Copper ion imprinted cross-linked grafted chitosan adsorbent and preparation method thereof

Abstract

The invention provides a copper ion imprinted cross-linked grafted chitosan adsorbent and a preparation method thereof. The preparation method comprises the following steps: adding an initiator into a mixed solution of a copper ion template agent and a chitosan solution to obtain a first reaction solution; carrying out grafting reaction on the first reaction solution to obtain a second reaction solution; adding a cross-linking agent into the second reaction liquid, carrying out cross-linking curing, and carrying out solid-liquid separation to obtain an intermediate; and eluting the copper ions in the intermediate to obtain the copper ion imprinted cross-linked grafted chitosan adsorbent. A solvent of the chitosan solution comprises water and unsaturated carboxylic acid. According to the preparation method disclosed by the invention, an ion imprinting technology is combined with crosslinking and grafting modification, so that the copper ion imprinting crosslinking grafted chitosan adsorbent is endowed with higher stability and selectivity, and the cyclic regeneration performance of the copper ion imprinting crosslinking grafted chitosan adsorbent is improved; the adsorption kinetics and the adsorption thermodynamics of the copper ion imprinted cross-linked grafted chitosan adsorbent are optimized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, in particular to the removal of noble metal ions by adsorption, and more particularly to a copper ion imprinted crosslinked grafted chitosan adsorbent and a preparation method thereof. BACKGROUND

[0002] Wastewater discharged from metal smelting, battery, printing and dyeing and other industrial production processes often contains copper, causing serious water pollution and posing a great threat to human living environment and health. The methods for removing copper ions from wastewater mainly include membrane filtration, chemical precipitation, ion exchange or electrochemistry, etc. However, these methods have problems such as unsatisfactory removal effect, high treatment cost, complex process flow, etc. As an effective separation technology, adsorption has the advantages of high separation efficiency, simple operation, easy recovery of separation products, etc., and has a wide application prospect in the field of heavy metal ion wastewater treatment. Natural polymer chitosan has the advantages of wide source and biodegradability, and using it as a heavy metal ion adsorbent will not cause secondary pollution. However, ordinary chitosan is easily dissolved and lost in aqueous solution, especially in acidic aqueous solution, which greatly limits its application.

[0003] CN106861663A discloses a microfluidic synthesis imprinted adsorbent for copper-containing wastewater treatment, which is prepared by the following method: dissolving soluble copper salt and acetic acid in a chitosan solution, the mass ratio of copper ions, chitosan and acetic acid being 1:(1-5):(1-4), heating and stirring to obtain a dispersion phase; then using a microfluidic device to shear the continuous phase from the dispersion phase, and introducing the formed microdroplets into a solidification liquid for crosslinking and solidification; finally, using a desorption agent to desorb the solidified microdroplets, and washing and drying, to obtain the required adsorbent. The invention has the advantages of simple operation and low cost, and the obtained adsorbent has specific selective adsorption performance for copper ions, fast adsorption speed, high adsorption capacity and reusability. The use of microfluidic granulation technology makes the particle size uniform, and the components, morphology and size are uniform, which has a far-reaching research prospect for the treatment of copper ion-containing industrial wastewater.

[0004] CN109174034A discloses a copper ion imprinted chitosan / carboxymethyl cellulose sodium composite adsorbent and a preparation method thereof. The preparation process includes: preparing a carboxymethyl cellulose sodium solution, adding an acidic solution, chitosan and a copper salt respectively, slowly adding a basic solution to the solution until the pH is 5 after stirring and dissolving, precipitating composite imprinted gel particles, then adding epichlorohydrin for crosslinking, and then acid washing to remove Cu 2+ , alkaline solidification, water washing, ethanol washing and drying to obtain the copper ion imprinted chitosan / carboxymethyl cellulose sodium composite adsorbent. The composite adsorbent prepared by the invention is a gel particle with irregular shape and developed pore structure, and has high adsorption capacity for Cu 2+The copper ion imprinting composite adsorbent has good adsorption and selectivity, can be regenerated and reused, has simple preparation process, low energy consumption, environmental friendliness, and can be widely applied to treatment of copper ion-containing wastewater and waste liquid.

