CN114369719B

CN114369719B - Pretreatment and extraction separation method of tungsten-molybdenum raw material solution

Info

Publication number: CN114369719B
Application number: CN202111660824.8A
Authority: CN
Inventors: 关文娟; 夏新兵; 张贵清; 曾理; 巫圣喜; 曹佐英; 李青刚; 王明玉; 方开元; 施崇龙
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2021-12-30
Filing date: 2021-12-30
Publication date: 2022-10-18
Anticipated expiration: 2041-12-30
Also published as: CN114369719A

Abstract

The invention belongs to the field of tungsten-molybdenum separation, and particularly relates to a raw material solution pretreatment method beneficial to tungsten-molybdenum extraction separation, wherein the pH value of a tungsten-molybdenum mixed solution to be treated is controlled to be 4.5-7; then adding hydrogen peroxide to carry out a complex reaction; and regulating the pH value of the solution to be 0.5-2.5 after the reaction to obtain the pretreated solution. The invention also discloses a method for extracting the pretreated solution to realize tungsten-molybdenum separation. The solution prepared by the method does not generate a third phase in the extraction process, can achieve the effect of deeply removing molybdenum without long-time placement, has low tungsten co-extraction loss, is beneficial to improving the problem of the existing technology of extracting and separating tungsten and molybdenum by a peroxide system, simplifies the process flow and realizes industrial popularization.

Description

Pretreatment and extraction separation method of tungsten-molybdenum raw material solution

Technical Field

The invention belongs to the field of tungsten-molybdenum metallurgy, and particularly relates to a tungsten-molybdenum raw material solution pretreatment and extraction method thereof.

Background

Tungsten and molybdenum have wide industrial applications as important strategic rare metals. Tungsten and molybdenum have very similar physicochemical properties, due to the effect of lanthanide shrinkage, and are often associated in ores,are difficult to separate. The molybdenum is taken as the most difficult impurity to remove in tungsten metallurgy, and the molybdenum content in APT-0 is not more than 2 x 10 as specified in national standard GB/T10116-2007 ^-5 . With the consumption of high-grade tungsten resources, the low-grade tungsten ore with high molybdenum content and secondary resources become tungsten metallurgy raw materials, which is a necessary trend and a strategic choice for sustainable development of tungsten metallurgy industry in China. Therefore, the deep separation of tungsten and molybdenum in the tungsten resource with high molybdenum content becomes an urgent problem to be solved in tungsten metallurgy.

At present, the methods widely used in industry for removing molybdenum from tungstate, including precipitation, extraction, ion exchange, etc., are separation methods based on the difference in thiophilic property of tungsten and molybdenum. The essence of the method is that S is added into the solution under the weak alkaline condition ^2- The molybdate ions are preferentially converted into thiomolybdate ions, and then the tungsten and molybdenum are separated by means of precipitation, extraction, ion exchange adsorption and the like by utilizing the property difference of the molybdate ions and the thiomolybdate ions. These methods are useful for low molybdenum tungstate solutions (Mo/WO) ₃ <2% by mass) has a good effect, but when the molybdenum content is higher (Mo/WO) ₃ >2%), the method has great problems in molybdenum removal efficiency, cost, environmental protection and the like, and is difficult to meet the requirements of industrial production.

In addition, based on the property difference of peroxy complexes of tungsten and molybdenum, patent u.s.3969478 proposes a tungsten-molybdenum separation method, i.e. acidifying the pH of a tungsten-molybdenum mixed solution to 0.5-4.3 with acid, then adding hydrogen peroxide for complexation, and then selectively extracting molybdenum with neutral extractants such as tributyl phosphate (TBP), trialkylphosphine oxide (TRPO) and the like separately, thereby achieving deep separation of tungsten and molybdenum. On the basis, the patent CN 102876906A considers that the problems of large tungsten co-extraction amount, phase difference and the like exist when TBP or TRPO is used for separation, so that the TRPO with the volume ratio of 1-8% is added into the TBP to form a binary mixed extractant for extraction and separation of tungsten-molybdenum peroxide complex solution, and the separation effect is improved to a certain extent. In the process, in order to improve the molybdenum removal depth, the feed liquid is usually required to be placed for 24-48h. The solution is turbid after being placed due to the self-decomposition of hydrogen peroxide in the feed liquid and the instability of peroxytungstate, and the problems of third phase formation, insufficient molybdenum removal depth and the like occur in the long-term operation of the process.

