Biomass flocculant, preparation method and application thereof

Abstract

The present application belongs to the technical field of deep-sea plume suppression, and particularly relates to a biomass flocculant, a preparation method and application thereof. The raw materials include sodium alginate, acrylamide and dodecane dimethyl betaine, wherein the mass ratio of sodium alginate and acrylamide to the volume of dodecane dimethyl betaine is 1g:(2-4)g:(0.5-1)ml. The present application uses natural or bio-based materials such as sodium alginate, acrylamide and dodecane dimethyl betaine as main components, fully utilizes marine polysaccharides as raw materials, and introduces dodecane dimethyl betaine on the molecule of the flocculant material to reduce the viscosity of the flocculant solution, thereby reducing the requirements on the pipeline and pumping device, improving the pumping efficiency of the flocculant, effectively suppressing the damage of the deep-sea plume to the ecological environment, and having good economic and environmental benefits. The product is non-toxic and has good biodegradability, avoiding the potential harm of traditional inorganic flocculants to the deep-sea ecological environment.

Description

Technical Field

[0001] This invention belongs to the field of deep-sea plume suppression technology, specifically relating to a biomass flocculant, its preparation method, and its application. Background Technology

[0002] Deep-sea sediments are primarily composed of marine biological remains, authigenic sediments, aeolian dust, cosmic dust, volcanic ash, terrigenous clay colloids, and ice raft debris. These sediments are the result of biological and chemical processes, and also contain materials from land, volcanoes, and space. During deep-sea observation, manned submersible descents cause severe disturbance to sediments, significantly impacting the observation field of view and accuracy. Furthermore, deep-sea mining processes, including mining, crushing, and hoisting, generate large-scale plumes. These plumes, generated by human disturbance, not only severely damage deep-sea ecosystems but also suffocate benthic organisms. The large amounts of heavy metal ions released with these plumes can lead to biological mutations or even death. Therefore, there is an urgent need to develop a flocculant and its preparation method to effectively suppress the generation and diffusion of deep-sea plumes.

[0003] Flocculation technology is a core technology in industrial and environmental water treatment, and the development of related flocculant materials is crucial for improving the flocculation and sedimentation of particulate matter in water. Inorganic flocculants are widely used due to their low cost and ease of use, while organic polymeric flocculants such as polyacrylamide have the ability to achieve high-efficiency flocculation at low dosages. However, high metal concentrations and recalcitrant polymeric flocculants may cause unpredictable harm to the fragile deep-sea ecosystem, and the monomer residues of flocculant materials may have physiological toxic effects on deep-sea organisms. Biopolymer-based flocculants have attracted widespread interest from researchers due to their biodegradability and environmental friendliness. Various green flocculants have been developed or designed to improve the flocculation process in wastewater treatment, providing a reference for the development of plume-suppressing flocculant materials in special deep-sea environments.

[0004] Marine polysaccharides, compounds widely found in marine organisms, exhibit unique advantages in bottom current treatment during deep-sea mining due to their abundant renewability, non-toxicity, biodegradability, and excellent shear stability. Utilizing marine polysaccharides as flocculants not only fully leverages their unique properties but also vividly embodies the sustainable development concept of "taking from the sea and using it for the sea." Considering both practical application effects and economic costs, commercially available marine polysaccharide flocculants are primarily high-molecular-weight flocculants based on chitosan and sodium alginate. Chitosan can form high-charge-density cationic polyelectrolytes in acidic environments, exhibiting good complexing and flocculation properties. However, in the low-temperature, weakly alkaline environment of the deep sea, its relatively small molecular weight and weak bridging ability limit its ideal flocculation effect.

