阅读说明：本技术 一种铬酸钠提纯耦合杂质资源化利用的方法 (Method for purifying sodium chromate and coupling resource utilization of impurities ) 是由 王少娜 杜浩 刘彪 王新东 李兰杰 王海旭 刘义 于 2020-07-21 设计创作，主要内容包括：本发明提供一种铬酸钠提纯耦合杂质资源化利用的方法,所述方法包括溶解、硅的脱除、碳酸根的脱除、钒的脱除和铬酸钠重结晶的步骤,利用钙源与钒酸根发生沉淀而不与铬酸根发生沉淀的特性,将化学性质类似的钒酸根与铬酸根分离；利用硅酸根、碳酸根、钒酸根与钙源结合的不同碱浓度优势区间,实现了杂质离子的分步回收,可达到除杂净化耦合杂质分步资源化利用的目的,提高了资源利用率。(The invention provides a method for purifying and coupling sodium chromate to recycle impurities, which comprises the steps of dissolving, removing silicon, removing carbonate, removing vanadium and recrystallizing sodium chromate, wherein the vanadate and chromate with similar chemical properties are separated by utilizing the characteristic that a calcium source and vanadate are precipitated but not precipitated; the method realizes the step-by-step recovery of impurity ions by utilizing different alkali concentration advantage intervals of combination of silicate, carbonate, vanadate and calcium source, can achieve the purpose of impurity removal, purification and coupling of impurity step-by-step resource utilization, and improves the resource utilization rate.)

1. A method for purifying sodium chromate and coupling impurities for resource utilization is characterized by comprising the following steps:

(1) dissolving impurity-containing sodium chromate coarse crystals to obtain a dissolved solution, wherein the alkali concentration of the dissolved solution is 280-300 g/L;

(2) mixing the dissolved solution obtained in the step (1) with a first calcium source, carrying out first reaction, and then carrying out first solid-liquid separation to obtain calcium silicate slag and a first reaction solution;

(3) diluting the first reacted liquid obtained in the step (2) to an alkali concentration of 160-250 g/L, mixing the first reacted liquid with a second calcium source, carrying out a second reaction, and carrying out solid-liquid separation to obtain calcium carbonate and a second reacted liquid;

(4) diluting the second reacted liquid obtained in the step (3) to an alkali concentration of 0-150 g/L, mixing the second reacted liquid with a tricalcium source, carrying out a third reaction, and carrying out solid-liquid separation to obtain calcium vanadate and an impurity-removed liquid;

(5) evaporating and crystallizing the impurity-removed solution obtained in the step (4) to obtain purified sodium chromate crystals;

the impurities in the sodium chromate coarse crystal comprise sodium carbonate, sodium hydroxide, sodium vanadate and sodium silicate.

2. The method according to claim 1, wherein the sodium chromate coarse crystals comprise sodium chromate coarse crystal products obtained by evaporative crystallization of leachate obtained by a process of alkali medium liquid phase oxidation chromium extraction or vanadium chromium co-extraction.

3. The method according to claim 1 or 2, wherein the sodium chromate coarse crystals contain 0 to 25 wt% and no 0;

preferably, the content of sodium hydroxide in the sodium chromate coarse crystal is 0-15 wt% and does not contain 0;

preferably, the content of sodium vanadate in the sodium chromate coarse crystal is 0-5 wt% and does not contain 0;

preferably, the content of sodium silicate in the sodium chromate coarse crystal is 0-2 wt% and does not contain 0.

4. The method according to any one of claims 1 to 3, wherein the dissolved solution in step (1) comprises any one of water, process recycle liquor or lye or a combination of at least two thereof;

preferably, the industrial circulating liquid is circulating liquid in a process of extracting chromium or vanadium and chromium by oxidizing in an alkali medium liquid phase;

preferably, the dissolving temperature is 20-100 ℃.

