Modified sodium alginate, method for preparing the same, and use thereof

Abstract

The application relates to the technical field of adsorbents, in particular to modified sodium alginate as well as a preparation method and application thereof; the preparation raw materials of the modified sodium alginate include sodium alginate, an activating agent, a mercapto reagent, a carboxylic acid compound containing an unsaturated double bond and an initiator. The application adopts natural polysaccharide sodium alginate as raw materials, which is widely sourced, non-toxic and biodegradable; a functional group carboxyl is introduced into the sodium alginate through a mercapto-alkene click reaction; the surface adsorption active sites of the modified sodium alginate are increased; the modified sodium alginate can effectively adsorb and remove methylene blue and ciprofloxacin in water; and the modified sodium alginate can still maintain good adsorption performance after being subjected to multiple cycles of adsorption-desorption.

Description

Technical Field

[0001] This application relates to the field of adsorbents, specifically to a modified sodium alginate, its preparation method, and its application. Background Technology

[0002] Water scarcity caused by water pollution has seriously affected human life and sustainable development, and solving water pollution is a major challenge facing the world today. Adsorption, due to its advantages such as being environmentally friendly, simple to operate, low in investment cost, and recyclable, has become a cost-effective technology. As the core of adsorption technology, improving the economy and adsorption performance of adsorbents is key to optimizing and upgrading adsorption technology.

[0003] Therefore, it is crucial to develop an adsorbent with good adsorption properties. Summary of the Invention

[0004] In view of the above problems, this application provides a modified sodium alginate, its preparation method and application. The modified sodium alginate can effectively adsorb and remove methylene blue and ciprofloxacin in water, and can maintain good adsorption performance after multiple cycles of adsorption-desorption.

[0005] In a first aspect, this application provides a modified sodium alginate, wherein the raw materials for preparing the modified sodium alginate include sodium alginate, an activator, a thiolizing agent, a carboxylic acid compound containing an unsaturated double bond, and an initiator.

[0006] Due to their abundant sources, renewability, biodegradability, biocompatibility, and environmental friendliness, polysaccharides, a type of natural polymer, have attracted widespread attention in the water treatment field. Adsorbents with active functional groups (such as -OH, -COOH, -SH, -NH2, etc.) can adsorb pollutants such as dyes or antibiotics through ion exchange, coordination, chelation, and electrostatic adsorption, thereby achieving the purpose of pollutant removal. Therefore, functional modification of polysaccharide materials can increase their adsorption sites, thereby enhancing their adsorption capacity for pollutants in water.

[0007] Click chemistry aims to rapidly and efficiently construct compounds by assembling small units, offering advantages such as high selectivity, rapid reaction, simple and mild conditions, few side reactions, and high yields. Click chemistry allows for the modular introduction of adsorption functional groups, thereby developing adsorbents rich in functional groups.

[0008] In the technical solution of this application, natural polysaccharide sodium alginate is used as raw material. It is widely available, non-toxic, biodegradable, and has the advantages of being green and environmentally friendly. The functional group carboxyl is introduced into sodium alginate through a mercapto-olefin click reaction. The surface adsorption active sites of the modified sodium alginate are increased, which can effectively adsorb and remove methylene blue and ciprofloxacin in water. It also has the advantage of being reusable and can maintain good adsorption performance after multiple cycles of adsorption-desorption.

[0009] Preferably, the molar ratio of the activator to sodium alginate is (0.5-2):1, wherein 0.5-2 can be 0.7, 1, 1.2, 1.5, 1.7, etc.

[0010] Preferably, the activator comprises N-hydroxysuccinimide and / or 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride.

[0011] Preferably, the molar ratio of N-hydroxysuccinimide to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is (0.5-1.5):1, wherein 0.5-1.5 can be 0.6, 0.8, 1, 1.2, 1.4, etc.

[0012] Preferably, the molar ratio of the thiolated reagent to sodium alginate is (0.5-2):1, wherein 0.5-2 can be 0.7, 1, 1.2, 1.5, 1.7, etc.

[0013] In the technical solution of this application, the molar ratio of thiolated reagent and sodium alginate within the above range can ensure effective reaction between reactants and maximize grafting efficiency. If the thiolated reagent is excessive, it may lead to cross-linking between or within molecules, reducing the efficiency of the grafting reaction. If the sodium alginate is excessive, it means that the supply of thiolated reagent is insufficient, resulting in incomplete grafting reaction.

