Method for preparing chromium oxide green from beta-menadione chromium-containing waste liquid

Abstract

The invention discloses a method for preparing chromium oxide green from beta-menadione chromium-containing waste liquid, which comprises the following steps: step 1, adding a chromium source into the beta-menadione chromium-containing waste liquid to adjust the acid value, and heating the solution to form feed liquid A; step 2, adding sodium hydroxide and a reducing agent into the sodium dichromate or sodium chromate solution to prepare feed liquid B for later use; step 3, slowly and continuously adding the feed liquid B into the fully stirred feed liquid A, carrying out heat preservation and curing to form feed liquid C, carrying out plate-frame pressure filtration, pulping and washing on the feed liquid C to obtain a chromium hydroxide filter cake, and calcining and crushing the chromium hydroxide filter cake to obtain a chromium oxide green product; and performing chromium removal, filter pressing, concentration evaporation and electrolysis on the washing solution to obtain sodium hydroxide and sulfuric acid. The chromium oxide green prepared by the invention has lower hexavalent chromium content than other chromium oxide green, and is more stable; the cost of the method is lower than that of chromic anhydride calcination; the washing solution can also be converted into an important raw material in the chemical industry.

Description

Technical Field

[0001] The invention belongs to the field of organic synthesis and chromium-based new material composites, and specifically relates to a method for preparing chromium oxide green from β-menadione chromium-containing waste liquid. Background Art

[0002] Chromium oxide green is an important raw material for metallic chromium, fused chromium, and refractory materials, and is mainly used for metallic chromium smelting. The smelted metallic chromium can be alloyed with iron, nickel, cobalt, titanium, aluminum, copper, etc., and then become an engineering material with heat resistance, thermal strength, wear resistance and special properties. Chromium oxide green smelting metallic chromium is used as an alloying agent for the production of various nickel- or cobalt-based high-temperature alloys, titanium alloys, aluminum-based alloys, resistance alloys and copper alloys, and some are used to produce stainless steel and heat-resistant steel. These materials are widely used in aviation, aerospace, nuclear reactors, automobiles, shipbuilding, chemicals, military and other industries. The production methods are: electrolysis, aluminum silicon thermal method and vacuum carbon reduction method. The production of metallic chromium in my country is mainly based on the aluminothermic method, and a small amount of electrolysis is used. Its usage accounts for about 80% of the consumption of alloying agents, and the usage of stainless steel and heat-resistant steel industries accounts for the largest proportion of chromium usage.

[0003] At present, the mainstream production process of chromium-containing waste liquid of menadione in my country is to prepare basic chromium sulfate from menadione residual liquid, that is, the chromium powder process. Its main application scope is mainly used for tanning leather, as a raw material for the production of chromium hydroxide, in the dye industry for the production of reactive black dyes, and as a mordant in the printing and dyeing industry. There are no reports in the prior art on the use of menadione waste liquid to prepare high-purity chromium oxide green. After 2018, due to the tightening of environmental governance and environmental protection policies by the state, the application market for basic chromium sulfate has shrunk significantly. In addition, due to the expansion of the vitamin K3 and vitamin K2 markets, the output of basic chromium sulfate is greater than the market demand, resulting in fierce competition in the entire basic chromium sulfate market and serious losses for some manufacturers. Summary of the invention

[0004] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0005] In order to achieve these purposes and other advantages of the present invention, a method for preparing chromium oxide green from chromium-containing waste liquid of β-menadione is provided, comprising the following steps:

[0006] Step 1, adding a chromium source to the chromium-containing waste liquid of β-menadione to adjust the acid value, and then heating the solution to form a feed liquid A;

[0007] Step 2: Add sodium hydroxide and a reducing agent to a sodium dichromate or sodium chromate solution to prepare a feed solution B for standby use;

[0008] Step three, slowly and continuously add liquid B to the fully stirred liquid A, and keep warm and mature to form liquid C, and filter liquid C through plate and frame pressing, pulping washing, and plate and frame washing to obtain chromium hydroxide filter cake, and the chromium hydroxide filter cake is then calcined and crushed to obtain chromium oxide green product.

