Composite adsorbent as well as preparation method and application thereof

Abstract

The invention provides a composite adsorbent and a preparation method and application thereof.The composite adsorbent is prepared by taking a food processing by-product banana peel which is low in cost, simple and easy to obtain as a raw material and adsorbing a modifier chitosan acetic acid solution on the banana peel, the components have a synergistic effect, the banana peel is taken as a carrier, and the composite adsorbent is prepared from the banana peel and the chitosan acetic acid solution. Hydroxyl and amino functional groups contained in the modifier increase adsorption sites of the modifier to chloropropanol, and the specific combination mode of the banana peel and the chitosan acetic acid solution makes the functional groups on the composite adsorbent fully utilized, so the adsorption capacity of the composite adsorbent to the chloropropanol is improved, and the effect of removing the chloropropanol in the polyamide epichlorohydrin papermaking wet strength agent is significant; and the banana peel is natural, green and non-toxic and does not cause secondary pollution to the wet strength agent, meanwhile, the resource utilization efficiency of agricultural and sideline products can be improved by using the banana peel, and wide application prospects are achieved.

Description

Technical Field

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

[0002] Food contact paper often needs to use wet strength agents in the pulp to improve the strength of the paper and make the paper performance meet the requirements. Polyamidoamine-epichlorohydrine (PAE) resin-based wet strength agents have become the most widely used wet strength agents at present. Epichlorohydrin (ECH) is an important raw material for synthesizing PAE resin. When ECH is not completely reacted, its side reaction will produce chloropropanol substances 3-chloro-1,2-propanediol (3-MCPD) and 1,3-dichloro-2-propanol (1,3-DCP). 3-MCPD and 1,3-DCP have been classified as potential carcinogens (category 2B) by the International Agency for Research on Cancer, and these two substances will remain on the paper products with the addition of wet strength agents, thus bringing the risk problem of chloropropanol pollution in food contact paper products.

[0003] At present, the methods for removing chloropropanol from polyamidoamine-epichlorohydrine papermaking wet strength agents include controlling the production process and post-treatment. Among the post-treatment technologies, the adsorption method has attracted much attention due to its advantages such as simple operation and high efficiency. Compared with other methods, the physical adsorption method is easy to operate, low in cost and high in efficiency, and can also avoid the generation of harmful intermediates, which is an effective chloropropanol removal technology.

[0004] The core of the physical adsorption method is the selection of the adsorption material. At present, mainly wood-based activated carbon is used as the adsorbent to remove chloropropanol from polyamidoamine-epichlorohydrine papermaking wet strength agents. Activated carbon is added to the wet strength agent, stirred and 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 addition amount of activated carbon is 100 g / L, the removal rate of chloropropanol is about 90%. When the addition amount of activated carbon is 200 g / L, the removal rate of chloropropanol can reach 99.6%.

[0005] However, the adsorption of chloropropanol by activated carbon mainly depends on the adsorption capacity of micropores and mesopores. The adsorption process is related to the mass transfer and diffusion of chloropropanol, which is a physical adsorption of single-molecule action. The characteristic of physical adsorption is that there is no selectivity, and small molecule substances other than chloropropanol will also enter the pores and occupy the adsorption sites. Therefore, in the actual application process, it is necessary to increase the dosage of activated carbon to improve the removal rate of chloropropanol. In addition, activated carbon is obtained by carbonization and activation of carbon-containing materials, with limited adsorption capacity and difficult recovery, and its cost will limit 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 preparation method of the above composite adsorbent.

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

[0009] The technical solution adopted by the present invention is as follows: A composite adsorbent, the main active components of which are composed of banana peel and chitosan acetate solution, and the weight ratio of the banana peel to the chitosan acetate solution is 2-15:1.

[0010] Preferably, for the above composite adsorbent, the weight ratio of the banana peel to the chitosan acetate solution is 8-12:1.

