CN107233868B - Preparation and application of color-changing fiber IAHF-PAR - Google Patents

Abstract

The invention discloses a synthesis method of chelating fiber IAHF, a synthesis method of IAHF-PAR color-changing fiber and application thereof, wherein the synthesis method of chelating fiber IAHF comprises the following steps: the acrylic fiber chelating fiber IAHF is synthesized by taking acrylic fiber as a matrix and isoniazid as a ligand under the protection of nitrogen. Placing acrylic fiber chelate fibers IAHF and PAR into formaldehyde water solution, stirring under nitrogen protection, heating and refluxing for 2-6h at 70 deg.C^oAnd C, after the stirring reaction is finished, washing with warm water, and drying to constant weight to obtain the color-developing fiber IAHF-PAR. The acrylic fiber chelating fiber IAHF synthesized by the invention has heavy metal ion adsorption capacity, strong selective adsorption on mercury ions, large adsorption capacity and high adsorption speed, and the chromogenic fiber IAHF-PAR can be suitable for detection in different environments and can be prepared into chromogenic materials in different forms.

Description

Preparation and application of color-changing fiber IAHF-PAR

Technical Field

The invention belongs to the technical field of functional fiber synthesis, and particularly relates to a synthesis method of chelating fiber (IAHF) with efficient selective adsorption performance, a synthesis method of IAHF-PAR color-changing fiber and application.

Background

The high-speed development of the scientific and technological level and economy promotes the industrial modernization process of China, brings convenient urban life and considerable economic benefit, brings serious environmental pollution problems, and destroys the ecological environment on which people live. The pollution caused by the heavy metal is a serious test facing the food quality safety. The production and processing processes of agricultural products are particularly easily influenced by the external environment, so that heavy metal pollution in the environment easily leads to the standard exceeding of heavy metal in the agricultural products. Therefore, the safety of the heavy metals in agricultural products needs to be evaluated and detected. The large number of samples to be detected and the low detection threshold are basic characteristics of heavy metal detection in agricultural products, so that the establishment of the detection method with high detection speed and sensitive reaction has great research significance.

At present, most of the common methods for rapidly detecting heavy metals are chemical color development methods, and a plurality of various solid heavy metal sensor materials and color development test paper have been developed and developed. However, the production cost of the sensing material is not low, most of the sensing materials are prepared by using a film and a nano material as a matrix, the preparation steps are multiple, the regeneration performance is poor, and the large-scale popularization and application in the market are difficult. The test paper method has many problems such as high heavy metal detection threshold value and insufficient accuracy, and the most important point is that most test paper does not have the specific adsorption capacity of single metal ions. Polyacrylonitrile fiber is an excellent modified material, and is a hot spot for research in high molecular materials. Therefore, before the matrix fiber is connected with different color developing agents, the fiber must be modified, so that the fiber can rapidly and specifically respond to heavy metal ions, and the defects of low color developing speed, non-specific color developing and the like of the conventional test paper are overcome. After chemical modification, the lone pair electrons on the functional group of the polyacrylonitrile chelating fiber coordinate with metal ions to firmly chelate the metal ions to the fiber. The polyacrylonitrile fiber is used as a modified matrix material, and the organic heterocyclic ligand with strong chelation effect on metal ions is grafted to the active groups of the fiber to prepare the novel chelate fiber capable of rapidly adsorbing the heavy metal ions.

Toxic heavy metal mercury in the agricultural products can enter a human body through a food chain and is enriched through biological action, and the mercury poisoning phenomenon is easy to occur in species on the upper layer of the food chain. Humans, as the top of the food chain, should have strict control over mercury exposure. The toxicity of mercury is very strong, and the human health can be endangered by small inhalation, and serious mercury poisoning usually shows vomiting, gum swelling and inflammation, and heart function decline. The action mechanism is that the protease is combined with sulfhydryl of protease in human body, which inhibits the activity of enzyme, hinders the normal metabolism of cells and destroys the function of human body. Accumulation in the kidney can cause gastroenteritis and mercury poisoning nephropathy; in brain tissue, can damage the central nervous system of humans. If the food polluted by mercury is eaten, the food causes great damage to human bodies.

