A method for treating pulp and pine wastewater by using MOG-Fe / Al flocculant with coral-like shape

Abstract

The application discloses a method for treating pulp and barking wastewater by using MOG-Fe / Al flocculants in a shape similar to coral stone, and comprises the following steps: preparing MOG-Fe / Al flocculants by using aluminum nitrate, iron nitrate and trimesic acid; diluting pulp and barking wastewater, adjusting pH and temperature, and adding flocculants and standing and settling. The MOG-Fe / Al flocculants are colloidal particles in a dense network shape, attached to more pores and similar to coral stone, have interwoven fibers or particles, are rich in mesoporous structures, can provide many active centers, are favorable for diffusion of molecules in the pores, have a large specific surface area of the material, further improve the adsorption performance in water treatment, and improve the removal rate. The results show that when the MOG-Fe / Al dosage is 1.0 g, the wastewater concentration is diluted to 100 times, the pH is 9, the flocculation temperature is 30 DEG C, the flocculation time is 12 h, and the wastewater turbidity removal rate can reach 98.3%.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology. Specifically, it is a method for treating pulp and slag wastewater using a MOG-Fe / Al flocculant with a coral-like shape. Background Technology

[0002] Pulp and paper wastewater mainly originates from the pulping and papermaking industries. It is generated during wood processing and pulp extraction, and its composition is complex, primarily containing lignin, cellulose, various organic compounds and inorganic substances, and may also contain bleaching agents and other chemicals. Xinjiang Uygur Autonomous Region, as a major cotton-producing province in China, has a rapidly developing cotton textile industry, generating a large amount of pulp and paper wastewater annually. Efficiently treating this wastewater, which contains large amounts of cotton linters, cellulose, waxes, pectin, fats, sand, and other impurities, to meet the region's Class I discharge standards is a crucial prerequisite for enterprises to achieve both environmental protection and green production in Xinjiang Uygur Autonomous Region. It is also an effective way to realize the recycling of water resources in Xinjiang Uygur Autonomous Region.

[0003] Currently, the treatment of pulp and cypress wastewater in Xinjiang Uygur Autonomous Region mainly employs physical, chemical, biological, membrane separation, and advanced oxidation technologies. Physical methods remove suspended solids and large particulate pollutants through sedimentation, filtration, and flotation; chemical methods remove dissolved pollutants and harmful substances through coagulation-flotation and redox reactions using chemical agents. Biological methods utilize aerobic or anaerobic microorganisms to degrade organic matter and reduce organic load. Membrane separation technologies such as ultrafiltration, nanofiltration, and reverse osmosis achieve deep treatment; advanced oxidation technologies utilize strong oxidants or photocatalysis to degrade recalcitrant organic matter. To improve the utilization rate of pulp and cypress wastewater, realize water resource reuse, and solve problems such as high energy consumption, high treatment costs, low recovery efficiency, and complex operation in the treatment process, flocculation has always been the most effective wastewater treatment method, and the development of highly efficient new flocculants has become a primary goal for researchers.

[0004] However, existing flocculants used for wastewater treatment include polyaluminum chloride (PAC), polyacrylamide (PAM), and aluminum sulfate. Due to the complex composition, high concentration of suspended solids, and large amount of organic matter in pulp and slurry wastewater, the single chemical structure and fixed flocculation mechanism of existing flocculants still result in problems such as low flocculation efficiency, poor flocculation and sedimentation, and secondary pollution when used to treat pulp and slurry wastewater. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the technical problem this invention aims to solve is to improve the pore structure of existing flocculants and increase their efficiency in treating pulp and sludge wastewater. Therefore, this invention provides a method for treating pulp and sludge wastewater using a coral-like MOG-Fe / Al flocculant.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] This invention provides a method for treating pulp and slag wastewater using a MOG-Fe / Al flocculant with a coral-like shape, comprising the following steps:

[0008] (1) Preparation of MOG-Fe / Al flocculant:

[0009] Aluminum nitrate, ferric nitrate, and trimesic acid were mixed, and ethanol was added. The mixture was stirred and dissolved at room temperature. The mixture was then sealed and subjected to a hydrothermal synthesis reaction. After the reaction, the mixture was cooled to room temperature and freeze-dried to obtain the final product.

[0010] (2) Dilute the raw wastewater of slurry and let it stand. Then, carry out subsequent treatment of the diluted wastewater. Adjust the pH and temperature of the diluted wastewater, add MOG-Fe / Al flocculant, and let it stand to settle. The treatment is then completed.

[0011] In this invention, an iron-aluminum mixture is used: iron and aluminum are commonly used flocculants with good flocculation effects. Iron ions (Fe...) 2+ or Fe 3+ Aluminum ions (Al) have a strong coagulating ability in water, effectively removing suspended solids and colloids. 3+ These two ions combine to form larger flocs, increasing settling properties. The combination of these two ions allows the flocculant to maintain excellent performance across a wide pH range. Tripterygic acid, as an organic polymer, helps improve the stability and structural strength of the flocculant and can be tailored to specific water quality conditions. The introduction of this material helps increase the molecular weight of the flocculant, thereby improving its role in water treatment.

