A method and system for synergistically degrading COD and new pollutants in industrial wastewater based on catalytic reduction-oxidation
By employing a catalytic reduction-oxidation synergistic degradation method, and utilizing a combination of sulfite, iodide, and persulfate catalysts, the problem of complete degradation of perfluorinated compounds in dyeing and printing wastewater was solved, achieving efficient, economical, and pollution-free treatment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 浙江工业大学绍兴研究院
- Filing Date
- 2026-04-07
- Publication Date
- 2026-06-23
AI Technical Summary
Existing technologies for treating perfluorinated compounds (PFCs) in dyeing and printing wastewater suffer from problems such as incomplete degradation, high energy consumption, susceptibility to water quality interference, and the risk of secondary pollution.
A catalytic reduction-oxidation synergistic degradation method was adopted. By adjusting the pH of the wastewater to alkaline, sulfite and alkali metal iodides were added for catalytic reduction reaction. Subsequently, persulfate and ferrous sulfate were added for catalytic oxidation reaction. Ultraviolet light and a directional catalyst were used to form a complex, attack the CF bond and completely mineralize the short-chain fluorine-containing intermediate.
It achieves a removal rate of >95% for PFOA and PFOS, a removal rate of >90% for total organic carbon (TOC), and a defluorination rate of >96%, with no secondary pollution and good economic efficiency for engineering applications.
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Figure CN122254686A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of wastewater treatment, specifically relating to a method and system for the synergistic degradation of COD and new pollutants in industrial wastewater based on catalytic reduction-oxidation. Background Technology
[0002] Perfluorinated compounds (PFCs) are widely used in industries such as textiles, papermaking, and electroplating due to their unique hydrophobic and oleophobic properties, ultimately ending up in wastewater from dyeing and printing industrial parks. The strong carbon-fluorine (CF) bonds (bond energy ~485 kJ / mol) in PFC molecules and the spatial shielding effect formed by fluorine atoms give them extremely high inertness to traditional biodegradation and chemical oxidation. Existing technologies have explored various approaches, but all have significant limitations.
[0003] Chinese patent CN116282416A (A method for degrading various perfluorinated and polyfluorinated compounds in water using piezoelectric catalysis of polytetrafluoroethylene powder) discloses the use of polytetrafluoroethylene (PTFE) powder as a piezoelectric catalyst, which uses ultrasonic vibration to provide mechanical energy, inducing PTFE to generate a piezoelectric effect to degrade PFCs. The key feature of this technology is the use of PTFE, an inert material, as the core catalyst, relying on external mechanical energy (ultrasound) input. Its drawbacks are: firstly, ultrasonic energy decays rapidly in water, resulting in low energy efficiency when treating large-scale wastewater; secondly, PTFE powder is difficult to effectively separate and recover from water bodies, easily causing secondary pollution and potentially generating unknown fluoride-containing intermediates; and finally, the adaptability of this technology to complex water qualities (such as high-COD dyeing and printing wastewater) has not been verified, and its practical application prospects are unclear.
[0004] Chinese patent CN114939396A (Inorganic silicon activated carbon for removing perfluorinated compounds, preparation method and application) enhances the adsorption capacity for PFCs by constructing a polysilicon dioxide layer (forming CO-Si bonds) on the surface of activated carbon. Its technical feature lies in utilizing the physicochemical adsorption of modified activated carbon, with a typical dosage of 5-15 mg / L. The fundamental drawback of this technology is that it is merely a pollutant transfer technology, not a degradation technology. It enriches PFCs from water to the solid phase, producing hazardous waste activated carbon rich in PFCs, resulting in high subsequent disposal costs and the risk of secondary release. Furthermore, its adsorption capacity for short-chain PFCs is limited, and the adsorption capacity is easily inhibited by competition from other organic matter in dyeing and printing wastewater, failing to achieve complete elimination of PFCs.
[0005] In summary, existing technologies for treating PFCs in actual dyeing and printing wastewater generally face core challenges such as incomplete degradation, high energy consumption, susceptibility to water quality interference, and the risk of secondary pollution. Therefore, there is an urgent need to develop a new treatment technology that can efficiently and completely degrade PFCs, has strong anti-interference capabilities, and is environmentally friendly. Summary of the Invention
[0006] To address the aforementioned technical problems in existing technologies, the present invention aims to provide a method and system for the synergistic degradation of COD and new pollutants in industrial wastewater based on catalytic reduction-oxidation. This method and system can efficiently and thoroughly degrade perfluorinated compounds (PFCs) in actual dyeing and printing wastewater, and has strong anti-interference capabilities, low operating costs, and no secondary pollution.