The problem of solution stability can generally be solved by adding phosphorus to the solution. Phosphorus element can form phosphotungstic heteropoly acid salt with extremely high solubility with tungstate, and tungstic acid precipitate can not be generated even under high acidity. In U.S. Pat. No.3969478, zelikman adds water-soluble phosphorus salt to improve the stability of the feed solution. For the tungsten-molybdenum mixed solution with high phosphorus content, namely the solution obtained by adopting sulfur-phosphorus mixed acid to decompose under pressure (CN 108642278B) or adopting phosphoric acid to decompose tungsten ore, the phosphorus content in the solution is relatively high, so that the tungsten-molybdenum separation is carried out by adopting a peroxide complexation method in the treatment of the tungsten-molybdenum mixed solution with high phosphorus content in the patent CN 104711422A and the patent CN 104762476A. In the methods, before adding hydrogen peroxide, the acidity of the solution is generally controlled to be higher (the total acidity is 0.5-4mol/L, preferably 1-3 mol/L), and the obtained feed liquid is extracted by using a mixture of tributyl phosphate and dimethylheptyl methylphosphonate or single tributyl phosphate to realize tungsten-molybdenum separation. However, for the tungsten-molybdenum mixed solution with low phosphorus content, phosphorus, arsenic, silicon and other impurities can be preferentially and simultaneously removed under an alkaline condition, while the phosphorus is not easily removed under an acidic condition, so that the problem of stability of the acidic tungsten-molybdenum mixed solution by additionally introducing phosphorus impurities is not desirable.

In conclusion, the preparation of the tungsten-molybdenum mixed solution containing hydrogen peroxide is very important for the separation effect and stable operation of the tungsten-molybdenum separation process. The preparation process of the tungsten-molybdenum peroxy complex solution generally comprises three steps: 1) Solution pre-acidification (pH) _st1 ) (ii) a 2) Adding hydrogen peroxide for complexing; 3) Solution pH adjustment (pH) _st2 ). The detailed preparation parameters are shown in table 1.

TABLE 1 control of parameters for preparation of tungsten-molybdenum peroxo-complex solutions

As can be seen from Table 1, the pH of the solution was low (both less than 4.5) when hydrogen peroxide was added, and in the mixed solution of tungsten and molybdenum containing no phosphorus, tungsten was mainly in the form of metatungstate and tungsten-molybdenum heteropoly acid radicalThe molybdenum mainly exists in the form of hepta-poly, octa-poly isopolymolybdate and tungsten-molybdenum heteropoly acid radical. The metatungstate and tungsten-molybdenum heteropoly acid radical are difficult to be converted into peroxytungstate radical and peroxymolybdate radical with low polymerization degree under the action of hydrogen peroxide, and finally a third phase is formed in the extraction process and molybdenum removal is incomplete. In addition, for the ammonium salt mixed solution of tungsten and molybdenum, evaporation deamination is a common method for reducing the pH of the solution, which can greatly reduce the consumption of inorganic acid, but the high-temperature evaporation process accelerates the ammonium paratungstate (H) ₂ W ₁₂ O ₄₀ ^10- ) The species is not easy to complex with hydrogen peroxide. In addition, acid is added to adjust the pH value to 3-4 after evaporation deamination, and then hydrogen peroxide is complexed, metatungstate and heteropoly acid are still formed in the process, which is not beneficial to separation of tungsten and molybdenum.

Disclosure of Invention

In order to solve the technical problems that a third phase is easy to extract, long-time standing is needed, the tungsten-molybdenum extraction selectivity is not ideal and the like in the existing tungsten-molybdenum extraction method, the invention aims to provide a raw material solution pretreatment method beneficial to tungsten-molybdenum extraction and separation, and aims to solve the problem of the third phase and improve the extraction efficiency and the extraction selectivity through pretreatment of raw materials.

The second purpose of the invention is to provide the tungsten-molybdenum extraction separation method, aiming at improving the extraction efficiency and the extraction selectivity.

A raw material solution pretreatment method beneficial to extraction and separation of tungsten and molybdenum comprises the following steps:

(1) Controlling the pH value of the tungsten-molybdenum mixed solution to be treated to be 4.5-7.0;

(2) Adding hydrogen peroxide into the solution obtained in the step (1) to perform a complex reaction; wherein the addition amount of the hydrogen peroxide is more than 1.0 time of the sum of the mole numbers of the tungsten and the molybdenum;

(3) Regulating the pH value of the solution in the step (2) to be 0.5-2.5 to obtain a pretreated solution.

The invention overcomes the inherent technical thinking in the industry, innovatively controls the pH value of the tungsten-molybdenum mixed solution to be 4.5-7.0 in advance, then carries out complex reaction, and can realize the conversion of tungsten and molybdenum based on a brand-new reaction idea by matching with the consumption of hydrogen peroxide and subsequent pH control, thereby being unexpectedly beneficial to avoiding the formation of a third phase in the extraction process and improving the extraction efficiency and separation selectivity. According to the technical scheme, the solution after pretreatment is free from standing and addition of phosphide, and a phase regulator is not required to be added in the extraction process, so that a third phase can be still avoided, the extraction process can be effectively simplified, the extraction efficiency is improved, more importantly, high extraction selectivity can be still obtained, and efficient and deep separation of tungsten and molybdenum can be facilitated.

