A broad-spectrum chitosan-based adsorbent, its preparation method and application

Abstract

The application provides a broad-spectrum chitosan-based adsorbent and a preparation method and application thereof, and the preparation method is as follows: carboxylated chitosan and diethylenetriamine pentaacetic acid are dissolved in water under the condition of 50 DEG C, and stirred uniformly to obtain an A solution; polyether is added into the A solution under the condition of 50 DEG C, and stirred uniformly to obtain a B solution; the B solution is added drop by drop into a polyethylene imine solution under the condition of 50 DEG C, and is left to stand for 4-10 hours to obtain a C gel, then the C gel is separated from the polyethylene imine solution, and the separated C gel is cleaned; the cleaned C spherical gel is freeze-dried to obtain the chitosan-based adsorbent. The adsorbent has the advantages of simple preparation process, no pollutant emission in the preparation process, no secondary pollution, solved problems of complex and long preparation process of traditional adsorbents, low investment cost, strong practicability, easy industrialization popularization, and the ability to solve the problems of environmental pollution and health influence caused by herbicides.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adsorbents, in particular to an adsorbent capable of adsorbing herbicides in contaminated water, and more particularly to a broad-spectrum chitosan-based adsorbent and its preparation method and application. BACKGROUND

[0002] Due to climate change, reduction of arable land, water shortage and biological and non-biological pressures, the world is facing challenges in food security. While striving to increase food production, weeds have become one of the biggest threats in crop production. To control weeds, farmers mainly rely on herbicides, but overuse can lead to environmental pollution, and these residual herbicides can flow into the human body through water bodies and other channels, causing serious impact on human health. Among them, 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2-methyl-4-chlorophenoxyacetic acid as typical herbicides of phenoxyacetic acid, mainly dissolved in water in the form of anion, and easily destroy the ecology with water cycle. However, the current technology for treating herbicides in wastewater is neither economical nor efficient in meeting existing demand, and the continuous consumption of petrochemical resources has prompted researchers to vigorously develop biological resources. In the past few decades, biomass materials have attracted much attention as stable, renewable green resources due to their abundance, biodegradability, economy, non-toxicity, physical and chemical properties that are easy to operate, etc. Among them, chitosan, as the only cationic polymer in nature, is a renewable, non-toxic, biodegradable, biocompatible and antibacterial biomass material, and its macromolecular chain contains a large number of hydroxyl and amino groups, which is an excellent choice for designing water purification functional materials. Carboxymethyl chitosan, as a chitosan derivative with carboxyl groups, solves the problem of chitosan not being directly soluble in water, and can adsorb pollutant molecules through hydrogen bonds, van der Waals forces, electrostatic effects, etc. However, the current chitosan-based adsorbent still has problems such as complex preparation scheme, poor adsorption effect, few types of pollutants removed, secondary pollution to the environment, and cannot be reused.

[0003] Therefore, in order to solve the problem of environmental pollution and health impact caused by herbicides, it is urgent to develop a new type of chitosan-based adsorbent that can efficiently remove various pollutants such as herbicides, is harmless to the environment, can be recycled multiple times, and has the potential for low-cost industrialization. SUMMARY

[0004] In order to solve the problems in the prior art, the primary purpose of the present application is to provide a broad-spectrum chitosan-based adsorbent and its preparation method and application. The adsorbent preparation process is simple, and the preparation process does not discharge pollutants, which will not cause secondary pollution. The problem of complex and lengthy preparation process of traditional adsorbents is solved. Moreover, the investment cost is low, the practicality is strong, the industrialization is easy to realize, and the problem of environmental pollution and health impact caused by herbicides can be solved.

[0005] To achieve the above object, the specific scheme adopted by the present application is:

[0006] In one aspect, the present application discloses a preparation method of a broad-spectrum chitosan-based adsorbent, mainly comprising the following steps:

[0007] S1, under the condition of 50℃, carboxymethyl chitosan (CCh) and diethylenetriamine pentaacetic acid (DTPA) are dissolved in water, stirred uniformly, and an A solution (the A solution is a CCh / DTPA mixed solution) is obtained;

[0008] S2, under the condition of 50℃, polyether is added to the A solution, stirred uniformly, and a B solution (the B solution is a CCh / DTPA / polyether solution) is obtained;

[0009] S3, under the condition of 50℃, the B solution is added dropwise to a polyethyleneimine (PEI) solution, and a C gel (the C gel is a CCh / DTPA / polyether / PEI gel) is obtained after standing for 4-10h, then the C gel is separated from the polyethyleneimine solution, and the separated C gel is cleaned;

[0010] S4, the cleaned C spherical gel is freeze-dried, and a chitosan-based adsorbent is obtained.

[0011] Further, the concentration of carboxymethyl chitosan is 3-5%;

[0012] And / or,

[0013] The concentration of diethylenetriamine pentaacetic acid is 2.5-7.5%;

[0014] And / or,

[0015] The concentration of the polyethyleneimine solution is 5-10%.

[0016] Further, in step S1, the mass ratio of carboxymethyl chitosan and diethylenetriamine pentaacetic acid is 3:2.5, 3:5, 3:7.5, 4:2.5 or 5:2.5.

