Application of a pectin-CMC composite aerogel with high efficiency in adsorbing rare earth ions and its preparation method

Abstract

The present invention discloses a pectin-carboxymethyl cellulose composite aerogel (PCA) with efficient adsorption performance for rare earth ions, a preparation method and its application in adsorption separation, belonging to the field of material preparation and separation technology. The adsorbent uses pectin (PC) and carboxymethyl cellulose (CMC) as biomass adsorption materials, and adopts the sol-gel method to synthesize the aerogel to improve its adsorption performance. Through cross-linking, a large number of active adsorption sites are formed, thereby increasing its adsorption capacity for rare earth ions. Its maximum adsorption capacity for rare earth ion Ce(III) is 337.36 mg / g. Its structural characteristics and adsorption performance under different environments are specifically studied, and its adsorption mechanism is explored to provide a systematic theoretical basis for the green and efficient separation of rare earths.

Description

Technical Field

[0001] The invention belongs to the technical field of material preparation and separation, and particularly relates to a pectin-CMC composite aerogel capable of efficiently absorbing rare earth ions and an application of a preparation method thereof. Background Art

[0002] Rare earth elements, known as "industrial vitamins" and the "mother of new materials," are a crucial strategic resource. Due to their unique optical, electrical, and magnetic properties, rare earth elements are now widely used in automotive, fluid catalysts, metallurgy, medical systems, high-tech, clean energy, and military defense systems. The development of high-tech has led to an annual increase in rare earth element consumption of 3.7%-8.6%, widening the gap between supply and demand. Leaching tailings generated during the mining process contain significant quantities of rare earth ions. Therefore, as a non-renewable resource, further separation of rare earth elements from leachating tailings is crucial for fully utilizing the resource and conserving water resources.

[0003] Currently, there are many methods for extracting rare earths, such as leaching, chemical precipitation, solvent extraction, and adsorption. Among them, the adsorption method has attracted increasing attention from researchers due to its advantages such as simple process, low environmental pollution, and high extraction efficiency. The traditional adsorbents used in the early days were mainly materials such as activated carbon, silica gel, activated alumina, zeolite, and synthetic polymer resins. These adsorbents achieve physical adsorption and chemical adsorption through surface pores and the introduction of characteristic groups. Although traditional adsorbents have high adsorption properties, their high production cost, difficulty in regeneration, and poor recycling performance limit their further application. Therefore, the research of a low-cost adsorbent with good regeneration and recycling performance is the key to promoting the further development of the adsorption method.

[0004] Biomass-based materials have the advantages of being widely available and renewable. The functional groups rich in their surfaces can be modified to prepare high-value-added adsorption materials, which have broad application prospects in the field of rare earth ion recovery. With the rapid development of bio-based materials, researchers have also discovered their limitations in adsorption, such as structural instability and poor adsorption effect. Therefore, how to further improve the adsorption performance of bio-based materials in rare earth separation is an urgent problem to be solved. Rare earth hyperaccumulators such as pecans, dichotoma, and pokeweed not only have the advantages of biomass-based materials, but also can achieve efficient rare earth enrichment through their own functional groups such as carboxyl and amino groups. The cellulose, hemicellulose, and pectin in the cell walls of hyperaccumulator plants contain a large number of chelating groups such as carboxyl groups, which can provide more adsorption sites for rare earth ions and are the main site of plant enrichment. Separating the effective components from the cell walls to prepare new adsorbents is a new approach to improve the efficiency of rare earth separation. Summary of the Invention

[0005] In response to the problems that the adsorption performance of existing adsorbents for rare earth ions needs to be improved and the regeneration and recycling performance is poor, the purpose of the present invention is to construct a preparation method for a pectin-CMC composite aerogel rare earth adsorbent. The aerogel is prepared using sol-gel technology and a large number of active adsorption sites are formed through cross-linking to improve its adsorption performance for rare earth ions.

[0006] The technical solutions adopted in the present invention are as follows:

[0007] A pectin-CMC composite aerogel rare earth ion adsorption material is prepared from the following main raw materials in the following mass ratios:

[0008] The biomass adsorption materials are orange peel pectin (PC) and carboxymethyl cellulose (CMC);

[0009] The crosslinking agent is a 1% polyamide epichlorohydrin (PAE) solution.

