Detoxification method for treating eucalyptus chemical-mechanical pulping wastewater

Abstract

The present invention discloses a detoxification method for treating eucalyptus chemimechanical pulping wastewater. By using biochar / Bi2MoO6 composite material as a catalyst to construct an ICPB system to detoxify eucalyptus chemimechanical pulping wastewater, the method provides theoretical and technical reference for solving the problem of efficient treatment of difficult-to-biodegrade wastewater in pulping enterprises.

Description

Technical Field

[0001] The invention relates to the treatment of eucalyptus chemimechanical pulping wastewater, and in particular to a detoxification method for treating eucalyptus chemimechanical pulping wastewater. Background Art

[0002] Eucalyptus is one of the important fast-growing tree species in my country. It has the advantages of short growth cycle, good fiber morphology and strong adaptability. It has become an important fiber raw material for chemical mechanical pulping in my country. [1-3] The vigorous development of eucalyptus chemimechanical pulping is of great significance to the healthy and sustainable development of my country's papermaking industry. However, the wastewater generated during the eucalyptus chemimechanical pulping process has poor biodegradability and is difficult to biodegrade, which has become a major industrial problem that needs to be urgently addressed in my country's eucalyptus chemimechanical pulping industry.

[0003] Eucalyptus chemical pulping wastewater has a complex composition and contains a large amount of lignin, hemicellulose, tannins, organic acids and other difficult-to-biodegrade organic matter, resulting in poor biological treatment effect of eucalyptus chemical pulping wastewater. Huang Zaiheng et al. (Huang Zaiheng, Qin Xiang, Liu Xi, et al. Multi-component composition analysis of eucalyptus chemical pulping wastewater [J]. China Papermaking, 2022, 41(06): 64-70) analyzed the components of eucalyptus chemical pulping wastewater and found that the lignin content in the wastewater was as high as 73g / L, which is 1.2 times that of poplar chemical pulping wastewater. It also contains more than 40 other organic pollutants. After anaerobic treatment, COD Cr The removal rate is 59.16%. The biochemical treatment efficiency of eucalyptus chemical pulp wastewater is low, mainly because the wastewater contains toxic substances that inhibit the survival of microorganisms. According to research, the anaerobic and aerobic biological treatment sections of eucalyptus chemical pulp wastewater have a COD Cr The removal rates were 59.10% and 64.40% respectively, and the wastewater after treatment still contained a large amount of organic matter such as butylated hydroxytoluene and phenols (Ran Miao. Biochemical-photocatalytic treatment technology and mechanism of eucalyptus P-RC APMP wastewater [D]. Chinese Academy of Forestry, 2021). The detoxification treatment of eucalyptus chemical mechanical pulp wastewater has become a research hotspot in the field of wastewater treatment. Huang Zaiheng et al. (Huang Z, Qin X, Zhu T, et al. Developing an Efficient Processing System Treatment for the High Concentration of Eucalyptus Chemical Mechanical Pulp Wastewater [J]. Molecules, 2022, 27 (18): 5774) developed a "chlorine dioxide pretreatment-anaerobic" combined process to treat eucalyptus chemical mechanical pulp wastewater. The study found that COD CrThe removal rate is 88.29%, which is 29.13% higher than that of ordinary anaerobic treatment. This is mainly because chlorine dioxide pretreatment removes toxic substances in eucalyptus chemical-mechanical pulping wastewater, improves the biodegradability of wastewater, and promotes the proliferation and growth of anaerobic bacteria.

[0004] In recent years, the direct coupling of photocatalytic oxidation and biodegradation (ICPB) technology has shown promising application prospects in the degradation of recalcitrant and poorly biodegradable organic pollutants, combining the advantages of rapid photocatalytic degradation and microbial metabolism. Photocatalytic oxidation in the ICPB system can convert poorly biodegradable organic matter in wastewater into biodegradable intermediates. These intermediates are then consumed and degraded by the microorganisms in the system as carbon sources, achieving efficient degradation of recalcitrant organic matter in wastewater.

