A composite treating agent for waste material and a method for preparing the same

Abstract

The application relates to the technical field of environmental engineering, and discloses a composite treatment agent for waste treatment and a preparation method thereof. The composite treatment agent comprises a low-temperature adaptive enzyme composite system and modified nano photocatalytic material. The enzyme composite system is composed of lipase, cellulase and protease, and has high activity at 10-35 DEG C and pH 6.0-9.0. The modified nano photocatalytic material is formed by compounding nitrogen-doped titanium dioxide nanosheets and reduced graphene oxide. The preparation method comprises preparing the above enzyme system and photocatalytic material and mixing them. Through the above scheme, the application can realize synchronous efficient and complete treatment of organic matters and heavy metals, and improves the applicability, robustness and economic and environmental protection of waste treatment.

Description

Technical Field

[0001] This invention belongs to the field of environmental engineering technology and relates to a composite treatment agent for waste treatment and its preparation method. Background Technology

[0002] Traditional chemical treatment agents, with their non-specific strong oxidizing or reducing effects, while achieving rapid decomposition, often lead to incomplete decomposition of organic pollutants, generating potentially toxic intermediates such as halogenated hydrocarbons and polychlorinated biphenyl precursors, rather than complete mineralization. Even worse, to achieve ideal treatment results, excessive amounts of chemical agents are often introduced, increasing treatment costs and inevitably causing secondary chemical pollution problems such as acid and alkali residues, high-salinity wastewater, and catalyst metal ion leakage. Such secondary pollution often requires additional neutralization, precipitation, or fine treatment, making the entire treatment chain lengthy and complex. The environmental burden is not fundamentally reduced; instead, it may shift from one type of pollution to another, severely deviating from the original intention of harmless waste treatment.

[0003] Meanwhile, the bioactivity of single microbial treatment agents is strictly constrained by environmental factors, and their inherent characteristics limit their broad applicability. The growth and reproduction of microorganisms, as well as the activity of their enzymes, are extremely sensitive to environmental conditions such as temperature, pH, salinity, and heavy metal concentration. For example, in cold regions or winter, low temperatures inhibit the metabolic rate of microorganisms and the catalytic efficiency of enzymes, leading to a significant extension of the decomposition cycle or even complete loss of activity. Furthermore, in extreme acidic or alkaline environments or high heavy metal ion concentrations commonly found in industrial waste, the cell structure of microorganisms and the active sites of enzymes are easily damaged, causing a sudden decrease in their treatment capacity or complete inactivation. This stringent requirement for environmental conditions and low robustness makes it difficult for single microbial treatment agents to maintain continuous high efficiency in different regions, seasons, and when treating different types and sources of waste. This greatly limits their universality and practical application scope, resulting in overly narrow application scenarios that fail to meet the high standards of environmental adaptability required by modern society for waste treatment technologies. Summary of the Invention

[0004] To achieve the aforementioned objectives, this invention provides a composite treatment agent for waste treatment and its preparation method. It aims to overcome the prominent problems of existing waste treatment technologies when facing complex, heterogeneous, and environmentally variable waste pollution, such as low treatment efficiency, susceptibility to secondary pollution, poor environmental adaptability, and difficulty in achieving simultaneous and synergistic degradation of organic matter and heavy metals. The composite treatment agent provided by this invention, through the organic integration of a low-temperature adapted bio-enzyme composite system and modified nano-photocatalytic materials, achieves simultaneous, efficient, and thorough treatment of organic pollutants and inorganic heavy metals under relatively mild conditions, thereby improving the broad applicability, environmental robustness, and economic and environmental benefits of waste treatment.

[0005] The present invention provides a composite treatment agent for waste treatment, comprising the following active components: a low-temperature adapted bio-enzyme composite system and a modified nano-photocatalytic material. The mass ratio of the low-temperature adapted bio-enzyme composite system to the modified nano-photocatalytic material is 5:1 to 1:5.

