in crude cobalt hydroxide needs to be strictly limited to U < 80 ppm), the traditional hydrometallurgical process faces severe challenges in dealing with low-cobalt high-impurity solution systems: on the one hand, the competitive reaction of impurity elements is intensified at low cobalt concentration, resulting in a large loss of cobalt due to coprecipitation or adsorption during impurity removal; on the other hand, the presence of high-concentration impurities significantly weakens the uranium separation efficiency, ultimately affecting the compliance and economy of cobalt products.

[0003] With the gradual dilution of ore grade, the cobalt concentration in the solution used by most enterprises to produce crude cobalt hydroxide products is low (mostly in the range of 1-4 g / L), and the content of impurity elements (such as Fe, Al, Mn, etc.) is high, making it more difficult to separate uranium and precipitate cobalt. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the above-mentioned defects existing in the prior art, and to provide a method for removing uranium and recovering cobalt in a low-cobalt high-impurity solution system with good uranium separation effect.

[0005] The technical solution adopted by the present application to solve its technical problem is as follows: a method for removing uranium and recovering cobalt in a low-cobalt high-impurity solution system, comprising: adding lime milk and sodium persulfate to the uranium removal liquid to carry out iron removal reaction, until the pH value is 3.6-4.8, solid-liquid separation is carried out, and iron removal slag and iron removal liquid after iron removal are obtained;

[0006] Lime milk and dilute phosphoric acid solution are added to the iron removal liquid to carry out uranium removal reaction, wherein the dilute phosphoric acid solution is added by dripping; after the addition of the dilute phosphoric acid solution is completed, the reaction is continued for more than 20 minutes, the reaction end point pH value is 4.5-6.2, solid-liquid separation is carried out, and uranium removal slag and uranium removal liquid after uranium removal are obtained;

[0007] In the iron removal reaction, the reaction temperature is above 40℃, the oxidation-reduction potential is not less than 300mv, and the reaction time is more than 2h;

[0008] In the uranium removal reaction, the reaction temperature is above 40°C; the mass concentration of the dilute phosphoric acid solution is 1.2% to 3%; the volume ratio of the dilute phosphoric acid solution to the iron-removed liquid is 1:20 to 250; and the dropping rate of the dilute phosphoric acid solution at a single dropping point is below 10.0 mL / s.

[0009] Preferably, lime milk and sodium persulfate are added to the uranium removal solution until the pH value is 3.8 to 4.5.

[0010] Preferably, in the iron removal reaction, the redox potential is not less than 350 mV.

[0011] Preferably, the reaction temperature in the iron removal reaction is 50℃~70℃.

[0012] Preferably, the iron removal reaction takes 4 to 8 hours.

[0013] Preferably, the reaction temperature in the uranium removal reaction is 50°C to 70°C.

[0014] Preferably, in the uranium removal reaction, the dropping rate of the dilute phosphoric acid solution at a single dropping point is less than 8.0 mL / s.

[0015] Preferably, in the uranium removal reaction, the reaction continues for 30 min to 2 h after the dilute phosphoric acid solution is completely added.

[0016] Preferably, in the uranium removal reaction, the mass concentration of the dilute phosphoric acid solution is 1.5% to 2.5%.

[0017] Preferably, in the uranium removal reaction, the volume ratio of the dilute phosphoric acid solution to the iron-removed liquid is 1:30 to 200.

[0018] Preferably, in the uranium removal reaction, the pH value at the reaction endpoint is 5.0 to 6.0.

[0019] Preferably, the iron-removing slag is washed with detergent A to obtain washing liquid A and iron-removing slag; the detergent A contains less than 10 g / L of sulfuric acid.

[0020] Preferably, the uranium removal residue is washed with detergent B to obtain washing solution B and uranium-enriched uranium removal residue; the detergent B contains less than 10 g / L of sulfuric acid; and the pH value at the washing endpoint is 3.5 to 4.5.

[0021] More preferably, the washing solution A is used as the uranium removal solution for further processing.

[0022] More preferably, the washing solution B is used as the uranium removal solution for further processing.

[0023] Preferably, the uranium concentration of the liquid to be removed is below 50 mg / L.

[0024] Preferably, the solution to be treated contains sulfuric acid at a concentration of 3g / L or more.

[0025] More preferably, the solution to be treated contains uranium at a concentration of 1mg / L to 30mg / L.

[0026] More preferably, the solution to be treated contains cobalt at a concentration of 0.5g / L to 4g / L.

[0027] More preferably, the solution to be treated contains sulfuric acid at a concentration of 5g / L to 15g / L.