In the present invention, the type of the tungsten-molybdenum mixed solution is not particularly required, and for example, it may be a solution containing sodium salts and/or ammonium salts of W and Mo. The method can be used for realizing pretreatment regardless of the solution of ammonium salt and sodium salt of W and Mo, and improving the subsequent extraction efficiency and extraction selectivity. In the invention, the tungsten-molybdenum mixed solution can be obtained by mixing at least one W solution of ammonium tungstate and sodium tungstate with at least one Mo solution of ammonium molybdate and sodium molybdate; the solution is allowed to contain tungstate and molybdate mutual reaction products besides the tungstate and molybdate.

In the invention, no special requirement is made on the concentration of W and Mo in the tungsten-molybdenum mixed solution, and any proportion, especially a high-W high-Mo system which is difficult to treat in the industry, can be effectively pretreated by adopting the method of the invention and the separation efficiency and effect of the subsequent extraction are improved.

For example, in the tungsten-molybdenum mixed solution to be treated, the W concentration is 1-200 g/L, and the Mo concentration is 0.01-165 g/L; the W concentration may further be between 5 and 200g/L and the Mo concentration may be between 1 and 100g/L in consideration of maximizing the process value.

In the invention, the pH value of the tungsten-molybdenum mixed solution to be treated is controlled within the range required by the invention, and the subsequent extraction third phase can be avoided based on a brand-new conversion mechanism, thereby being beneficial to the subsequent extraction efficiency and extraction selectivity.

Preferably, in the step (1), the pH value is in the range of 5.0-7.0; preferably 5.5 to 6.5. The research of the invention finds that the subsequent hydrogen peroxide complexing reaction is carried out after the pH value of the tungsten-molybdenum mixed solution to be treated is regulated to the required value, and the efficiency and the effect of the subsequent extraction can be unexpectedly improved.

In the present invention, the pH can be controlled based on the existing means. For example, the pH is controlled using a mineral acid. Preferably, the inorganic acid is at least one of sulfuric acid, hydrochloric acid and nitric acid.

In the invention, the hydrogen peroxide is H ₂ O ₂ In said hydrogen peroxide solution, H ₂ O ₂ The concentration of (B) is, for example, 1 to 40wt%, preferably 20 to 30wt%.

In the step (2), the hydrogen peroxide (H) is used ₂ O ₂ In terms of moles) of tungsten and molybdenum is 1.0 to 2.5 times, preferably 1.5 to 2.5 times the sum of the moles of tungsten and molybdenum.

In the invention, the temperature of the complexation reaction is 20-40 ℃. For example, the solution of step (1) may be controlled to be within the temperature range in advance, and then hydrogen peroxide may be added to perform the complex reaction. During the reaction, the temperature may be maintained within the temperature range.

In the invention, after the complexation reaction, the pH of the reaction system is further controlled to be in a required range, so that the extraction behavior after the synergistic improvement is facilitated, and the extraction separation efficiency and the separation selectivity are improved.

Preferably, in the step (3), the pH is 1.0 to 2.0.

The invention also provides a tungsten-molybdenum extraction separation method, which is characterized in that the tungsten-molybdenum mixed solution to be treated is prepared into a pretreated solution by adopting the pretreatment method; and then extracting by using an extraction organic phase to the pretreated solution to obtain a Mo-enriched loaded organic phase and a W-enriched raffinate.

In the invention, the pretreatment of the raw material solution can improve the extraction efficiency and the extraction separation selectivity.

In the present invention, the extraction can be carried out based on the existing means.

Preferably, the extraction organic phase contains an extractant and a diluent;

preferably, the extractant comprises at least one of tributyl phosphate (TBP), trialkyl phosphine oxide (TRPO); further preferred is a mixture of tributyl ester and trialkylphosphine oxide; more preferably, the volume ratio is 20 to 80:1 to 10 of tributyl ester and trialkylphosphine oxide. According to the invention, the problem of the third phase can be effectively solved by sample pretreatment, and the third phase can be effectively avoided by adopting a single TRPO. On the basis, other synergistic extraction components such as TBP can be further added, so that the synergistic extraction rate is further improved.

In the invention, the diluent can be a component which is known in the industry and can dissolve and disperse the extracting agent, for example, the diluent is at least one of sulfonated kerosene and aviation kerosene;

in the extracted organic phase, the volume content of the extracting agent can be adjusted according to the extraction requirement, and can be 4-90 percent for example; more preferably 20 to 90%. More preferably, the volume content of the TRPO in the extracted organic phase is 1-10%, and the TRPO content is less than or equal to 80% (preferably 20-80%); the balance of diluent.

The phase ratio in the extraction process can be adjusted according to the extraction requirements, and can be, for example, 1;

the method of the invention has no special requirement on the extraction mode, and the extraction methods such as cross-flow, parallel flow, fractional distillation, countercurrent extraction and the like which are well known in the industry can be applied to the method, and the formation of a third phase can be effectively avoided.