[0009] Preferably, in the step 1, the chromium trioxide content in the chromium-containing waste liquid of β-menadione is 70-240 g / L, the acid value is 50-550 g / L, the chromium source is one or more of sodium dichromate, sodium chromate, and chromic anhydride, and the chromium source is added according to a mass ratio of 1000:50-450 of the chromium-containing waste liquid of β-menadione to the chromium source, so that the mass ratio of chromium trioxide to sulfuric acid in the waste liquid is 10-40:1.

[0010] Preferably, in step 1, the solution is heated to increase the Baume degree of the solution to 25-55.

[0011] Preferably, in the step 2, when preparing the feed liquid B, sodium hydroxide and a reducing agent are added to make the pH value be 2.5-14, and the pure weight ratio of sodium chromate or sodium dichromate: sodium hydroxide: reducing agent in the feed liquid B is 1:0.05-0.5:0.1-0.5.

[0012] Preferably, in the step three, firstly, liquid B is heated to 70-110° C. for 0.5-3 h, and then liquid B is continuously and slowly added to liquid A, the addition end point is pH=4.5-8.5, the acidification rate of sulfuric acid: sodium dichromate is adjusted to 50-220%, and the heat preservation and aging temperature is 0.5-8 h to form liquid C.

[0013] Preferably, in step three, the calcination temperature is 550-1600° C., and the calcination time is 3-9 hours. The washing solution can also be subjected to chromium removal, filter pressing, concentrated evaporation, and electrolysis to obtain sodium hydroxide and sulfuric acid.

[0014] Preferably, after the chromium hydroxide filter cake is obtained in step 3, the chromium hydroxide filter cake is first modified and then calcined. The specific method is:

[0015] S1, first drying the chromium hydroxide filter cake, then grinding it into powder and dispersing it into water, adding citric acid thereto, ultrasonically stirring, and then drying the mixture at low temperature to obtain citric acid-modified ultrafine chromium hydroxide;

[0016] S2. calcining the ultrafine chromium hydroxide modified by citric acid, wherein the calcination conditions are: first calcining for a period of time in an oxygen-rich atmosphere, and then calcining for a period of time in a N2 atmosphere, to finally obtain nano chromium oxide green.

[0017] Preferably, in S1, the mass of citric acid is 1-5% of the mass of the powder, the ultrasonic frequency is 50-60 kHz, the ultrasonic time is 6-12 h, the low-temperature drying temperature is -5-5°C, and the drying time is 12-24 h.

[0018] Preferably, in S2, the oxygen-enriched calcination temperature is 150-220° C., and the oxygen-enriched calcination is for 2-4 hours; the N2 atmosphere calcination temperature is 550-1600° C., and the N2 atmosphere calcination is for 3-9 hours.

[0019] The present invention at least includes the following beneficial effects: the present invention realizes the process route of preparing chromium oxide green from β-menadione waste liquid, the main content of chromium oxide green in the product can stably reach 80-99.5%, the hexavalent chromium is lower than other chromium oxide greens, and it is more stable; the product can be used to produce fused chromium products and refractory materials, and the cost is lower and the quality is more stable than chromium anhydride calcination; the washing solution is subjected to chromium removal, pressure filtration, concentration evaporation, and electrolysis to obtain sodium hydroxide and sulfuric acid as important raw materials for the chemical industry; the "three wastes" are zero-emission, which meets the requirements of modern new green, safe and environmentally friendly chemical enterprises. In addition, the present invention can also obtain nano chromium oxide green by modifying the chromium hydroxide filter cake and then calcining it.

[0020] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. DETAILED DESCRIPTION

[0021] The present invention is described in further detail below so that those skilled in the art can implement it according to the description.

