High-hardness industrial wastewater treatment process

Abstract

The application relates to a high-hardness industrial wastewater treatment process, which sequentially passes industrial wastewater into a sedimentation tank, an adjusting tank and a flocculation tank, adds a flocculating agent and a scale inhibitor into the flocculation tank, then removes flocculation substances through two-stage multi-medium filters to flow into an ultrafiltration effluent tank; a RO security filter, a reverse osmosis concentration system and finally recycled effluent; wherein the scale inhibitor is a composite corrosion and scale inhibition water treatment agent, which is obtained by in-situ copolymerization of phosphonocarboxylic acid copolymer after modification of nitrogen-doped carbon quantum dots on the surface of attapulgite as a carrier. The application has the beneficial effects that the treatment process has good treatment effect on high-hardness industrial wastewater, can effectively remove complex components such as organic pollutants and heavy metal ions in the water body, reduce the probability of equipment scaling, reduce the cleaning frequency of the equipment, prolong the service life of the key equipment, improve the system operation stability and water quality stability.

Description

Technical Field

[0001] This invention relates to the field of mixed-in protection technology, specifically a process for treating high-hardness industrial wastewater. Background Technology

[0002] A complete industrial wastewater treatment system includes equalization tanks, flocculation tanks, coagulation tanks, micro-electrolysis reactors, biological reactors, and so on. These water treatment tanks are designed to filter, degrade, and adsorb suspended solids, organic pollutants, and heavy metal ions in the water to achieve removal. However, some specific industrial wastewaters are characterized by high hardness and high alkalinity. During treatment processes such as evaporation, membrane separation, pipeline transportation, and sedimentation, calcium carbonate, calcium sulfate, and other deposits can easily form on the equipment surface, shortening equipment lifespan and increasing cleaning frequency and maintenance costs. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method that can effectively reduce scaling in equipment during the treatment of high-hardness industrial wastewater, thereby improving treatment efficiency, extending equipment lifespan, and reducing operating costs.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A process for treating high-hardness industrial wastewater includes the following steps: 1) The industrial wastewater is fed into a sedimentation tank to filter out large suspended solids, and the effluent is fed into an equalization tank where limestone and sodium hydroxide are added to make the pH of the effluent range from 10 to 11. 2) The wastewater in the equalization tank is transported to the flocculation tank by the booster pump. Flocculant and scale inhibitor are added to the flocculation tank. The stirring device is turned on and stirred quickly for 30-60 minutes. During the rapid stirring, the outlet is opened to allow the water to flow into the transfer tank. Acidic substances are pumped in to make the pH weakly alkaline. After passing through two-stage multi-media filters to remove flocculants, the water flows into the ultrafiltration effluent tank. 3) After ultrafiltration, the water enters the clear water tank under the action of the booster pump. Sodium hydroxide or hydrochloric acid is added to the clear water tank to adjust the pH to 7-8. After adding scale inhibitor, it is pumped into the two-stage RO security filter. The purified water enters the reverse osmosis primary concentration system for concentration. After adding scale inhibitor, the concentrated water is pumped into the tertiary RO security filter and enters the reverse osmosis secondary concentration system. The final effluent is recycled. The scale inhibitor is a composite corrosion and scale inhibitor water treatment agent, obtained by in-situ copolymerization of attapulgite as a carrier, after modifying its surface with nitrogen-doped carbon quantum dots; wherein... The nitrogen-doped carbon quantum dots are prepared as follows: glucose, itaconic acid, and benzotriazole are added to a 50% ethanol aqueous solution and stirred evenly to obtain mixture A. ZnCl2·H2O and ethylenediamine are added to deionized water and stirred evenly to obtain mixture B. Mixture A is heated and stirred. Mixture B is added to mixture A while stirring. Then, the mixture is transferred to a high-pressure reactor for hydrothermal reaction. After cooling, it is dialyzed and dried to obtain the final product. The monomers of the phosphonocarboxylic acid copolymer include maleic acid, 2-acrylamide-2-methylpropanesulfonic acid, and N-substituted hydroxyethylidene diphosphonate-maleimide, in a molar ratio of 5~10:2~4:1.

[0005] Further, in step 2), the amount of flocculant and scale inhibitor added is 50~100 mg / L and 5~10 mg / L, respectively; in step 3), the amount of scale inhibitor added is 30~50 mg / L.