[0028] The present application has the following beneficial effects:

[0029] (1) The present application can be applied to the production of crude cobalt hydroxide from a low-cobalt high-impurity solution, and the efficient recovery of cobalt in the process is achieved simultaneously with the separation of cobalt and uranium. The removal effect of uranium in the low-cobalt high-impurity solution reaches 98% or more, and the impurity uranium content in the final crude cobalt hydroxide product can be reduced to within 70ppm, meeting the product sales requirements in the Democratic Republic of the Congo;

[0030] (2) The uranium is highly enriched in the uranium removal residue, resulting in a small amount of hazardous waste, which is convenient for further harmless treatment;

[0031] (3) The method of the present application is efficient, economical and environmentally friendly, and can significantly improve the comprehensive recovery level of cobalt resources.

[0032] In addition to the purposes, features and advantages described above, the present application has other purposes, features and advantages. The present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application, and are incorporated in and constitute a part of this specification. The illustrations are provided to explain the present application and are not intended to limit the present application. In the drawings:

[0034] Figure 1 is a process flow diagram of the method for removing uranium and recovering cobalt in the low-cobalt high-impurity solution system of Example 1 of the present application;

[0035] Figure 2 is a process flow diagram of the method for removing uranium and recovering cobalt in the low-cobalt high-impurity solution system of Example 5 of the present application. DETAILED DESCRIPTION

[0036] In order to make the purposes, schemes and beneficial techniques of the present application clearer, the present application will be further described in detail below with reference to the examples and drawings. It should be noted that the examples described in the present specification are only for the purpose of explaining the present application, and are not intended to limit the present application.

[0037] For simplicity, only some numerical ranges are explicitly recited herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with any other lower limit to form a range not explicitly recited, and likewise any upper limit can be combined with any other upper limit to form a range not explicitly recited. Furthermore, although a range is recited, it is to be understood that every point or individual number within that range is also specifically recited. Thus, each point or individual number can be combined with any other point or individual number to form a range not explicitly recited.

[0038] In the description herein, it is to be noted that, unless otherwise specified, "above", "below" are inclusive of the number, and the meaning of "multiple" in "one or more" is two or more, and the meaning of "multiple" in "one or more" is two or more.

[0039] The embodiment of the present application provides a method for removing uranium and recovering cobalt in a low-cobalt high-impurity solution system, comprising the following steps: adding lime milk and sodium persulfate to a liquid to be treated to remove iron, so that the pH value is 3.6-4.8, and solid-liquid separation is performed to obtain iron-removal slag and iron-removal liquid;

[0040] Lime milk and dilute phosphoric acid solution are added to the iron-removal liquid to remove uranium, wherein the dilute phosphoric acid solution is added dropwise; after the dilute phosphoric acid solution is completely added, the reaction is continued for more than 20 min, the pH value at the end of the reaction is 4.5-6.2, and solid-liquid separation is performed to obtain uranium-removal slag and uranium-removal liquid after uranium removal;

[0041] In the iron-removal reaction, the reaction temperature is higher than 40 DEG C, the redox potential is not less than 300 mv, and the reaction time is more than 2 h;

[0042] In the uranium-removal reaction, the reaction temperature is higher than 40 DEG C; the mass concentration of the dilute phosphoric acid solution is 1.2%-3%; the ratio of the amount of the dilute phosphoric acid solution to the iron-removal liquid is 1:20-250 in terms of volume ratio; and the dropwise adding speed of a single dropwise adding point of the dilute phosphoric acid solution is 10.0 mL / s or less. When the treatment capacity of the iron-removal liquid is large, the dilute phosphoric acid solution can be added through more than one dropwise adding point to ensure the total amount of the dilute phosphoric acid solution; and when the treatment capacity of the iron-removal liquid is very small, one dropwise adding point can be used.

[0043] The obtained uranium-removal liquid can be directly used for cobalt precipitation reaction by using active magnesium oxide to form cobalt hydroxide precipitation, and the cobalt hydroxide precipitation is washed and dried to become crude cobalt hydroxide product.

[0044] The embodiment of the present application can realize selective enrichment of cobalt and targeted removal of uranium under the condition of a low-cobalt high-impurity solution system through a two-stage pH regulation strategy, and the main reasons are as follows:

[0045] The first stage: under weak acid conditions, high valence impurities such as iron and aluminum are preferentially removed. In this stage, iron exists in the form of Fe 3+ , and by controlling the pH close to the hydrolysis precipitation point, efficient removal of iron [such as Fe(OH)3] can be achieved, while the precipitation of cobalt (Co 2+ hydrolysis pH>7.0) is inhibited; the generated iron slag has very low cobalt entrainment, greatly reducing the loss of cobalt;

[0046] The second stage: after solid-liquid separation, in the system where the iron and aluminum impurities have been greatly reduced, lime milk and phosphoric acid are added and the pH value is controlled to achieve selective precipitation of uranium; at this time, the concentration of competitive ions (such as Fe 3+ ) in the solution is significantly reduced, and the phosphate radical can react with the uranyl ion (UO22+) to form uranyl phosphate or calcium uranite [Ca(UO2)2(PO4)2·nH2O], which improves the efficiency of uranium removal and reduces the proportion of cobalt co-precipitation due to low impurity content, achieving deep purification of uranium.