[0005] Sodium alginate, a common heavy metal removal agent in water treatment, exhibits excellent coagulation aid properties due to its large molecular structure. Typically, sodium alginate requires a certain amount of calcium in water. 2+ Effective flocculation requires specific concentrations, typically necessitating large-scale application to achieve optimal results. However, excessively high metal ion concentrations can leave residues in the deep-sea environment. Therefore, enhancing the flocculation effect of sodium alginate on deep-sea sediments through appropriate chemical modification, and developing biomass flocculants suitable for low-temperature, weakly alkaline, and high-salinity environments to minimize the impact of flocculation operations on the deep-sea environment, are key issues in deep-sea plume management. However, no relevant literature has yet been reported. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a biomass flocculant, its preparation method and application. It makes full use of marine polysaccharides as raw materials. The dodecanedimethyl betaine introduced into the flocculant material molecule can reduce the viscosity of the flocculant solution, thereby reducing the requirements for pipelines and pumping devices, improving the pumping efficiency of the flocculant, and effectively suppressing the damage of deep-sea plumes to the ecological environment. It has good economic and environmental benefits.

[0007] The technical solution adopted is as follows:

[0008] A biomass flocculant (SA-AM-BS12) comprises sodium alginate, acrylamide, and dodecanedimethyl betaine as raw materials, wherein the mass ratio of sodium alginate and acrylamide to the volume ratio of dodecanedimethyl betaine is 1 g : (2-4) g : (0.5-1) ml. A more preferred ratio is 1 g : 3 g : 0.5 ml.

[0009] A method for preparing a biomass flocculant includes the following steps:

[0010] (1) Dissolve sodium alginate completely in deionized water and continuously purge with nitrogen to remove oxygen from the system; add initiator and react for 10-20 min.

[0011] (2) Dissolve acrylamide completely in deionized water, add it to the reaction system and stir continuously. Continue the reaction after the addition is complete.

[0012] (3) Add acetic acid to adjust the pH of the solution to 4-6, and add dodecanedimethyl betaine dropwise to the reaction system. After the addition is complete, continue the reaction.

[0013] (4) After the reaction is complete, air is introduced to stop the reaction, and a pale yellow translucent liquid is obtained;

[0014] The product was cooled to room temperature, and sufficient acetone was added to precipitate the viscous polymer. After a white precipitate was formed, the product was filtered and dried to obtain the crude graft copolymer product.

[0015] (5) The crude product is placed in a mixture of formamide / acetic acid to remove the homopolymer in the product. The filtered precipitate is repeatedly washed and dried to obtain the final product.

[0016] Preferably, in step (1), the system temperature is maintained at 55-70°C, and more preferably the reaction temperature is 60°C.

[0017] In step (1), nitrogen gas should be introduced to ensure that nitrogen effectively covers the surface of the solution, forming a nitrogen protective layer to prevent oxygen from entering the reaction system and maintain an inert atmosphere for the reaction.

[0018] The initiator is potassium persulfate, and the amount of potassium persulfate added is (10-50) mmol / L.

[0019] Preferably, in step (2), the reaction system temperature is maintained at a constant 60°C, and the rate at which the deionized aqueous solution of acrylamide is added to the reaction system in step (1) is controlled at 1–10 ml / min. Slowly adding acrylamide helps control the reaction rate and reactant concentration, preventing excessively rapid polymerization that could lead to excessively high system viscosity or uneven reaction.

[0020] Preferably, the stirring speed is 200–300 rpm, and the reaction time is 1–3 h. More preferably, the reaction time is 2 h.

[0021] The structure of the polymer formed by adding acrylamide in the reaction is closely related to its addition rate and stirring intensity. A moderate stirring speed helps to form the desired graft copolymer structure and ensures the functional properties of the flocculant.

[0022] Preferably, in step (3), the reaction temperature is maintained at 45–55°C. More preferably, the reaction temperature is 50°C.

[0023] Preferably, in step (3), the reaction process is continuously protected by nitrogen gas for 1-2 hours. The solution pH is more preferably pH=5. The rate of dodecanedimethylbetaine addition is set as needed, and the dropping rate can be 1-10 mL / min.

[0024] Preferably, in step (4), the product is vacuum dried at 50-65°C for 12-24 hours.