[0007] The technical solution adopted in this invention is as follows: A method for the synergistic degradation of COD and novel pollutants in industrial wastewater based on catalytic reduction-oxidation includes the following steps: Step 1: Adjust the pH of the dyeing and printing wastewater containing perfluorinated compounds (PFCs) to alkaline; Step 2: Add the reducing agent sulfite and the catalyst alkali metal iodide to the wastewater described in Step 1, and then pass it into a catalytic reduction reactor. Under ultraviolet light irradiation and stirring, a catalytic reaction takes place. The ultraviolet light reacts with the sulfite to generate strongly reducing hydrated electrons (e). aq - Iodide ions act as a directional catalyst to form complexes with PFCs, guiding e aq - It preferentially attacks the CF bond of PFCs to form short-chain fluorine-containing intermediates; Step 3: After the catalytic reduction in Step 2, the oxidant persulfate PMS and the catalyst ferrous sulfate are added to the effluent. The mixture is then pumped into a catalytic oxidation reactor equipped with a stirrer. The catalytic oxidation reaction is carried out under light-protected and stirred conditions. Ferrous sulfate activates the PMS to generate sulfate radicals, completely mineralizing the short-chain fluorine-containing intermediates produced in the reduction stage into CO2 and F2. - It also degrades residual organic matter.
[0008] Furthermore, in step 1, the pH of the dyeing and printing wastewater is adjusted to 8-10.
[0009] Furthermore, in step 2, the final concentration of sulfite in the wastewater is 5-20 mM, preferably 10-15 mM, and the final concentration of alkali metal iodide in the wastewater is 0.5-2 mM, preferably 0.8-1.2 mM.
[0010] Furthermore, in step 2, the alkali metal iodide is KI or NaI.
[0011] Furthermore, in step 2, the wavelength of the ultraviolet light is 250-260 nm, preferably 254 nm ± 2 nm, and the intensity of the ultraviolet light is 10-50 mW / cm². 2 20-30 mW / cm is preferred 2 .
[0012] Furthermore, in step 2, the reaction time of the wastewater in the catalytic reduction reactor is 20-60 minutes, preferably 30-45 minutes.
[0013] Furthermore, in step 3, the final concentration of PMS in the wastewater is 5-15 mM, preferably 8-12 mM, and the final concentration of ferrous sulfate in the wastewater is 0.1-1 mM, preferably 0.3-0.7 mM.
[0014] Furthermore, in step 3, the reaction time of the wastewater in the catalytic oxidation reactor is 30-90 minutes, preferably 50-70 minutes.
[0015] This invention relates to a system for the synergistic degradation of perfluorinated compounds in dyeing and printing wastewater via catalytic reduction and catalytic oxidation. The system comprises a raw water tank, a pH adjustment tank, a catalytic reduction reactor, a catalytic oxidation reactor, and a final effluent tank, connected sequentially by pipelines. The catalytic reduction reactor contains an ultraviolet light source, a stirrer, and a reagent dosing port, while the catalytic oxidation reactor contains a stirrer and a reagent dosing port. The catalytic reduction reactor and the catalytic oxidation reactor are connected in series via pipelines and a delivery pump to form a continuous treatment process. The reactor materials can be stainless steel (lined with an anti-corrosion coating), UPVC, or fiberglass to ensure corrosion resistance. The system can integrate a PLC automatic control unit for precise control of pH, reagent dosage, reaction time, and the start / stop of the UV lamp.
[0016] Compared with the prior art, the beneficial effects achieved by the present invention are: 1) Synergistic mechanism and strong anti-interference ability: The specific combination of "UV / sulfite / iodide" in the catalytic reduction step, especially the application of iodide as a directional catalyst; and the specific combination of "persulfate / iron-based catalyst" in the catalytic oxidation step, are used to completely mineralize short-chain fluorine-containing intermediates. The sequential coupling of "catalytic reduction-catalytic oxidation" and the directional catalytic effect of iodide effectively resist the interference of the complex matrix of dyeing and printing wastewater.
[0017] 2) High-efficiency degradation and thorough mineralization: PFOA and PFOS removal rate >95%, total organic carbon (TOC) removal rate >90%, and defluorination rate >96%.
[0018] 3) Economic efficiency and environmental friendliness: No precious metal catalysts or consumable electrodes are required, the main reagents are inexpensive; there is no secondary pollution, and it has good economic efficiency in engineering applications. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the process flow structure of the system for the catalytic reduction-catalytic oxidation synergistic degradation of perfluorinated compounds in dyeing and printing wastewater according to this application. Detailed Implementation
[0020] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.
