A composite adsorbent and its preparation method and application

Abstract

The invention provides a composite adsorbent, a preparation method and an application thereof. The composite adsorbent is prepared by taking banana peel, a food processing byproduct that is low-cost and easily available, as a raw material, and adsorbing a modifier chitosan acetic acid solution onto the banana peel. The components act synergistically with each other, and the banana peel is used as a carrier. The hydroxyl and amino functional groups contained in the modifier increase its adsorption sites for chloropropane. The specific combination of the banana peel and the chitosan acetic acid solution fully utilizes the functional groups on the composite adsorbent, thereby improving the adsorption capacity for chloropropane, and significantly removing chloropropane from a polyamide epichlorohydrin papermaking wet strength agent. In addition, the banana peel is naturally green and non-toxic, and will not cause secondary pollution to the wet strength agent. Simultaneously, the use of the banana peel can also improve the resource utilization efficiency of agricultural and sideline products, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorbents, in particular to a composite adsorbent and a preparation method and application thereof. Background Art

[0002] Food contact paper often requires the use of wet strength agents in the pulp to enhance the strength of the paper and achieve the required performance. Polyamidoamine-epichlorohydrine (PAE) resin-based wet strength agents have become the most widely used wet strength agents. Epichlorohydrin (ECH), a key raw material for synthesizing PAE resins, produces chloropropanols (3-chloro-1,2-propanediol) (3-MCPD) and 1,3-dichloro-2-propanol (1,3-DCP) as side reactions when ECH is not fully reacted. 3-MCPD and 1,3-DCP have been classified as potential carcinogens (Group 2B) by the International Agency for Research on Cancer. These two substances can remain on paper products after the addition of wet strength agents, posing a risk of chloropropanol contamination in food contact paper products.

[0003] Currently, methods for removing chloropropanols from polyamide-epichlorohydrin wet-strength papermaking agents include production process control and post-treatment. Adsorption, a post-treatment method, has attracted considerable attention due to its simplicity and high efficiency. Compared to other methods, physical adsorption is easy to operate, low-cost, and highly efficient. It also avoids the formation of harmful intermediates, making it an effective technology for removing chloropropanols.

[0004] The core of physical adsorption lies in the choice of adsorption material. Currently, wood-based activated carbon is primarily used as an adsorbent to remove chloropropanols from polyamide-epichlorohydrin wet-strength papermaking agents. Activated carbon is added to the wet-strength agent, stirred, adsorbed, and then centrifuged to separate the adsorbed sample from the activated carbon. The removal rate is calculated by measuring the chloropropanol content in the sample before and after adsorption. When the activated carbon dosage is 100 g / L, the chloropropanol removal rate is approximately 90%, and when the activated carbon dosage is 200 g / L, the removal rate reaches 99.6%.

[0005] However, activated carbon's adsorption of chloropropanols primarily relies on the adsorption capacity of its micropores and mesopores. The adsorption process is related to the mass transfer and diffusion of chloropropanols and is a unimolecular physical adsorption. Physical adsorption is characterized by its lack of selectivity, allowing small molecules other than chloropropanols to enter the pores and occupy adsorption sites. Therefore, in practical applications, the amount of activated carbon must be increased to improve the removal rate of chloropropanols. Furthermore, activated carbon, obtained through processes such as carbonization and activation of carbonaceous materials, has limited adsorption capacity and is difficult to recycle, limiting its large-scale use. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a composite adsorbent.

[0007] Another technical problem to be solved by the present invention is to provide a method for preparing the composite adsorbent.

[0008] Another technical problem to be solved by the present invention is to provide applications of the above composite adsorbent.

[0009] The technical solution adopted in the present invention is:

[0010] A composite adsorbent, whose main active ingredients are banana peel and chitosan acetic acid solution, wherein the weight ratio of the banana peel to the chitosan acetic acid solution is 2-15:1.

[0011] Preferably, in the above-mentioned composite adsorbent, the weight ratio of the banana peel to the chitosan acetic acid solution is 8-12:1.

[0012] Preferably, in the above-mentioned composite adsorbent, the weight ratio of the banana peel to the chitosan acetic acid solution is 10:1.