[0014] Preferably, the thiolation agent includes a thiol group as well as a carboxyl group and / or an amino group.

[0015] Preferably, the thiolation agent includes any one or a combination of at least two of cysteine, mercaptoacetic acid, or mercaptopropionic acid, with cysteine ​​being more preferred.

[0016] Preferably, the molar ratio of the carboxylic acid compound containing unsaturated double bonds to sodium alginate is (1-2):1, wherein 1-2 can be 1.2, 1.4, 1.6, 1.8, etc.

[0017] Preferably, the carboxylic acid compound containing unsaturated double bonds includes acrylic acid compounds.

[0018] Preferably, the molar ratio of the initiator to the carboxylic acid compound containing unsaturated double bonds is (0.1-0.5):1, wherein 0.1-0.5 can be 0.2, 0.3, 0.4, etc.

[0019] Preferably, the initiator comprises 2,2-dimethylolpropionic acid.

[0020] Secondly, this application provides a method for preparing the modified sodium alginate described in the first aspect, the method comprising the following steps:

[0021] Sodium alginate, activator, thiolizing agent, carboxylic acid compound containing unsaturated double bonds and initiator are mixed and subjected to thiol-alkene click reaction to obtain the modified sodium alginate.

[0022] In the technical solution of the embodiments of this application, thiol-alkene click reaction modified sodium alginate is obtained through thiol-alkene click reaction. The preparation process is simple and low-cost, and can be applied to large-scale industrial production.

[0023] Preferably, the preparation method includes the following steps:

[0024] (1) Sodium alginate, activator and solvent are mixed to obtain sodium alginate solution;

[0025] (2) Mix sodium alginate solution and thiolation reagent, react under light-protected conditions, adjust pH to obtain thiolation sodium alginate solution;

[0026] (3) Under an inert atmosphere, the initiator, a carboxylic acid compound containing an unsaturated double bond and a mercapto-modified sodium alginate solution are mixed and reacted to obtain the modified sodium alginate.

[0027] Preferably, in step (1), the solvent includes water.

[0028] Preferably, sodium alginate and solvent are mixed first, and then mixed with activator.

[0029] Preferably, in step (2), the thiolation reagent is first formed into a thiolation reagent solution and then mixed with sodium alginate solution.

[0030] Preferably, in step (2), the reaction time is 2-3 h, for example 2.2 h, 2.4 h, 2.6 h, 2.8 h, etc.

[0031] Preferably, in step (2), the pH is adjusted to 7-8, for example, 7.2, 7.4, 7.6, 7.8, etc.

[0032] In the technical solution of this application, the solution after mixing the thiolizing agent and sodium alginate solution is weakly acidic. Adjusting the pH to weakly alkaline allows the thiol group (-SH) to more easily lose a proton and form -S. - The presence of anions increases reactivity, while simultaneously reducing the reactivity of the carboxylic acid group (-COOH), thereby minimizing side reactions.

[0033] Preferably, in step (2), after adjusting the pH, the reaction continues for 1-2 hours, for example, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, etc.

[0034] Preferably, in step (3), the initiator and the carboxylic acid compound containing unsaturated double bonds are first mixed in a solvent to form a mixed solution.

[0035] Preferably, in step (3), the reaction is carried out under ultraviolet light irradiation.

[0036] Preferably, in step (3), the reaction time is 3-4 h.

[0037] As an example, in step (3), the reaction also includes post-processing, such as placing the reaction mixture in an alcohol solvent such as ethanol, separating the precipitate, and then drying it. The drying temperature can be 40-80℃, such as 50℃, 60℃, 70℃, etc.

[0038] As an example, in this application, the mixing in step (1), the mixing in step (2), the reaction, the pH adjustment and the continued reaction, and the mixing and reaction in step (3) are each carried out independently at 10-45°C, such as 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, etc.; for ease of operation, they can be carried out directly at room temperature.

[0039] As a preferred technical solution, the preparation method includes the following steps:

[0040] (1) Dissolve sodium alginate in a solvent and then mix it with an activator to obtain a sodium alginate solution;

[0041] (2) Mix sodium alginate solution and thiolation reagent solution, react under light-protected conditions for 2-3 h, adjust pH to 7-8, and continue reaction for 1-2 h to obtain thiolation sodium alginate solution;

[0042] (3) Under an inert atmosphere, the initiator and a mixed solution of a carboxylic acid compound containing unsaturated double bonds are mixed with a solution of thiolated sodium alginate and reacted under ultraviolet light for 3-4 h to obtain the modified sodium alginate.