[0012] The structure of the MOG-Fe / Al flocculant prepared by this invention differs from that of traditional flocculants based on a single metal or other polymeric materials. The composite structure of MOG-Fe / Al in this invention enables the effective formation of larger flocs and higher settling velocities during the reaction process, making it particularly important for the treatment of pulp and sludge wastewater characterized by high turbidity and high organic matter content.

[0013] Furthermore, since pulp and slag wastewater typically contains high concentrations of organic matter (such as lignin and cellulose) and complex colloidal particles, the flocculant must not only react effectively with the organic matter but also stably form large settling flocs. Based on the structural characteristics of the MOG-Fe / Al of this invention, it exhibits superior treatment performance in removing these organic substances. While replacing iron and aluminum with other metals, such as zinc and magnesium, also possesses some chemical precipitation capabilities, their hydrolytic and floc-forming abilities are inferior to iron and aluminum. Using other organic polymer materials, such as polyaluminum chloride, polyacrylamide, polyvinyl alcohol, and polyacryl alcohol, results in flocculants with relatively simple structures, all of which lead to insufficient treatment performance.

[0014] Preferably, the pulp wastewater of the present invention comes from the pulp and paper industry and is black liquor produced during wood processing and pulp extraction. It is rich in humic acid, fulvic acid, lignin, cellulose and chemical additives.

[0015] Preferably, the UV of the pulp wastewater 600 ≥2, turbidity ≥35 NTU, pH ≥11;

[0016] The composition of cypress wastewater is complex, mainly containing lignin, cellulose, various organic compounds and inorganic substances, as well as bleaching agents and other chemicals. It usually has high biochemical oxygen demand (BOD), chemical oxygen demand (COD) and turbidity, and the water is dark in color.

[0017] Preferably, in step (1), the molar ratio of aluminum nitrate, ferric nitrate, and trimesic acid is 15:10:(16-17);

[0018] Preferably, in step (1), the mass ratio of pyromellitic acid to ethanol is (4-5) g: 70 mL; the stirring time is 20-30 min.

[0019] Preferably, in step (1), the temperature of the hydrothermal synthesis reaction is 120-150℃ and the time is 1-3h; the temperature of the freeze drying is -60~-65℃ and the time is 12-24h.

[0020] Preferably, in step (2), the dilution ratio of the raw pulp wastewater is 50-550 times; the standing time after dilution is 10-20 minutes.

[0021] More preferably, in step (2), the dilution factor of the raw pulp wastewater solution is 100 times;

[0022] If the dilution is less than 100 times, the concentration of pollutants in the wastewater is too high, and the flocculant is insufficient, reaching its limit; while if the dilution exceeds 100 times, the concentration of pollutants is too low, and the flocculant is excessive, some of which fails to play its role and instead generates new pollutants, resulting in a decrease in the removal rate.

[0023] Preferably, in step (2), the pH of the diluted wastewater is adjusted to 6-12 and the temperature is 20-70℃;

[0024] More preferably, in step (2), the pH of the diluted wastewater is adjusted to 9 and the temperature is 30°C;

[0025] The pH value has a significant impact on the activity of flocculants. The hydroxyl groups on the surface of the flocculants play a key role in the adsorption process. The stronger the alkalinity of the solution, the lower the degree of protonation. The optimal pH adjustment for this method is 9. At the same time, raising the temperature at low temperatures can enhance the activity of flocculants and improve the flocculation effect. However, excessively high temperatures will reduce the activity of some flocculants, resulting in a decrease in the removal rate. The optimal temperature for this method is 30℃.

[0026] Preferably, in step (2), the mass ratio of the added MOG-Fe / Al flocculant to the volume of the diluted wastewater is 5-15 g: 1 L;

[0027] More preferably, in step (2), the mass ratio of the added MOG-Fe / Al flocculant to the volume ratio of the diluted wastewater is 10g:1L;

[0028] If the amount of flocculant used is too large, the excessive amount of flocculant will lead to enhanced interaction between flocculants, forming large flocs. These large flocs may be difficult to settle or be filtered, thus reducing the flocculation effect.

[0029] Preferably, in step (2), the settling time after adding MOG-Fe / Al flocculant is 1-12 hours;

[0030] More preferably, in step (2), the settling time after adding MOG-Fe / Al flocculant is 12h.

