A wastewater treatment method in the preparation of oxidized starch

Abstract

This invention relates to a wastewater treatment method in the preparation of oxidized starch, belonging to the field of wastewater treatment technology. The invention discloses a wastewater treatment method in the preparation of oxidized starch, comprising the following steps: (1) placing wastewater in two containers, then adding catalysts to each, and simultaneously introducing ozone. The containers are connected by pipes on both sides, and a submersible pump is turned on to circulate the wastewater between the two containers; (2) then adding an adsorbent, and ultrasonically treating at room temperature to form wastewater a; (3) adding sodium hydroxide and sodium carbonate to wastewater a, stirring and mixing, allowing it to stand, filtering, and discharging the filtrate. Ozone and the catalyst release ·OH in the water, free radicals oxidize and decompose organic matter, the adsorbent converts sulfides into elemental sulfur, and simultaneously adsorbs it under van der Waals forces. Additionally, alkaline substances are added to precipitate the salts in the wastewater, which are then filtered out. Therefore, this invention can effectively remove impurities from wastewater, resulting in a precipitate.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology and relates to a wastewater treatment method in the preparation of oxidized starch. Background Technology

[0002] Starch is a green and environmentally friendly renewable resource, and the demands of sustainable development have made it increasingly popular. Oxidized starch is a starch derivative obtained by chemically modifying native starch, and it is widely used in industries such as papermaking, food, and pharmaceuticals. The production of oxidized starch often generates unavoidable industrial wastewater, the main pollutant being COD, which includes organic matter, nitrites, sulfides, and ferrous salts.

[0003] Chinese patent CN114031692A discloses a method for reducing the COD of wastewater in the process of oxidized starch preparation. This patented method increases the degree of oxidation and carboxyl content by adding a cross-linking agent, thereby accelerating the starch oxidation reaction and degrading organic matter. Sulfides in the wastewater can damage the gills and gill tissues of aquatic organisms, leading to respiratory distress and death; however, in this invention, sulfides cannot be removed from the wastewater. Therefore, the wastewater treatment method provided by this invention in the process of oxidized starch preparation can effectively solve the above problems. Summary of the Invention

[0004] This invention relates to a wastewater treatment method in the preparation of oxidized starch, belonging to the field of wastewater treatment technology. The invention discloses a wastewater treatment method in the preparation of oxidized starch, comprising the following steps: (1) placing wastewater in two containers, then adding catalysts to each, and simultaneously introducing ozone. The containers are connected by pipes on both sides, and a submersible pump is turned on to circulate the wastewater between the two containers; (2) then adding an adsorbent, and ultrasonically treating at room temperature to form wastewater a; (3) adding sodium hydroxide and sodium carbonate to wastewater a, stirring and mixing, allowing it to stand, filtering, and discharging the filtrate. Ozone and the catalyst release ·OH in the water, free radicals oxidize and decompose organic matter, the adsorbent converts sulfides into elemental sulfur, and simultaneously adsorbs it under van der Waals forces. Additionally, alkaline substances are added to precipitate the salts in the wastewater, which are then filtered out. Therefore, this invention can effectively remove impurities from wastewater, resulting in a precipitate.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for treating wastewater during the preparation of oxidized starch, the method comprising the following steps:

[0007] (1) Place the wastewater in two containers, then add the catalyst to each container and simultaneously introduce ozone. Connect the two sides of the containers with pipes and turn on the submersible pump to circulate the wastewater between the two containers.

[0008] (2) Then add an adsorbent and ultrasonically treat at room temperature to form wastewater a;

[0009] (3) Add sodium hydroxide and sodium carbonate to wastewater a, stir and mix, let stand and filter, and discharge the filtrate.

[0010] Furthermore, in step (1), the solid-liquid ratio of the catalyst to the wastewater is 10:1-5 g / L, and the circulation time is 10-20 min.

[0011] Further, the catalyst preparation method in step (1) is as follows: the titanium silicon molecular sieve is washed with deionized water, dried in an oven, taken out and immersed in a nitrate mixed solution and shaken, then filtered, and the solid is calcined to obtain the catalyst.