[0005] CN108212114A discloses a copper ion imprinting composite adsorbent and a preparation method thereof. 2+ The preparation process comprises the following steps: configuring a chitosan acetic acid solution and a sodium carboxymethyl cellulose / sodium hydroxide composite coagulation solution respectively, dropping the chitosan acetic acid solution into the sodium carboxymethyl cellulose / sodium hydroxide composite coagulation solution to form balls, washing the balls with water, and then placing the balls in a Cu 2+ solution for imprinting, crosslinking with glutaraldehyde, and then acid washing to remove Cu 2+ , washing with water, and drying to obtain the copper ion imprinting composite adsorbent. The composite adsorbent prepared by the method has good selective adsorption capacity and can be regenerated and reused.

[0006] Therefore, it is of great significance to provide a copper ion imprinting crosslinking grafting chitosan adsorbent having excellent adsorption and selectivity for copper ions and a preparation method thereof. SUMMARY

[0007] In view of the deficiencies in the prior art, the purpose of the present application is to provide a copper ion imprinting crosslinking grafting chitosan adsorbent and a preparation method thereof. The present application combines ion imprinting technology with crosslinking and grafting modification to endow the copper ion imprinting crosslinking grafting chitosan adsorbent with higher stability and selectivity, improve the cyclic regeneration performance of the copper ion imprinting crosslinking grafting chitosan adsorbent, and further optimize the adsorption kinetics and thermodynamics of the copper ion imprinting crosslinking grafting chitosan adsorbent by introducing unsaturated carboxylic acid for grafting modification.

[0008] To achieve the purpose of the present application, the following technical solutions are adopted:

[0009] In a first aspect, the present application provides a preparation method of a copper ion imprinting crosslinking grafting chitosan adsorbent, which comprises the following steps:

[0010] adding an initiator to a mixed solution of a copper ion template and a chitosan solution to obtain a first reaction solution; performing grafting reaction on the first reaction solution to obtain a second reaction solution; adding a crosslinking agent to the second reaction solution for crosslinking and solidification, and then performing solid-liquid separation to obtain an intermediate; eluting copper ions in the intermediate to obtain the copper ion imprinting crosslinking grafting chitosan adsorbent; and the solvent of the chitosan solution comprises water and unsaturated carboxylic acid.

[0011] The application forms specific recognition sites by fixing the spatial configuration of the functional groups of the copper ion template, significantly improving the adsorption selectivity and capacity of the copper ion imprinted cross-linked grafted chitosan adsorbent for copper ions. At the same time, the use of cross-linking agents can enhance the structural stability of the material, reduce the steric hindrance of the active sites, and improve the regeneration performance of the copper ion imprinted cross-linked grafted chitosan adsorbent. By inducing the reaction of chitosan and cross-linking agent with copper ion template, and then eluting to form imprinted cavities, efficient adsorption and desorption cycles of copper ions can be realized.

[0012] Chitosan is a natural biological macromolecule after deacetylation of chitin. In the application, the degree of deacetylation of chitosan is ≥95%, and the viscosity is 100-200 mpa.s. In the application, the solvent for the chitosan solution includes unsaturated carboxylic acid, which provides a suitable acidic environment for the protonation of chitosan, promotes the protonation of chitosan, and at the same time, the carboxylic acid group forms a hydrogen bond with the hydroxyl or amino group of chitosan, further promoting the dispersion of chitosan. Under the action of the subsequent initiator, the unsaturated carboxylic acid monomer realizes the graft modification of chitosan, thereby introducing a large number of carboxyl groups on the chitosan chain, and forming a three-dimensional network composed of chitosan main chain and unsaturated carboxylic acid polymer side chain, thereby enhancing the coordination ability for metal ions.

[0013] Preferably, the copper ion template includes any one or a combination of at least two of copper sulfate, copper chloride, copper acetate or copper nitrate, and a typical but non-limiting combination includes a combination of copper sulfate and copper chloride, or a combination of copper acetate and copper nitrate, preferably copper sulfate.

[0014] Preferably, the initiator includes any one or a combination of at least two of potassium persulfate, ammonium persulfate or sodium bisulfite, and a typical but non-limiting combination includes a combination of potassium persulfate and ammonium persulfate, a combination of sodium bisulfite and potassium persulfate, or a combination of ammonium persulfate and sodium bisulfite.

[0015] Preferably, the cross-linking agent includes glutaraldehyde.

[0016] Preferably, the unsaturated carboxylic acid includes any one or a combination of at least two of acrylic acid, itaconic acid or maleic acid, and a typical but non-limiting combination includes a combination of acrylic acid and itaconic acid, a combination of maleic acid and acrylic acid, or a combination of itaconic acid and maleic acid.

[0017] Preferably, the volume ratio of water to unsaturated carboxylic acid is (35-70):1, for example, it can be 30:1, 40:1, 45:1, 50:1, 55:1, 60:1, 65:1 or 70:1, including but not limited to the listed values, and other values not listed in the value range are also applicable.