In the present invention, the extraction method is preferably countercurrent extraction, and the number of extraction stages may be adjusted according to the extraction requirements, and for example, may be 1 to 20, and in view of the treatment efficiency, the number of extraction stages may be further 4 to 15.

The invention relates to a tungsten-molybdenum extraction separation method, which comprises the following steps:

the first step is as follows: acidifying the tungsten-molybdenum mixed solution by using inorganic acid until the pH of the solution is 4.5-7.0, preferably 5.0-7.0; more preferably 5.5 to 6.5;

the second step is that: adding hydrogen peroxide into the acidified tungsten-molybdenum mixed solution for a complex reaction to obtain a tungsten-molybdenum peroxy complex solution; the addition amount of the hydrogen peroxide is 1.0 to 2.5 times of the sum of the mole numbers of the tungsten and the molybdenum, and the preferred addition amount is 1.5 to 2.5.

The third step: the tungsten molybdenum peroxide is dissolved by complexing with inorganic acid, and the pH value of the solution is adjusted to 0.5-2.5, preferably 1.5-2.

The fourth step: and (3) extraction:

and (3) extracting and separating by using an extraction organic phase containing tributyl phosphate (TBP) and trialkyl phosphine oxide (TRPO) to obtain a Mo-enriched loaded organic phase and W-enriched raffinate.

In the technical scheme of the invention, through the pretreatment process of the parameter conditions, a third phase of subsequent extraction can be avoided on the basis of the following brand new mechanism, and the extraction efficiency and the extraction selectivity can be improved.

Advantageous effects

The invention researches and clarifies a mechanism for forming the tungsten-molybdenum extraction third phase, and further researches and discovers that based on the combination of the pretreatment process parameters, the invention can be based on a brand-new conversion mechanism unexpectedly, can avoid the formation of the subsequent third phase, can directly extract without standing or a phosphorus solution stabilizer, can avoid the third phase, avoids the precipitation risk caused by long-time standing, and can effectively improve the extraction efficiency and the extraction separation selectivity.

Drawings

FIG. 1 is a graph of different sets of extraction equilibria in example 1;

FIG. 2 is a graph of different extraction equilibria of example 2.

FIG. 3 is W-H ₂ Species distribution map of O series ([ W ]]＝0.25M，25℃)。

FIG. 4 shows W-Mo-H ₂ O-series species distribution pattern ([ W ]]＝0.5M，[Mo]=0.15m,25 ℃, wherein the proportion of W-Mo heteropoly acid species is calculated as Mo).

Detailed Description

The following examples are intended to illustrate the invention but not to further limit it.

The solution used was a single tungstate solution when the formation of the third phase was examined. The formation of a third phase was difficult to observe in a single-stage extraction experiment because the introduction of molybdenum resulted in preferential extraction of molybdenum by TRPO.

Example 1

(1-1) after a certain amount of sodium tungstate is dissolved in deionized water, firstly, acidifying with sulfuric acid until the pH value is 3.55, adding hydrogen peroxide, wherein the using amount of the hydrogen peroxide is 2 times of the molar weight of tungsten, and then, acidifying with the sulfuric acid until the pH value is 1.50 to obtain a sodium tungstate solution containing W79 g/L. The solution was treated with an extraction system consisting of 4% TRPO +96% kerosene (volume%) with an organic phase composition at a phase ratio of 1, and formation of a third phase was observed after the extraction was completed, as shown in FIG. 1a below.

(1-2) in the above (1-1) examples, only the organic phase composition was changed by 4% TRPO +60% TBP +36% kerosene (volume percent), and no third phase formation was observed after the extraction was completed, as shown in FIG. 1b below.

(1-3) in the above (1-1) example, only the pH of the first acidification step was changed to 6.54, and no formation of a third phase was observed after the extraction was completed, as shown in FIG. 1c.

Example 2

(2-1) after a certain amount of sodium tungstate is dissolved in deionized water, firstly, acidifying with sulfuric acid until the pH value is 2.51, adding hydrogen peroxide, wherein the using amount of the hydrogen peroxide is 1 time of the molar weight of tungsten, and then, acidifying with the sulfuric acid until the pH value is 1.80 to obtain a sodium tungstate solution containing 60g/L of W. The solution was treated with an extraction system consisting of 4% TRPO +96% kerosene (volume%) with the organic phase composition at a phase ratio of 1, the aqueous phase equilibrium pH after the extraction was 2.13, and a large amount of formation of the third phase was observed, as shown in FIG. 2.

(2-2) in the above (2-1) example, the pH of the first acidification was changed to 3.54, and the equilibrium pH of the aqueous phase after completion of extraction was 2.14, and more formation of the third phase was observed.