[0043] Thirdly, this application provides an adsorbent comprising the modified sodium alginate described in the first aspect, or the modified sodium alginate obtained by the preparation method described in the second aspect.

[0044] Preferably, the adsorbent is used for water treatment.

[0045] Compared with the prior art, the technical solution of this application has at least the following advantages:

[0046] (1) This application uses natural polysaccharide sodium alginate as raw material, which is widely available, non-toxic, biodegradable, green and environmentally friendly, and has no secondary pollution.

[0047] (2) This application introduces the functional group carboxyl group into sodium alginate through a mercapto-olefin click reaction. The surface adsorption active sites of the modified sodium alginate are increased, which can effectively adsorb and remove methylene blue and ciprofloxacin in water. The modified sodium alginate is reusable and can maintain good adsorption performance after multiple cycles of adsorption-desorption.

[0048] (3) The preparation method described in this application is simple to operate and has mild reaction conditions, and can be applied to large-scale industrial production.

[0049] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0050] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0051] Figure 1 The flowchart shows the preparation process of the modified sodium alginate obtained in Example 1.

[0052] Figure 2 The infrared spectrum of the modified sodium alginate obtained in Example 1;

[0053] Figure 3 This is a scanning electron microscope image of the mercapto-olefin click reaction modified sodium alginate obtained in Example 1;

[0054] Figure 4 for Figure 3 A magnified view of a portion of the image;

[0055] Figure 5Here is a scanning electron microscope image of the thiolated sodium alginate obtained in Example 1;

[0056] Figure 6 for Figure 5 A magnified view of a portion of the image;

[0057] Figure 7 The adsorption effect of thiolated sodium alginate and thio-alkene click reaction modified sodium alginate obtained in Example 1 on methylene blue under different pH conditions;

[0058] Figure 8 The adsorption effect of ciprofloxacin on sodium alginate modified by click reaction with thiolized sodium alginate and thiol-alkene obtained in Example 1 under different pH conditions is shown.

[0059] Figure 9 The adsorption effect of the mercapto-olefin click reaction modified sodium alginate obtained in Example 1 on methylene blue and ciprofloxacin after five cycles of adsorption-desorption is shown. Detailed Implementation

[0060] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0062] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0063] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0064] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is also expected that ranges of 60–110 and 80–120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "2-10" indicates that all real numbers between "2-10" have been listed in this article; "2-10" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0065] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0066] Example 1

[0067] This embodiment provides a modified sodium alginate, which is obtained by the following preparation method, as shown in the schematic diagram. Figure 1 As shown, the preparation method includes the following steps:

[0068] (1) Sodium alginate was dissolved in 60 mL of pure water. Then, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were added. The molar ratio of sodium alginate, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was 1:1:1. The mixture was activated at room temperature for 1 h. Then, cysteine ​​was added. The molar ratio of sodium alginate and cysteine ​​was 1:1.5. The mixture was reacted under light-protected conditions for 2 h. The pH was adjusted to 7 and the reaction was continued for 1 h.

[0069] (2) Add 5 mL of 2,2-dimethylolpropionic acid and acrylic acid dissolved in pure water to the thiolated sodium alginate solution obtained in step (1), with the molar ratio of cysteine, acrylic acid and 2,2-dimethylolpropionic acid being 1:1:0.3. Irradiate the mixture solution with a 365 nm ultraviolet lamp under nitrogen conditions and stir for 3 h.

[0070] (3) The mixture solution obtained in step (2) is placed in an ethanol solution, the precipitate is separated, and it is dried at 60°C to obtain mercapto-olefin click reaction modified sodium alginate, namely the modified sodium alginate.

[0071] Example 2

[0072] This embodiment provides a modified sodium alginate, which is obtained by the following preparation method, which includes the following steps:

[0073] (1) Sodium alginate was dissolved in 60 mL of pure water. Then, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were added. The molar ratio of sodium alginate, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was 1:1:1. The mixture was activated at room temperature for 1 h. Then, cysteine ​​was added. The molar ratio of sodium alginate and cysteine ​​was 1:1. The mixture was reacted under light-protected conditions for 2 h. The pH was adjusted to 7 and the reaction was continued for 1 h.