[0022] Example 1

[0023] A method for preparing chromium oxide green from chromium-containing waste liquid of β-menadione, comprising the following steps:

[0024] Step 1: add 130 g of sodium dichromate to 1000 g of β-menadione chromium-containing waste liquid (chromium trioxide content of 130 g / L, acid value of 260 g / L) to adjust the acid value so that the ratio of chromium trioxide to sulfuric acid in the waste liquid reaches 15:1, and then heat the solution to increase the Baume degree to 38 to form feed liquid A;

[0025] Step 2, adding sodium hydroxide and sulfur to the sodium chromate solution in a sodium chromate: sodium hydroxide: sulfur pure weight ratio of 1:0.1:0.25 to prepare a feed solution B, adjusting the pH to 7.2, and setting aside;

[0026] Step 3, take liquid B with a pH of 7.2, heat it to 98°C and react for 2h, then slowly and continuously add liquid B to liquid A, with the addition end point being pH=6.5, adjust the acidification rate of sulfuric acid: sodium dichromate in the solution to 170%, and keep warm and mature for 3h to form liquid C; liquid C is filtered through a plate and frame filter press, pulped and washed, and washed on a plate and frame for 5 times to obtain a chromium hydroxide filter cake, and the filter cake is calcined at 1500°C for 4h, and then crushed to obtain a chromium oxide green product with a chromium trioxide content of 99.17%; the washing solution is subjected to chromium removal, filter pressing, concentrated evaporation, and electrolysis to obtain sodium hydroxide and sulfuric acid.

[0027] Example 2

[0028] A method for preparing chromium oxide green from chromium-containing waste liquid of β-menadione, comprising the following steps:

[0029] Step 1: add 300 g of sodium dichromate to 1000 g of β-menadione chromium-containing waste liquid (chromium trioxide content of 70 g / L, acid value of 350 g / L) to adjust the acid value so that the ratio of chromium trioxide to sulfuric acid in the waste liquid reaches 20:1, and then heat the solution to increase the Baume degree to 45 to form feed liquid A;

[0030] Step 2, adding sodium hydroxide and sulfur to the sodium chromate solution in a pure weight ratio of sodium chromate: sodium hydroxide: sulfur of 1:0.3:0.2 to prepare liquid B, adjusting the pH to 6.5, and setting aside;

[0031] Step 3, take liquid B with a pH of 6.5, heat it to 105°C and react for 3 hours, then slowly and continuously add liquid B to liquid A, and the addition end point is pH = 5.5, adjust the acidification rate of sulfuric acid: sodium dichromate in the solution to 160%, and keep warm and mature for 3 hours to form liquid C; the liquid C is subjected to plate and frame filter pressing, pulping washing, and plate and frame washing 3 times to obtain a chromium hydroxide filter cake, and the filter cake is calcined at 1600°C for 3 hours, and then crushed to obtain a chromium oxide green product with a chromium trioxide content of 98.72%; the washing solution is subjected to chromium removal, filter pressing, concentrated evaporation, and electrolysis to obtain sodium hydroxide and sulfuric acid.

[0032] Example 3

[0033] A method for preparing chromium oxide green from chromium-containing waste liquid of β-menadione, comprising the following steps:

[0034] Step 1, add 75g of sodium dichromate to 1000g of β-menadione chromium-containing waste liquid (chromium trioxide content of 120g / L, acid value of 180g / L) to adjust the acid value so that the ratio of chromium trioxide to sulfuric acid in the waste liquid reaches 10:1, and then heat the solution to increase the Baume degree to 42 to form feed liquid A;

[0035] Step 2, adding sodium hydroxide and sulfur to the sodium chromate solution in a sodium chromate: sodium hydroxide: sulfur pure weight ratio of 1:0.2:0.15 to prepare a feed solution B, adjusting the pH to 7.0, and setting aside;