[0011] Preferably, for the above composite adsorbent, the weight ratio of the banana peel to the chitosan acetate solution is 10:1.

[0012] The preparation method of the above composite adsorbent is as follows: Dry the banana peel and grind it into powder, then mix it with the chitosan acetate solution according to the ratio, stir at 50-80°C for 6-8h, carry out centrifugal separation and washing, and dry at 50-70°C to obtain the composite banana peel adsorbent material.

[0013] The application of the above composite adsorbent in removing chloropropanol.

[0014] Preferably, for the application of the above composite adsorbent, the composite adsorbent is used as an adsorbent material to remove chloropropanol in the papermaking wet strength agent polyamide epichlorohydrin.

[0015] Preferably, for the application of the above composite adsorbent, put the composite adsorbent into the polyamide epichlorohydrin papermaking wet strength agent, shake it and then centrifuge it.

[0016] Preferably, for the application of the above composite adsorbent, the input amount of the composite adsorbent is 30g / L, shake and adsorb at 200 revolutions per minute for 30 minutes and then centrifuge.

[0017] The beneficial effects of the present invention are: The above-mentioned composite adsorbent is prepared by using banana peel, a by-product of food processing that is inexpensive and easily available, as the raw material, and adsorbing a chitosan acetate solution, a modifier, on the banana peel. The components synergistically interact with each other. With the banana peel as the carrier, the hydroxyl and amino functional groups contained in the modifier increase the adsorption sites for chloropropanol. The specific combination of the banana peel and the chitosan acetate solution enables the full utilization of the functional groups on the composite adsorbent, thereby improving the adsorption capacity for chloropropanol and achieving a significant effect in removing chloropropanol from polyamide epichlorohydrin papermaking wet strength agent. Moreover, the 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. Description of the Drawings

[0018] Figure 1 It is a comparison chart of the removal rates of 1,3-DCP and 3-MCPD by each adsorbent in the comparative example. Detailed Embodiments

[0019] In order to enable those skilled in the art to better understand the technical solution of the present invention, the following further details the technical solution of the present invention in combination with specific embodiments.

[0020] Example 1 A composite adsorbent is prepared by the following method: Chitosan is dissolved in a 1-2% acetic acid solution, and after stirring at room temperature for 1-2 h, a chitosan acetate solution with a volume fraction of 1-2% is formed. It is mixed with banana peel powder (powder obtained by drying and grinding banana peel) at a weight ratio of 1:10, and stirred at 50 °C for 6 h. After the reaction is completed, the precipitate is filtered, and the precipitate is thoroughly rinsed with deionized water and dried at 70 °C for 12 h to obtain a chitosan banana peel composite adsorbent.

[0021] Example 2 A composite adsorbent is prepared by the following method: β-Cyclodextrin is dissolved in an aqueous solution, and after stirring at room temperature for 1-2 h, a β-cyclodextrin solution with a volume fraction of 10-12% is formed. It is mixed with banana peel powder at a weight ratio of 1:5, and stirred at 50 °C for 6 h. After the reaction is completed, the precipitate is filtered, and the precipitate is thoroughly rinsed with deionized water and dried at 70 °C for 12 h to obtain a β-cyclodextrin banana peel composite adsorbent.

[0022] Example 3 A composite adsorbent is prepared in the same way as in Example 1, except that the weight ratio of the chitosan acetate solution to the banana peel powder is 1:2.

[0023] Example 4 A composite adsorbent was prepared in the same way as in Example 1, except that the weight ratio of the chitosan acetate solution to the banana peel powder was 1:5.

[0024] Example 5 A composite adsorbent was prepared in the same way as in Example 1, except that the weight ratio of the chitosan acetate solution to the banana peel powder was 1:8.

[0025] Example 6 A composite adsorbent was prepared in the same way as in Example 1, except that the weight ratio of the chitosan acetate solution to the banana peel powder was 1:12.

[0026] Example 7 A composite adsorbent was prepared in the same way as in Example 1, except that the weight ratio of the chitosan acetate solution to the banana peel powder was 1:15.