[0012] Furthermore, the drying temperature and time are 60-70℃ and 1-2h, respectively, and the solid-liquid ratio of the titanium-silicon molecular sieve to the nitrate mixed solution is 1-2:10g / mL. The nitrate mixed solution is composed of manganese nitrate solution, ferric nitrate solution and cerium nitrate solution in a volume ratio of 1:1:1, and the mass fractions of the manganese nitrate solution, ferric nitrate solution and cerium nitrate solution are 1-1.5%, 1%, and 1.5-2%, respectively.

[0013] Furthermore, the oscillation time and speed are 8-10h and 180r / min, respectively, and the calcination temperature and time are 500-600℃ and 3-4h, respectively.

[0014] Furthermore, the preparation method of the adsorbent in step (2) includes the following steps:

[0015] A1: Mix graphite powder with sodium nitrate and sulfuric acid solution, dissolve the powder, add potassium permanganate, heat and stir, add ultrapure water and continue stirring to form mixture a;

[0016] A2: Add hydrogen peroxide solution to mixture a, let it stand to precipitate, filter, wash the precipitate with deionized water, and freeze-dry to obtain the initial adsorbent;

[0017] A3: The initial adsorbent is dispersed in deionized water, nitrogen gas is introduced, then ferrous chloride tetrahydrate is added and stirred to mix, ammonia water is added and stirring is continued, the mixture is filtered and separated, the solid is washed with deionized water and freeze-dried to obtain the adsorbent.

[0018] Further, in step A1, the total mass of graphite powder, sodium nitrate, and potassium permanganate has a solid-liquid ratio of 4-5:20-26 g / mL to the sulfuric acid solution, wherein the mass ratio of graphite powder, sodium nitrate, and potassium permanganate is 1:1.5:3, the mass fraction of the sulfuric acid solution is 90-95%, the heating temperature is 60-80℃, and the amount of ultrapure water added accounts for 70-80% of the volume of the mixed solution a.

[0019] Further, in step A2, the volume ratio of the mixture a to the hydrogen peroxide solution is 100:0.5-0.6, wherein the mass fraction of the hydrogen peroxide solution is 20-30%, the standing time is 3-4 hours, and the freeze-drying temperature and time are -2 to -6°C and 24 hours, respectively.

[0020] Furthermore, in step A3, the mass ratio of the primary adsorbent, deionized water, ferrous chloride tetrahydrate, and ammonia is 2.5:5:10:1.5, wherein the mass fraction of ammonia is 25%, and the freeze-drying temperature and time are -2 to -6°C and 24 hours, respectively.

[0021] Furthermore, in step (2), the adsorbent accounts for 20-30% of the mass of wastewater a, the ultrasonic time is 120-180 min, and in step (3), the amount of sodium hydroxide and sodium carbonate added accounts for 2-3% and 8-10% of the mass of wastewater a, respectively.

[0022] The beneficial effects of this invention are:

[0023] 1. Ozone, under the action of a catalyst, enhances the release of ·OH in water, thereby decomposing organic matter through free radical oxidation;

[0024] 2. The adsorbent converts sulfides into elemental sulfur and adsorbs them under van der Waals forces, thereby separating the sulfides in the wastewater. In addition, sodium carbonate and sodium hydroxide are added to cause the salts in the wastewater to form ferrous carbonate precipitate. Under these conditions, elemental sulfur will not react with sodium hydroxide, and the precipitate is removed by filtration. Detailed Implementation

[0025] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with embodiments, is provided below.

[0026] Example 1

[0027] A method for treating wastewater during the preparation of oxidized starch, the method comprising the following steps:

[0028] (1) Place the wastewater in two containers, then add the catalyst to each container and simultaneously introduce ozone. Connect the two sides of the containers with pipes and turn on the submersible pump to circulate the wastewater between the two containers.

[0029] (2) Then add an adsorbent and ultrasonically treat at room temperature to form wastewater a;

[0030] (3) Add sodium hydroxide and sodium carbonate to wastewater a, stir and mix, let stand and filter, and discharge the filtrate.

[0031] In step (1), the solid-liquid ratio of the catalyst to the wastewater is 10:1 g / L, and the circulation time is 10 min.

