Method for treating pendimethalin wastewater

Abstract

The invention relates to the technical field of pendimethalin wastewater treatment, in particular to a pendimethalin wastewater treatment method which comprises the following steps: step 1, adding ferrous oxide or ferrous hydroxide into wastewater, and adjusting the pH value of the wastewater to be neutral; 2, adjusting the pH value of the primary filtrate to 2-5 by using an inorganic acid, and adding an iron-carbon mixture with the mass ratio of 1: (0.5-2) to carry out an oxidation-reduction reaction; and step 3, introducing the secondary filtrate into 2-5 reaction kettles which are connected in series, and adding hydrogen peroxide for 1-3 times according to the mass ratio of hydrogen peroxide to COD (Chemical Oxygen Demand) of (15-25): 1. According to the pendimethalin wastewater treatment method provided by the invention, the iron-carbon mixture generates a primary battery effect in the solution, nitrate radicals can be quickly reduced into nitrogen oxides or ammonia gas, the nitrate radicals are efficiently and quickly treated, and meanwhile, iron ions and ferrous ions can finally generate corresponding hydroxides to be separated out.

Description

Technical Field

[0001] The present invention relates to the technical field of pendimethalin wastewater treatment, and particularly to a method for treating pendimethalin wastewater. Background Art

[0002] Pendimethalin is a selective herbicide widely used in agricultural production, which can effectively control annual gramineous weeds and broad-leaved weeds. Due to its high herbicidal performance, it is produced and used in large quantities globally. Its production process involves various chemical reactions such as nitrification, reduction, condensation, etc., and a large amount of wastewater will be generated in these production links.

[0003] Pendimethalin wastewater usually contains nitric acid and various organic substances. The mass concentration of nitric acid in the wastewater is usually between 1% and 5%. Direct neutralization of the wastewater with sodium hydroxide will generate sodium nitrate waste salt (which is explosive), and it needs to be entrusted to a third party for treatment, with high treatment costs and high risks. Moreover, different production batches or process adjustments may lead to changes in the nitric acid concentration, types and contents of organic substances, increasing the treatment difficulty. Therefore, we propose a method for treating pendimethalin wastewater to solve the above problems. Summary of the Invention

[0004] The purpose of the present invention is to propose a method for treating pendimethalin wastewater to solve the deficiencies existing in the prior art.

[0005] The method for treating pendimethalin wastewater includes the following steps:

[0006] Step 1, primary pH adjustment and solid-liquid separation: Add ferrous oxide or ferrous hydroxide to the wastewater to adjust the pH of the wastewater to neutral, and obtain a primary filtrate after the first-stage filtration;

[0007] Step 2, micro-electrolysis reaction treatment: Adjust the pH of the primary filtrate to 2-5 with inorganic acid, add an iron-carbon mixture with a mass ratio of 1:0.5-2 for redox reaction. The iron-carbon mixture is a mixture of iron powder and carbon powder. When adding the iron-carbon mixture, the mass of iron is 5%-15% of the mass of the wastewater. Take the termination of bubbles as the reaction end point, and obtain a secondary filtrate after the second-stage filtration;

[0008] Step 3, multi-stage catalytic oxidation: Introduce the secondary filtrate into 2-5 reaction kettles connected in series, add hydrogen peroxide in 1-3 times according to the mass ratio of hydrogen peroxide to COD of 15-25:1, and perform the third-stage filtration and discharge after the reaction in the last reaction kettle.

[0009] Preferably, the volatile gas generated in Step 1 is dried and then connected to a selective catalytic reduction denitration system for treatment.

[0010] Preferably, the particle size of the iron powder is 0.1-0.5 mm, and the particle size of the carbon powder is 0.1-1 mm.

[0011] Preferably, the gas generated in the reaction process of step 2 is absorbed by deionized water, then dried, and finally connected to a selective catalytic reduction denitration system for treatment.

[0012] Preferably, the inorganic acid is a hydrochloric acid or sulfuric acid solution with a mass concentration of 10%-30%, and the dosage is dynamically controlled by an on-line pH monitoring system.

