A method for treating anthraquinone spent sulfuric acid

Abstract

The application discloses a treatment method of anthraquinone waste sulfuric acid, and comprises the following steps: (1) adding calcium carbonate and ferrous sulfate into a reactor, adding water and stirring uniformly; (2) adding anthraquinone waste sulfuric acid and hydrogen peroxide aqueous solution into the reactor in step (1), continuing to stir for a certain time after dropping is completed; (3) filtering and separating the mixture after reaction in step (2), obtaining calcium sulfate dihydrate solid and water phase, and returning the water phase into the reactor; (4) adding calcium hydroxide into the reactor, stirring uniformly, adding a flocculating agent after adjusting pH, and stirring and flocculating; filtering and separating, and obtaining filter cake and filtrate. The treatment method can react the anthraquinone waste sulfuric acid with calcium carbonate to prepare calcium sulfate dihydrate. The heat released in the reaction is used to decompose organic impurities in the waste sulfuric acid by hydrogen peroxide and ferrous sulfate, one-step purification and utilization of the anthraquinone waste sulfuric acid is realized, the filtrate after reaction can be reused, the discharge of three wastes is reduced, the treatment time and cost of the anthraquinone waste sulfuric acid are reduced, and the anthraquinone waste sulfuric acid is used in a resourceful and productized way.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization of industrial waste acid, and in particular to a method for treating anthraquinone waste sulfuric acid. Background Technology

[0002] Anthraquinone is an important chemical raw material in industrial production, widely used in the production of hydrogen peroxide, liquid crystals, dyes, pesticides, and pharmaceuticals. The phthalic anhydride process is currently the most widely used method for producing alkylanthraquinone in China. This method involves two steps: first, alkylbenzene and phthalic anhydride are reacted to generate an intermediate; then, the intermediate is catalytically dehydrated and ring-closed using concentrated sulfuric acid or fuming sulfuric acid, ultimately yielding the target product, alkylanthraquinone. The phthalic anhydride process has advantages such as low cost and simple process. However, for every ton of alkylanthraquinone produced, approximately 6-10 tons of waste sulfuric acid with a concentration below 50% is generated. This waste sulfuric acid has a high COD, dark color, and a pungent odor, making it difficult and costly to treat.

[0003] Currently, the treatment methods for anthraquinone waste sulfuric acid can be divided into the following categories: 1. Waste sulfuric acid is first purified before being used as a raw material to produce other products. This can be achieved by using resins or activated carbon to adsorb organic matter in the waste sulfuric acid, or by using oxidants to oxidize and decompose the organic matter, after which it can be used to produce magnesium sulfate, aluminum sulfate, and polyferric sulfate. The problem with this method is that the waste acid treatment is costly and time-consuming, and the wastewater generated during the production process using the purified waste acid as a raw material requires secondary treatment.

[0004] 2. First, the waste sulfuric acid is neutralized, and the separated wastewater undergoes further treatment. For example, magnesium oxide, calcium oxide, or calcium hydroxide can be reacted with the waste sulfuric acid to induce precipitation and separation. The filtrate is then treated using Fenton oxidation followed by biological treatment before being discharged. The problem with this method is that the product obtained after neutralizing the waste sulfuric acid has a high COD and poor quality, generally only suitable for solid waste treatment. The filtrate is high-COD wastewater requiring further treatment, increasing the overall cost. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems in the existing technology by providing a method for treating anthraquinone waste sulfuric acid. This method utilizes the waste sulfuric acid to produce high-quality calcium sulfate dihydrate, achieving the resource utilization of the waste sulfuric acid. Simultaneously, the heat released during the reaction, along with hydrogen peroxide and ferrous sulfate, decomposes and purifies the organic impurities in the waste sulfuric acid. The filtrate after the reaction only needs to be adjusted to alkaline pH, and after simple flocculation, precipitation, and filtration, it can be reused, reducing the discharge of waste gas, wastewater, and solid waste. This treatment method features simple process, low treatment cost, and high treatment efficiency.

[0006] The present invention achieves the above objectives using the following technical solution: A method for treating anthraquinone waste sulfuric acid includes the following steps: (1) Add calcium carbonate and ferrous sulfate to the reactor, add water, and stir until well mixed; (2) Add anthraquinone waste sulfuric acid and hydrogen peroxide aqueous solution to the reactor in step (1), and continue stirring the reaction for a certain period of time after the addition is completed; (3) Filter the mixture after the reaction in step (2) to obtain calcium sulfate dihydrate solid and aqueous phase. The aqueous phase is returned to the reaction vessel. (4) Add calcium hydroxide into the reactor, stir evenly, adjust the pH, add flocculant, stir and flocculate; filter and separate to obtain filter cake and filtrate.