[0005] Photocatalysts are an important component of the ICPB system and directly affect the degradation performance of the system. There are no reports in the prior art on the detoxification of eucalyptus chemical-mechanical pulping wastewater using ICPB combined with biochar-based materials. Summary of the Invention

[0006] Purpose of the invention: The technical problem to be solved by the present invention is to address the deficiencies of the existing technology and provide a detoxification method for treating eucalyptus chemimechanical pulping wastewater. By using biochar / Bi2MoO6 composite material as a catalyst to construct an ICPB system to detoxify eucalyptus chemimechanical pulping wastewater, it provides theoretical and technical reference for solving the problem of efficient treatment of difficult-to-biodegrade wastewater in pulping enterprises.

[0007] In order to solve the above technical problems, the present invention discloses a detoxification method for treating eucalyptus chemical-mechanical pulping wastewater, comprising the following steps:

[0008] (1) loading the lignin charcoal / Bi2MoO6 catalyst onto a polyurethane sponge carrier, then placing the catalyst-loaded polyurethane sponge carrier into acclimated aerobic sludge, aerating it, completing the activated sludge inoculation, and obtaining an inoculated polyurethane sponge carrier;

[0009] (2) In a dark environment, the inoculated polyurethane sponge carrier is placed in a fluidized bed reactor and a biofilm is cultured using an SBR process to obtain a polyurethane sponge carrier loaded with a catalyst and a biofilm;

[0010] (3) placing the polyurethane sponge carrier loaded with the catalyst and the biofilm in an internal circulation reactor to construct a photocatalytic oxidation-biodegradation direct coupling system;

[0011] (4) The anaerobic effluent from the eucalyptus chemical-mechanical pulp was added to the internal circulation reactor of the photocatalytic oxidation-biodegradation direct coupling system for treatment. During the treatment process, the experimental temperature and dissolved oxygen were controlled at 25±1°C and 4±0.5 mg / L, and the light source was an LED lamp.

[0012] The lignin charcoal / Bi2MoO6 catalyst is loaded onto a polyurethane sponge carrier by the following method:

[0013] 1) The catalyst lignin charcoal / Bi2MoO6 is placed in a container filled with anhydrous ethanol, stirred, and then ultrasonicated to obtain a suspension. The polyurethane sponge carrier is placed in the suspension and stirred. During the above process, the container opening is sealed;

[0014] 2) The container opening in step (1) is unsealed and placed on a magnetic stirrer at 60-70° C. to stir the ethanol completely, and the catalyst-loaded polyurethane sponge is placed in an oven for drying. The carrier obtained after drying is first washed with distilled water and then ultrasonicated, and then washed with distilled water again to remove the catalyst that is not firmly loaded. Finally, it is placed in an oven for drying to constant weight to obtain a catalyst-loaded sponge carrier.

[0015] Specifically, the polyurethane sponge carrier is in the shape of a 7 mm ± 0.5 mm cube, and the ratio of catalyst mass, anhydrous ethanol volume, and carrier mass is 1:20 to 150:2. Preferably, when the ratio of catalyst mass, anhydrous ethanol volume, and carrier mass is 1:100:2, the catalyst loading rate is the highest.

[0016] In step (2), the obtained catalyst-loaded sponge carrier is put into aerobic sludge and aerated for 20-24 hours to complete the activated sludge inoculation. The inoculated sponge carrier is placed in a fluidized bed reactor and a biofilm is cultured using the SBR process.

[0017] Among them, in the process of cultivating biofilm, according to COD Cr :N:P=200:5:1 ratio to prepare the experimental culture solution required for biofilm formation. During the biofilm culture process, the water temperature was maintained at 25±1℃, the dissolved oxygen content was controlled at 4±0.5mg / L, and the culture solution was changed every 12h. The COD Cr Stable, biofilm culture completed.

[0018] Preferably, before the treatment in step (4), an anaerobic effluent stabilization system for eucalyptus chemical-mechanical pulp is used.

[0019] The present invention further proposes a method for treating wood chemimechanical pulping wastewater, that is, using the above method to perform detoxification treatment, and then further treating the eucalyptus chemimechanical pulping wastewater obtained after the treatment by using Fenton oxidation method.

