Modified sodium alginate as well as preparation method and application thereof

Abstract

The invention relates to the technical field of adsorbents, in particular to modified sodium alginate as well as a preparation method and application thereof. The modified sodium alginate is prepared from the following raw materials: sodium alginate, an activating agent, a sulfhydrylation reagent, a carboxylic acid compound containing unsaturated double bonds and an initiator. Natural polysaccharide sodium alginate is adopted as a raw material, the natural polysaccharide sodium alginate is wide in source, non-toxic and biodegradable, a functional group carboxyl is introduced into sodium alginate through a thiol-ene click reaction, adsorption active sites on the surface of the modified sodium alginate are increased, methylene blue and ciprofloxacin in water can be effectively adsorbed and removed, and the service life of the modified sodium alginate is prolonged. And after multiple times of cyclic adsorption-desorption, relatively good adsorption performance can be maintained.

Description

Technical Field

[0001] The present application relates to the field of adsorbents, and in particular to a modified sodium alginate and a preparation method and application thereof. Background Art

[0002] The shortage of water resources caused by water pollution has seriously affected human life and sustainable development. Solving the water pollution problem is a major challenge facing the world today. Adsorption has become a cost-effective technology due to its advantages such as green environmental protection, simple operation, low investment cost and recyclability. As the core of adsorption technology, improving the economy and adsorption performance of adsorbents is the key to optimizing and upgrading adsorption technology.

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

[0004] In view of the above problems, the present application provides a modified sodium alginate and a preparation method and application thereof. 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, the present application provides a modified sodium alginate, wherein raw materials for preparing the modified sodium alginate include sodium alginate, an activator, a thiol-forming agent, a carboxylic acid compound containing an unsaturated double bond, and an initiator.

[0006] Polysaccharides in natural polymer materials have the advantages of abundant sources, renewable, biodegradable, biocompatible and green environmental protection, and polysaccharide-based adsorbents have attracted widespread attention in the field of water treatment. 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, electrostatic adsorption, etc., thereby achieving the purpose of removing pollutants. Therefore, the polysaccharide material can be functionalized to increase its adsorption sites, thereby improving its adsorption capacity for pollutants in water.

[0007] Click chemistry aims to quickly and efficiently construct compounds by splicing small units, and has the advantages of good selectivity, rapid reaction, simple and mild conditions, few side reactions, and high yield. Click chemistry can be used to modularly introduce functional groups with adsorption effects, thereby developing adsorbents rich in functional groups.

[0008] In the technical scheme of the implementation mode of the present application, natural polysaccharide sodium alginate is used as raw material, which has a wide source, is non-toxic, biodegradable, and has the advantages of being green and environmentally friendly; the functional group carboxyl is introduced into the sodium alginate through the thiol-ene click reaction, and the adsorption active sites on the surface of the modified sodium alginate are increased, which can effectively adsorb and remove methylene blue and ciprofloxacin in water, and 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 thiol-forming agent 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 the implementation mode of the present application, the molar ratio of the thiolating agent and sodium alginate is within the above range to ensure effective reaction between the reactants and maximize the grafting efficiency; if the thiolating agent is excessive, it may cause cross-linking between molecules or within molecules, reducing the efficiency of the grafting reaction; if the sodium alginate is excessive, it means that the thiolating agent is insufficiently supplied, resulting in incomplete grafting reaction.

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

[0015] Preferably, the thiolating agent comprises any one of cysteine, thioglycolic acid or mercaptopropionic acid, or a combination of at least two thereof, and cysteine ​​is further preferred.

[0016] Preferably, the molar ratio of the carboxylic acid compound containing an unsaturated double bond 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 an unsaturated double bond includes an acrylic acid compound.

[0018] Preferably, the molar ratio of the initiator to the carboxylic acid compound containing an unsaturated double bond 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] In a second aspect, the present application provides a method for preparing the modified sodium alginate according to the first aspect, the preparation method comprising the following steps:

[0021] Sodium alginate, an activator, a thiol-forming agent, a carboxylic acid compound containing an unsaturated double bond and an initiator are mixed to carry out a thiol-ene click reaction to obtain the modified sodium alginate.

[0022] In the technical solution of the implementation mode of the present application, thiol-ene click reaction-modified sodium alginate is obtained through thiol-ene click reaction, which has a simple preparation process and low cost and can be applied to large-scale industrial production.

