A method for treating a sulfocarbamide waste solution

Abstract

This disclosure provides a method for treating sulfolane waste liquid, wherein the sulfolane waste liquid is mixed with a photocatalyst and then subjected to a dark reaction and a photocatalytic reaction sequentially; wherein the photocatalyst is a BiPO4 / C3N4 composite photocatalyst. This method is green, energy-saving, simple, and efficient, and can convert sulfolane in the sulfolane waste liquid into sulfolane and sulfuric acid under normal temperature and pressure conditions without the addition of external organic reagents. In this method, sulfolane is directly released in gaseous form, reducing the time and energy costs associated with waste liquid separation; small molecule organic pollutants in the sulfolane waste liquid are degraded under photocatalysis, leaving only the sulfuric acid generated in the reaction and a small amount of the original inorganic salts after degradation.

Description

Technical Field

[0001] This disclosure relates to the field of waste liquid treatment, and more specifically, to a method for treating sulfolane waste liquid. Background Technology

[0002] Sulfolane waste liquid is a hazardous waste generated from aromatic hydrocarbon plants. Currently, industrial treatment of sulfolane waste liquid mainly employs distillation. However, due to the high water content of the waste liquid, evaporation is extremely energy-intensive, and the high temperatures can easily cause side reactions such as ring-opening of sulfolane. When treating sulfolane waste liquid using biochemical methods, sulfolane is degraded into carbon dioxide and sulfur dioxide, which cannot be utilized as resources. Therefore, efficient and energy-saving technologies for the harmless and resource-based treatment of sulfolane waste liquid are urgently needed in the market.

[0003] In recent years, the resource utilization technology of sulfolane waste liquid has attracted the attention of those skilled in the art. For example, Luoyang Petrochemical uses delayed coking technology to send sulfolane to the top of the coke tower for recycling, opening up a "green channel" for the treatment of sulfolane waste liquid. However, due to the high sulfur content in sulfolane, the process generates harmful waste gases such as hydrogen sulfide or sulfur dioxide, increasing the burden of waste gas treatment and resulting in high energy consumption.

[0004] Patent document 200610134285.3 discloses a method for recovering sulfolane containing inorganic salts. It uses a filter aid to precipitate the inorganic salts, and then removes the filter aid by vacuum distillation, thereby removing the inorganic salts from the sulfolane. This method is efficient and simple to operate, but the filter aid is toluene, a precursor to toxic substances, and this method can only remove specific inorganic salts, not other small-molecule organic pollutants in the waste liquid. Patent document 201810857047.8 uses an extraction method to recover sulfolane from waste liquid, achieving a sulfolane concentration of less than 50 mg / L after treatment. However, this method uses an extractant consisting of one or more of halogenated hydrocarbons, aromatic hydrocarbons, and ester compounds, requiring a large quantity, and similarly fails to remove small-molecule organic pollutants from the waste liquid. Although the sulfolane concentration in the treated waste liquid can be below 50 mg / L, the COD will still be higher than 100 mg / L, failing to meet emission standards. Due to the presence of small-molecule organic matter and inorganic salts, the recycling of the treated wastewater is also significantly limited. Summary of the Invention

[0005] The purpose of this disclosure is to solve the problems of high energy consumption, high toxicity, and difficulty in removing small molecule organic pollutants in the treatment of sulfolane waste liquid.

[0006] To achieve the above objectives, this disclosure provides a method for treating sulfolane waste liquid, wherein the sulfolane waste liquid is mixed with a photocatalyst and then subjected to a dark reaction and a photocatalytic reaction in sequence; wherein the photocatalyst is a BiPO4 / C3N4 composite photocatalyst.

[0007] Optionally, the BiPO4 / C3N4 composite photocatalyst comprises a BiPO4 core and C3N4 particles attached to the surface of the BiPO4 core in the form of quantum dots; based on the total weight of the BiPO4 / C3N4 composite photocatalyst, the weight percentage of BiPO4 is 60-90%, preferably 65-85%; the weight percentage of C3N4 is 10-40%, preferably 15-35%; and the specific surface area of ​​the BiPO4 / C3N4 composite photocatalyst is 2-50 m². 2 / g; preferably 4-40m 2 / g.

[0008] Optionally, based on the volume of the sulfolane waste liquid, the amount of BiPO4 / C3N4 composite photocatalyst added is 0.1-5 g / L, preferably 0.3-3 g / L.

[0009] Optionally, the COD of the sulfolane waste liquid is 20-2500 mg / L, the concentration of sulfolane is 10-200 mg / L, the concentration of acetic acid is 0-1000 mg / L, and the concentration of sulfate is 0-100 mg / L.

