Chitosan / sodium alginate composite aerogel and preparation method and application thereof
By preparing chitosan/sodium alginate composite aerogels, the synergistic effect of the functional groups of chitosan and sodium alginate was utilized to solve the problems of low perchlorate removal efficiency and secondary pollution in existing technologies, and to achieve rapid and efficient perchlorate adsorption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2024-03-19
- Publication Date
- 2026-06-05
AI Technical Summary
Existing technologies are not very efficient at removing low concentrations of perchlorate from water, and physical adsorbents may introduce secondary pollution or have insufficient mechanical strength.
Chitosan/sodium alginate composite aerogels were prepared by dripping chitosan solution into sodium alginate solution to form gel spheres. Glutaraldehyde was cross-linked and washed with alkali to form a porous structure. The synergistic effect of the functional groups of chitosan and sodium alginate was utilized to efficiently adsorb perchlorate.
It achieves efficient removal of perchlorate from water, with fast adsorption speed, high adsorption capacity, wide applicable pH range, and avoids secondary pollution and mechanical strength issues.
Smart Images
Figure CN118236980B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of environmental remediation, specifically relating to a chitosan / sodium alginate composite aerogel, its preparation method, and its application. Background Technology
[0002] Perchlorate (ClO4) - ClO4 is a novel inorganic pollutant. Due to its high stability, solubility, and strong oxidizing properties, it is widely used as an oxidant in military manufacturing and industrial production. Anthropogenic ClO4 is also generated during the use of aerospace, fireworks, and disinfectants. - Pollution has resulted in low concentrations of perchlorate being virtually ubiquitous in the environment. Studies have shown that ClO4... - Its charge and ionic radius are very similar to those of iodide ions, allowing it to compete with iodide ions for normal thyroid function. In 2017, the World Health Organization (WHO) published its "Guidelines for Drinking-water Quality," which set a limit of 70 μg / L for perchlorate in drinking water. Furthermore, in 2019, the U.S. Environmental Protection Agency (USEPA) proposed a maximum health-based contaminant level target of 56 μg / L for perchlorate in drinking water.
[0003] There are three main pathways for perchlorate removal: physical adsorption, chemical reduction, and microbial reduction. Chemical catalysis requires harsh reaction conditions, such as highly acidic environments and anaerobic conditions. Furthermore, there is a risk of catalyst metal shedding. Perchlorate-reducing bacteria can use perchlorate as an electron acceptor for reduction. However, bioremediation processes are relatively slow, and microbial metabolites may cause secondary pollution. Therefore, these technologies are limited in practical water treatment applications. Compared to these technologies, physical adsorption is considered a highly efficient and economical method because it is simple, has high removal efficiency, and uses inexpensive adsorbents. Aerogel materials, with their high porosity and high adsorption capacity, are widely used to adsorb and purify anions, heavy metals, and pesticides in water.
[0004] Chitosan (CTS) is a polymer of 2-amino-2-deoxy-D-glucose monomers linked by β-(1-4) glycosides. It is the only naturally occurring cationic polysaccharide in nature, containing a large number of hydroxyl (-OH) and amino (-NH2) groups, which are typical Lewis basic groups. It has wide applications in water treatment, biomedical materials, and food engineering. However, the strong hydrogen bonding between the hydroxyl and amino groups in the chitosan molecule makes it difficult to dissolve in water and common solvents, although it is soluble in acidic solutions.
[0005] Chinese patent application CN111203192A discloses a method for preparing modified chitosan microsphere adsorbents for adsorbing perchlorate and its application, including the following steps: weighing chitosan and dissolving it in acetic acid solution, stirring for a certain time, and then refrigerating and allowing it to stand to remove air bubbles; adding the chitosan solution dropwise into NaOH solution to induce a gel reaction, obtaining chitosan gel microspheres; washing until neutral, and then carrying out a cross-linking reaction according to a certain ratio of the molar mass of chitosan monomers to the molar mass of cross-linking agent ECH in the microspheres; adding the chitosan microspheres after the cross-linking reaction is completed to a ZrOCl2·8H2O aqueous solution and reacting for a certain time, and then drying the resulting zirconium-containing microspheres to obtain the chitosan microsphere adsorbent. However, the above patent still has room for further improvement in the removal efficiency of perchlorate. Summary of the Invention
[0006] This invention provides a method for preparing chitosan / sodium alginate composite aerogel. The composite aerogel prepared by this method can purify low concentrations of perchlorate in water with high adsorption rate.