[0006] In a preferred embodiment of the present invention, a low-temperature adapted bio-enzyme complex system is composed of lipase, cellulase, and protease in a specific ratio of active units. Specifically, the ratio of active units of lipase, cellulase, and protease in the complex system is 1000:500:800 to 5000:2000:3000. The lipase, cellulase, and protease are all obtained through efficient expression and purification from psychrophilic microorganisms using genetic engineering techniques, ensuring high activity and stability within a temperature range of 10°C to 35°C, with the optimal activity temperature range being 15°C to 30°C. The lipase has at least 10000 U / g of enzyme activity, the cellulase has at least 5000 U / g of enzyme activity, and the protease has at least 8000 U / g of enzyme activity. The low-temperature adapted bio-enzyme complex system can maintain high catalytic efficiency under weakly acidic to weakly alkaline conditions with a pH of 6.0 to 9.0. The enzyme complex system is prepared into a powder form using spray drying or freeze drying techniques, and maltodextrin is used as a protective agent to maintain its long-term storage stability.

[0007] In a preferred embodiment of the present invention, the modified nano-photocatalytic material is formed by combining nitrogen-doped titanium dioxide (N-TiO2) nanosheets with reduced graphene oxide (rGO). The N-TiO2 nanosheets serve as the core photocatalytic unit, and their preparation process includes the following steps: First, using tetrabutyl titanate as the titanium source and urea as the nitrogen source, a hydrothermal synthesis reaction is carried out in an ethanol solvent. The reaction temperature is controlled at 180°C to 220°C, and the reaction time is 12 to 24 hours. By adjusting the hydrothermal conditions, the crystal structure of the obtained N-TiO2 nanosheets can be precisely controlled, mainly existing in the anatase phase, which exhibits high photocatalytic activity. The average size of the N-TiO2 nanosheets is 10 nm to 50 nm, and the specific surface area is... to Nitrogen doping, by substituting oxygen sites or interstitial doping, effectively reduces the band gap of titanium dioxide from approximately 3.2 eV to 2.5 eV to 2.8 eV, thereby broadening its absorption range for visible light and improving its photoresponse efficiency. N-TiO2 nanosheets exhibit excellent visible light absorption capabilities, with their absorption edge red-shifted to the 500 nm to 550 nm range.

[0008] In a preferred embodiment of the present invention, graphene oxide (GO) is prepared by a modified Hummers method and further chemically reduced using reducing agents such as hydrazine hydrate or ascorbic acid. The reduction process is carried out in a water bath at 80°C to 95°C for 2 to 4 hours to ensure effective reduction of the graphene oxide, removing oxygen-containing functional groups and restoring its two-dimensional sheet structure and high conductivity. The specific surface area of ​​the obtained rGO is [missing information]. to The carbon-to-nitrogen ratio is between 150 and 250. rGO, as a carrier and electron transport medium for N-TiO2 nanosheets, with its unique two-dimensional structure and high conductivity, can effectively suppress the recombination of photogenerated electron-hole pairs, thereby improving the photocatalytic quantum efficiency.

[0009] In a preferred embodiment of the present invention, the composite process of N-TiO2 nanosheets and rGO first involves dispersing N-TiO2 nanosheets in deionized water to form a uniform suspension. Then, the rGO suspension is added dropwise to the N-TiO2 nanosheet suspension, and the mixture is ultrasonically treated for 1 to 3 hours to ensure thorough mixing of the two components and to achieve surface loading or eutectic growth. Ultrasonic treatment helps break up agglomerates and promotes the uniform dispersion of N-TiO2 nanosheets on the surface of rGO sheets or embedded within their structure. Subsequently, through steps such as vacuum filtration, washing, freeze-drying, or hot air drying, a powdered N-TiO2 / rGO composite nanomaterial is finally obtained. In the composite material, the mass ratio of N-TiO2 nanosheets to rGO is 5:1 to 10:1. This composite structure, through the formation of heterojunctions on the rGO surface by N-TiO2 nanosheets, increases the number of active sites and provides an efficient electron transport path, enabling photogenerated electrons to rapidly transfer from the conduction band of N-TiO2 to the conductive network of rGO, thereby effectively separating electron-hole pairs.

