Advanced oxidation printing and dyeing wastewater treatment process

Abstract

The invention relates to an advanced oxidation printing and dyeing wastewater treatment process, and belongs to the technical field of sewage treatment. The method comprises the following steps: adding an aluminum oxide catalyst into to-be-treated printing and dyeing wastewater in a reactor, and stirring; adding an auxiliary agent, and mixing and stirring; adding an oxidizing agent potassium monopersulfate into the obtained mixed solution and stirring; under the irradiation of an ultraviolet light source, continuously introducing ozone prepared by an ozone generator into the reactor for stirring reaction. Pollutants such as refractory dyes and organic auxiliaries in the printing and dyeing wastewater are efficiently removed under mild conditions, the COD removal rate of effluent reaches 90% or above, the chroma removal rate reaches 90% or above, and the quality of the effluent meets the requirements of subsequent treatment or up-to-standard discharge.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a process for treating advanced oxidative dyeing and printing wastewater. Background Technology

[0002] The wastewater generated from wide-width fabric dyeing, denim, and knitting processes is characterized by large volumes and complex water quality, generally exhibiting high COD, high color intensity, and strong alkalinity, with low BOD / COD ratios and poor biodegradability, posing a significant challenge to wastewater treatment. Taking denim wastewater as an example, COD often exceeds 2000 mg / L, color intensity is thousands of times higher, and pH values ​​are typically between 11 and 13. This wastewater contains a large amount of recalcitrant organic pollutants, including aromatic amines, aldehydes, fatty acids, and amides, and some also contain phenols, nitriles, and organosilicon compounds. These substances have stable molecular structures and strong biotoxicity, not only contributing to the wastewater's dark color and high COD but also inhibiting microbial activity, resulting in poor biochemical treatment effects. Some aromatic amines even possess carcinogenic and persistent pollutant characteristics; therefore, the advanced treatment of dyeing wastewater urgently requires breakthroughs beyond the limitations of traditional processes.

[0003] Traditional treatment methods primarily employ biological and physiochemical approaches. Biological methods rely on microbial degradation, effectively removing readily degradable components, but their effectiveness is limited for complex or toxic recalcitrant substances, often resulting in excessive effluent color and COD. Physicochemical methods, such as coagulation and adsorption, can remove some large-molecule dyes, but they essentially transfer pollution, easily generating secondary waste and failing to completely decompose dissolved small-molecule organic matter. With increasingly complex dyeing and printing processes, single traditional processes are no longer sufficient to meet stable emission standards.

[0004] To address the bottleneck in removing recalcitrant pollutants, advanced oxidation technologies (AOPs) have attracted widespread attention due to their ability to generate highly oxidizing species such as hydroxyl radicals within the system. These radicals possess extremely high oxidation potentials, enabling non-selective chain scission and ring-opening of organic molecules, ultimately converting them into CO2 and H2O, thus achieving the complete degradation of recalcitrant substances. Compared to chlorination or ozone oxidation alone, AOPs exhibit stronger degradation capabilities, produce fewer byproducts, and are more environmentally friendly.

[0005] In summary, the treatment of wastewater from wide-width fabrics, denim, and knitwear dyeing requires more efficient advanced treatment processes. The ozone and ultraviolet synergistic advanced oxidation method employed in this invention is a solution addressing the shortcomings of traditional processes and the recalcitrant nature of the wastewater. It boasts advantages such as high reaction efficiency, wide applicability, and green and controllable operation, providing crucial technical support for the advanced treatment and stable compliance of wastewater discharge in the dyeing industry. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a process for treating advanced oxidative dyeing and printing wastewater. This invention employs an advanced oxidation technology that combines ozone, ultraviolet light, and potassium persulfate (PMS). Utilizing an alumina catalyst carrier, it achieves a highly efficient activation technology-PMS-alumina catalyst three-phase synergistic advanced oxidation process. This process effectively destroys the molecular structure of colored organic compounds, significantly improving decolorization and organic matter degradation efficiency. Thus, under relatively mild conditions, it efficiently removes recalcitrant dyes, organic auxiliaries, and other pollutants from dyeing and printing wastewater, achieving an effluent COD removal rate of over 90% and a color removal rate of over 90%, ensuring the effluent quality meets subsequent treatment or discharge standards.