[0010] Optionally, the conditions for the dark reaction include: light intensity not exceeding 0.2 mW / cm². 2 Preferably, it does not exceed 0.1 mW / cm 2 The time is 10–60 min, preferably 20–40 min; the conditions for the photocatalytic reaction include: light intensity of 20–80 mW / cm². 2 The illumination time is 2-6 hours; preferably, the photocatalytic reaction is carried out under the illumination of a xenon lamp; more preferably, the xenon lamp is a 300W xenon lamp pre-installed with a 400-800nm ​​filter.

[0011] Optionally, the preparation method of the BiPO4 / C3N4 composite photocatalyst includes:

[0012] S1. A suspension containing BiPO4 precursor was obtained by mixing an aqueous phosphate solution with an aqueous bismuth nitrate solution.

[0013] S2. The suspension containing the BiPO4 precursor is mixed with melamine and heated to obtain a first mixture.

[0014] S3. Centrifuge the second mixture to obtain solid powder; calcine the solid powder.

[0015] Optionally, the concentration of the bismuth nitrate aqueous solution is 0.060–0.100 mol / L, preferably 0.070–0.090 mol / L; the concentration of the phosphate aqueous solution is 0.100–0.350 mol / L, preferably 0.150–0.300 mol / L; and the volume ratio of the bismuth nitrate aqueous solution to the phosphate aqueous solution is 1:0.5–1.5, preferably 1:0.8–1.2.

[0016] Optionally, the phosphate is at least one of NaH2PO4, Na2HPO4 and Na3PO4, preferably NaH2PO4.

[0017] Optionally, the BiPO4 precursor is bismuth nitrate pentahydrate, and the mass ratio of melamine to bismuth nitrate pentahydrate is 0.10 to 0.70, preferably 0.15 to 0.61.

[0018] Optionally, in step S1, the mixing includes stirring, and the stirring conditions include: time of 15–45 min and temperature of 25–30 °C; in step S2, the heating conditions include: temperature of 90–130 °C, preferably 100–120 °C; time of 800–1600 min, preferably 900–1500 min; in step S3, the centrifugation conditions include: time of 20–40 min, preferably 25–30 min; rotation speed of 3000–5000 r / min, preferably 4000–4500 r / min; and the calcination conditions include: temperature of 400–600 °C, preferably 500–580 °C; time of 90–200 min, preferably 100–150 min.

[0019] Through the above technical solution, this disclosure provides a method for converting and degrading small-molecule organic pollutants in sulfolane wastewater using a BiPO4 / C3N4 composite photocatalyst under visible light irradiation. This method is green, energy-saving, simple, and efficient, and can convert sulfolane in sulfolane wastewater into cyclobutane and sulfuric acid under normal temperature and pressure conditions without the addition of external organic reagents. In this method, cyclobutane is directly released in gaseous form, reducing the time and energy costs associated with wastewater separation; the small-molecule organic pollutants in the sulfolane wastewater are degraded under photocatalysis, leaving only the generated sulfuric acid and a small amount of original inorganic salts after degradation.

[0020] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Detailed Implementation

[0021] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of this disclosure.

[0022] This disclosure provides a method for treating sulfolane waste liquid, wherein the sulfolane waste liquid is mixed with a photocatalyst and then subjected to a dark reaction and a photocatalytic reaction in sequence; wherein the photocatalyst is a BiPO4 / C3N4 composite photocatalyst.

[0023] This disclosed method utilizes a BiPO4 / C3N4 composite photocatalyst as a catalyst to convert and degrade sulfolane in sulfolane wastewater under visible light irradiation. This method is green, energy-saving, simple, and efficient, converting sulfolane in sulfolane wastewater into cyclobutane and sulfuric acid under normal temperature and pressure conditions without the addition of external organic reagents. In this method, cyclobutane is directly released as a gas, reducing the time and energy costs associated with wastewater separation. The small-molecule organic pollutants in the sulfolane wastewater are degraded under photocatalysis, leaving only the generated sulfuric acid and a small amount of original inorganic salts.

[0024] According to this disclosure, the BiPO4 / C3N4 composite photocatalyst used in this disclosure includes a BiPO4 core and C3N4 particles attached to the surface of the BiPO4 core in the form of quantum dots, and the C3N4 exists in the form of quantum dots. This BiPO4 / C3N4 composite photocatalyst is beneficial for light absorption and has a good degradation effect on sulfolane waste liquid.