[0025] Preferably, in step (5), the ratio of formamide to acetic acid in the formamide / acetic acid mixture is 1:1; the filtered precipitate is repeatedly washed with methanol, and then the filtered precipitate is vacuum dried at 50-65°C for 12-24 hours.

[0026] The application of the biomass flocculant prepared in this invention in suppressing the generation and diffusion of deep-sea plumes.

[0027] The principle of this invention:

[0028] Sodium alginate, a natural polymer, is rich in hydroxyl (-OH) and carboxyl (-COO-) groups on its molecular chain. By introducing potassium persulfate as an initiator, the hydroxyl groups on the sodium alginate molecular chain are activated, allowing them to chemically react with the carbon-carbon double bonds (C=C) in acrylamide. This successfully grafts acrylamide onto the sodium alginate molecular chain. Further polymerization of the acrylamide double bonds constructs polyacrylamide side chains on the sodium alginate main chain. Furthermore, the amphoteric surfactant dodecyl dimethyl betaine exhibits cationic properties in acidic media. The carboxyl groups on the sodium alginate main chain exhibit opposite intermolecular charges, allowing dodecyl dimethyl betaine to stably attach to the sodium alginate polymer main chain. The reaction process is as follows:

[0029]

[0030] This invention provides a biomass flocculant (SA-PAM-BS12), its preparation method, and its application. Compared with the prior art, the advantages of this invention are as follows:

[0031] 1) This invention uses natural or bio-based materials such as sodium alginate, acrylamide and dodecanedimethyl betaine as the main components. The product is non-toxic and has good biodegradability, avoiding the potential harm of traditional inorganic flocculants (such as aluminum salts and iron salts) to the deep-sea ecological environment and reducing the impact on fragile ecosystems.

[0032] 2) Compared with high molecular weight polyacrylamide, the biomass flocculant of the present invention has a better flocculation effect on deep-sea soil samples, and the product can be flexibly extended to multiple fields such as drinking water treatment and sedimentation of suspended sediment in estuaries and coastlines, and has broad application prospects.

[0033] 3) This invention makes full use of marine polysaccharides as raw materials, embodying the sustainable development concept of "taking from the sea and using it for the sea", and has good economic and environmental benefits.

[0034] 4) In response to the problem of sediment plumes generated during deep-sea mining, this invention provides a new countermeasure that can effectively suppress the damage of deep-sea plumes to the ecological environment by enhancing particle settling.

[0035] 5) The dodecanedimethyl betaine introduced into the flocculant material molecule can reduce the viscosity of the flocculant solution, thereby reducing the requirements for pipelines and pumping devices and improving the pumping efficiency of flocculants.

[0036] 6) When this flocculant material is added to the deep-sea environment, under weakly alkaline conditions, the mutual repulsion between negatively charged groups will expand and stretch the molecular branches of the flocculant material, forming flocculant molecules that further promote bridging. At the same time, through the synergistic effect of dodecanedimethyl betaine and polyacrylamide, it can significantly promote the flocculation and sedimentation of deep-sea plume particles.

[0037] 7) Dodecanedimethyl betaine, as a surfactant molecule, possesses positively charged quaternary ammonium groups and negatively charged carboxyl groups, altering the surface charge density of particles and effectively enhancing their adsorption capacity. The long-chain alkyl groups on dodecanedimethyl betaine can adsorb onto the surface of sediment particles, enhancing their hydrophobicity and promoting aggregation through hydrophobic interactions. Simultaneously, its amphoteric surfactant properties allow it to connect particles with different surface characteristics, promoting mutual attraction and aggregation. After dodecanedimethyl betaine provides the initial conditions for particle aggregation, polyacrylamide, through the adsorption bridging effect of its polymer chains, rapidly forms flocs, accelerating floc growth and sedimentation, aggregating insoluble complexes to form larger network flocs that settle quickly. Attached Figure Description

[0038] Figure 1 The infrared spectra of the flocculant material prepared in this invention and sodium alginate are shown.