[0007] This invention is achieved through the following scheme:

[0008] The purpose of this invention is to provide a process for treating advanced oxidative dyeing and printing wastewater, comprising the following steps:

[0009] (1) In the reactor, add alumina catalyst to the dyeing and printing wastewater to be treated and stir; then add auxiliaries and stir; so that the metal ions are fully mixed with the alumina catalyst and the wastewater;

[0010] (2) Add oxidant to the mixture obtained in step (1) and stir; allow PMS to be evenly dispersed in water;

[0011] (3) Under ultraviolet light irradiation, ozone generated by the ozone generator is continuously introduced into the reactor for stirring reaction. Ozone is continuously introduced into the reactor to form sufficient contact reaction in the water. Stirring during this process promotes the dissolution and mass transfer of ozone in the liquid phase and its reaction with pollutants. Stirring and necessary aeration are maintained during the reaction to ensure sufficient contact between the light field and the liquid phase. The light dose and residence time are adjusted in conjunction with the influent water quality (COD, color, UVT254).

[0012] When used in conjunction with ozone, they can be arranged synchronously or in series to enable UV-PMS / PDS and O3 to form a synergistic activation, thereby increasing the instantaneous concentration of free radicals and oxidation efficiency.

[0013] Further, in step (1), the particle size of the alumina catalyst is 100 μm to 1000 μm; preferably 150 μm to 600 μm;

[0014] And / or, the dosage of the alumina catalyst is 0.1 g / L to 5.0 g / L;

[0015] And / or, the stirring speed is 10 rpm to 100 rpm.

[0016] Further, in step (1), the auxiliary agent is selected from ferrous sulfate and / or manganese sulfate;

[0017] And / or, the amount of the adjuvant added is 0.5 mg / L to 5 mg / L;

[0018] And / or, the stirring time is 1 min to 10 min.

[0019] Further, in step (2), the oxidant is potassium persulfate;

[0020] And / or, the amount of the oxidant added is 0.2 mmol / L to 8.0 mmol / L;

[0021] And / or, the stirring time is 1 min to 15 min.

[0022] Further, in step (3), the ultraviolet light source is a low-pressure mercury lamp (main peak 254 nm, optionally including 185 nm spectral line), a medium-pressure mercury lamp (200–320 nm wide spectrum) or a UV-LED array (preferably 265–285 nm).

[0023] Furthermore, in step (3), the wavelength of the irradiation is 185 nm to 285 nm; the intensity is 90 μW / cm² to 200 μW / cm².

[0024] Furthermore, in step (3), the rated power of the ozone generator is 1 kW to 5 kW.

[0025] Furthermore, in step (3), the concentration of ozone gas is 50 mg / L to 400 mg / L;

[0026] And / or, the stirring speed is 20 rpm to 200 rpm.

[0027] Furthermore, in step (3), the reaction time is 10 min to 600 min;

[0028] And / or, the reaction temperature is 20°C to 30°C;

[0029] And / or, the pH of the reaction is 3.0–6.0.

[0030] Furthermore, the organic pollutants in the dyeing and printing wastewater are one or more of Rhodamine B, Methyl Blue, Methylene Blue, Methyl Orange, Acid Orange II, Brilliant Red 3BN, and Brilliant Black BN.

[0031] The reactor used in the above reaction is a vertical cylindrical container made of corrosion-resistant fiberglass (FRP) or stainless steel lined with rubber. The reactor has an effective volume of 10 m³, an inner diameter of approximately Φ2000 mm, and an effective liquid depth of approximately 3200 mm (with an additional 200 mm of free height to prevent liquid splashing). The reactor has a manhole and a stirrer installation port at the top for easy addition of reagents, observation, and maintenance; a raw water inlet is located in the upper middle part of the side wall, and an outlet and sludge discharge port are located at the bottom. An ozone gas addition interface is also reserved in the middle of the side wall. The reactor is installed on an outdoor concrete foundation.

[0032] The above reaction is stirred using a top-feed reducer agitator with a power of approximately 1 kW to 5 kW and a frequency converter speed range of 20 rpm to 120 rpm. It is equipped with a three-bladed impeller (double-layer baffle) with a diameter of 1 m to 2 m. The main material is stainless steel, and the shaft length is customized according to the liquid depth (2 m to 3 m). The seal uses a mechanical seal to prevent leakage and corrosion.

[0033] The circulating pump is a corrosion-resistant centrifugal pump with a flow rate of approximately 4 m³ / h to 20 m³ / h, a head of 10 m to 30 m, and a power of 1 kW to 5 kW. It is made of stainless steel or engineering plastics (resistant to oxidants). The inlet pump is used to transport raw water from the raw water tank to the reactor, and its specifications are similar to the circulating pump.