[0010] The preparation method of pectin-CMC composite aerogel rare earth ion adsorption material includes the following main steps:

[0011] 1. Accurately weigh 4.5g of pectin and hydrolyze it in 3wt% nitric acid solution for 4h. Accurately weigh 4.5g of carboxymethyl cellulose and add it to 150ml of water and stir until completely dissolved.

[0012] 2. After the hydrolysis is completed, the pectin solution and the CMC solution are mixed at different mass ratios. Polyamide epichlorohydrin (PAE) is added as a crosslinking agent to the mixed solution and mechanically stirred for 3 hours.

[0013] 3. Pre-freeze the mixture at -80°C for 12 h and dry it in a freeze dryer.

[0014] 4. The freeze-dried composite aerogel was placed in a vacuum drying oven and dried overnight.

[0015] Furthermore, in step 1, the mass ratio of pectin hydrolyzed in the nitric acid solution is 3 wt %.

[0016] Furthermore, in step 2, the mixing mass ratios of the pectin solution and the CMC solution are 5:0, 3:2, 1:1, 2:3, and 0:5, respectively.

[0017] Furthermore, in step 2, the mass ratio of the pectin-CMC mixed solution to the crosslinking agent PAE is 4:1.

[0018] Furthermore, the temperature of the vacuum drying oven in step 4 is set to 80°C.

[0019] Technical advantages of the present invention:

[0020] The pectin-CMC composite aerogel prepared by the present invention has low crystallinity and good hydrophilicity, and has an excellent structural basis in the field of adsorption of rare earth ions. Its surface has abundant active adsorption groups, which mainly achieve adsorption of rare earth ions through electrostatic interaction, ion exchange and chelation. At pH=6,

[0021] Static adsorption experiments showed a maximum adsorption capacity of 337.36 mg / g for Ce(III) in water, significantly exceeding the adsorption capacity of other traditional adsorbents. Adsorption experiments also demonstrated that the pectin-CMC composite aerogel exhibits excellent regeneration and recycling properties, demonstrating potential applications in the extraction of rare earth ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the SEM image of pectin-CMC composite aerogel;

[0023] Figure 2 This is the Fourier infrared spectrum of pectin-CMC composite aerogel;

[0024] Figure 3 This is the contact angle analysis diagram of pectin-CMC composite aerogel.

[0025] Figure 4 This is the effect of pH on adsorption capacity. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with specific embodiments.

[0027] Example 1

[0028] The biomass adsorption materials are orange peel pectin (PC) and carboxymethyl cellulose (CMC);

[0029] The crosslinking agent is a 1% polyamide epichlorohydrin (PAE) solution.

[0030] (1) Accurately weigh 4.5 g of pectin and hydrolyze it in 150 mL of 3 wt% nitric acid solution for 4 h. Accurately weigh 4.5 g of carboxymethyl cellulose and add it to 150 mL of water and stir until completely dissolved.

[0031] (2) After the hydrolysis is completed, 50 g of pectin solution is weighed, 12.5 mL of polyamide epichlorohydrin (PAE) crosslinker is added, and mechanical stirring is performed for 3 h.

[0032] (3) The mixture was pre-frozen at -80°C for 12 h and dried in a freeze dryer.

[0033] (4) The freeze-dried composite aerogel was placed in a vacuum drying oven at 80°C and dried overnight.

[0034] Example 2

[0035] The biomass adsorption materials are orange peel pectin (PC) and carboxymethyl cellulose (CMC);

[0036] The crosslinking agent is a 1% polyamide epichlorohydrin (PAE) solution.

[0037] (1) Accurately weigh 4.5 g of pectin and hydrolyze it in 150 mL of 3 wt% nitric acid solution for 4 h. Accurately weigh 4.5 g of carboxymethyl cellulose and add it to 150 mL of water and stir until completely dissolved.

[0038] (2) After the hydrolysis is completed, 30 g of pectin solution and 20 g of CMC solution are weighed, 12.5 mL of polyamide epichlorohydrin (PAE) crosslinker is added, and mechanical stirring is performed for 3 h.

