CN113856646A

CN113856646A - Novel beta-cyclodextrin-chitosan cross-linked adsorption material and preparation method thereof

Info

Publication number: CN113856646A
Application number: CN202111130187.3A
Authority: CN
Inventors: 余康宸; 郁昂
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-09-26
Filing date: 2021-09-26
Publication date: 2021-12-31

Abstract

The invention belongs to the technical field of novel surfactants, and discloses a novel beta-cyclodextrin-chitosan cross-linked adsorbing material and a preparation method thereof, wherein the preparation method of the novel beta-cyclodextrin-chitosan cross-linked adsorbing material comprises the following steps: dissolving and regenerating chitosan; carrying out beta-cyclodextrin/chitosan crosslinking reaction under acidic condition. According to the invention, the processes of micro-emulsification and thermal phase separation are increased through chitosan dissolution and regeneration, crystals are re-destructured, the relative surface area of the adsorption synthetic material is increased, more contact areas are provided for subsequent experiments, the reaction efficiency is improved, and reaction sites are increased; through beta-cyclodextrin/chitosan acidic condition crosslinking reaction, the reaction condition is changed from traditional alkaline condition ring-opening crosslinking to acidic condition ring-opening crosslinking, reactants are crosslinked in the form of solute, the reaction is more sufficient, the yield of the obtained product is high, and the waste of raw materials is reduced; properly raising the reaction temperature, enhancing the activity of the epoxy chloropropane, shortening the crosslinking reaction time and having strong popularization and application capability.

Description

Novel beta-cyclodextrin-chitosan cross-linked adsorption material and preparation method thereof

Technical Field

The invention belongs to the technical field of novel surfactants, and particularly relates to a novel beta-cyclodextrin-chitosan cross-linked adsorption material and a preparation method thereof.

Background

At present, the surfactant is a surface active substance, has the unique properties of hydrophile and lipophile, is widely applied to the chemical industry, and has sufficient functions in the aspects of changing the surface property of an interface and remarkably reducing the surface tension of the interface. Surfactants can be classified into two types, ionic and nonionic surfactants, according to whether hydrophilic groups can be ionized in water, and ionic surfactants can be further classified into amphoteric surfactants, cationic surfactants and anionic surfactants.

Among the surfactants, anionic surfactants are the most widely used, the most productive, and the longest history of development. The molecular structure of the anionic surfactant has amphipathy, and the anionic surfactant is formed by combining a hydrophilic group and a hydrophobic group, wherein the hydrophilic group is usually formed by polar groups such as hydroxyl, carboxylic acid and the like, and the hydrophobic group is usually formed by combining nonpolar hydroxyl chains. Since the anionic surfactant has good water solubility, can improve the solubility of organic substances in water and reduce the surface tension of water, and the like, the anionic surfactant is most frequently applied to the fields of foaming, washing, dispersing, lubricating and the like in domestic water. According to the PSCD 2017 data, the product of the global anionic surfactant accounts for about 1200 ten thousand tons, and the product is widely used in the fields of public cleaning, pesticide chemistry, emulsion polymerization, textile auxiliaries, paint coating and the like.

Linear Alkylbenzene Sulfonate (LAS) is one of the most widely used anionic surfactants in the current life, has the characteristics of high functionality and high cost performance, is used in daily necessities such as liquid detergent, washing powder, facial cleanser, bath lotion and the like in large quantity, and data in 2017 show that 54.54 million tons of sodium dodecyl benzene sulfonate are produced in China in the year, and account for about 45 percent of the total output of the anionic surfactants, wherein most of LAS is treated with domestic water or enters natural water. Sodium dodecylbenzene sulfonate is a yellow oily liquid and is also the most used linear alkylbenzene sulfonate. It is more soluble in water than soap. Because of its low foam viscosity, the sodium dodecyl benzene sulfonate has the characteristic of easy foam disappearance while keeping the advantage of easy foaming. The sodium dodecyl benzene sulfonate is stable in chemical property, can not be decomposed in an acidic or alkaline medium and under the condition of heating, has good degreasing capability, and has good performances of reducing the surface tension and wetting, penetrating and emulsifying of water, so that the sodium dodecyl benzene sulfonate is added into industrial products and daily necessities in a large amount.

The linear alkyl benzene sulfonate can enter natural water through the ways of discharging industrial wastewater, waste residues, domestic sewage and the like, so that the environment is influenced, and the linear alkyl benzene sulfonate can be detected in various environment media. In general domestic sewage or sewage discharged by catering industry, the concentration of the anionic surfactant can reach 10mg/L, and the content of the anionic surfactant in industrial wastewater can reach 250 mg/L. According to the research of Wang Li Na et al, the market share of the laundry detergent is increasing in recent years, when the clothes are washed, the anionic surfactant discharged from the laundry detergent is about 1.5 times of the laundry detergent, and the discharge amount of linear alkylbenzene sulfonate into the environment is increased. According to the Kobukey et al, it is shown that when the surfactant concentration in water reaches 1.5mg/L, foam is generated, which affects the aesthetic appearance of the environment. Meanwhile, the foam is not easy to disappear, and an isolation layer is easy to generate on the surface of the water body, so that the gas exchange between the water body and the air is seriously influenced, the water body smells, the content of dissolved oxygen is reduced, the living environment of aquatic organisms is further damaged, and the ecological balance is damaged. In recent years, more and more toxicological studies are carried out on anionic surfactants in water, the anionic surfactants can be attached to gills of fishes or directly adsorbed by the fishes, the biological toxicity for common crucians in water is stronger, and the inhibition effect on fish antioxidant enzymes and superoxide dismutase is stronger.

According to the 'surface water environment quality standard' (3838-2002) in China, an anionic surfactant becomes one of important water quality pollutants and needs to be further treated in a sewage treatment plant. According to the Integrated wastewater discharge Standard (GB8978-1996), the discharge standards of anionic surfactants are divided into three categories, wherein the concentration of the anionic surfactant is required to be not more than 5mg/L in the first-level discharge standard, the concentration of the anionic surfactant is required to be not more than 10mg/L in the second-level discharge standard, and the concentration of the anionic surfactant is required to be not more than 20mg/L in the third-level discharge standard. When the concentration of the surfactant in the water exceeds a certain concentration, foam is easily generated, the content of dissolved oxygen in the water is reduced, and the water body smells. Meanwhile, due to the special amphipathy and solubilization of the anionic surfactant, the anionic surfactant is very easy to combine with persistent organic pollutants such as polychlorinated biphenyl, polycyclic aromatic hydrocarbon and the like in water, and more complex and profound effects are generated. Therefore, if the domestic sewage containing the anionic surfactant is not properly treated, the direct discharge of the domestic sewage into the water body causes secondary pollution of the natural water body, and immeasurable serious consequences are generated.