[0010] The method for preparing the composite treatment agent provided by the present invention includes the following steps:

[0011] Step 1: Preparation of a Low-Temperature Adapted Bioenzyme Complex System. First, recombinant microbial strains expressing lipase, cellulase, and protease are constructed using genetic engineering techniques. Then, the recombinant strains are fermented separately under the following conditions: temperature 18℃ to 25℃, pH 7.0 to 7.5, aeration rate of 1 vvm to 2 vvm, and culture time of 48 to 72 hours. After fermentation, the three enzymes are separated, purified, and concentrated using centrifugation, ultrafiltration, and other methods to achieve electrophoretic purity. Next, the activity units of each enzyme are measured, and they are precisely mixed according to a preset activity unit ratio (e.g., lipase, cellulase, and protease activity units ratio of 2500:1000:2000). Finally, the mixed enzyme solution is thoroughly mixed with maltodextrin (as a protective agent, with an enzyme-to-protectant mass ratio of 1:1 to 1:2), and then prepared into a stable enzyme powder by spray drying or freeze drying. The spray drying inlet temperature was set at 140℃ to 160℃, and the outlet temperature at 70℃ to 90℃; the freeze-drying pre-freezing temperature was set at -40℃ to -60℃, the main drying stage temperature was set at -20℃ to 0℃, and the secondary drying stage temperature was set at 20℃ to 30℃. This preparation process ensures maximum preservation of enzyme activity and imparts excellent storage stability.

[0012] Step Two: Preparation of Modified Photocatalytic Nanomaterials. First, N-TiO2 nanosheets were prepared according to the following sub-steps: Tetrabutyl titanate and urea were dissolved in anhydrous ethanol at a specific molar ratio to form a homogeneous precursor solution. This solution was transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and subjected to hydrothermal reaction at a constant temperature of 190℃ for 18 hours. After the reaction, the reactor was allowed to cool naturally to room temperature, and the reaction product was removed. Unreacted precursors and impurities were removed by centrifugation and washing. The washed precipitate was dried in a vacuum oven at 60℃ for 12 hours and then ground into fine N-TiO2 nanosheet powder. Next, reduced graphene oxide was prepared according to the following sub-steps: Graphene oxide was prepared using a modified Hummers method. Specifically, 3g of natural graphite powder was mixed with 150mL of concentrated sulfuric acid in an ice bath, and 10g of potassium permanganate was slowly added, controlling the temperature to not exceed 20℃. After stirring for 30 minutes, the mixture was transferred to a water bath at 35℃ and stirred for 2 hours. Subsequently, 200 mL of deionized water was slowly added, and the mixture was stirred for 30 minutes until the temperature reached 98°C. After stirring for another 15 minutes, 10 mL of hydrogen peroxide was added, and the solution color changed from brownish-yellow to bright yellow. Finally, a large amount of deionized water was added for dilution, and the solution was centrifuged and washed to obtain a graphene oxide dispersion. The graphene oxide dispersion was mixed with hydrazine hydrate (graphene oxide to hydrazine hydrate mass ratio of 1:0.5) and refluxed at 90°C for 3 hours to reduce graphene oxide. The reduced rGO suspension was centrifuged, washed, and then dried in a vacuum oven at 80°C for 24 hours, and ground into rGO powder. Finally, N-TiO2 nanosheets were composited with rGO according to the following sub-steps: the dried N-TiO2 nanosheet powder was dispersed in 200 mL of deionized water and sonicated for 30 minutes to ensure uniform dispersion. The obtained N-TiO2 suspension was mixed with a pre-prepared rGO suspension (containing 0.8 g g GO), and the mixture was sonicated for 2 hours to promote uniform loading of N-TiO2 nanosheets on the rGO surface. The mixed suspension was stirred and evaporated at 80 °C until a slurry was formed. The slurry was dried in a vacuum oven at 60 °C for 12 hours, and then ground into a fine N-TiO2 / rGO composite nanomaterial powder.

[0013] Step 3: The low-temperature adapted bio-enzyme composite powder prepared in Step 1 and the modified nano-photocatalytic material powder prepared in Step 2 are precisely weighed according to a preset mass ratio. They are then uniformly mixed using a V-type mixer or a planetary ball mill for 30 to 60 minutes at a speed of 30 to 60 rpm to ensure highly uniform dispersion of the two components on a macroscopic scale, avoiding stratification or agglomeration. The mixing process is carried out in a clean environment with an ambient temperature of 20°C to 25°C and a relative humidity of 40% to 60%. The resulting composite treatment agent powder is then dispensed in a dry environment and stored in sealed containers to prevent moisture absorption and activity loss.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] The composite treatment agent provided by this invention achieves simultaneous, efficient, and thorough treatment of organic pollutants and inorganic heavy metals under relatively mild conditions by organically integrating a low-temperature adaptable bio-enzyme composite system with modified nano-photocatalytic materials, thereby improving the broad applicability, environmental robustness, and economic and environmental benefits of waste treatment. Detailed Implementation

[0016] The technical solutions of the present invention will be described in detail below with reference to embodiments and comparative examples, in order to ensure that those skilled in the art can fully understand and implement the present invention based on the content of this disclosure.