[0013] Preferably, in step 3, hydrogen peroxide is added in a gradient mode, a reaction residence time of 30-60 minutes is set between adjacent reaction kettles, and an ORP on-line monitor is set at the outlet of the last reaction kettle to control the reaction end point.

[0014] Preferably, in step 3, the dosage of hydrogen peroxide in the first reaction kettle is greater than 50% of the total dosage.

[0015] Preferably, the filter devices used for the first-stage filtration, second-stage filtration and third-stage filtration are plate-and-frame filter presses, and the filter residues in step 1 and step 3 are transported to solid waste treatment equipment for centralized treatment.

[0016] Preferably, the iron-carbon mixture in step 2 can be recycled at least 3 batches after replenishing fresh iron powder, and the iron-carbon mass ratio is maintained at 1:0.5-2 during recycling.

[0017] Preferably, the filter residue in step 2 is dried and crushed, the iron powder is removed by magnetism and then weighed. When the mass of the carbon powder is less than 30% of the mass of the remaining filter residue, the filter residue is transported to solid waste treatment equipment for treatment.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. For the pendimethalin wastewater treatment method proposed by the present invention, the pH of the wastewater is first adjusted to neutral by ferrous oxide or ferrous hydroxide, and part of the solid waste (calcium, magnesium ions, etc.) can be precipitated, avoiding the mixing of these solid wastes into the iron-carbon mixture in step 2. When the solid waste deposits on the surface of the carbon powder, it will cause the premature inactivation of the carbon powder and affect the recycling times of the iron-carbon mixture. Through the treatment of step 1, the generation amount of solid waste can be effectively reduced. At the same time, during the use of ferrous oxide or ferrous hydroxide, a small amount of nitrate can be reduced, and the iron ions generated by adjusting the pH can be easily removed in the subsequent step 2 (no new impurities are introduced).

[0020] 2. In the method for treating pendimethalin wastewater proposed by the present invention, in step 2, a primary battery effect is generated in the solution by the iron-carbon mixture, with iron as the negative electrode and carbon as the positive electrode, which can quickly reduce nitrate to nitrogen oxides or ammonia, efficiently and rapidly treat nitrate, and at the same time, iron ions and ferrous ions can finally form corresponding hydroxides and precipitate out; in step 2, the pH of the primary filtrate is adjusted to weakly acidic with inorganic acid. On the one hand, it can improve the reaction rate of step 2, and on the other hand, when the iron-carbon mixture is recycled, it can remove the iron hydroxide attached to the surface of the carbon powder to ensure that the carbon powder can smoothly participate in the reaction.

[0021] 3. In the method for treating pendimethalin wastewater proposed by the present invention, the organic matter in the wastewater is subjected to multi-stage catalytic oxidation by hydrogen peroxide, which can effectively reduce the COD of the wastewater, reduce the usage amount of hydrogen peroxide at the same time, and improve the treatment efficiency. Detailed implementation mode

[0022] The present invention will be further explained below with reference to specific embodiments.

[0023] The method for treating pendimethalin wastewater includes the following steps:

[0024] Step 1, primary pH adjustment and solid-liquid separation: Ferrous oxide or ferrous hydroxide is added to the wastewater to adjust the pH of the wastewater to neutral, and the primary filtrate is obtained after the first-stage filtration.

[0025] Step 2, micro-electrolysis reaction treatment: The pH of the primary filtrate is adjusted to 2-5 with inorganic acid, and an iron-carbon mixture with a mass ratio of 1:0.5-2 is added for redox reaction. The iron-carbon mixture is a mixture of iron powder and carbon powder. When adding the iron-carbon mixture, the mass of iron is 5%-15% of the mass of the wastewater. The reaction ends with the termination of bubbles, and the secondary filtrate is obtained after the second-stage filtration.

[0026] Step 3, multi-stage catalytic oxidation: The secondary filtrate is introduced into 2-5 series-connected reaction kettles, and hydrogen peroxide is added in 1-3 times according to the mass ratio of hydrogen peroxide to COD of 15-25:1. After the reaction in the last reaction kettle, it is filtered for the third time and discharged.

[0027] The volatile gas generated in step 1 is dried and then connected to a selective catalytic reduction denitration system for treatment.