[0047] The staged slagging also makes the iron slag generated in the first stage unnecessary to participate in the subsequent uranium removal reaction, greatly reducing the amount of uranium removal slag, thereby reducing the amount of phosphoric acid and the physical entrainment of cobalt. Uranium is highly enriched in the uranium removal slag, greatly reducing the amount of hazardous waste and greatly reducing the pressure of subsequent harmless treatment.

[0048] In a high-impurity system, other types of impurity ions are generally in the g / L level, while the uranium content is in the mg / L level, with a difference of several orders of magnitude. Therefore, in order to allow the phosphoric acid to accurately and fully react with the uranium in the solution, it must be added slowly, and part of the other impurity ions must be removed from the system in advance through iron removal and solid-liquid separation.

[0049] In an embodiment of the present application, lime milk and sodium persulfate are added to the uranium removal liquid to a pH value of 3.8-4.5.

[0050] In an embodiment of the present application, the redox potential in the iron removal reaction is not less than 350mv. The redox potential can be controlled by the amount of oxidizing agent sodium persulfate.

[0051] In an embodiment of the present application, the reaction temperature in the iron removal reaction is 50-70℃.

[0052] In an embodiment of the present application, the reaction time in the iron removal reaction is 4-8h.

[0053] In an embodiment of the present application, the reaction temperature in the uranium removal reaction is 50-70℃.

[0054] In the embodiment of the present application, the adding speed of the single drop point of the dilute phosphoric acid solution in the uranium removal reaction is 8.0 mL / s or less. When the treatment capacity of the iron removal solution is large, the dilute phosphoric acid solution can be added through more than one drop point to ensure the total amount of the dilute phosphoric acid. When the treatment capacity is small, the dilute phosphoric acid solution can be added through one drop point.

[0055] In the embodiment of the present application, the uranium removal reaction continues for 30 min to 2 h after the dilute phosphoric acid solution is added.

[0056] In the embodiment of the present application, the mass concentration of the dilute phosphoric acid solution in the uranium removal reaction is 1.5% to 2.5%.

[0057] In the embodiment of the present application, the volume ratio of the dilute phosphoric acid solution to the iron removal solution in the uranium removal reaction is 1:30 to 200.

[0058] In the embodiment of the present application, the amount of the lime milk in the uranium removal reaction can be determined according to the change of the pH value.

[0059] In the embodiment of the present application, the pH value at the end of the uranium removal reaction is 5.0 to 6.0.

[0060] In the embodiment of the present application, the iron removal residue is washed with a detergent A to obtain a washing solution A and an iron removal washed residue. The detergent A contains 10 g / L or less of sulfuric acid. The washing can dissolve part of the components in the iron removal residue. The above-mentioned method can be used to control the detergent and the washing process, so that the cobalt in the iron removal residue has a high dissolution rate, and the uranium has a low dissolution rate, thereby realizing the efficient recovery of cobalt.

[0061] In the embodiment of the present application, the uranium removal residue is washed with a detergent B to obtain a washing solution B and a uranium-rich uranium removal washed residue. The detergent B contains 10 g / L or less of sulfuric acid. The pH value at the end of the washing is 3.5 to 4.5. The washing can dissolve part of the components in the uranium removal residue. The uranium removal residue in the present application has a low impurity content and a high crystallinity, so that the residual cobalt can be selectively leached by mild pickling, and the uranium has a low dissolution rate due to the formation of a stable phosphate structure, thereby realizing the efficient separation of cobalt and uranium. The above-mentioned method can be used to control the detergent and the washing process, so that the cobalt in the uranium removal residue has a high dissolution rate, and the uranium has a low dissolution rate, thereby realizing the efficient recovery of cobalt.

[0062] In some embodiments of the present application, the washing solution A is used as the solution to be treated for uranium removal. Since the uranium has a low dissolution rate, the obtained washing solution A can be directly returned to the process, and the uranium in the solution to be treated for uranium removal will not be enriched.

[0063] In some embodiments of the present application, the washing solution B is used as the solution to be treated for uranium removal. Since the uranium has a low dissolution rate, the obtained washing solution B can be directly returned to the process, and the uranium in the solution to be treated for uranium removal will not be enriched.

[0064] In some embodiments of the present application, the washing time of the iron residue is 1-2 hours.

[0065] In some embodiments of the present application, the washing time of the uranium residue is 2-4 hours.

[0066] In some embodiments of the present application, the uranium concentration of the liquid to be treated is 50 mg / L or less.

[0067] In some embodiments of the present application, the liquid to be treated contains 3 g / L or more of sulfuric acid.

[0068] In some embodiments of the present application, the uranium concentration of the liquid to be treated is 1 mg / L-30 mg / L.