[0018] Preferably, the mass concentration of the chitosan in the chitosan solution is 10 g / L to 20 g / L, for example, it can be 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L or 20 g / L, including but not limited to the listed values, other values in the value range are also applicable.

[0019] Preferably, the mass concentration of the copper ions in the first reaction solution is 0.25 g / L to 1.35 g / L, for example, it can be 0.25 g / L, 0.45 g / L, 0.65 g / L, 0.85 g / L, 1.05 g / L, 1.15 g / L, 1.25 g / L or 1.35 g / L, including but not limited to the listed values, other values in the value range are also applicable.

[0020] Preferably, the mass concentration of the initiator in the first reaction solution is 4.5 g / L to 10 g / L, for example, it can be 4.5 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, including but not limited to the listed values, other values in the value range are also applicable.

[0021] Preferably, the grafting reaction comprises a first grafting reaction and a second grafting reaction; the temperature of the first grafting reaction is higher than that of the second grafting reaction.

[0022] Preferably, the temperature of the first grafting reaction is 70°C to 90°C, for example, it can be 70°C, 75°C, 80°C, 85°C or 90°C, including but not limited to the listed values, other values in the value range are also applicable.

[0023] Preferably, the time of the first grafting reaction is 15 min to 60 min, for example, it can be 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, including but not limited to the listed values, other values in the value range are also applicable.

[0024] Preferably, the temperature of the second grafting reaction is 50°C to 70°C, for example, it can be 50°C, 55°C, 60°C, 65°C or 70°C, including but not limited to the listed values, other values in the value range are also applicable.

[0025] Preferably, the time of the second grafting reaction is 40 min to 90 min, for example, it can be 40 min, 50 min, 60 min, 70 min, 80 min or 90 min, including but not limited to the listed values, other values in the value range are also applicable.

[0026] Preferably, the grafting reaction is carried out under an inert atmosphere, which includes nitrogen and / or an inert gas.

[0027] Preferably, the inert gas includes any one or a combination of at least two of helium, neon or argon.

[0028] Preferably, the volume ratio of the cross-linking agent to the second reaction solution is 1 : (95-300), which can be 1 :95, 1 : 100, 1 : 125, 1 : 150, 1 : 175, 1 : 200, 1 : 225, 1 : 250, 1 : 275 or 1 : 300, including but not limited to the listed values, and other values not listed within the value range are also applicable.

[0029] Preferably, the temperature for cross-linking and curing is 35-55°C, which can be 35°C, 40°C, 45°C, 50°C or 55°C, including but not limited to the listed values, and other values not listed within the value range are also applicable.

[0030] Preferably, the time for cross-linking and curing is 1-3h, which can be 1h, 1.5h, 2h, 2.5h or 3h, including but not limited to the listed values, and other values not listed within the value range are also applicable.

[0031] Preferably, the method for solid-liquid separation includes centrifugation.

[0032] Preferably, the preparation method further includes washing and drying the intermediate using water and ethanol, respectively.

[0033] Preferably, the washing method includes centrifugal washing.

[0034] Preferably, the drying temperature is 50-80°C, which can be 50°C, 60°C, 70°C or 80°C, including but not limited to the listed values, and other values not listed within the value range are also applicable. The time for drying is not specifically limited, and is aimed at complete evaporation of residual solvent.

[0035] As a preferred technical solution of the present application, the elution method includes mixing the intermediate with a template removal agent solution to elute copper ions in the intermediate.

[0036] Preferably, in the template removal agent solution, the template removal agent includes any one or a combination of at least two of disodium ethylenediaminetetraacetate, dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid, and a typical but non-limiting combination includes a combination of disodium ethylenediaminetetraacetate and dilute hydrochloric acid, or a combination of dilute sulfuric acid and dilute nitric acid.

[0037] Preferably, the concentration of the template-removing agent solution is 0.05 mol / L to 0.25 mol / L, for example, it can be 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L or 0.25 mol / L, including but not limited to the listed values, other values not listed in the value range are also applicable.

[0038] Preferably, the solid-liquid ratio of the intermediate to the template-removing agent solution is 0.5 g / L to 2 g / L, for example, it can be 0.5 g / L, 0.75 g / L, 1 g / L, 1.25 g / L, 1.5 g / L, 1.75 g / L or 2 g / L, including but not limited to the listed values, other values not listed in the value range are also applicable.

