Method for deeply treating organic pollutants in lignite gasification biochemical wastewater by using far ultraviolet light activated oxidant

Abstract

The invention belongs to the technical field of water treatment, and particularly relates to a method for deeply treating organic pollutants in lignite gasification biochemical wastewater by using a far ultraviolet light activated oxidant. The method comprises the following steps: mixing lignite gasification biochemical wastewater with an oxidizing agent, and carrying out photocatalytic degradation reaction on the obtained reaction liquid to obtain effluent; the oxidizing agent comprises one or more of H2O2, persulfate and periodate; the photocatalytic degradation reaction is carried out under far ultraviolet light. The method provided by the invention can effectively degrade organic pollutants in lignite gasification biochemical wastewater, especially refractory organic pollutants, the removal rate of organic matters is greater than or equal to 90%, up-to-standard discharge can be realized, the treatment period is shortened (the total reaction time is 2-4 hours), the environmental adaptability is strong, and the method is suitable for industrial production. The problems that in a traditional Fenton method, the agent adding amount is large, the wastewater pH value adaptability is poor, the treatment efficiency of low-concentration refractory organic matter is unstable, the process reaction period is long, and the operation and maintenance cost is high are solved.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a method for deep treatment of organic pollutants in lignite gasification biochemical wastewater using far-ultraviolet light-activated oxidants. Background Technology

[0002] Lignite gasification technology is an important part of the coal chemical industry. However, the lignite gasification wastewater generated during the gasification process is complex in composition, high in COD (even after biological treatment, it still reaches 600-900 mg / L), has high color, and is highly toxic, containing recalcitrant heterocyclic compounds (pyridine, quinoline), which is a bottleneck restricting the industry's development. For this type of recalcitrant wastewater after aerobic and anaerobic biological treatment, most companies generally use the Fenton process for advanced treatment after multi-stage pretreatment. Related technologies disclose a method for advanced treatment of biological wastewater, which includes sequentially passing the biological wastewater through coagulation sedimentation, Fenton oxidation, and adsorption filtration. The Fenton oxidation step involves adjusting the pH value and Fe... 2+ The dosage is increased to enhance the generation of hydroxyl radicals, aiming to remove residual stubborn organic matter and color from wastewater. However, due to the characteristics of biological effluent, existing treatment methods still have many practical problems: (1) The traditional Fenton process relies on the addition of a large amount of chemical agents, which not only produces a large amount of iron-containing sludge that causes secondary pollution, but also, if such sludge is not properly solidified and landfilled or resource-based treated, it is very easy to infiltrate and pollute the soil and groundwater through leachate, forming a serious risk of secondary pollution and increasing the pressure and cost of subsequent environmental protection disposal. (2) The pH value of the wastewater is subject to strict requirements. The acid-base adjustment process consumes a lot of energy and requires the treatment system to be equipped with an additional acid-base adjustment unit. The pH value of the wastewater is reduced to a specified range by adding concentrated sulfuric acid. After the reaction is completed, alkaline agents such as sodium hydroxide are added to neutralize it to neutral. The whole process not only consumes a lot of acid and alkali agents, but the continuous operation of the adjustment equipment will also generate high energy consumption. Especially when treating large volumes of wastewater, the energy cost of the acid-base adjustment process can account for 15-20% of the total treatment cost, which significantly reduces the economic efficiency of the process.

[0003] (3) The treatment efficiency of low-concentration recalcitrant organic matter is easily affected by water quality fluctuations, resulting in poor stability of effluent indicators and frequent failures to meet standards: When the influent COD load, pollutant composition or salinity changes, the free radical generation efficiency in the Fenton reaction system will fluctuate drastically, resulting in incomplete oxidation and degradation of the target pollutants. (4) Although the Fenton process achieves synergy of multi-stage treatment, the reaction cycle of the Fenton oxidation unit is long, and the subsequent adsorption filtration requires regular replacement of filter media, which increases the equipment operation and maintenance costs and downtime losses. The overall economic efficiency and continuity of the process need to be improved. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for deep treatment of organic pollutants in lignite gasification biochemical wastewater using far-ultraviolet light-activated oxidants. The method provided by this invention can effectively degrade organic pollutants in lignite gasification biochemical wastewater, especially recalcitrant organic pollutants, with an organic matter removal rate of ≥90% and can meet emission standards. It shortens the treatment cycle (total reaction time 2-4 hours, based on COD reaching the emission standard, i.e., COD below 80 mg / L), has strong environmental adaptability, and solves the problems of large reagent dosage, poor adaptability to wastewater pH, unstable treatment efficiency of low-concentration recalcitrant organic matter, long process reaction cycle, and high operation and maintenance costs in the traditional Fenton process.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for deep treatment of organic pollutants in lignite gasification biochemical wastewater using far-ultraviolet light-activated oxidants, comprising the following steps: The lignite gasification biochemical wastewater and oxidant are mixed, and the resulting reaction solution is subjected to photocatalytic degradation reaction to obtain effluent; The oxidant includes one or more of H2O2, persulfate, and periodate; The photocatalytic degradation reaction is carried out under far-ultraviolet light.