[0020] Beneficial effect: Compared with the existing technology, the photocatalytic oxidation and microbial degradation in the ICPB method used in this application have good synergistic effect, which can significantly improve the aerobic treatment effect of eucalyptus chemical mechanical pulping wastewater and reduce the amount of Fenton reagent used in the deep treatment process. Cr The removal rate increased from 46.66% to 74.34%. In the subsequent deep treatment, when the dosage of H2O2 (15wt%) and FeSO4 (30wt%) was 1.5mL / L and 7.5mL / L respectively, the COD Cr It can be reduced to 41 mg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0022] Figure 1 This is a schematic diagram of the ICPB internal circulation experimental device;

[0023] Figure 2 The treatment effects of different systems on anaerobic effluent from eucalyptus chemical-mechanical pulping (B: biodegradation; ICPB: direct coupling of photocatalytic oxidation and biodegradation; AD: adsorption; P: photolysis; PC: photocatalysis);

[0024] Figure 3 BOD5 / COD in different reaction time periods in biological treatment and ICPB treatment systems Cr ratio (a) and the loading amount of microorganisms on the carrier (b);

[0025] Figure 4 Scanning electron micrographs of different sponge carriers, including: carrier (a), carrier loaded with catalyst (b), carrier loaded with catalyst and biofilm (c), carrier (d), outer (e) and inner (f) surface biofilms in the biological treatment system, carrier (g), outer (h) and inner (i) surface biofilms in the ICPB system;

[0026] Figure 5 Comparison of phylum-level community distribution between biological treatment and ICPB system (a), detailed colony proportion distribution diagrams (bc) of biological treatment (b) and ICPB system (c). DETAILED DESCRIPTION

[0027] The present application is described in detail below through specific embodiments.

[0028] In the following examples, the experimental wastewater was derived from the pilot plant wastewater of P-RC APMP pulping of Eucalyptus grandis. The pollution indexes of the eucalyptus chemical-mechanical pulping wastewater were tested, and the results are shown in Table 1.

[0029] Table 1 Pollutant characteristics of eucalyptus P-RC APMP wastewater

[0030]

[0031] As can be seen from the table, when the alkali dosage of eucalyptus chemical mechanical pulp is 65kg / ton pulp and the hydrogen peroxide dosage is 70kg / ton pulp, the COD of the comprehensive wastewater of eucalyptus chemical mechanical pulp is Cr The amount of generated is 164.90kg / ton of pulp, and the BOD5 is 49.63kg / ton of pulp. Cr The ratio is 0.301, making it biodegradable wastewater. Furthermore, eucalyptus chemical-mechanical pulping wastewater contains high levels of fine fibers and extractables, resulting in high SS and TS levels in wastewater from various pulping stages. Therefore, fine fiber recovery should be considered during wastewater treatment, both to achieve fiber reuse and reduce wastewater treatment pressure.

[0032] Since the SS and TS contents in the eucalyptus chemical-mechanical pulping wastewater are high, which affects the biochemical efficiency in the treatment process, it was first filtered with a filter (300 mesh) and the filtered water samples were used for subsequent research. Cr It is 6273 mg / L, TS is 4.32 g / L, and SS is 0.67 g / L.

[0033] Example 1 Preparation of polyurethane sponge carrier loaded with catalyst and biofilm.

[0034] The lignin charcoal / Bi2MoO6 catalyst was prepared with reference to the method disclosed in CN 202211407803X, and LM10 (10wt% LC / Bi2MoO6) with the best adsorption and photocatalytic properties was used. It was loaded onto the polyurethane sponge by the co-impregnation method. Specifically as follows: 1g of the catalyst was placed in 100mL of anhydrous ethanol, stirred vigorously for 8h and then ultrasonicated for 2h to make the catalyst evenly dispersed in anhydrous ethanol. 2g (220±10) of 7mm cubic polyurethane sponge carrier (hydrophilic type, Jiangsu Yunhuan Environmental Protection Co., Ltd., the carrier specific surface area is greater than 4000m 2 / m 3 , porosity is 98%) is put into above-mentioned suspension, vigorously stirred 12h.The whole process is sealed with Parafilm sealing film beaker, prevents the volatilization of ethanol in stirring and ultrasonic process.Then beaker is placed on 70 ℃ of magnetic stirrers while stirring ethanol volatilization, in order to make catalyst can be evenly loaded on the carrier surface, when ethanol volume is less, use glass rod to continue stirring, until ethanol volatilizes completely.The sponge carrier of loaded catalyst is put into 80 ℃ of baking ovens and dry, after drying, the carrier is ultrasonicated to remove the catalyst that loads is not firm, finally put into baking oven and dry to constant weight, obtain the polyurethane sponge carrier of loaded catalyst.