[0017] Example 1: Preparation of a low-temperature adapted bio-enzyme complex system: Lipase was produced by fermentation using recombinant strains of *Pseudomonas*, cellulase by fermentation using recombinant strains of *Bacillus*, and protease by fermentation using recombinant strains of *Vibrio cellulose*. Fermentation temperature was 20℃, pH 7.2, aeration rate was 1.5 vvm, and culture time was 60 hours. After centrifugation and ultrafiltration, enzyme activities were measured: lipase 12000 U / g, cellulase 6000 U / g, and protease 9000 U / g, mixed at an activity unit ratio of 1000:500:800. The enzymes were mixed with maltodextrin at a mass ratio of 1:1, spray-dried at an inlet temperature of 140℃ and an outlet temperature of 70℃ to obtain enzyme powder.

[0018] Preparation of modified photocatalytic nanomaterials: Tetrabutyl titanate and urea were dissolved in anhydrous ethanol at a molar ratio of 2:1, and the mixture was hydrothermally reacted at 180℃ for 24 hours. After centrifugation and washing, the mixture was vacuum dried at 60℃ for 12 hours to obtain N-TiO2 nanosheets with an average size of 10 nm and a specific surface area of ​​[missing information]. A modified Hummers method was used to prepare graphene oxide. Graphene oxide was mixed with hydrazine hydrate at a mass ratio of 1:0.5, reduced in a water bath at 80°C for 4 hours, centrifuged, washed, and vacuum dried at 80°C for 24 hours to obtain reduced graphene oxide with a specific surface area of ​​[missing information]. The carbon-to-nitrogen ratio was 250. N-TiO2 nanosheets and reduced graphene oxide were mixed at a mass ratio of 5:1, ultrasonicated for 3 hours, stirred and evaporated at 80°C to form a slurry, and vacuum dried at 60°C for 12 hours to obtain photocatalytic material powder.

[0019] Mixing of composite treatment agents: The enzyme powder and photocatalytic material powder are mixed at a mass ratio of 5:1 in a V-type mixer at 30 rpm for 60 minutes at 20°C and 40% relative humidity.

[0020] Example 2: Preparation of a low-temperature adapted bio-enzyme complex system: Lipase, cellulase, and protease were produced by fermentation using recombinant strains of *Pseudomonas*, *Bacillus*, and *Vibrio*, respectively. Fermentation temperature was 18℃, pH 7.0, aeration rate was 1 vvm, and culture time was 72 hours. After separation and purification, the enzyme activities were 15000 U / g, 7000 U / g, and 10000 U / g, respectively, and were mixed at an activity unit ratio of 2500:1000:2000. The enzyme was mixed with maltodextrin at a mass ratio of 1:1.5, freeze-dried, pre-frozen at -40℃, primary dried at -20℃, and secondary dried at 20℃ to obtain enzyme powder.

[0021] Preparation of modified photocatalytic nanomaterials: N-TiO2 nanosheets with an average size of 30 nm and a specific surface area of ​​1:1 were prepared by hydrothermal reaction of tetrabutyl titanate and urea at 200℃ for 18 hours. Reduced graphene oxide was prepared by reducing graphene oxide with hydrazine hydrate at a mass ratio of 1:0.5 in a water bath at 90°C for 3 hours. The specific surface area was [not specified]. The carbon-to-nitrogen ratio was 200. N-TiO2 nanosheets and reduced graphene oxide were mixed at a mass ratio of 8:1, ultrasonicated for 2 hours, and then subjected to the same subsequent treatment as in Example 1 to obtain photocatalytic material powder.

[0022] Composite treatment agent mixing: Enzyme powder and photocatalytic material powder are mixed at a mass ratio of 2:1 in a planetary ball mill at 45 rpm for 45 minutes at 22°C and 50% relative humidity.