[0039] Preferably, the elution time is 2 h to 10 h, for example, it can be 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h, including but not limited to the listed values, other values not listed in the value range are also applicable.

[0040] Preferably, the preparation method further comprises washing, drying and grinding the copper ion imprinted cross-linked grafted chitosan.

[0041] Preferably, the washing method comprises centrifugal washing with water and ethanol respectively.

[0042] In the second aspect, the application provides a copper ion imprinted cross-linked grafted chitosan adsorbent, which is prepared by the preparation method of the first aspect.

[0043] Compared with the prior art, the application has the following beneficial effects:

[0044] The application combines ion imprinting technology with cross-linking and grafting modification, which endows the copper ion imprinted cross-linked grafted chitosan adsorbent with higher stability and selectivity, improves the cyclic regeneration performance of the copper ion imprinted cross-linked grafted chitosan adsorbent, and further optimizes the adsorption kinetics and adsorption thermodynamics of the copper ion imprinted cross-linked grafted chitosan adsorbent by introducing unsaturated carboxylic acid for grafting modification. BRIEF DESCRIPTION OF DRAWINGS

[0045] Fig. 1 is the SEM image of chitosan in Example 1.

[0046] Fig. 2 is the SEM image of the intermediate prepared in Example 1.

[0047] Fig. 3 is the SEM image of the copper ion imprinted cross-linked grafted chitosan adsorbent prepared in Example 1. DETAILED DESCRIPTION

[0048] The technical solutions of the present application are further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations on the present application.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the use of the terms "including," "comprising," "having" and variations thereof herein is intended to be broad and encompass the terms "consisting of" and "consisting essentially of."

[0050] In the description of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0051] In one specific embodiment, the present application provides a preparation method of a copper ion imprinted crosslinked grafted chitosan adsorbent, the preparation method comprising:

[0052] adding an initiator to the mixture of the copper ion template and the chitosan solution to obtain a first reaction solution, the solvent of the chitosan solution comprising water and an unsaturated carboxylic acid in a volume ratio of (35-70):1, the mass concentration of chitosan in the chitosan solution being 10 g / L-20 g / L, the mass concentration of copper ions in the first reaction solution being 0.25 g / L-1.35 g / L, and the mass concentration of the initiator being 4.5 g / L-10 g / L; performing a grafting reaction on the first reaction solution under an inert atmosphere, the grafting reaction comprising first incubating at 70℃-90℃ for 15 min-60 min, and then incubating at 50℃-70℃ for 40 min-90 min to complete the grafting reaction, thereby obtaining a second reaction solution; adding a crosslinking agent to the second reaction solution, the volume ratio of the crosslinking agent to the second reaction solution being 1:(95-300), and crosslinking and solidifying at 35℃-55℃ for 1 h-3 h, followed by centrifugal separation, washing the intermediate with water and ethanol respectively, and vacuum drying at 50℃-80℃; mixing the intermediate with a template removal agent solution having a concentration of 0.05 mol / L-0.25 mol / L according to a solid-liquid ratio of 0.5 g / L-2 g / L, stirring and eluting for 2 h-10 h to elute the copper ions from the intermediate, thereby obtaining the copper ion imprinted crosslinked grafted chitosan adsorbent, and washing, drying and grinding the copper ion imprinted crosslinked grafted chitosan.

[0053] In some embodiments, the copper ion template agent includes any one or a combination of at least two of copper sulfate, copper chloride, copper acetate or copper nitrate, typically but not limitedly including a combination of copper sulfate and copper chloride, or a combination of copper acetate and copper nitrate, preferably copper sulfate.

[0054] In some embodiments, the initiator includes any one or a combination of at least two of potassium persulfate, ammonium persulfate or sodium bisulfite, typically but not limitedly including a combination of potassium persulfate and ammonium persulfate, a combination of sodium bisulfite and potassium persulfate, or a combination of ammonium persulfate and sodium bisulfite.

[0055] In some embodiments, the crosslinking agent includes glutaraldehyde.

[0056] In some embodiments, the unsaturated carboxylic acid includes any one or a combination of at least two of acrylic acid, itaconic acid or maleic acid, typically but not limitedly including a combination of acrylic acid and itaconic acid, a combination of maleic acid and acrylic acid, or a combination of itaconic acid and maleic acid.

[0057] In some embodiments, the inert atmosphere includes nitrogen and / or an inert gas.

[0058] In some embodiments, the inert gas includes any one or a combination of at least two of helium, neon or argon.