5. The method according to any one of claims 1 to 4, wherein the first calcium source in step (2) comprises calcium oxide and/or calcium hydroxide;

preferably, the molar ratio of the first calcium source to silicate in the dissolving solution is 1-1.5: 1;

preferably, the temperature of the first reaction is 60-100 ℃;

preferably, the time of the first reaction is more than or equal to 10min, and preferably 10-30 min.

6. The method according to any one of claims 1 to 5, wherein the calcium silicate slag in the step (2) is used for preparing a silicon-based material.

7. The method according to any one of claims 1 to 6, wherein the second calcium source in step (3) comprises calcium oxide and/or calcium hydroxide;

preferably, the molar ratio of the second calcium source to the carbonate in the first reacted liquid is 1-1.5: 1;

preferably, the temperature of the second reaction is 40-90 ℃;

preferably, the temperature of the second reaction is not less than 20min, and preferably 20-40 min.

8. The method according to any one of claims 1 to 7, wherein the third calcium source in step (4) comprises calcium oxide and/or calcium hydroxide;

preferably, the molar ratio of the third calcium source to the vanadate is 1.5-2.2: 1;

preferably, the temperature of the third reaction is 60-100 ℃;

preferably, the time of the third reaction is more than or equal to 10min, and preferably 10-40 min.

9. The method according to any one of claims 1 to 8, wherein the crystallization mother liquor obtained by the evaporative crystallization in the step (5) is recycled to a process, and the process comprises a process for extracting chromium or vanadium and chromium by alkali medium liquid phase oxidation.

10. A method according to any one of claims 1 to 9, characterized in that the method comprises the steps of:

(1) dissolving impurity-containing sodium chromate coarse crystals to obtain a dissolved solution, wherein the dissolved solution comprises any one or a combination of at least two of water, process circulating solution or alkali liquor, the alkali concentration of the dissolved solution is 280-300 g/L, and the dissolving temperature is 20-100 ℃; the sodium chromate coarse crystal comprises a sodium chromate coarse crystal product obtained by evaporating and crystallizing a leachate obtained by an alkali medium liquid-phase oxidation chromium extraction or vanadium-chromium co-extraction process, wherein the sodium chromate coarse crystal contains 0-25 wt% of sodium carbonate, 0-15 wt% of sodium hydroxide, 0-5 wt% of sodium vanadate, 0-2 wt% of sodium silicate, and the sodium chromate coarse crystal product contains no 0;

(2) mixing the dissolved solution obtained in the step (1) with a first calcium source, carrying out first reaction, and then carrying out first solid-liquid separation to obtain calcium silicate slag and a first reacted solution, wherein the calcium silicate slag is used for preparing a silicon-based material;

wherein the first calcium source comprises calcium oxide and/or calcium hydroxide, the molar ratio of the first calcium source to silicate in the dissolving solution is 1-1.5: 1, the temperature of the first reaction is 60-100 ℃, and the time is more than or equal to 10 min;

(3) Diluting the first reacted liquid obtained in the step (2), mixing the diluted first reacted liquid with a second calcium source, carrying out a second reaction, and carrying out solid-liquid separation to obtain calcium carbonate and a second reacted liquid;

the concentration of alkali after the first reaction liquid is diluted is 160-250 g/L, the second calcium source comprises calcium oxide and/or calcium hydroxide, the molar ratio of the second calcium source to carbonate in the first reaction liquid is 1-1.5: 1, the temperature of the second reaction is 40-90 ℃, and the temperature is more than or equal to 20 min;

(4) diluting the second reacted solution obtained in the step (3), mixing the diluted second reacted solution with a tricalcium source, carrying out a third reaction, and carrying out solid-liquid separation to obtain calcium vanadate and a solution after impurity removal;

the concentration of alkali after the second reaction liquid is diluted is 0-150 g/L, the third calcium source comprises calcium oxide and/or calcium hydroxide, the molar ratio of the third calcium source to vanadate radicals is 1.5-2.2: 1, the temperature of the third reaction is 60-100 ℃, and the time is more than or equal to 10 min;

(5) and (4) evaporating and crystallizing the impurity-removed solution in the step (4) to obtain purified sodium chromate crystals, and circulating a crystallization mother solution obtained by evaporation and crystallization to a process, wherein the process comprises a process for extracting chromium or vanadium and chromium by alkali medium liquid-phase oxidation.