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

[0024] (1) mixing sodium alginate, an activator and a solvent to obtain a sodium alginate solution;

[0025] (2) mixing the sodium alginate solution and the thiol reagent, reacting them in a light-proof condition, and adjusting the pH to obtain a thiolated sodium alginate solution;

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

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

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

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

[0030] Preferably, in step (2), the reaction time is 2-3 h, such as 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, such as 7.2, 7.4, 7.6, 7.8, etc.

[0032] In the technical solution of the embodiment of the present application, the solution after the thiol-reactive agent and the sodium alginate solution are mixed is weakly acidic. When the pH is adjusted to a weakly alkaline state, the thiol (-SH) can more easily lose protons to form -S - The anion increases the reaction activity, while the activity of the carboxylic acid group (-COOH) decreases, thereby reducing the occurrence of side reactions.

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

[0034] Preferably, in step (3), before the initiator and the carboxylic acid compound containing an unsaturated double bond are mixed, a mixed solution is first formed in a solvent.

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

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

[0037] As an example, in step (3), the reaction also includes post-treatment, such as placing the reaction mixture in an alcohol solvent such as ethanol, precipitating and separating, and then drying, wherein the drying temperature can be 40-80°C, such as 50°C, 60°C, 70°C, etc.

[0038] As an example, in the present application, the mixing of step (1), the mixing, reaction, pH adjustment and continued reaction of step (2), and the mixing and reaction of step (3) are each independently carried out at 10-45°C, for example, 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 comprises the following steps:

[0040] (1) dissolving sodium alginate in a solvent, and then mixing with an activator to obtain a sodium alginate solution;

[0041] (2) mixing the sodium alginate solution and the thiol reagent solution, reacting for 2-3 hours under light-proof conditions, adjusting the pH to 7-8, and continuing the reaction for 1-2 hours to obtain a thiolated sodium alginate solution;

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

[0043] In a third aspect, the present application provides an adsorbent, which includes 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) The present 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) The present application introduces a functional group carboxyl into sodium alginate through a thiol-ene click reaction, and 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 the present 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 the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0051] Figure 1 This is a flow chart of the preparation of modified sodium alginate obtained in Example 1;

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

[0053] Figure 3 This is a scanning electron micrograph of the sodium alginate modified by the thiol-ene click reaction obtained in Example 1;

[0054] Figure 4 for Figure 3 A partial enlarged view of

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

[0056] Figure 6 for Figure 5 A partial enlarged view of

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

[0058] Figure 8 The adsorption effect of ciprofloxacin on the thiolated sodium alginate and the sodium alginate modified by the thiol-ene click reaction obtained in Example 1 under different pH conditions;

[0059] Fig. 9 The adsorption effect of the sodium alginate modified by the thiol-ene click reaction obtained in Example 1 on methylene blue and ciprofloxacin after five cycles of adsorption-desorption. DETAILED DESCRIPTION

[0060] The following embodiments of the technical solution of the present application will be described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0062] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0063] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0064] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "2-10" means that all real numbers between "2-10" are listed in this document, and "2-10" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0065] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0066] Example 1

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

[0068] (1) Sodium alginate is dissolved in 60 mL of pure water, and then N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride are added, the molar ratio of sodium alginate, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1:1, and activated at room temperature for 1 hour; then cysteine ​​is added, the molar ratio of sodium alginate to cysteine ​​is 1:1.5, and the reaction is carried out under light-proof conditions for 2 hours, the pH is adjusted to 7, and the reaction is continued for 1 hour.

[0069] (2) 5 mL of 2,2-dihydroxymethylpropionic acid and acrylic acid dissolved in pure water were added to the thiolated sodium alginate solution obtained in step (1), and the molar ratio of cysteine, acrylic acid and 2,2-dihydroxymethylpropionic acid was 1:1:0.3. The mixture solution was irradiated with an ultraviolet lamp with a wavelength of 365 nm under nitrogen and stirred for 3 h.

[0070] (3) placing the mixture solution obtained in step (2) in an ethanol solution, separating by precipitation, and drying at 60° C. to obtain sodium alginate modified by thiol-ene click reaction, i.e., the modified sodium alginate.

[0071] Example 2

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

[0073] (1) Sodium alginate is dissolved in 60 mL of pure water, and then N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride are added, the molar ratio of sodium alginate, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1:1, and activated at room temperature for 1 hour; then cysteine ​​is added, the molar ratio of sodium alginate and cysteine ​​is 1:1, and the reaction is carried out under light-proof conditions for 2 hours, the pH is adjusted to 7, and the reaction is continued for 1 hour.