Cyclodextrin (CD) is a cyclic oligosaccharide formed by a series of reactions in which Cyclodextrin transferase (CGT) acted by bacillus acts on amylose. Generally, cyclodextrin is formed by combining 6-12 glucose monosaccharides, three types of commonly-used cyclodextrin, namely alpha, beta and gamma, respectively contain 6, 7 and 8 glucose monosaccharide molecules, the radius of the alpha cyclodextrin is the minimum and is only 0.5nm, a small number of organic molecules capable of being enveloped exist, the application range is limited, the relative radius of the gamma-cyclodextrin is larger and can reach 0.8nm, but the application range is also limited because the gamma-cyclodextrin is high in industrial production cost and difficult to produce on a large scale. Beta-cyclodextrin has a molecular radius of 0.6nm and a moderate size, and can be produced in large quantities industrially, so that beta-cyclodextrin is most widely applied in life due to its unique radius and inclusion capacity.

The cyclodextrin is hydrophobic and hydrophilic in the inside and is hydrophilic in the outside, the cyclodextrin is in a round table configuration in the inside, organic matters can be included and adsorbed, the cyclodextrin has good solubility due to the hydrophilic in the outside, the cyclodextrin is stable in property, and the cyclodextrin is not easy to deteriorate after being stored at normal temperature for many years. The hydrolysis is easy to occur when meeting acid, glucose and noncyclic maltose are generated by decomposition, and the glucose and the noncyclic maltose are relatively stable under the alkaline and neutral conditions and cannot react with the solution. Cyclodextrin has no fixed melting point, can start to decompose after about 200 ℃, and can easily combine with other organic matters through grafting reaction and crosslinking reaction due to a large amount of active groups contained in cyclodextrin, thereby exerting greater advantages.

At present, cyclodextrin is widely applied to the aspects of food, environmental protection, chemistry, daily necessities and the like, in the food industry, cyclodextrin can be used for protecting food pigment stability and slowly releasing aromatic odor of food due to strong enveloping capacity, and in the medicine industry, cyclodextrin is nontoxic to human bodies, can be used as a carrier of a plurality of medicines, and has the functions of improving the dosage form and the release speed of the medicines. In the environmental protection industry, the adsorbent is mostly used for treating pollutants in water or used as an air freshener carrier to improve the environmental quality.

(2) Chitosan (Chitosan), a high molecular weight polysaccharide, also called Chitosan, is produced by deacetylation of chitin. Chitin is widely present in the chitin structure of natural animals, and is also called animal cellulose because of its cellulose properties, such as high content in shrimp, crab shells and insect shells. Chitin is poorly soluble, so its application is limited, and the solubility of chitin is not improved until acetyl groups in chitin are removed with concentrated alkali. Chitosan is deacetylated, the chitosan can be called as chitosan after the deacetylation degree is more than 50%, the solubility of the chitosan is different according to the deacetylation degree, the higher the deacetylation degree of the chitosan is, the smaller the relative molecular mass is, the higher the solubility is, and the chitosan can be dissolved in dilute acid due to the amino group in the chitosan molecule. The chitosan molecule contains a large amount of active groups, and can generate a series of derivatization reactions, such as Schiff base reaction, graft copolymerization group degradation reaction, complexation reaction and the like. In recent years, the chitosan has certain bacteriostatic and adsorptive capabilities, and the Jianan Yang research shows that the chitosan surface has positive charges which can be combined with negative charges on erythrocytes to promote blood coagulation. According to the research of Fei Liu X and the like, chitosan also has the capacity of inhibiting the synthesis of bacterial RNA and protein, has strong antibacterial capacity, can complete the adsorption of pollutants through electrostatic action due to a large amount of positive charges of chitosan, and is widely applied to the fields of medicinal chemistry, biological treatment, environmental protection, water treatment and the like.

In conclusion, the sewage containing the surfactant enters the water body to damage the normal life activities of aquatic organisms and finally threatens the health of human beings through a food chain and other channels. At present, sewage containing a surfactant generally has six approaches, namely a coagulating sedimentation separation method, an adsorption separation method, a foam separation method, a membrane separation method, a biological oxidation method and a catalytic oxidation method. The coagulating sedimentation separation method has low cost but is easy to generate secondary pollution, the foam separation method has undesirable effect on removing sewage containing high-concentration surfactant, the membrane separation method has good effect but the membrane separation method technology is easy to block and needs to frequently replace the membrane, the treatment period required by the biological catalysis and catalytic oxidation methods is long, the adsorption separation method mainly utilizes the adsorption effect of the filler, the surfactant in the wastewater is adsorbed on the solid surface to be removed, and the cost is low and the effect is good. Therefore, it is important to develop an adsorbent having good adsorption properties. Beta-cyclodextrin and chitosan have a plurality of advantages as natural extracts in nature, but have certain defects, such as easy dissolution, instability and easy hydrolysis when meeting acid; the chitosan has poor solubility, cannot be dissolved under an alkaline condition, and has harsh reaction conditions, if the defects of the chitosan and the alkaline condition can be avoided through modification, the advantages of the chitosan and the alkaline condition can be played, and the effect that 1+1 is more than 2 is realized.

Through the above analysis, the problems and defects of the prior art are as follows:

(1) the linear alkyl benzene sulfonate can enter a natural water body through the ways of discharging industrial wastewater, waste residues, domestic sewage and the like, so that the environment is influenced, and the existence of the linear alkyl benzene sulfonate can be detected in various environment media; due to the special amphipathy and solubilization of the anionic surfactant, the anionic surfactant is very easy to combine with persistent organic pollutants such as polychlorinated biphenyl, polycyclic aromatic hydrocarbon and the like in water, and more complex and profound effects are generated.

(2) When the concentration of the surfactant in the water reaches 1.5mg/L, foam is generated, and the environment attractiveness is influenced; meanwhile, the foam is not easy to disappear, and an isolation layer is easy to generate on the surface of the water body, so that the gas exchange between the water body and the air is seriously influenced, the water body smells, the content of dissolved oxygen is reduced, the living environment of aquatic organisms is further damaged, and the ecological balance is damaged.

(3) The sewage containing the surfactant enters the water body to damage the normal life activities of aquatic organisms and finally threatens the health of human beings through a food chain and other channels; the anionic surfactant can be attached to fish gills of fish or directly adsorbed by fish bodies, has strong biological toxicity to common crucian in water, and has strong inhibiting effect on fish antioxidant enzyme and superoxide dismutase.

(4) In the current approach aiming at the sewage containing the surfactant, the coagulating sedimentation separation method is easy to generate secondary pollution, the foam separation method has poor effect on removing the sewage containing the surfactant with high concentration, the membrane separation method is easy to block and needs to be frequently replaced, and the treatment period required by the biological catalysis and catalytic oxidation methods is long.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a novel beta-cyclodextrin-chitosan cross-linked adsorbing material and a preparation method thereof.

The invention is realized in such a way that a preparation method of a novel beta-cyclodextrin-chitosan crosslinking adsorption material comprises the following steps:

step one, dissolving and regenerating chitosan;

and step two, carrying out beta-cyclodextrin/chitosan acidic condition crosslinking reaction.