[0059] In the present application, the template removal agent is selected from a material with strong coordination ability. The template removal agent can bind with copper ions preferentially through chelation competition, break the coordination bond with the polymer, form a water-soluble complex, and separate from the three-dimensional network composed of the chitosan main chain and the unsaturated carboxylic acid polymer side chain.

[0060] In some embodiments, the template removal agent in the template removal agent solution includes any one or a combination of at least two of disodium ethylenediaminetetraacetate, dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid, typically but not limitedly including a combination of disodium ethylenediaminetetraacetate and dilute hydrochloric acid, or a combination of dilute sulfuric acid and dilute nitric acid.

[0061] In another specific embodiment, the present application provides a copper ion imprinted crosslinked grafted chitosan adsorbent, which is prepared by the preparation method described in the aforementioned specific embodiment.

[0062] Example 1

[0063] The present embodiment provides a preparation method of a copper ion imprinted crosslinked grafted chitosan adsorbent, which includes:

[0064] Potassium persulfate was added to a mixture of copper sulfate and chitosan solution to obtain a first reaction solution, wherein the solvent of the chitosan solution was water and acrylic acid in a volume ratio of 56:1, the mass concentration of chitosan in the chitosan solution was 14 g / L, the mass concentration of copper ions in the first reaction solution was 0.8 g / L, and the mass concentration of potassium persulfate was 5.6 g / L; under a nitrogen atmosphere, the first reaction solution was first heated to 80° C. for 30 min, and then kept at 60° C. for 60 min to complete the grafting reaction to obtain a second reaction solution; 50 vol% pentane was added to the second reaction solution. A dialdehyde aqueous solution, wherein the volume ratio of glutaraldehyde to the second reaction liquid in the 50% glutaraldehyde aqueous solution is 1:145, cross-linking and curing at 40°C for 2 hours, centrifuging to obtain an intermediate, washing the intermediate with water and ethanol three times respectively, and vacuum drying at 60°C; mixing the intermediate with a disodium ethylenediaminetetraacetic acid solution with a concentration of 0.1 mol / L according to a solid-liquid ratio of 1 g / L, stirring and eluting for 2 hours to elute copper ions in the intermediate to obtain the copper ion imprinted cross-linked grafted chitosan adsorbent, and washing, drying and grinding the copper ion imprinted cross-linked grafted chitosan.

[0065] Example 2

[0066] This embodiment provides a method for preparing a copper ion imprinted cross-linked grafted chitosan adsorbent, the preparation method comprising:

[0067] Potassium persulfate was added to a mixture of copper chloride and chitosan solution to obtain a first reaction solution, wherein the solvent of the chitosan solution was water and acrylic acid in a volume ratio of 35:1, the mass concentration of chitosan in the chitosan solution was 10 g / L, the mass concentration of copper ions in the first reaction solution was 0.25 g / L, and the mass concentration of potassium persulfate was 4.5 g / L; under an inert atmosphere, the first reaction solution was first heated to 70° C. for 15 minutes, and then kept at 50° C. for 40 minutes to complete the grafting reaction to obtain a second reaction solution; 50 vol% glutaraldehyde was added to the second reaction solution The invention discloses a 50 vol% glutaraldehyde aqueous solution, wherein the volume ratio of glutaraldehyde to the second reaction liquid is 1:300, cross-linking and curing at 35° C. for 1 hour, centrifuging to obtain an intermediate, washing the intermediate with water and ethanol, respectively, and vacuum drying at 50° C.; mixing the intermediate with a 0.05 mol / L disodium ethylenediaminetetraacetic acid solution at a solid-liquid ratio of 0.5 g / L, stirring and eluting for 5 hours to elute the copper ions in the intermediate to obtain the copper ion imprinted cross-linked grafted chitosan adsorbent, and washing, drying and grinding the copper ion imprinted cross-linked grafted chitosan.

[0068] Example 3

[0069] The embodiment provides a preparation method of a copper ion imprinted crosslinked grafted chitosan adsorbent, and the preparation method comprises the following steps:

[0070] Potassium persulfate is added into a mixed solution of copper nitrate and a chitosan solution to obtain a first reaction solution, a solvent of the chitosan solution is water and maleic acid in a volume ratio of 70:1, a mass concentration of chitosan in the chitosan solution is 20 g / L, in the first reaction solution, a mass concentration of copper ions is 1.35 g / L, and a mass concentration of potassium persulfate is 10 g / L; under an inert atmosphere, the first reaction solution is first heated to 90 DEG C and kept for 60 min, and then kept at 70 DEG C for 90 min, so that a grafting reaction is completed, and a second reaction solution is obtained; 50vol% glutaraldehyde aqueous solution is added into the second reaction solution, a volume ratio of glutaraldehyde to the second reaction solution in the 50vol% glutaraldehyde aqueous solution is 1:95, crosslinking and solidification are carried out at 55 DEG C for 3 h, centrifugal separation is carried out, the intermediate is washed by using water and ethanol respectively, and vacuum drying is carried out at 80 DEG C; the intermediate is mixed with disodium ethylenediaminetetraacetate solution with a concentration of 0.25 mol / L according to a solid-liquid ratio of 2 g / L, stirring and elution are carried out for 10 h, copper ions in the intermediate are eluted, the copper ion imprinted crosslinked grafted chitosan adsorbent is obtained, and the copper ion imprinted crosslinked grafted chitosan is washed, dried and ground.

[0071] Embodiment 4

[0072] The embodiment provides a preparation method of a copper ion imprinted crosslinked grafted chitosan adsorbent, and the preparation method is the same as that in embodiment 3, except that equal volume of itaconic acid is used to replace maleic acid.

[0073] Embodiment 5

[0074] The embodiment provides a preparation method of a copper ion imprinted crosslinked grafted chitosan adsorbent, and the preparation method is the same as that in embodiment 1, except that a volume ratio of water to acrylic acid is 75:1.

[0075] Embodiment 6

[0076] The embodiment provides a preparation method of a copper ion imprinted crosslinked grafted chitosan adsorbent, and the preparation method is the same as that in embodiment 1, except that a volume ratio of water to acrylic acid is 30:1.

[0077] Embodiment 7

[0078] The embodiment provides a preparation method of a copper ion imprinted crosslinked grafted chitosan adsorbent, and the preparation method is the same as that in embodiment 1, except that a mass concentration of copper ions in the first reaction solution is 0.2 g / L.

[0079] Embodiment 8

[0080] The embodiment provides a preparation method of a copper ion imprinted crosslinked grafted chitosan adsorbent, which is identical to the preparation method in the embodiment 1, except that the mass concentration of copper ions in the first reaction solution is 1.5 g / L.

[0081] Embodiment 9

[0082] The embodiment provides a preparation method of a copper ion imprinted crosslinked grafted chitosan adsorbent, which is identical to the preparation method in the embodiment 1, except that the mass concentration of potassium persulfate in the first reaction solution is 3.5 g / L.

[0083] Embodiment 10

[0084] The embodiment provides a preparation method of a copper ion imprinted crosslinked grafted chitosan adsorbent, which is identical to the preparation method in the embodiment 1, except that the mass concentration of potassium persulfate in the first reaction solution is 12 g / L.

[0085] Embodiment 11

[0086] The embodiment provides a preparation method of a copper ion imprinted crosslinked grafted chitosan adsorbent, which is identical to the preparation method in the embodiment 1, except that the volume ratio of glutaraldehyde to the second reaction solution is 1:90.

[0087] Embodiment 12

[0088] The embodiment provides a preparation method of a copper ion imprinted crosslinked grafted chitosan adsorbent, which is identical to the preparation method in the embodiment 1, except that the volume ratio of glutaraldehyde to the second reaction solution is 1:310.

[0089] Embodiment 13

[0090] The embodiment provides a preparation method of a copper ion imprinted crosslinked grafted chitosan adsorbent, which is identical to the preparation method in the embodiment 1, except that the concentration of the ethylenediaminetetraacetic acid disodium solution is 0.03 mol / L.

[0091] Embodiment 14

[0092] The embodiment provides a preparation method of a copper ion imprinted crosslinked grafted chitosan adsorbent, which is identical to the preparation method in the embodiment 1, except that the concentration of the ethylenediaminetetraacetic acid disodium solution is 0.3 mol / L.

[0093] Comparative Example 1

[0094] The comparative example provides a preparation method of a copper ion imprinted chitosan adsorbent, which is identical to the preparation method in the embodiment 1, except that no potassium persulfate is added to perform the grafting reaction.

[0095] Comparative Example 2

[0096] The comparative example provides a preparation method of a copper ion imprinted chitosan adsorbent, which is the same as that of Example 1 except that no copper sulfate is added.

[0097] Performance test:

[0098] The morphology of the chitosan, the intermediate and the copper ion imprinted crosslinked grafted chitosan adsorbent described in Example 1 was tested by SEM, and the SEM images obtained by the test are shown in Figs. 1-3, respectively. Figs. 1 to 3

[0099] The copper ion concentration was 50 mg / L, the solid-liquid ratio was 0.4 g / L, and the adsorbents provided in all the examples and the comparative example were added, the time when the test adsorption capacity reached 90% of the equilibrium adsorption capacity q e was tested, and the test results are shown in Table 1.