[0074] (2) 5 mL of 2,2-dihydroxymethylpropionic acid and acrylic acid dissolved in pure water were added to the thiolated sodium alginate solution obtained in step (1), and the molar ratio of cysteine, acrylic acid and 2,2-dihydroxymethylpropionic acid was 1:1:0.3. The mixture solution was irradiated with an ultraviolet lamp with a wavelength of 365 nm under nitrogen and stirred for 3 h.

[0075] (3) placing the mixture solution obtained in step (2) in an ethanol solution, separating by precipitation, and drying at 60° C. to obtain sodium alginate modified by thiol-ene click reaction, i.e., the modified sodium alginate.

[0076] Example 3

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

[0078] (1) Sodium alginate is dissolved in 60 mL of pure water, and then N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride are added, the molar ratio of sodium alginate, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1:1, and activated at room temperature for 1 hour; then cysteine ​​is added, the molar ratio of sodium alginate to cysteine ​​is 1:2, and the reaction is carried out under light-proof conditions for 2 hours, the pH is adjusted to 7, and the reaction is continued for 1 hour.

[0079] (2) 5 mL of 2,2-dihydroxymethylpropionic acid and acrylic acid dissolved in pure water were added to the thiolated sodium alginate solution obtained in step (1), and the molar ratio of cysteine, acrylic acid and 2,2-dihydroxymethylpropionic acid was 1:1:0.3. The mixture solution was irradiated with an ultraviolet lamp with a wavelength of 365 nm under nitrogen and stirred for 3 h.

[0080] (3) placing the mixture solution obtained in step (2) in an ethanol solution, separating by precipitation, and drying at 60° C. to obtain sodium alginate modified by thiol-ene click reaction, i.e., the modified sodium alginate.

[0081] Example 4

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

[0083] (1) Sodium alginate is dissolved in 60 mL of pure water, and then N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride are added, the molar ratio of sodium alginate, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1:1, and activated at room temperature for 1 hour; then cysteine ​​is added, the molar ratio of sodium alginate to cysteine ​​is 1:0.5, and the reaction is carried out under light-proof conditions for 2 hours, the pH is adjusted to 7, and the reaction is continued for 1 hour.

[0084] (2) 5 mL of 2,2-dihydroxymethylpropionic acid and acrylic acid dissolved in pure water were added to the thiolated sodium alginate solution obtained in step (1), and the molar ratio of cysteine, acrylic acid and 2,2-dihydroxymethylpropionic acid was 1:1:0.3. The mixture solution was irradiated with an ultraviolet lamp with a wavelength of 365 nm under nitrogen and stirred for 3 h.

[0085] (3) placing the mixture solution obtained in step (2) in an ethanol solution, separating by precipitation, and drying at 60° C. to obtain sodium alginate modified by thiol-ene click reaction, i.e., the modified sodium alginate.

[0086] Example 5

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

[0088] (1) Sodium alginate is dissolved in 60 mL of pure water, and then N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride are added, the molar ratio of sodium alginate, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1:1, and activated at room temperature for 1 hour; then cysteine ​​is added, the molar ratio of sodium alginate and cysteine ​​is 1:1, and the reaction is carried out under light-proof conditions for 2 hours, the pH is adjusted to 7, and the reaction is continued for 1 hour.

[0089] (2) 5 mL of 2,2-dihydroxymethylpropionic acid and acrylic acid dissolved in pure water were added to the thiolated sodium alginate solution obtained in step (1), and the molar ratio of cysteine, acrylic acid and 2,2-dihydroxymethylpropionic acid was 1:2:0.5. The mixture solution was irradiated with an ultraviolet lamp with a wavelength of 365 nm under nitrogen and stirred for 3 h.

[0090] (3) placing the mixture solution obtained in step (2) in an ethanol solution, separating by precipitation, and drying at 60° C. to obtain sodium alginate modified by thiol-ene click reaction, i.e., the modified sodium alginate.

[0091] Embodiment 6-7

[0092] The difference between this embodiment and embodiment 1 is that the molar ratio of cysteine ​​to sodium alginate is different, which are 0.3:1 (embodiment 6) and 2.5:1 (embodiment 7), respectively. The rest is the same as embodiment 1.