[0006] Preferably, when the color of the lignite gasification biochemical wastewater is ≥100 times, before mixing the lignite gasification biochemical wastewater and the oxidant, the method further includes: mixing the lignite gasification biochemical wastewater and the flocculant for flocculation treatment, and then mixing the resulting supernatant with the oxidant.

[0007] Preferably, the persulfate includes perdisulfate and / or potassium permonosulfate complex salt.

[0008] Preferably, the periodate includes potassium periodate and / or sodium periodate.

[0009] Preferably, the flocculant includes inorganic flocculants and organic flocculants; the inorganic flocculant is polyaluminum sulfate and / or polyaluminum chloride; the organic flocculant is polyacrylamide and / or cationic polyacrylamide.

[0010] Preferably, the wavelength of the far-ultraviolet light is 185~365nm.

[0011] Preferably, the photocatalytic degradation reaction takes 60 to 240 minutes.

[0012] Preferably, the concentration of persulfate in the reaction solution is 10~50mM.

[0013] Preferably, the concentration of periodate in the reaction solution is 5~40mM.

[0014] Preferably, the concentration of H2O2 in the reaction solution is 4.9~38.8mM.

[0015] This invention provides a method for deep treatment of organic pollutants in lignite gasification biochemical wastewater using far-ultraviolet light-activated oxidants, comprising the following steps: The lignite gasification biochemical wastewater and oxidant are mixed, and the resulting reaction solution is subjected to photocatalytic degradation reaction to obtain effluent; The oxidant includes one or more of H2O2, persulfate, and periodate; The photocatalytic degradation reaction is carried out under far-ultraviolet light.

[0016] The beneficial effects of the method for deep treatment of organic pollutants in lignite gasification biochemical wastewater provided by the present invention using far-ultraviolet light-activated oxidant are as follows: (1) To solve the problem of large dosage of traditional Fenton process reagents, the activity of the oxidation system is enhanced by ultraviolet light. While reducing the dosage of oxidant (H2O2), the efficiency of free radical generation is improved by the synergistic effect of PMS (persulfate) and KIO4, reducing the consumption of chemical reagents and the amount of iron-containing sludge generated in the future, thus controlling the risk of secondary pollution from the source. (2) Solve the problem of poor pH adaptability of wastewater, break through the limitation of the traditional Fenton method which is only applicable to strongly acidic environments, broaden the pH range of the ultraviolet light activation system, and can stably react in the pH range of wastewater 3~9, eliminate the frequent acid-base adjustment steps, reduce reagent consumption and energy costs, and improve the convenience of process operation. (3) To address the problem of unstable treatment efficiency for low-concentration, recalcitrant organic matter, the strong penetrability and catalytic activity of ultraviolet light are utilized to activate the oxidation system and generate various highly active free radicals (·OH, SO4·). - (such as IO3·), to enhance the degradation ability of heterocyclic compounds such as pyridine and quinoline, improve the resistance to water quality fluctuations, and ensure that the effluent COD, color and other indicators meet the standards stably; (4) It solves the problems of long process reaction cycle and high operation and maintenance cost. The instant activation characteristics of ultraviolet light can shorten the oxidation reaction cycle. Compared with the traditional Fenton method and multi-stage treatment process, it reduces the space occupied by equipment and the running time, while reducing the loss of operation and maintenance links such as filter replacement, and improving the economic efficiency and continuity of the process. (5) To solve the problem of high carbon emissions in the treatment process, the carbon emissions in the production of reagents and operation of equipment are reduced through the technical approach of low reagent addition and low energy consumption, so as to provide a low-carbon and environmentally friendly technical solution for the treatment of lignite gasification biochemical wastewater. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the process for treating lignite gasification biochemical wastewater using an ultraviolet light-activated oxidant (H2O2, PMS, KIO4) system in an embodiment of the present invention. Figure 2 The graph shows the test results of pH value, COD concentration and COD removal rate of the supernatant obtained from flocculation treatment under different amounts of polyaluminum sulfate flocculant added in Example 1. Figure 3 This is a graph showing three parallel COD degradation processes under different concentrations of H2O2 activated by a 254nm UV lamp, obtained in Example 2. Figure 4 The graph shows the COD removal rates of three parallel runs at different concentrations of H2O2 activated by 254nm UV lamps obtained in Example 2. Figure 5 This is a diagram illustrating the electron paramagnetic technique of activating H2O2 with a 254nm ultraviolet lamp obtained in Example 2. Figure 6 The graph shows three parallel COD degradation events at different concentrations of PMS activated by 254nm UV lamp, obtained in Example 3. Figure 7 The graph shows the COD removal rates of three parallel PMS treatments at different concentrations activated by 254nm UV lamps obtained in Example 3. Figure 8 This is a diagram of the electron paramagnetic technique of PMS activated by 254nm ultraviolet lamp obtained in Example 3; Figure 9 The graph shows three parallel COD degradation events at different concentrations of KIO4 activated by 254nm UV lamp, obtained in Example 4. Figure 10 The graph shows the COD removal rates of three parallel trials at different concentrations of KIO4 activated by 254nm UV lamps obtained in Example 4. Figure 11 This is a diagram illustrating the electron paramagnetic technique of KIO4 activated by a 254nm ultraviolet lamp obtained in Example 4. Figure 12 Colorimetric diagrams of raw water, supernatant obtained from flocculation treatment, and reaction solutions after treatment in Examples 2 (H2O2 volume fraction of 2‰), 3 (PMS addition amount of 30mM), and 4 (KIO4 addition amount of 30mM); Figure 13 The pH values ​​of the raw water, the supernatant obtained from flocculation treatment, and the reaction solutions after treatment in Examples 2 (H2O2 volume fraction of 2‰), 3 (PMS addition amount of 30mM), and 4 (KIO4 addition amount of 30mM) are shown in the graph. Figure 14The BOD5 / COD ratios are shown for raw water, supernatant obtained from flocculation treatment, and reaction solutions after treatment in Examples 2 (H2O2 addition volume fraction of 2‰), 3 (PMS addition amount of 30mM), and 4 (KIO4 addition amount of 30mM). Detailed Implementation