[0013] The preparation method of the composite adsorbent comprises the following specific steps:

[0014] The banana peel is dried and ground into powder, and then mixed with chitosan acetic acid solution in proportion, stirred at 50-80 DEG C for 6-8 hours, centrifuged and washed, and dried at 50-70 DEG C to obtain a composite banana peel adsorption material.

[0015] The application of the above composite adsorbent in removing chloropropanols.

[0016] Preferably, the composite adsorbent is used as an adsorption material to remove chloropropanol from polyamide epichlorohydrin, a wet strength agent for papermaking.

[0017] Preferably, the composite adsorbent is used by adding the composite adsorbent into a polyamide epichlorohydrin papermaking wet strength agent, shaking the mixture and then centrifuging the mixture.

[0018] Preferably, in the application of the composite adsorbent, the input amount of the composite adsorbent is 30 g / L, and the adsorption is carried out by shaking at 200 rpm for 30 minutes and then centrifuged.

[0019] The beneficial effects of the present invention are:

[0020] The composite adsorbent is prepared by using banana peel, a low-cost and easily available by-product of food processing, as a raw material, and adsorbing a chitosan acetic acid solution as a modifier onto the banana peel. The components work synergistically with each other, and the banana peel is used as a carrier. The hydroxyl and amino functional groups contained in the modifier increase its adsorption sites for chloropropane. The specific combination of banana peel and chitosan acetic acid solution allows the functional groups on the composite adsorbent to be fully utilized, thereby improving the adsorption capacity for chloropropane, and significantly removing chloropropane from polyamide epichlorohydrin papermaking wet strength agent. Banana peel is naturally green and non-toxic, and will not cause secondary pollution to the wet strength agent. At the same time, the use of banana peel can also improve the resource utilization efficiency of agricultural and sideline products, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a comparison chart of the 1,3-DCP and 3-MCPD removal rates of each adsorbent in the comparative example. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described in detail below in conjunction with specific implementation methods.

[0023] Example 1

[0024] A composite adsorbent is prepared by the following method:

[0025] Chitosan was dissolved in 1-2% acetic acid solution and stirred at room temperature for 1-2 h to form a chitosan acetic acid solution with a volume fraction of 1-2%. The chitosan acetic acid solution was mixed with banana peel powder (banana peel dried and ground into powder) in a weight ratio of 1:10 and stirred at 50°C for 6 h. After the reaction was completed, the precipitate was filtered and thoroughly rinsed with deionized water. The precipitate was dried at 70°C for 12 h to obtain a chitosan banana peel composite adsorbent.

[0026] Example 2

[0027] A composite adsorbent is prepared by the following method:

[0028] β-cyclodextrin was dissolved in an aqueous solution and stirred at room temperature for 1-2 h to form a β-cyclodextrin solution with a volume fraction of 10-12%. The solution was then mixed with banana peel powder in a weight ratio of 1:5 and stirred at 50°C for 6 h. After the reaction was completed, the precipitate was filtered, thoroughly rinsed with deionized water, and dried at 70°C for 12 h to obtain a β-cyclodextrin banana peel composite adsorbent.

[0029] Example 3

[0030] A composite adsorbent, prepared by the same method as in Example 1, except that the weight ratio of the chitosan acetic acid solution to the banana peel powder is 1:2.

[0031] Example 4

[0032] A composite adsorbent, prepared by the same method as in Example 1, except that the weight ratio of the chitosan acetic acid solution to the banana peel powder is 1:5.

[0033] Example 5

[0034] A composite adsorbent, prepared by the same method as in Example 1, except that the weight ratio of the chitosan acetic acid solution to the banana peel powder is 1:8.

[0035] Example 6

[0036] A composite adsorbent, prepared by the same method as in Example 1, except that the weight ratio of the chitosan acetic acid solution to the banana peel powder is 1:12.

[0037] Example 7

[0038] A composite adsorbent, prepared by the same method as in Example 1, except that the weight ratio of the chitosan acetic acid solution to the banana peel powder is 1:15.