[0028] The particle size of the iron powder is 0.1-0.5 mm, and the particle size of the carbon powder is 0.1-1 mm.

[0029] The gas generated during the reaction in step 2 is absorbed by deionized water, then dried, and finally connected to a selective catalytic reduction denitration system for treatment.

[0030] The inorganic acid is hydrochloric acid or sulfuric acid solution with a mass concentration of 10-30%, and the dosage is dynamically controlled by the pH on-line monitoring system.

[0031] In step 3, hydrogen peroxide is added in a gradient mode, a reaction residence time of 30-60 minutes is set between adjacent reaction kettles, and an ORP on-line monitor is set at the outlet of the last reaction kettle to control the reaction end point.

[0032] In step 3, the dosage of hydrogen peroxide in the first reaction kettle is greater than 50% of the total dosage.

[0033] The filtering devices used in the first-stage filtration, second-stage filtration and third-stage filtration are plate-and-frame filter presses, and the filter residues in steps 1 and 3 are transported to the solid waste treatment equipment for centralized treatment.

[0034] The iron-carbon mixture described in step 2 can be recycled for at least 3 batches after replenishing fresh iron powder, and the iron-carbon mass ratio is maintained at 1:0.5-2 during recycling.

[0035] The filter residue in step 2 is dried and crushed, the iron powder is removed by magnetism and then weighed. When the mass of the carbon powder is less than 30% of the mass of the remaining filter residue, the filter residue is transported to the solid waste treatment equipment for treatment.

[0036] The main reaction principle in step 1 is as follows:

[0037] 3Fe 2+ +NO3 - +4H + =3Fe 3+ +NO↑+2H2O

[0038] The main reaction principle in step 2 is as follows:

[0039] 1) When the wastewater is acidic

[0040] 3Fe + 8HNO3 (dilute) = 3Fe(NO3)2 + 2NO↑ + 4H2O;

[0041] 2) When the wastewater is neutral

[0042] 4Fe + NO s - + 6H2O = 4Fe(OH)2 + NH3↑

[0043] The technical solution of the present invention will be further described below through specific embodiments.

[0044] Example 1: Using the pendimethalin wastewater from a pesticide factory as the water to be treated, the initial pH is 0.4, the initial COD is 16721 mg / L, and the treatment volume is 2 m 3 , and the specific treatment steps are as follows:

[0045] Step 1, Primary pH adjustment and solid-liquid separation: Add ferrous oxide to the wastewater to adjust the pH of the wastewater to neutral, and obtain a primary filtrate after the first-stage filtration;

[0046] Step 2, Micro-electrolysis reaction treatment: Adjust the pH of the primary filtrate to 5 with hydrochloric acid with a mass concentration of 10%. Add an iron-carbon mixture, where the mass of iron powder is 200 kg and the mass of carbon powder is 100 kg, and the iron-carbon mass ratio is 1:0.5. Conduct an oxidation-reduction reaction, and take the termination of bubbles as the reaction end point. Obtain a secondary filtrate after the second-stage filtration;

[0047] Step 3, Multi-stage catalytic oxidation: Introduce the secondary filtrate into 2 series-connected reaction kettles, add 502 kg of hydrogen peroxide, add the hydrogen peroxide in 1 portion. After the reaction in the last reaction kettle, conduct the third-stage filtration and discharge. The residence time of each reaction kettle is 30 minutes.

[0048] Example 2: Use the pendimethalin wastewater from a certain pesticide factory as the water to be treated, with an initial pH of 0.4 and an initial COD of 16721 mg / L, and a treatment volume of 2 m 3 , and the specific treatment steps are as follows:

[0049] Step 1, Primary pH adjustment and solid-liquid separation: Add ferrous hydroxide to the wastewater to adjust the pH of the wastewater to neutral, and obtain a primary filtrate after the first-stage filtration;

[0050] Step 2, Micro-electrolysis reaction treatment: Adjust the pH of the primary filtrate to 2 with hydrochloric acid with a mass concentration of 30%. Add an iron-carbon mixture, where the mass of iron powder is 300 kg and the mass of carbon powder is 400 kg, and the iron-carbon mass ratio is 1:2. Conduct an oxidation-reduction reaction, and take the termination of bubbles as the reaction end point. Obtain a secondary filtrate after the second-stage filtration;