Further, in the first step, the chitosan dissolution and regeneration comprises the following steps:

(1) measuring 4mL of glacial acetic acid to prepare 200mL of 2% (w/v) glacial acetic acid solution, weighing 5g of chitosan powder, dissolving in water bath at 60 ℃, and continuously stirring until the solution is clear and transparent;

(2) preparing 100mL of 5% (w/v) emulsifier-petroleum ether continuous phase, dropwise adding 15mL of chitosan solution into 100mL of petroleum ether continuous phase at 50 ℃ by using a disposable dropper, and magnetically stirring for 3 hours at 1000rpm to obtain water-in-oil emulsion;

(3) and (2) placing the emulsion in liquid nitrogen at the temperature of-196 ℃ for low-temperature quenching for 3.5h, preparing 100mL of sodium hydroxide/ethanol aqueous phase conversion fluid precooled in advance after the completion of the low-temperature quenching, carrying out phase inversion regeneration on the chitosan iceball, carrying out mild stirring by using a glass rod to generate white precipitate, centrifugally collecting formed chitosan microspheres, washing the chitosan microspheres by using deionized water and absolute ethyl alcohol in sequence until the supernatant is neutral, and drying the chitosan microspheres in a vacuum freeze dryer.

Further, in the step (1), the glacial acetic acid is analytically pure glacial acetic acid.

Further, in step (2), the emulsifier-petroleum ether continuous phase is mixed with 9.6g S80 and 0.4g T60; wherein, the S80 is Span80, and the T60 is Tween 60.

Further, in the step (3), the concentration of the sodium hydroxide/ethanol aqueous phase conversion liquid is 1% (w/v).

Further, in the second step, the beta-cyclodextrin/chitosan acidic condition crosslinking reaction comprises:

(1) dissolving chitosan in 2% (w/v) glacial acetic acid solution again, and stirring in water bath at 60 deg.C until the solution is clear and transparent; adding 50mL of dimethyl sulfoxide into a reaction system to increase the solubility of chitosan in a water environment and create good reaction conditions for the reaction;

(2) weighing 5g of beta-cyclodextrin, dissolving in water bath at 60 ℃, slowly adding into the chitosan solution, increasing the reaction temperature to 80 ℃, and keeping stirring at high speed for 30min to uniformly mix the beta-cyclodextrin and the chitosan solution;

(3) measuring 12mL of epoxy chloropropane, slowly dropwise adding the epoxy chloropropane into the mixed solution, wherein the solution is in an acidic environment, the epoxy chloropropane is subjected to acidic ring opening, and the chitosan and the beta-cyclodextrin are subjected to crosslinking reaction under an acidic condition;

(4) after the reaction is finished, slowly adding 300mL of 1mol/L sodium hydroxide solution, adjusting the pH of the solution to 10 to precipitate out a reactant, and continuously stirring for 30min to finish the reaction;

(5) obtaining solid precipitate by adopting a suction filtration method, titrating with dilute acid until the pH of the precipitate is neutral, washing the residue with deionized water and absolute ethyl alcohol, and drying in a vacuum drying oven at 60 ℃ to obtain a finished product.

Further, in the step (3), the crosslinking reaction time is controlled to be 2 hours.

The invention also aims to provide a novel beta-cyclodextrin-chitosan crosslinking adsorption material prepared by the preparation method of the novel beta-cyclodextrin-chitosan crosslinking adsorption material.

By combining all the technical schemes, the invention has the advantages and positive effects that: the novel beta-cyclodextrin-chitosan cross-linking adsorption material provided by the invention utilizes beta-cyclodextrin as a raw material, combines the beta-cyclodextrin and chitosan into a novel compound through a cross-linking reaction, improves reaction conditions, optimizes a synthesis path, is used for adsorbing an anionic surfactant in sewage, and discusses feasibility of application.

According to the invention, the processes of micro-emulsification and thermal phase separation are increased through chitosan dissolution and regeneration, crystals are re-destructured, the relative surface area of the adsorption synthetic material is increased, more contact areas are provided for subsequent experiments, the reaction efficiency is improved, and reaction sites are increased. The invention has the advantages that through beta-cyclodextrin/chitosan acidic condition crosslinking reaction, 1, the reaction condition is changed from traditional alkaline condition ring-opening crosslinking to acidic condition ring-opening crosslinking, reactants are crosslinked in the form of solute, the reaction is more sufficient, the yield of the obtained product is high, and the waste of raw materials is reduced; 2. the reaction temperature is properly increased, the activity of the epichlorohydrin is enhanced, and the crosslinking reaction time is shortened; 3. the raw material proportion does not need to be completely accurate, the beta-cyclodextrin self-crosslinking by-product also has good effect of adsorbing the anionic surfactant, and the anti-interference capability is strong in the practical production process, so that the invention has strong popularization and application capability.

The invention improves the synthesis method of cyclodextrin and chitosan to prepare the cyclodextrin-chitosan adsorbent which is used for adsorbing and treating the surfactant in the domestic sewage and obtains good adsorption effect. On the synthesis path, the innovation points of the invention are as follows:

(1) in the traditional method, the reaction raw material chitosan is not pretreated, and the crystallization is easy to agglomerate during the reaction, so that the crystallization effect is poor, and the subsequent reaction is influenced.

The invention optimizes the synthesis path, pretreats the chitosan, increases the specific surface area of the chitosan by using a thermal phase separation method, increases the porosity of the product, provides more contact area for subsequent experiments, improves the reaction efficiency, increases reaction sites, makes the microscopic surface of the adsorbent have more folds, and can contain and adsorb more anionic surfactants. The invention also verifies the product function (the data of the post-attached experiment and the picture of the electron microscope) through a characterization experiment and an adsorption experiment, and obtains the conclusion that the product of the new technical scheme has good adsorption effect, can be repeatedly utilized and has strong popularization and application.

(2) The traditional crosslinking method is a crosslinking reaction under an alkaline condition, but in actual operation, chitosan cannot be dissolved under the alkaline condition, and precipitates are easily and directly separated out under the alkaline condition, so that the crosslinking reaction is only carried out on the surface of the microsphere, the reaction is insufficient, and a large amount of waste is generated. Because the reaction yield of the product is high and the reaction conditions are simple in industrial application, the traditional technology can be completed only in a laboratory, but is difficult to be widely applied and popularized in the industry.

The invention optimizes the technical conditions, utilizes the characteristic that the crosslinking agent epichlorohydrin has oxidation crosslinking capability in acid and alkaline environments at the same time, carries out ring opening reaction under the acid condition, precipitates the product in the alkaline environment, distinguishes the reaction environment from the precipitation environment, crosslinks the reactant in the form of solute, and properly increases the dosage of beta-cyclodextrin, so that the reaction is more complete, the reaction yield is greatly improved, and the waste is reduced; meanwhile, compared with the traditional method, the optimization technology optimizes the proportion of each raw material and the auxiliary solvent, does not need to completely and accurately control the content of the cross-linking agent, has strong interference resistance in actual production, has high yield of cross-linked products obtained after the reaction is finished, and has better adsorption effect on the anionic surfactant by the cyclodextrin self-cross-linked by-products generated by the reaction, so that the precision and the actual requirements can be met even if the production conditions can not strictly meet the laboratory requirements in industrial production, and the fault tolerance rate of the obtained products is higher, therefore, the technical scheme has great practical application value and space.