[0039] Figure 2 The X-ray diffraction patterns of the flocculant material prepared in this invention and sodium alginate are shown. Detailed Implementation

[0040] The accompanying drawings are for illustrative purposes only. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0041] Example 1

[0042] Take 2g of sodium alginate and place it in a 500mL three-necked flask. Add 300mL of deionized water and stir until the sodium alginate is completely dissolved. Heat the flask in a water bath to 60°C and keep it at a constant temperature. Insert the nitrogen gas tube into the liquid surface and stir while purging nitrogen gas for 10 minutes. Add potassium persulfate as an initiator to make the concentration of the initiator in the reaction system 10mmol / L. Stir for 10 minutes under a 60°C water bath heating condition.

[0043] Dissolve 6g of acrylamide in 50ml of deionized water, slowly add it dropwise to a three-necked flask and stir continuously at 250rpm. Maintain the temperature at 60℃ and continue stirring for 2 hours.

[0044] The reaction temperature was lowered to 50°C, and acetic acid was added dropwise to adjust the pH of the solution to 5. Then, 1 mL of dodecyl dimethyl betaine was added dropwise to a three-necked flask. After the addition was complete, the reaction was continued for 2 hours under nitrogen protection. After the reaction was completed, air was purged to stop the reaction, yielding a pale yellow, translucent liquid. The product was cooled to room temperature, and sufficient acetone was added to precipitate the viscous polymer. After a white precipitate was formed, the product was filtered, and then vacuum dried at 60°C for 24 hours to obtain the crude graft copolymer product.

[0045] The crude product was placed in a mixture of formamide and acetic acid at a ratio of 1:1 to remove homopolymers from the product. The filtered precipitate was repeatedly washed with methanol to remove the solvent, and then the filtered precipitate was vacuum dried at 60°C for 24 hours to obtain the biomass flocculant material.

[0046] The prepared flocculant material was dissolved in pure water and stirred until completely dissolved to prepare concentrations of 0.01 g / L, 0.1 g / L, 0.5 g / L, 1 g / L, and 2 g / L, thus obtaining biomass flocculant SA-AM-BS12 with different concentrations.

[0047] See Figure 1 The infrared characterization images of the flocculant material and sodium alginate of this invention show significant differences between the infrared spectra of the flocculant material and the raw material. Specifically, the absorption peak at 1658 cm⁻¹ indicates the stretching vibration of the C=O bond in the primary amide group, while the absorption peak at 1200 cm⁻¹ reflects the stretching vibration of the CO bond in the aliphatic ether structure. Compared with the typical characteristic peak of hydroxyl groups in the raw material, the peak in the product is significantly narrower, indicating a reduction in the molecular weight of hydroxyl groups in the product. Based on this, it can be inferred that acrylamide has been successfully grafted onto the sodium alginate matrix.

[0048] The characteristic absorption peak at 1126 cm⁻¹ is attributed to the stretching vibration of the CN bond, while the absorption peak at 1417 cm⁻¹ represents the result of the symmetric vibration of the CNC structural unit, indicating that the dodecanedimethyl betaine molecule is effectively attached to the sodium alginate backbone through intermolecular interactions.

[0049] Infrared analysis of the flocculant material revealed that the main functional groups in the product structure are amide, ether, carboxyl, and amino groups, indicating that the product is non-toxic and biodegradable, and has the characteristics of safety and environmental protection. Compared with traditional flocculants, it greatly improves the safety of use and reduces secondary pollution.