[0093] Comparative Example 1

[0094] This comparative example provides a modified sodium alginate, which is obtained by the following preparation method, and the preparation method comprises the following steps:

[0095] (1) Sodium alginate was dissolved in 60 mL of pure water, and then N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were added, and the molar ratio of sodium alginate, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride was 1:1:1, and activated at room temperature for 1 hour; then cysteine ​​was added, and the molar ratio of sodium alginate and cysteine ​​was 1:1, and the reaction was carried out under light-proof conditions for 2 hours, and the pH was adjusted to 7, and the reaction was continued for 1 hour.

[0096] (2) placing the mixture solution obtained in step (1) in an ethanol solution, separating the precipitate, and drying at 60° C. to obtain thiolated sodium alginate.

[0097] Performance Testing

[0098] (1) Structural characterization

[0099] Taking Example 1 and Comparative Example 1 as examples, the structures of sodium alginate, cysteine, and sodium alginate modified by thiol-ene click reaction were characterized. Figure 2 As shown in the infrared spectrum of sodium alginate modified by thiol-ene click reaction, the peak at 2591 cm -1 The characteristic peak of thiol disappears at 1024cm -1 The characteristic peak of CSC appeared at 2591 cm -1 The peak at the bottom is the characteristic peak of thiol (-SH), indicating that sodium alginate was successfully grafted with cysteine.

[0100] (2) Morphology test

[0101] Taking Example 1 and Comparative Example 1 as examples, the morphologies of the samples were observed and compared using a scanning electron microscope. Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, compared with the scanning electron microscope image of thiolated sodium alginate (Comparative Example 1) ( Figure 5 and Figure 6 ), the sodium alginate modified by the thiol-ene click reaction obtained in the present application (Example 1) is as follows Figure 3 and Figure 4 As shown, many evenly distributed slender needle-like lines appeared on the surface, and the morphology of the adsorbent changed; the surface of the thiolated sodium alginate was rough and had no obvious lines, which was significantly different from the surface morphology of the sodium alginate modified by the thiol-ene click reaction.

[0102] (3) Adsorption performance

[0103] 1) Sodium alginate modified by thiol-ene click reaction was used as adsorbent to investigate the adsorption capacity of methylene blue under different pH conditions. The initial concentration of methylene blue was 100 mg·L -1 , taking Example 1 as an example, the results are as follows Figure 7 As shown in Figure 2, the adsorption capacity of the adsorbent remains at 450 mg g in a wide pH range. -1 This is because the electrostatic interaction between sodium alginate and methylene blue was modified by the thiol-ene click reaction.

[0104] 2) Sodium alginate modified by thiol-ene click reaction was used as an adsorbent to investigate its adsorption capacity for ciprofloxacin under different pH conditions. The initial concentration of ciprofloxacin was 50 mg·L -1 , taking Example 1 as an example, the results are as follows Figure 8As shown in the figure, under acidic conditions, there are a large number of hydrogen ions in the solution, which compete with cationic ciprofloxacin for adsorption, resulting in no significant increase in the adsorption amount. When the pH increases, the hydrogen ions in the solution decrease, and the cationic ciprofloxacin and the sodium alginate adsorbent modified by the thiol-ene click reaction produce electrostatic effects. At this time, the adsorption effect is the best, and the adsorption capacity reaches 211.1 mg·g -1 ; As the pH continues to increase, ciprofloxacin gradually exists in the aqueous solution in the form of anions. There is electrostatic repulsion between the adsorbent and the pollutant, so the adsorption amount of ciprofloxacin by the adsorbent decreases.

[0105] 3) The sodium alginate modified by thiol-ene click reaction was cyclically adsorbed and desorbed to explore the adsorption of methylene blue and ciprofloxacin after multiple uses. Taking Example 1 as an example, the results are as follows: Fig. 9 As shown, the adsorption of methylene blue was almost unaffected after multiple uses, and although the adsorption efficiency of ciprofloxacin decreased, it also maintained a relatively high removal rate.

[0106] For further comparison, the test results of the adsorption performance of each embodiment are summarized in Table 1. During the performance test, the reaction temperature was 25°C; the dosage of the adsorbent was 0.2 g·L -1 ; The volume of methylene blue solution is 50 mL, the pH is 10, and the initial concentration is 100 mg·L -1 ; The volume of ciprofloxacin solution is 50 mL, the pH is 4, and the initial concentration is 50 mg·L -1 .

[0107] Table 1

[0108]

[0109] 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, which proves that the modified sodium alginate obtained by the preparation method described in the present application has better adsorption performance.