[0032] The catalyst preparation method in step (1) is as follows: the titanium silicon molecular sieve is washed with deionized water, dried in an oven, taken out and immersed in a nitrate mixed solution and shaken, then filtered, and the solid is calcined to obtain the catalyst.

[0033] The drying temperature and time are 60℃ and 1h, respectively. The solid-liquid ratio of the titanium-silicon molecular sieve and the nitrate mixed solution is 1:10 g / mL. The nitrate mixed solution is composed of manganese nitrate solution, ferric nitrate solution and cerium nitrate solution in a volume ratio of 1:1:1. The mass fractions of the manganese nitrate solution, ferric nitrate solution and cerium nitrate solution are 1%, 1% and 1.5%, respectively.

[0034] The oscillation time and speed are 8h and 180r / min, respectively, and the calcination temperature and time are 500℃ and 3h, respectively.

[0035] The preparation method of the adsorbent in step (2) includes the following steps:

[0036] A1: Mix graphite powder with sodium nitrate and sulfuric acid solution, dissolve the powder, add potassium permanganate, heat and stir, add ultrapure water and continue stirring to form mixture a;

[0037] A2: Add hydrogen peroxide solution to mixture a, let it stand to precipitate, filter, wash the precipitate with deionized water, and freeze-dry to obtain the initial adsorbent;

[0038] A3: The initial adsorbent is dispersed in deionized water, nitrogen gas is introduced, then ferrous chloride tetrahydrate is added and stirred to mix, ammonia water is added and stirring is continued, the mixture is filtered and separated, the solid is washed with deionized water and freeze-dried to obtain the adsorbent.

[0039] In step A1, the total mass of graphite powder, sodium nitrate, and potassium permanganate is 4:20 g / mL in solid-liquid ratio to the sulfuric acid solution. The mass ratio of graphite powder, sodium nitrate, and potassium permanganate is 1:1.5:3. The mass fraction of the sulfuric acid solution is 90%. The heating temperature is 60°C. The amount of ultrapure water added accounts for 70% of the volume of the mixture a.

[0040] In step A2, the volume ratio of mixture a to hydrogen peroxide solution is 100:0.5, the mass fraction of hydrogen peroxide solution is 20%, the standing time is 3 hours, and the freeze-drying temperature and time are -2℃ and 24 hours, respectively.

[0041] In step A3, the mass ratio of the primary adsorbent, deionized water, ferrous chloride tetrahydrate, and ammonia is 2.5:5:10:1.5, with the ammonia having a mass fraction of 25%. The freeze-drying temperature and time are -2℃ and 24h, respectively.

[0042] In step (2), the adsorbent accounts for 20% of the mass of wastewater a, the ultrasonic time is 120 min, and in step (3), the amount of sodium hydroxide and sodium carbonate added accounts for 2% and 8% of the mass of wastewater a, respectively.

[0043] The titanium-silicon molecular sieve was purchased from WONDER-1941-30-6, and the graphite powder was purchased from Mingrun Chenyue.

[0044] Example 2

[0045] A method for treating wastewater during the preparation of oxidized starch, the method comprising the following steps:

[0046] (1) Place the wastewater in two containers, then add the catalyst to each container and simultaneously introduce ozone. Connect the two sides of the containers with pipes and turn on the submersible pump to circulate the wastewater between the two containers.

[0047] (2) Then add an adsorbent and ultrasonically treat at room temperature to form wastewater a;

[0048] (3) Add sodium hydroxide and sodium carbonate to wastewater a, stir and mix, let stand and filter, and discharge the filtrate.

[0049] In step (1), the solid-liquid ratio of the catalyst to the wastewater is 10:3 g / L, and the circulation time is 15 min.

[0050] The catalyst preparation method in step (1) is as follows: the titanium silicon molecular sieve is washed with deionized water, dried in an oven, taken out and immersed in a nitrate mixed solution and shaken, then filtered, and the solid is calcined to obtain the catalyst.