[0035] The catalyst-loaded sponge carrier was put into aerobic sludge (from a paper mill in northern Jiangsu) and aerated for 24 hours to complete the activated sludge inoculation. The inoculated sponge carrier was placed in a fluidized bed reactor and the biofilm was cultured using the SBR process. The specific device is as follows: Figure 1 As shown. The ICPB reactor is made of quartz glass and consists of a hollow cylinder with an effective volume of 540mL, an inner diameter of 70mm, an outer diameter of 75mm, and a column height of 180mm. A 40mm circular aeration plate is installed at the bottom of the reactor to provide the oxygen required for the aerobic process. According to COD Cr :N:P=200:5:1 ratio to prepare the experimental culture medium required for biofilm formation. During the biofilm cultivation process, the water temperature was maintained at 25±1℃, the dissolved oxygen content was controlled at 4±0.5mg / L, and 500mL of culture medium was replaced every 12h. In order to prevent the catalyst from damaging the biofilm under light conditions, the reactor should be placed in a dark environment. The COD of the inlet and outlet water was measured every 24h. Cr The changes of COD in the effluent were monitored and the growth of biofilm was observed under a microscope. Cr Basically stable, at this time the biofilm culture is basically completed, and a large amount of biofilm is attached to the inside and outside of the sponge carrier.

[0036] Example 2: The ICPB system treats the anaerobic effluent from eucalyptus chemical-mechanical pulp.

[0037] The anaerobic effluent from the eucalyptus pulp was fed into an internal circulation reactor containing a biofilm-bearing sponge carrier. Because the microorganisms needed to gradually adapt to the anaerobic effluent treatment environment, 250 mL of anaerobic effluent was exchanged every 12 hours for the first week. Once the system stabilized, the corresponding ICPB experiments were conducted.

[0038] use Figure 1 The ICPB experiment was conducted using the device shown above. The light source used was a 60W LED lamp (Royal Philips, The Netherlands). During the experiment, 500 mL of anaerobic effluent from the eucalyptus chemical-mechanical pulp was replaced each time. The experimental temperature and dissolved oxygen were controlled at 25 ± 1°C and 4 ± 0.5 mg / L. After 24 hours, samples were taken to measure the COD content of the anaerobic effluent. Cr In order to solve the problem of poor aerobic treatment effect of eucalyptus chemical-mechanical pulping wastewater, the ICPB technology was first used to detoxify the eucalyptus chemical-mechanical pulping wastewater. The blank groups of adsorption (AD), photolysis (P), photocatalytic oxidation (PC) and biodegradation (B) were used as control experiments to study the detoxification mechanism of ICPB.

[0039] Table 2 ICPB system comparative experimental operating conditions

[0040]

[0041] The corresponding experimental results are as follows Figure 2 As shown in the figure, each reaction system has fluctuations at the beginning of the experiment, so the stable experimental data after 3 cycles are selected for analysis.