[0007] This invention provides a method for preparing chitosan / sodium alginate composite aerogel, comprising:
[0008] (1) Chitosan is added to glacial acetic acid solution to form chitosan solution, sodium alginate is added to NaOH solution to form sodium alginate solution, and chitosan solution is added dropwise to sodium alginate solution while stirring to form gel balls.
[0009] (2) The gel beads were added to glutaraldehyde solution to obtain gel beads;
[0010] (3) The gel beads were washed with alkali to obtain a chitosan / sodium alginate composite aerogel with pores.
[0011] This invention involves dripping a chitosan solution into a sodium alginate solution, causing the chitosan to partially encapsulate the sodium alginate to form gel spheres. Glutaraldehyde is then used to cross-link the interior of these gel spheres, reinforcing them to form gel beads. Alkali washing is then used to remove some of the sodium alginate from the gel beads, creating multiple pores within the beads. These pores enable efficient adsorption of perchlorate ions, and the synergistic effect of the functional groups of chitosan and sodium alginate is utilized to efficiently remove perchlorate.
[0012] Preferably, the concentration of the chitosan solution is 2%-5% by mass fraction, and the concentration of the sodium alginate solution is 1%-4%. This invention controls the concentration of the chitosan solution to ensure sufficient chitosan can be incorporated into the sodium alginate solution. By controlling the concentration of the sodium alginate solution, this invention forms gel spheres containing appropriate amounts of chitosan and sodium alginate. This avoids insufficient sodium alginate concentration affecting the amount of sodium alginate in the gel spheres, thus hindering perchlorate removal. It also avoids excessively high sodium alginate solution concentration, which would prevent sodium alginate from dissolving in the chitosan solution, thus failing to obtain the desired sodium alginate content in the gel spheres and affecting perchlorate removal.
[0013] More preferably, the concentration of the sodium alginate solution is 1%-3% by mass fraction. At this concentration of sodium alginate solution, the removal efficiency of the chitosan / sodium alginate composite aerogel for perchlorate shows a gradient increasing trend with increasing sodium alginate solution concentration, reaching the highest removal rate for perchlorate when the sodium alginate solution concentration is 3%.
[0014] Preferably, in step (3), the alkaline washing solution is a NaOH solution with a concentration of 0.01–0.05 M, and the alkaline washing time is 4–5 h. This invention controls the concentration of the NaOH solution and the alkaline washing time to remove an appropriate amount of sodium alginate, thereby forming a rough surface and appropriately sized pores to adsorb perchlorate. This avoids reducing the adsorption effect due to insufficient pores, and also avoids excessive loss of sodium alginate due to excessively high concentration or excessively long alkaline washing time, which would reduce the adsorption effect and decrease the mechanical properties of the composite gel, leading to collapse and failure of the composite gel during adsorption.
[0015] This invention provides a composite aerogel with suitable porosity, strong hydrophilicity, low density, and large adsorption capacity by controlling the parameters of alkaline washing and the content of sodium alginate. The addition of sodium alginate increases the number of hydroxyl groups, enhancing hydrophilicity. After freeze-drying, the resulting aerogel has a low density.
[0016] Preferably, in step (1), chitosan is added to glacial acetic acid solution to form the chitosan solution, and sodium alginate is added to NaOH solution to form the sodium alginate solution;
[0017] The mass ratio of chitosan to sodium alginate is 1:0.5 to 2.0.
[0018] This invention provides an appropriate amount of sodium alginate, which enables the composite aerogel to have an appropriate amount of carboxyl groups to remove perchlorate. It also forms microporous channels, allowing perchlorate to combine with more adsorption sites such as amino, carboxyl, and hydroxyl groups.
[0019] More preferably, the chitosan has a degree of deacetylation ≥95% and a viscosity of 100-200 mPa·s.
[0020] Preferably, in step (2), the mass fraction of glutaraldehyde is 25%.
[0021] Preferably, the chitosan has a degree of deacetylation ≥95%, a viscosity of 100-200 mPa·s, and a mass fraction of 4.0-5.0% in the chitosan solution.