[0018] This invention provides a method for deep treatment of organic pollutants in lignite gasification biochemical wastewater using far-ultraviolet light-activated oxidants, comprising the following steps: The lignite gasification biochemical wastewater and oxidant are mixed, and the resulting reaction solution is subjected to photocatalytic degradation reaction to obtain effluent; The oxidant includes one or more of H2O2, persulfate, and periodate; The photocatalytic degradation reaction is carried out under far-ultraviolet light.

[0019] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0020] As one implementation method, when the color of the lignite gasification biochemical wastewater is ≥100 times, before mixing the lignite gasification biochemical wastewater and the oxidant, the method further includes: mixing the lignite gasification biochemical wastewater and the flocculant for flocculation treatment, and then mixing the resulting supernatant with the oxidant.

[0021] In one embodiment, the lignite gasification biochemical wastewater is the lignite gasification biochemical effluent; the organic pollutants in the lignite gasification biochemical wastewater are recalcitrant organic pollutants; the recalcitrant organic pollutants include one or more of long-chain alkanes, anilines, and volatile phenols; in Example 1, the lignite gasification biochemical wastewater has a COD of 818.10 mg / L, a color of 200 times, and a pH of 7.5; the flocculant includes inorganic flocculants and organic flocculants; the inorganic flocculant is polyaluminum sulfate and / or polyaluminum chloride (PAC), specifically polyaluminum sulfate in this embodiment; the organic flocculant is polyacrylamide (PAM) and / or cationic polyacrylamide (CPAM), specifically polyacrylamide (PAM) in this embodiment; the inorganic flocculant is used in the form of an inorganic flocculant solution; the organic flocculant is used in the form of an organic flocculant solution; the mass fraction of the inorganic flocculant in the inorganic flocculant solution is 10-50%, specifically in this embodiment... 30%; the mass fraction of organic flocculant in the organic flocculant solution is 1-10‰, specifically 5‰ in this embodiment; the volume of the inorganic flocculant solution is 1-10‰ of the volume of lignite gasification biochemical wastewater, specifically 1‰, 2‰, 3‰, 4‰, or 5‰ in this embodiment; the volume of the organic flocculant solution is 0.5-3‰ of the volume of lignite gasification biochemical wastewater, specifically 1‰ in this embodiment; the flocculation treatment involves sequential stirring and settling; the stirring rate is 6... The speed is 00~800r / min, specifically 700r / min in this embodiment; the settling time is 30~120min, specifically 30min in this embodiment; after settling, the supernatant is taken for later use; the equipment used for flocculation treatment includes a flocculation reaction tank and a flocculation sedimentation tank; the lignite gasification biochemical wastewater and flocculant are mixed and stirred in the flocculation reaction tank; settling is carried out in the flocculation sedimentation tank, where solid-liquid separation is achieved to obtain the supernatant.

[0022] In one embodiment, the oxidant includes one or more of H2O2, persulfate, and periodate, specifically H2O2, persulfate, or periodate; the persulfate includes perdisulfate (PDS) and / or potassium permonosulfate complex salt (PMS), specifically potassium permonosulfate complex salt (PMS); the periodate includes potassium periodate (KIO4) and / or sodium periodate (NaIO4), specifically KIO4; the H2O2 is used in the form of an H2O2 solution; the mass fraction of the H2O2 solution is 30%. The volume of the H2O2 solution is 0.5-4‰ of the volume of the lignite gasification biochemical wastewater, specifically 0.5, 1, 1.5, 2, 2.5, 3, 3.5, or 4‰ in the specific embodiments; the concentration of H2O2 in the reaction solution is 4.9-38.8 mM, specifically 4.9, 9.7, 19.4, 29.1, or 38.8 mM in the specific embodiments; the concentration of persulfate is 10-50 mM, specifically 10, 20, 30, 40, or 50 mM in the specific embodiments; and the concentration of periodate is 5-40 mM, specifically 5, 10, 20, or 30 mM in the specific embodiments.