[0023] Example 3: Preparation of a low-temperature adapted bio-enzyme complex system: The fermentation strain was the same as in Example 1, the fermentation temperature was 25℃, pH 7.5, the aeration rate was 2 vvm, and the culture time was 48 hours. After isolation and purification, the enzyme activities were 20000 U / g, 8000 U / g, and 12000 U / g, respectively, and were mixed at an activity unit ratio of 3500:1500:2500. The enzyme and maltodextrin were mixed at a mass ratio of 1:2, spray-dried at an inlet temperature of 160℃ and an outlet temperature of 90℃ to obtain enzyme powder.

[0024] Preparation of modified photocatalytic nanomaterials: N-TiO2 nanosheets with an average size of 50 nm and a specific surface area of ​​1:0.5 were prepared by hydrothermal reaction of tetrabutyl titanate and urea at 220℃ for 12 hours. Graphene oxide was reduced with ascorbic acid and then subjected to a water bath at 85°C for 3 hours to obtain reduced graphene oxide with a specific surface area of ​​[missing information]. The carbon-to-nitrogen ratio was 150. N-TiO2 nanosheets and reduced graphene oxide were mixed at a mass ratio of 10:1, ultrasonicated for 1 hour, and then subjected to the same subsequent treatment as in Example 1 to obtain photocatalytic material powder.

[0025] Mixing of composite treatment agents: The enzyme powder and photocatalytic material powder are mixed at a mass ratio of 1:1 in a V-type mixer at 60 rpm for 30 minutes at 25°C and 60% relative humidity.

[0026] Example 4: Preparation of a low-temperature adapted bio-enzyme complex system: Fermentation temperature 22℃, pH 7.3, aeration rate 1.8 vvm, culture time 55 hours. Enzyme activities were 18000 U / g, 7500 U / g, and 11000 U / g, respectively, mixed at an activity unit ratio of 4000:1800:2800. The enzyme and maltodextrin were mixed at a mass ratio of 1:1.2, freeze-dried, pre-frozen at -50℃, primary dried at -10℃, and secondary dried at 25℃ to obtain enzyme powder.

[0027] Preparation of modified photocatalytic nanomaterials: N-TiO2 nanosheets with an average size of 20 nm and a specific surface area of ​​1.5:1 were prepared by hydrothermal reaction of tetrabutyl titanate and urea at 190℃ for 20 hours. The preparation of reduced graphene oxide is the same as in Example 2, with the same specific surface area. The carbon-to-nitrogen ratio was 180. N-TiO2 nanosheets and reduced graphene oxide were mixed at a mass ratio of 6:1, ultrasonicated for 2.5 hours, and then subjected to the same subsequent treatment as in Example 1 to obtain photocatalytic material powder.

[0028] Composite treatment agent mixing: Enzyme powder and photocatalytic material powder are mixed at a mass ratio of 1:2 in a planetary ball mill at 50 rpm for 40 minutes at 23°C and 45% relative humidity.

[0029] Example 5: Preparation of a low-temperature adapted bio-enzyme complex system: Fermentation temperature 23℃, pH 7.4, aeration rate 1.2 vvm, culture time 50 hours. Enzyme activities were 16000 U / g, 6500 U / g, and 10500 U / g, respectively, mixed at an activity unit ratio of 5000:2000:3000. The enzyme and maltodextrin were mixed at a mass ratio of 1:1.8, spray-dried at an inlet temperature of 150℃ and an outlet temperature of 80℃ to obtain enzyme powder.

[0030] Preparation of modified photocatalytic nanomaterials: N-TiO2 nanosheets with an average size of 40 nm and a specific surface area of ​​1.2:1 were prepared by hydrothermal reaction of tetrabutyl titanate and urea at 210℃ for 16 hours. The preparation of reduced graphene oxide is the same as in Example 3, with the same specific surface area. The carbon-to-nitrogen ratio was 170. N-TiO2 nanosheets and reduced graphene oxide were mixed at a mass ratio of 9:1, ultrasonicated for 1.5 hours, and then subjected to the same subsequent treatment as in Example 1 to obtain photocatalytic material powder.

[0031] Mixing of composite treatment agents: The enzyme powder and photocatalytic material powder are mixed at a mass ratio of 1:5 in a V-type mixer at 40 rpm for 50 minutes at 24°C and 55% relative humidity.

[0032] Comparative Example 1 (single chemical treatment agent) uses traditional potassium permanganate chemical treatment agent, which is directly used for waste treatment and contains no biological enzymes or photocatalytic materials.