[0022] Preferably, chitosan is dissolved in glacial acetic acid solution using alternating stirring and sonication to form a chitosan solution. The stirring and sonication are alternated every 30-40 minutes for a duration of 4-6 hours. The stirring speed is 300-500 r / min, and the solution is allowed to stand for 12-15 hours after the alternating stirring and sonication. By controlling the process parameters of stirring, sonication, and standing time, air bubbles in the chitosan solution are avoided.
[0023] Preferably, the solution for dissolving sodium alginate is a 2.0–4.0% NaOH solution, wherein the mass fraction of sodium alginate in the sodium alginate solution is 2.0–4.0%. This invention provides a NaOH solution of suitable concentration and an appropriate amount of sodium alginate, enabling sodium alginate to dissolve completely in the NaOH solution.
[0024] Preferably, in step (1), the stirring speed is 500-600 r / min. By controlling the stirring speed, chitosan can be uniformly dispersed in the sodium alginate solution to form gel spheres, avoiding adhesion and failure to form gel spheres, which would affect the adsorption performance of perchlorate.
[0025] More preferably, a 10ml syringe with a 0.5*25mm needle is used to drop mixture A into the sodium alginate solution, and the mixture is added while stirring at a stirring speed of 300r / min.
[0026] Preferably, after alkaline washing, the product is washed, frozen, and dried to obtain a porous chitosan / sodium alginate composite aerogel. Washing is performed by repeatedly washing with deionized water 10 times. Freezing is carried out in a -4°C freezer for 4 hours, and drying is performed using a freeze dryer with a cold trap temperature of -45°C and a vacuum degree of 15 Pa for 12 hours until completely dried.
[0027] On the other hand, the present invention also provides a chitosan / sodium alginate composite aerogel, which is prepared by the aforementioned method for preparing chitosan / sodium alginate composite aerogel, wherein the specific surface area of the chitosan / sodium alginate composite aerogel is 228.2–256.3 m². 2 / g, with pore size ranging from 1 to 5 μm.
[0028] On the other hand, the present invention also provides the application of the chitosan / sodium alginate composite aerogel in the removal of perchlorate, wherein the chitosan / sodium alginate composite aerogel is added to a perchlorate solution with a concentration of 10.0 to 500.0 mg / L, and the pH value of the perchlorate solution is 3.0 to 11.0.
[0029] The chitosan / sodium alginate composite aerogel provided by this invention can remove perchlorate from perchlorate solutions with a wide range of pH values and concentrations.
[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0031] This invention utilizes the high-density adsorption sites of amino and hydroxyl groups provided by chitosan and carboxyl groups provided by sodium alginate to achieve a maximum adsorption capacity of 70.15 mg / g for perchlorate. Furthermore, the alkaline washing of the sodium alginate creates a rough surface and pores, avoiding the secondary pollution and reduced perchlorate adsorption capacity caused by introducing new substances through pore-forming agents as in existing technologies. Simultaneously, the addition of sodium alginate and the alkaline washing process increase hydrophilic functional groups, thereby enhancing the hydrophilicity of the composite aerogel. Combined with the higher surface roughness, this allows for more effective capture of perchlorate anions.
[0032] The chitosan / sodium alginate composite aerogel provided by this invention adsorbs sodium perchlorate rapidly, reaching over 95% ClO4 concentration within 10 minutes at an initial concentration of 10 mg / L. - Removal rate, achieving rapid and efficient removal of ClO4 - The purpose is to [achieve this goal]. The rough surface and abundant functional groups of aerogel provide a large number of adsorption sites, and the hydrogen bonds and electrostatic adsorption between perchlorate and functional groups further enhance the adsorption rate. Attached Figure Description
[0033] Figure 1 This is a schematic diagram illustrating the preparation of CTS, CTS / SA, and CTS / SA-m aerogels obtained in Example 1, Comparative Example 1, and Comparative Example 2.
[0034] Figure 2 The images show the scanning electron microscope (SEM) images of the CTS, CTS / SA, and CTS / SA-m adsorbents prepared in Example 1, Comparative Example 1, and Comparative Example 2.
[0035] Figure 3 The contact angle diagrams are shown for the CTS, CTS / SA, and CTS / SA-m aerogels prepared in Example 1, Comparative Example 1, and Comparative Example 2.
