Biomass flocculant as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of deep sea plume inhibition, and particularly relates to a biomass flocculant as well as a preparation method and application thereof. The raw materials comprise sodium alginate, acrylamide and dodecane dimethyl betaine, and the ratio of the mass of the sodium alginate to the volume of the acrylamide to the volume of the dodecane dimethyl betaine is 1g: (2-4) g: (0.5-1) ml. Natural or bio-based materials such as sodium alginate, acrylamide and dodecane dimethyl betaine are adopted as main components, marine polysaccharide is fully utilized as a raw material, and dodecane dimethyl betaine introduced to flocculant material molecules can reduce the viscosity of a flocculant solution, so that the requirements on pipelines and pumping devices are reduced, and the cost is reduced. And the pumping efficiency of the flocculating agent is improved, the damage of the deep sea plume to the ecological environment is effectively inhibited, and good economic benefits and environmental benefits are achieved. The product is non-toxic and harmless, has good biodegradability, and avoids the potential harm of the traditional inorganic flocculant to the deep sea ecological environment.

Description

Technical Field

[0001] The invention belongs to the technical field of deep-sea plume suppression, and in particular relates to a biomass flocculant and a preparation method and application thereof. Background Art

[0002] Deep-sea sediments are mainly composed of marine biological remains, autogenous sediments, aeolian dust, cosmic dust, volcanic ash, terrigenous clay colloids and ice raft debris. These sediments are the result of biological and chemical reactions, and also contain materials from land, volcanoes and the universe. During deep-sea observations, the descent of manned submersibles will cause severe disturbance of sediments, seriously affecting the observation field of view and accuracy. In the deep-sea mining process, the mining, crushing and lifting of minerals will lead to large-scale plume diffusion. The plumes generated by human activities will not only seriously damage the deep-sea ecosystem, but also cause the suffocation of benthic organisms. At the same time, the large amount of heavy metal ions released with the plumes may cause biological deformation or even death. Therefore, it is urgent to develop a flocculant and its preparation method that can effectively inhibit the generation and diffusion of deep-sea plumes.

[0003] Flocculation technology is the core technology for industrial and environmental water treatment, and the research and development of related flocculation materials has become the key to improving the flocculation and sedimentation of particulate matter in water. Inorganic flocculants are widely used because of their low cost and ease of use, while organic polymer flocculants such as polyacrylamide have the ability to flocculate efficiently at low dosages. However, high metal concentrations and difficult-to-degrade polymer flocculants may cause unpredictable harm to the fragile deep-sea ecological environment, and the monomer residues of flocculation materials may have physiological toxic effects on deep-sea organisms. Biopolymer-based flocculants have aroused widespread interest among researchers because of their biodegradable and environmentally friendly advantages. A variety of green flocculants have been developed or designed to improve the flocculation process in wastewater treatment, providing a reference for the research and development of plume-suppressing flocculation materials in special deep-sea environments.

[0004] Marine polysaccharides, a class of compounds widely found in marine organisms, have shown unique advantages in the treatment of underflows in deep-sea mining due to their rich renewability, non-toxic and degradable properties, and excellent shear stability. The use of marine polysaccharides as flocculation materials not only makes full use of their unique properties, but also vividly embodies the concept of sustainable development of marine resources of "taking from the sea and using it in the sea". Taking into account the actual application effect and economic cost, the common marine polysaccharide flocculation materials on the market are mainly high-molecular flocculants based on chitosan and sodium alginate. Chitosan can form a cationic polyelectrolyte with high charge density in an acidic environment, showing good complexation and flocculation properties. However, in the low temperature and weak alkaline environment of the deep sea, its relatively small molecular weight and weak bridging ability limit the realization of its ideal flocculation effect.

[0005] Sodium alginate is a common heavy metal remover for water treatment. Its macromolecular structure is excellent in coagulation. Usually, sodium alginate needs a certain amount of Ca in the water. 2+ The concentration of sodium alginate can play an effective flocculation effect, and usually a large amount of it is needed to achieve the ideal flocculation effect, but too high a metal ion concentration will remain in the deep-sea environment. Therefore, it is a key issue in deep-sea plume management to improve the flocculation effect of sodium alginate on deep-sea sediments through reasonable chemical modification methods and develop biomass flocculants suitable for low temperature, weak alkaline, and high-salt environments to minimize the impact of flocculation operations on the deep-sea environment. However, there is no relevant literature report. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a biomass flocculant and a preparation method and application thereof, which fully utilizes marine polysaccharides as raw materials. The dodecane dimethyl betaine introduced into the flocculant material molecules can reduce the viscosity of the flocculant solution, thereby reducing the requirements for pipelines and pumping devices, improving the flocculant pumping efficiency, and effectively inhibiting the damage of deep-sea plumes to the ecological environment, with good economic and environmental benefits.