[0017] Further, in step S2, the polyether is glycerol triglycidyl ether, and the amount of polyether used is 1-3%.

[0018] Further, in step S3, the cleaning method adopts anhydrous ethanol and deionized water for cleaning three times respectively.

[0019] On the other hand, the present application discloses a chitosan-based adsorbent prepared by the above preparation method.

[0020] In still another aspect, the present application discloses the application of the chitosan-based adsorbent in adsorbing herbicides in contaminated water.

[0021] Further, the herbicide is a phenoxy carboxylic acid herbicide.

[0022] Further, the phenoxy carboxylic acid herbicide contains 2,3,7,8-tetrachlorodibenzo-p-dioxin or 2-methyl-4-chlorophenoxyacetic acid.

[0023] Further, the chitosan-based adsorbent with a concentration of 0.5 g / L is added to the contaminated water with an initial concentration of 30 mg / L, and the herbicide in the contaminated water is adsorbed at a temperature of 30°C and a rotation speed of 200 r / min for 12-24 h. After adsorption saturation, the adsorbent saturated with adsorption is desorbed by oscillating for 2 h at a temperature of 50°C and a rotation speed of 200 r / min using a mixed solution containing 50 v / v% anhydrous ethanol and 1M NaOH.

[0024] Advantages:

[0025] (1) The application provides a novel broad-spectrum chitosan-based adsorbent which can adsorb various pollutants such as herbicides, has good adsorption effect, is biodegradable, and can be recycled multiple times.

[0026] (2) The preparation process of the adsorbent is simple, solves the problem of complex and lengthy preparation process of traditional adsorbents, has low investment cost, high practicability, and is easy to realize industrialization and popularization.

[0027] (3) The chitosan-based adsorbent provided by the application is mainly cross-linked between the hydroxyl groups on DTPA and the carboxyl groups, amino groups and hydroxyl groups on CCh through polyether, forms spherical gel in an instant when PEI solution is dropped, and the gel is wrapped by PEI outside, so that the gel is aminated and more easily adsorbs anionic herbicides.

[0028] (4) When the chitosan-based adsorbent provided by the application adsorbs residual herbicides in sewage, the carboxyl groups and hydroxyl groups on the adsorbent mainly produce hydrogen bond interaction with the carboxyl groups on the phenoxy carboxylic acid herbicide, and the amino groups on the adsorbent and the carboxyl groups on the herbicide mainly produce dehydration condensation reaction, so that the chitosan-based adsorbent can adsorb more 2,3,7,8-tetrachlorodibenzo-p-dioxin or 2-methyl-4-chlorophenoxyacetic acid based on the above two interactions. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a preparation flow chart of the adsorbent prepared in Example 1.

[0030] Figure 2 is a result chart of the adsorption amount and removal rate of the adsorbent after being recycled for 5 times in Examples 2-3. DETAILED DESCRIPTION

[0031] The technical solutions of the present application will be clearly and completely described below in combination with specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present application.

[0032] The present application discloses a kind of broad-spectrum chitosan-based adsorbent, its preparation method mainly includes the following steps:

[0033] S1, under the condition of 50 DEG C, carboxylated chitosan (CCh) with concentration of 3-5% and diethylene triamine pentaacetic acid (DTPA) with concentration of 2.5-7.5% are dissolved in water, stirring is uniformly, A solution (A solution is CCh / DTPA mixed solution) is obtained;Wherein, the mass ratio of carboxylated chitosan and diethylene triamine pentaacetic acid is 3:2.5, 3:5, 3:7.5, 4:2.5 or 5:2.5.

[0034] S2, under the condition of 50 DEG C, polyether (glycerol triglycidyl ether, the amount is 1-3%) is added to A solution, stirring is uniformly, B solution (B solution is CCh / DTPA / polyether solution) is obtained;

[0035] S3, under the condition of 50 DEG C, B solution is added dropwise to polyethyleneimine (PEI) solution with concentration of 5-10%, and is placed for 4-10 h to obtain C gel (C gel is CCh / DTPA / polyether / PEI gel), then C gel is separated from polyethyleneimine solution, and the separated C gel is cleaned with anhydrous ethanol and deionized water respectively three times;

[0036] S4, the cleaned C spherical gel is freeze-dried, and a chitosan-based adsorbent is obtained.

[0037] The present application also discloses the application of the chitosan-based adsorbent in adsorbing phenoxy carboxylic acid herbicides in contaminated water. The phenoxy carboxylic acid herbicides contain 2,3,7,8-tetrachlorodibenzo-p-dioxin or 2-methyl-4-chlorophenoxyacetic acid.

[0038] The technical solutions of the present application will be clearly and completely described below in combination with specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present application.

[0039] Example 1

[0040] Please refer to Figure 1 , Figure 1 is an adsorbent preparation flow chart. The present embodiment provides a preparation method of a broad-spectrum chitosan-based adsorbent, which includes the following steps:

[0041] (1) CCh was added into water at 50°C, and stirred to obtain a CCh solution with a mass fraction of 5%. Then 2.5% DTPA was added into the above prepared CCh solution, and stirred for 30 min to obtain a mixed solution of CCh / DTPA, wherein the mass ratio of CCh to DTPA was 5:2.5. The solution was named as A solution.