[0025] In this disclosure, based on the total weight of the BiPO4 / C3N4 composite photocatalyst, the weight percentage of BiPO4 can be 60-90%, preferably 65-85%; the weight percentage of C3N4 can be 10-40%, preferably 15-35%; and the specific surface area of ​​the BiPO4 / C3N4 composite photocatalyst can be 2-50 m². 2 / g; preferably 4-40m 2 / g.

[0026] According to this disclosure, based on the volume of the sulfolane waste liquid, the amount of BiPO4 / C3N4 composite photocatalyst added can be 0.1 to 5 g / L, preferably 0.3 to 3 g / L.

[0027] In one exemplary embodiment of this disclosure, the COD of the sulfolane waste liquid is 20-2500 mg / L, the concentration of sulfolane is 10-200 mg / L, the concentration of acetic acid is 0-1000 mg / L, and the concentration of sulfate is 0-100 mg / L.

[0028] According to this disclosure, the conditions for the dark reaction may include: light intensity not exceeding 0.2 mW / cm². 2 Preferably, it does not exceed 0.1 mW / cm 2 The time is 10–60 min, preferably 20–40 min; the conditions for the photocatalytic reaction may include: a light intensity of 20–80 mW / cm². 2 The illumination time is 2-6 hours; preferably, the photocatalytic reaction can be carried out under the illumination of a xenon lamp; more preferably, the xenon lamp is a 300W xenon lamp pre-installed with a 400-800nm ​​filter.

[0029] According to this disclosure, the preparation method of the BiPO4 / C3N4 composite photocatalyst may include:

[0030] S1. A suspension containing BiPO4 precursor was obtained by mixing an aqueous phosphate solution with an aqueous bismuth nitrate solution.

[0031] S2. The suspension containing the BiPO4 precursor is mixed with melamine and heated to obtain a first mixture.

[0032] S3. Centrifuge the second mixture to obtain solid powder; calcine the solid powder.

[0033] The method for preparing the BiPO4 / C3N4 composite photocatalyst disclosed herein effectively solves the problems of high energy consumption, long process, and difficulty in ensuring product uniformity caused by the traditional preparation process of BiPO4 / C3N4 composite materials, which requires the separate synthesis of BiPO4 and C3N4 before composite formation. The BiPO4 / C3N4 composite photocatalyst prepared by the method disclosed herein is more conducive to light absorption and has a good degradation effect on sulfolane waste liquid.

[0034] According to this disclosure, the concentration of the bismuth nitrate aqueous solution can be 0.060–0.100 mol / L, preferably 0.070–0.090 mol / L; the concentration of the phosphate aqueous solution can be 0.100–0.350 mol / L, preferably 0.150–0.300 mol / L; the volume ratio of the bismuth nitrate aqueous solution and the phosphate aqueous solution can be 1:0.5–1.5; preferably 1:0.8–1.2.

[0035] According to this disclosure, the phosphate can be at least one of NaH2PO4, Na2HPO4 and Na3PO4, preferably NaH2PO4.

[0036] According to this disclosure, the BiPO4 precursor can be bismuth nitrate pentahydrate, and the mass ratio of melamine to bismuth nitrate pentahydrate can be 0.10 to 0.70, preferably 0.15 to 0.61.

[0037] According to this disclosure, in step S1, the mixing can be a stirring process, and the stirring process conditions may include: a time of 15-45 min and a temperature of 25-30°C; in step S2, the heating process conditions may include: a temperature of 90-130°C, preferably 100-120°C; a time of 800-1600 min, preferably 900-1500 min; in step S3, the centrifugal separation conditions may include: a time of 20-40 min, preferably 25-30 min; a rotation speed of 3000-5000 r / min, preferably 4000-4500 r / min; and the calcination conditions may include: a temperature of 400-600°C, preferably 500-580°C; and a time of 90-200 min, preferably 100-150 min.

[0038] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0039] The preparation method of the BiPO4 / C3N4 composite photocatalyst used in Examples 1 and 2 of this disclosure is as follows:

[0040] 2.91 g of bismuth nitrate pentahydrate and 2.808 g of sodium dihydrogen phosphate were dissolved in 70 mL of water to obtain bismuth nitrate solution and sodium dihydrogen phosphate solution, respectively. The sodium dihydrogen phosphate solution was added to the bismuth nitrate solution and stirred at 26 °C for 30 min to obtain a suspension containing BiPO4 precursor.

[0041] 0.442 g of melamine was added to a suspension containing BiPO4 precursor, stirred at room temperature for 30 min, and heated in a hydrothermal reactor at 160 °C for 24 h to obtain the first mixture.