[0006] Furthermore, the preparation method of the composite corrosion and scale inhibitor water treatment agent is as follows: S1. Add 3-aminopropyltriethoxysilane and anhydrous ethanol to a reaction flask to obtain a mixed solution. Adjust the pH to acidic. Disperse the activated attapulgite in the mixed solution by ultrasound. Heat to 60°C and react with ultrasound for 3 hours. Filter. Wash the product three times with water and ethanol. Dry to obtain modified attapulgite. S2. The modified attapulgite and nitrogen-doped carbon quantum dots are evenly dispersed in deionized water. Nitrogen gas is introduced into the aqueous solution of the modified attapulgite to remove air, and the temperature is raised to 50~60℃. Then, the aqueous solution of nitrogen-doped carbon quantum dots is added while stirring, and the mixture is sonicated for 30 min. S3. Add the initiator to the reaction system in step S2 and stir until homogeneous. Heat to 60-70°C and maintain a nitrogen atmosphere. Mix maleic acid, 2-acrylamide-2-methylpropanesulfonic acid, and N-substituted hydroxyethylidene diphosphonate-maleimide in the molar ratio and add dropwise to the reaction system. After the addition is complete, heat to 80-90°C and react for 4-6 hours. After cooling, filter and dry to obtain the final product.

[0007] Furthermore, in the preparation process of the nitrogen-doped carbon quantum dots, the mass ratio of glucose, itaconic acid, and benzotriazole is 10:1~2:2~5; and the mass ratio of ZnCl2·H2O and ethylenediamine is 1~1.5:1.

[0008] Furthermore, in the preparation process of the nitrogen-doped carbon quantum dots, the hydrothermal reaction temperature is 180~200℃ and the reaction time is 8~12h.

[0009] Furthermore, the N-substituted hydroxyethylidene diphosphonate-maleimide has the following structural formula: It is prepared by reacting maleimide with hydroxyethylidene diphosphonic acid in K2CO3 / DMF under DCC / DMAP-assisted esterification.

[0010] Furthermore, the activation process of the activated attapulgite soil is as follows: After grinding and sieving the natural attapulgite, the attapulgite was soaked in a 1M sodium hydroxide solution for 2 hours at a solid-liquid ratio of 1:10 g / mL. After filtration and washing with water, it was soaked in a 3M hydrochloric acid solution, heated in an 80℃ water bath for 4 hours, cooled and filtered, washed with water until neutral, and dried.

[0011] Furthermore, the mass ratio of the modified attapulgite to nitrogen-doped carbon quantum dots is 1:0.3~0.8.

[0012] Compared with the prior art, the beneficial effects of the present invention are: the treatment process of this application has a better treatment effect on industrial wastewater with high hardness. In addition to effectively removing complex components such as organic pollutants and heavy metal ions from the water, it can also reduce the probability of equipment scaling, reduce the number of equipment cleaning times, extend the service life of key equipment, and improve the stability of system operation and the stability of product water quality. Detailed Implementation

[0013] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0015] Example 1: A process for treating high-hardness industrial wastewater 1) The industrial wastewater is fed into a sedimentation tank to filter out large suspended solids, and the effluent is fed into an equalization tank where limestone and sodium hydroxide are added to make the pH of the effluent range from 10 to 11. 2) The wastewater in the equalization tank is transported to the flocculation tank by the booster pump. Flocculant and scale inhibitor are added to the flocculation tank. The stirring device is turned on and stirred quickly for 30-60 minutes. During the rapid stirring, the outlet is opened to allow the water to flow into the transfer tank. Acidic substances are pumped in to make the pH weakly alkaline. After passing through two-stage multi-media filters to remove flocculants, the water flows into the ultrafiltration effluent tank. 3) After ultrafiltration, the water enters the clear water tank under the action of the booster pump. Sodium hydroxide or hydrochloric acid is added to the clear water tank to adjust the pH to 7-8. After adding scale inhibitor, it is pumped into the two-stage RO security filter. The purified water enters the reverse osmosis primary concentration system for concentration. After adding scale inhibitor, the concentrated water is pumped into the tertiary RO security filter and enters the reverse osmosis secondary concentration system. The final effluent is recycled. The scale inhibitor is a composite corrosion and scale inhibitor water treatment agent, and its preparation process is as follows: S1. Activation of attapulgite: Grind and crush natural attapulgite and sieve it. Soak the attapulgite in 1M sodium hydroxide solution for 2 hours at a solid-liquid ratio of 1:10 g / mL. After filtration and washing with water, soak it in 3M hydrochloric acid solution, heat it in a water bath at 80℃ for 4 hours, cool and filter it, wash it with water until neutral, and dry it. Preparation of nitrogen-doped carbon quantum dots: 2 g glucose, 0.2 g itaconic acid, and 0.4 g benzotriazole were added to 10 ml of 50% ethanol aqueous solution and stirred until homogeneous to obtain mixture A. 0.2 g ZnCl2·H2O and 0.2 g ethylenediamine were added to 2 ml of deionized water and stirred until homogeneous to obtain mixture B. Mixture A was heated and stirred, and mixture B was added to mixture A while stirring. The mixture was then transferred to a high-pressure reactor and hydrothermally reacted at 180℃ for 8 h. After cooling, the mixture was dialyzed and dried to obtain the final product. Obtaining the comonomer: Maleic acid, 2-acrylamide-2-methylpropanesulfonic acid, and N-substituted hydroxyethylidene diphosphonate-maleimide were mixed in a molar ratio of 5:2:1, wherein the structural formula of N-substituted hydroxyethylidene diphosphonate-maleimide is: It is prepared by reacting maleimide with hydroxyethylidene diphosphonic acid in K2CO3 / DMF under DCC / DMAP-assisted esterification.