[0051] The drying temperature and time are 65℃ and 1.5h, respectively. The solid-liquid ratio of the titanium-silicon molecular sieve and the nitrate mixed solution is 1.5:10g / mL. The nitrate mixed solution is composed of manganese nitrate solution, ferric nitrate solution and cerium nitrate solution in a volume ratio of 1:1:1. The mass fractions of the manganese nitrate solution, ferric nitrate solution and cerium nitrate solution are 1.2%, 1% and 1.8%, respectively.

[0052] The oscillation time and speed are 9h and 180r / min, respectively, and the calcination temperature and time are 550℃ and 3.5h, respectively.

[0053] The preparation method of the adsorbent in step (2) includes the following steps:

[0054] A1: Mix graphite powder with sodium nitrate and sulfuric acid solution, dissolve the powder, add potassium permanganate, heat and stir, add ultrapure water and continue stirring to form mixture a;

[0055] A2: Add hydrogen peroxide solution to mixture a, let it stand to precipitate, filter, wash the precipitate with deionized water, and freeze-dry to obtain the initial adsorbent;

[0056] A3: The initial adsorbent is dispersed in deionized water, nitrogen gas is introduced, then ferrous chloride tetrahydrate is added and stirred to mix, ammonia water is added and stirring is continued, the mixture is filtered and separated, the solid is washed with deionized water and freeze-dried to obtain the adsorbent.

[0057] In step A1, the total mass of graphite powder, sodium nitrate, and potassium permanganate is 4.5:23 g / mL in solid-liquid ratio to the sulfuric acid solution. The mass ratio of graphite powder, sodium nitrate, and potassium permanganate is 1:1.5:3. The mass fraction of the sulfuric acid solution is 92%. The heating temperature is 70°C. The amount of ultrapure water added accounts for 75% of the volume of the mixture a.

[0058] In step A2, the volume ratio of mixture a to hydrogen peroxide solution is 100:0.55, the mass fraction of hydrogen peroxide solution is 25%, the standing time is 3.5 h, and the freeze-drying temperature and time are -4 °C and 24 h, respectively.

[0059] In step A3, the mass ratio of the primary adsorbent, deionized water, ferrous chloride tetrahydrate, and ammonia is 2.5:5:10:1.5, with the ammonia having a mass fraction of 25%. The freeze-drying temperature and time are -4°C and 24 hours, respectively.

[0060] In step (2), the adsorbent accounts for 25% of the mass of wastewater a, the ultrasonic time is 150 min, and in step (3), the amount of sodium hydroxide and sodium carbonate added accounts for 2.5% and 9% of the mass of wastewater a, respectively.

[0061] The titanium-silicon molecular sieve was purchased from WONDER-1941-30-6, and the graphite powder was purchased from Mingrun Chenyue.

[0062] Example 3

[0063] A method for treating wastewater during the preparation of oxidized starch, the method comprising the following steps:

[0064] (1) Place the wastewater in two containers, then add the catalyst to each container and simultaneously introduce ozone. Connect the two sides of the containers with pipes and turn on the submersible pump to circulate the wastewater between the two containers.

[0065] (2) Then add an adsorbent and ultrasonically treat at room temperature to form wastewater a;

[0066] (3) Add sodium hydroxide and sodium carbonate to wastewater a, stir and mix, let stand and filter, and discharge the filtrate.

[0067] In step (1), the solid-liquid ratio of the catalyst to the wastewater is 10:5 g / L, and the circulation time is 20 min.

[0068] The catalyst preparation method in step (1) is as follows: the titanium silicon molecular sieve is washed with deionized water, dried in an oven, taken out and immersed in a nitrate mixed solution and shaken, then filtered, and the solid is calcined to obtain the catalyst.

[0069] The drying temperature and time are 70℃ and 2h, respectively. The solid-liquid ratio of the titanium-silicon molecular sieve and the nitrate mixed solution is 2:10 g / mL. The nitrate mixed solution is composed of manganese nitrate solution, ferric nitrate solution and cerium nitrate solution in a volume ratio of 1:1:1. The mass fractions of the manganese nitrate solution, ferric nitrate solution and cerium nitrate solution are 1.5%, 1% and 2%, respectively.

[0070] The oscillation time and speed are 10h and 180r / min, respectively, and the calcination temperature and time are 600℃ and 4h, respectively.