[0036] Step 3, take liquid B with a pH of 7.0, heat it to 108°C and react for 2h, then slowly and continuously add liquid B to liquid A, the addition end point is pH=7.5, adjust the acidification rate of sulfuric acid: sodium dichromate in the solution to 210%, and keep warm and mature for 3h to form liquid C; liquid C is filtered through a plate and frame filter press, pulped and washed twice, and a chromium hydroxide filter cake is obtained. After the filter cake is calcined at 950°C for 8h, a chromium oxide green product with a chromium trioxide content of 95.00% is obtained by crushing; the washing solution is subjected to chromium removal, filter pressing, concentrated evaporation, and electrolysis to obtain sodium hydroxide and sulfuric acid.

[0037] Example 4

[0038] The difference between this embodiment and embodiment 1 is that after the chromium hydroxide filter cake is obtained in step 3, the chromium hydroxide filter cake is first modified and then calcined by:

[0039] S1, first drying the filter cake, then grinding it into powder and dispersing it into water, adding 3% citric acid by weight of the powder thereto, stirring it ultrasonically at 50 kHz for 6 hours, and then drying the mixture at a low temperature of 3° C. to obtain citric acid-modified ultrafine chromium hydroxide;

[0040] S2. Calcine the ultrafine chromium hydroxide modified by citric acid. The calcination conditions are: first calcinate at 200℃ in an oxygen-rich atmosphere for 2.5h, then calcine at 1500℃ in a N2 atmosphere for 4h, and finally obtain nano chromium oxide green with a chromium trioxide content of 99.50%. At the same time, the specific surface area of ​​the obtained nano chromium oxide green reaches 55m 2 / g, and the particle size D90 of nano chromium oxide green is 12nm.

[0041] Comparative Example 1

[0042] The difference between this comparative example and Example 4 is that the ultrafine chromium hydroxide modified by citric acid is not subjected to oxygen-enriched calcination in S2, and the rest is consistent with Example 4. The specific surface area of ​​the chromium oxide green finally obtained in this comparative example is 36 m 2 / g, the particle size D90 of chromium oxide green is 16nm, and the percentage content of chromium trioxide in the product is 94.27%. In this comparative example, since no oxygen-enriched calcination is performed, the citric acid is not completely removed, the percentage content of chromium trioxide in the product is reduced, and the particle size of chromium oxide green is increased, and the specific surface area is small.

[0043] Comparative Example 2

[0044] The difference between this comparative example and Example 4 is that in S1, no ultrasonic stirring is performed, but normal stirring is performed, and the rest is consistent with Example 4. The specific surface area of ​​the chromium oxide green finally obtained in this comparative example is 41m 2 / g, the particle size D90 of chromium oxide green is 21nm, and the percentage content of chromium trioxide in the product is 99.28%. In this comparative example, since ultrasonic stirring is not performed, the material is unevenly dispersed in water, which ultimately leads to a decrease in the specific surface area of ​​the prepared chromium oxide green and a significant increase in the particle size of the chromium oxide green.

[0045] Comparative Example 3

[0046] The difference between this comparative example and Example 4 is that no citric acid is added to S1, and the rest is the same as Example 4. The specific surface area of ​​the chromium oxide green finally obtained in this comparative example is 22 m 2 / g, the particle size D90 of chromium oxide green is 12nm, and the percentage content of chromium trioxide in the product is 99.47%. Since citric acid is not added in this comparative example, its specific surface area is greatly reduced.

[0047] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A method for preparing chromium oxide green from chromium-containing waste liquid of β-menadione, characterized in that: The following steps are involved: Step 1, adding a chromium source to the chromium-containing waste liquid of β-menadione to adjust the acid value, and then heating the solution to form a feed liquid A; Step 2: Add sodium hydroxide and a reducing agent to a sodium dichromate or sodium chromate solution to prepare a feed solution B for standby use; Step three, slowly and continuously add liquid B to the fully stirred liquid A, and keep warm and mature to form liquid C, and filter liquid C through plate and frame pressing, pulping washing, and plate and frame washing to obtain chromium hydroxide filter cake, and the chromium hydroxide filter cake is then calcined and crushed to obtain chromium oxide green product.