At present, common methods for analyzing and detecting mercury ions in agricultural products include cold atomic absorption spectrometry, hydride generation-atomic fluorescence spectrometry, inductively coupled plasma emission spectrometry, and the like. Although the analysis methods can accurately detect the content of mercury in the sample, the analysis methods have the defects of high use cost, complicated preparation work in the early detection stage and the like, and cannot meet the requirement of rapid detection of a large number of samples. Therefore, it is important to find a rapid detection method with low cost, portability, and certain sensitivity and accuracy.

Disclosure of Invention

The invention aims to solve the technical problems in the prior art and provides an acrylic fiber chelating fiber IAHF and a synthesis method thereof.

Meanwhile, the synthesis and the application of the novel acrylic fiber chromogenic fiber IAHF-PAR are provided, and the mercury in agricultural products can be rapidly detected.

In order to solve the technical problems, the invention provides the following technical scheme:

the synthetic method of the acrylic fiber chelating fiber IAHF comprises the following steps:

(1) taking acrylic fiber (PAN) as a matrix, and soaking and swelling the acrylic fiber in a reaction solvent toluene for 6 hours;

(2) adding a ligand into the product obtained in the step (1), and stirring at 40-100 ℃ under the protection of nitrogen until the reaction is finished, wherein the ligand is isoniazid, and the molar ratio of a matrix to the ligand is 1: 2-1: 6;

(3) and (3) washing the obtained product in the step (2) with a reaction solvent toluene to be colorless, washing, and drying to constant weight to obtain the acrylic fiber chelating fiber IAHF.

As an improvement of the synthetic method of the acrylic fiber chelating fiber IAHF, in the step (1), the dosage ratio of the acrylic fiber to the toluene is 0.10-0.20g acrylic fiber/30 ml toluene.

As an improvement of the synthetic method of the acrylic fiber chelating fiber IAHF, the molar ratio of the acrylic fiber to the isoniazid is preferably 1: 3.

As an improvement of the synthetic method of the acrylic fiber chelating fiber IAHF, the rinsing in the step (3) is as follows: washing with anhydrous alcohol, acetone and diethyl ether sequentially.

As an improvement of the synthesis method of the acrylic chelating fiber IAHF, the reaction temperature in the step (2) is preferably 100 ℃.

The synthetic fiber obtained by the invention is novel acrylic fiber chelating fiber IAHF, and the content of the functional group and the conversion rate of the functional group of the synthetic fiber can be calculated by formulas (1) and (2) according to the content of N in the product:

the content of the functional group and the conversion rate of the functional group of the synthetic fiber can also be calculated according to the S content by the formulas (3) and (4):

wherein, F₀Is the content of the functional group of the acrylic fiber (CN mmol/g), F_cIs a function of synthetic fibresEnergy radical content (mmol/g), x is functional radical conversion rate, S_cFor synthetic fibre sulphur content (%), N₀Is the nitrogen content (%) of the acrylic fiber, N_cIs the nitrogen content (%) of the synthetic fiber, M_LIs the molar mass (mol/g) of the ligand, n_SIs the number of sulfur atoms in the ligand molecule, n_NThe number of nitrogen atoms in the ligand molecule.

The preparation method for preparing the PAR color developing fiber by adopting the acrylic fiber chelating fiber IAHF comprises the steps of putting the acrylic fiber chelating fiber IAHF and PAR into a formaldehyde water solution, stirring, heating and refluxing for 2-6h under the protection of nitrogen, stirring and reacting at 70 ℃, washing with warm water, and drying to constant weight to obtain the color developing fiber IAHF-PAR;

as an improvement of the synthesis method of the color-developing fiber IAHF-PAR, the dosage ratio of the IAHF, the PAR, water and formaldehyde is preferably as follows: 0.5g IAHF/0.3g PAR/35ml water/5 ml formaldehyde.