[0031] The technical solution of the present invention achieves the following beneficial technical effects:

[0032] Due to the high turbidity and concentration of pulp and cypress wastewater, conventional flocculants often suffer from poor flocculation, slow settling speed, or limited removal of specific pollutants, as these flocculants are mostly based on cationic or anionic polymer structures. This invention uses aluminum and iron as metal ions, trimellitic acid as a ligand, and ethanol as a reaction solvent. A hydrothermal reaction is carried out at 120-150℃ to synthesize a functional coral-like metal-organic gel composite material, MOG-Fe / Al, for treating pulp and cypress wastewater. The treatment effect and process conditions were evaluated for pulp and cypress wastewater. The synthesized MOG-Fe / Al material has a porous, irregular morphology with a specific surface area of ​​360.5 m². 2 / g, belonging to the micro-mesoporous material category, this MOG-Fe / Al gel material demonstrates significant practical value and broad development prospects in the field of pulp and slag wastewater treatment. Specific analysis is as follows:

[0033] The MOG-Fe / Al flocculant prepared in this invention is a dense network of colloidal particles with numerous pores, resembling the shape of coral stone, and possessing interwoven fibers or particles. The average pore size of MOG-Fe / Al is concentrated at 1.7 nm, 2.4 nm, and 5.0 nm, classifying it as a micro-mesoporous material with abundant mesoporous structures. These structures not only provide numerous active centers for the material's application but also facilitate the diffusion of target molecules within the pores. The presence of pores in the MOG-Fe / Al flocculant helps to increase the material's specific surface area, thereby improving its adsorption performance in water treatment. Furthermore, the density and anisotropy of the material's surface network are related to its physical and chemical properties.

[0034] This invention utilizes MOG-Fe / Al flocculant to treat pulp and slurry wastewater, and optimizes the process conditions. Results show that at a MOG-Fe / Al dosage of 1.0 g, wastewater concentration diluted 100 times, pH 9, flocculation temperature of 30℃, and flocculation time of 12 h, the turbidity removal rate reaches 98.3%, demonstrating the best flocculation treatment effect for pulp and slurry wastewater. MOG-Fe / Al exhibits excellent flocculation performance in cotton textile wastewater treatment and has significant application potential. This invention provides a feasible new solution for wastewater treatment in the cotton textile industry of Xinjiang Uygur Autonomous Region, offers a new approach to cotton pulp wastewater treatment, and is of great significance to the protection of water resources and the sustainable development of the ecological environment in Xinjiang Uygur Autonomous Region, especially in southern Xinjiang. Attached Figure Description

[0035] Figure 1 The absorbance of wastewater at different wavelengths in Example 3 of this invention;

[0036] Figure 2Turbidity removal rate at different MOG-Fe / Al flocculant dosages in Example 3 of this invention;

[0037] Figure 3 The turbidity removal rate of MOG-Fe / Al flocculant for wastewater of different concentrations in Example 4 of this invention;

[0038] Figure 4 The turbidity removal rate of wastewater at different temperatures by MOG-Fe / Al flocculant in Example 5 of this invention;

[0039] Figure 5 The turbidity removal rate of MOG-Fe / Al flocculant in wastewater with different pH values ​​in Example 6 of this invention;

[0040] Figure 6 Turbidity removal rate of MOG-Fe / Al flocculant under different settling times in Example 7 of this invention;

[0041] Figure 7 SEM images of MOG-Fe / Al, MOG-Fe, and MOG-Al in this invention;

[0042] Among them, a: MOG-Fe / Al (500nm); b: MOG-Fe (500nm); c: MOG-Al (500nm); d: MOG-Fe / Al (1μm); e: MOG-Fe (1μm); f: MOG-Al (1μm);

[0043] Figure 8 FT-IR images of MOG-Fe / Al, MOG-Fe, and MOG-Al in this invention;

[0044] Figure 9 XRD patterns of MOG-Fe / Al, MOG-Fe, and MOG-Al in this invention;

[0045] Figure 10 TG diagrams of MOG-Fe / Al, MOG-Fe, and MOG-Al in this invention;

[0046] Figure 11 X-ray photoelectron spectroscopy analysis of MOG-Fe / Al in Example 1 of this invention;

[0047] Figure 12 N2 adsorption-desorption test diagram of MOG-Fe / Al in Example 1 of this invention;

[0048] Figure 13 Pore ​​size distribution diagram of MOG-Fe / Al in Example 1 of this invention. Detailed Implementation

[0049] To make the objectives, technical solutions, and technical effects of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0050] The following detailed description of a method for treating pulp wastewater using a coral-like MOG-Fe / Al flocculant is illustrated by specific embodiments.

[0051] The pulp wastewater (black liquor) used in the following examples was obtained from Alar City Zhongtai Textile Technology Co., Ltd.; sample specifications: black liquor concentration 50% (i.e., the mass percentage of solids in the black liquor). Sample characteristics: black, paste-like, with a faint grassy smell. Water solubility: easily soluble; viscosity: 41040 mPa·s; humic acid mass concentration in black liquor: 5.12%, fulvic acid mass concentration: 20.04%, other organic matter mass concentration: 59.36%; moisture mass concentration: 10.11%; pH value: 12.00; black liquor nutrients: N: 0.280%; P: 0.598%; K: 1.520%; total nutrient mass percentage: 2.398%.