2. The method for preparing chromium oxide green from β-menadione chromium-containing waste liquid according to claim 1, characterized in that: In the step 1, the content of chromium trioxide in the chromium-containing waste liquid of β-menadione is 70-240 g / L, the acid value is 50-550 g / L, the chromium source is one or more of sodium dichromate, sodium chromate, and chromic anhydride, and the chromium source is added according to a mass ratio of 1000:50-450 between the chromium-containing waste liquid of β-menadione and the chromium source, so that the mass ratio of chromium trioxide in the waste liquid to sulfuric acid is 10-40:

1.

3. The method for preparing chromium oxide green from β-menadione chromium-containing waste liquid according to claim 1, characterized in that: In the step 1, the solution is heated to increase the Baume degree of the solution to 25-55.

4. The method for preparing chromium oxide green from β-menadione chromium-containing waste liquid according to claim 1, characterized in that: In the step 2, when preparing the feed liquid B, sodium hydroxide and a reducing agent are added to make the pH value be 2.5-14, the pure weight ratio of sodium chromate or sodium dichromate: sodium hydroxide: reducing agent in the feed liquid B is 1:0.05-0.5:0.1-0.5, and the reducing agent is one or more of sulfur, sodium thiosulfate or sodium sulfide.

5. The method for preparing chromium oxide green from β-menadione chromium-containing waste liquid according to claim 1, characterized in that: In the step three, firstly, liquid B is heated to 70-110° C. for 0.5-3 h, and then liquid B is continuously and slowly added to liquid A, with the pH value being 4.5-8.5 as the end point, and the acidification rate of sulfuric acid: sodium dichromate is adjusted to 50-220%, and the heat preservation and aging temperature is 0.5-8 h to form liquid C.

6. The method for preparing chromium oxide green from β-menadione chromium-containing waste liquid according to claim 1, characterized in that: In the step 3, the calcination temperature is 550-1600° C., and the calcination time is 3-9 hours. The washing solution can also be subjected to chromium removal, filter pressing, concentrated evaporation, and electrolysis to obtain sodium hydroxide and sulfuric acid.

7. The method for preparing chromium oxide green from β-menadione chromium-containing waste liquid according to claim 1, characterized in that: After the chromium hydroxide filter cake is obtained in step 3, the chromium hydroxide filter cake is first modified and then calcined. The specific method is as follows: S1, first drying the chromium hydroxide filter cake, then grinding it into powder and dispersing it into water, adding citric acid thereto, ultrasonically stirring, and then drying the mixture at low temperature to obtain citric acid-modified ultrafine chromium hydroxide; S2. calcining the ultrafine chromium hydroxide modified by citric acid, wherein the calcination conditions are: first calcining for a period of time in an oxygen-rich atmosphere, and then calcining for a period of time in a N2 atmosphere, to finally obtain nano chromium oxide green.

8. The method for preparing chromium oxide green from β-menadione chromium-containing waste liquid according to claim 7, characterized in that: In S1, the mass of citric acid is 1-5% of the mass of the powder, the ultrasonic frequency is 50-60 kHz, the ultrasonic time is 6-12 hours, the low-temperature drying temperature is -5-5°C, and the drying time is 12-24 hours.

9. The method for preparing chromium oxide green from β-menadione chromium-containing waste liquid according to claim 7, characterized in that: In the S2, the oxygen-enriched calcination temperature is 150-220° C., and the oxygen-enriched calcination is 2-4 hours. The N2 atmosphere calcination temperature is 550-1600° C., and the N2 atmosphere calcination is 3-9 hours.