(2-3) in the above example (2-1), the pH of the first acidification was changed to 4.58, and the equilibrium pH of the aqueous phase after completion of the extraction was 2.13, and substantially no third phase was formed.

(2-4) in the above (2-1) example, the pH of the first acidification was changed to 5.47 only, the equilibrium pH of the aqueous phase after completion of the extraction was 2.14, and no formation of a third phase was observed.

(2-5) in the above (2-1) example, the pH of the first acidification was changed to 6.50 only, the equilibrium pH of the aqueous phase after completion of the extraction was 2.14, and no formation of a third phase was observed.

Example 3

(3-1) dissolving a certain amount of sodium tungstate by using deionized water, acidifying by using sulfuric acid until the pH is 3.55, adding hydrogen peroxide, wherein the using amount of the hydrogen peroxide is 0.5 times of the molar weight of tungsten, and then acidifying by using the sulfuric acid until the pH is 1.80 to obtain a sodium tungstate solution with the W100 g/L content. The solution was treated with an extraction system consisting of 4% TRPO +96% kerosene (volume%) with the organic phase composition at a phase ratio of 1, the aqueous phase equilibrium pH after the extraction was 2.10, and a large amount of formation of the third phase was observed.

(3-2) in the above example (3-1), the amount of hydrogen peroxide was changed to 2.5 times the molar amount of tungsten, and the equilibrium pH of the aqueous phase after completion of extraction was 2.12, and formation of a large amount of the third phase was observed.

(3-3) in the above (3-1) example, the pH of the first acidification was changed to 6.55, and the equilibrium pH of the aqueous phase after completion of extraction was 2.13, and more formation of the third phase was observed.

(3-4) in the above example (3-3), the amount of hydrogen peroxide was changed to 2.5 times the molar amount of tungsten, and the equilibrium pH of the aqueous phase after completion of extraction was 2.14, and no formation of a third phase was observed.

Example 4 (different pH) _st1 Influence on the depth of molybdenum removal

Preparing molybdenum-containing sodium tungstate solution (solution obtaining mode: weighing a certain amount of analytically pure sodium molybdate (Na) ₂ MoO ₄ ·2H ₂ O) and sodium tungstate (Na) ₂ WO ₄ ·2H ₂ O) reagent dissolved in deionized water), acidifying with sulfuric acid, first acidifying to control solution pH _st1 Is 3.50,4.50,5.50,6.50 ₂ O ₂ The dosage of the solution is 2.0 times of the total molar quantity of tungsten and molybdenum, and the pH value is controlled by the second step of acidification ₂ At 1.50, 4 tungsten molybdenum peroxo complex solutions (aqueous phase) were obtained, in which: no. 1 contains 101.2g/L of W and 15.89g/L of Mo; the No. 2 contains 100.7g/L of W and 15.52g/L of Mo; the No.3 alloy contains 100.2g/L of W and 16.25g/L of Mo; the No. 4 alloy contains 100.8g/L of W and 15.68g/L of Mo. Will be provided withThe solution was extracted directly with the following extractant:

the extractant comprises the following components: 4% TRPO +60% kerosene (volume percentage).

Extraction test: the organic phase and the aqueous phase are subjected to 6-stage countercurrent extraction under the condition of phase ratio of 2/1. No third phase appeared during the extraction, and the extraction results are shown in Table 4.

TABLE 4 Effect of first step acidification pH on molybdenum removal depth (6 stage countercurrent extraction)

Example 5 (Effect of standing time on depth of molybdenum removal)

Preparing molybdenum-containing sodium tungstate solution (solution obtaining mode: weighing a certain amount of analytically pure sodium molybdate (Na) ₂ MoO ₄ ·2H ₂ O) and sodium tungstate (Na) ₂ WO ₄ ·2H ₂ O) reagent dissolved in deionized water), acidifying with sulfuric acid, first acidifying to control solution pH _st1 Are 3.52,4.63,5.51,6.47 ₂ O ₂ The dosage of the solution is 2.0 times of the total molar quantity of tungsten and molybdenum, and the pH value is controlled by the second step of acidification ₂ At 1.50, 4 tungsten molybdenum peroxo complex solutions (aqueous phase) were obtained, in which: no. 1 contains 101.5g/L of W and 15.84g/L of Mo; no. 2 contains W102.7g/L and Mo 15.82g/L; no.3 contains 101.4g/L of W and 16.04g/L of Mo; no. 4 contains 103.1g/L of W and 16.18g/L of Mo. The solution was left for various times (0h, 6h,12h, 24h) and then extracted with the following extractants:

Extraction test: the organic phase and the water phase are subjected to 6-stage cross-flow extraction under the condition of 1/1 phase ratio. No third phase appeared during the extraction, and the extraction results are shown in Table 5.