[0052] Example 1: Preparation of MOG-Fe / Al flocculant

[0053] 5.625 g of aluminum nitrate nonahydrate (15 mmol), 4.04 g of ferric nitrate nonahydrate (10 mmol), and 4.625 g of trimesic acid (16.667 mmol) were weighed and placed in a 500 mL beaker. Then, 70 mL of ethanol was added, and the mixture was stirred at room temperature for 20 min to dissolve. The solution was then placed in a hydrothermal synthesis vessel and sealed. The vessel was placed in an oven at 120 °C for 2 h and reacted. After cooling to room temperature, the sample was removed and dried in a freeze dryer at -64.3 °C for 12 h to obtain MOG-Fe / Al material.

[0054] Comparative Example 1: Preparation of MOG-Fe flocculant

[0055] 4.04 g of ferric nitrate nonahydrate (10 mmol) and 4.625 g of trimesic acid (16.667 mmol) were weighed and placed in a 500 mL beaker. Then, 70 mL of ethanol was added, and the mixture was stirred at room temperature for 20 min to dissolve. The solution was then placed in a hydrothermal synthesis vessel and sealed. The vessel was placed in an oven at 120 °C for 2 h and reacted. After cooling to room temperature, the sample was removed and dried in a freeze dryer at -64.3 °C for 12 h to obtain MOG-Fe material.

[0056] Preparation of Comparative Example 2 MOG-Al Flocculant

[0057] 5.625 g of aluminum nitrate nonahydrate (15 mmol) and 4.625 g of trimesic acid (16.667 mmol) were weighed and placed in a 500 mL beaker. Then, 70 mL of ethanol was added, and the mixture was stirred at room temperature for 20 min to dissolve. The solution was then placed in a hydrothermal synthesis vessel and sealed. The vessel was placed in an oven at 120 °C for 2 h and reacted. After cooling to room temperature, the sample was removed and dried in a freeze dryer at -64.3 °C for 12 h to obtain MOG-Al material.

[0058] Example 2: Method for treating pulp wastewater using MOG-Fe / Al flocculant with a coral-like shape.

[0059] Dilute the original wastewater of slurry with distilled water 100 times, let it stand for 10 minutes, adjust the pH of the diluted wastewater to 9, add the MOG-Fe / Al flocculant obtained in Example 1 (the mass ratio of MOG-Fe / Al flocculant to the volume of diluted wastewater is 10g:1L) at 30℃, and let it stand for sedimentation and flocculation treatment for 12 hours to complete the treatment.

[0060] The absorbance (measured after filtration) and turbidity (measured directly without filtration) of the slurry wastewater before and after treatment were measured using a UV-Vis spectrophotometer and a turbidimeter. Changes in absorbance reflect changes in the concentration of certain solutes (such as organic matter) in the wastewater; turbidity measurement evaluates the light-scattering ability of suspended solids in the water, thereby assessing the treatment effect of the flocculant on the wastewater.

[0061] The determination of the maximum absorption wavelength involved measuring the absorbance of the diluted wastewater at wavelengths of 550 nm, 560 nm, 570 nm, 580 nm, 590 nm, 600 nm, 610 nm, 620 nm, 630 nm, 640 nm, and 650 nm. The absorbance of the wastewater at different wavelengths was then calculated as follows: Figure 1 As shown in the figure, the maximum absorption wavelength was finally determined to be 600 nm, so the experiment was conducted at this wavelength.

[0062] The experimental results show that the original pulp wastewater solution before treatment: UV 600 2.1 Turbidity: 35 ± 1.5 NTU; pH: 12.00 ± 0.01;

[0063] Post-treatment pulp wastewater: UV 600 0.079 NTU, Turbidity: 0.59 NTU, pH: 6.00;

[0064] Example 3: Flocculation effect of different MOG-Fe / Al flocculant dosages

[0065] Take 1 mL of raw slurry wastewater, dilute it 120 times with distilled water, let it stand for 10 min, adjust the pH of the diluted wastewater to 10, and add 0.5-1.5 g of MOG-Fe / Al flocculant (i.e., the mass ratio of MOG-Fe / Al flocculant to the volume of diluted wastewater is 5-15 g: 1 L) under constant temperature water bath conditions of 20℃, and let it stand for sedimentation and flocculation treatment for 1 h. The treatment is then complete.

[0066] This embodiment modifies the mass ratio of MOG-Fe / Al flocculant to diluted wastewater to study the flocculation effect of different MOG-Fe / Al flocculant dosages. The turbidity values ​​of the wastewater before and after flocculation were measured, and the turbidity removal rate was calculated to evaluate the flocculation effect. The results are shown in Table 1. Figure 2 As shown.