The chromogenic fiber IAHF-PAR prepared by the synthetic method disclosed by the invention is applied to the rapid detection of heavy metals in agricultural products. The heavy metal is Hg²⁺。

The application of the acrylic fiber chromogenic fiber IAHF-PAR in the rapid detection of Hg (II) in agricultural products comprises the following steps:

(1) pretreatment of a sample to be detected: the method comprises the steps of (1) obtaining a solution to be detected after a sample to be detected is smashed, digested and subjected to constant volume; the sample to be detected is a marine product;

(2) putting the digested agricultural product solution into a clean and transparent colorimetric tube, adjusting the pH value of the solution to be 7.0, immersing the chromogenic fiber IAHF-PAR in the solution to be detected for 2s, taking out the solution, spin-drying, converting the color information of the fiber color into RGB value after the chromogenic experiment is finished, and comparing the RGB value with a standard colorimetric card to obtain the content of Hg (II) in the agricultural product.

The synthetic method of the acrylic fiber chelating fiber IAHF and the chromogenic fiber IAHF-PAR have the following advantages:

(1) the obtained acrylic fiber chelate fiber IAHF and acrylic fiber chromogenic fiber IAHF-PAR have the characteristics of wide raw material source, low price, easy preparation and the like;

(2) the acrylic fiber chelating fiber IAHF synthesized by the method has heavy metal ion adsorption capacity, wherein the acrylic fiber chelating fiber IAHF has strong selective adsorption on mercury ions, large adsorption capacity and high adsorption speed;

(3) the elution efficiency of the acrylic fiber chelate fiber IAHF synthesized by the invention is high;

(4) the synthesis method provided by the invention is simple to operate and high in yield;

(5) the acrylic fiber IAHF-PAR synthesized by the method can be suitable for detection in different environments and can be prepared into color developing materials in different forms;

(6) the acrylic fiber IAHF-PAR synthesized by the method has obvious color selectivity on mercury ions, and can be used for detecting the mercury content in agricultural products;

(7) the heavy metal detection application provided by the invention effectively reduces the detection cost, simplifies the detection steps, and can be applied to detection and analysis of trace mercury in food.

Drawings

FIG. 1 is a chart showing the infrared spectrum of IAHF prepared in example 1;

FIG. 2 shows the effect of different reaction temperatures on the conversion of IAHF functional groups;

FIG. 3 shows the effect of different reaction molar ratios on the conversion of IAHF functional groups;

FIG. 4 shows the adsorption amounts of six heavy metal ions by IAHF at different pH values;

FIG. 5 is a graph showing the adsorption of metal ions of Hg (II) by IAHF at different temperatures as a function of time;

FIG. 6 is a schematic diagram showing the color developing effect of the color developing fiber IAHF-PAR on different metals;

FIG. 7 shows a schematic representation of the color development effect of the color-developing fibers IAHF-PAR on Hg (II) at different pH values.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Example 1

(1) Accurately weighing 0.15g of parent acrylic fiber (PAN) and placing the parent acrylic fiber in a 100ml three-necked bottle, adding 30ml of reaction solvent toluene, and soaking and swelling for 6 hours;

(2) adding ligand isoniazid into a three-necked bottle, introducing nitrogen, stirring at the stirring speed of 150rpm for 1-2h at normal temperature, and stirring at 100 ℃ until the reaction is finished after the air in the bottle is exhausted (i.e. under the protection of nitrogen), wherein the molar ratio of the acrylic fiber (matrix) to the isoniazid (ligand) is 1: 3;

(3) and (3) after the reaction in the step (2) is finished, washing the obtained product in the step (2) by using a reaction solvent toluene until the obtained product is colorless, then washing the obtained product by using absolute ethyl alcohol, acetone and diethyl ether for a plurality of times in sequence, and drying the obtained product in vacuum at the temperature of 50 ℃ until the weight of the obtained product is constant to obtain the acrylic chelating fiber IAHF.