[0007] The technical solutions adopted are:

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

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

[0010] (1) Sodium alginate is completely dissolved in deionized water, and nitrogen is continuously introduced to remove oxygen in the system; an initiator is added and the reaction is carried out for 10 to 20 minutes;

[0011] (2) completely dissolving acrylamide in deionized water, adding the acrylamide to the reaction system and continuously stirring the acrylamide, and continuously reacting the acrylamide after the addition is completed;

[0012] (3) adding acetic acid to adjust the pH of the solution to 4-6, and adding dodecane dimethyl betaine dropwise to the reaction system. After the addition is completed, the reaction is continued;

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

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

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

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

[0017] In step (1), nitrogen should be passed to ensure that the nitrogen effectively covers the surface of the solution to form 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 temperature of the reaction system is maintained at a constant temperature of 60° C., and the rate at which the deionized aqueous solution of acrylamide is added to the reaction system of step (1) is controlled at 1 to 10 ml / min. Slow addition of acrylamide helps control the reaction rate and reactant concentration, and prevents excessive polymerization from causing excessive viscosity of the system or uneven reaction.

[0020] Preferably, the stirring speed is 200-300 rpm, and the reaction time is 1-3 hours, and the more preferred reaction time is 2 hours.

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

[0022] Preferably, in step (3), the reaction temperature is maintained at 45-55°C. A more preferred reaction temperature is 50°C.

[0023] Preferably, in step (3), the reaction process is continuously protected by nitrogen, and the reaction time is 1 to 2 hours. The solution pH is more preferably pH = 5. The rate of dodecane dimethyl betaine addition is set as required, and the drop rate can be 1 to 10 mL / min.

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

[0025] Preferably, in the 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 biomass flocculant prepared by the present invention is used to inhibit the generation and diffusion of deep-sea plume.

[0027] Principle of the present invention:

[0028] The molecular chain of natural polymer sodium alginate is rich in hydroxyl (-OH) and carboxyl (-COO-). By introducing the initiator potassium persulfate, the hydroxyl on the molecular chain of sodium alginate is activated, so that it can react chemically with the carbon-carbon double bond (C=C) in acrylamide, so that acrylamide is successfully grafted onto the molecular chain of sodium alginate. Further, through the polymerization reaction of the double bond of acrylamide, a polyacrylamide side chain is constructed on the main chain of the sodium alginate molecule. Furthermore, the amphoteric surfactant dodecyl dimethyl betaine exhibits cationic properties in an acidic medium. There is an adsorption effect of opposite charges between the carboxyl groups on the main chain of the sodium alginate molecule, which enables dodecyl dimethyl betaine to be stably attached to the polymer main chain of sodium alginate. The reaction process is as follows:

[0029]

[0030] The present invention provides a biomass flocculant (SA-PAM-BS12) and a preparation method and application thereof. Compared with the prior art, the present invention has the following beneficial effects:

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

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

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

[0034] 4) In response to the sediment plume problem generated during deep-sea mining, the present 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 dodecane dimethyl betaine introduced into the flocculant material molecules can reduce the viscosity of the flocculant solution, thereby reducing the requirements for pipelines and pumping devices and improving the flocculant pumping efficiency.

[0036] 6) When the flocculant material is added to the deep sea environment, the molecular side chains of the flocculant material will be expanded and stretched under weak alkaline conditions due to the mutual repulsion between the negatively charged groups, forming flocculant molecules that further promote the bridging effect. At the same time, through the synergistic effect of dodecane dimethyl betaine and polyacrylamide, the flocculation and sedimentation of deep sea plume particles can be significantly promoted.

[0037] 7) Dodecane dimethyl betaine, as a surfactant molecule, has a positively charged quaternary ammonium group and a negatively charged carboxyl group, which changes the surface charge density of the particles and effectively enhances the adsorption capacity between particles. The long-chain alkyl on dodecane dimethyl betaine can be adsorbed to the surface of sediment particles, enhancing the hydrophobicity of the particle surface and promoting the aggregation of particles through hydrophobic interactions. At the same time, its amphoteric surfactant characteristics can connect particles with different surface characteristics and promote mutual attraction and aggregation between particles. After dodecane dimethyl betaine provides the initial particle aggregation conditions, polyacrylamide will quickly form flocs through the adsorption bridging effect of its polymer chain, accelerate the growth and sedimentation of flocs, aggregate insoluble complexes and form larger network flocs to make them settle quickly. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0039] Figure 2 The X-ray diffraction spectra of the flocculant material and sodium alginate prepared in the present invention are shown. DETAILED DESCRIPTION