[0021] Example 1: A method for the synergistic degradation of COD and new pollutants in industrial wastewater based on catalytic reduction-oxidation, compared with a control method. Figure 1 This includes the following steps: Step 1: Take 1L of biological effluent from a dyeing and printing factory (containing PFOA 1000 ng / L, COD 80 mg / L), and adjust the pH to 9.0 with NaOH; Step 2: Add Na2SO3 to the wastewater from Step 1 to a final concentration of 10 mM, add KI to a final concentration of 1 mM, and then pass the solution into a catalytic reduction reactor. The solution is then subjected to 254 nm UV light (25 mW / cm²). 2 Stir and react for 40 minutes; Step 3: After the catalytic reduction in Step 2, add PMS to a final concentration of 10 mM and FeSO4 to a final concentration of 0.5 mM, then pump the mixture into a catalytic oxidation reactor equipped with a stirrer and stir for 60 minutes in the dark.
[0022] In this invention, the defluorination rate (fluoride ion release rate) is measured by measuring the free fluoride ions (F) in the water samples before and after the reaction. - The defluorination rate (%) is calculated by considering the change in concentration and the theoretical maximum amount of fluoride that can be released upon complete mineralization of the target PFCs. The calculation formula is as follows: Defluorination rate (%) = (C) / (PFCs) t - C0) / (C theoretical ) × 100% In the formula: C t : Fluoride ion concentration (mg / L) in the water sample after the reaction. C0: Fluoride ion concentration (mg / L) in the raw water sample before reaction; C theoretical Based on the initial concentration and molecular formula of the target PFCs, calculate the theoretical total amount of fluoride ions (mg / L) that can be released upon complete mineralization.
[0023] Fluoride ion concentration was determined by ion chromatography (HJ 84-2016).
[0024] The results of the catalytic oxidation reaction in Example 1 were: PFOA removal rate >95%, TOC removal rate >92%, fluoride ion release rate >98%, and final effluent COD <15 mg / L.
[0025] Comparative Example 1: The experimental steps of Comparative Example 1 are the same as those of Example 1, except that the steps of catalytic reduction and catalytic oxidation are changed, while the other conditions remain the same.
[0026] In other words, in the experimental procedure of Comparative Example 1, the wastewater (same as in Example 1) was first adjusted to pH 9.0 with NaOH, then catalytic oxidation was performed (adding 10 mM PMS and 0.5 mM FeSO4 to a final concentration, stirring in the dark for 60 minutes), followed by catalytic reduction (adding 10 mM Na2SO3 and 1 mM KI to a final concentration, stirring at 254 nm UV (light intensity 25 mW / cm²)). 2 Stir for 40 minutes.
[0027] The results of the catalytic oxidation reaction in Comparative Example 1 were: PFOA removal rate <30%, TOC removal rate <40%, and fluoride ion release rate <35%.
[0028] Conclusion: After changing the "reduction-oxidation" sequence in Comparative Example 1, the degradation effect decreased significantly. This demonstrates that the synergistic sequence of "reduction-chain breaking followed by oxidation-mineralization" in this invention is crucial for the efficient degradation of robust PFCs. Direct oxidation is difficult to attack intact CF bonds, while subsequent reduction is inefficient for complex intermediates that have already been partially oxidized.
[0029] Compare with Example 2 (changing the ultraviolet wavelength): The experimental procedure of Example 2 was repeated in Example 1, except that in step 2, the wavelength of the ultraviolet light source was replaced with 300 nm or 400 nm, while maintaining a light intensity of 25 mW / cm². 2 "Unchanged", with all other conditions remaining unchanged.
[0030] The results of the catalytic oxidation reaction in Comparative Example 2 were as follows: when using 300 nm UV light, the PFOA removal rate was approximately 65%; when using 400 nm UV light, the PFOA removal rate was <10%.
[0031] Conclusion: 254 nm ultraviolet light is the most effective way to excite sulfite to produce a high concentration of hydrated electrons (ep). aq - The excitation efficiency of longer wavelength ultraviolet or visible light decreases significantly. This proves that specific short-wavelength ultraviolet light (250-260 nm) is a necessary condition for the efficient generation of reducing species in this technical solution.
[0032] Comparative Example 3 (KI catalyst omitted): The experimental steps of Example 1 were repeated in accordance with those of Example 3, except that "KI was not added in step 2 of the catalytic reduction step", while the other conditions remained the same.