[0069] In some embodiments of the present application, the cobalt concentration of the liquid to be treated is 0.5 g / L-4 g / L.

[0070] In some embodiments of the present application, the liquid to be treated contains one or more than one of the following impurity elements: iron, manganese, magnesium, aluminum, copper, and calcium.

[0071] In some embodiments of the present application, the metal elements other than cobalt and uranium in the liquid to be treated include 3 g / L or less of iron, 4 g / L or less of manganese, 15 g / L or less of magnesium, 2 g / L or less of aluminum, 0.2 g / L or less of copper, and 0.2 g / L or less of calcium.

[0072] In some embodiments of the present application, the liquid to be treated contains 5 g / L-15 g / L of sulfuric acid.

[0073] The main purpose of the iron removal reaction is to oxidize Fe 2+ in the solution to Fe 3+ by an oxidizing agent, and then add a precipitant to remove most of the impurities such as iron and aluminum in the solution; lime milk is used as the precipitant, and sodium persulfate is used as the oxidizing agent; the obtained iron removal residue is separated from the system through solid-liquid separation, so as to prevent the lime milk from continuously releasing OH - around the settled residue layer, which causes the pH value to rise, and Co 2+ in the precipitated solution to be lost in large amounts.

[0074] If the pH value of the iron removal reaction is further increased, Co 2+ in the solution will also be easily co-precipitated or surface-adsorbed with impurity hydroxides (such as Fe(OH)3 and Al(OH)3) due to local over-alkalization and other factors, which causes the cobalt to be lost in large amounts with the iron removal residue; especially when the cobalt concentration of the original solution is low, the loss proportion of cobalt can be as high as 30% or more, which affects the normal production efficiency.

[0075] The deep removal of uranium relies on the phosphate precipitation method (such as uranyl phosphate precipitation), but in a high-impurity system, phosphate (PO43-) will also react with high-valence ions such as Co 2+ , Fe3 + , Al3+to form stable phosphate precipitates (such as FePO4, AlPO4), reducing the removal effect of uranium. Due to the low concentration of cobalt in the solution, secondary pH control is required, i.e., first control in a lower pH range, which can pre-precipitate most of the hydroxides of iron, aluminum and other impurities, and calcium sulfate slag formed by the neutralization of lime milk and sulfuric acid is discharged from the system. Under such low pH conditions, the proportion of cobalt precipitation is relatively low, and even if there is local over-alkalization, the pH value of the local over-alkalization will not be very high, and it is difficult to precipitate cobalt, so the iron removal reaction in this scheme requires solid-liquid separation. The reason why this part of the iron slag is discharged first is that this part of the slag phase may also contain unreacted lime, which will continue to release hydroxyl ions, causing the pH value of the lower sedimentation layer or the bottom mud layer to continuously rise during the iron slag sedimentation process, which may reach the precipitation pH of cobalt, causing a large amount of cobalt to precipitate and cause loss.

[0076] After the above iron slag is discharged from the system, a low-acid solution containing cobalt is obtained, and a small amount of lime milk is added to easily reach the pH value range for uranium removal. Even if local over-alkalization causes cobalt precipitation, the total cobalt recovery rate is still relatively high due to the small amount of slag formed, and it is also convenient for subsequent use of acid washing to recover cobalt elements, further ensuring the cobalt recovery rate of the system.

[0077] In the uranium removal process, dilute phosphoric acid solution is added to the solution, the main purpose of which is to introduce PO4 3- into the solution to promote the formation of uranyl phosphate precipitates in the solution; the purpose of adding lime milk to the solution is to introduce Ca 2+ into the solution to promote the formation of more stable calcium uranite precipitates in the solution, and to use calcium sulfate and other slag phases to carry out adsorption-precipitation coupling to remove uranium, significantly increasing the removal effect of uranium; the main influence mechanism is as follows:

[0078] (1) "Crystal nucleus induction" effect of slag phase

[0079] Firstly, the slag phase [calcium sulfate (CaSO4·nH2O)] microcrystalline particles can serve as heterogeneous nucleation sites, significantly reducing the nucleation energy barrier for uranyl phosphate precipitation. Without the addition of lime milk, it is difficult to form a calcium sulfate slag phase in the solution. The formation of uranyl phosphate precipitation depends on homogeneous nucleation, but the homogeneous nucleation rate is extremely low under low concentration (trace) uranium conditions, resulting in the inability to form visible precipitates. Secondly, the slag phase can promote crystal growth, thereby further accelerating the precipitation reaction. The adsorption of UO22+ and PO43- on the surface of calcium sulfate forms a local high-concentration region, accelerating the growth of calcium uranium mica lattices (such as Ca(UO2)2(PO4)2·nH2O).