[0050] Figure 2The X-ray diffraction patterns of the flocculant material and sodium alginate of the present invention are shown, indicating that the flocculant material has multiple distinct diffraction peaks. Broad diffraction peaks exist between 10° and 25°. Peak 2 coincides with the (-311) plane peak of polyacrylamide. Peak 1 is slightly shifted to a lower angle compared to its (200) plane, and its diffraction intensity is enhanced. Peak 2, however, is shifted to a higher angle relative to the (111) plane, and its diffraction intensity is weakened, indicating that the preferred crystal orientation is peak 1. Furthermore, the diffraction intensities of peaks 3 and 4 are enhanced relative to the (-512) and (511) planes of polyacrylamide, and the diffraction intensity of peak 2 is several times that of the (400) plane. The shifts, broadening, and intensity changes of other peaks indicate that crystallization is attached to the sodium alginate backbone. Combined with the infrared spectroscopy results, it is shown that dodecyl dimethyl betaine is introduced into the sodium alginate backbone during the polymerization of polyacrylamide.

[0051] Example 2

[0052] Take 2g of sodium alginate and place it in a 500mL three-necked flask. Add 300mL of deionized water and stir until the sodium alginate is completely dissolved. Heat the flask in a water bath to 55°C and keep it at a constant temperature. Insert the nitrogen gas tube into the liquid surface and stir while purging nitrogen for 10 minutes. Add potassium persulfate as an initiator to make the concentration of the initiator in the reaction system 10mmol / L. Stir for 10 minutes under a 55°C water bath heating condition.

[0053] Dissolve 8g of acrylamide in 50ml of deionized water, slowly add it dropwise to a three-necked flask and stir continuously at 250rpm. Maintain the temperature at 60℃ and continue stirring for 1 hour.

[0054] The reaction mixture was kept at 55°C, and acetic acid was added dropwise to adjust the pH of the solution to 5. Then, 1 mL of dodecyl dimethyl betaine was added dropwise to a three-necked flask. After the addition was complete, the reaction was continued for 1 hour under nitrogen protection. After the reaction was completed, air was purged to stop the reaction, yielding a pale yellow, translucent liquid. The product was cooled to room temperature, and sufficient acetone was added to precipitate the viscous polymer. After a white precipitate was formed, the mixture was filtered, and the product was vacuum dried at 60°C for 24 hours to obtain the crude graft copolymer product.

[0055] The crude product was placed in a mixture of formamide and acetic acid at a ratio of 1:1 to remove homopolymers from the product. The filtered precipitate was repeatedly washed with methanol to remove the solvent, and then the filtered precipitate was vacuum dried at 60°C for 24 hours to obtain the biomass flocculant material.

[0056] The prepared flocculant material was dissolved in pure water and stirred until completely dissolved to prepare concentrations of 0.01 g / L, 0.1 g / L, 0.5 g / L, 1 g / L, and 2 g / L, thus obtaining biomass flocculant SA-AM-BS12 with different concentrations.

[0057] Compared with Example 1, Example 2 simplifies the control of the reaction system temperature during the preparation process and shortens the reaction time.

[0058] Comparative Example 1:

[0059] Sodium alginate was dissolved in purified water and heated in a water bath with stirring until completely dissolved, to prepare sodium alginate flocculants with concentrations of 0.01 g / L, 0.1 g / L, 0.5 g / L, 1 g / L, and 2 g / L.

[0060] Comparative Example 2:

[0061] Anionic polyacrylamide with a molecular weight of 12-14 million was dissolved in pure water and heated in a water bath with stirring until completely dissolved, preparing polyacrylamide flocculants with concentrations of 0.01 g / L, 0.1 g / L, and 0.5 g / L. Because high concentrations of polyacrylamide have excessively high viscosity, making pumping difficult, this comparative example does not consider polyacrylamide flocculants with concentrations greater than 0.5 g / L.

[0062] Application Experiment: Preparation of Simulated Water Samples from In-situ Sediments in Deep-Sea Polymetallic Nodule Mining Areas

[0063] Weigh 2g of deep-sea in-situ sediment and add it to 1000ml of seawater covering the sediment. Incubate at 4℃ for 24 hours to simulate the low-temperature environment of the deep sea. Take out the simulated water sample and stir continuously for 1 minute to prepare a simulated water sample for the presence of a deep-sea plume.