[0067] Turbidity removal rate = (Turbidity value before flocculation - Turbidity value after flocculation) / Turbidity value before flocculation × 100%

[0068] Table 1. Flocculation effect of different MOG-Fe / Al flocculant dosages

[0069] MOG-Fe / Al dosage / g 0.5 0.62 0.75 0.79 0.88 1 Turbidity removal rate / % 69 72.2 76.8 79 84.5 88 MOG-Fe / Al dosage / g 1.1 1.2 1.3 1.38 1.5 Turbidity removal rate / % 85 82 80.9 78 76.5

[0070] According to Table 1, Figure 2 It was found that within the dosage range of 0.5-1.0g, the turbidity removal rate gradually increased with increasing dosage. However, within the dosage range of 1.0-1.5g, the removal rate gradually decreased with increasing dosage, with the optimal dosage being 1.0g. This may be because as the flocculant dosage increases, excessive flocculant leads to enhanced interactions between flocculants, forming large flocs. These large flocs may be difficult to settle or filter, thus reducing the flocculation effect. Furthermore, the flocculant may cause changes in the pH of the solution, affecting its performance and consequently the flocculation effect. Once the optimal dosage is reached, further increases in flocculant dosage will not result in flocculation but will instead dissolve in the wastewater, becoming new pollutants. In addition, the flocculant used in the experiment was also colored; excessive addition would cause new pollution to the wastewater.

[0071] Example 4: Flocculation effect of MOG-Fe / Al on wastewater of different concentrations

[0072] Take 1 mL of raw slurry wastewater and dilute it with distilled water 50-550 times. After standing for 10 min, adjust the pH of the diluted wastewater to 10. Under constant temperature water bath conditions of 20℃, add 1.0 g of MOG-Fe / Al flocculant and allow it to settle and flocculate for 1 h. The treatment is then complete.

[0073] This embodiment modifies the dilution ratio of distilled water to the original pulp wastewater to study the flocculation effect of MOG-Fe / Al on wastewater of different concentrations. The turbidity values ​​of the wastewater before and after flocculation were measured, and the turbidity removal rate was calculated to evaluate the flocculation effect. The results are shown in Table 2. Figure 3 As shown.

[0074] Table 2. Flocculation effect of MOG-Fe / Al gel material on wastewater of different concentrations.

[0075] Wastewater dilution ratio 50 100 150 200 250 300 Turbidity removal rate / % 60.4 92.6 89.8 85.4 80.3 74.3 Wastewater dilution ratio 350 400 450 500 550 Turbidity removal rate / % 69.2 67.3 61.2 56.2 45.8

[0076] According to Table 2, Figure 3 When wastewater was diluted 50 times and 1.0g of flocculant was added, the turbidity removal rate was only 60.3%; when diluted 100 times, the removal rate increased to 92.5%. The removal rate gradually decreased with increasing dilution. This is because when the dilution is less than 100 times, the pollutant concentration in the wastewater is too high, and the flocculant is insufficient, reaching its limit; while when the dilution exceeds 100 times, the pollutant concentration is too low, and the flocculant is excessive, some of which fails to function and instead generates new pollutants, leading to an increase in turbidity. This indicates that the optimal treatment concentration is a 100-fold dilution.

[0077] Example 5: Flocculation effect of MOG-Fe / Al on wastewater at different temperatures

[0078] Take 1 mL of raw slurry wastewater, dilute it 100 times with distilled water, let it stand for 10 min, adjust the pH of the diluted wastewater to 10, add 1.0 g of MOG-Fe / Al flocculant under constant temperature water bath conditions at different temperatures (20-70℃), and let it stand for 1 h for sedimentation and flocculation treatment. The treatment is then complete.

[0079] This embodiment modifies the temperature conditions of the flocculation treatment to study the flocculation effect of MOG-Fe / Al at different temperatures. The turbidity values ​​of the wastewater before and after flocculation are measured, and the turbidity removal rate is calculated to evaluate the flocculation effect. The results are shown in Table 3. Figure 4 As shown.

[0080] Table 3. Flocculation effect of MOG-Fe / Al on wastewater at different temperatures.

[0081] Temperature / °C 20 25 30 35 40 45 Turbidity removal rate / % 92.5 94.4 96.4 95.3 94.2 91.3 Temperature / °C 50 55 60 65 70 Turbidity removal rate / % 86.3 86.1 85.8 85.2 85.1

[0082] According to Table 3, Figure 4The wastewater removal rate of MOG-Fe / Al flocculant gradually increased from 20℃ to 30℃, but began to decline above 30℃. At 50℃, the turbidity value showed no significant change, indicating that temperature had a limited effect on the flocculant. At low temperatures, increasing temperature enhanced activity and improved flocculation. However, at excessively high temperatures, some activity decreased, leading to a reduction in turbidity removal rate; subsequently, the activity stabilized, and the turbidity removal rate remained above 80%. At 30℃, the removal rate reached 96.4%, indicating that 30℃ was the optimal operating temperature.