[0100] The copper ion and nickel ion solutions with a concentration of 50 mg / L were used as the adsorption sample, the solid-liquid ratio was 0.4 g / L, and the adsorbents provided in all the examples and the comparative example were added, the selectivity of the adsorbent to copper ions was tested, and the selectivity factor was calculated, and the test results are shown in Table 1.

[0101] The adsorbents after adsorbing copper ions in all the examples and the comparative example were desorbed by 0.1 mol / L disodium ethylenediaminetetraacetate solution, the desorption rate was tested, and the adsorbent was subjected to 6 times of adsorption and desorption, the adsorption rate and the desorption rate of the 6th test were tested, and the test results are shown in Table 1. In the above test process, atomic absorption spectrophotometry was used to determine the ion concentration in the solution, C e (mg / L) and C d (mg / L) represent the initial concentration and the equilibrium concentration, V (L) represents the volume of the adsorption sample solution, m (g) represents the mass of the adsorbent, C d (mg / L) represents the concentration of the disodium ethylenediaminetetraacetate solution, V e (L) represents the volume of the disodium ethylenediaminetetraacetate solution, and the equilibrium adsorption capacity q d , the metal ion distribution coefficient K Cu / Ni , the Cu / Ni selectivity factor a e , the adsorption rate E and the desorption rate DE were calculated according to the following formulas 1-5, respectively.

[0102] q d = (C0-Ce) / m Formula 1;

[0103] K e = q Cu / Ni / Ce Formula 2;

[0104] a d ​(Cu) / K d (Ni) Formula 3;

[0105] E=(C0-Ce) / C0 Formula 4;

[0106] DE=C d V d / ((C0-C e ) / V) Formula 5.

[0107] Table 1

[0108]

[0109]

[0110] like Fig. 1 As shown in Figure 2, the surface of the unmodified chitosan film showed a stacked structure with some holes and cracks, such as Fig. 2 and Fig. 3 As shown in the figure, although the morphology of the intermediate is similar to that of the copper ion imprinted cross-linked grafted chitosan adsorbent, both of which are loose, porous, irregular, and cracked spherical structures, the surface of the intermediate is irregular, with linear synapses similar to burrs, while the copper ion imprinted cross-linked grafted chitosan adsorbent is a loose, porous aggregate of small balls with a complex texture. There are abundant nano-scale cracks on the surface, which are distributed radially or in a fibrous network, forming a porous channel structure. The surface is extremely rough, with a high specific surface area and porosity. The adsorption sites on the surface of the material are completely exposed, which increases the contact area with copper ions, which is beneficial to the improvement of the copper ion adsorption capacity and the acceleration of the adsorption kinetics.

[0111] According to the test results of Examples 1 to 3 in Table 1, the present invention combines crosslinking and grafting modification through ion imprinting technology to give the copper ion imprinted crosslinked grafted chitosan adsorbent higher stability and selectivity, improve the recycling performance of the copper ion imprinted crosslinked grafted chitosan adsorbent, and further optimize the adsorption kinetics of the copper ion imprinted crosslinked grafted chitosan adsorbent by introducing unsaturated carboxylic acid for grafting modification.

[0112] According to the test results of example 1, example 4 and example 5, it can be determined that the appropriate addition amount of acrylic acid can provide a suitable acidic environment for the protonation of chitosan, promote the protonation of chitosan, and at the same time, the carboxyl group thereof forms a hydrogen bond with the hydroxyl group or amino group of chitosan, further promoting the dispersion of chitosan, and under the action of the subsequent initiator, realizing the graft modification of chitosan by acrylic acid monomer, thereby introducing a large number of carboxyl groups on the chitosan chain, and enhancing the coordination ability to metal ions. If the addition amount of acrylic acid is too small, chitosan cannot be fully dissolved, which cannot effectively improve the adsorption capacity of the adsorbent, and if the addition amount of acrylic acid is too large, too many non-selective binding sites are formed, which cannot realize high selectivity to copper ions.

[0113] According to the test results of example 1, example 6, example 7 and comparative example 2, it can be determined that if no copper ion template is added, acrylic acid will be excessively polymerized, which cannot proceed to the subsequent chitosan crosslinking experiment, that is, the copper ion template also plays a role in stabilizing the polymerization solution, if the copper ion template is added too little, it cannot form enough copper ion imprint specific recognition sites, and if the copper ion template is added too much, the adsorption performance of the adsorbent is not obviously improved, which causes waste of resources.