[0036] Figure 4Infrared spectra of CTS, CTS / SA, and CTS / SA-m aerogels prepared in Example 1, Comparative Example 1, and Comparative Example 2;
[0037] Figure 5 Zeta potential diagrams corresponding to CTS / SA-m aerogels prepared at different alkaline concentrations as provided in Example 6;
[0038] Figure 6 The different sodium alginate ratios provided in Application Example 1 affect ClO4 - The effect of adsorption removal rate is shown in the figure.
[0039] Figure 7 The different pH values of ClO4 provided in Application Example 2 - Adsorption and removal effect diagram;
[0040] Figure 8 To apply the CTS / SA-m provided in Example 3 to different initial concentrations of ClO4 - Variations in adsorption capacity and fitting of Langmuir, Freundlich, and MLA models;
[0041] Figure 9 To apply the CTS / SA-m to ClO4 at different contact times in Example 4 - The influence of adsorption capacity and the fitting diagrams of the kinetic model and the intraparticle diffusion model; among which, Figure 9 (a) CTS / SA-m at different contact times for ClO4 in Application Example 4 - Effect of adsorption capacity and fitting plots of pseudo-first-order and pseudo-second-order kinetic models. Figure 9 (b) CTS / SA-m at different contact times for ClO4 in Application Example 4 - Adsorption capacity intraparticle diffusion model fitting diagram. Detailed Implementation
[0042] The present invention will be further analyzed below with reference to specific embodiments.
[0043] Example 1
[0044] This embodiment provides a method for preparing CTS / SA-m composite aerogel, such as... Figure 1 As shown in c, it includes:
[0045] Step (1): At room temperature of 25℃, add 4g of chitosan (CTS) (deacetylated >95%) to 196ml of glacial acetic acid aqueous solution (8%, w / w), and sonicate until completely dissolved to obtain a preliminary mixture; then let the preliminary mixture stand for 12h to remove air bubbles to obtain 2% CTS mixture A.
[0046] Step (2): At room temperature (25℃), 6.0 g of sodium alginate (SA) was added to 194 ml of 2.0 M NaOH solution to obtain a sodium alginate solution (3%). Then, using a syringe, the CTS mixture A prepared in step (1) was added dropwise to the 3% sodium alginate solution at a constant rotation speed of 500 r / min to form CTS / SA gel spheres. The spheres were allowed to gel in NaOH solution for 6 h, and then thoroughly washed with deionized water until the pH of the gel spheres in the water was neutral.
[0047] Step (3): Immerse the gel microspheres obtained in step (2) in a glutaraldehyde solution (20%, w / w) and crosslink them in a constant temperature shaker at 50°C for 12 hours. Then, rinse the CTS / SA gel microspheres repeatedly with deionized water to remove crosslinking agent residues.
[0048] Step (4): The gel beads obtained in step (3) were soaked in 0.01M NaOH solution for 4 hours to remove some of the SA. Then, the gel beads were rinsed with deionized water until the pH was neutral to obtain CTS / SA-M gel beads. Finally, the gel beads were freeze-dried for 48 hours to obtain CTS / SA-m aerogel.
[0049] Comparative Example 1
[0050] This comparative example provides a method for preparing a CTS adsorbent, such as... Figure 1 As shown in a, it includes:
[0051] Step (1): At room temperature of 25℃, add 4g of chitosan (deacetylated >95%) to 196ml of glacial acetic acid aqueous solution (8%, w / w), and sonicate until completely dissolved to obtain a preliminary mixture; then let the preliminary mixture stand for 12h to remove air bubbles to obtain 2% CTS mixture A;
[0052] Step (2): Using a syringe, the CTS mixture A prepared in step (1) is added dropwise to the sodium alginate solution, and CTS / SA gel spheres are formed at a constant rotation speed of 500 r / min. The spheres are allowed to gel in NaOH solution for 6 h, and then the gel spheres are thoroughly washed with deionized water until the pH of the gel spheres in the water is neutral.
[0053] Steps (3) and (4) are performed according to steps (3, 4) of Example 1 to obtain the CTS adsorbent.