Technical Field

The invention relates to the technical field of separation and purification, in particular to a method for purifying sodium chromate and coupling resource utilization of impurities.

Background

Sodium chromate is an important industrial chemical product and is a necessity for producing other chromium compounds. The primary/secondary resources such as chromite, chromium-containing vanadium titano-magnetite, vanadium-containing chromium mud and the like can be used for producing sodium chromate.

The prior industrialized sodium chromate production process comprises a roasting method and a liquid-phase oxidation method, wherein the traditional production method is the roasting method, and the liquid-phase oxidation method is a wet clean production technology which is developed first by the institute of process engineering of Chinese academy of sciences, and can solve the problem of three-waste pollution of the traditional roasting method at the source.

CN101817561A discloses a method for obtaining a sodium chromate product, which comprises the steps of carrying out a pressurized reaction on a sodium hydroxide solution and chromite under an oxidizing atmosphere, diluting after the reaction, carrying out liquid-solid separation to obtain a chromium-containing liquid, and carrying out impurity removal, evaporation and crystallization on the chromium-containing liquid to obtain the sodium chromate product.

CN102531056B discloses a liquid phase oxidation method, which uses chromium-containing vanadium slag as a raw material to react with sodium hydroxide solution and oxidizing gas under a pressurized condition, and liquid-solid separation is carried out after the reaction to obtain a vanadium-chromium-containing solution.

CN105400967B discloses a vanadium-chromium co-extraction method, which realizes the co-extraction of vanadium and chromium in vanadium slag under the conditions of sodium hydroxide concentration of 40-70 wt% and reaction temperature of 100-180 ℃ through the liquid-phase oxidation reaction of the vanadium slag and sodium hydroxide solution under the condition of micropore gas distribution.

Wherein, the vanadium-chromium-containing solutions obtained in CN102531056B and CN105400967B are respectively subjected to cooling crystallization to separate sodium vanadate and evaporative crystallization to separate sodium chromate, so as to obtain vanadium-chromium products. The liquid-phase oxidation process breaks through the limitations of low chromium recovery rate, high waste water environmental treatment cost, heavy pollution of chromium-containing tailings and the like in the traditional roasting process, gradually becomes a new development direction of the industry, and part of the processes enter the industrial production stage.

However, in the process of producing sodium chromate by liquid phase oxidation process, air is generally used as oxidizing gas to be introduced into the system in industrial application, and CO in the air is generated at high alkali and high temperature₂Will react with sodium hydroxide solution to generate Na₂CO₃The industrial sodium hydroxide raw material generally adopts 50 wt% of liquid alkali and also contains a certain amount of Na₂CO₃Sodium carbonate can be continuously accumulated to saturation in the system, and can be separated out along with sodium chromate crystals in the process of sodium chromate evaporation crystallization, so that the currently obtained sodium chromate productThe purity is not high, even the purity of sodium chromate is less than 60 percent when the purity is serious, and the impurity content is high.

The sodium chromate containing impurities can be sold as a product after impurity removal and purification, so that an economical and efficient method is urgently needed for purifying coarse crystals.

Disclosure of Invention

In order to solve the technical problems, the invention provides a method for purifying and coupling sodium chromate and recycling impurities, which can obtain qualified sodium chromate products through simple dissolution, efficient impurity removal and recrystallization, can recover impurity components in sodium chromate coarse crystals step by step, and improves the utilization rate of resources.