[0114] According to the test results of example 1, example 8, example 9 and comparative example 1, it can be determined that if no initiator potassium persulfate is added, the crosslinking solidification reaction cannot be initiated, and the adsorbent cannot be prepared, if the addition amount of potassium persulfate is too small, the acrylic acid cannot be completely polymerized, and if the addition amount of potassium persulfate is too large, the polymerization is excessive, which leads to poor selectivity of copper ions.

[0115] According to the test results of example 1, example 10 and example 11, it can be determined that if the crosslinking agent is used in too small or too large an amount, the copper ion imprint binding sites in the three-dimensional crosslinking network are too loose or too tight, which leads to a decrease in the selective adsorption performance to copper ions.

[0116] According to the test results of example 1, example 12 and example 13, it can be determined that if the concentration of the ethylenediaminetetraacetic acid disodium solution is too low, the ethylenediaminetetraacetic acid disodium for chelating and eluting copper ions is insufficient to form enough copper ion imprint binding sites, which leads to a decrease in the adsorption capacity to copper ions.

[0117] The applicant declares that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, which falls within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a copper ion imprinted cross-linked grafted chitosan adsorbent, characterized in that: The preparation method comprises: Adding an initiator to a mixture of a copper ion template and a chitosan solution to obtain a first reaction solution; performing a grafting reaction on the first reaction solution to obtain a second reaction solution; adding a crosslinking agent to the second reaction solution, crosslinking and curing, and performing solid-liquid separation to obtain an intermediate; eluting copper ions from the intermediate to obtain the copper ion imprinted cross-linked grafted chitosan adsorbent; The solvent of the chitosan solution includes water and unsaturated carboxylic acid.

2. The preparation method according to claim 1, wherein The copper ion template comprises any one of copper sulfate, copper chloride, copper acetate or copper nitrate, or a combination of at least two thereof; And / or, the initiator includes any one or a combination of at least two of potassium persulfate, ammonium persulfate or sodium bisulfite; and / or, the cross-linking agent comprises glutaraldehyde; And / or, the unsaturated carboxylic acid includes any one of acrylic acid, itaconic acid or maleic acid, or a combination of at least two thereof.

3. The preparation method according to claim 1, wherein The volume ratio of water to unsaturated carboxylic acid is (35-70):1; And / or, in the chitosan solution, the mass concentration of chitosan is 10 g / L to 20 g / L; and / or, in the first reaction solution, the mass concentration of copper ions is 0.25 g / L to 1.35 g / L; And / or, in the first reaction solution, the mass concentration of the initiator is 4.5 g / L to 10 g / L.

4. The preparation method according to claim 1, wherein The grafting reaction includes a first grafting reaction and a second grafting reaction; the temperature of the first grafting reaction is higher than that of the second grafting reaction; And / or, the grafting reaction is performed under an inert atmosphere.

5. The preparation method according to claim 4, wherein The temperature of the first grafting reaction is 70°C to 90°C; And / or, the first grafting reaction time is 15min to 60min; and / or, the temperature of the second grafting reaction is 50° C. to 70° C.; And / or, the second grafting reaction time is 40 min to 90 min.

6. The preparation method according to claim 1, wherein The volume ratio of the cross-linking agent to the second reaction liquid is 1:(95-300); And / or, the cross-linking and curing temperature is 35° C. to 55° C.; And / or, the cross-linking and curing time is 1 hour to 3 hours; And / or, the solid-liquid separation method includes centrifugation.

7. The preparation method according to claim 1, wherein The elution method includes mixing the intermediate with a template remover solution to elute the copper ions in the intermediate.

8. The preparation method according to claim 7, wherein In the template remover solution, the template remover includes any one or a combination of at least two of disodium ethylenediaminetetraacetate, dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid; and / or, the concentration of the template remover solution is 0.05 mol / L to 0.25 mol / L; and / or, the solid-to-liquid ratio of the intermediate to the template removing agent solution is 0.5 g / L to 2 g / L; And / or, the elution time is 2h to 10h.

9. The preparation method according to claim 1, wherein The preparation method further comprises washing, drying and grinding the copper ion imprinted cross-linked grafted chitosan.

10. A copper ion imprinted cross-linked grafted chitosan adsorbent, characterized in that: The copper ion imprinted cross-linked grafted chitosan adsorbent is prepared by the preparation method according to any one of claims 1 to 9.

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