[0051] Step 3, Multi-stage catalytic oxidation: Introduce the secondary filtrate into 5 series-connected reaction kettles, add 836 kg of hydrogen peroxide, add the hydrogen peroxide in 3 portions. The input amount in the first reaction kettle is 436 kg, the input amount in the second reaction kettle is 260 kg, and the input amount in the third reaction kettle is 140 kg. After the reaction in the last reaction kettle, conduct the third-stage filtration and discharge. The residence time of each reaction kettle is 60 minutes.

[0052] Example 3: Use the pendimethalin wastewater from a certain pesticide factory as the water to be treated, with an initial pH of 0.4 and an initial COD of 16721 mg / L, and a treatment volume of 2 m 3 , and the specific treatment steps are as follows:

[0053] Step 1, Primary pH adjustment and solid-liquid separation: Add ferrous hydroxide to the wastewater to adjust the pH of the wastewater to neutral, and obtain a primary filtrate after the first-stage filtration;

[0054] Step 2, Micro-electrolysis Reaction Treatment: Adjust the pH of the primary filtrate to 2 with sulfuric acid of 30% mass concentration, add an iron-carbon mixture, where the mass of iron powder is 200 kg and the mass of carbon powder is 200 kg, with an iron-carbon mass ratio of 1:1, conduct an oxidation-reduction reaction, and take the termination of bubbles as the reaction end point, and obtain a secondary filtrate through secondary filtration;

[0055] Step 3, Multi-stage Catalytic Oxidation: Introduce the secondary filtrate into 3 series-connected reaction kettles, add 669 kg of hydrogen peroxide, add hydrogen peroxide in 2 batches, the input amount in the first reaction kettle is 469 kg, and the input amount in the second reaction kettle is 200 kg. After passing through the last reaction kettle, conduct tertiary filtration and discharge. The residence time of each reaction kettle is 45 minutes.

[0056] Example 4: Use the pendimethalin wastewater from a certain pesticide factory as the water to be treated, with an initial pH of 0.4 and an initial COD of 16721 mg / L, and a treatment volume of 2 m 3 , and the specific treatment steps are as follows:

[0057] Step 1, Primary pH Adjustment and Solid-Liquid Separation: Add ferrous hydroxide to the wastewater to adjust the pH of the wastewater to neutral, and obtain a primary filtrate through primary filtration;

[0058] Step 2, Micro-electrolysis Reaction Treatment: Adjust the pH of the primary filtrate to 2 with sulfuric acid of 30% mass concentration, add an iron-carbon mixture, and the iron-carbon mixture is obtained by supplementing fresh iron powder to the iron-carbon mixture in Example 3. Among them, the mass of iron powder is 200 kg, and the total mass of carbon powder and the substances adhered to the carbon powder is 296 kg. Conduct an oxidation-reduction reaction, and take the termination of bubbles as the reaction end point, and obtain a secondary filtrate through secondary filtration;

[0059] Step 3, Multi-stage Catalytic Oxidation: Introduce the secondary filtrate into 3 series-connected reaction kettles, add 669 kg of hydrogen peroxide, add hydrogen peroxide in 2 batches, the input amount in the first reaction kettle is 469 kg, and the input amount in the second reaction kettle is 200 kg. After passing through the last reaction kettle, conduct tertiary filtration and discharge. The residence time of each reaction kettle is 45 minutes.