[0034] The ozone generator has a rated power of 1 kW to 5 kW and is equipped with a stainless steel discharge tube and an air-cooled / water-cooled system. The ozone gas outlet is connected to the reactor ozone dosing port through an ozone-resistant pipe (PTFE).

[0035] Ozone itself is a strong oxidant, but with high selectivity. Upon exposure to ultraviolet light, ozone generates hydrogen peroxide and further decomposes into a large number of hydroxyl radicals, significantly improving degradation efficiency. The synergistic system of ozone / UV light can substantially reduce color and COD in a short time and effectively destroy stubborn pollutants such as aromatic amines and phenols. Compared with ozone or UV light alone, the ozone / UV combination achieves higher organic matter removal rates and deeper mineralization, while avoiding secondary pollution. In engineering applications, it requires less space and is easy to operate.

[0036] The technical solution of the present invention has the following advantages compared with the prior art:

[0037] This invention provides a process for treating advanced oxidative dyeing and printing wastewater. The invention employs a synergistic combination of multiple advanced oxidation activation methods, including metal catalysis, ozone, and ultraviolet light, which simultaneously generates various highly reactive species such as sulfate radicals, hydroxyl radicals, and singlet oxygen, significantly improving the degradation efficiency of complex organic pollutants in dyeing and printing wastewater. Compared with existing single activation methods, this invention has the following advantages:

[0038] (1) Broad-spectrum treatment: It is applicable to a variety of dyeing and printing wastewater such as wide-width fabrics, denim and knitwear, and has a good removal effect on recalcitrant pollutants such as aromatic amines, aldehydes, amides and organosilicon compounds.

[0039] (2) High reagent utilization rate: A high COD removal rate can be achieved with a low amount of oxidant and catalyst, which significantly reduces reagent consumption and operating costs.

[0040] (3) Good adaptability: The process is more adaptable to the pH range of the reaction and can flexibly adjust the operating parameters according to the actual situation on site to adapt to different types of water samples and water quality fluctuations.

[0041] (4) Excellent environmental friendliness: There are few by-products in the reaction process, the risk of secondary pollution is low, and emission safety is ensured through ozone tail gas treatment and process control measures.

[0042] (5) Strong engineering feasibility: The equipment design has reserved a variety of control and detection interfaces, which facilitates operation and scale-up applications and has high potential for industrial promotion.

[0043] In summary, this invention has significant advantages in terms of reaction efficiency, economy, safety, and engineering application prospects, providing an efficient, economical, and sustainable technical approach for the deep treatment of complex wastewater in the dyeing and printing industry. Detailed Implementation

[0044] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0045] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0046] Example 1

[0047] This embodiment discloses an advanced oxidation wastewater treatment process catalyzed by alumina catalyst, comprising the following steps:

[0048] (1) Raw water feeding: Start the water pump to transport the wide-width dyeing wastewater from the raw water tank to the pilot reactor. After the water feeding is completed, close the water inlet valve.

[0049] (2) Catalyst addition: Alumina catalyst (purchased from Aladdin, catalog number A489818) was added to the reactor. The alumina catalyst was crushed and sieved before addition to prepare different particle sizes of 150 μm and 600 μm. The catalyst addition amount was 0.1 g / L, and the stirring speed of the wastewater was 10 rpm during addition.

[0050] (3) Addition of additives: Add a small amount of ferrous sulfate (FeSO4) solution at a rate of 0.5 mg / L. After addition, continue stirring for 1 min to ensure that the metal ions are fully mixed with the alumina catalyst and wastewater.

[0051] (4) Addition of oxidant: Add 0.2 mmol / L potassium persulfate (PMS) to the reactor and stir for 1 min after addition to allow PMS to be evenly dispersed in water.

[0052] (5) Advanced Oxidation Activation 1 (Ozone Activation): Turn on the oxygen generator and ozone generator. After the ozone concentration stabilizes, start the circulation pump to perform the ozone addition reaction. Set the ozone aeration gas concentration to 50 mg / L. Keep the ozone continuously flowing into the reactor to form a sufficient contact reaction in the water. During this process, the stirrer maintains a speed of 20 rpm to promote the dissolution and mass transfer of ozone in the liquid phase and its reaction with pollutants. The ozone generator is selected with a rated power of 1 kW. The circulation pump is a corrosion-resistant centrifugal pump with a flow rate of about 4 m³ / h, a head of 10 m, and a power of 1 kW.