[0080] (2) Coordination bridging effect of calcium ions

[0081] Ca in solution 2+ It can act as a bridge, Ca 2+ Can be combined with UO2 2+ and PO4 3- Formation of ternary complexes (such as Ca[UO2(PO4)]) + ), compress UO2 2+ The double electric layer weakens the stability of its hydrated shell, achieving charge neutralization, promoting phosphate coordination substitution, and lowering the activation energy of the reaction; the reaction process is as follows:

[0082]

[0083] (3) Dynamic equilibrium of competing reactions

[0084] The slag phase can continuously release trace amounts of Ca 2+ Maintaining a reasonable level of Ca in the solution 2+ A concentration that promotes uranium precipitation without causing excessive Ca. 2+ With PO4 3- Ca3(PO4)2 is generated while PO4 is consumed. 3- Without the addition of lime milk, a calcium sulfate system cannot be formed, and the Ca in the solution will be... 2+ A significant decrease in concentration may lead to PO4 3- Reduced effectiveness, excessive SO4 2- With PO4 3- Competitive coordination UO2 2+ This forms a readily soluble uranyl sulfate complex, and simultaneously, due to the addition of phosphoric acid, H+ is released. + It may cause local pH changes, reduce the buffering capacity of the solution, and inhibit precipitation;

[0085] (4) Surface adsorption-coprecipitation mechanism

[0086] Calcium sulfate in the slag phase can play a role in adsorption, and the calcium sulfate slag formed in the solution has a high specific surface area, and its surface hydroxyl group (≡Ca–OH) can capture UO2 2+ by chemical adsorption to form a surface complex:

[0087]

[0088] Synergistic precipitation of phosphoric acid: adsorbed UO2 2+ reacts with HPO4 2- in the solution to directly form a dense calcium uranite precipitate layer on the surface of calcium sulfate, thereby realizing adsorption-precipitation coupled removal.

[0089] By optimizing the impurity removal sequence and reaction conditions, high-content impurities (such as iron and aluminum) are preferentially separated, reducing their interference with subsequent cobalt recovery and uranium removal, and by precisely controlling the precipitation kinetics, the loss of cobalt due to co-precipitation is inhibited, thereby realizing cobalt-uranium separation and efficient recovery of cobalt.

[0090] Embodiments

[0091] The following examples describe the present disclosure in more detail, and are merely illustrative, as various modifications and changes can be apparent to those skilled in the art within the scope of the present disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are on a weight basis unless otherwise specified. Unless otherwise stated, all reagents used in the examples are available by routine commercial means or are synthesized according to routine methods and used as received without further purification. Unless otherwise stated, all instruments used in the examples are available by routine commercial means.

[0092] Example 1

[0093] The uranium removal liquid used in the method for removing uranium and recovering cobalt in the low-cobalt high-impurity solution system of this embodiment is a low-cobalt high-impurity solution used by a copper-cobalt hydrometallurgy enterprise in the Democratic Republic of the Congo to produce crude cobalt hydroxide products. The key components of the uranium removal liquid are shown in Table 1.

[0094] Table 1: Main component content analysis results of the uranium removal liquid

[0095] Co element U element Fe element Al element Mg element Mn element sulfuric acid content 1.69 g / L 16.86 mg / L 1.70 g / L 0.73 g / L 11.84 g / L 0.55 g / L 7.0 g / L

[0096] The process flow of this embodiment is shown in Figure 1 . The specific process of this embodiment is as follows:

[0097] Lime milk and sodium persulfate are added to the uranium removal liquid for iron removal reaction, the reaction temperature is controlled at 50°C, the reaction endpoint pH value is 4.0, the reaction time is 6h, and the oxidation-reduction potential is not less than 350mv; after the reaction, solid-liquid separation is performed to obtain iron removal slag and iron removal liquid;

[0098] The uranium removal reaction is carried out by adding lime milk and dilute phosphoric acid solution into the solution after iron removal, wherein the dilute phosphoric acid solution is added slowly and uniformly, the reaction temperature is controlled at 50°C, the pH value at the end of reaction is 5.0, the mass concentration of the dilute phosphoric acid solution is 1.5%, the adding amount is 30:1 (volume ratio) of the solution after iron removal to the dilute phosphoric acid solution, the dilute phosphoric acid solution is added by single-point dripping with a speed of 0.25 mL / s and a time of 60 min, and the reaction is continued for 30 min after the addition of the dilute phosphoric acid solution; and then the solid-liquid separation is carried out to obtain the uranium removal residue and the solution after uranium removal.

[0099] The cobalt removal reaction is carried out by directly adding active magnesium oxide into the obtained solution after uranium removal to form cobalt hydroxide precipitate, which is washed and dried to become crude cobalt hydroxide product.

[0100] The obtained iron removal residue, uranium removal residue and crude cobalt hydroxide product in this example are detected, and the results show that the uranium content in the iron removal residue is 87 ppm, the cobalt content is 0.28%, the uranium content in the uranium removal residue is 2938 ppm, the cobalt content is 5.98%, the uranium removal residue accounts for 7.87% of the total amount of the iron removal residue and the uranium removal residue, and the uranium content in the crude cobalt hydroxide product is 68 ppm.