[0064] The flocculants prepared in Comparative Example 1, Comparative Example 2, Example 1, and Example 2 were injected into simulated water samples prepared under the same conditions to simulate the plume treatment effect of the flocculants being pumped into the deep sea environment, and the changes in turbidity of the simulated water samples were recorded.

[0065] Because deep-sea plumes have a wide diffusion range and long suspension time, the treatment of deep-sea plumes focuses more on the rapid settling of the plumes. Therefore, the turbidity residual rate, i.e., the ratio of the turbidity of the simulated water sample to the original turbidity after 30 minutes of flocculant addition, is used to characterize the treatment effect of flocculants on deep-sea plumes. The turbidity NTU change rate of simulated water samples treated with different flocculants is shown in Table 1.

[0066] Table 1. Change rate of turbidity NTU in simulated water samples treated with different flocculants

[0067]

[0068] As shown in Table 1, the treatment results indicate that SA-AM-BS12, at the same dosage, exhibits a stronger flocculation and sedimentation effect compared to PAM, with significantly reduced injection resistance and a noticeable effect on plume treatment. SA-AM-BS12, prepared under different conditions according to the claims, still demonstrates good flocculation and sedimentation effects on deep-sea sediments.

[0069] The Chinese meanings of the English abbreviations used in this invention.

[0070] SA: Sodium alginate;

[0071] AM: Acrylamide;

[0072] BS12: Dodecanedimethylbetaine.

[0073] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing a biomass flocculant, characterized in that, The raw materials include sodium alginate, acrylamide, and dodecanedimethyl betaine, wherein the mass ratio of sodium alginate and acrylamide to the volume ratio of dodecanedimethyl betaine is 1 g : (2-4) g : (0.5-1) mL. The preparation method includes the following steps: (1) Sodium alginate is completely dissolved in deionized water, and nitrogen is continuously introduced to remove oxygen from the system; the system temperature is maintained at 55-70℃, an initiator is added, and the reaction is carried out for 10-20 min; the initiator is potassium persulfate, and the amount of potassium persulfate added is 10-50 mmol / L; (2) Dissolve acrylamide completely in deionized water, add it to the reaction system and stir continuously. Continue the reaction after the addition is complete. (3) Add acetic acid to adjust the pH of the solution to 4-6, add dodecanedimethyl betaine dropwise to the reaction system, and continue the reaction after the addition is completed; (4) After the reaction is complete, air is introduced to stop the reaction, and a pale yellow translucent liquid is obtained; The product was cooled to room temperature, and acetone was added to precipitate the viscous polymer. After a white precipitate was formed, the product was filtered and dried to obtain the crude graft copolymer product. (5) The crude product is placed in a mixture of formamide / acetic acid to remove the homopolymer in the product. The filtered precipitate is repeatedly washed and dried to obtain the final product.

2. The method for preparing a biomass flocculant according to claim 1, characterized in that, In step (2), the temperature of the reaction system is kept constant at 60°C, and the rate at which the deionized aqueous solution of acrylamide is added to the reaction system in step (1) is controlled at 1 to 10 mL / min.

3. The method for preparing a biomass flocculant according to claim 2, characterized in that, The stirring speed is 200-300 rpm, and the reaction time is 1-3 hours.

4. The method for preparing a biomass flocculant according to claim 2, characterized in that, In step (3), the reaction temperature is maintained at 45-55°C.

5. The method for preparing a biomass flocculant according to claim 1, characterized in that, In step (3), the reaction process is continuously protected by nitrogen gas for 1 to 2 hours.

6. The method for preparing a biomass flocculant according to claim 1, characterized in that, In step (4), the product is vacuum dried at 50-65°C for 12-24 hours.

7. The method for preparing a biomass flocculant according to claim 1, characterized in that, In step (5), the filtered precipitate is repeatedly washed with methanol, and then the filtered precipitate is vacuum dried at 50-65°C for 12-24 hours.

8. The application of the biomass flocculant prepared by the preparation method according to any one of claims 1-7 in suppressing the generation and diffusion of deep-sea plumes.

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