[0053] (6) Advanced oxidation activation 2 (UV activation): After adding the oxidant and completing the premixing in step (5), turn on the UV light source. The UV light source can be a low-pressure mercury lamp (main peak 254 nm, including 185 nm spectral line), with an intensity of 90 μW / cm. 2 .

[0054] (7) Reaction maintenance: Start timing the ozone-PMS-alumina catalyst reaction for 10 min from the start of ozone introduction. Maintain the reaction temperature at 20~30℃ and the pH at 4.5.

[0055] (8) Effluent recovery: The clarified treated effluent is pumped out of the reactor by the effluent pump, the water volume is measured and water samples are collected to test the treatment effect and detect indicators such as COD.

[0056] (9) Catalyst reuse: The collected alumina catalyst precipitate can be partially reused in the next batch of tests after simple washing, saving catalyst costs.

[0057] The agitator used in the above steps is a top-feed reducer agitator with a power of about 1 kW, a frequency conversion speed regulation of 20 rpm, and a three-bladed impeller (double-layer baffle) with a diameter of 1 m.

[0058] When alumina with a particle size of 150 μm was used as a catalyst, the COD removal rate in the water was found to be 91.2% and the color removal rate was 91.8%.

[0059] When alumina with a particle size of 600 μm was used as a catalyst, the COD removal rate in the water was found to reach 90.0% and the color removal rate to be 94.2%.

[0060] Example 2

[0061] This embodiment provides an advanced oxidation wastewater treatment process catalyzed by an alumina catalyst, comprising the following steps:

[0062] (1) Raw water feeding: Start the water pump to transport the wide-width dyeing wastewater from the raw water tank to the pilot reactor. After the water feeding is completed, close the water inlet valve.

[0063] (2) Catalyst addition: Alumina catalyst (purchased from Aladdin, catalog number A431629) was added to the reactor. The alumina catalyst was crushed and sieved before addition to prepare different particle sizes of 150 μm and 600 μm. The catalyst addition rate was 5.0 g / L, and the stirring speed of the wastewater was 100 rpm during addition.

[0064] (3) Addition of additives: Add a small amount of manganese sulfate (MnSO4) solution at 5 mg / L, and continue stirring for 10 min after addition to ensure that the metal ions are fully mixed with the alumina catalyst and wastewater.

[0065] (4) Addition of oxidant: Add potassium persulfate (PMS) to the reactor. The actual addition range is 8.0 mmol / L according to the experimental plan. After addition, maintain stirring for 15 min to allow PMS to be evenly dispersed in water.

[0066] (5) Advanced Oxidation Activation 1 (Ozone Activation): Turn on the oxygen generator and ozone generator. After the ozone concentration stabilizes, start the circulation pump to perform the ozone addition reaction. Set the ozone aeration gas concentration to 400 mg / L. Keep the ozone continuously flowing into the reactor to form a sufficient contact reaction in the water. During this process, the stirrer maintains a speed of 200 rpm to promote the dissolution and mass transfer of ozone in the liquid phase and its reaction with pollutants. The ozone generator is selected with a rated power of 5 kW. The circulation pump is a corrosion-resistant centrifugal pump with a flow rate of about 20 m³ / h, a head of 30 m, and a power of 5 kW.

[0067] (6) Advanced oxidation activation 2 (UV activation): After adding the oxidant and completing the premixing in step (5), turn on the UV light source. The UV light source can be a low-pressure mercury lamp UV-LED array (wavelength 275 nm) with an intensity of 150 μW / cm². 2 .

[0068] (7) Reaction maintenance: The ozone-UV-PMS-alumina catalyst reaction was maintained for 600 min from the start of ozone introduction. The reaction temperature was maintained at ambient temperature of 20~30℃ and the pH was controlled at 3.5.

[0069] (8) Effluent recovery: The clarified treated effluent is pumped out of the reactor by the effluent pump, the water volume is measured and water samples are collected to test the treatment effect and detect indicators such as COD.

[0070] (9) Catalyst reuse: The collected alumina catalyst precipitate can be partially reused in the next batch of tests after simple washing, saving catalyst costs.

[0071] The UV lamps are 320 W x 12, with a tube diameter of 19 mm and a length of 1554 mm. The outer diameter x inner diameter x length (mm) of the matching quartz sleeve is 28 x 25 x 1640.