[0074] (2) Add 5 mL of 2,2-dimethylolpropionic acid and acrylic acid dissolved in pure water to the thiolated sodium alginate solution obtained in step (1), with the molar ratio of cysteine, acrylic acid and 2,2-dimethylolpropionic acid being 1:1:0.3. Irradiate the mixture solution with a 365 nm ultraviolet lamp under nitrogen conditions and stir for 3 h.

[0075] (3) The mixture solution obtained in step (2) is placed in an ethanol solution, the precipitate is separated, and it is dried at 60°C to obtain mercapto-olefin click reaction modified sodium alginate, namely the modified sodium alginate.

[0076] Example 3

[0077] This embodiment provides a modified sodium alginate, which is obtained by the following preparation method, which includes the following steps:

[0078] (1) Sodium alginate was dissolved in 60 mL of pure water. Then, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were added. The molar ratio of sodium alginate, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was 1:1:1. The mixture was activated at room temperature for 1 h. Then, cysteine ​​was added. The molar ratio of sodium alginate and cysteine ​​was 1:2. The mixture was reacted under light-protected conditions for 2 h. The pH was adjusted to 7 and the reaction was continued for 1 h.

[0079] (2) Add 5 mL of 2,2-dimethylolpropionic acid and acrylic acid dissolved in pure water to the thiolated sodium alginate solution obtained in step (1), with the molar ratio of cysteine, acrylic acid and 2,2-dimethylolpropionic acid being 1:1:0.3. Irradiate the mixture solution with a 365 nm ultraviolet lamp under nitrogen conditions and stir for 3 h.

[0080] (3) The mixture solution obtained in step (2) is placed in an ethanol solution, the precipitate is separated, and it is dried at 60°C to obtain mercapto-olefin click reaction modified sodium alginate, namely the modified sodium alginate.

[0081] Example 4

[0082] This embodiment provides a modified sodium alginate, which is obtained by the following preparation method, which includes the following steps:

[0083] (1) Sodium alginate was dissolved in 60 mL of pure water. Then, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were added. The molar ratio of sodium alginate, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was 1:1:1. The mixture was activated at room temperature for 1 h. Then, cysteine ​​was added. The molar ratio of sodium alginate and cysteine ​​was 1:0.5. The mixture was reacted under light-protected conditions for 2 h. The pH was adjusted to 7 and the reaction was continued for 1 h.

[0084] (2) Add 5 mL of 2,2-dimethylolpropionic acid and acrylic acid dissolved in pure water to the thiolated sodium alginate solution obtained in step (1), with the molar ratio of cysteine, acrylic acid and 2,2-dimethylolpropionic acid being 1:1:0.3. Irradiate the mixture solution with a 365 nm ultraviolet lamp under nitrogen conditions and stir for 3 h.

[0085] (3) The mixture solution obtained in step (2) is placed in an ethanol solution, the precipitate is separated, and it is dried at 60°C to obtain mercapto-olefin click reaction modified sodium alginate, namely the modified sodium alginate.

[0086] Example 5

[0087] This embodiment provides a modified sodium alginate, which is obtained by the following preparation method, which includes the following steps:

[0088] (1) Sodium alginate was dissolved in 60 mL of pure water. Then, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were added. The molar ratio of sodium alginate, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was 1:1:1. The mixture was activated at room temperature for 1 h. Then, cysteine ​​was added. The molar ratio of sodium alginate and cysteine ​​was 1:1. The mixture was reacted under light-protected conditions for 2 h. The pH was adjusted to 7 and the reaction was continued for 1 h.

[0089] (2) Add 5 mL of 2,2-dimethylolpropionic acid and acrylic acid dissolved in pure water to the thiolated sodium alginate solution obtained in step (1), with the molar ratio of cysteine, acrylic acid and 2,2-dimethylolpropionic acid being 1:2:0.5. Irradiate the mixture solution with a 365 nm ultraviolet lamp under nitrogen conditions and stir for 3 h.

[0090] (3) The mixture solution obtained in step (2) is placed in an ethanol solution, the precipitate is separated, and it is dried at 60°C to obtain mercapto-olefin click reaction modified sodium alginate, namely the modified sodium alginate.

[0091] Comparative Example 1

[0092] This comparative example provides a modified sodium alginate, which is obtained by the following preparation method, which includes the following steps:

[0093] (1) Sodium alginate was dissolved in 60 mL of pure water. Then, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were added. The molar ratio of sodium alginate, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was 1:1:1. The mixture was activated at room temperature for 1 h. Then, cysteine ​​was added. The molar ratio of sodium alginate and cysteine ​​was 1:1. The mixture was reacted under light-protected conditions for 2 h. The pH was adjusted to 7 and the reaction was continued for 1 h.