[0054] Comparative Example 2
[0055] This comparative example provides a method for preparing a CTS adsorbent, such as... Figure 1 As shown in b, it includes:
[0056] Step (1): Obtain CTS / SA gel microspheres according to steps (1, 2, 3) of Example 1;
[0057] Step (2): The gel microspheres obtained in step (1) were freeze-dried for 48 hours using a freeze dryer to obtain CTS / SA aerogel.
[0058] Example 3
[0059] Unlike Example 1, 2g of sodium alginate was dissolved in 198ml of 2.0M NaOH solution, and the sodium alginate solution ratio was 1.0wt% SA.
[0060] Example 4
[0061] Unlike Example 1, 4g of sodium alginate was dissolved in 196ml of 2.0M NaOH solution, and the sodium alginate solution was prepared with a ratio of 2.0wt% SA.
[0062] Example 5
[0063] Unlike Example 1, 8g of sodium alginate was dissolved in 192ml of 2.0M NaOH solution, and the sodium alginate solution ratio was 4.0wt% SA.
[0064] Example 6
[0065] Unlike Example 1, the concentrations of the NaOH solutions were 0.05, 0.1, 0.2, and 0.5 M, respectively, and the alkaline washing time was 8 hours.
[0066] Performance Analysis:
[0067] like Figure 2 Figures (a), (b), and (c) show scanning electron microscope (SEM) images of the CTS, CTS / SA, and CTS / SA-m adsorbents prepared in Example 1. It can be seen that the CTS / SA-m prepared in Example 1 has a relatively rough surface, exhibiting a loofah-like structure with numerous inwardly recessed microporous channels, and a specific surface area of 228.20 m². 2 / g, with pore sizes ranging from 1 to 5 μm.
[0068] like Figure 3 The image shows the contact angle diagrams of the adsorbents prepared in Example 1, Comparative Example 1, and Comparative Example 2. Figure 3 It is evident that the three adsorbents exhibit different hydrophilicities. The contact angles of CTS, CTS / SA, and CTS / SA-m are 46.03°, 26.13°, and 14.04°, respectively, with CTS / SA-m showing the strongest hydrophilicity. This indicates that the addition of sodium alginate to the composite aerogel and the alkaline washing process increase the hydrophilic functional groups, thereby enhancing the hydrophilicity of the adsorbent.
[0069] like Figure 4 The image shows the infrared spectra of the adsorbents prepared in Example 1, Comparative Example 1, and Comparative Example 2. Figure 4 As can be seen, the spectrum of the CTS / SA-m adsorbent prepared in Example 1 shows characteristic peaks of -OH stretching, -COO- stretching, -CO-NH2 stretching and -OH bending, indicating that the functional groups (-OH, -COO-) increased during the preparation of the adsorbent.
[0070] like Figure 5 The figure shows the Zeta potential diagrams of the CTS / SA-m adsorbents prepared with different alkali washing concentrations as provided in Example 6. From... Figure 5 As can be seen, the Zeta potential of the CTS / SA-m adsorbent prepared in Example 6 decreases with the increase of NaOH concentration during alkaline washing. A negative Zeta potential is not conducive to the adsorption of perchlorate anions on the surface. Therefore, the NaOH concentration during alkaline washing needs to be controlled at 0.01-0.05M.
[0071] Application Example 1
[0072] Configure ClO4 - The solution concentration was 10 mg / L, and the pH was adjusted to 5. 0.2 g of the CTS / SA-m aerogel material prepared in Examples 1-5 was weighed and placed in a 250 ml ground-glass stoppered conical flask. ClO4 was poured into the conical flask. - 100 ml of solution; shake at 25°C and 150 rpm for 1.5 h; repeat the above steps three times.
[0073] like Figure 6 As shown, with the increase of the sodium alginate solution ratio, ClO4 - The removal rate increased significantly; when the sodium alginate solution was prepared at a ratio of 3.0 wt% SA and 4.0 wt% SA, the removal rate of 10 mg / L ClO4 was significantly increased. - The removal rate has little impact. Appropriate sodium alginate can improve the adsorption effect of aerogel, and the pore size produced during alkaline washing is moderate, which is conducive to adsorption. When the sodium alginate content is too high, the pores of the aerogel after alkaline washing are too large, which leads to a decrease in the mechanical strength of the material and affects adsorption.