[0110] Comparing Examples 6-7 with Example 1, it can be seen that the adsorption performance of Examples 6-7 is not as good as that of Example 1, which proves that the molar ratio of the thiol reagent to sodium alginate is in the range of (0.5-2):1, which is more conducive to introducing an appropriate amount of thiol functional groups, thereby improving the adsorption performance of the modified sodium alginate.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A modified sodium alginate, characterized in that: The raw materials for preparing the modified sodium alginate include sodium alginate, an activator, a thiol-forming agent, a carboxylic acid compound containing an unsaturated double bond and an initiator.

2. The modified sodium alginate according to claim 1, characterized in that The molar ratio of the activator to sodium alginate is (0.5-2):1; Preferably, the activator comprises N-hydroxysuccinimide and / or 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride; Preferably, the molar ratio of N-hydroxysuccinimide to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is (0.5-1.5):

1.

3. The modified sodium alginate according to claim 1 or 2, characterized in that: The molar ratio of the thiol-forming agent to sodium alginate is (0.5-2):1; Preferably, the thiolating agent comprises a thiol group and a carboxyl group and / or an amino group; Preferably, the thiolating agent comprises any one of cysteine, thioglycolic acid or mercaptopropionic acid, or a combination of at least two thereof, and cysteine ​​is further preferred.

4. The modified sodium alginate according to any one of claims 1 to 3, characterized in that: The molar ratio of the carboxylic acid compound containing an unsaturated double bond to sodium alginate is (1-2):1; Preferably, the carboxylic acid compound containing an unsaturated double bond includes an acrylic acid compound.

5. The modified sodium alginate according to any one of claims 1 to 4, characterized in that: The molar ratio of the initiator to the carboxylic acid compound containing an unsaturated double bond is (0.1-0.5):1; Preferably, the initiator comprises 2,2-dimethylolpropionic acid.

6. A method for preparing the modified sodium alginate according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: Sodium alginate, an activator, a thiol-forming agent, a carboxylic acid compound containing an unsaturated double bond and an initiator are mixed to carry out a thiol-ene click reaction to obtain the modified sodium alginate.

7. The preparation method according to claim 6, characterized in that: The preparation method comprises the following steps: (1) mixing sodium alginate, an activator and a solvent to obtain a sodium alginate solution; (2) mixing the sodium alginate solution and the thiol reagent, reacting them in a light-proof condition, and adjusting the pH to obtain a thiolated sodium alginate solution; (3) Under an inert atmosphere, an initiator, a carboxylic acid compound containing an unsaturated double bond and a thiolated sodium alginate solution are mixed and reacted to obtain the modified sodium alginate.

8. The preparation method according to claim 7, characterized in that: In step (1), the solvent comprises water; Preferably, the sodium alginate and the solvent are first mixed, and then mixed with the activator; Preferably, in step (2), the thiolating agent is first formed into a thiolating agent solution, and then mixed with the sodium alginate solution; Preferably, in step (2), the reaction time is 2-3 h; Preferably, in step (2), the pH is adjusted to 7-8; Preferably, in step (2), after adjusting the pH, the reaction is continued for 1-2 hours; Preferably, in step (3), before the initiator and the carboxylic acid compound containing an unsaturated double bond are mixed, a mixed solution is first formed in a solvent; Preferably, in step (3), the reaction is carried out under ultraviolet light; Preferably, in step (3), the reaction time is 3-4 h.

9. The preparation method according to any one of claims 6 to 8, characterized in that: The preparation method comprises the following steps: (1) dissolving sodium alginate in a solvent, and then mixing with an activator to obtain a sodium alginate solution; (2) mixing the sodium alginate solution and the thiol reagent solution, reacting for 2-3 hours under light-proof conditions, adjusting the pH to 7-8, and continuing the reaction for 1-2 hours to obtain a thiolated sodium alginate solution; (3) Under an inert atmosphere, a mixed solution of an initiator and a carboxylic acid compound containing an unsaturated double bond and a thiolated sodium alginate solution are mixed, and the mixture is reacted for 3-4 hours under ultraviolet light to obtain the modified sodium alginate.

10. An adsorbent, characterized in that: The adsorbent comprises the modified sodium alginate according to any one of claims 1 to 5, or the modified sodium alginate obtained by the preparation method according to any one of claims 6 to 8; Preferably, the adsorbent is used for water treatment.

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