TABLE 5 influence of standing time at different pH values on the depth of molybdenum removal (6 stage cross-flow extraction)

Example 6

Dissolving a certain amount of sodium molybdate and sodium tungstate reagent with pure water to prepare a sodium tungstate solution containing molybdenum, acidifying with sulfuric acid, and controlling the pH of the solution by acidification in the first step _st1 6.92，H ₂ O ₂ The dosage of the water solution is 1.5 times of the total molar quantity of tungsten and molybdenum, and the pH value is controlled by the second step of acidification _st2 1.88, obtaining the tungsten-molybdenum peroxy complexing solution, wherein the tungsten-molybdenum peroxy complexing solution contains W198.4g/L and Mo10.7g/L.

The extractant comprises the following components: 3% TRPO +70% kerosene (volume percent).

Extraction test: the organic phase and the aqueous phase are subjected to 6-stage countercurrent extraction under the condition of 2/1 phase ratio, and the raffinate contains 199.7g/L of W, 0.0024g/L of Mo and Mo/WO ₃ ＝0.953×10 ^-5 。

Example 7

Dissolving a certain amount of sodium molybdate and sodium tungstate reagent with pure water to prepare a sodium tungstate solution containing molybdenum, acidifying with nitric acid, and controlling the pH of the solution by a first acidification step _st1 5.51，H ₂ O ₂ The dosage of the second step is 2.5 times of the total molar quantity of tungsten and molybdenum, and the pH value is controlled by the second step of acidification _st2 1.0, obtaining the tungsten-molybdenum peroxy complex solution, wherein the W content is 20.25g/L, and the Mo content is 162.1g/L.

The extractant comprises the following components: 10% TRPO +80% kerosene (volume percent).

Extraction test: the organic phase and the aqueous phase are subjected to 10-stage countercurrent extraction under the condition of a phase ratio of 10/1, and raffinate contains 20.67g/L of W, 0.0065g/L of Mo and Mo/WO ₃ ＝2.49×10 ^-4 。

Example 8

Dissolving ammonium tungstate and tungsten trioxide in ammonia water to obtain ammonium tungstate solution containing molybdenum, acidifying with hydrochloric acid, and controlling pH _st1 4.53，H ₂ O ₂ The dosage of the solution is 1.0 time of the total molar quantity of tungsten and molybdenum, and the pH value is controlled by the second step of acidification _st2 2.50, obtaining the tungsten-molybdenum peroxy complexing solution, wherein the W content is 49.3g/L, and the Mo content is 1.45g/L.

The extractant comprises the following components: 6% TRPO +60% kerosene (volume percent).

Extraction test: the above organic phase withThe water phase is subjected to 7-stage countercurrent extraction under the condition of a phase ratio of 1/10, and the raffinate contains 50.4g/L of W, 0.0049g/L of Mo and Mo/WO ₃ ＝7.71×10 ^-5 。

Example 9

Dissolving a certain amount of sodium molybdate and sodium tungstate reagent with pure water to prepare a sodium tungstate solution containing molybdenum, acidifying with sulfuric acid, and controlling the pH of the solution by acidification in the first step _st1 5.02，H ₂ O ₂ The dosage of the second step is 2.0 times of the total molar quantity of tungsten and molybdenum, and the pH value is controlled by the second step of acidification _st2 0.5, obtaining tungsten-molybdenum peroxide complex solution containing 80.8g/L of W and 2.2g/L of Mo.

The extractant comprises the following components: 1% TRPO +20% kerosene (volume percentage).

Extraction test: the organic phase and the aqueous phase are subjected to 4-stage countercurrent extraction under the condition of phase ratio of 5/1, and the raffinate contains 78.1g/L of W, 0.0034g/L of Mo and Mo/WO ₃ ＝3.80×10 ^-5 。

Example 10

Dissolving a certain amount of sodium molybdate and sodium tungstate reagent with pure water to prepare a sodium tungstate solution containing molybdenum, acidifying with sulfuric acid, and controlling the pH of the solution by the first acidification step _st1 5.82，H ₂ O ₂ The dosage of the solution is 2.0 times of the total molar quantity of tungsten and molybdenum, and the pH value is controlled by the second step of acidification _st2 1.5, obtaining the tungsten-molybdenum peroxy complex solution, wherein the W content is 5.8g/L, and the Mo content is 0.01g/L.

The extractant comprises the following components: 1% TRPO +30% kerosene (volume percent).

Extraction test: the organic phase and the aqueous phase are subjected to 4-stage cocurrent extraction under the condition of 1/4 phase ratio, and the raffinate contains 5.1g/L of W, 0.0005g/L of Mo and Mo/WO ₃ ＝7.78×10 ^-5 。

Example 11

Dissolving a certain amount of sodium molybdate and sodium tungstate reagent in pure water to prepare a sodium tungstate solution containing molybdenum, acidifying with nitric acid, and controlling the pH of the solution by the first acidification step _st1 6.32，H ₂ O ₂ The dosage of the second step is 2.0 times of the total molar quantity of tungsten and molybdenum, and the pH value is controlled by the second step of acidification _st2 2.0, obtaining the tungsten-molybdenum peroxy complexing solution, wherein the W content is 80.8g/L, and the Mo content is 10.2g/L.