(3) The reaction temperature of the traditional crosslinking method is usually low (50-60 ℃), and is a certain distance away from the optimal reactive temperature of the crosslinking agent epichlorohydrin.

The invention changes the reaction temperature and the reaction conditions, improves the reaction temperature to 80 ℃, increases the activity of the epichlorohydrin, enables the reaction to reach the balance more quickly and reduces the reaction time; meanwhile, the mixing time of pre-crosslinking and reaction completion is increased, so that the chitosan and the beta-cyclodextrin can be more fully mixed, the solid carrying rate of the raw materials is increased, the precipitated particles are more exquisite, the relative surface area is larger, and the obtained product has a better adsorption effect (shown by the attached experimental data).

According to the invention, through the re-recovery of the adsorbent and the graphical analysis of data, the adsorbent repeatedly used for five times still has a good adsorption effect, the maximum adsorption quantity is not changed greatly, the maximum adsorption quantity can also reach 74.14mg/g, which indicates that the chitosan-cyclodextrin adsorbent has stable properties and is worth being recycled.

Therefore, in the experiment for exploring the adsorption effect, the invention can draw the following conclusions:

(1) when the dosage is controlled to be 45mg, the adsorption efficiency and the adsorption quantity can be taken into consideration, so that the adsorbent can be saved, the adsorption effect can be ensured, the adsorption efficiency can reach 92.8% under the condition, and the adsorption quantity can reach 103.06 mg/g.

(2) In the experiment for researching the reaction time on the adsorption effect, the reaction equilibrium concentration can be reached by controlling the reaction time to be 25min, the adsorption rate can reach 91.7%, the adsorption rate is approximately consistent with that of the previous experiment, the adsorption quantity can reach 103.06mg/g, the time cost can be saved by measuring the adsorption equilibrium time, and the reaction efficiency can be increased.

(3) In an experiment for researching pH on an adsorption effect, the conclusion that the pH is an important condition influencing the adsorption effect is obtained, under the condition that the pH is less than 7, the adsorption efficiency can be stably kept above 80.1%, the adsorption quantity can be kept at 89.00mg/g, under the condition that the pH is more than 7, the adsorption effect is greatly reduced, when the pH value is 11, the adsorption efficiency is reduced to above 42.6%, the adsorption quantity is kept at 47.33mg/g, although the reduction range is large, the adsorption capacity is still certain, the adsorption characteristic of the chitosan-cyclodextrin adsorbent comprises two effects of static effect and enveloping effect, the pH change can be resisted within a certain range, and the adsorption effect is stable.

(4) The adsorbent is recycled, the maximum adsorption capacity can still reach 74.14mg/g after five times of adsorption and desorption, the change range is small, and the adsorbent has the value and the capability of reutilization.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a flow chart of a preparation method of a novel beta cyclodextrin-chitosan cross-linked adsorption material provided by an embodiment of the invention.

Fig. 2 is a schematic view of a beta-cyclodextrin steric structure provided by an embodiment of the present invention.

FIG. 3 is a schematic diagram of the molecular structure of chitosan provided by the embodiment of the present invention.

Fig. 4 is a schematic view of an adsorption effect of the novel beta cyclodextrin-chitosan cross-linked adsorption material provided by the embodiment of the present invention.

FIG. 5 is a scanning electron microscope image at 50 times magnification of three substances provided by an embodiment of the present invention.

FIG. 5(a) is a 50-fold scanning electron microscope image of β -cyclodextrin provided in an example of the present invention.

FIG. 5(b) is a 50-fold scanning electron microscope image of chitosan provided in the example of the present invention.

Fig. 5(c) is a 50-fold scanning electron microscope image of the chitosan-cyclodextrin adsorbent provided in the example of the present invention.

FIG. 6 is a scanning electron microscope image at 200 Xmagnification of three substances provided by an embodiment of the present invention.

FIG. 6(a) is a scanning electron microscope image of beta-cyclodextrin at 200 times magnification provided by an embodiment of the present invention.

FIG. 6(b) is a scanning electron microscope image of chitosan at 200 times magnification provided by the embodiment of the present invention.

Fig. 6(c) is a scanning electron microscope image of chitosan-cyclodextrin adsorbent 200 times provided by the embodiment of the present invention.

FIG. 7 is a scanning electron microscope image at 500 Xmagnification of three substances provided by an embodiment of the present invention.

FIG. 7(a) is a 500-fold scanning electron microscope image of β -cyclodextrin provided in an example of the present invention.

FIG. 7(b) is a 500-fold scanning electron microscope image of chitosan provided in the example of the present invention.

Fig. 7(c) is a 500-fold scanning electron microscope image of the chitosan-cyclodextrin adsorbent provided in the example of the present invention.

FIG. 8 is a scanning electron microscope image at 1000 Xmagnification of three substances provided by an embodiment of the present invention.

FIG. 8(a) is a 1000-fold scanning electron microscope image of β -cyclodextrin provided in an example of the present invention.

FIG. 8(b) is a 1000 XSEM image of chitosan provided in the examples of the present invention.

Fig. 8(c) is a 1000-fold scanning electron microscope image of the chitosan-cyclodextrin adsorbent provided in the example of the present invention.

FIG. 9 is a 2000 Xscanning electron microscope image of three substances provided by an embodiment of the present invention.

FIG. 9(a) is a 2000-fold scanning electron microscope photograph of β -cyclodextrin provided in an embodiment of the present invention.

FIG. 9(b) is a 2000-fold scanning electron microscope image of chitosan provided in the examples of the present invention.

Fig. 9(c) is a 2000-fold scanning electron microscope image of the chitosan-cyclodextrin adsorbent provided in the example of the present invention.

FIG. 10 is a graph of standard anionic surfactant concentration work curves provided by examples of the present invention.

FIG. 11 is a graph of sorbent dosing versus LAS removal rate as provided by an embodiment of the present invention.

FIG. 12 is a graph of sorbent dosing versus maximum sorption capacity Q provided by an embodiment of the present invention.

FIG. 13 is a graph of adsorption time versus LAS adsorption rate provided by an embodiment of the present invention.

FIG. 14 is a graph of adsorption time versus maximum adsorption Q provided by an embodiment of the present invention.

FIG. 15 is a graph of pH versus maximum adsorption Q provided by an example of the present invention.

FIG. 16 is a diagram of a quasi-secondary power model fit provided by an embodiment of the invention.

Figure 17 is a graph of desorption experimental data provided by an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Aiming at the problems in the prior art, the invention provides a novel beta-cyclodextrin-chitosan cross-linked adsorbing material and a preparation method thereof, and the invention is described in detail below with reference to the accompanying drawings.