[0040] The accompanying drawings are only for illustrative purposes; the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. If no specific conditions are specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0041] Example 1

[0042] Take 2g of sodium alginate and put it in a 500mL three-necked flask, add 300ml of deionized water, stir until the sodium alginate is completely dissolved, heat in a water bath to 60° and keep constant temperature, insert the nitrogen pipe head below the liquid surface, stir for 10min while passing nitrogen, add initiator potassium persulfate so that the initiator concentration in the reaction system is 10mmol / L, and stir for 10min under 60°C water bath heating conditions;

[0043] Dissolve 6 g of acrylamide in 50 ml of deionized water, slowly add it dropwise into a three-necked flask and continue stirring at 250 rpm. Keep stirring at 60 °C for 2 hours.

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

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

[0046] The prepared flocculant material was dissolved in pure water and stirred until completely dissolved, and the concentrations were configured to be 0.01 g / L, 0.1 g / L, 0.5 g / L, 1 g / L, and 2 g / L to obtain biomass flocculant SA-AM-BS12 of different concentrations.

[0047] See also Figure 1 The infrared characterization diagram of the flocculating material of the present invention and sodium alginate shows that the infrared spectrum of the flocculant material is significantly different from that of the raw material. Specifically, the absorption peak at 1658 cm-1 shows the stretching vibration characteristics of the C=O bond in the primary amide group, and the absorption peak at 1200 cm-1 reflects the stretching vibration of the CO bond in the fatty ether structure. Compared with the typical characteristic peak of the hydroxyl group in the raw material, the morphology of this peak in the product is significantly narrowed, indicating a decrease in the molecular weight of the hydroxyl group in the product, from which 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 dodecane dimethyl betaine molecules are effectively attached to the main chain of sodium alginate through intermolecular interactions.

[0049] Through infrared analysis of the flocculation material, it can be seen that the main functional groups in the product structure are amide group, ether group, carboxyl group and amino group, which means that the product has no biological toxicity and can be naturally degraded. It is safe and environmentally friendly. Compared with traditional flocculants, it greatly improves the safety of use and reduces secondary pollution.

[0050] Figure 2The X-ray diffraction spectra of the flocculation material of the present invention and sodium alginate are shown, indicating that the flocculation material has multiple obvious diffraction peaks. There is a broad diffraction peak between 10° and 25°. Peak No. 2 coincides with the peak position of the (-311) plane of polyacrylamide, Peak No. 1 is slightly offset to a lower angle compared with its (200) plane, and the diffraction intensity is enhanced, while Peak No. 2 is offset to a high angle relative to the (111) plane, and the diffraction intensity is weakened, indicating that the crystal plane is preferentially oriented to Peak No. 1. In addition, the diffraction intensity of Peaks No. 3 and No. 4 is enhanced relative to the (-512) and (511) planes of polyacrylamide, and the diffraction intensity of Peak No. 2 is several times that of the (400) plane. The shift, broadening and intensity changes of other peaks indicate that the crystal is attached to the main chain of sodium alginate. Combined with the infrared spectrum results, it is shown that dodecyl dimethyl betaine is introduced into the main chain of sodium alginate during the polymerization of polyacrylamide.

[0051] Example 2

[0052] Take 2g of sodium alginate and put it in a 500mL three-necked flask, add 300ml of deionized water, stir until the sodium alginate is completely dissolved, heat in a water bath to 55° and keep constant temperature, insert the nitrogen pipe head below the liquid surface, stir for 10min while passing nitrogen, add initiator potassium persulfate so that the initiator concentration in the reaction system is 10mmol / L, and stir for 10min under 55°C water bath heating conditions;

[0053] Dissolve 8 g of acrylamide in 50 ml of deionized water, slowly add it dropwise into a three-necked flask and continue stirring at 250 rpm. Keep stirring at 60 °C for 1 hour.

[0054] Maintain the reaction at 55°C, add acetic acid to adjust the solution pH to 5, then add 1 mL of dodecyl dimethyl betaine to the three-necked flask, and continue the reaction for 1 hour after the addition is completed. Nitrogen is continuously passed through the reaction process for protection; after the reaction is completed, air is passed through to stop the reaction, and a light yellow translucent liquid is obtained. The product is cooled to room temperature, and sufficient acetone is added to precipitate a viscous polymer. After a white precipitate is produced, it is filtered, and the product is vacuum dried at 60°C for 24 hours to obtain a crude graft copolymer product;

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

[0056] The prepared flocculant material was dissolved in pure water and stirred until completely dissolved, and the concentrations were configured to be 0.01 g / L, 0.1 g / L, 0.5 g / L, 1 g / L, and 2 g / L to obtain biomass flocculant SA-AM-BS12 of different concentrations.