In order to achieve the purpose, the invention adopts the following technical scheme:

In a first aspect, the invention provides a method for purifying sodium chromate and coupling impurities for resource utilization, which comprises the following steps:

(1) dissolving impurity-containing sodium chromate coarse crystals to obtain a dissolved solution, wherein the alkali concentration of the dissolved solution is 280-300 g/L;

(2) mixing the dissolved solution obtained in the step (1) with a first calcium source, carrying out first reaction, and then carrying out first solid-liquid separation to obtain calcium silicate slag and a first reaction solution;

(3) diluting the first reacted liquid obtained in the step (2) to an alkali concentration of 160-250 g/L, mixing the first reacted liquid with a second calcium source, carrying out a second reaction, and carrying out solid-liquid separation to obtain calcium carbonate and a second reacted liquid;

(4) diluting the second reacted liquid obtained in the step (3) to an alkali concentration of 0-150 g/L, mixing the second reacted liquid with a tricalcium source, carrying out a third reaction, and carrying out solid-liquid separation to obtain calcium vanadate and an impurity-removed liquid;

(5) evaporating and crystallizing the impurity-removed solution obtained in the step (4) to obtain purified sodium chromate crystals;

the impurities in the sodium chromate coarse crystal comprise sodium carbonate, sodium hydroxide, sodium vanadate and sodium silicate.

The calcium source can react with carbonate, vanadate radical, silicate, aluminate and the like to generate corresponding precipitates of calcium carbonate, calcium vanadate, calcium silicate, calcium aluminate, calcium aluminosilicate and the like so as to achieve the aim of removing impurities in the solution, the calcium chromate precipitate is difficult to generate and still remains in the solution, and after pure sodium chromate-containing alkaline solution is obtained, the characteristic of solubility that the solubility of sodium chromate is greatly reduced along with the increase of the alkali concentration in the alkaline medium is subsequently utilized, and the efficient separation is realized through evaporative crystallization. In addition, the calcium source is added in three steps, so that the separation among silicon, vanadium and carbonate can be realized, the recycling of impurity resources is realized, and the utilization rate of the resources is improved.

The alkali concentration of the solution is 280-300 g/L, and may be 280g/L, 282g/L, 285g/L, 287g/L, 288g/L, 289g/L, 290g/L, 292g/L, 295g/L, 298g/L or 300g/L, for example.

According to the method, only silicon precipitation can be controlled in the step by strictly controlling the alkali concentration of the dissolving solution to be 280-300 g/L, and chromate and a calcium source do not react to reduce the yield of sodium chromate.

The concentration of the alkali after the first reaction solution is diluted in the step (3) is 160-250 g/L, for example, 160g/L, 165g/L, 170g/L, 175g/L, 180g/L, 185g/L, 190g/L, 200g/L, 210g/L, 220g/L, 230g/L, 240g/L or 250 g/L.

In the second step of the method, the alkali concentration needs to be diluted to 160-250 g/L, so that the separation effect of carbonate and vanadate radicals can be improved, carbonate can be effectively precipitated, and the purity of the final sodium chromate is improved.

The concentration of the alkali after the second reaction solution is diluted in the step (4) is 0-150 g/L, for example, 0g/L, 5g/L, 10g/L, 15g/L, 20g/L, 30g/L, 40g/L, 50g/L, 70g/L, 80g/L, 90g/L, 100g/L, 120g/L, 140g/L or 150 g/L.

The method controls the alkali concentration to be below 150g/L, greatly improves the efficiency of vanadate precipitation, and finally improves the product purity of sodium chromate.

Preferably, the sodium chromate coarse crystal comprises a sodium chromate coarse crystal product obtained by evaporating and crystallizing a leaching solution obtained by an alkali medium liquid-phase oxidation chromium extraction or vanadium-chromium co-extraction process.

Preferably, the content of sodium carbonate in the sodium chromate coarse crystal is 0-25 wt% and does not contain 0, and for example, may be 0.1 wt%, 1 wt%, 2 wt%, 5 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt%, or the like.

Preferably, the sodium hydroxide content in the sodium chromate coarse crystal is 0 to 15 wt% and does not contain 0, and may be, for example, 0.1 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 2 wt%, 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, or the like.

Preferably, the sodium vanadate content in the sodium chromate coarse crystal is 0 to 5 wt% and does not contain 0, and may be, for example, 0.1 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, or the like.