As shown in fig. 1, a method for preparing a novel beta cyclodextrin-chitosan cross-linked adsorbent material provided by an embodiment of the present invention includes the following steps:

s101, dissolving and regenerating chitosan;

s102, carrying out beta-cyclodextrin/chitosan acidic condition crosslinking reaction.

The technical solution of the present invention is further described below with reference to specific examples.

As shown in figure 2, the beta-cyclodextrin is formed by combining a truncated cone, a large port and a small port, and has hydrophobic inside and hydrophilic outside. The unique stereo cavity structure of cyclodextrin makes it have good function of containing organic molecules, but because of its easy solubility in water, many excellent properties cannot be exerted, and it needs to be modified for application.

As shown in figure 3, chitosan as a natural alkaline high molecular polysaccharide has the advantages of high quality, low price, wide raw material source, degradability and the like, has rich internal groups, contains a large number of active sites such as amino groups, hydroxyl groups and the like, has excellent adsorption, chelating and crosslinking capabilities, can be used as a cationic flocculant in the process of flocculation and precipitation in the water treatment industry, can also be used as a cationic flocculant for generating a chelating reaction with heavy metal ions by utilizing electrostatic action, but has high solubility and adsorption capability influenced by pH and is relatively unstable in action. Therefore, the propylene oxide is adopted to cause the beta-cyclodextrin and molecules such as chitosan to generate cross-linking reaction, the existing reaction conditions are optimized, the beta-cyclodextrin is modified into a compound which is difficult to dissolve in water, the compound is used for adsorbing an anionic surfactant in sewage, and the application possibility is further discussed.

The invention uses beta-cyclodextrin and chitosan as raw materials, and the beta-cyclodextrin and the chitosan are combined into a novel compound through a cross-linking reaction, so as to adsorb an anionic surfactant in sewage and discuss the feasibility of application.

The following is a specific technical scheme step:

the method comprises the following steps: dissolving and regenerating chitosan

Measuring 4mL of glacial acetic acid (analytically pure) to prepare 200mL of 2% (w/v) glacial acetic acid solution, weighing 5g of chitosan powder, dissolving the chitosan powder in a water bath at the temperature of 60 ℃, and continuously stirring until the solution is clear and transparent. 100mL of 5% (w/v) emulsifier-petroleum ether continuous phase (9.6 g of Span80(S80) and 0.4g of Tween60(T60) were mixed) was prepared, 15mL of chitosan solution was added dropwise to 100mL of petroleum ether continuous phase at 50 ℃ using a disposable dropper, and the mixture was magnetically stirred at 1000rpm for 3 hours to obtain a water-in-oil emulsion.

And (2) placing the emulsion in liquid nitrogen at the temperature of-196 ℃ for low-temperature quenching for 3.5h, preparing 100mL (1% (w/v)) of sodium hydroxide/ethanol aqueous phase conversion liquid precooled in advance after the completion of the low-temperature quenching, carrying out phase inversion regeneration on the chitosan iceball, carrying out mild stirring by using a glass rod to generate white precipitates, centrifugally collecting the formed chitosan microspheres, washing the chitosan microspheres by using water and absolute ethyl alcohol in sequence until the supernatant is neutral, and drying the chitosan microspheres in a vacuum freeze dryer.

The method comprises the following steps: the phase separation process of micro-emulsification and heating is increased, crystals are re-deconstructed, the relative surface area of the adsorption synthetic material is increased, more contact areas are provided for subsequent experiments, the reaction efficiency is improved, and reaction sites are increased.

Step two: beta-cyclodextrin/chitosan crosslinking reaction under acidic condition

(1) And (3) dissolving the chitosan obtained in the step one in a 2% (w/v) glacial acetic acid solution again, and stirring in a water bath at the temperature of 60 ℃ until the solution is clear and transparent. And 50mL of dimethyl sulfoxide is added into a reaction system, so that the solubility of the chitosan in a water environment is increased, a good reaction condition is created for the reaction, and the chitosan is prevented from being separated out.

(2) Weighing 5g of beta-cyclodextrin, dissolving in water bath at 60 ℃, slowly adding into the chitosan solution, increasing the reaction temperature to 80 ℃, and keeping high-speed stirring for 30min to uniformly mix the beta-cyclodextrin and the chitosan solution.

(3) Measuring 12mL of epoxy chloropropane, slowly dropwise adding the epoxy chloropropane into the mixed solution, wherein the solution is in an acidic environment, the epoxy chloropropane is subjected to acidic ring opening, the chitosan and the beta-cyclodextrin react under an acidic condition, and the crosslinking reaction time is controlled to be about 2 hours.

(4) And after the reaction is finished, slowly adding 300mL of 1mol/L sodium hydroxide solution, adjusting the pH value of the solution to 10 to precipitate out a reactant, and continuously stirring for 30min to finish the reaction.

The method comprises the following steps: 1. the reaction condition is changed from the traditional alkaline condition ring-opening crosslinking to the acidic condition ring-opening crosslinking, reactants are crosslinked in the form of solute, the reaction is more sufficient, the yield of the obtained product is high, and the waste of raw materials is reduced; 2. the reaction temperature is properly increased, the activity of the epichlorohydrin is enhanced, and the crosslinking reaction time is shortened; 3. the raw material proportion does not need to be completely accurate, the beta-cyclodextrin self-crosslinking by-product also has good effect of adsorbing the anionic surfactant, and the anti-interference capability is strong in the practical production process, so that the invention has strong popularization and application capability.

The adsorption effect is shown in fig. 4.

The technical solution of the present invention will be further described with reference to specific experiments.

(1) Characterization experiment-Scanning Electron Microscope (SEM)

In order to facilitate microstructure comparison, scanning electron microscope characterization experiments are carried out on beta-Cyclodextrin (CD), Chitosan (CD) and a chitosan-cyclodextrin adsorbent (CS-CD) which is a cross-linked product of the beta-Cyclodextrin (CD) and the chitosan-cyclodextrin adsorbent (CS-CD), and longitudinal and transverse comparisons are carried out by respectively amplifying the beta-Cyclodextrin (CD), the Chitosan (CD) and the chitosan-cyclodextrin adsorbent (CS-CD) by 50 times, 200 times, 500 times, 1000 times and 2000 times. Fig. 5(a) is an electron microscope image of beta-cyclodextrin at a magnification of 50 times, fig. 5(b) is an electron microscope image of chitosan at a magnification of 50 times, and fig. 5(c) is an electron microscope image of chitosan cyclodextrin adsorbent (CS-CD) crosslinked by the beta-cyclodextrin at a magnification of 50 times, which can observe that the beta-cyclodextrin has a larger particle size than that of chitosan particles at a magnification of 50 times, and the chitosan has a sharper, smoother, less sharp appearance, and a rougher, but less obvious wrinkle appearance. The chitosan-cyclodextrin adsorbent (CS-CD) can obviously observe surface unevenness and has a rich fold structure. The chitosan-cyclodextrin adsorbent has different particle sizes, and is judged to be caused by insufficient uniformity in particle grinding. The particle size and the surface structure of three solid particles are preliminarily observed by a 50-time electron microscope image, and the microscopic surface cannot be further analyzed, so that more detailed observation can be carried out by means of larger magnification.