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

[0058] Comparative Example 1:

[0059] Dissolve sodium alginate in pure water, heat in a water bath and stir until completely dissolved, and prepare sodium alginate flocculants with concentrations of 0.01g / L, 0.1g / L, 0.5g / L, 1g / L, and 2g / L.

[0060] Comparative Example 2:

[0061] Dissolve anionic polyacrylamide with a molecular weight of 12-14 million in pure water, heat in a water bath and stir until completely dissolved, and prepare polyacrylamide flocculants with concentrations of 0.01g / L, 0.1g / L, and 0.5g / L. Since the viscosity of polyacrylamide is too high at high concentrations and it is difficult to pump, this comparative example does not consider polyacrylamide flocculants greater than 0.5g / L.

[0062] Application test: Configuration of in-situ sediment simulated water samples in deep-sea polymetallic nodule mining areas

[0063] Weigh 2g of deep-sea in-situ sediments and add them to 1000ml of seawater overlying the sediments, and keep them at 4℃ for 24h to simulate the low-temperature environment of the deep sea. Take out the simulated water sample and stir it continuously for 1min to prepare a simulated water sample simulating the presence of deep-sea plumes.

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

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

[0066] Table 1 Turbidity NTU change rate of simulated water samples treated with different flocculants

[0067]

[0068] As shown in the treatment results in Table 1, SA-AM-BS12 at the same dosage exhibits a stronger flocculation and sedimentation effect than PAM, its injection resistance is significantly reduced compared with PAM, and the plume flow treatment effect is obvious. SA-AM-BS12 under different preparation conditions achieved in the claims still has a good flocculation and sedimentation effect on deep-sea sediments.

[0069] The English abbreviations used in this invention refer to their Chinese meanings.

[0070] SA: sodium alginate;

[0071] AM: acrylamide;

[0072] BS12: Dodecyl dimethyl betaine.

[0073] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A biomass flocculant, characterized in that: The raw materials include sodium alginate, acrylamide and dodecane dimethyl betaine, wherein the mass ratio of the sodium alginate and acrylamide to the volume ratio of the dodecane dimethyl betaine is 1g: (2-4)g: (0.5-1)ml.

2. The method for preparing a biomass flocculant according to claim 1, characterized in that: The steps include: (1) Sodium alginate is completely dissolved in deionized water, and nitrogen is continuously introduced to remove oxygen in the system; an initiator is added and the reaction is carried out for 10 to 20 minutes; (2) completely dissolving acrylamide in deionized water, adding the acrylamide to the reaction system and continuously stirring the acrylamide, and continuously reacting the acrylamide after the addition is completed; (3) adding acetic acid to adjust the pH of the solution to 4-6, and adding dodecane dimethyl betaine dropwise to the reaction system. After the addition is completed, the reaction is continued; (4) After the reaction is completed, air is introduced to stop the reaction, and a light yellow translucent liquid is obtained; The product was cooled to room temperature, acetone was added to precipitate a viscous polymer, a white precipitate was generated, and the precipitate was filtered and dried to obtain a crude graft copolymer product; (5) The obtained crude product is placed in a mixture of formamide / acetic acid to remove homopolymers in the product. The filtered precipitate is repeatedly washed and then dried to obtain the final product.

3. The method for preparing a biomass flocculant according to claim 2, characterized in that: In the step (1), the system temperature is maintained at 55-70° C., the initiator is potassium persulfate, and the amount of potassium persulfate added is (10-50) mmol / L.

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

5. The method for preparing a biomass flocculant according to claim 4, characterized in that: The stirring speed is 200-300 rpm, and the reaction time is 1-3 hours.

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

7. The method for preparing a biomass flocculant according to claim 2, characterized in that: In the step (3), nitrogen protection is continuously passed during the reaction process, and the reaction time is 1 to 2 hours.

8. The method for preparing a biomass flocculant according to claim 2, characterized in that: In the step (4), the product is vacuum dried at 50-65° C. for 12-24 hours.

9. The method for preparing a biomass flocculant according to claim 2, characterized in that: In the 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.

10. Use of the biomass flocculant prepared by the preparation method according to any one of claims 1 or 2 to 9 in inhibiting the generation and diffusion of deep-sea plumes.

Images