Preferably, the sodium silicate content in the sodium chromate coarse crystal is 0 to 2 wt% and does not contain 0, and may be, for example, 0.1 wt%, 0.2 wt%, 0.5 wt%, 0.7 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.4 wt%, 1.5 wt%, 1.8 wt%, or 2 wt%.

Preferably, the dissolved solution in step (1) comprises any one of water, process recycle liquid or lye or a combination of at least two thereof, wherein typical non-limiting combinations are a combination of water and process recycle liquid, a combination of water and lye, and a combination of process recycle liquid and lye.

Preferably, the industrial circulating liquid is circulating liquid in a process of extracting chromium or vanadium and chromium by oxidizing in an alkali medium liquid phase.

Preferably, the temperature of the dissolution is 20 to 100 ℃, for example, 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃ or 100 ℃.

Preferably, the first calcium source in step (2) comprises calcium oxide and/or calcium hydroxide.

Preferably, the molar ratio of the first calcium source to the silicate in the solution is 1 to 1.5:1, and may be, for example, 1:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, 1.35:1, 1.4:1, 1.45:1, or 1.5: 1.

Preferably, the temperature of the first reaction is 60 to 100 ℃, for example, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃.

Preferably, the time of the first reaction is not less than 10min, for example, 10min, 12min, 15min, 18min, 20min, 22min, 25min, 28min, 30min, 35min, 40min, 45min, 50min or 80min, and preferably 10-30 min.

Preferably, the calcium silicate slag in the step (2) is used for preparing a silicon-based material.

Preferably, the second calcium source comprises calcium oxide and/or calcium hydroxide.

Preferably, the molar ratio of the second calcium source to the carbonate in the first post-reaction solution is 1 to 1.5:1, and may be, for example, 1:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, 1.35:1, 1.4:1, 1.45:1, or 1.5: 1.

Preferably, the temperature of the second reaction is 40-90 ℃, for example, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃ or 90 ℃.

Preferably, the temperature of the second reaction is not less than 20min, for example, 20min, 21min, 25min, 27min, 28min, 30min, 32min, 35min, 38min, 40min, 42min, 45min, 48min, 50min, 60min, 80min or 90min, and preferably 20-40 min.

Preferably, the third calcium source comprises calcium oxide and/or calcium hydroxide.

Preferably, the molar ratio of the third calcium source to the vanadate is 1.5 to 2.2:1, and may be, for example, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1, or 2.2: 1.

Preferably, the temperature of the third reaction is 60 to 100 ℃, for example, 60 ℃, 62 ℃, 65 ℃, 68 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃.

Preferably, the time of the third reaction is not less than 10min, for example, 10min, 12min, 15min, 18min, 20min, 22min, 25min, 28min, 30min, 35min, 40min, 45min, 50min or 80min, and preferably 10-40 min.

Preferably, the crystallization mother liquor obtained by the evaporation crystallization in the step (5) is recycled to a process, and the process comprises a process for extracting chromium or vanadium and chromium by alkali medium liquid-phase oxidation.

As a preferred technical scheme of the invention, the method comprises the following steps:

(1) dissolving impurity-containing sodium chromate coarse crystals to obtain a dissolved solution, wherein the dissolved solution comprises any one or a combination of at least two of water, process circulating solution or alkali liquor, the alkali concentration of the dissolved solution is 280-300 g/L, and the dissolving temperature is 20-100 ℃; the sodium chromate coarse crystal comprises a sodium chromate coarse crystal product obtained by evaporating and crystallizing a leachate obtained by an alkali medium liquid-phase oxidation chromium extraction or vanadium-chromium co-extraction process, wherein the sodium chromate coarse crystal contains 0-25 wt% of sodium carbonate, 0-15 wt% of sodium hydroxide, 0-5 wt% of sodium vanadate, 0-2 wt% of sodium silicate, and the sodium chromate coarse crystal product contains no 0;