The composition of the extracting agent is as follows: 5% TRPO +60% kerosene (volume percent).

Extraction test: the organic phase and the aqueous phase are subjected to 6-stage fractional extraction under the condition of 2/1 phase ratio, and the raffinate contains 81.1g/L of W, 0.0021g/L of Mo and Mo/WO ₃ ＝2.05×10 ^-5 。

Example 12

Dissolving a certain amount of sodium molybdate and sodium tungstate reagent with pure water to prepare a sodium tungstate solution containing molybdenum, acidifying with sulfuric acid, and controlling the pH of the solution by the first acidification step _st1 5.54，H ₂ O ₂ The dosage of the solution is 2.0 times of the total molar quantity of tungsten and molybdenum, and the pH value is controlled by the second step of acidification _st2 1.50, obtaining the tungsten-molybdenum peroxide complex solution, wherein the tungsten-molybdenum peroxide complex solution contains 101.8g/L of W and 16.21g/L of Mo.

Extraction test: the organic phase and the aqueous phase are subjected to 6-stage countercurrent extraction under the condition of phase ratio of 2/1, and the raffinate contains 103.9g/L of W, 0.0034g/L of Mo and Mo/WO ₃ ＝2.71×10 ^-5 。

Comparative example 1

Compared to example 12, the difference is only the pH of the first acidification step _st1 3.51, the same extraction procedure was used, the raffinate contained 103.5g/L W, 0.075g/L Mo/WO ₃ ＝5.94×10 ^-4 。

Example 13

Compared to example 12, the only difference is that the extractant composition was 4% TRPO +96% kerosene (volume percent). The third phase does not appear in the extraction process, and the raffinate contains 102.5g/L of W, 0.0127g/L of Mo and Mo/WO ₃ ＝9.83×10 ^-5 。

Comparative example 2

Compared with example 13, the difference is only the pH _st1 Was 3.5. The third phase appears in the fifth and sixth stages of the extraction process, and the raffinate contains 96.8g/L of W, 0.121g/L of Mo and Mo/WO ₃ ＝9.91×10 ^-4 。

Principle analysis:

usually in a single W-H ₂ The relationship between the species distribution of tungsten and pH in O system is shown in FIG. 3Shown in the figure.

When pH is changed>8.5 in solution with tungsten WO ₄ ^2- The form exists; acidifying to pH<8.5，WO ₄ ^2- Begin to polymerize to form paratungstate W ₆ O ₂₁ ^6- ，W ₇ O ₂₄ ^6- ，H ₂ W ₁₂ O ₄₂ ^10- And the like, a precipitate is formed in the ammonium salt solution. Usually in a rapid acidification process, H as described above ₂ W ₁₂ O ₄₀ ¹⁰ Is not generated because the conversion of this species usually requires high temperatures (c)>80 c) or for a long time (hours or even days). Continuing acidification to pH of the solution<At 5.5, metatungstate H begins to exist in the solution ₂ W ₁₂ O ₄₀ ^6- Is formed when 2<pH<4, the tungsten in the solution is substantially present as metatungstate. The reaction process is basically consistent in the mixed solution of tungsten and molybdenum, the only difference is that tungsten can form W-Mo heteropoly compound with molybdenum besides the species, and the specific distribution of the related species is shown in FIG. 4.

As can be seen from fig. 4, when the tungsten-molybdenum mixed solution was acidified, numerous heteropoly compounds were formed in addition to the formation of isopolytungstates. When the pH is higher<At 8, the W-Mo heteropoly compound begins to form in the solution, and the Mo/W atomic ratio in the W-Mo heteropoly compound increases with the decrease of pH, i.e., moW ₆ O ₂₄ ^6- (pH8.0)，Mo ₂ W ₅ O ₂₄ ^6- (pH7.8)，Mo ₃ W ₄ O ₂₄ ^6- (pH7.4)，Mo ₄ W ₃ O ₂₄ ^6- (pH7.2)，Mo ₅ W ₂ O ₂₄ ^6- (pH4.6)，Mo ₆ WO ₂₄ ^6- (pH3.8)。