[0023] In one embodiment, the photocatalytic degradation reaction is carried out under far-ultraviolet light; the wavelength of the far-ultraviolet light is 185~365nm, specifically 254nm in this embodiment; the light source for the photocatalytic degradation reaction is a low-pressure ultraviolet lamp or a vacuum ultraviolet lamp (VUV); the light emitted by the low-pressure ultraviolet lamp is single-wavelength light with a wavelength of 254nm or 222nm; the power of the low-pressure ultraviolet lamp is 16~17W, specifically 17W in this embodiment; the wavelength of the light emitted by the vacuum ultraviolet lamp is 185nm; the photocatalytic degradation reaction is carried out under stirring conditions; the stirring rate is 300~500r / min, specifically 300r / min in this embodiment; the time of the photocatalytic degradation reaction is 60~240min, specifically 120min in this embodiment; during the photocatalytic degradation reaction, the ultraviolet lamp is placed in water and the ultraviolet light source is turned on.

[0024] Figure 1 This is a schematic diagram illustrating the process of treating lignite gasification biochemical wastewater using a UV-activated oxidant (H2O2, PMS, KIO4) system in an embodiment of the present invention. Figure 1 As shown, the biochemical wastewater from lignite gasification enters the flocculation reaction tank through the inlet, where polyaluminum sulfate and polyacrylamide are added for coagulation and flocculation. Subsequently, solid-liquid separation is achieved in the flocculation sedimentation tank, and the supernatant enters the advanced oxidation treatment tank for deep oxidation and degradation, ultimately achieving discharge in compliance with standards.

[0025] This invention belongs to the field of water treatment technology, specifically referring to the deep treatment of coal chemical wastewater. Specifically, it involves a homogeneous advanced oxidation technology based on ultraviolet (UV) activation of hydrogen peroxide (H2O2), persulfate (PMS), and potassium periodate (KIO4) for the deep removal of recalcitrant organic pollutants such as long-chain alkanes, anilines, and volatile phenols from lignite gasification biochemical wastewater. It can be adapted to existing wastewater treatment processes in coal chemical enterprises to achieve compliant discharge.

[0026] This invention utilizes ultraviolet light activation of H2O2 / PMS / KIO4 to deeply treat organic pollutants in lignite gasification biochemical wastewater, achieving the following technical effects: 1. Guarantee of compliant discharge: After treatment by three methods, the 300mL small-scale wastewater has a COD ≤ 80mg / L, color ≤ 10 times, and organic matter removal rate ≥ 90%, which fully meets the Class A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB 18918-2002), solving the problem of substandard biological effluent; 2. Shorter processing cycle: Total reaction time is 2-4 hours, significantly reducing the footprint of processing facilities and making it suitable for the site requirements of small and medium-sized enterprises; 3. Strong environmental adaptability: The COD removal rate fluctuates by less than 8% within the water temperature range of 5~40℃ and pH value of 3.0~9.0. No temperature control is required, and it can be adapted to coal chemical enterprises in different climate regions such as Inner Mongolia and Yunnan.

[0027] The key points of this invention are as follows: 1. This invention explores the different reaction mechanisms of three different systems for treating lignite gasification biochemical wastewater. The core mechanism of the UV / H2O2 system is photoactivation initiating homogeneous cracking of H2O2 to produce ·OH and broadly mineralizing pollutants. The UV / PMS system, on the other hand, is photo-driven PMS cracking to produce SO4· - Its ability to convert ·OH to form a dual radical synergistic oxidation process, and the clear mechanism of both provides support for process optimization; the core mechanism of the UV / KIO4 system is the photoexcitation of KIO4 to generate ·OH and 1 O2, targeted attack and broad-spectrum oxidation work together to adapt to complex water quality; 2. This invention found that the three systems show significant differences in water quality after degradation of lignite gasification biochemical wastewater, with obvious differences in pH value, color, and BOD5 / COD, effectively adapting to diverse application needs with different treatment objectives and process conditions.

[0028] 3.254nm far-ultraviolet lamp and H2O2 / PMS / KIO4 adaptation technology: Utilizing the high photon energy characteristics of 254nm lamp, it efficiently excites oxidants to generate active species, making it suitable for water quality with low biodegradability and highly recalcitrant pollutants; 4. Synergistic treatment technology for lignite gasification biochemical wastewater by composite flocculation pretreatment and ultraviolet light activation: Flocculation reduces color, solving the problem of poor ultraviolet light penetration in high-color wastewater and improving the utilization rate of activator; 5. Low-cost, highly adaptable, and efficient process parameter system: By optimizing the flocculant ratio, oxidant concentration, and reaction time, it is low-cost and adaptable to different water qualities.

[0029] This invention can optimize parameters by adjusting the flocculant ratio, oxidant concentration, and light source power according to the actual wastewater quality, such as COD, pH value, and types of characteristic pollutants, without requiring significant changes to the process equipment. This invention has strong compatibility with the existing "anaerobic + aerobic" biochemical process of coal chemical enterprises, and the pretreated flocculated sludge can be incorporated into the existing sludge treatment system without the need for new sludge disposal facilities. The stability of the process has been verified by pilot-scale experiments, and industrial parameters can be further optimized through pilot-scale testing.