[0071] The preparation method of the adsorbent in step (2) includes the following steps:

[0072] A1: Mix graphite powder with sodium nitrate and sulfuric acid solution, dissolve the powder, add potassium permanganate, heat and stir, add ultrapure water and continue stirring to form mixture a;

[0073] A2: Add hydrogen peroxide solution to mixture a, let it stand to precipitate, filter, wash the precipitate with deionized water, and freeze-dry to obtain the initial adsorbent;

[0074] A3: The initial adsorbent is dispersed in deionized water, nitrogen gas is introduced, then ferrous chloride tetrahydrate is added and stirred to mix, ammonia water is added and stirring is continued, the mixture is filtered and separated, the solid is washed with deionized water and freeze-dried to obtain the adsorbent.

[0075] In step A1, the total mass of graphite powder, sodium nitrate, and potassium permanganate is in a solid-liquid ratio of 5:26 g / mL to the sulfuric acid solution. The mass ratio of graphite powder, sodium nitrate, and potassium permanganate is 1:1.5:3. The mass fraction of the sulfuric acid solution is 95%. The heating temperature is 80°C. The amount of ultrapure water added accounts for 80% of the volume of the mixture a.

[0076] In step A2, the volume ratio of mixture a to hydrogen peroxide solution is 100:0.6, the mass fraction of hydrogen peroxide solution is 30%, the standing time is 4 hours, and the freeze-drying temperature and time are -6℃ and 24 hours, respectively.

[0077] In step A3, the mass ratio of the primary adsorbent, deionized water, ferrous chloride tetrahydrate, and ammonia is 2.5:5:10:1.5, with the ammonia having a mass fraction of 25%. The freeze-drying temperature and time are -6°C and 24 hours, respectively.

[0078] In step (2), the adsorbent accounts for 30% of the mass of wastewater a, the ultrasonic time is 180 min, and in step (3), the amount of sodium hydroxide and sodium carbonate added accounts for 3% and 10% of the mass of wastewater a, respectively.

[0079] The titanium-silicon molecular sieve was purchased from WONDER-1941-30-6, and the graphite powder was purchased from Mingrun Chenyue.

[0080] Comparative Example 1

[0081] Based on Example 2, no catalyst is added in step (1) of the wastewater treatment method, and other conditions are the same as in Example 2.

[0082] Comparative Example 2

[0083] Based on Example 2, step (2) of the wastewater treatment method is removed, while other conditions remain the same as in Example 2.

[0084] Comparative Example 3

[0085] Based on Example 2, the sodium carbonate in step (3) of the wastewater treatment method was replaced with an equal mass of sodium hydroxide, and other conditions were the same as in Example 2.

[0086] Comparative Example 4

[0087] Based on Example 2, the sodium hydroxide in step (3) of the wastewater treatment method was replaced with an equal mass of sodium carbonate, and other conditions were the same as in Example 2.

[0088] Performance testing

[0089] 1. COD was detected in the wastewater and the water source of Examples 1-3 and Comparative Examples 1-4 according to the "Dilution ratio method" in the fourth edition of "Methods for Monitoring and Analysis of Water and Wastewater", and the COD removal rate was obtained.

[0090] The test results are shown in Table 1.

[0091] Table 1 Test Results

[0092]

[0093]

[0094] Analysis of the data in Table 1 shows that the COD removal rates of Examples 1-3 are greater than those of Comparative Examples 1-3, and the COD removal rates of all examples are greater than 95%. In Comparative Example 1, the absence of a catalyst reduces free radicals in the wastewater, thus decreasing the degree of oxidative degradation of organic matter. In Comparative Example 2, the lack of an adsorbent results in insignificant removal of sulfides, leading to a lower COD removal rate. In Comparative Example 3, only sodium hydroxide is added, which can react with iron salts to form ferric hydroxide precipitate. However, due to the increased solubility of sodium hydroxide, it further reacts with sulfur elements that have not yet been adsorbed, further reducing the COD removal rate. In Comparative Example 4, the absence of sodium hydroxide significantly reduces the binding of sodium carbonate with iron ions, resulting in less precipitate formation and thus a lower COD removal rate.