[0083] Example 6: Flocculation effect of MOG-Fe / Al on wastewater with different pH values

[0084] Take 1 mL of raw wastewater from the pulp and add distilled water to dilute it 100 times. After standing for 10 min, adjust the pH of the diluted wastewater to 1-12. Under constant temperature water bath conditions of 30℃, add 1.0 g of MOG-Fe / Al flocculant and allow it to stand for sedimentation and flocculation treatment for 1 h. The treatment is then complete.

[0085] This embodiment modifies the pH conditions of the wastewater during flocculation treatment to study the flocculation effect of MOG-Fe / Al on wastewater at different pH values. The turbidity values ​​of the wastewater before and after flocculation are measured, and the turbidity removal rate is calculated to evaluate the flocculation effect. The results are shown in Table 4. Figure 5 As shown.

[0086] Table 4. Flocculation effect of MOG-Fe / Al on wastewater at different pH levels

[0087] pH 12 11 10 9 8 7 Turbidity removal rate / % 92.8 94.6 96.8 97.2 97.1 95.3 pH 6 5 4 3 2 1 Turbidity removal rate / % 90.2 84.4 78.4 74.3 72.2 69.6

[0088] According to Table 4, Figure 5 It can be seen that MOG-Fe / Al gel flocculant exhibits different flocculation effects in wastewater with different pH values. The turbidity removal rate gradually increases with increasing pH, but begins to decrease after exceeding pH 9, indicating that acidity and alkalinity have a significant impact on its activity. The turbidity removal rate is relatively high in the pH range of 7 to 10.5, possibly because the hydroxyl groups on the adsorbent surface play a key role in the adsorption process. Extreme pH values ​​affect the flocculation effect; the stronger the alkalinity of the solution, the lower the degree of protonation. This is because alkaline solutions contain more hydroxide ions (OH-), leading to a decrease in the protonation of hydrogen ions (H+). + The increased affinity of the alkalinity to the Fe / Al gel reduces the concentration of free hydrogen ions in the solution. Therefore, as alkalinity increases, the acidity (pH value) of the solution rises, and the degree of protonation decreases accordingly. Thus, the optimal pH adjustment when using MOG-Fe / Al gel to treat wastewater is 9.

[0089] Example 7: Effect of different settling times on the flocculation of MOG-Fe / Al

[0090] Take 1 mL of raw slurry wastewater, dilute it 100 times with distilled water, let it stand for 10 min, adjust the pH of the diluted wastewater to 9, add 1.0 g of MOG-Fe / Al flocculant under constant temperature water bath conditions of 30℃, and let it stand for sedimentation and flocculation treatment for 1-12 h respectively, and the treatment is completed.

[0091] This embodiment modifies the settling time of the flocculation treatment to study the flocculation effect of MOG-Fe / Al under different settling times. The turbidity values ​​of the wastewater before and after flocculation were measured, and the turbidity removal rate was calculated to evaluate the flocculation effect. The results are shown in Table 5. Figure 6 As shown.

[0092] Table 5. Flocculation effect of MOG-Fe / Al under different settling times.

[0093] Settling time / h 1 2 3 4 5 6 Turbidity removal rate / % 97.4 97.5 97.6 97.7 97.9 97.9 Settling time / h 7 8 9 10 11 12 Turbidity removal rate / % 98.1 98.2 98.2 98.3 98.3 98.3

[0094] According to Table 5, Figure 6 It can be seen that as the settling time increases, the turbidity removal rate of MOG-Fe / Al gel for wastewater continues to increase, indicating that the longer the settling time, the better the flocculation effect. It is recommended to choose 12h as the optimal treatment time.

[0095] Performance Measurement and Analysis

[0096] The properties of the MOG-Fe / Al, MOG-Fe, and MOG-Al materials obtained in Example 1, Comparative Example 1, and Comparative Example 2 were measured and analyzed, and the results are as follows.

[0097] (1) Scanning electron microscopy (SEM)

[0098] Figure 7 SEM images of MOG-Fe / Al, MOG-Fe, and MOG-Al. (Source: [Insert source here]) Figure 7 As shown in images a, 7b, and 7c, MOG-Fe / Al consists of densely packed, porous colloidal particles resembling coral stones, exhibiting interwoven fibers or particles. The size and distribution of these pores may vary depending on the gel composition and drying conditions. The presence of pores helps to increase the specific surface area of ​​the material, thereby improving its adsorption performance in water treatment. The density and anisotropy of the network on the material surface may affect its physical and chemical properties. The surfaces of MOG-Al and MOG-Fe exhibit irregular morphologies with densely packed protrusions; unlike MOG-Fe / Al, the material surface did not develop a large network structure after drying. Figure 7As shown in d, 7e, and 7f, the morphology of MOG-Fe / Al obtained by 1μm scanning exhibits many rod-shaped attached particles. The MOG-Fe surface resembles volcanic pumice with a small number of particles attached, while the MOG-Al surface is covered with a large number of irregular particles. The shape, size, and distribution of these particles or fibers are also related to the raw materials and preparation process. Observation reveals that the dried gel surface may show varying degrees of roughness.