[0007] Preferably, the mass ratio of ferrous sulfate to calcium carbonate in step (1) is 1:30 to 50, more preferably 1:35 to 40; the mass ratio of ferrous sulfate to water is 1:300 to 500, more preferably 1:350 to 145, and even more preferably 1:400.

[0008] Preferably, in step (2), the hydrogen peroxide aqueous solution and anthraquinone waste sulfuric acid are added separately, or they are added after being mixed. More preferably, they are added after being mixed, and the preferred method of addition is dropwise addition. The mass concentration of sulfuric acid in the anthraquinone waste sulfuric acid is 40%–50%; the COD content of the anthraquinone waste sulfuric acid is 10000–15000 mg / L. The mass concentration of the hydrogen peroxide aqueous solution is 25%–35%, wherein the mass ratio of the hydrogen peroxide aqueous solution to the anthraquinone waste sulfuric acid is 1:15–25, preferably 1:20.

[0009] Preferably, in step (2), the hydrogen peroxide aqueous solution and anthraquinone waste sulfuric acid are added dropwise over a period of 150 min to 180 min. During the reaction, the pH value is controlled to be 4 to 5 by controlling the dropwise addition time of the anthraquinone waste sulfuric acid. The reaction temperature is controlled to be 35 to 40 °C by controlling the dropwise addition time of the anthraquinone waste sulfuric acid. The stirring time after the dropwise addition is preferably 30 to 60 min.

[0010] Preferably, in step (3), the purity of the prepared calcium sulfate dihydrate is greater than 97.5%.

[0011] Preferably, in step (4), the pH value is adjusted to 8-9. The flocculant can be polyacrylamide or polyaluminum chloride, preferably polyacrylamide. The mass ratio of flocculant to water phase is 1:9000-15000. The stirring and flocculation time is preferably 15-30 min.

[0012] Preferably, in step (4), the filter cake is treated as general solid waste. The COD content in the filtrate is less than 350 mg / L, and it can be used as recycled water for the next batch of reaction; preferably, the filtrate is returned to the reactor in step (1) as recycled water.

[0013] The present invention provides a method for treating anthraquinone waste sulfuric acid that reacts with calcium carbonate to produce calcium sulfate dihydrate. The heat released from the reaction of sulfuric acid and calcium carbonate is used to decompose organic impurities in the waste sulfuric acid using hydrogen peroxide and ferrous sulfate. Compared to direct purification methods for anthraquinone waste sulfuric acid, this method has advantages such as using a smaller amount of Fenton's reagent, a lower reaction temperature, and generating less solid waste. It achieves the purification and utilization of anthraquinone waste sulfuric acid in one step, and the filtrate after the reaction can be reused, reducing the discharge of waste gas, wastewater, and solid waste, lowering the treatment time and cost of anthraquinone waste sulfuric acid, and realizing the resource-based and product-based utilization of waste acid. Detailed Implementation

[0014] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0015] Chemical oxygen demand (COD): determined according to HG / T 6109-2022; Calcium sulfate purity: determined according to GB / T 21371-2019; Organic matter content in calcium sulfate: determination method for organic matter in phosphogypsum (potassium dichromate titration method).

[0016] Example 1

[0017] Weigh 10g of ferrous sulfate and 500g of calcium carbonate and transfer them to a 10L reactor. Add 4.5L of water and start stirring. Weigh 1000g of anthraquinone waste sulfuric acid (45%) and 50g of hydrogen peroxide aqueous solution (27.5%), mix them evenly, and transfer them to a 2L constant pressure dropping funnel. Slowly add the above solution dropwise over 150 minutes, controlling the pH of the solution to 4-5 and the reaction temperature to 35-40℃ during the dropwise addition. After the dropwise addition is complete, continue stirring for 30 minutes. Filter the solid and liquid phases to separate them. Take out the filter cake, which is calcium sulfate dihydrate product. Return the aqueous phase to the reactor. Weigh 15g of calcium hydroxide and add it to the reactor. Stir evenly and control the pH of the aqueous phase to 8-9. Then add 0.5g of polyacrylamide and stir for 30 minutes. Filter the solid and liquid phases in the reactor to separate them. The filter cake is general solid waste, and the filtrate can be reused as recycled water for the next batch.