[0095] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for treating wastewater during the preparation of oxidized starch, characterized in that, The wastewater treatment method during the preparation of oxidized starch includes the following steps: (1) Place the wastewater in two containers, then add the catalyst to each container and simultaneously introduce ozone. Connect the two sides of the containers with pipes and turn on the submersible pump to circulate the wastewater between the two containers. (2) Then add an adsorbent and ultrasonically treat at room temperature to form wastewater a; (3) Add sodium hydroxide and sodium carbonate to wastewater a, stir and mix, let stand and filter, and discharge the filtrate. The preparation method of the adsorbent in step (2) includes the following steps: A1: Mix graphite powder with sodium nitrate and sulfuric acid solution, dissolve the powder, add potassium permanganate, heat and stir, add ultrapure water and continue stirring to form mixture a; A2: Add hydrogen peroxide solution to mixture a, let it stand to precipitate, filter, wash the precipitate with deionized water, and freeze-dry to obtain the initial adsorbent; A3: The initial adsorbent is dispersed in deionized water, nitrogen gas is introduced, then ferrous chloride tetrahydrate is added and stirred to mix, ammonia water is added and stirring is continued, the mixture is filtered and separated, the solid is washed with deionized water and freeze-dried to obtain the adsorbent; The catalyst preparation method in step (1) is as follows: the titanium silicon molecular sieve is washed with deionized water, dried in an oven, taken out and immersed in a nitrate mixed solution and shaken, then filtered, and the solid is calcined to obtain the catalyst; wherein, the nitrate mixed solution is composed of manganese nitrate solution, iron nitrate solution and cerium nitrate solution in a volume ratio of 1:1:

1.

2. The wastewater treatment method in the preparation of oxidized starch according to claim 1, characterized in that, In step (1), the solid-liquid ratio of the catalyst to the wastewater is 10:1-5 g / L, and the circulation time is 10-20 min.

3. The wastewater treatment method in the preparation of oxidized starch according to claim 1, characterized in that, The drying temperature and time are 60-70℃ and 1-2h, respectively. The solid-liquid ratio of the titanium-silicon molecular sieve and nitrate mixed solution is 1-2:10g / mL. The mass fractions of the manganese nitrate solution, ferric nitrate solution and cerium nitrate solution are 1-1.5%, 1%, and 1.5-2%, respectively.

4. The wastewater treatment method in the preparation of oxidized starch according to claim 1, characterized in that, The oscillation time and speed are 8-10h and 180 r / min, respectively, and the calcination temperature and time are 500-600℃ and 3-4h, respectively.

5. The wastewater treatment method in the preparation of oxidized starch according to claim 1, characterized in that, In step A1, the total mass of graphite powder, sodium nitrate, and potassium permanganate is in a solid-liquid ratio of 4-5:20-26 g / mL to the sulfuric acid solution. The mass ratio of graphite powder, sodium nitrate, and potassium permanganate is 1:1.5:

3. The mass fraction of the sulfuric acid solution is 90-95%. The heating temperature is 60-80℃. The amount of ultrapure water added accounts for 70-80% of the volume of the mixed solution a.

6. The wastewater treatment method in the preparation of oxidized starch according to claim 1, characterized in that, In step A2, the volume ratio of the mixture a to the hydrogen peroxide solution is 100:0.5-0.6, the mass fraction of the hydrogen peroxide solution is 20-30%, the standing time is 3-4 hours, and the freeze-drying temperature and time are -2~-6℃ and 24 hours, respectively.

7. The wastewater treatment method in the preparation of oxidized starch according to claim 1, characterized in that, In step A3, the mass ratio of the primary adsorbent, deionized water, ferrous chloride tetrahydrate, and ammonia is 2.5:5:10:1.5, with the ammonia having a mass fraction of 25%. The freeze-drying temperature and time are -2 to -6°C and 24 hours, respectively.

8. The wastewater treatment method in the preparation of oxidized starch according to claim 1, characterized in that, In step (2), the adsorbent accounts for 20-30% of the mass of wastewater a, the ultrasonic time is 120-180 min, and in step (3), the amount of sodium hydroxide and sodium carbonate added accounts for 2-3% and 8-10% of the mass of wastewater a, respectively.

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