[0027] Comparative Example 1 Activated carbon and the composite adsorbent described in Example 1 (chitosan banana peel adsorbent CS-banana peel) were respectively added to 5 mL of polyamide epichlorohydrin wet strength agent, and the addition amount was 30 g / L. After stirring at 200 rpm for 30 min, centrifugation was carried out for 30 min to separate the adsorbed sample solution from the adsorbent, and the removal rate was calculated by measuring the content of chloropropanol in the adsorbed sample solution. As Figure 1 shown, when the addition amount was 30 g / L, the removal rates of 1,3-DCP and 3-MCPD in the polyamide epichlorohydrin wet strength agent by activated carbon were 86.19% and 71.79% respectively; the removal rates of 1,3-DCP and 3-MCPD in the polyamide epichlorohydrin wet strength agent by the composite adsorbent described in Example 1 reached 99.83% and 84.15% respectively.

[0028] Comparative Example 2 Banana peel powder and the composite adsorbent described in Example 1 (chitosan banana peel adsorbent CS-banana peel) were respectively added to 5 mL of polyamide epichlorohydrin wet strength agent, and the addition amount was 30 g / L. After stirring at 200 rpm for 30 min, centrifugation was carried out for 30 min to separate the adsorbed sample solution from the adsorbent, and the removal rate was calculated by measuring the content of chloropropanol in the adsorbed sample solution. As Figure 1 shown, when the addition amount was 30 g / L, the removal rates of 1,3-DCP and 3-MCPD in the polyamide epichlorohydrin wet strength agent by banana peel powder were 99.77% and 76.67% respectively; the removal rates of 1,3-DCP and 3-MCPD in the polyamide epichlorohydrin wet strength agent by the composite adsorbent described in Example 1 reached 99.83% and 84.15% respectively.

[0029] Comparative Example 3 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 respectively added to 5 mL of polyamide epichlorohydrin wet strength agent at an addition amount of 30 g / L. After stirring for 30 min at 200 rpm, the sample solution after adsorption was separated from the adsorbent by centrifugation for 30 min, and the removal rate was calculated by measuring the content of chloropropanol in the sample solution after adsorption. As Figure 1 shown, when the addition amount was 30 g / L, the removal rates of 1,3-DCP and 3-MCPD in the polyamide epichlorohydrin wet strength agent by the β-cyclodextrin banana peel composite adsorbent were 73.03% and 30.71% respectively; the removal rates of 1,3-DCP and 3-MCPD in the polyamide epichlorohydrin wet strength agent by the composite adsorbent described in Example 1 reached 99.83% and 84.15% respectively.

[0030] In summary, the composite adsorbent of the present invention has good adsorption performance for chloropropanol in polyamide epichlorohydrin papermaking wet strength agent, and its adsorption ability for chloropropanol is significantly better than that of activated carbon at a lower dosage. Moreover, the raw materials of this adsorbent are simple and easy to obtain, the cost is low, the preparation process is simple, and it does not require harsh conditions and cumbersome steps.

[0031] The above-described embodiments are only used to describe the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A composite adsorbent, characterized in that: The main active ingredients 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.

2. The composite adsorbent 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 composite adsorbent 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 method for preparing the composite adsorbent according to any one of claims 1 to 3, characterized in that: The specific steps are as follows: (1) Dry the banana peel, grind it into powder, and mix it with chitosan acetic acid solution in a certain 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. Use of the composite adsorbent according to any one of claims 1 to 3 in removing chloropropanols.

6. The use according to claim 5, characterized in that: The composite adsorbent is used as an adsorbent material to remove chloropropanol from polyamide epichlorohydrin, a wet strength agent for papermaking.

7. The use according to claim 6, characterized in that: The composite adsorbent is added into the polyamide epichlorohydrin papermaking wet strength agent, shaken and then centrifuged.

8. The use according to claim 7, 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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