[0042] The first mixture was centrifuged to obtain melamine-loaded BiPO4 powder. The melamine-loaded BiPO4 powder was then placed in a crucible and calcined to obtain the BiPO4 / C3N4 composite photocatalyst used in the examples. The centrifugation time was 30 min, the rotation speed was 4000 r / min, and the calcination conditions included calcination at 550°C for 2 h in a muffle furnace.

[0043] Example 1

[0044] The waste liquid of sulfolane was mixed with the BiPO4 / C3N4 composite photocatalyst to obtain a mixed solution, wherein the amount of BiPO4 / C3N4 composite photocatalyst added was 2 g / L based on the volume of the waste liquid of sulfolane.

[0045] Before photocatalytic treatment, the BiPO4 / C3N4 composite photocatalyst was subjected to dark adsorption with sulfolane waste liquid for 30 minutes. A 300W xenon lamp with a pre-installed 400–800 nm filter (illuminance of 50 mW / cm²) was used. 2 Photocatalytic treatment of sulfolane waste liquid with added photocatalyst.

[0046] In this embodiment, the COD of the sulfolane wastewater to be treated was 2196 mg / L, the initial concentration of sulfolane was 97.2 mg / L, the initial concentration of acetic acid was 72.1 mg / L, and the initial concentration of sulfate was 34.3 mg / L. After 2 hours of photocatalytic reaction, the sulfolane wastewater was tested, and the COD was found to be 44 mg / L, the acetate concentration was 18.6 mg / L, and the sulfate ion concentration was 113.7 mg / L.

[0047] Calculations show that the COD removal rate reaches 98.0%, and all the sulfur in sulfolane is converted into sulfate.

[0048] Example 2

[0049] The waste liquid of sulfolane was mixed with BiPO4 / C3N4 composite photocatalyst to obtain a mixed solution, wherein the amount of BiPO4 / C3N4 composite photocatalyst added was 0.5 g / L based on the volume of the waste liquid of sulfolane.

[0050] Before photocatalytic treatment, the BiPO4 / C3N4 composite photocatalyst was subjected to dark adsorption with sulfolane waste liquid for 30 minutes. A 300W xenon lamp with a pre-installed 400–800 nm filter (illuminance of 50 mW / cm²) was used. 2 Photocatalytic treatment of sulfolane waste liquid with added photocatalyst.

[0051] In this embodiment, the COD of the sulfolane wastewater to be treated was 201 mg / L, the concentration of sulfolane was 25.2 mg / L, and the concentration of sulfate was 29.2 mg / L. The concentration of photocatalyst in the wastewater was 0.5 g / L. After 2 hours of photocatalytic reaction, the COD of the solution was 43 mg / L, the concentration of acetic acid was 0.2 mg / L, and the concentration of sulfate ions was 49.8 mg / L.

[0052] Calculations show that the COD removal rate reached 78.6%, and all the sulfur in sulfolane was converted into sulfate.

[0053] Comparative Example 1

[0054] The testing method for this comparative example is the same as in Example 1, except that no photocatalyst is added to the sulfolane waste liquid; it is directly irradiated under visible light. Specifically, a 300W xenon lamp pre-loaded with a 400-800nm ​​filter is used for visible light photocatalytic treatment of the sulfolane waste liquid. A dark treatment period of 30 minutes is performed before turning on the light source. The COD concentration of the sulfolane waste liquid is 2196 mg / L, the initial concentration of sulfolane is 97.2 mg / L, the initial concentration of acetic acid is 72.1 mg / L, and the initial concentration of sulfate is 34.3 mg / L. After 2 hours of photocatalytic reaction, the sulfolane waste liquid is tested, and the measured COD is 2142 mg / L, the acetate concentration is 70.7 mg / L, and the sulfate ion concentration is 32.4 mg / L.

[0055] Calculations show that the COD removal rate is 2%, and the sulfur in sulfolane is not converted into sulfate.

[0056] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0057] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0058] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for treating sulfolane waste liquid, characterized in that, The sulfolane waste liquid was mixed with a photocatalyst and then subjected to a dark reaction and a photocatalytic reaction in sequence; wherein, the photocatalyst was a BiPO4 / C3N4 composite photocatalyst. Based on the volume of the sulfolane waste liquid, the amount of BiPO4 / C3N4 composite photocatalyst added is 0.1~5 g / L; The preparation method of the BiPO4 / C3N4 composite photocatalyst includes: S1. A suspension containing BiPO4 precursor was obtained by mixing an aqueous phosphate solution with an aqueous bismuth nitrate solution. S2. The suspension containing the BiPO4 precursor is mixed with melamine and heated to obtain a first mixture. S3. Centrifuge the first mixture to obtain solid powder; calcine the solid powder. The BiPO4 / C3N4 composite photocatalyst comprises a BiPO4 core and C3N4 particles attached to the surface of the BiPO4 core in the form of quantum dots. Based on the total weight of the BiPO4 / C3N4 composite photocatalyst, the weight percentage of BiPO4 is 60-90%, and the weight percentage of C3N4 is 10-40%. The specific surface area of ​​the BiPO4 / C3N4 composite photocatalyst is 2-50 m². 2 / g.