[0101] Example 2

[0102] The method for removing uranium and recovering cobalt in the low-cobalt high-impurity solution system in this example and the raw materials are basically the same as those in Example 1, except that the reaction temperature in the uranium removal reaction process is controlled at 70°C.

[0103] The obtained iron removal residue, uranium removal residue and crude cobalt hydroxide product in this example are detected, and the results show that the uranium content in the iron removal residue is 99 ppm, the cobalt content is 0.33%, the uranium content in the uranium removal residue is 2688 ppm, the cobalt content is 5.31%, the uranium removal residue accounts for 7.22% of the total amount of the iron removal residue and the uranium removal residue, and the uranium content in the crude cobalt hydroxide product is 62 ppm.

[0104] Example 3

[0105] The method for removing uranium and recovering cobalt in the low-cobalt high-impurity solution system in this example and the raw materials are basically the same as those in Example 1, except that the end pH value in the uranium removal reaction process is controlled at 6.0.

[0106] The obtained iron removal residue, uranium removal residue and crude cobalt hydroxide product in this example are detected, and the results show that the uranium content in the iron removal residue is 66 ppm, the cobalt content is 0.35%, the uranium content in the uranium removal residue is 3445 ppm, the cobalt content is 7.68%, the uranium removal residue accounts for 10.20% of the total amount of the iron removal residue and the uranium removal residue, and the uranium content in the crude cobalt hydroxide product is 32 ppm.

[0107] Example 3

[0108] The method for removing uranium and recovering cobalt in the low-cobalt high-impurity solution system of this example and the raw materials are basically the same as those of Example 1, except that the mass concentration of the dilute phosphoric acid solution during the uranium removal reaction process is 2.5%, and other conditions remain unchanged.

[0109] The iron removal residue, uranium removal residue, and crude cobalt hydroxide product obtained in this example were detected, and the results showed that the uranium content in the iron removal residue was 72 ppm, the cobalt content was 0.24%, the uranium content in the uranium removal residue was 3166 ppm, the cobalt content was 4.99%, the uranium removal residue accounted for 6.22% of the total amount of the iron removal residue and the uranium removal residue, and the uranium content in the crude cobalt hydroxide product was 56 ppm.

[0110] Example 4

[0111] The method for removing uranium and recovering cobalt in the low-cobalt high-impurity solution system of this example and the raw materials are basically the same as those of Example 1, except that the addition amount of the dilute phosphoric acid solution during the uranium removal reaction process is 200:1 (volume ratio) of the iron removal solution, and other conditions remain unchanged.

[0112] The iron removal residue, uranium removal residue, and crude cobalt hydroxide product obtained in this example were detected, and the results showed that the uranium content in the iron removal residue was 99 ppm, the cobalt content was 0.38%, the uranium content in the uranium removal residue was 2396 ppm, the cobalt content was 5.13%, the uranium removal residue accounted for 6.82% of the total amount of the iron removal residue and the uranium removal residue, and the uranium content in the crude cobalt hydroxide product was 77 ppm.

[0113] Comparative Example 1

[0114] The method for removing uranium and recovering cobalt in the low-cobalt high-impurity solution system of this example and the raw materials are basically the same as those of Example 1, except that no lime milk is added during the uranium removal reaction process, and other conditions remain unchanged.

[0115] The detection results showed that the uranium content in the iron removal residue was 103 ppm, the cobalt content was 0.36%, there was no obvious uranium removal residue, and the uranium content in the crude cobalt hydroxide product was 789 ppm, which could not meet the product sales requirements.

[0116] Comparative Example 2

[0117] The method for removing uranium and recovering cobalt in the low-cobalt high-impurity solution system of this example and the raw materials are basically the same as those of Example 1, except that the addition of the dilute phosphoric acid solution during the uranium removal reaction is completed within 3 minutes, and the reaction continues for 1.5 hours after the addition is completed; other conditions remain unchanged.

[0118] The iron removal residue, uranium removal residue, and crude cobalt hydroxide product obtained in this example were detected, and the results showed that the uranium content in the iron removal residue was 76 ppm, the cobalt content was 0.25%, the uranium content in the uranium removal residue was 834 ppm, the cobalt content was 5.68%, the uranium removal residue accounted for 5.77% of the total amount of the iron removal residue and the uranium removal residue, and the uranium content in the product was 198 ppm, which could not meet the product sales requirements.

[0119] Example 5

[0120] The raw materials of this example are the same as those of Example 1.

[0121] This example adopts continuous production, and the treatment rate of the liquid to be deuranated is 100 m 3 / h.