[0030] The abbreviations in English and Chinese of this invention are shown in Table 1.

[0031] Table 1 English Abbreviations

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments thereof, but they should not be construed as limiting the scope of protection of the present invention.

[0033] Example 1 The effluent COD of the lignite gasification biochemical wastewater was 818.10 mg / L, with a color of 200 times and a pH of 7.5. The organic matter in the wastewater was non-degradable in the biochemical tank (BOD5 was 366 mg / L). This wastewater underwent flocculation treatment, using a 30% polyaluminum sulfate solution and a 0.5‰ PAM solution. The 30% polyaluminum sulfate solution was added in gradients of 1‰, 2‰, 3‰, 4‰, and 5‰ based on the volume fraction of the raw lignite gasification biochemical wastewater. The 0.5‰ PAM solution was added according to the volume fraction of the lignite gasification biochemical wastewater. Add 1‰ of the solution, stir vigorously at 700 r / min, and let it stand for 30 min to settle. After settling, take the supernatant to test the water quality indicators. Use raw lignite gasification biochemical wastewater with a volume fraction of 3‰ polyaluminum sulfate solution (mass fraction of 30%) and a mass fraction of 1‰ polyacrylamide solution (mass fraction of 0.5‰) for flocculation. The supernatant after flocculation is used for subsequent UV / H2O2, VU / PMS, and UV / KIO4 degradation. The water quality indicators of the supernatant are as follows: COD reduced to 340.25 mg / L, color reduced by 60 times, pH value of 6.5, which is within the neutral range.

[0034] The flocculation treatment achieved a COD removal rate of 58.04% for the wastewater. After the color decreased by 60 times, the light transmittance improved, paving the way for subsequent ultraviolet (UV) treatment. As the dosage of polyaluminum sulfate additive increased from 1‰ to 5‰, the wastewater COD concentration significantly decreased from approximately 642.68 mg / L to 300.93 mg / L, with the corresponding removal rate increasing from 21.44% to 63.22%, demonstrating the additive's effectiveness in degrading organic matter. However, while the COD removal effect improved, the wastewater pH value continuously decreased from neutral 7.5 to 5.5, indicating that while the additive improved treatment efficiency, it also caused significant acidification of the water body. The relationship between flocculant dosage, COD removal rate, and wastewater acidity needs to be coordinated.

[0035] Example 2 UV / H2O2 treatment of lignite gasification biochemical wastewater: The supernatant from Example 1 was used for treatment. H2O2 was added to the UV / H2O2 system, and a 17W 254nm single-wavelength ultraviolet lamp (low-pressure ultraviolet mercury lamp) was used for wastewater treatment.

[0036] In a small-scale experiment, 300 mL of the supernatant from Example 1 was transferred to a photoreactor. H₂O₂ (30% H₂O₂ solution) was added at volume fractions of 0.5‰, 1‰, 2‰, 3‰, and 4‰. An ultraviolet lamp was placed in the water, the ultraviolet light source was turned on, and the photoreaction was carried out at a stirring rate of 300 r / min for 120 min. Samples were taken every 30 min. Figure 4 As shown, after 2 hours of reaction, the degradation effects of 2‰, 3‰, and 4‰ were similar. Considering the cost, the dosage of UV / H2O2 was chosen to be 2‰. After 2 hours of treatment with 2‰ H2O2, the COD decreased to 28.73 mg / L, the color decreased by 2 times, the pH value after the reaction was 2.2, and the BOD5 / COD ratio was 0.04, indicating low biodegradability.

[0037] The core of the UV / H2O2 process is to use ultraviolet light to excite hydrogen peroxide to generate highly oxidizing hydroxyl radicals (·OH). These radicals degrade large-molecule organic pollutants into a series of small-molecule acidic intermediates. Because the treated water is acidic, acidic conditions are unfavorable for biological treatment, resulting in a lower BOD5 / COD ratio.

[0038] Example 3 UV / PMS treatment of lignite gasification biochemical wastewater: The supernatant from Example 1 was used for treatment. PMS (persulfate) or PDS (perdisulfate) was added to the UV / PMS system, and a 254nm single-wavelength UV lamp with a power of 17W was used in conjunction with the wastewater treatment.

[0039] For the small-scale experiment, 300 mL of the supernatant from Example 1 was transferred into the photoreactor and added at concentrations of 10, 20, 30, 40, and 50 mM. The ultraviolet lamp was placed in the water, the ultraviolet light source was turned on, and the photoreaction was carried out under the condition of a stirring rate of 300 r / min for 120 min. Samples were taken every 30 min.

[0040] like Figure 7 As shown, after 2 hours of reaction, the degradation effects of 30, 40, and 50 mM were similar. Considering the cost, the dosage of UV / PMS was chosen to be 30 mM. After 2 hours of treatment with 30 mM PMS, the COD decreased to 33.27 mg / L, the color decreased by 2 times, the pH value after the reaction was 6.9, and the BOD5 / COD ratio was 0.97, indicating high biodegradability.