[0018] The COD of the anthraquinone waste sulfuric acid was determined to be 13850 mg / L, and its color was dark red; the purity of the obtained calcium sulfate dihydrate was 98.5%, and the organic matter content was 0.3%; the COD of the filtrate was 285 mg / L, and its color was pale yellow.

[0019] Example 2

[0020] Weigh 10g of ferrous sulfate and 500g of calcium carbonate and transfer them to a 10L reactor. Add 4.5L of recycled water from Example 1 and start stirring. Weigh 1000g of anthraquinone waste sulfuric acid (45%) and 50g of hydrogen peroxide aqueous solution (27.5%), mix them evenly, and transfer them to a 2L constant pressure dropping funnel. Slowly add the above solution dropwise over 150 minutes, controlling the pH of the solution to 4-5 and the reaction temperature to 35-40℃ during the dropwise process. After the dropwise addition is complete, continue stirring for 30 minutes. Filter the solid and liquid phases to separate them. The filter cake is calcium sulfate dihydrate product, and the aqueous phase is returned to the reactor. Weigh 15g of calcium hydroxide and add it to the reactor. Stir evenly and control the pH of the aqueous phase to 8-9. Then add 0.3g of polyaluminum chloride and stir for 30 minutes. Filter the solid and liquid phases to separate them. The filter cake is general solid waste, and the filtrate can be reused in the next batch.

[0021] The COD of the anthraquinone waste sulfuric acid was determined to be 12780 mg / L, and its color was dark red; the purity of the obtained calcium sulfate dihydrate was 97.8%, and the organic matter content was 0.4%; the COD of the filtrate was 320 mg / L, and its color was pale yellow.

[0022] Example 3

[0023] Weigh 14g of ferrous sulfate and 500g of calcium carbonate into a 10L reactor, add 4.5L of water, and start stirring. Weigh 1000g of anthraquinone waste sulfuric acid and transfer it into a 2L constant-pressure dropping funnel. Then weigh 60g of hydrogen peroxide (27.5%) into a 100ml beaker and slowly pump it into the reactor using a peristaltic pump. Control the dropping time of the anthraquinone waste sulfuric acid and hydrogen peroxide to 180min, control the pH of the solution to 4-5 during the dropping process, and the reaction temperature to 35-40℃. After the dropping is complete, continue stirring for 30min. Filter the solid and liquid phases to separate them. Take out the filter cake, which is calcium sulfate dihydrate product. Return the aqueous phase to the reactor. Weigh 15g of calcium hydroxide and add it to the reactor. Stir evenly and control the pH of the aqueous phase to 8-9. Then add 0.5g of polyacrylamide and stir for 30min. Filter the solid and liquid phases to separate them. The filter cake is general solid waste, and the filtrate can be reused for the next batch.

[0024] The COD of the anthraquinone waste sulfuric acid was determined to be 13212 mg / L, and its color was dark red; the purity of the obtained calcium sulfate dihydrate was 98%, and the organic matter content was 0.3%; the COD of the filtrate was 220 mg / L, and its color was pale yellow.

[0025] Comparative Example 1 The hydrogen peroxide aqueous solution from Example 3 was added into a 10L reactor at once, and the rest was the same as in Example 3.

[0026] The COD of the anthraquinone waste sulfuric acid was determined to be 13212 mg / L, and its color was dark red. The purity of the obtained calcium sulfate dihydrate was 97.5%, and the organic matter content was 1.7%. The COD of the filtrate was 1350 mg / L, and its color was red. The high content of organic impurities in the calcium sulfate dihydrate and the filtrate was due to the ineffective decomposition of hydrogen peroxide after the initial addition of hydrogen peroxide solution, which failed to achieve an oxidation effect.

[0027] Comparative Example 2 Replace 15g of calcium hydroxide in Example 1 with 16g of sodium hydroxide, and the rest is the same as in Example 1.

[0028] The COD of the anthraquinone waste sulfuric acid was determined to be 13850 mg / L, and its color was dark red. The purity of the obtained calcium sulfate dihydrate was 97.8%, and the organic matter content was 0.8%. The COD of the filtrate was 630 mg / L, and its color was deep yellow. This result may be because calcium hydroxide, after adjusting the pH, can generate calcium sulfate, which further reduces the content of organic impurities in the water through flocculation and precipitation.