[0122] The process flow of this example is shown in Figure 2 The specific process of this example is as follows:

[0123] Lime milk and sodium persulfate are added to the liquid to be deuranated to perform the iron removal reaction, the reaction temperature is controlled at 60°C, the reaction end point pH value is 4.0, the reaction time is 6h, and the oxidation-reduction potential is not less than 350mv; after the reaction, solid-liquid separation is performed to obtain the iron removal residue and the liquid after iron removal;

[0124] Lime milk and dilute phosphoric acid solution are added to the liquid after iron removal to perform the deuranation reaction, wherein the dilute phosphoric acid solution is added at a uniform and slow speed, the reaction temperature is controlled at 60°C, and the reaction end point pH value is 5.5; the mass concentration of the dilute phosphoric acid solution is 1.5%, and the addition amount is liquid after iron removal:dilute phosphoric acid solution (volume ratio) = 100:1; the dilute phosphoric acid solution is added in a multi-point uniform dropping manner, the total number of phosphoric acid addition points is 50, the single-point dropping speed is 5.55mL / s, the addition is continued during the reaction, the total residence time in the phosphoric acid addition reaction tank is 60min, and after the addition of the dilute phosphoric acid solution is completed, the reaction is continued for 60min; after the reaction, solid-liquid separation is performed to obtain the deuranation residue and the liquid after deuranation.

[0125] Active magnesium oxide is directly added to the obtained liquid after deuranation to perform the cobalt precipitation reaction, forming a cobalt hydroxide precipitate, which is washed and dried to become a crude cobalt hydroxide product.

[0126] The crude cobalt hydroxide product obtained in this example is detected; the results show that the uranium content in the crude cobalt hydroxide product is 68ppm.

[0127] Water is used as the washing agent A to wash the iron removal residue, the washing time is 2h, and the iron removal washed residue and the washing liquid A are obtained. The obtained washing liquid A is returned to the process as the liquid to be deuranated for further deuranation and cobalt precipitation.

[0128] 10g / L dilute sulfuric acid is used as the washing agent B to wash the deuranation residue, the pH value of the washing end point is 4.5, the washing time is 2h, and the deuranation washed residue and the washing liquid B are obtained. The obtained washing liquid B is returned to the process as the liquid to be deuranated for further deuranation and cobalt precipitation.

[0129] The detection shows that the uranium content in the iron removal residue obtained in the embodiment is 82 ppm, the cobalt content is 0.33%, the uranium content in the uranium removal residue is 2930 ppm, the cobalt content is 6.35%, the proportion of the uranium removal residue in the total amount of the uranium removal residue and the iron removal residue is 9.65%, and the processing amount of 1000 m 3 The total amount of the iron removal residue and the uranium removal residue is about 75.76 t after the uranium removal liquid is produced; the proportion of the dissolved cobalt in the iron removal residue after washing is 34.62%, and the proportion of the uranium resolubilization is 9.01%; the proportion of the dissolved cobalt in the uranium removal residue after washing is 59.86%, and the proportion of the uranium resolubilization is 12.88%, and the cobalt recovery rate in the whole process reaches 80.24%.

[0130] Example 6

[0131] The method for removing uranium and recovering cobalt in the low-cobalt high-impurity solution system in the embodiment is basically the same as that in Example 5, except that the dilute sulfuric acid with a concentration of 10 g / L is used as the washing agent A, and the uranium removal residue is washed with water and a small amount of sulfuric acid is supplemented to control the washing end point pH value to 3.5; and other conditions are unchanged.

[0132] In the washing process of the iron removal residue, the acid concentration of the washing liquid is 10 g / L, in the washing process of the uranium removal residue, the initial dilute sulfuric acid concentration is 0 g / L, the pH value change of the washing liquid is monitored during the washing process, and sulfuric acid is supplemented in time and slowly to control the washing end point pH value to 3.5, and other conditions are unchanged.

[0133] The detection shows that the proportion of the dissolved cobalt in the iron removal residue after washing is 48.48%, and the proportion of the uranium resolubilization is 11.20%; the proportion of the dissolved cobalt in the uranium removal residue after washing is 81.04%, and the proportion of the uranium resolubilization is 22.37%, and the cobalt recovery rate in the whole process reaches 87.91%.

[0134] Comparative Example 3

[0135] The method for removing uranium and recovering cobalt in the low-cobalt high-impurity solution system in the embodiment is basically the same as that in Example 5, except that the dilute sulfuric acid with a concentration of 10 g / L is used as the washing agent A, and the uranium removal residue is washed with water and a small amount of sulfuric acid is supplemented to control the washing end point pH value to 3.5; and other conditions are unchanged.

[0136] The detection shows that the proportion of the dissolved cobalt in the iron removal residue after washing is 34.62%, and the proportion of the uranium resolubilization is 9.01%, the proportion of the dissolved cobalt in the uranium removal residue after washing is 38.56%, and the proportion of the uranium resolubilization is 10.99%, and the cobalt recovery rate in the whole process is 74.44%.