[0042] (2) Glycerol triglycidyl ether was added into the A solution at 50°C, and stirred for 10 min to obtain a B solution, wherein the mass ratio of CCh, DTPA and glycerol triglycidyl ether in the B solution was 5:2.5:1.

[0043] (3) The B solution was sucked into a 5 mL needle tube, and was installed into a microsyringe with an extrusion rate of 1.065 mm / ms, and was dropped into a PEI solution with a mass fraction of 5% drop by drop. C gel was obtained after standing for 8 h, and then the C gel was separated from the PEI solution, and was washed with anhydrous ethanol and deionized water for three times respectively.

[0044] (4) The washed C spherical gel was freeze-dried to obtain the chitosan-based adsorbent.

[0045] Example 2

[0046] 0.5 g / L of the chitosan-based adsorbent prepared in Example 1 was added into contaminated water containing 2,3,7,8-tetrachlorodibenzo-p-dioxin herbicide with an initial concentration of 30 mg / L, and was oscillated at a temperature of 30°C and a rotation speed of 200 r / min for 24 h to adsorb 2,3,7,8-tetrachlorodibenzo-p-dioxin in the contaminated water. After adsorption saturation, the supernatant was filtered and was analyzed by high performance liquid chromatography to calculate the adsorption amount and removal rate. Then the adsorbent saturated by adsorption was desorbed by using a mixed solution of 50 v / v% anhydrous ethanol and 1 M NaOH, and was oscillated at a temperature of 50°C and a rotation speed of 200 r / min for 2 h. The whole adsorption-desorption process was repeated for five times to determine the cyclic use performance of the adsorbent. The adsorption amount was equal to (initial concentration-adsorbed concentration) x solution volume / adsorbent dosage, and the removal rate was equal to (initial concentration-adsorbed concentration) / initial concentration. Figure 2 is a graph of the adsorption amount and removal rate of the adsorbent after five times of cyclic use, and it can be seen from the graph that the adsorption amount of the pollutant still reached more than 30 mg / g, and the removal rate was still as high as more than 80% after five times of adsorption-desorption test. Figure 2

[0047] Example 3

[0048] The difference between Example 3 and Example 2 is only that the contaminated water is contaminated water containing 2-methyl-4-chlorophenoxyacetic acid herbicide with an initial concentration of 30 mg / L.​Figure 2 It can be seen that after five times of adsorption-desorption test, the adsorption amount of 2-methyl-4-chlorophenoxyacetic acid herbicide is still more than 25 mg / g, and the removal rate is still as high as more than 76%.

[0049] The above is only the preferred embodiment of the present application, and is not intended to limit the present application in any form. Any equivalent transformation or modification made according to the essence of the present application should be covered within the protection scope of the present application.

Claims

1. A method for preparing a broad-spectrum chitosan-based adsorbent, characterized in that, It mainly includes the following steps: S1. At 50°C, carboxylated chitosan and diethylenetriaminepentaacetic acid are dissolved in water and stirred until homogeneous to obtain solution A. S2. At 50℃, glycerol triglycidyl ether is added to solution A and stirred until homogeneous to obtain solution B. S3. Under the condition of 50℃, solution B is added dropwise to polyethyleneimine solution, and the mixture is allowed to stand for 4-10 hours to obtain gel C. Then, gel C is separated from polyethyleneimine solution and the separated gel C is washed. S4. Freeze-dry the cleaned C-spherical gel to obtain the chitosan-based adsorbent.

2. The method for preparing a broad-spectrum chitosan-based adsorbent according to claim 1, characterized in that, The mass concentration of the polyethyleneimine solution is 5-10%.

3. The method for preparing a broad-spectrum chitosan-based adsorbent according to claim 1, characterized in that, In step S1, the mass ratio of carboxylated chitosan to diethylenetriaminepentaacetic acid is 3:2.5, 3:5, 3:7.5, 4:2.5, or 5:2.

5.

4. The method for preparing a broad-spectrum chitosan-based adsorbent according to claim 1, characterized in that, In step S3, the cleaning method involves washing three times each with anhydrous ethanol and deionized water.

5. A chitosan-based adsorbent prepared by the preparation method according to any one of claims 1-4.

6. The application of the chitosan-based adsorbent according to claim 5 in the adsorption of phenoxycarboxylic acid herbicides in polluted water.

7. The application according to claim 6, characterized in that, The herbicide contains 2-methyl-4-chlorophenoxyacetic acid.

8. The application according to claim 6, characterized in that, A chitosan-based adsorbent with a concentration of 0.5 g / L was added to polluted water with an initial concentration of 30 mg / L. The adsorbent was shaken at 200 r / min at 30°C to adsorb herbicides. After adsorption saturation, the saturated adsorbent was desorbed using a mixed solution containing 50 v / v% anhydrous ethanol and 1M NaOH, and shaken at 200 r / min at 50°C for 2 h.

Images