Fig. 6(a) is an electron micrograph of β -cyclodextrin at a magnification of 200 times, fig. 6(b) is an electron micrograph of chitosan at a magnification of 200 times, fig. 6(c) is an electron micrograph of chitosan-cyclodextrin adsorbent (CS-CD) which is a product of crosslinking between both, at a magnification of 200 times, fig. 7(a) is an electron micrograph of β -cyclodextrin at a magnification of 500 times, fig. 7(b) is an electron micrograph of chitosan at a magnification of 500 times, fig. 7(c) is an electron micrograph of chitosan-cyclodextrin adsorbent (CS-CD) which is a product of crosslinking between both, at a magnification of 500 times, and fig. 7(c) is an electron micrograph of chitosan-cyclodextrin adsorbent (CS-CD) which is a product of crosslinking between both, at a magnification of 500 times, the results of 200 times of the electron micrographs being similar to the results of the 500 times of the electron micrographs and thus being compared in the same dimension. The beta-cyclodextrin adsorbent has the advantages that the beta-cyclodextrin surface structure is clearer under an electron microscope with the magnification of 200 times and 500 times, the surface is smoother, no obvious pore structure exists, the presumed surface area is smaller, the surface of chitosan is clearer and smoother, the particle size of partial particles can reach the nanometer level under the scale, the appearance of the chitosan cyclodextrin adsorbent is greatly different from that of two raw materials under the magnification of 200 times and 500 times, obvious level folds can be observed, the presumed adsorption sites are greatly increased after cross-linking reaction, the folds are more dense through scale analysis and calculation, the distance between each fold and the adjacent folds can reach the nanometer level, and the expected reaction result is more met. Fig. 8(a) is an electron microscope image of β -cyclodextrin at a magnification of 1000 times, fig. 8(b) is an electron microscope image of chitosan at a magnification of 1000 times, and fig. 8(c) is an electron microscope image of chitosan cyclodextrin adsorbent (CS-CD) crosslinked with both at a magnification of 1000 times, where the microstructure of the particles is observed more clearly at a magnification of 1000 times, and the β -cyclodextrin has a very flat surface, no pore structure, strong dullness, a relatively small specific surface area, and an insufficient adsorption performance. Chitosan can be observed to have certain wrinkles under the scale of 1000 times amplification, and more attachment points are provided for adsorbing substances. The appearance of the chitosan cyclodextrin adsorbent is completely different from that of the chitosan cyclodextrin adsorbent, the synthesized product has clear appearance, extremely many folds and completely exposed particle interior, and the synthesis reaction can be fully presumed to have good adsorption effect.

Fig. 9(a) is an electron microscope image of β -cyclodextrin at a magnification of 2000 times, fig. 9(b) is an electron microscope image of chitosan at a magnification of 2000 times, fig. 9(c) is an electron microscope image of chitosan cyclodextrin adsorbent (CS-CD) which is a product of cross-linking between the two, at a magnification of 2000 times, it is evident that the surface of β -cyclodextrin is smooth and smooth, has no pore structure, has a relatively small specific surface area, and is presumed that internal molecular advantages cannot be exerted during the related reaction, and the contact area is small, at 1000 times and 2000 times. The surface structure of the chitosan is similar to that of beta cyclodextrin, no obvious pore structure exists, certain wrinkles can be observed on the surface, and a small amount of specific surface area is increased to a certain degree. The synthesized chitosan-cyclodextrin adsorbent has a large number of pore structures and a large specific surface area, and the analysis is performed in the reaction process due to the good crystal restructuring process and the correct selection of the cross-linking agent, so that the components in the beta-cyclodextrin particles and the components in the chitosan particles are fully cross-linked, the cross-linking degree is high, the etching effect is good, more contact surfaces are provided for subsequent adsorption experiments, and the adsorption balance time can be greatly reduced.

(2) Adsorption experiments

1. Background and principles of the experiment

The main active ingredient of the synthetic detergent is generally anionic surfactant, wherein linear alkyl benzene sodium sulfonate (LAS) is the most widely used, LAS is used as a standard substance in experiments, the average carbon number of the synthetic detergent is 12, the alkyl carbon chain is between C10 and C13, and the average molecular weight of the synthetic detergent is 344.4. According to the determination of the anionic surfactant in the national standard water, namely methylene blue spectrophotometry (GB7494-37), the anionic surfactant reacts with cationic dye methylene blue to generate blue methylene blue active substance, namely MBAS. The substance has a direct proportion relationship between the chroma and the concentration after being extracted by chloroform, the absorbance of the substance can be measured by adopting a spectrophotometry method under the wavelength of 652nm, a cuvette with the thickness of 10mm is used, and when the volume of a reagent is 100mL, the detection limit is 0.05 mg/L-2.0 mg/L LAS.

2. Early preparation

(1) Preparation of sodium Linear alkyl benzene sulfonate stock solution

0.100g of sodium Linear Alkylbenzene Sulfonate (LAS) standard was weighed to 0.001g using an electronic balance. A100 mL clean beaker was taken, the weighed standard was dissolved in 50mL DI water in a fume hood, quickly transferred to a 100mL volumetric flask, diluted and mixed well to give a 1g/L solution of sodium linear alkylbenzene sulfonate, which was stored in a 4 ℃ refrigerator.

(2) Preparing standard solution of sodium linear alkyl benzene sulfonate

Accurately sucking 10.00mL of linear alkyl benzene sodium sulfonate stock solution by a pipette, transferring the stock solution into a clean volumetric flask with the volume of 1000mL, diluting the stock solution with DI water to accurately fix the volume to 1000mL to obtain a linear alkyl benzene sodium sulfonate solution with the concentration of 10mg/L, and preparing and using the linear alkyl benzene sodium sulfonate solution on the same day.

(3) Preparing methylene blue solution

57.5g of sodium dihydrogen phosphate dihydrate (NaH) was accurately weighed using an electronic balance₂PO₄·2H₂O), dissolving in 300mL DI water in a clean beaker with the specification of 500mL, slowly adding 6.8mL concentrated sulfuric acid along the wall of the beaker, shaking up, and cooling to room temperatureAnd (3) warm, accurately weighing 30mg of methylene blue (indicator grade) by using an electronic balance, dissolving the methylene blue by using 50mL of DI water, transferring the solution and the solution into a 1000mL brown volumetric flask, diluting to a constant volume until the solution is marked, uniformly mixing, and storing in a dark place to prevent decomposition.

(4) Preparing phenolphthalein indicator solution

Accurately weighing 1.0g of phenolphthalein by an electronic balance, dissolving in 50mL of absolute ethanol in a 100mL clean beaker, slowly adding 50mL of DI water while stirring, filtering off the precipitate, transferring and storing in a reagent bottle.