[0033] Comparative Example 2 (single microbial treatment agent): using conventional Bacillus microbial treatment agent, without biological enzyme complex system and modified nano-photocatalytic materials, relying solely on the metabolic action of microorganisms to treat waste.

[0034] Comparison table of data from Examples 1-5 and Comparative Examples 1-2:

[0035]

[0036] The organic matter degradation rates in Examples 1-5 were all between 92% and 96%, and the heavy metal removal rates were between 88% and 93%, which are higher than those in Comparative Example 1 (organic matter degradation rate 75%, heavy metal removal rate 65%) and Comparative Example 2 (organic matter degradation rate 68%, heavy metal removal rate 55%). This indicates that the composite treatment agent of this application, through the synergistic effect of a low-temperature adapted bio-enzyme composite system and modified nano-photocatalytic materials, can more efficiently treat organic matter and heavy metals in waste.

[0037] Examples 1-5 showed no secondary pollution after treatment, while Comparative Example 1, which used traditional chemical treatment agents, produced secondary pollution such as acid and alkali residues, which violated the original intention of harmless waste treatment. This demonstrates the environmental advantages of the composite treatment agent in this application.

[0038] Under low temperature (10℃) conditions, the treatment efficiency of Examples 1-5 was 85%-89%, which was much higher than that of Comparative Example 2 (35%), indicating that the low temperature adapted bio-enzyme composite system can maintain high activity in low temperature environment. Under pH=6.0 and pH=9.0 conditions, the treatment efficiency of Examples 1-5 was stable at 89%-94%, while the treatment efficiencies of Comparative Example 1 and Comparative Example 2 fluctuated greatly and were generally lower, indicating that the composite treatment agent of this application has good robustness under different pH environments and stronger environmental adaptability.

[0039] Example 5 showed the highest organic matter degradation rate (96%) and heavy metal removal rate (93%), and also the best treatment efficiency under low temperature and different pH conditions. The combination of enzyme activity unit ratio (5000:2000:3000), N-TiO2 nanosheet to reduced graphene oxide mass ratio (9:1), and enzyme to photocatalytic material mass ratio (1:5) in its formulation was more reasonable, and the synergistic effect was more fully exerted.

[0040] Although the chemical treatment agent in Comparative Example 1 has a certain treatment effect at room temperature, it has the problem of secondary pollution. The single microbial treatment agent in Comparative Example 2 is greatly affected by the environment, its activity drops sharply at low temperature, and its effect on removing heavy metals is poor. This further highlights the advantages of the composite treatment agent of this application in terms of treatment efficiency, environmental protection and environmental adaptability.

[0041] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite treatment agent for waste treatment, characterized in that, Comprise: Low-temperature adaptive biological enzyme complex system; Modified nano-photocatalytic material; The mass ratio of the low-temperature adaptive biological enzyme complex system to the modified nano-photocatalytic material is 5:1 to 1:5; The low-temperature adaptive biological enzyme complex system is composed of lipase, cellulase and protease; the activity unit ratio of the lipase, the cellulase and the protease is 1000:500:800 to 5000:2000:3000; The lipase, the cellulase and the protease are obtained by high-efficiency expression and purification from psychrophilic microorganisms through genetic engineering technology, and the psychrophilic microorganisms include but are not limited to Pseudomonas, Bacillus or Vibrio strains; The lipase has an enzyme activity of at least 10,000 U / g, the cellulase has an enzyme activity of at least 5,000 U / g, and the protease has an enzyme activity of at least 8,000 U / g; The modified nano-photocatalytic material is formed by compounding N-TiO2 nanosheets and rGO; The N-TiO2 nanosheet exists mainly in an anatase phase, has an average size of 10 nm to 50 nm, and has a specific surface area of 100 m2 / g to 300 m2 / g The N-TiO2 nanosheets are prepared by using tetrabutyl titanate as a titanium source, urea as a nitrogen source, and hydrothermal synthesis reaction in an ethanol solvent at 180°C to 220°C for 12 hours to 24 hours; The rGO is prepared by improving the Hummers method to prepare GO, and further obtained by chemical reduction with hydrazine hydrate or ascorbic acid reducing agent; The reduction process is carried out in a water bath at 80°C to 95°C for 2 hours to 4 hours; The specific surface area of the rGO is The carbon to nitrogen ratio is between 150 and 250; The compounding process of the N-TiO2 nanosheets and the rGO includes dispersing the N-TiO2 nanosheets in deionized water to form a uniform suspension, then adding the rGO suspension drop by drop into the N-TiO2 nanosheet suspension, and treating by ultrasonic wave for 1 hour to 3 hours to fully mix the two components and realize surface loading or co-crystal growth; The mass ratio of the N-TiO2 nanosheets to the rGO is 5:1 to 10:1; The composite structure forms a heterojunction on the surface of the rGO through the N-TiO2 nanosheets.