[0099] (2) Fourier Transform Infrared Spectroscopy (FT-IR)

[0100] Figure 8 The figures show the FT-IR spectra of MOG-Fe / Al, MOG-Fe, and MOG-Al. It can be seen from the figures that all materials show similar performance at 3574 cm⁻¹. -1 Hydroxyl stretching vibration peaks of adsorbed water were observed at all locations, with a peak at 2538 cm⁻¹. -1 The stretching vibration peak of the benzene ring of the organic ligand appeared at 1663 cm⁻¹. -1 A peak of C-C stretching vibration of the aromatic ring in the organic ligand appeared at 1384 cm⁻¹. -1 A symmetric stretching vibration peak of the C=O group of the BTC carboxyl group appeared at 1390 cm⁻¹. -1 The strongest band peak at cm⁻¹ is due to the asymmetric stretching vibration of the carboxylic acid group. The para-substitution peak of the CH disubstituted benzene ring in the fingerprint region appears at 810 cm⁻¹. -1 In addition, at 678cm -1 and 667cm -1 CN fatty alcohol was found in two places.

[0101] (3) X-ray diffraction (XRD)

[0102] XRD patterns of MOG-Fe / Al and MOG-Fe, MOG-Al, as shown Figure 9As shown in the figure. The diffraction peaks of MOG-Fe / Al are strong, but there are broad peaks, which may be due to the amorphous state or low crystallinity. There are many impurity peaks in MOG-Fe and MOG-Al, which further proves that their purity is not high. The relevant peaks of these two MOGs are closely matched, which confirms that the crystal structure of the material remains intact after the change. The broad plate diffraction peaks at 22°-25° prove that the crystallinity of these three samples is poor. There is no long-range order in the structure, indicating that the amorphous structure of the three samples may be more prone to fracture or deformation and has poor thermal stability, affecting the reliability of high-temperature applications. In addition, by analyzing the matching degree of diffraction peaks of these three MOG materials, it was found that after modification with aluminum nitrate nonahydrate and iron nitrate nonahydrate, the samples showed obvious differences in broad peaks, indicating that the crystal structure has changed. The PDF card numbers of the diffraction peaks of the materials are 70-1103 and 70-2161, and when the incident angle of the X-ray beam relative to the surface is 70°, the relative enhancement of the (203) peak indicates that the MOG material has a plane-preferred orientation.

[0103] (4) Thermogravimetric analysis (TG)

[0104] TG plots of MOG-Fe / Al and MOG-Fe, MOG-Al, as shown Figure 10 As shown. At 0–177 °C, a significant mass loss of 14.1%–22.5% was observed in the samples, which is usually related to the evaporation of water or the release of low-volatile components. Water or solvent was released from the gel network during this stage. Between 177 and 322 °C, a significant mass loss of 17.4%–8.3% was observed in the samples. This stage may be related to the loss of organic ligands, polymer degradation, or phase transition. At temperatures of 322–503 °C, the mass loss was 13.4%–34.6%, with the largest loss in MOG-Fe. This can be attributed to the removal of residual solvents and the decomposition of the porous gel matrix. This stage may be due to the decomposition of the molecular skeleton and the loss of remaining organic ligands, leading to some collapse of the MOG skeleton. The residues may involve carbon and iron oxides, which can be attributed to the removal of residual solvents and the decomposition of the porous gel matrix. Above 503 °C, the mass of the samples tended to stabilize, with a final residual mass of 29%–39%. This residual mass can be used to infer the content of inorganic components or carbonization products in the material. (5) X-ray photoelectron spectroscopy (XPS)

[0105] To further analyze the chemical bonding information of MOG-Fe / Al, the material was characterized by XPS. The results are shown in [Figure number missing]. Figure 11 As shown, the binding energy (BEs) peak values ​​are 75.16, 285.21, 407.19, 532.12, and 711.53 eV, indicating the presence of Al, C, N, O, and Fe elements on the sample surface. Figure 11 a). C 1sPeak fitting showed that the peaks at 284.80 and 289.09 eV corresponded to the C—C / C=C and O—C=O bonds of the carboxyl group, respectively. Figure 11 b). Fe 2p High-resolution XPS spectroscopy shows Fe 2+ and Fe 3+ The characteristic peaks of 709.21 and 711.83 eV are attributed to Fe, respectively. 2+ 2p1 / 2 and Fe 3+ 2p2 / 3 Spin orbital splitting, Fe 2+ 2p The satellite peak is located at 715.01 eV Fe. 3+ 2p2 / 3 The satellite peak at 729.36 eV confirms Fe 3+ Coordination with BTC. Al 2p The BE peaks were 72.56 eV and 75.26 eV, corresponding to metallic Al and adsorbed alumina, respectively, further confirming the presence of Al. Figure 11 d). Both MOG-Fe / Al and MOG-FeAl spectra show NO bonds, and MOG-FeAl N 1s The BE peaks are 396.60, 399.31, 400.88, 404.16, and 407.29 eV, corresponding to metal nitrogen compounds, pyrrole nitrogen, and nitrogen oxides, respectively. 1s The fitted curves for the peaks are at 529.29 and 532.10 eV, corresponding to the metal O and CO bonds, respectively. Figure 11 f).