[0042] Depend on Figure 2 It can be seen that the anaerobic treatment effect of eucalyptus chemical mechanical pulping effluent is not obvious in the single adsorption and photolysis system. Cr The removal rate is basically below 5%. Compared with the activated sludge aerobic treatment process, the biofilm loaded with sponge carrier has a better effect on the COD removal of eucalyptus chemical mechanical pulping wastewater. Cr The removal effect is basically the same. After 24 hours of aeration, the COD Cr The removal rate was 46.67%. In the single photocatalytic reaction, after 24 hours of photocatalytic reaction of lignin carbon / Bi2MoO6, the COD content of anaerobic effluent from eucalyptus chemical mechanical pulping was Cr The removal rate was 28.56%, which may be related to the dark color of the wastewater and the high content of pollutants. It can be seen that the use of separate photocatalytic oxidation technology and biodegradation technology to treat eucalyptus chemical-mechanical pulping wastewater has certain limitations. However, when photocatalytic oxidation is directly coupled with microbial degradation (i.e. ICPB), the treatment effect of the system on the anaerobic effluent of eucalyptus chemical-mechanical pulping is significantly improved. After 24 hours of reaction, COD Cr Reduced to 547mg / L, COD Cr The removal rate reached 74.34%. In the ICPB system, photocatalytic oxidation and biodegradation exhibited excellent synergy. Due to the shear force of the water flow and the influence of photocatalytically active species, the sponge carrier skeleton exposed more photocatalysts. Under light conditions, the lignin charcoal / Bi2MoO6 catalyst produced a large amount of oxidizing species such as OH and holes, which degraded recalcitrant pollutants into biodegradable intermediates. These intermediates were quickly degraded and consumed by the microorganisms in the system as carbon sources. This process not only promoted the growth and reproduction of microorganisms, but also avoided competition between intermediates and active species, allowing more active free radicals to oxidatively degrade recalcitrant pollutants in eucalyptus chemical-mechanical pulping wastewater.

[0043] BOD5 / COD ratio of eucalyptus chemical-mechanical pulping wastewater in biological treatment and ICPB treatment systems Cr The ratio and the load of microorganisms in the carrier were determined (see Figure 3 ).Depend on Figure 3 a It can be seen that in the biological treatment system, with the increase of reaction time, the BOD5 / COD Cr The ratio is gradually decreasing from the initial 0.313 to 0.286, indicating that the biochemical performance of eucalyptus chemical-mechanical pulping wastewater is gradually deteriorating during the aerobic biological treatment process.Cr The ratio first increased and then decreased, but was higher than that of the initial wastewater. After 12h and 24h of reaction, the BOD5 / COD ratio of the wastewater was Cr The ratios increased from the initial 0.313 to 0.369 and 0.338, respectively, indicating that the biochemical properties of eucalyptus chemical-mechanical pulping wastewater were improved in the ICPB system. Figure 3 b shows that the microbial load in the carrier decreased in the biological treatment system, while the microbial load increased in the ICPB treatment system, which can also be verified by the subsequent microbial growth (SEM). Figure 3 It can be seen that in the photocatalytic process in the ICPB system, stubborn or highly toxic organic pollutants can be degraded into biodegradable intermediates, which improves the biochemical properties of wastewater, thereby improving the subsequent microbial degradation efficiency and promoting the growth and reproduction of microorganisms.

[0044] In order to study the growth of biofilm under different systems, the sponge carrier was observed by SEM (see Figure 4 ).Depend on Figure 4 a It can be seen that the macropores and micropores in the single carrier are combined, and the surface of the internal support structure is smooth. When the catalyst is loaded ( Figure 4 b), the inner and outer surfaces of the carrier are relatively rough, and a large amount of catalyst is evenly distributed and attached to the sponge carrier, which is not only conducive to the oxidative degradation of the photocatalyst under light, but also conducive to the subsequent growth and domestication of microorganisms. When the sponge carrier loaded with catalyst is inoculated with biofilm ( Figure 4 c) Biofilms adhere to the inner and outer surfaces of the sponge carrier, and the content of biofilms inside the carrier is much greater than that outside the carrier. Figure 4 (df) is the distribution of biofilm on the carrier in the biological treatment system. It can be seen that the biofilm on the inner and outer surfaces of the sponge carrier has severe shedding phenomenon, and only a small amount of biofilm covers the surface of the carrier. This is mainly because the anaerobic effluent of eucalyptus chemical-mechanical pulp contains toxic substances that are not conducive to the survival of microorganisms, causing a large number of microorganisms to die and fall off due to the shear force of the water flow. The ICPB system ( Figure 4 ei) The content of biofilm on the carrier increases significantly, and a large amount of biofilm is loaded inside the carrier; due to the influence of water shear force and photocatalytic free radicals, the outer surface of the carrier is smooth and a large amount of photocatalyst is exposed, which is conducive to the photocatalytic degradation of highly toxic and stubborn pollutants.