[0094] (2) The mixture solution obtained in step (1) is placed in an ethanol solution, the precipitate is separated, and dried at 60°C to obtain thiolated sodium alginate.

[0095] Performance testing

[0096] (1) Structural characterization

[0097] Taking Example 1 and Comparative Example 1 as examples, the structure of sodium alginate modified by click reaction with cysteine ​​and mercapto-ene was characterized, such as... Figure 2As shown, the infrared spectrum of thiol-olefin click reaction modified sodium alginate shows a peak at 2591 cm⁻¹. -1 The characteristic peak of the thiol group disappears at 1024 cm⁻¹, and at 1024 cm⁻¹... -1 The presence of a characteristic CSC peak at 2591 cm⁻¹ confirms that acrylic acid was grafted onto thiolated sodium alginate via a thiol-olefin click reaction. The thiolated sodium alginate showed a peak at 2591 cm⁻¹. -1 The peak at the position is a characteristic peak of thiol (-SH), indicating that sodium alginate was successfully grafted with cysteine.

[0098] (2) Morphological test

[0099] Taking Example 1 and Comparative Example 1 as examples, their morphologies were observed and compared using scanning electron microscopy, and the results are as follows: Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, the scanning electron microscope image of sodium alginate relative to thiolated sodium alginate (Comparative Example 1) is as follows (e.g.) Figure 5 and Figure 6 The click-modified sodium alginate obtained in this application (Example 1) is as follows: Figure 3 and Figure 4 As shown, many evenly distributed fine needle-like textures appear on the surface, indicating a change in the morphology of the adsorbent; the surface of thiolized sodium alginate is rough with no obvious textures, which is significantly different from the surface morphology of thiol-alkene click reaction modified sodium alginate.

[0100] (3) Adsorption performance

[0101] 1) Using mercapto-olefin click reaction modified sodium alginate as an adsorbent, the adsorption capacity for methylene blue under different pH conditions was investigated. The initial concentration of methylene blue was 100 mg·L⁻¹. -1 Taking Example 1 as an example, the results are as follows: Figure 7 As shown, the adsorption capacity of the adsorbent remains at 450 mg·g over a wide pH range. -1 This is due to the electrostatic interaction between the mercapto-olefin click reaction modified sodium alginate and methylene blue.

[0102] 2) Using mercapto-olefin click reaction modified sodium alginate as an adsorbent, the adsorption capacity of ciprofloxacin was investigated under different pH conditions. The initial concentration of ciprofloxacin was 50 mg·L⁻¹. -1 Taking Example 1 as an example, the results are as follows: Figure 8 As shown, under acidic conditions, a large number of hydrogen ions exist in the solution, competing with the cationic ciprofloxacin for adsorption, resulting in no significant increase in adsorption capacity. When the pH increases, the number of hydrogen ions in the solution decreases, and the cationic ciprofloxacin interacts electrostatically with the mercapto-olefin click-modified sodium alginate adsorbent, achieving the best adsorption effect with an adsorption capacity of 211.1 mg·g⁻¹.-1 As pH continues to increase, ciprofloxacin gradually exists in the aqueous solution in anionic form. There is electrostatic repulsion between the adsorbent and the pollutant, so the adsorption capacity of the adsorbent for ciprofloxacin decreases.

[0103] 3) The adsorption-desorption of sodium alginate modified by the click reaction of mercapto-olefin was investigated after multiple uses to explore the adsorption of methylene blue and ciprofloxacin. Taking Example 1 as an example, the results are as follows: Figure 9 As shown, the adsorption of methylene blue is almost unaffected after multiple uses, and although the adsorption efficiency of ciprofloxacin decreases, it still maintains a high removal rate.

[0104] To facilitate further comparison, the test results of the adsorption performance of each implementation method are summarized in Table 1. The reaction temperature during the performance test was 25°C; the dosage of adsorbent was 0.2 g·L⁻¹. -1 The methylene blue solution had a volume of 50 mL, a pH of 10, and an initial concentration of 100 mg·L⁻¹. -1 The ciprofloxacin solution volume was 50 mL, pH 4, and the initial concentration was 50 mg·L⁻¹. -1 .