[0041] Example 4 UV / KIO4 treatment of biochemical wastewater from lignite gasification: The supernatant from Example 1 was used for treatment. KIO4 was added to the UV / KIO4 system, and a 17W 254nm single-wavelength UV lamp was used in conjunction with the wastewater treatment.

[0042] For the small-scale experiment, 300 mL of the supernatant from Example 1 was transferred into the photoreactor and added at concentrations of 5, 10, 20, and 30 mM. The ultraviolet lamp was placed in the water, the ultraviolet light source was turned on, and the photoreaction was carried out under the condition of stirring rate of 300 r / min for 120 min. Samples were taken every 30 min.

[0043] like Figure 10 As shown, after 2 hours of reaction, the 30 mM concentration exhibited the best degradation effect. The optimal dosage for UV / KIO4 was 30 mM. After 2 hours of treatment with 30 mM KIO4, the COD decreased to 21.21 mg / L, the color decreased by 8 times, the post-reaction pH was 6.9, and the BOD5 / COD ratio was 0.92, indicating high biodegradability. Compared to UV / H2O2 and UV / PMS, this system exhibited higher color. During the reaction, the wastewater initially became clear and transparent before turning pale brownish-yellow. Starch testing confirmed the presence of elemental iodine in the post-reaction water, hence the higher color.

[0044] Comparative Example 1 The difference from Example 2 is that no ultraviolet light was added, and a 30% H2O2 solution with a volume fraction of 2‰ (19.58 mM) was added as a control. The specific steps were as follows: 300 mL of the supernatant from Example 1 was transferred to a reactor, and a 30% H2O2 solution with a mass fraction of 2‰ was added. The reaction was carried out at a stirring rate of 300 r / min for 90 min. After sampling, the COD of the liquid after the reaction was measured to be 579.17 mg / L. The reaction was continued for 120 min, and the COD of the liquid after the reaction was measured to be 562.54 mg / L. The COD of the liquid increased after the reaction. Comparison with the COD of the H2O2 solution revealed that the increase in COD was due to the incomplete depletion of H2O2.

[0045] Comparative Example 2 The difference from Example 3 is that no ultraviolet light was added, and 30 mM PMS was added as a control. The specific steps are as follows: 300 mL of the supernatant from Example 1 was taken and transferred to a reactor, 30 mM PMS was added, and the reaction was carried out at a stirring rate of 300 r / min for 90 min. After sampling, the COD of the liquid after the reaction was measured to be 337.22 mg / L. The reaction was continued for 120 min, and the COD of the liquid after the reaction was measured to be 305.46 mg / L.

[0046] Comparative Example 3 The difference from Example 4 is that no ultraviolet light was added, and 30 mM KIO4 was added as a control. The specific steps are as follows: 300 mL of the supernatant from Example 1 was taken and transferred to a reactor, and 30 mM KIO4 was added. The mixture was reacted for 90 min at a stirring rate of 300 r / min. After sampling, the COD of the liquid after the reaction was measured to be 222.29 mg / L. The reaction was continued for 120 min, and the COD of the liquid after the reaction was measured to be 152.73 mg / L.

[0047] Performance testing Water quality index testing and effect verification: Colorimetric determination was performed according to the national standard method (GB / T5750.4-2023 Standard Examination Methods for Drinking Water Part 4: Sensory Characteristics and Physical Indicators), using an ultraviolet-visible spectrophotometer to measure absorbance at a wavelength of 436 nm; COD determination followed the "Determination of Chemical Oxygen Demand in Water - Dichromate Method" (HJ828-2017), a standard curve was plotted, and the COD value was calculated according to the formula; BOD5 determination was performed according to the "Determination of Five-Day Biochemical Oxygen Demand (BOD5) in Water - Dilution and Inoculation Method" (HJ 505-2009), after water sample dilution, it was incubated at 20±1℃ in the dark for 5 days, and the dissolved oxygen difference was measured to calculate BOD5; Characteristic pollutants were tested using high performance liquid chromatography-mass spectrometry (HPLC-MS / MS) and gas chromatography-mass spectrometry (GC-MS).

[0048] (1) Figure 2 The graph shows the test results of pH value, COD concentration and COD removal rate of the supernatant obtained from flocculation treatment under different amounts of polyaluminum sulfate flocculant added in Example 1.

[0049] like Figure 2 As shown, with increasing dosage of polyaluminum sulfate flocculant, the COD of the wastewater showed a significant decreasing trend. Within the range of 2-5‰, further increases in dosage maintained a high removal rate with slight fluctuations. Simultaneously, the pH value gradually decreased from the alkaline state of the raw water to the acidic range. These results indicate that appropriate dosage can effectively reduce COD concentration and regulate pH.

[0050] (2) Figure 3 The bar chart shows three parallel COD degradation curves obtained in Example 2 under different concentrations of H2O2 activated by 254nm UV lamp. This bar chart reveals the influence of H2O2 addition on COD removal rate.

[0051] like Figure 3 As shown, the COD removal rate showed a significant upward trend as the H2O2 addition increased from 0.5‰ to 4‰, with removal rates of 29.9%, 49.3%, 88.9%, 88.6%, and 93.2%, respectively. When the addition reached 2‰, the removal rate had increased to 88.9%; continuing to increase to 4‰, the removal rate remained at a high level of 93.2%.