[0045] Table 3 Biodiversity index in biological treatment and ICPB systems

[0046]

[0047] Table 3 shows the biodiversity indices in biological treatment and ICPB systems. Biological alpha diversity can evaluate the abundance and diversity of microbial communities within the system. Shannon, Simpson, Ace, Chao, and Coverage indices are generally selected as commonly used indices. Among them, Chao and Ace indices can reflect the richness of biological communities, Shannon and Simpson indices can reflect the diversity of biological communities, and Coverage index is used to evaluate the coverage of sample libraries. The larger the Chao index and Ace index, the greater the richness of the microbial community; while the larger the Shannon index and the smaller the Simpson index, the higher the community biodiversity. As can be seen from the table, the Coverage index of the tested samples is above 99.8%, indicating that high-throughput sequencing can represent the main characteristics of the distribution of microbial colonies. The Chao, Ace and Shannon indices in the ICPB system were higher than those in the biological treatment system, and the Simpson index was lower than that in the biological treatment system, indicating that the richness and diversity of the biological colonies in the ICPB system were greater than those in the biological treatment system. This was mainly because the ICPB system could convert highly toxic pollutants in eucalyptus chemical-mechanical pulping wastewater into low-toxic and easily degradable small-molecule intermediates, reducing the toxicity of the wastewater and thus reducing the degree of damage to the biofilm inside the carrier; while in the biological system, microorganisms directly treated the highly toxic eucalyptus chemical-mechanical pulping wastewater, and it was difficult for the microorganisms to adapt. Only a small number of highly adaptable microorganisms survived, and most of the microbial bacteria were eliminated, resulting in a decrease in the richness and diversity of the microbial community.

[0048] Figure 5 The distribution of biological colonies at the phylum level in the biological treatment and ICPB systems. As can be seen from the figure, the biological colonies in the biological treatment system are mainly composed of Proteobacteria (36.81%), Actinobacteria (33.86%) and Cyanobacteria (25.43%), while other bacteria are relatively few and the colonies are relatively single. In contrast, the biological colonies in the ICPB system are diverse, with Proteobacteria and Actinobacteria still being the dominant species, and the contents of other species have increased. Compared with the biological treatment system, the abundance of Patescibacteria, Chloroflexi and Bacteroidota in the ICPB system have all increased significantly. The reduction or disappearance of other phyla indicates that the microorganisms in these phyla cannot adapt to the harmful environment and gradually die. The increase or appearance of bacterial phyla indicates that the colonies can adapt to the environment and reproduce and grow. [19,20] Related studies have reported that Proteobacteria, Actinobacteria, Patellar bacteria and Bacteroidetes have the ability to degrade polycyclic aromatic hydrocarbons in wastewater. [21,22]At the same time, the patellar bacteria can participate in the circulation of N, S and iron, and can also participate in nitrite detoxification [7] In summary, the ICPB system contained a wide variety of microbial colonies and a high relative abundance of specific species, further demonstrating that the direct photocatalytic-biological coupling system can convert highly toxic and difficult-to-biodegrade pollutants into low-toxic and easily degradable intermediates, thereby reducing or avoiding the damage of bioinhibitors to the microbial colonies in the system.

[0049] Example 3: Deep treatment of eucalyptus chemical-mechanical pulping wastewater.

[0050] Table 4 COD in eucalyptus chemical-mechanical pulping wastewater after biological and ICPB treatment by Fenton method Cr Comparison of degradation performance

[0051]

[0052] The eucalyptus chemical-mechanical pulping wastewater after biological treatment and ICPB treatment was treated with the Fenton oxidation process. The relevant data are shown in Table 4. In previous studies, it was found that the optimal reaction conditions for the Fenton process to treat this wastewater were: pH 3.5, reaction time 30 minutes, and a ratio of FeSO4 (30 wt%) to H2O2 (15 wt%) of 5:1. As shown in Table 3, with the simultaneous increase in the amount of FeSO4 and H2O2, the COD Cr When the dosage of H2O2 and FeSO4 is 5mL / L and 25mL / L respectively, the COD of eucalyptus chemical mechanical pulping wastewater after biological treatment is Cr When the dosage of H2O2 and FeSO4 was 1.5mL / L and 7.5mL / L respectively, the COD of eucalyptus chemical-mechanical pulping wastewater after ICPB treatment was 49mg / L. Cr It is 41 mg / L. It can be seen that compared with biological treatment, the amount of reagents used in the Fenton treatment experiment of wastewater after ICPB treatment is significantly reduced, which is beneficial to reducing the subsequent sludge volume and reducing the cost of wastewater treatment.