[0039] Comparative Example 1

[0040] Activated carbon and the composite adsorbent described in Example 1 (chitosan banana peel adsorbent CS-banana peel) were added to 5 mL of polyamide epichlorohydrin wet strength agent at a dosage of 30 g / L. After stirring at 200 rpm for 30 min, the adsorbed sample solution was separated from the adsorbent by centrifugation for 30 min. The removal rate was calculated by measuring the chloropropanol content in the adsorbed sample solution. Figure 1 As shown in the figure, when the dosage is 30 g / L, the removal rates of activated carbon for 1,3-DCP and 3-MCPD in polyamide epichlorohydrin wet strength agent are 86.19% and 71.79%, respectively; the removal rates of the composite adsorbent described in Example 1 for 1,3-DCP and 3-MCPD in polyamide epichlorohydrin wet strength agent reach 99.83% and 84.15%, respectively.

[0041] Comparative Example 2

[0042] Banana peel powder and the composite adsorbent described in Example 1 (chitosan banana peel adsorbent CS-banana peel) were added to 5 mL of polyamide epichlorohydrin wet strength agent at a dosage of 30 g / L. After stirring at 200 rpm for 30 min, the adsorbed sample solution was separated from the adsorbent by centrifugation for 30 min. The removal rate was calculated by measuring the chloropropanol content in the adsorbed sample solution. Figure 1As shown in the figure, when the dosage is 30 g / L, the removal rates of banana peel powder for 1,3-DCP and 3-MCPD in polyamide epichlorohydrin wet strength agent are 99.77% and 76.67%, respectively; the removal rates of the composite adsorbent described in Example 1 for 1,3-DCP and 3-MCPD in polyamide epichlorohydrin wet strength agent reach 99.83% and 84.15%, respectively.

[0043] Comparative Example 3

[0044] The β-cyclodextrin banana peel composite adsorbent (CD-banana peel) described in Example 2 and the composite adsorbent (chitosan banana peel adsorbent CS-banana peel) described in Example 1 were added to 5 mL of polyamide epichlorohydrin wet strength agent at a dosage of 30 g / L. After stirring at 200 rpm for 30 min, the adsorbed sample solution was separated from the adsorbent by centrifugation for 30 min. The removal rate was calculated by measuring the chloropropanol content in the adsorbed sample solution. Figure 1 As shown in the figure, when the dosage is 30 g / L, the removal rates of 1,3-DCP and 3-MCPD in polyamide epichlorohydrin wet strength agent by the β-cyclodextrin banana peel composite adsorbent are 73.03% and 30.71%, respectively; the removal rates of 1,3-DCP and 3-MCPD in polyamide epichlorohydrin wet strength agent by the composite adsorbent described in Example 1 reach 99.83% and 84.15%, respectively.

[0045] In summary, the composite adsorbent of the present invention has excellent adsorption performance for chloropropanol in polyamide epichlorohydrin papermaking wet strength agent, and its adsorption capacity for chloropropanol is significantly better than that of activated carbon at a lower dosage. In addition, the raw materials of the adsorbent are simple and easy to obtain, the cost is low, and the preparation process is simple, without requiring harsh conditions and cumbersome steps.

[0046] The above-described embodiments are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. An application of a composite adsorbent in removing chloropropanols, characterized in that: The main active ingredients of the composite adsorbent are composed of banana peel and chitosan acetic acid solution, and the weight ratio of the banana peel to the chitosan acetic acid solution is 2-15:

1. The composite adsorbent is used as an adsorption material to remove chloropropanol from polyamide epichlorohydrin, a wet strength agent for papermaking. The composite adsorbent is added to the polyamide epichlorohydrin papermaking wet strength agent, shaken, and then centrifuged.

2. The use according to claim 1, characterized in that: The weight ratio of the banana peel to the chitosan acetic acid solution is 8-12:

1.

3. The use according to claim 2, characterized in that: The weight ratio of the banana peel to the chitosan acetic acid solution is 10:

1.

4. The use according to any one of claims 1 to 3, characterized in that: The composite adsorbent is prepared by the following method: (1) Dry the banana peel and grind it into powder, then mix it with chitosan acetic acid solution in proportion; (2) Stirring at 50-80°C for 6-8 h, centrifuging and washing, and drying at 50-70°C to obtain a composite banana peel adsorption material.

5. The use according to claim 1, characterized in that: The input amount of the composite adsorbent is 30 g / L, and the adsorption is carried out at 200 rpm for 30 minutes and then centrifuged.

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