[0052] (3) Figure 4 The figure shows the COD removal rate of three parallel treatments at different concentrations of H2O2 activated by 254nm UV lamp obtained in Example 2. This figure illustrates the change of COD over time during treatment with different concentrations of H2O2.

[0053] like Figure 4 As shown, COD in all systems initially increased briefly, possibly due to incomplete depletion of H2O2; subsequently, COD gradually decreased over time, indicating continuous degradation. Higher concentrations of H2O2 (3‰, 4‰) reduced COD to 20–30 mg / L after 120 min, demonstrating significantly better removal efficiency than the low-concentration group. This result indicates that appropriately increasing the H2O2 dosage and ensuring sufficient reaction time can achieve efficient and deep oxidation of organic matter.

[0054] (4) Figure 5 This is an electron paramagnetic spectrum (EPR) of H2O2 activated by a 254 nm UV lamp obtained in Example 2. This EPR spectrum characterizes the free radical species generated in the UV / H2O2 system, demonstrating that UV excitation can effectively promote the decomposition of H2O2 to produce ·OH and ·OOH. - Together, they contribute to the efficient oxidative degradation of organic matter.

[0055] (5) Figure 6The image shows three parallel COD degradation curves obtained in Example 3 under different concentrations of PMS activated by 254nm UV lamp, presenting the COD degradation curves over time under different amounts of PMS (persulfate).

[0056] like Figure 6 As shown, within the concentration range of 10–50 mM, COD continuously decreased with increasing reaction time, indicating that the PMS system can effectively degrade organic matter in water. Higher PMS additions, such as 40 mM and 50 mM, exhibited faster COD removal rates and lower final residual concentrations at the same time points.

[0057] (6) Figure 7 The image shows three parallel COD removal rate graphs obtained in Example 3 under different concentrations of PMS activated by 254nm UV lamp; it illustrates the effect of different PMS (persulfate) addition amounts on COD removal rate.

[0058] like Figure 7 As shown, the COD removal rate showed a significant upward trend as the PMS concentration increased from 10 mM to 50 mM, with removal rates of 58.4%, 74.4%, 90.3%, 94.4%, and 94.8%, respectively. When the PMS concentration reached 40 mM, the removal rate was as high as 94.4%. Further increasing to 50 mM, the removal rate only increased to 94.8%, indicating that the improvement slowed down after 40 mM.

[0059] (7) Figure 8 This is an electron paramagnetic plot of the 254nm UV lamp activated PMS obtained in Example 3. This EPR plot characterizes the free radical species generated in the UV / PMS system.

[0060] from Figure 8 SO4· is clearly visible in the spectrum. - The presence of ·OH demonstrates that UV excitation can effectively promote the decomposition of PMS to produce ·OH and SO4· - Together, they contribute to the efficient oxidative degradation of organic matter.

[0061] (8) Figure 9 The three parallel COD degradation diagrams obtained in Example 4 under different concentrations of KIO4 activated by 254nm UV lamp reveal the degradation trend of COD with reaction time under different KIO4 addition amounts.

[0062] like Figure 9 As shown, the COD of all systems decreased over time, and the higher the initial concentration, the faster the degradation rate.

[0063] (9) Figure 10 The image shows the COD removal rates of three parallel trials at different concentrations of KIO4 activated by 254nm UV lamps obtained in Example 4.

[0064] like Figure 10 As shown, the COD removal rate increased significantly from 5 mM to 30 mM, with values ​​of 52.5%, 64.2%, 70.9%, and 92.6%, respectively. The removal rate was highest (92.6%) when the concentration reached 30 mM, indicating that increasing the KIO4 dosage can effectively improve oxidation efficiency.

[0065] (10) Figure 11 This is a diagram of the electron paramagnetic technique for activating KIO4 with a 254nm ultraviolet lamp obtained in Example 4.

[0066] like Figure 11 As shown, singlet oxygen was generated in the system. 1 O2), which is the main non-radical reactive species generated by the photolysis of KIO4. Simultaneously, experiments using DMPO as a scavenger showed the generation of hydroxyl radicals (·OH). Comparison of different solvent environments indicates that hydroxyl radicals (·OH) coexist in the UV / KIO4 system. 1 O2-dominated non-radical pathways and ·OH-involved radical pathways.

[0067] (11) Figure 12 The graph shows the colorimetric values ​​of the raw water, the supernatant obtained from flocculation treatment, and the reaction solutions after treatment in Examples 2 (H2O2 added at a volume fraction of 2‰), 3 (PMS added at a concentration of 30 mM), and 4 (KIO4 added at a concentration of 30 mM). The graph compares the colorimetric values ​​of different water samples. H2O2 represents Example 2, PMS represents Example 3, and KIO4 represents Example 4.