[0053] The present invention provides a concept and method for treating and detoxifying eucalyptus chemical-mechanical pulping wastewater. There are numerous methods and approaches for implementing this technical solution. The above is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Any components not specified in this embodiment may be implemented using existing technologies.

Claims

1. A detoxification method for treating eucalyptus chemical-mechanical pulping wastewater, characterized in that: The steps include: (1) The lignin charcoal / Bi2MoO6 catalyst is loaded onto a polyurethane sponge carrier, and then the polyurethane sponge carrier loaded with the above catalyst is put into the acclimated aerobic sludge, aerated, and the activated sludge is inoculated to obtain the inoculated polyurethane sponge carrier; (2) In a dark environment, the inoculated polyurethane sponge carrier is placed in a fluidized bed reactor and a biofilm is cultured using an SBR process to obtain a polyurethane sponge carrier loaded with the catalyst and the biofilm; (3) placing the polyurethane sponge carrier loaded with the above-mentioned catalyst and biofilm in an internal circulation reactor to construct a photocatalytic oxidation-biodegradation direct coupling system; (4) The anaerobic effluent from the eucalyptus chemical-mechanical pulp was added to the internal circulation reactor of the photocatalytic oxidation-biodegradation direct coupling system for treatment. During the treatment process, the experimental temperature and dissolved oxygen were controlled at 25±1°C and 4±0.5 mg / L, and the light source was an LED lamp; The lignin charcoal / Bi2MoO6 catalyst is loaded onto the polyurethane sponge carrier by the following method: 1) Placing the lignin charcoal / Bi2MoO6 catalyst in a container filled with anhydrous ethanol, stirring, and then ultrasonicating to obtain a suspension, placing a polyurethane sponge carrier into the suspension and stirring. During the above process, the container opening is sealed. The polyurethane sponge carrier is in the shape of a 7 mm ± 0.5 mm cube, and the mass ratio of the catalyst to the volume of anhydrous ethanol to the polyurethane sponge carrier is 1:20 to 150:2; 2) Unsealing the container in 1) and placing it on a magnetic stirrer at 60-70° C. to stir the anhydrous ethanol to completely evaporate the anhydrous ethanol. The polyurethane sponge carrier loaded with the catalyst is placed in an oven to dry. The polyurethane sponge carrier loaded with the catalyst obtained after drying is first washed with distilled water and then ultrasonicated. The polyurethane sponge carrier is then washed with distilled water again to remove loosely loaded catalyst. Finally, the polyurethane sponge carrier is placed in an oven to dry to a constant weight to obtain a polyurethane sponge carrier loaded with the catalyst. Before the treatment in step (4), the anaerobic effluent stabilization system of eucalyptus chemical mechanical pulp is used.

2. The method according to claim 1, characterized in that In step (1), the obtained polyurethane sponge carrier loaded with the above catalyst is put into aerobic sludge and aerated for 20-24 hours to complete the activated sludge inoculation. The inoculated polyurethane sponge carrier is then placed in a fluidized bed reactor to culture a biofilm using the SBR process.

3. The method according to claim 2, characterized in that In the process of cultivating biofilm, according to COD Cr : N : P = 200:5:1 ratio to prepare the experimental culture medium required for biofilm formation. During the biofilm culture process, the water temperature was maintained at 25±1℃, the dissolved oxygen content was controlled at 4±0.5 mg / L, and the culture medium was changed every 12 hours. When the effluent COD Cr Stable, biofilm culture completed.

4. A method for treating eucalyptus chemical-mechanical pulping wastewater, characterized in that: The detoxification treatment is carried out using the method described in any one of claims 1 to 3, and then the eucalyptus chemical-mechanical pulping wastewater obtained after the treatment is further treated by Fenton oxidation method.

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