[0074] Application Example 2
[0075] The effect of different pH values on adsorption experiments of a single system was investigated, including the following steps:
[0076] Step (1): Prepare ClO4 - The solution concentration was 10 mg / L, and the pH was adjusted to 1, 3, 5, 7, 9, and 11 using 1M NaOH and 1M HCl, respectively.
[0077] Step (2): Weigh 0.2g of the alkaline-washed CTS / SA-m material containing 3.0wt% SA as determined in Example 2, put it into a 250ml ground glass conical flask, and set up two parallel samples under different pH conditions;
[0078] Step (3): Add ClO4 to step (2) - Place 100 ml of solution in a shaker and shake for 1.5 hours at a speed of 150 r / min.
[0079] like Figure 7 As shown, pH value has no significant effect on perchlorate removal within the range of 3.0-11.0, and the perchlorate removal rate can reach 87.96%-96.47%. This indicates that the material has a wide pH application range and can be used for removing ClO4. - Highly efficient adsorbent.
[0080] Application Example 3
[0081] Prepare 10, 20, 50, 100, 200, 300, and 500 mg / L LlO4- solutions respectively, and adjust the pH to 5 with 1M NaOH and 1M HCl.
[0082] Weigh 0.2g of each of the (CTS / SA-m) materials prepared in Example 1 and place them in a ground glass conical flask. Set up two parallel samples for the same adsorption time (two parallel samples plus the original sample make three samples; the final adsorption capacity data is the average value, and the corresponding error bars are also shown in the picture). Place the sample in a shaker and shake for 1.5h at a speed of 150r / min.
[0083] To further describe (CTS / SA-m) for ClO4 - The adsorption behavior was investigated by nonlinearly fitting the isotherm data using the Langmuir isotherm model, the Freundlich isotherm model, and the Multilayer (≥3) adsorption (MLA) isotherm model. The equations for each model are as follows:
[0084] Langmuir isotherm model:
[0085]
[0086] Freundlich isotherm model:
[0087]
[0088] Multilayer (≥3) adsorption (MLA) isotherm model:
[0089]
[0090] Where C e (mg·L -1 ) and q e (mg·L -1 ) represent ClO4 - The equilibrium concentration and adsorption capacity. Q (mg·g) -1 K represents the maximum adsorption capacity of the adsorbent. L K F denoted by Langmuir constant and Freundlich constant, respectively; D (mg / g) is the functional group density; n* is the number of perchlorate molecules adsorbed at each active site (functional group); C1 and C2 are the half-saturation concentrations of the first layer and the 1+N2 layer, respectively.
[0091] Depend on Figure 8 It can be seen that the correlation coefficient R corresponding to the Multilayer (≥3) adsorption (MLA) isotherm model is... 2 The maximum value indicates that it is best suited to describe the adsorption process of perchlorate on CTS / SA-m, suggesting that the adsorption of perchlorate on CTS / SA-m is multilayer (≥3) adsorption.
[0092] Application Example 4
[0093] Preparation of ClO4 - Concentrations of 10, 50, and 100 mg / L were used, and the pH was adjusted to 5 with 1M NaOH and HCl. 0.2 g of each of the (CTS / SA-m) material prepared in Example 1 was weighed and placed in ground-glass conical flasks. Two parallel samples were prepared for the same adsorption time. The prepared ClO4... - Pour 100 ml of the solution into an Erlenmeyer flask, place it in a shaker, and shake for 0, 2, 5, 10, 20, 30, 40, 50, 60, 70, 80 and 90 min respectively, at a speed of 150 r / min.
[0094] To further understand the adsorption process and mechanism, the kinetic data were fitted using a pseudo-first-order kinetic model, a pseudo-second-order kinetic model, and an intraparticle diffusion model (Weber-Morris model):
[0095] Quasi-first-order dynamic model:
[0096]
[0097] Quasi-second-order dynamic model:
[0098]
[0099] Intraparticle diffusion model (Weber-Morris model):
[0100] q t =k d t 0.5 +C
[0101] Where, q t (mg·g -1 ) and q e (mg·g -1 ) represent the adsorption amounts of the target pollutant at time t and at equilibrium, respectively. k1(min) -1 ) and k2(g·mg -1 min -1 ) are the pseudo-first-order and pseudo-second-order kinetic adsorption rate constants, respectively. k d (mg·g -1 min -1 / 2 ) represents the diffusion rate constant within the particle.