[0072] The agitator is a top-feed type reducer agitator with a power of about 5 kW and a frequency conversion speed regulation of 120 rpm. It is equipped with a three-bladed impeller (double-layer baffle) with a diameter of 2 m.

[0073] When alumina with a particle size of 150 μm was used as a catalyst, the COD removal rate in the water was found to be 90.2% and the color removal rate was 90.9%.

[0074] When alumina with a particle size of 600 μm was used as a catalyst, the COD removal rate in the water was found to be 90.5% and the color removal rate was 92.8%.

[0075] Comparative Example 1

[0076] This comparative example provides an advanced oxidation wastewater treatment process catalyzed by an alumina catalyst, similar to Example 1, except that the alumina catalyst in step (1) is replaced with an Fe-based catalyst (purchased from Aladdin, EC No.: 236-908-0). The other steps are consistent with those in Example 1.

[0077] The COD removal rate in the water was 56.7%, and the color removal rate was 85.1%.

[0078] Comparative Example 2

[0079] This comparative example provides an advanced oxidation wastewater treatment process catalyzed by an alumina catalyst, similar to Example 1, except that step (5) ozone activation is omitted. All other steps remain the same as in Example 1.

[0080] When alumina with a particle size of 150 μm is used as a catalyst, the COD removal rate in water is 49.9% and the color removal rate is 75.1%.

[0081] Comparative Example 3

[0082] This comparative example provides an advanced oxidation wastewater treatment process catalyzed by an alumina catalyst, similar to Example 1, except that step (6) of ultraviolet light activation is omitted. The other steps are consistent with those in Example 1.

[0083] When alumina with a particle size of 150 μm is used as a catalyst, the COD removal rate in water is 32.9% and the color removal rate is 80.1%.

[0084] Comparative Example 4

[0085] This comparative example provides an advanced oxidation wastewater treatment process catalyzed by an alumina catalyst, similar to Example 1, except that potassium persulfate in step (4) is replaced with potassium persulfate. All other steps remain the same as in Example 1.

[0086] When alumina with a particle size of 150 μm is used as a catalyst, the COD removal rate in water is 22.1% and the color removal rate is 77.6%.

[0087] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A process for the treatment of advanced oxidation of printing and dyeing wastewater, characterized by, The method comprises the following steps: (1) adding an alumina catalyst to the printing and dyeing wastewater to be treated in a reactor and stirring; then adding an auxiliary agent and stirring; (2) adding an oxidizing agent potassium monopersulfate to the mixture obtained in step (1) and stirring; (3) continuously feeding ozone prepared by an ozone generator into the reactor under the irradiation of an ultraviolet light source and stirring and reacting; In step (1), the particle size of the alumina catalyst is 100 μm-1000 μm; the auxiliary agent is selected from ferrous sulfate and / or manganese sulfate.

2. The process according to claim 1, characterized in that, In step (1), the addition amount of the alumina catalyst is 0.1 g / L-5.0 g / L; And / or, the stirring speed is 10 rpm-100 rpm.

3. The process of claim 1, wherein, In step (1), the addition amount of the auxiliary agent is 0.5 mg / L-5 mg / L; And / or, the stirring time is 1 min-10 min.

4. The process of claim 1, wherein, In step (2), the addition amount of the potassium monopersulfate is 0.2 mmol / L-8.0 mmol / L; And / or, the stirring time is 1 min-15 min.

5. The process of claim 1, wherein, In step (3), the ultraviolet light source is a low-pressure mercury lamp, a medium-pressure mercury lamp or a UV-LED array.

6. The process of claim 1, wherein, In step (3), the wavelength of the irradiation is 185 nm-285 nm, and the intensity is 90 μW / cm²-200 μW / cm².

7. The process of claim 1, wherein, In step (3), the rated power of the ozone generator is 1 kW-5 kW.

8. The process of claim 1, wherein, In step (3), the gas concentration of the ozone is 50 mg / L-400 mg / L; And / or, the stirring speed is 20 rpm-200 rpm.

9. The process of claim 1, wherein, In step (3), the reaction time is 10 min-600 min; And / or, the reaction temperature is 20℃-30℃; And / or, the pH value of the reaction is 3.0-6.

0.

10. The process of claim 1, wherein, The organic pollutants in the printing and dyeing wastewater are one or more of rhodamine B, methyl blue, methylene blue, methyl orange, acid orange II, brilliant red 3BN and brilliant black BN.