[0039] (3) The mixture was pre-frozen at -80°C for 12 h and dried in a freeze dryer.

[0040] (4) The freeze-dried composite aerogel was placed in a vacuum drying oven at 80°C and dried overnight.

[0041] Example 3

[0042] The biomass adsorption materials are orange peel pectin (PC) and carboxymethyl cellulose (CMC);

[0043] The crosslinking agent is a 1% polyamide epichlorohydrin (PAE) solution.

[0044] (1) Accurately weigh 4.5 g of pectin and hydrolyze it in 150 mL of 3 wt% nitric acid solution for 4 h. Accurately weigh 4.5 g of carboxymethyl cellulose and add it to 150 mL of water and stir until completely dissolved.

[0045] (2) After the hydrolysis was completed, 25 g of pectin solution and 25 g of CMC solution were weighed, 12.5 mL of polyamide epichlorohydrin (PAE) crosslinker was added, and mechanical stirring was performed for 3 h.

[0046] (3) The mixture was pre-frozen at -80°C for 12 h and dried in a freeze dryer.

[0047] (4) The freeze-dried composite aerogel was placed in a vacuum drying oven at 80°C and dried overnight.

[0048] Example 4

[0049] The biomass adsorption materials are orange peel pectin (PC) and carboxymethyl cellulose (CMC);

[0050] The crosslinking agent is a 1% polyamide epichlorohydrin (PAE) solution.

[0051] (1) Accurately weigh 4.5 g of pectin and hydrolyze it in 150 mL of 3 wt% nitric acid solution for 4 h. Accurately weigh 4.5 g of carboxymethyl cellulose and add it to 150 mL of water and stir until completely dissolved.

[0052] (2) After the hydrolysis was completed, 20 g of pectin solution and 30 g of CMC solution were weighed, 12.5 mL of polyamide epichlorohydrin (PAE) crosslinker was added, and mechanical stirring was performed for 3 h.

[0053] (3) The mixture was pre-frozen at -80°C for 12 h and dried in a freeze dryer.

[0054] (4) The freeze-dried composite aerogel was placed in a vacuum drying oven at 80°C and dried overnight.

[0055] Example 5

[0056] The biomass adsorption materials are orange peel pectin (PC) and carboxymethyl cellulose (CMC);

[0057] The crosslinking agent is a 1% polyamide epichlorohydrin (PAE) solution.

[0058] (1) Accurately weigh 4.5 g of pectin and hydrolyze it in 150 mL of 3 wt% nitric acid solution for 4 h. Accurately weigh 4.5 g of carboxymethyl cellulose and add it to 150 mL of water and stir until completely dissolved.

[0059] (2) After the hydrolysis is completed, 50 g of CMC solution is weighed, 12.5 mL of polyamide epichlorohydrin (PAE) crosslinker is added, and mechanical stirring is performed for 3 h.

[0060] (3) The mixture was pre-frozen at -80°C for 12 h and dried in a freeze dryer.

[0061] (4) The freeze-dried composite aerogel was placed in a vacuum drying oven at 80°C and dried overnight.

[0062] The pectin-CMC composite aerogel prepared in the example was tested. Figure 1 This is the SEM image of pectin-CMC composite aerogel. The pectin-CMC composite aerogel has a three-dimensional network porous structure, indicating that the material was successfully prepared.

[0063] Figure 2 The Fourier transform infrared spectrum shows that the five adsorbents show different stretching vibration peak intensities, which indicates that the biomass content may affect the active groups in the composite aerogel and thus affect the adsorption sites of the adsorbent. -1 The characteristic peak at 2940 cm is related to the stretching vibration of OH. -1The characteristic peak at 1600 cm is related to the stretching vibration of CH. Compared with pure pectin aerogel (P5C0) and pure CMC aerogel (P0C5), the OH and CH stretching vibration peaks of composite aerogels (P3C2, P1C1, P2C3) are broadened, indicating that there is an interaction between pectin and CMC, and the two are successfully cross-linked. For CMC aerogel (P0C5), the peak at 1600 cm -1 and 1410 cm -1 The broad bands at 1600 cm and 200 cm are attributed to the stretching vibrations of the symmetrical and asymmetrical structures of the -COO– groups. -1 The stretching vibration peak at 1740 cm -1 At 1410 cm -1 The broadband at 1640 cm -1 At the same time, the composite aerogel showed the characteristic C-NH2 stretching vibration band of pectin. This evidence confirms that the cross-linking reaction between pectin and CMC has successfully occurred. The characteristic functional groups contained in both are introduced into the composite aerogel, increasing the variety and content of active groups and providing more active adsorption sites for rare earth ions.