[0102] Depend on Figure 9 It can be seen that the fitting curves of the quasi-first-order and quasi-second-order dynamic models are as follows: Figure 9 As shown in (a), the correlation coefficient (R) of the quasi-second-order dynamics model 2 =0.976) is higher than the correlation coefficient (R²) of the pseudo-first-order dynamic model. 2 =0.894). Therefore, the pseudo-second-order kinetic model can better describe the effect of CTS / SA-m on ClO4. - The adsorption process. For example... Figure 9 As shown in (b), the fitted graph is divided into three straight lines, which means that ClO4 - The adsorption of ClO4 involves multiple steps, and intraparticle diffusion is not the only rate-limiting step. Furthermore, different initial concentrations of ClO4... - The intraparticle diffusion rate constants of the three straight lines of adsorption, in descending order, are k 1d >k 2d >k 3d The largest value of k 1d Corresponding to the first stage of adsorption, in this stage ClO4 - The fastest adsorption rate occurs during the diffusion process to the adsorbent surface; the second stage is internal diffusion, where ClO4... - Gradually occupying the internal adsorption sites of the adsorbent; and in the final stage k 3d The minimum value indicates that the adsorption rate gradually decreases, slowly reaching adsorption equilibrium. These conclusions demonstrate that CTS / SA-m has a low adsorption rate for ClO4. - Adsorption is a relatively complex process that is completed in multiple steps.
[0103] The above embodiments are not intended to limit the present invention, and the present invention is not limited to the above embodiments. Any embodiment that meets the requirements of the present invention is within the protection scope of the present invention.
Claims
1. A method for preparing a chitosan / sodium alginate composite aerogel, characterized in that, include: (1) Add the chitosan solution to the sodium alginate solution while stirring to form gel beads; (2) The gel beads were added to glutaraldehyde solution to obtain gel beads; (3) The gel beads are washed with alkali to obtain a chitosan / sodium alginate composite aerogel with a rough surface and pores; In step (3), the gel beads are washed with NaOH solution, the concentration of which is 0.01 M to 0.05 M, and the washing time is 4 h to 5 h. After alkali washing in step (3), the gel microspheres are rinsed with deionized water until the pH is neutral, and the gel microsphere samples are freeze-dried for 48 h using a freeze dryer to obtain chitosan / sodium alginate composite aerogel. The concentration of the chitosan solution is 2%-5% by mass fraction, and the concentration of the sodium alginate solution is 1%-4%. In step (1), chitosan is added to glacial acetic acid solution to form the chitosan solution, and sodium alginate is added to NaOH solution to form the sodium alginate solution; The mass ratio of chitosan to sodium alginate is 1:0.5~2.
0.
2. The method for preparing chitosan / sodium alginate composite aerogel according to claim 1, characterized in that, The concentration of the sodium alginate solution is 1%-3% by mass fraction.
3. The method for preparing chitosan / sodium alginate composite aerogel according to claim 1, characterized in that, The chitosan has a degree of deacetylation ≥95% and a viscosity of 100-200 mPa·s.
4. The method for preparing chitosan / sodium alginate composite aerogel according to claim 1, characterized in that, Chitosan was dissolved in glacial acetic acid solution by alternating stirring and sonication to form a chitosan solution. The stirring and sonication were alternated every 30 to 40 minutes for a duration of 4 to 6 hours. The stirring speed was 300 to 500 r / min. After alternating stirring and sonication, the solution was allowed to stand for 12 to 15 hours.
5. The method for preparing chitosan / sodium alginate composite aerogel according to claim 1, characterized in that, In step (1), the stirring speed is 500~600 r / min.
6. A chitosan / sodium alginate composite aerogel, characterized in that, The chitosan / sodium alginate composite aerogel was prepared by the method described in any one of claims 1-5, and the specific surface area of the chitosan / sodium alginate composite aerogel was 228.2~256.3 m². 2 / g, with pore size of 1~5µm.
7. An application of the chitosan / sodium alginate composite aerogel according to claim 6 in the removal of perchlorate, characterized in that, The chitosan / sodium alginate composite aerogel was added to a perchlorate solution with a concentration of 10.0~500.0 mg / L, wherein the pH value of the perchlorate solution was 3.0~11.0.