[0029] Comparative Example 3 Weigh 500g of calcium carbonate and transfer it to a 10L reactor. Add 4.5L of water and start stirring. Weigh 1000g of anthraquinone waste sulfuric acid (45%) and transfer it to a 2L constant-pressure dropping funnel. Then weigh 60g of hydrogen peroxide (27.5%) into a 100ml beaker and slowly pump it into the reactor using a peristaltic pump. Control the dropping time of the anthraquinone waste sulfuric acid and hydrogen peroxide to be 150min, and control the pH of the solution to be 4-5 and the reaction temperature to be 35-40℃ during the dropping process. After the dropping is completed, continue stirring for 30min. Filter the solid and liquid phases to separate them, and take out the filter cake as calcium sulfate dihydrate product.

[0030] The COD of the anthraquinone waste sulfuric acid was determined to be 13212 mg / L, and its color was dark red. The purity of the obtained calcium sulfate dihydrate was 94%, and the organic matter content was 2.3%. The COD of the aqueous phase was 2634 mg / L, and its color was dark red. The results show that hydrogen peroxide alone cannot effectively decompose the organic impurities in the aqueous phase.

[0031] Comparative Example 4 Weigh 100g of anthraquinone waste sulfuric acid (45%) and add it to a 250ml three-necked flask. Add 2g of ferrous sulfate and 20g of hydrogen peroxide (27.5%) to the anthraquinone waste sulfuric acid. The reaction temperature is 40℃, and the mixture is stirred for 150min.

[0032] The COD of the anthraquinone waste sulfuric acid was measured to be 13212 mg / L, and its color was dark red; the COD of the solution after the reaction was 8832 mg / L, and its color was also dark red. The results indicate that under a strongly acidic environment, the decomposition of organic impurities by hydrogen peroxide becomes less effective, and the purification effect of the anthraquinone waste sulfuric acid is not significant.

[0033] Comparative Example 5 Weigh 100g of anthraquinone waste sulfuric acid (45%) and add it to a three-necked flask. Add 5g of ferrous sulfate and 40g of hydrogen peroxide (27.5%) to the anthraquinone waste sulfuric acid. The reaction temperature is 80℃, and the mixture is stirred for 150min.

[0034] The COD of the anthraquinone waste sulfuric acid was measured to be 13212 mg / L, and its color was dark red; the COD of the solution after the reaction was 4637 mg / L, and its color was also dark red. The results show that increasing the amounts of hydrogen peroxide and ferrous sulfate, while simultaneously raising the reaction temperature, reduced the COD of the anthraquinone waste sulfuric acid, but still did not achieve a complete purification effect.

Claims

1. A method for treating anthraquinone waste sulfuric acid, comprising the following steps: (1) Add calcium carbonate and ferrous sulfate to the reactor, add water, and stir until well mixed; (2) Add anthraquinone waste sulfuric acid and hydrogen peroxide aqueous solution dropwise to the reactor in step (1), and continue stirring the reaction for a certain period of time after the addition is completed; (3) Filter the mixture after the reaction in step (2) to obtain calcium sulfate dihydrate solid and aqueous phase. The aqueous phase is returned to the reaction vessel. (4) Add calcium hydroxide into the reactor, stir evenly, adjust the pH, add flocculant, stir and flocculate; filter and separate to obtain filter cake and filtrate; In step (2), the pH value is 4 to 5 and the reaction temperature is 35 to 40℃.

2. The processing method according to claim 1, characterized in that, In step (1), the mass ratio of ferrous sulfate to calcium carbonate is 1:30 to 50.

3. The processing method according to claim 2, characterized in that, In step (1), the mass ratio of ferrous sulfate to calcium carbonate is 1:35-40.

4. The processing method according to claim 1, characterized in that, In step (1), the mass ratio of ferrous sulfate to water is 1:300 to 500.

5. The processing method according to claim 1, characterized in that, In step (2), the hydrogen peroxide aqueous solution and anthraquinone waste sulfuric acid are added separately, or the hydrogen peroxide aqueous solution and anthraquinone waste sulfuric acid are added together.

6. The processing method according to claim 1, characterized in that, In step (2), the mass ratio of hydrogen peroxide aqueous solution to anthraquinone waste sulfuric acid is 1:15-25.

7. The processing method according to claim 1, characterized in that, In step (4), the pH value is 8 to 9.

8. The processing method according to claim 1, characterized in that, In step (4), the flocculant is polyacrylamide or polyaluminum chloride.

9. The processing method according to claim 1, characterized in that, The mass ratio of flocculant to water is 1:9000 to 15000.

10. The processing method according to claim 1, characterized in that, The filtrate from step (4) is returned to the reactor in step (1) as recycled water.