[0060] Example 5: Use the pendimethalin wastewater from a certain pesticide factory as the water to be treated, with an initial pH of 0.1 and an initial COD of 13436 mg / L, and a treatment volume of 2 m 3 , and the specific treatment steps are as follows:

[0061] Step 1, Primary pH Adjustment and Solid-Liquid Separation: Add ferrous hydroxide to the wastewater to adjust the pH of the wastewater to neutral, and obtain a primary filtrate through primary filtration;

[0062] Step 2, Micro-electrolysis Reaction Treatment: Adjust the pH of the primary filtrate to 2 with sulfuric acid at a mass concentration of 30%, add an iron-carbon mixture, where the mass of iron powder is 100 kg and the mass of carbon powder is 100 kg, and the iron-carbon mass ratio is 1:1. Conduct an oxidation-reduction reaction, and take the termination of bubbles as the reaction end point. Obtain the secondary filtrate through secondary filtration;

[0063] Step 3, Multi-stage Catalytic Oxidation: Introduce the secondary filtrate into 3 series-connected reaction kettles, add 537 kg of hydrogen peroxide, and add hydrogen peroxide in 2 batches. The input amount in the first reaction kettle is 387 kg, and the input amount in the second reaction kettle is 150 kg. After passing through the last reaction kettle, conduct tertiary filtration and discharge. The residence time in each reaction kettle is 45 minutes.

[0064]

[0065] As described above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A method for treating pendimethalin wastewater, characterized in that, It includes the following steps: Step 1, primary pH adjustment and solid-liquid separation: Add ferrous oxide or ferrous hydroxide to the wastewater to adjust the pH of the wastewater to neutral, and obtain a primary filtrate after the first-stage filtration; Step 2, micro-electrolysis reaction treatment: Adjust the pH of the primary filtrate to 2-5 with an inorganic acid, add an iron-carbon mixture with a mass ratio of 1:0.5-2 for redox reaction. The iron-carbon mixture is a mixture of iron powder and carbon powder. When adding the iron-carbon mixture, the mass of iron is 5%-15% of the mass of the wastewater. Take the termination of bubbles as the reaction end point, and obtain a secondary filtrate after the second-stage filtration; Step 3, multi-stage catalytic oxidation: Introduce the secondary filtrate into 2-5 reaction kettles connected in series, add hydrogen peroxide in 1-3 times according to the mass ratio of hydrogen peroxide to COD of 15-25:1, and perform the third-stage filtration and discharge after the reaction in the last reaction kettle.

2. The pendimethalin wastewater treatment method according to claim 1, characterized in that, The volatile gas generated in Step 1 is dried and then connected to a selective catalytic reduction denitration system for treatment.

3. The pendimethalin wastewater treatment method according to claim 1, characterized in that The particle size of the iron powder is 0.1-0.5 mm, and the particle size of the carbon powder is 0.1-1 mm.

4. The pendimethalin wastewater treatment method according to claim 1, characterized in that, The gas generated during the reaction in Step 2 is absorbed by deionized water, then dried, and finally connected to a selective catalytic reduction denitration system for treatment.

5. The method for treating pendimethalin wastewater according to claim 1, wherein The inorganic acid is a hydrochloric acid or sulfuric acid solution with a mass concentration of 10%-30%, and the dosage is dynamically controlled by a pH on-line monitoring system.

6. The method for treating pendimethalin wastewater according to claim 1, wherein In Step 3, hydrogen peroxide is added in a gradient mode, a reaction residence time of 30-60 minutes is set between adjacent reaction kettles, and an ORP on-line monitor is set at the outlet of the last reaction kettle to control the reaction end point.

7. The method for treating pendimethalin wastewater according to claim 6, wherein In Step 3, the dosage of hydrogen peroxide in the first reaction kettle is greater than 50% of the total dosage.

8. The method for treating pendimethalin wastewater according to claim 1, wherein The filtration devices used for the first-stage filtration, second-stage filtration and third-stage filtration are plate-and-frame filter presses, and the filter residues in Step 1 and Step 3 are transported to solid waste treatment equipment for centralized treatment.

9. The method for treating pendimethalin wastewater according to claim 8, characterized in that, The iron-carbon mixture described in Step 2 can be recycled at least 3 batches after replenishing fresh iron powder, and the iron-carbon mass ratio is maintained at 1:0.5-2 during recycling.

10. The method for treating pendimethalin wastewater according to claim 9, characterized in that, The filter residue in Step 2 is dried and crushed, the iron powder is removed by magnetism and then weighed. When the mass of the carbon powder is less than 30% of the mass of the remaining filter residue, the filter residue is transported to solid waste treatment equipment for treatment.

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