[0106] (6) Specific surface area measurement (BET)

[0107] To determine the pore size distribution and specific surface area of ​​MOG-Fe / Al, N2 adsorption-desorption tests were performed (see...). Figure 12 The MOG-Fe / Al exhibits a Type IV adsorption isotherm, with a hysteresis loop between the adsorption and desorption branches, indicating mesoporous characteristics. Under relative pressures of P / P0 = 0.4–0.8, a significant hysteresis loop exists between the adsorption and desorption branches, suggesting high mesoporosity. Due to the characteristics of the H2(a) type hysteresis loop, desorption curves alone are insufficient; therefore, adsorption curves were used for analysis. Based on the adsorption data, the BET surface area was calculated to be 360.532 m². 2 The large surface area ( / g) endows MOG microcubes with abundant surface active sites, promoting the reaction between molecules and sensing materials. Pore size distribution Figure 13The results show that the average pore sizes of MOG-Fe / Al are concentrated at 1.7 nm, 2.4 nm and 5.0 nm, which belong to micro-mesoporous materials. Moreover, the mesoporous structure is abundant. These structures not only provide numerous active centers for the application of the material, but also facilitate the diffusion of target molecules within the pores.

[0108] In summary, this invention successfully synthesized a metal-organic gel (MOG) material, MOG-Fe / Al, and investigated its flocculation effect on cotton slurry wastewater. The process conditions were optimized, and the properties and structure of the synthesized material were characterized. Results showed that with a MOG-Fe / Al dosage of 1.0 g, wastewater concentration diluted 100 times, pH 9, flocculation temperature of 30℃, and flocculation time of 12 h, the turbidity removal rate of the wastewater reached 98.3%. This is related to the differences in pore size, channel number, gel properties of aluminum and iron, and internal structure. Characterization results showed that the material had a rough surface and a dense mesh distribution. The MOG-Fe / Al obtained in this invention exhibits excellent flocculation performance in cotton textile wastewater treatment and has significant application potential. This invention prepares a novel, highly efficient flocculation agent, MOG-Fe / Al, for cotton textile wastewater treatment, providing a feasible new solution for wastewater treatment in the Xinjiang Uygur Autonomous Region and offering a new approach to cotton slurry wastewater treatment.

[0109] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for treating pulp and slag wastewater using a MOG-Fe / Al flocculant with a coral-like shape, characterized in that, Includes the following steps: (1) Preparation of MOG-Fe / Al flocculant: Aluminum nitrate, ferric nitrate, and trimellitic acid were mixed, and ethanol was added. The mixture was stirred and dissolved at room temperature. A hydrothermal synthesis reaction was then carried out under sealed conditions. After the reaction, the mixture was cooled to room temperature and freeze-dried to obtain the final product. The molar ratio of aluminum nitrate, ferric nitrate, and trimellitic acid was 15:10:(16-17); the mass ratio of trimellitic acid to ethanol was (4-5) g:70 mL; the stirring time was 20-30 min; the hydrothermal synthesis reaction temperature was 120-150℃ and the time was 1-3 h; the freeze-drying temperature was -60~-65℃ and the time was 12-24 h. (2) Dilute the pulp and cypress wastewater and let it stand; adjust the pH and temperature of the diluted wastewater, add MOG-Fe / Al flocculant, and let it settle to complete the treatment; the dilution ratio of the pulp and cypress wastewater is 50-550 times; the settling time after dilution is 10-20 min; adjust the pH of the diluted pulp and cypress wastewater to 6-12 and the temperature to 20-70℃; the mass ratio of the added MOG-Fe / Al flocculant to the volume of the diluted pulp and cypress wastewater is 5-15 g:1 L; the settling time after adding MOG-Fe / Al flocculant is 1-12 h; the pulp and cypress wastewater comes from the pulp and paper industry and is black liquor produced during wood processing and pulp extraction; the UV of the pulp and cypress wastewater 600 ≥2, Turbidity ≥35 NTU, pH ≥11.

2. The method as described in claim 1, characterized in that, In step (2), the dilution factor of the cypress wastewater is 100 times.

3. The method as described in claim 1, characterized in that, In step (2), the pH of the diluted pulp wastewater is adjusted to 9 and the temperature is 30℃.

4. The method as described in claim 1, characterized in that, In step (2), the mass ratio of the added MOG-Fe / Al flocculant to the volume of the diluted pulp wastewater is 10g:1L; the settling time after adding MOG-Fe / Al flocculant is 12h.

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