FIG. 1 shows the IR spectrum of IAHF prepared in example 1 at 2243cm^‐1The peak is the stretching vibration absorption peak of the cyano CN bond in the acrylic fiber, and 2869cm^‐1And 2930cm^‐1Respectively represents the symmetric and asymmetric stretching vibration peaks of the molecular structure methylene-CH 2 of the polyacrylonitrile fiber, and the analysis of the figure shows that the IAH modification reduces the cyano group consumption due to the reaction, the absorption peak of C.ident.N bond near 2243cm-1 in the matrix of the acrylic fiber is obviously weakened, 3297cm^-1Is the absorption peak of primary amine in ligand IAH; 1666cm in IAHF^-1、1628cm^-1And 1238cm^-1The presence of a heterocyclic ring is indicated by the absorption peak of (a). Wherein, 1666cm^-1Is the stretching vibration peak of C ═ O in the ligand; 1628cm^-1Is a C ═ N conjugated stretching vibration peak on the heterocycle; 1238cm^-1The reaction path and IAHF structure of the synthetic reaction of the acrylic fiber chelating fiber IAHF are obtained by applying an infrared spectrum technical method and comparing and analyzing the acrylic fibers before and after the reaction, wherein the nearby absorption peak is a stretching vibration peak of a C-N bond, and the reaction path and the IAHF structure of the synthetic reaction of the acrylic fiber chelating fiber IAHF are as follows:

comparative examples 1 to 1

The reaction solvent in example 1 was changed to water and n-butanol, and the rest was the same as in example 1.

Specifically, in the present embodiment, the acrylic fiber is used as a matrix, and acrylonitrile in the acrylic fiber has an irregular spatial three-dimensional structure due to interaction of cyano groups with a large polarity, so that the acting force between molecules of the acrylic fiber is large. The organic reaction solvent has swelling effect on many high molecular materials, and is favorable for chemical modification. Therefore, the results of comparing the swelling property and solubility of the acrylic fiber in the reaction solvent and the boiling point and polarity of the solvent with water, toluene and n-butanol as the reaction solvent are shown in table 1.

TABLE 1 elemental analysis of IAHF in three different solvents

According to Table 1, by comprehensively comparing the nitrogen content of IAHF, isoniazid has higher functional group conversion rate in toluene.

Comparative examples 1 to 2

The reaction temperature in step (2) of example 1 was changed to 40 ℃, 60 ℃ and 80 ℃ and the stirring was carried out, and the reaction temperature was the same as that in example 1, thereby examining the influence of the reaction temperature on the conversion rate of the IAHF functional group.

Specifically, the mobility of the polymer material has different forms, and most organic polymer materials have four physical states: glassy state, viscoelastic state, high elastic state, viscous state, the transition between high elastic state and glassy state is called glass transition. Below the glass transition temperature, the polymer is in a glass state, and the molecular chain and the chain segment are not active, which is not beneficial to the chemical modification. The glass transition temperature of the acrylic fiber is 80-100 ℃. Therefore, when the reaction temperature is higher than the glass transition temperature of acrylon, the reaction can be smoothly carried out. On the contrary, the reaction temperature is too high, and the fiber structure is easily damaged. The boiling points of the solvents of water, toluene and n-butanol are respectively 100 ℃, 110.6 ℃ and 117.7 ℃, and the boiling point of the ligand is 186 ℃. Considering the melting point of the solvent and the ligand, the reaction temperature range of the IAHF in the toluene is selected to be 40-100 ℃, as shown in figure 2, the conversion rate of the functional group is increased along with the temperature rise in the reaction temperature range, so the optimal synthesis temperature of the IAHF is 100 ℃.