[0105] Table 1

[0106]

[0107] Analysis of Comparative Example 1 and Example 1 shows that the performance of Comparative Example 1 is not as good as that of Example 1, proving that the modified sodium alginate obtained by the preparation method described in this application has better adsorption performance.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A modified sodium alginate, characterized in that, The preparation raw material of the modified sodium alginate comprises sodium alginate, an activating agent, a mercapto reagent, a carboxylic compound containing unsaturated double bonds and an initiator; The mercapto reagent is cysteine; The activating agent comprises N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride; The molar ratio of the mercapto reagent to the sodium alginate is (0.5-2):1; The molar ratio of the carboxylic compound containing unsaturated double bonds to the sodium alginate is (1-2):1; The modified sodium alginate is prepared by the following preparation method, which comprises the following steps: (1) mixing the sodium alginate, the activating agent and a solvent to obtain a sodium alginate solution; (2) mixing the sodium alginate solution and the mercapto reagent, reacting under light-proof conditions, adjusting pH to obtain a mercapto sodium alginate solution; (3) mixing the initiator, the carboxylic compound containing unsaturated double bonds and the mercapto sodium alginate solution under an inert atmosphere, and reacting to obtain the modified sodium alginate.

2. The modified sodium alginate according to claim 1, characterized in that, The molar ratio of the activating agent to the sodium alginate is (0.5-2):

1.

3. The modified sodium alginate according to claim 1, characterized in that, The molar ratio of the N-hydroxysuccinimide to the 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride is (0.5-1.5):

1.

4. The modified sodium alginate according to claim 1, characterized in that, The carboxylic compound containing unsaturated double bonds comprises an acrylic compound.

5. The modified sodium alginate according to claim 1, wherein, The molar ratio of the initiator to the carboxylic compound containing unsaturated double bonds is (0.1-0.5):

1.

6. A process for the preparation of the modified sodium alginate according to any one of claims 1 to 5, characterized in that, The preparation method comprises the following steps: The preparation method comprises the following steps: (1) mixing the sodium alginate, the activating agent and a solvent to obtain a sodium alginate solution; (2) mixing the sodium alginate solution and the mercapto reagent, reacting under light-proof conditions, adjusting pH to obtain a mercapto sodium alginate solution; (3) mixing the initiator, the carboxylic compound containing unsaturated double bonds and the mercapto sodium alginate solution under an inert atmosphere, and reacting to obtain the modified sodium alginate.

7. The production method according to claim 6, wherein In step (1), the solvent comprises water.

8. The preparation method according to claim 6, characterized in that, The sodium alginate is first mixed with the solvent, and then mixed with the activating agent.

9. The preparation method according to claim 6, characterized in that, In step (2), the mercapto reagent is first formed into a mercapto reagent solution, and then mixed with the sodium alginate solution.

10. The production method according to claim 6, characterized by, In step (2), the reaction time is 2-3 h.

11. The method of claim 6, wherein, In step (2), the pH is adjusted to 7-8.

12. The production method according to claim 6, characterized by, In step (2), after the pH is adjusted, the reaction is continued for 1-2 h.

13. The preparation method according to claim 6, characterized in that, In step (3), before the initiator and the carboxylic compound containing unsaturated double bonds are mixed, a mixed solution is first formed in a solvent.

14. The method of claim 6, wherein, In step (3), the reaction is carried out under ultraviolet light irradiation.

15. The method of claim 6, wherein, In step (3), the reaction time is 3-4 h.

16. The method of claim 6, wherein, The preparation method comprises the following steps: (1) dissolving the sodium alginate in a solvent, and then mixing with the activating agent to obtain a sodium alginate solution; (2) mixing the sodium alginate solution and the mercapto reagent solution, reacting under light-proof conditions for 2-3 h, adjusting the pH to 7-8, and continuing the reaction for 1-2 h to obtain a mercapto sodium alginate solution; (3) mixing the initiator and the mixed solution of the carboxylic acid compound containing unsaturated double bond and the thiolated sodium alginate solution under inert atmosphere, and irradiating under ultraviolet light for 3-4 hours to obtain the modified sodium alginate.

17. An adsorbent, characterized in that, The adsorbent comprises the modified sodium alginate according to any one of claims 1-5, or the modified sodium alginate obtained by the preparation method according to any one of claims 6-16.

18. The adsorbent of claim 17, wherein, The adsorbent is used for water treatment.

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