(2) mixing the dissolved solution obtained in the step (1) with a first calcium source, carrying out first reaction, and then carrying out first solid-liquid separation to obtain calcium silicate slag and a first reacted solution, wherein the calcium silicate slag is used for preparing a silicon-based material;

wherein the first calcium source comprises calcium oxide and/or calcium hydroxide, the molar ratio of the first calcium source to silicate in the dissolving solution is 1-1.5: 1, the temperature of the first reaction is 60-100 ℃, and the time is more than or equal to 10 min;

(3) Diluting the first reacted liquid obtained in the step (2), mixing the diluted first reacted liquid with a second calcium source, carrying out a second reaction, and carrying out solid-liquid separation to obtain calcium carbonate and a second reacted liquid;

the concentration of alkali after the first reaction liquid is diluted is 160-250 g/L, the second calcium source comprises calcium oxide and/or calcium hydroxide, the molar ratio of the second calcium source to carbonate in the first reaction liquid is 1-1.5: 1, the temperature of the second reaction is 40-90 ℃, and the temperature is more than or equal to 20 min;

(4) diluting the second reacted solution obtained in the step (3), mixing the diluted second reacted solution with a tricalcium source, carrying out a third reaction, and carrying out solid-liquid separation to obtain calcium vanadate and a solution after impurity removal;

the concentration of alkali after the second reaction liquid is diluted is 0-150 g/L, the third calcium source comprises calcium oxide and/or calcium hydroxide, the molar ratio of the third calcium source to vanadate radicals is 1.5-2.2: 1, the temperature of the third reaction is 60-100 ℃, and the time is more than or equal to 10 min;

(5) and (4) evaporating and crystallizing the impurity-removed solution in the step (4) to obtain purified sodium chromate crystals, and circulating a crystallization mother solution obtained by evaporation and crystallization to a process, wherein the process comprises a process for extracting chromium or vanadium and chromium by alkali medium liquid-phase oxidation.

The calcium silicate slag obtained in the step (2) can be used for preparing calcium silicate-based materials, the calcium carbonate obtained in the step (3) can be returned to a blast furnace process to be used as a calcium source, and the calcium vanadate obtained in the step (4) can be further prepared into a vanadium pentoxide product by adopting an ammonium addition reaction or an acid addition reaction, and is a common treatment method in vanadium chemical industry. Therefore, the invention can realize the step-by-step resource utilization of corresponding impurity elements by gradient impurity removal.

In the invention, the solution obtained in the step (5) after impurity removal is subjected to evaporative crystallization to obtain a qualified sodium chromate product, the evaporative crystallization is one of chemical common operations, and the specific steps and parameters are not specially limited.

The crystallization mother liquor obtained in the step (5) is substantially sodium hydroxide solution, and can be returned to the dissolution process of the liquid-phase oxidation process for continuous use.

Compared with the prior art, the invention has at least the following beneficial effects:

(1) the sodium chromate is purified by a recrystallization mode, the purity of the obtained sodium chromate is more than or equal to 98 wt%, the utilization value of the sodium chromate is improved, and the problem that the product purity does not reach the standard in the preparation link of sodium chromate products in a liquid-phase oxidation process is solved;

(2) According to the method for purifying sodium chromate and coupling impurities for resource utilization, the precipitating agent capable of precipitating the vanadate but not capable of precipitating the chromate is found between the chromate and the vanadate with similar properties, so that the separation of the vanadate and the chromate is effectively realized, and the sodium chromate and the calcium vanadate are recovered;

(3) the method for purifying and coupling sodium chromate and recycling impurities provided by the invention adopts a mode of adding a calcium source step by step, elaborately designs the precipitation steps and the sequence of the impurities, strictly controls the concentration of sodium hydroxide in the solution of each step, and preliminarily realizes the separation of the impurities, wherein the fractional removal rates of silicon, carbonate and vanadium are more than or equal to 99.0 wt%, so that the impurities in the original sodium chromate coarse crystal can be effectively recycled, and the resource utilization rate is improved.

Detailed Description

For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.