[0064] The pectin-CMC composite aerogel prepared in the example was tested for contact angle. Figure 3 The following is a contact angle analysis chart. As can be seen, the contact angles of the original pectin and aerogel are 57° and 56°, respectively, while the contact angles of the original CMC and aerogel are 37° and 38°, respectively. There is no significant difference in the contact angles between the original pectin and CMC aerogel forms. However, the contact angles of the crosslinked composite aerogels decrease significantly, and the degree of decrease varies with the crosslinking ratios. The contact angles of P3C2, P1C1, and P2C3 are 29°, 26°, and 19.7°, respectively. This is likely due to the addition of more hydrophilic groups, such as hydroxyl and carboxyl groups, during the crosslinking process, making the adsorbent more susceptible to hydrogen bonding in water, thereby increasing its hydrophilicity. P2C3 exhibits the smallest contact angle of 19.7°, indicating the highest hydrophilicity. This allows the adsorbent to more easily bind to REEs, enhancing the material's adsorption capacity.

[0065] Adsorption tests were conducted on the pectin-CMC composite aerogels prepared in the example. 10 mg of aerogel was added to 10 mL of Ce(III) solution and allowed to adsorb on a thermostatic oscillator for 2 hours until equilibrium was reached, maintaining the rotation speed at 150 rpm. The pH of the solution was adjusted to 2, 3, 4, 5, 6, and 7 using HNO3 or NaOH, respectively. Figure 4The figure below shows the effect of different pH values ​​on adsorption capacity. Adsorption tests were conducted at different pH values. As can be seen from the figure, PCA still has good adsorption capacity under acidic conditions. Furthermore, as the acidity decreases, the adsorption capacity gradually increases, with the best adsorption performance at pH 6. This may be due to competition between H (I) and Ce (III) for adsorption sites. When the acidity is strong, the concentration of H (I) in the solution is high, the protonation effect is strong, and H (I) and Ce (III) compete for adsorption sites, resulting in lower adsorption performance. As the pH increases, the protonation effect gradually weakens, and the adsorption capacity increases.

Claims

1. A method for preparing a pectin-CMC composite aerogel rare earth ion adsorption material, characterized in that: The steps include: (1) Accurately weigh 4.5 g of orange peel pectin and hydrolyze it in 3 wt% nitric acid solution for 4 h; accurately weigh 4.5 g of carboxymethyl cellulose and add it to 150 ml of water and stir until completely dissolved; (2) After the hydrolysis is completed, the orange peel pectin solution and the CMC solution are mixed in a mass ratio of 2:3, polyamide epichlorohydrin is added as a crosslinking agent, and mechanically stirred for 3 h; (3) The mixture was pre-frozen at -80°C for 12 h and dried in a freeze dryer; (4) The freeze-dried composite aerogel was placed in a vacuum drying oven and dried overnight.

2. The method for preparing a pectin-CMC composite aerogel rare earth ion adsorption material according to claim 1, characterized in that: The mass ratio of pectin hydrolyzed in the nitric acid solution in the step (1) is 3 wt %.

3. The method for preparing a pectin-CMC composite aerogel rare earth ion adsorption material according to claim 1, wherein the mass ratio of the pectin-CMC mixed solution to the polyamide epichlorohydrin in step (2) is 4:

1.

4. The method for preparing a pectin-CMC composite aerogel rare earth ion adsorption material according to claim 1, wherein the temperature of the vacuum drying oven in step (4) is set to 80°C.

5. Use of the pectin-CMC composite aerogel rare earth ion adsorption material prepared by the preparation method according to claim 1 in the adsorption and separation of rare earth ions.

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