The third phase is formed primarily as a complex of TRPO and uncomplexed isopolytungstate, of which isopolytungstate is the weakest active on hydrogen peroxide, the most difficult to exchange with peroxygen ligands, and the reaction process is slow, and therefore at pH<4, it is difficult to achieve complete complexation of tungsten, so that a third phase is formed in the extraction process. The previous studies show thatAs the concentration of TRPO increases, the formation of the third phase increases. The addition of TBP effectively avoided the formation of the third phase, but in long-term continuous running experiments, there was still accumulation of the third phase. This is mainly to avoid the formation of metatungstate all the time, so that tungsten is not completely complexed, and finally, the accumulation of three-phase extraction compounds is caused. In addition, heteropoly compounds such as Mo with high Mo/W atom ratio generated in the acidification process ₅ W ₂ O ₂₄ ^6- ，Mo ₆ WO ₂₄ ^6- Is the main reason of the difference of the separation depth of tungsten and molybdenum in the extraction process. Such heteropoly compounds combine large amounts of molybdenum, are more difficult to depolymerize and complex than heteropoly acids with lower Mo/W atomic ratios, making it difficult to form readily extractable peroxymolybdates. Therefore, the method provided by the invention carries out hydrogen peroxide complexation of tungsten and molybdenum in a high pH range (4.5-7), can effectively avoid the formation of heteropoly compounds with high metatungstate and Mo/W atom ratio, realizes high-efficiency complexation of tungsten and molybdenum species and hydrogen peroxide, thereby avoiding the formation of a third phase and improving the deep separation of molybdenum.

Claims

1. A raw material solution pretreatment method beneficial to tungsten-molybdenum extraction and separation is characterized by comprising the following steps:

(3) And (3) regulating the pH value of the solution in the step (2) to 0.5-2.5 to obtain a pretreated solution.

2. The raw material solution pretreatment method according to claim 1, characterized in that, in the step (1), the tungsten-molybdenum mixed solution to be treated is a solution containing sodium salts and/or ammonium salts of W and Mo.

3. The raw material solution pretreatment method according to claim 2, characterized in that in the tungsten-molybdenum mixed solution to be treated, the W concentration is 1 to 200g/L, and the Mo concentration is 0.01 to 165g/L.

4. The method for pretreating a raw material solution according to claim 1, wherein in steps (1) and (3), a mineral acid is used to control the pH.

5. The method for pretreating a raw material solution according to claim 4, wherein the inorganic acid is at least one of sulfuric acid, nitric acid, and hydrochloric acid.

6. The raw material solution pretreatment method according to claim 1, wherein in the step (1), the pH value is in a range from 5.0 to 7.0.

7. The pretreatment method of a raw material solution according to claim 6, wherein in the step (1), the pH value is in the range of 5.5 to 6.5.

8. The raw material solution pretreatment method according to claim 1, wherein in the step (2), the addition amount of the hydrogen peroxide is 1.0 to 2.5 times of the sum of the molar numbers of tungsten and molybdenum.

9. The pretreatment method of a raw material solution according to claim 8, wherein in the step (2), the addition amount of the hydrogen peroxide is 1.5 to 2.5 times of the sum of the molar numbers of tungsten and molybdenum.

10. The pretreatment method for a raw material solution according to claim 1, wherein the temperature of the complexation reaction is 20 to 40 ℃.

11. The raw material solution pretreatment method according to claim 1, wherein in the step (3), the pH is 1.0 to 2.0.

12. A tungsten-molybdenum extraction separation method is characterized in that a tungsten-molybdenum mixed solution to be treated is prepared into a pretreated solution by adopting the pretreatment method of any one of claims 1 to 11; and then extracting by using an extraction organic phase to the pretreated solution to obtain a Mo-enriched loaded organic phase and a W-enriched raffinate.

13. The tungsten-molybdenum extraction separation process of claim 12, wherein the organic phase contains an extractant and a diluent.

14. The tungsten-molybdenum extraction separation method of claim 13, wherein the extractant comprises at least one of tributyl phosphate and trialkylphosphine oxide.

15. The tungsten-molybdenum extraction separation method of claim 14, wherein the extractant is a mixture of tributyl phosphate and trialkylphosphine oxide.

16. The tungsten-molybdenum extraction separation method of claim 15, wherein the volume ratio of the extractant is 20 to 80:1 to 10 of tributyl phosphate and trialkylphosphine oxide.

17. The tungsten-molybdenum extraction separation process of claim 13, wherein the diluent is at least one of sulfonated kerosene and aviation kerosene.

18. The tungsten-molybdenum extraction separation method of claim 13, wherein the volume content of the extractant in the extracted organic phase is 4 to 90%.

19. The tungsten-molybdenum extraction separation method of claim 18, wherein the volume content of the extractant in the extracted organic phase is 20-90%.

20. The tungsten-molybdenum extraction separation method according to claim 19, wherein the phase ratio in the extraction process is 1.

21. The tungsten-molybdenum extraction separation method of claim 19, wherein the extraction is at least one of cross-flow extraction, co-current extraction, fractional extraction, and counter-current extraction.

22. The tungsten-molybdenum extraction separation method of claim 19, wherein the number of extraction stages is 1 to 20.

23. The tungsten-molybdenum extraction separation method of claim 22, wherein the number of extraction stages is 4 to 15.