[0016] S2. Add 10g of 3-aminopropyltriethoxysilane and anhydrous ethanol to the reaction flask to obtain a mixed solution. Disperse 2g of activated attapulgite in the mixed solution by ultrasound. Heat to 60℃ and react with ultrasound assistance for 3 hours. Filter, wash the product three times with water and ethanol, and dry to obtain modified attapulgite.

[0017] S3. Disperse 1g of modified attapulgite and 0.3g of nitrogen-doped carbon quantum dots evenly in deionized water. Purge the modified attapulgite aqueous solution with nitrogen to remove air and heat to 50~60℃. Then, while stirring, add the nitrogen-doped carbon quantum dot aqueous solution and continue sonication for 30 min. S4. Add potassium persulfate initiator to the above reaction system and stir until homogeneous. Heat to 60-70℃ and maintain a nitrogen atmosphere. Mix maleic acid, 2-acrylamide-2-methylpropanesulfonic acid, and N-substituted hydroxyethylidene diphosphonate-maleimide in the molar ratio. Add 2g of the monomer mixture dropwise to the reaction system. After the addition is complete, heat to 80-90℃ and react for 4-6 hours. After cooling, filter and dry to obtain the final product.

[0018] The scale inhibitor used in this invention is obtained by in-situ copolymerization of attapulgite as a carrier and nitrogen-doped carbon quantum dots modified on its surface to form a phosphonocarboxylic acid copolymer. Using attapulgite as a carrier, its nanotube structure restricts scale crystal formation. Furthermore, after activation, its specific surface area increases, and its surface has abundant loading sites, which can act as a grafting bridge to load carbon quantum dots on its surface and generate the phosphonocarboxylic acid copolymer in situ, resulting in a synergistic effect. The nitrogen-doped carbon quantum dots have abundant amino, carboxyl, and hydroxyl functional groups on their surface, making it difficult for calcium carbonate microcrystals to aggregate or interfering with normal crystal growth, thereby inhibiting scale formation. The scale-forming crystals exhibit high stability and are coated with zinc ions, enhancing the material's antibacterial properties. When modified onto the surface of attapulgite, they demonstrate excellent adsorption performance and effectively remove organic matter and heavy metals from water. Phosphonyl carboxylic acid copolymers are generated in situ on the attapulgite surface, resulting in good compounding effects. These copolymers contain abundant carboxyl, phosphonyl, amide, sulfonic acid, and heterocyclic structures. The phosphonyl groups are provided by N-substituted hydroxyethylidene diphosphonate-maleimide, forming a dense protective layer on the metal surface, effectively inhibiting corrosion and exhibiting good corrosion inhibition properties. Applying this to water treatment processes for high-hardness industrial wastewater effectively extends the service life of equipment.

[0019] Taking the wastewater discharged from the chemical plant as an example, the COD is 2210 mg / L and the salt content is 8230 mg / L. After treatment by the above system, the COD is ≤15mg / L and the desalination rate is ≥95%.

[0020] The corrosion rates of carbon steel, stainless steel, and copper alloys in the circulating water are all lower than the national standards (carbon steel 0.075 mm / a, stainless steel 0.005 mm / a, copper 0.005 mm / a), and the monthly fouling thermal resistance is <3.44 × 10⁻⁶. -4 m 2 ·K / W.