3. Preliminary experiments

The sample is diluted by 1, 2, 5, 10 and 100 times respectively for measurement, whether the sample is within the detection limit is observed, and the proper dilution factor is determined.

(1) Drawing of standard curve

Transferring 0, 1.00, 2.00, 3.00, 4.00 and 5.00mL of linear alkyl sodium benzenesulfonate standard solution into a 25.0mL colorimetric tube, accurately diluting to a marked line, wherein the concentration is 0, 0.4, 0.8, 1.2, 1.6 and 2.0mg/L respectively, shaking uniformly, measuring the light absorption value and recording.

(2) Measurement of Absorbance

Adding phenolphthalein serving as an indicator into the sample, dropwise adding a sodium hydroxide solution with the concentration of 1mol/L until the water is peach-colored, and dropwise adding 0.5mol/L sulfuric acid until the red color disappears. Adding 25mL of methylene blue solution into the sample, shaking uniformly, adding 10mL of chloroform, transferring the solvent to a separating funnel, shaking for 30s, discharging air, adding a small amount of isopropanol to eliminate emulsification, standing for layering, placing the chloroform layer into a second separating funnel which is previously filled with 50mL of washing solution, washing the first separating funnel with a plurality of drops of chloroform, and repeatedly extracting for three times, wherein 10mL of chloroform is used each time. All chloroform was pooled in a second separatory funnel, shaken for 30s, allowed to stand for layering, added to a 50.0mL cuvette, and calibrated by addition of a reticle. The cuvette was washed three times and the samples were measured at 652.0nm with chloroform as reference and the absorbance recorded.

4. Adsorption experiments

(1) Influence of the amount of addition on the amount of adsorption

A50 mg/L LAS aqueous solution was prepared, and 2mL of the solution was diluted to 100 mL. 15mg, 30mg, 45mg, 60mg, 75mg and 100mg of the modified microspheres (see 3.3.4 in the following description) were added to the mixture, the mixture was placed in a beaker, the mixture was reacted for 2 hours with shaking in a constant temperature oscillator at 25 ℃, and the absorbance of the supernatant was measured after magnetic separation. And respectively calculating the removal rate and the adsorption capacity of the modified microspheres to the surfactant under different adding amount conditions according to the following formula.

Wherein eta is the removal rate of anionic surfactant, Q_eThe adsorption amount of the modified microspheres to LAS in adsorption balance is shown; c₀Initial concentration of surfactant, mg/L; c_eThe concentration of the surfactant remaining in the solution after adsorption (the same applies hereinafter).

(2) Determination of adsorption equilibrium time

A50 mg/L LAS aqueous solution was prepared, and 2mL of the solution was diluted to 100 mL. Adding 45mg of modified adsorbent, placing in a beaker, oscillating and reacting in a constant temperature oscillator at 25 ℃, taking supernatant liquid every 10 minutes to measure absorbance, and taking 10 samples.

Wherein eta is the removal rate of anionic surfactant, Q_eThe adsorption amount of the modified microspheres to LAS in adsorption balance is shown; c₀Initial concentration of surfactant, mg/L; c_eIs the concentration of surfactant remaining in the solution after adsorption.

(3) Test for influence of initial pH value on adsorption quantity

Prepare 50mg/L LAS solution, 2mL, dilute to 100 mL. Adjusting pH value to 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0 and 11.0 with dilute HCl solution, adding 20mg modified microsphere, placing in a beaker, oscillating and reacting for 2 hours in a constant temperature oscillator at 20 ℃, and taking supernatant after magnetic separation to measure absorbance. And respectively calculating the removal rate and the adsorption capacity of the modified microspheres to the surfactant under different initial pH values according to the reaction formula.

5. Analysis of experiments

(1) Experimental data processing

Standard working curve

The absorbance measurements for the standard curve solution series are shown in Table 1.

TABLE 1 LAS Standard working curves

Fitting was performed according to the data in table 1, and a fitted curve was plotted with the anionic surfactant concentration as abscissa and the absorbance as ordinate, as shown in fig. 10.

From fig. 10, the fitting equation of the standard working curve is that y is 0.4879x +0.0022, and R2 is 0.9998, so the fitting effect is good. The wastewater dye concentration calculation formula is as follows:

wherein, A is solution absorbance; c-anionic surfactant concentration.

(II) influence of addition amount on adsorption effect

According to the determination result, the absorbances of the water samples under different adding masses of the adsorbents and the corresponding concentrations of the surfactants are obtained, the removal rate and the adsorption quantity of the anionic surfactants in the water samples by the chitosan-cyclodextrin adsorbents are calculated, and the removal rate and the adsorption quantity are arranged into a table 2 and are plotted to obtain a graph 11 and a graph 12.

TABLE 2 influence of LAS dosage on adsorption Effect

The calculation process is as follows, taking the dosage of 30mg as an example:

the other calculations are the same as above.

(III) influence of adsorption time on adsorption efficiency

As can be seen from the data in Table 2, the adsorption rate is continuously increased and gradually becomes stable with the increase of the added mass, but the adsorption amount Q is reduced with the increase of the added mass, so that the factors of the adsorption amount and the adsorption rate are comprehensively considered, 45mg of the added mass is selected as a fixed amount, the influence of the adsorption time on the adsorption efficiency is researched, and the data is collated to obtain Table 3, a graph 13 and a graph 14.

TABLE 3 influence of adsorption time on the adsorption Effect

The calculation process is as follows, taking the adding amount as 20min as an example:

the other calculations are the same as above.

(IV) influence of pH on the adsorption Effect

Set 11 different pH ranges to explore the effect of pH change on adsorption effect, collate the data to obtain table 4 and figure 15.

TABLE 4 influence of pH on the adsorption Effect

The calculation is as follows, taking the pH as an example:

the other calculations are the same as above.

(V) Desorption experiment

The chitosan cyclodextrin adsorbent with saturated adsorption is obtained by recycling the adsorbent again, a suction filtration method is used for obtaining the chitosan cyclodextrin adsorbent, the chitosan cyclodextrin adsorbent is washed by ethanol and deionized water, the chitosan cyclodextrin adsorbent is soaked for 12 hours by hydrochloric acid with the concentration of 1mol/L, the chitosan cyclodextrin adsorbent is washed by deionized water and ethanol again, the pH value of the adsorbent is adjusted to be 7, the chitosan cyclodextrin adsorbent is placed into a drying oven with the temperature of 60 ℃ for drying and regenerating the adsorbent, the experiment is simulated again and repeated (the reaction time is controlled for 40min), and the data are collated to obtain the table 5.