2. The method according to claim 1, wherein, Based on the total weight of the BiPO4 / C3N4 composite photocatalyst, the weight percentage of BiPO4 is 65-85%.

3. The method according to claim 1, wherein, Based on the total weight of the BiPO4 / C3N4 composite photocatalyst, the weight percentage of C3N4 is 15-35%.

4. The method according to claim 1, wherein, The specific surface area of ​​the BiPO4 / C3N4 composite photocatalyst is 4-40 m². 2 / g.

5. The method according to claim 1, wherein, Based on the volume of the sulfolane waste liquid, the amount of BiPO4 / C3N4 composite photocatalyst added is 0.3~3g / L.

6. The method according to claim 1, wherein, The sulfolane waste liquid has a COD of 50~2500 mg / L, a sulfolane concentration of 10~200 mg / L, an acetic acid concentration of 0~1000 mg / L, and a sulfate concentration of 0~100 mg / L.

7. The method according to claim 1, wherein, The conditions for the dark reaction include: light intensity not exceeding 0.2 mW / cm². 2 The time is 10-60 min; the conditions for the photocatalytic reaction include: light intensity of 20-80 mW / cm². 2 The light exposure time is 2-6 hours.

8. The method according to claim 1, wherein, The light intensity of the dark reaction does not exceed 0.1 mW / cm². 2 .

9. The method according to claim 1, wherein, The dark reaction time is 20-40 minutes.

10. The method according to claim 1, wherein, The photocatalytic reaction is carried out under the illumination of a xenon lamp.

11. The method according to claim 10, wherein, The xenon lamp is a 300W xenon lamp pre-installed with a 400~800nm ​​filter.

12. The method according to claim 1, wherein, The concentration of the bismuth nitrate aqueous solution is 0.060~0.100 mol / L, and the concentration of the phosphate aqueous solution is 0.100~0.350 mol / L; The volume ratio of the bismuth nitrate aqueous solution to the phosphate aqueous solution is 1:0.5~1.

5.

13. The method according to claim 1, wherein, The concentration of the bismuth nitrate aqueous solution is 0.070~0.090 mol / L.

14. The method according to claim 1, wherein, The concentration of the phosphate aqueous solution is 0.150~0.300 mol / L.

15. The method according to claim 1, wherein, The volume ratio of the bismuth nitrate aqueous solution to the phosphate aqueous solution is 1:0.8~1.

2.

16. The method according to claim 1, wherein, The phosphate is at least one of NaH2PO4, Na2HPO4 and Na3PO4.

17. The method according to claim 1, wherein, The phosphate is NaH2PO4.

18. The method according to claim 1, wherein, The bismuth nitrate is bismuth nitrate pentahydrate, and the mass ratio of melamine to bismuth nitrate pentahydrate is 0.10~0.

70.

19. The method according to claim 18, wherein, The mass ratio of melamine to bismuth nitrate pentahydrate is 0.15 to 0.

61.

20. The method according to claim 1, wherein, In step S1, the mixing includes a stirring process, and the stirring process conditions include: a time of 15~45 min and a temperature of 25~30℃. In step S2, the conditions for the heat treatment include: a temperature of 90~130℃ and a time of 800~1600min; In step S3, the centrifugal separation conditions include: a time of 20-40 min and a rotation speed of 3000-5000 r / min; the calcination conditions include: a temperature of 400-600℃ and a time of 90-200 min.

21. The method according to claim 1, wherein, In step S2, the temperature of the heat treatment is 100~120℃.

22. The method according to claim 1, wherein, In step S2, the heating treatment time is 900~1500 min.

23. The method according to claim 1, wherein, In step S3, the centrifugation time is 25-30 min.

24. The method according to claim 1, wherein, In step S3, the centrifugal separation speed is 4000~4500 r / min.

25. The method according to claim 1, wherein, In step S3, the calcination temperature is 500~580℃.

26. The method according to claim 1, wherein, In step S3, the calcination time is 100~150 min.