2. The composite treatment agent for waste treatment according to claim 1, characterized by The low-temperature adaptive biological enzyme complex system maintains high catalytic efficiency at a temperature range of 10°C to 35°C and under weakly acidic to weakly alkaline conditions with a pH value of 6.0 to 9.0; The enzyme complex system is prepared into powder by spray drying or freeze drying technology, and malt dextrin is used as a protective agent to maintain its long-term storage stability.

3. A method for producing a composite treatment agent for waste treatment, for producing the composite treatment agent for waste treatment according to any one of claims 1 to 2, characterized by, Comprise the following steps: Step one: preparing a low-temperature adaptive biological enzyme complex system; Step two: preparing a modified nano-photocatalytic material; Step three: mixing the low-temperature adaptive biological enzyme complex system powder with the modified nano-photocatalytic material powder.

4. The preparation method according to claim 3, characterized in that: The step one comprises the following sub-steps: The recombinant microbial strains expressing lipase, cellulase and protease are respectively fermented, and the culture conditions include but are not limited to temperature 18-25℃, pH 7.0-7.5, aeration rate 1-2vvm, and culture time 48-72 hours; after fermentation, the lipase, cellulase and protease are separated, purified and concentrated by centrifugation and ultrafiltration; The activity units of each enzyme are determined, and the enzymes are accurately mixed according to the preset activity unit ratio, wherein the activity unit ratio of lipase, cellulase and protease is 2500:1000:2000; The mixed enzyme solution is uniformly mixed with malt dextrin, and the mass ratio of lipase, cellulase and protease to malt dextrin is 1:1-1:2, and then a stable enzyme powder is prepared by spray drying or freeze drying, wherein the inlet temperature of spray drying is set to 140-160℃, and the outlet temperature is set to 70-90℃, and the pre-freezing temperature of freeze drying is set to -40--60℃, the main drying stage temperature is set to -20-0℃, and the secondary drying stage temperature is set to 20-30℃. The step two comprises the following sub-steps: Preparation of the N-TiO2 nanosheet: tetrabutyl titanate and urea are dissolved in anhydrous ethanol to form a uniform precursor solution, which is transferred to a stainless steel high-pressure reactor with a polytetrafluoroethylene liner, and hydrothermal reaction is carried out at 190℃ for 18 hours, and the reaction product is centrifuged, washed and dried in a vacuum oven at 60℃ for 12 hours, and then ground into fine N-TiO2 nanosheet powder; Preparation of the rGO: the GO is prepared by a modified Hummers method, and the GO dispersion liquid is mixed with a reducing agent hydrazine hydrate, wherein the mass ratio of the GO to the hydrazine hydrate is 1:0.5, and the GO is reduced by refluxing at 90℃ for 3 hours, and the reduced rGO suspension is centrifuged, washed and dried in a vacuum oven at 80℃ for 24 hours, and then ground into rGO powder; The N-TiO2 nanosheet is compounded with the rGO: the N-TiO2 nanosheet powder is dispersed in deionized water and ultrasonically treated for 30 minutes, and then the N-TiO2 suspension is mixed with the previously prepared rGO suspension and ultrasonically treated for 2 hours, and then the mixed suspension is stirred and evaporated at 80℃ until a slurry is formed, and the slurry is dried in a vacuum oven at 60℃ for 12 hours, and then ground into fine N-TiO2 / rGO composite nanomaterial powder; The step three comprises the following sub-steps: The low-temperature adapted enzyme composite system powder prepared in step one and the modified nanophotocatalytic material powder prepared in step two are uniformly mixed by a V-shaped mixer or a planetary ball mill at a preset mass ratio for 30-60 minutes at a speed of 30-60 rpm, and the mixing process is carried out in a clean environment at an ambient temperature of 20-25℃ and a relative humidity of 40-60%.

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