[0021] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A process for treating high-hardness industrial wastewater, characterized in that, Includes the following steps: 1) The industrial wastewater is fed into a sedimentation tank to filter out large suspended solids, and the effluent is fed into an equalization tank where limestone and sodium hydroxide are added to make the pH of the effluent range from 10 to 11. 2) The wastewater in the equalization tank is transported to the flocculation tank by the booster pump. Flocculant and scale inhibitor are added to the flocculation tank. The stirring device is turned on and stirred quickly for 30-60 minutes. During the rapid stirring, the outlet is opened to allow the water to flow into the transfer tank. Acidic substances are pumped in to make the pH weakly alkaline. After passing through two-stage multi-media filters to remove flocculants, the water flows into the ultrafiltration effluent tank. 3) After ultrafiltration, the water enters the clear water tank under the action of the booster pump. Sodium hydroxide or hydrochloric acid is added to the clear water tank to adjust the pH to 7-8. After adding scale inhibitor, it is pumped into the two-stage RO security filter. The purified water enters the reverse osmosis primary concentration system for concentration. After adding scale inhibitor, the concentrated water is pumped into the tertiary RO security filter and enters the reverse osmosis secondary concentration system. The final effluent is recycled. The scale inhibitor is a composite corrosion and scale inhibitor water treatment agent, obtained by in-situ copolymerization of attapulgite as a carrier, after modifying its surface with nitrogen-doped carbon quantum dots; wherein... The nitrogen-doped carbon quantum dots are prepared as follows: glucose, itaconic acid, and benzotriazole are added to a 50% ethanol aqueous solution and stirred evenly to obtain mixture A. ZnCl2·H2O and ethylenediamine are added to deionized water and stirred evenly to obtain mixture B. Mixture A is heated and stirred. Mixture B is added to mixture A while stirring. Then, the mixture is transferred to a high-pressure reactor for hydrothermal reaction. After cooling, it is dialyzed and dried to obtain the final product. The monomers of the phosphonocarboxylic acid copolymer include: maleic acid, 2-acrylamide-2-methylpropanesulfonic acid, and N-substituted hydroxyethylidene diphosphonate-maleimide, in a molar ratio of 5~10:2~4:1; The N-substituted hydroxyethylidene diphosphonate-maleimide is prepared by reacting maleimide with hydroxyethylidene diphosphonic acid in K2CO3 / DMF under DCC / DMAP-assisted esterification.

2. The high-hardness industrial wastewater treatment process as described in claim 1, characterized in that, In step 2), the amount of flocculant and scale inhibitor added is 50~100 mg / L and 5~10 mg / L, respectively; in step 3), the amount of scale inhibitor added is 30~50 mg / L.

3. The high-hardness industrial wastewater treatment process as described in claim 1, characterized in that, The preparation method of the composite corrosion and scale inhibitor water treatment agent is as follows: S1. Add 3-aminopropyltriethoxysilane and anhydrous ethanol to a reaction flask to obtain a mixed solution. Adjust the pH to acidic. Disperse the activated attapulgite in the mixed solution by ultrasound. Heat to 60°C and react with ultrasound for 3 hours. Filter. Wash the product three times with water and ethanol. Dry to obtain modified attapulgite. S2. The modified attapulgite and nitrogen-doped carbon quantum dots are evenly dispersed in deionized water. Nitrogen gas is introduced into the aqueous solution of the modified attapulgite to remove air, and the temperature is raised to 50~60℃. Then, the aqueous solution of nitrogen-doped carbon quantum dots is added while stirring, and the ultrasonic treatment is continued for 30 min. S3. Add the initiator to the reaction system in step S2 and stir until homogeneous. Heat to 60-70°C and maintain a nitrogen atmosphere. Mix maleic acid, 2-acrylamide-2-methylpropanesulfonic acid, and N-substituted hydroxyethylidene diphosphonate-maleimide in the molar ratio and add dropwise to the reaction system. After the addition is complete, heat to 80-90°C and react for 4-6 hours. After cooling, filter and dry to obtain the final product.

4. The high-hardness industrial wastewater treatment process as described in claim 1, characterized in that, In the preparation process of the nitrogen-doped carbon quantum dots, the mass ratio of glucose, itaconic acid, and benzotriazole is 10:1~2:2~5; the mass ratio of ZnCl2·H2O and ethylenediamine is 1~1.5:

1.

5. The high-hardness industrial wastewater treatment process as described in claim 1, characterized in that, In the preparation process of the nitrogen-doped carbon quantum dots, the hydrothermal reaction temperature is 180~200℃ and the reaction time is 8~12h.

6. The high-hardness industrial wastewater treatment process as described in claim 3, characterized in that, The activation process of the activated attapulgite soil is as follows: After grinding and sieving the natural attapulgite, the attapulgite was soaked in a 1M sodium hydroxide solution for 2 hours at a solid-liquid ratio of 1:10 g / mL. After filtration and washing with water, it was soaked in a 3M hydrochloric acid solution, heated in an 80℃ water bath for 4 hours, cooled and filtered, washed with water until neutral, and dried.

7. The high-hardness industrial wastewater treatment process as described in claim 3, characterized in that, The mass ratio of the modified attapulgite to nitrogen-doped carbon quantum dots is 1:0.3~0.8.