[0137] Comparative Example 4

[0138] The method for removing uranium and recovering cobalt in the low-cobalt high-impurity solution system in the embodiment is basically the same as that in Example 5, except that the dilute sulfuric acid with a concentration of 10 g / L is used as the washing agent A, and the uranium removal residue is washed with water and a small amount of sulfuric acid is supplemented to control the washing end point pH value to 3.5; and other conditions are unchanged.

[0139] After detection, the cobalt dissolution ratio in the iron slag after washing is 34.62%, the uranium dissolution ratio is 9.01%, the cobalt dissolution ratio in the uranium slag after washing is 91.89%, the uranium dissolution ratio is 79.55%, and the cobalt recovery rate in the whole process is 89.03%, but a large amount of uranium in the slag phase is re-dissolved into the system through the washing liquid B, and the uranium cannot be effectively removed from the system.

Claims

1. A method for removing uranium and recovering cobalt from a low cobalt high impurity solution system, characterized in that, The method comprises the following steps: adding lime milk and sodium persulfate into the liquid to be treated to carry out iron removal reaction, until the pH value is 3.6-4.8, and then carrying out solid-liquid separation to obtain iron removal residue and liquid after iron removal; adding lime milk and dilute phosphoric acid solution into the liquid after iron removal to carry out uranium removal reaction, wherein the dilute phosphoric acid solution is added dropwise, and after the addition of the dilute phosphoric acid solution is completed, the reaction is continued for more than 20 min, the pH value at the end of the reaction is 4.5-6.2, and then solid-liquid separation is carried out to obtain uranium removal residue and liquid after uranium removal; in the iron removal reaction, the reaction temperature is higher than 40℃, the oxidation-reduction potential is not lower than 300mv, and the reaction time is more than 2h; in the uranium removal reaction, the reaction temperature is higher than 40℃, the mass concentration of the dilute phosphoric acid solution is 1.2%-3%, the volume ratio of the dilute phosphoric acid solution to the liquid after iron removal is 1:20-250, and the dropwise adding speed of the dilute phosphoric acid solution at a single dropwise adding point is lower than 10.0mL / s.

2. The process for removal of uranium and recovery of cobalt from a low cobalt high impurity solution system as claimed in claim 1 wherein, in the iron removal reaction, the oxidation-reduction potential is not lower than 350mv, the reaction temperature is 50-70℃, and the reaction time is 4-8h.

3. The process for removal of uranium and recovery of cobalt from a low cobalt high impurity solution system as claimed in claim 1 wherein, in the uranium removal reaction, the reaction temperature is 50-70℃, the dropwise adding speed of the dilute phosphoric acid solution at a single dropwise adding point is lower than 8.0mL / s, and after the addition of the dilute phosphoric acid solution is completed, the reaction is continued for 30min-2h.

4. The method for uranium removal and cobalt recovery from a low cobalt high impurity solution system according to claim 1, characterized in that, in the uranium removal reaction, the mass concentration of the dilute phosphoric acid solution is 1.5%-2.5%, the volume ratio of the dilute phosphoric acid solution to the liquid after iron removal is 1:30-200, and the pH value at the end of the reaction is 5.0-6.

0.

5. The method for uranium removal and cobalt recovery from a low cobalt high impurity solution system according to claim 1, characterized in that, the iron removal residue is washed by using a detergent A to obtain washing liquid A and iron removal residue after washing; the detergent A contains 10g / L or less of sulfuric acid.

6. The method for uranium removal and cobalt recovery from a low cobalt high impurity solution system according to claim 1, characterized in that, the uranium removal residue is washed by using a detergent B to obtain washing liquid B and uranium-enriched uranium removal residue after washing; the detergent B contains 10g / L or less of sulfuric acid; and the pH value at the end of the washing is 3.5-4.

5.

7. The process for removal of uranium and recovery of cobalt from a low cobalt high impurity solution as claimed in claim 5 wherein, the washing liquid A is used as the liquid to be treated for uranium removal.

8. The process for removal of uranium and recovery of cobalt from a low cobalt high impurity solution as claimed in claim 6 wherein, the washing liquid B is used as the liquid to be treated for uranium removal.

9. The method for uranium removal and cobalt recovery from a low cobalt high impurity solution system according to any one of claims 1-8, characterized in that, the uranium concentration of the liquid to be treated for uranium removal is 50mg / L or less, and the liquid to be treated for uranium removal contains 3g / L or more of sulfuric acid.

10. The process for removal of uranium and recovery of cobalt from a low cobalt high impurity solution as claimed in claim 9 wherein, the uranium concentration of the liquid to be treated for uranium removal is 1-30mg / L, the cobalt concentration of the liquid to be treated for uranium removal is 0.5-4g / L, and the liquid to be treated for uranium removal contains 5-15g / L of sulfuric acid.

Images