[0068] like Figure 12 As shown, the raw water had the highest color intensity, reaching 200.00 times; the color intensity of the supernatant after preliminary treatment decreased to 60.00 times; and after deep treatment by UV-assisted advanced oxidation processes (AOPs), the color intensity of all systems was significantly reduced. Among them, the UV / H2O2 and UV / PMS processes had the best decolorization effect, with an effluent color intensity of only 2.00 times; the UV / KIO4 process had an effluent color intensity of 8.00 times, and experiments showed that a small amount of elemental iodine was generated, but it still exhibited good decolorization performance.

[0069] (12) Figure 13 This is a bar chart showing the pH values ​​of raw water, supernatant obtained from flocculation treatment, and reaction solutions after treatment in Examples 2 (H2O2 volume fraction of 2‰), 3 (PMS addition amount of 30mM), and 4 (KIO4 addition amount of 30mM). This bar chart compares the final pH values ​​of the reaction system under different treatment conditions, where H2O2 represents Example 2, PMS represents Example 3, and KIO4 represents Example 4.

[0070] like Figure 13As shown, after treatment with various oxidants, the pH value changed to varying degrees compared to the raw water. The lowest pH value (2.20) was observed after PMS treatment, indicating strong acidity; KIO4 treatment resulted in a pH of 6.90, indicating weak acidity; and H2O2 treatment resulted in a pH of 7.50, close to neutral. The pH value of the supernatant (8.30) was close to that of the raw water. The results indicate that different oxidants significantly affect the pH value of the reaction system, with PMS treatment causing the most significant acidification. Compared to the traditional Fenton process, which relies on large amounts of chemical reagents and generates a large amount of iron-containing sludge leading to secondary pollution, and requires adding concentrated sulfuric acid to lower the wastewater pH to a specified range and then adding alkaline agents such as sodium hydroxide to neutralize it after the reaction, this process not only consumes large amounts of acid and alkali reagents but also generates high energy consumption due to the continuous operation of the adjustment equipment. In contrast, the UV / H2O2 system does not produce net H2O through H2O photolysis itself. + The pH value after the reaction is close to neutral, with little change in acidity or base compared to the traditional Fenton process, making it more environmentally friendly. KIO4 produces an acidic product after the reaction, with little change in pH value compared to the supernatant. However, PMS may directly generate a large amount of H2 during photoactivation. + Furthermore, its final product, sulfate ions, forms a strong acid, which together triggers severe acidification of the system.

[0071] (13) Figure 14 The BOD5 / COD ratios of the raw water, the supernatant obtained from flocculation treatment, and the reaction solutions after treatment in Examples 2 (H2O2 volume fraction of 2‰), 3 (PMS addition of 30mM), and 4 (KIO4 addition of 30mM) were compared to show the changes in the biodegradability (BOD5 / COD) of wastewater treated by UV synergistic with different oxidants. H2O2 represents Example 3, PMS represents Example 4, and KIO4 represents Example 5.

[0072] like Figure 14 As shown, compared to the raw water (0.44), the UV / H2O2 and UV / KIO4 ratios after treatment significantly increased, reaching 0.92 and 0.97 respectively, indicating that the oxidation pathway can effectively convert pollutants into easily biodegradable small molecules. However, the UV / PMS ratio after treatment dropped sharply to 0.04, directly related to its extremely low effluent pH of 2.20. The strongly acidic environment severely inhibits microbial activity, and some intermediate products generated by PMS oxidation, such as those containing sulfonic acid groups, have stable structures and are difficult for organisms to utilize.

[0073] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for deep treatment of organic pollutants in lignite gasification biochemical wastewater using a far-ultraviolet light-activated oxidant, characterized in that, Includes the following steps: The lignite gasification biochemical wastewater and oxidant are mixed, and the resulting reaction solution is subjected to photocatalytic degradation reaction to obtain effluent; The oxidant includes one or more of H2O2, persulfate, and periodate; The photocatalytic degradation reaction is carried out under far-ultraviolet light.

2. The method according to claim 1, characterized in that, When the color of the lignite gasification biochemical wastewater is ≥100 times, before mixing the lignite gasification biochemical wastewater and the oxidant, the process further includes: mixing the lignite gasification biochemical wastewater and the flocculant for flocculation treatment, and then mixing the resulting supernatant with the oxidant.

3. The method according to claim 1, characterized in that, The persulfate includes perdisulfate and / or potassium permonosulfate complex salt.

4. The method according to claim 1, characterized in that, The periodate includes potassium periodate and / or sodium periodate.

5. The method according to claim 2, characterized in that, The flocculant includes inorganic flocculants and organic flocculants; the inorganic flocculant is polyaluminum sulfate and / or polyaluminum chloride; the organic flocculant is polyacrylamide and / or cationic polyacrylamide.

6. The method according to claim 1, characterized in that, The wavelength of the far-ultraviolet light is 185~365nm.

7. The method according to claim 1, characterized in that, The photocatalytic degradation reaction takes 60 to 240 minutes.

8. The method according to claim 1 or 3, characterized in that, The concentration of persulfate in the reaction solution is 10~50mM.

9. The method according to claim 1 or 4, characterized in that, The concentration of periodate in the reaction solution is 5~40mM.

10. The method according to claim 1, characterized in that, The concentration of H2O2 in the reaction solution is 4.9~38.8mM.

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