[0033] The results of the catalytic oxidation reaction in Comparative Example 3 were: the PFOA removal rate was about 50%, the fluoride ion release rate was about 55%, and a variety of long and short chain fluorinated organic intermediates were detected in the water after the reaction.
[0034] Conclusion: Without iodide ions as a directional catalyst, hydrated electrons (e aq - KI (phosphorus chloride) indiscriminately attacks various components in wastewater (such as natural organic matter and dye molecules), resulting in low and incomplete defluorination efficiency of PFCs. The addition of KI, by forming a complex with PFCs, guides the removal of e-fluoride. aq - Prioritizing the attack on the CF key is the key to the high selectivity and strong anti-interference ability of this method (for complex dyeing wastewater).
[0035] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.
Claims
1. A method for the synergistic degradation of COD and new pollutants in industrial wastewater based on catalytic reduction-oxidation, characterized in that, Includes the following steps: Step 1: Adjust the pH of the dyeing and printing wastewater containing perfluorinated compounds (PFCs) to alkaline; Step 2: Add the reducing agent sulfite and the catalyst alkali metal iodide to the wastewater described in Step 1, and then pass it into a catalytic reduction reactor. Under ultraviolet light irradiation and stirring, a catalytic reaction takes place. The ultraviolet light reacts with the sulfite to generate strongly reducing hydrated electrons (e). aq - Iodide ions act as a directional catalyst to form complexes with PFCs, guiding e aq - It preferentially attacks the CF bond of PFCs to form short-chain fluorine-containing intermediates; Step 3: After the catalytic reduction in Step 2, the oxidant persulfate PMS and the catalyst ferrous sulfate are added to the effluent. The mixture is then pumped into a catalytic oxidation reactor equipped with a stirrer. The catalytic oxidation reaction is carried out under light-protected and stirred conditions. Ferrous sulfate activates the PMS to generate sulfate radicals, completely mineralizing the short-chain fluorine-containing intermediates produced in the reduction stage into CO2 and F2. - It also degrades residual organic matter.
2. The method for catalytic reduction-oxidation synergistic degradation of COD and new pollutants in industrial wastewater as described in claim 1, characterized in that, In step 1, the pH of the dyeing and printing wastewater is adjusted to 8-10.
3. The method for synergistic degradation of COD and new pollutants in industrial wastewater based on catalytic reduction-oxidation as described in claim 1, characterized in that, In step 2, the final concentration of sulfite in the wastewater is 5-20 mM, preferably 10-15 mM, and the final concentration of alkali metal iodide in the wastewater is 0.5-2 mM, preferably 0.8-1.2 mM.
4. The method for synergistic degradation of COD and new pollutants in industrial wastewater based on catalytic reduction-oxidation as described in claim 1, characterized in that, In step 2, the alkali metal iodide is KI or NaI.
5. The method for catalytic reduction-oxidation synergistic degradation of COD and new pollutants in industrial wastewater as described in claim 1, characterized in that, In step 2, the wavelength of the ultraviolet light is 250-260 nm, preferably 254 nm ± 2 nm, and the intensity of the ultraviolet light is 10-50 mW / cm². 2 20-30 mW / cm is preferred 2 .
6. The method for synergistic degradation of COD and new pollutants in industrial wastewater based on catalytic reduction-oxidation as described in claim 1, characterized in that, In step 2, the reaction time of the wastewater in the catalytic reduction reactor is 20-60 minutes, preferably 30-45 minutes.
7. The method for catalytic reduction-oxidation synergistic degradation of COD and new pollutants in industrial wastewater as described in claim 1, characterized in that, In step 3, the final concentration of PMS in the wastewater is 5-15 mM, preferably 8-12 mM, and the final concentration of ferrous sulfate in the wastewater is 0.1-1 mM, preferably 0.3-0.7 mM.
8. The method for catalytic reduction-oxidation synergistic degradation of COD and new pollutants in industrial wastewater as described in claim 1, characterized in that, In step 3, the reaction time of the wastewater in the catalytic oxidation reactor is 30-90 minutes, preferably 50-70 minutes.
9. The system for the method of catalytic reduction-oxidation synergistic degradation of COD and new pollutants in industrial wastewater as described in claim 1, characterized in that... It includes a raw water tank, a pH adjustment tank, a catalytic reduction reactor, a catalytic oxidation reactor, and a final effluent tank, which are connected in sequence by pipelines. The catalytic reduction reactor contains an ultraviolet light source, a stirrer, and a reagent dosing port, and the catalytic oxidation reactor contains a stirrer and a reagent dosing port.