TABLE 5 Effect of regenerated adsorbent on adsorption Effect

(2) Analysis of Experimental data

The fitting equation of the standard working curve is that y is 0.4879x +0.0022, and R2 is 0.9998, so that the fitting effect is good. In an experiment for researching the influence of the addition amount on the adsorption amount, the adsorption rate can be observed to continuously increase along with the increase of the addition quality of the adsorbent until the saturated adsorption rate is reached and cannot be increased. Therefore, when the possibility of application of the adsorbent is researched, the adding amount cannot be increased or reduced blindly, and it is necessary to find a balanced adsorption adding amount, according to experimental data, when the adding amount is 75mg, the adsorption amount reaches the maximum of 96.6%, the adsorption efficiency is the most good, but the adsorption effect is poor, the adsorption amount is only 64.37mg/g, analysis shows that the equilibrium concentration of the solution is low at this time, most of the anionic surfactant in the solution is completely adsorbed, the average adsorption amount is reduced due to the excessive adding quality, waste is generated, and therefore the adding quality needs to be reduced properly. When the adding amount is 15mg, the adsorption effect is the best, the maximum adsorption amount can reach 149.27mg/g, but the equilibrium concentration is higher, so that the adsorption efficiency is lower, namely 44.8%, and the analysis shows that the solution concentration is higher and the adding amount is insufficient, so that the adding quality needs to be properly increased. Comprehensive analysis shows that when the adding amount is controlled to be 45mg, the adsorption efficiency is 92.8%, when the adsorption amount reaches 103.06mg/g, most of the anionic surfactant in the solution is absorbed, the adsorption amount is large, the adsorption efficiency is considered, the adsorption amount can be ensured, and therefore the adding amount of 45mg is used as a fixed amount for controlling the adsorption efficiency experiment by subsequently researching the reaction time.

Secondly, in the experiment for researching the reaction time on the adsorption effect, the detection is carried out on the residual anionic surfactant in the solution every 10 minutes, and the adsorption rate is taken as the ordinate, the adsorption time is taken as the abscissa, the adsorption quantity is taken as the ordinate, and the adsorption time is taken as the abscissa. It can be observed that the solution residual concentration is decreased very fast and the adsorption rate is increased very fast in the interval of 0-10 min, the adsorption speed is reduced and stably and slowly increased in the interval of 10-20 min, the adsorption reaches balance in about 30min, the subsequent adsorption rate is not changed obviously, and the slight fluctuation of individual data may be caused by a certain deviation in the sampling or detection link. Therefore, in subsequent experiments, the reaction time is controlled to be 30min, so that the time is saved, and the efficiency is increased.

In the experiment for researching the pH value on the adsorption effect, the solution adsorption effect is greatly changed along with the pH value, the adsorption effect of the adsorbent is good under an acidic condition, and the adsorption effect of the adsorbent is inhibited under an alkaline condition. This is because as the pH of the solution changes, H in the solution⁺With OH^-The amount of (a) will affect the activity of the reaction site. The adsorbent is a chitosan-cyclodextrin adsorbent, chitosan can be slightly ionized and positively charged in water, organic pollutants can be adsorbed by electrostatic action in an acidic environment, and OH in solution can be adsorbed along with the change of pH^-Increased content of OH^-Competition with anionic surfactant can be generated, effective adsorption sites are reduced, but it can be found that pH cannot become a decisive factor of adsorption, 60% of adsorption performance is still maintained in an alkaline environment, the adsorption mechanism of cyclodextrin is inclusion effect due to the special structure of cyclodextrin, and electrostatic adsorption of anionic surfactant is not completely relied on

Studies by Fenyvesi et al, adsorption of anionic organics by CyclodextrinsThe effect is very good, and the annular structure has a large number of adsorption sites and strong inclusion capacity. Therefore, the chitosan-cyclodextrin adsorbent still has certain adsorption effect on anionic organic compounds in an alkaline environment.

And fourthly, fitting the data in the table 3 according to a first-order kinetic equation to find that the fitting effect is poor, so that fitting is carried out according to a quasi-second-order dynamic model in the table 3, and the graph 16 is drawn.

From fig. 16, it can be seen that the reaction conforms to the quasi-secondary dynamic model, which has the formula:

wherein Q is_t: adsorption capacity, mg/g; t: adsorption time t, min; q_e: equilibrium adsorption capacity, mg/g; k is a radical of₂: adsorption constant.

Combining to obtain the relation: y is 0.0094x + 0.012; the contrast ratio can be used to determine Q_em＝106.38mg/g，k＝7.36×10^-3，R²＝0.993。

Desorption experiment (see FIG. 17)

TABLE 6 influence of regenerated adsorbent on adsorption Effect

Through the recovery of the adsorbent again and the data mapping analysis, the adsorbent which is repeatedly used for five times still has a good adsorption effect, the maximum adsorption quantity is not changed greatly, the maximum adsorption quantity can also reach 74.14mg/g, and the chitosan-cyclodextrin adsorbent is stable in property and is worthy of being recovered and repeatedly used.

Therefore, in the experiment for exploring the adsorption effect,

In the description of the present invention, "a plurality" means two or more unless otherwise specified; the terms "upper", "lower", "left", "right", "inner", "outer", "front", "rear", "head", "tail", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be construed as limiting the invention. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.

Claims

1. A preparation method of a novel beta-cyclodextrin-chitosan cross-linked adsorption material is characterized by comprising the following steps:

step one, dissolving and regenerating chitosan;

2. The method for preparing the novel beta-cyclodextrin-chitosan cross-linked adsorbent material according to claim 1, wherein in the first step, the chitosan dissolution and regeneration comprises the following steps:

3. The method for preparing the novel beta-cyclodextrin-chitosan cross-linked adsorbent material according to claim 2, wherein in the step (1), the glacial acetic acid is analytically pure glacial acetic acid.

4. The method for preparing a novel beta-cyclodextrin-chitosan cross-linked adsorbent material according to claim 2, wherein in the step (2), the emulsifier-petroleum ether continuous phase is mixed with 9.6g S80 and 0.4g T60; wherein, the S80 is Span80, and the T60 is Tween 60.

5. The method for preparing a novel beta-cyclodextrin-chitosan cross-linked adsorbent material according to claim 2, wherein in the step (3), the concentration of the aqueous sodium hydroxide/ethanol phase transition liquid is 1% (w/v).

6. The method for preparing the novel beta-cyclodextrin-chitosan cross-linked adsorbent material according to claim 1, wherein in the second step, the beta-cyclodextrin/chitosan acidic condition cross-linking reaction comprises:

(1) dissolving chitosan in 2% (w/v) glacial acetic acid solution again, and stirring in water bath at 60 deg.C until the solution is clear and transparent; adding 50mL of dimethyl s sulfoxide into a reaction system to increase the solubility of chitosan in a water environment and create good reaction conditions for the reaction;

7. The method for preparing the novel beta-cyclodextrin-chitosan cross-linked adsorbent material according to claim 6, wherein in the step (3), the cross-linking reaction time is controlled to be 2 hours.

8. A novel beta cyclodextrin-chitosan cross-linked adsorbing material prepared by the preparation method of the novel beta cyclodextrin-chitosan cross-linked adsorbing material as claimed in any one of claims 1 to 7.