Comparative examples 1 to 3

The effect of the molar ratio of the precursor to the ligand on the conversion of the IAHF functional group was examined by changing the molar ratio of the precursor to the ligand in step (2) of example 1 to 1:2, 1:4, 1:5, 1:6, and the rest of the same procedure as in example 1, and the results are shown in FIG. 3. From FIG. 3, it can be seen that the conversion rate of the IAHF functional group increases with the increase of the molar ratio and does not change much, and from the viewpoint of energy, the conversion rate of the functional group reaches the maximum value at 1:3, and the maximum energy is saved. Thus, the optimum reaction molar ratio was determined to be 1: 3.

As described above, the optimum synthesis conditions for IAHF are shown in Table 2.

TABLE 2 optimal conditions for IAHF synthesis

Experiment 1-1

Weighing 15.0mg of acrylic fiber chelating fiber IAHF in multiple parts, placing into a 100mL iodine measuring flask, transferring into 25mL of HAc-NaAc buffer solution with different pH values, standing for 6h, adding 5mL of metal ion standard solution, performing shaking adsorption balance at 25 ℃, at 100 rmp. Sampling and determining the concentration of residual metal ions in the solution. The amount of adsorption (Q) and the adsorption rate (E) were calculated by the following formulas:

wherein Q is the adsorption capacity (mg/g) of the acrylic chelating fiber; c₀And C_eInitial concentration (mg/mL) and equilibrium concentration (mg/mL) of metal ions, respectively; w is the mass (g) of the acrylic chelating fiber; v is the volume of the metal ion solution (mL).

In the experiment, the pH range is 2.5-6.5, and the metal ion standard solutions are standard solutions of heavy metal ions Al (III), Hg (II), Zn (II), Cd (II), Pb (II) and Cr (II). As shown in FIG. 4, the adsorption amount of Hg (II) by the acrylic fiber chelate fiber IAHF is much larger than that of other five heavy metals, and the acrylic fiber chelate fiber IAHF has good selective adsorption property.

As shown in fig. 4, the influence of the solvent pH on adsorption of Hg (ii) by the acrylic chelate fiber IAHF was large, and the optimum adsorption pH was 5.5. The pH of the solution affects the presence (molecular, ionic, complex) and solubility of heavy metals in water, as well as the degree of protonation of functional groups on the fibers. In the environment with stronger acidity, the protonation degree of functional groups on the fibers is enhanced, which is not beneficial to the adsorption of heavy metal ions; under the condition of stronger alkalinity, the solubility of heavy metal ions is reduced, and precipitation is easy to occur. Therefore, the strong acid and strong alkali environment is not favorable for the adsorption of heavy metal ions by the chelate fiber.

Experiment 1-2

Weighing 15.0mg of acrylic fiber chelating fiber IAHF in multiple parts, placing in a 100mL iodine measuring flask, transferring into 25mL of HAc-NaAc buffer solution with optimal adsorption pH, standing for 6h, adding 5mL of metal ion standard solution, performing shaking adsorption at 15 deg.C, 25 deg.C and 35 deg.C, respectively, at 100 rmp. Sampling at regular time, and measuring the concentration of the metal ions in the solution until the concentration of the metal ions in the solution is unchanged, so as to achieve adsorption balance.

In this experiment, the metal ion standard solution is a standard solution of heavy metal ions Hg (II).

As shown in fig. 5, the adsorption amount (Q) becomes larger with time and reaches an equilibrium at a certain time point. Within the first 15min, the adsorption sites on the acrylic chelating fiber are more, the concentration of metal ions in the solution is higher, the adsorption rate is higher due to the larger mass transfer power, and the adsorption quantity is increased rapidly. With the saturation of the adsorption of the combinable active sites on the acrylic chelating fiber, the obstruction of the adsorption space is increased, the concentration of the metal in the solution is reduced, the adsorption rate is gradually reduced, and finally, the adsorption balance is achieved. The adsorption equilibrium time of the acrylic fiber chelating fiber IAHF to Hg (II) is 36 min. Compared with other traditional adsorption materials such as ion exchange resin and the like, the time of adsorption balance is greatly shortened, and the commonly used ion exchange resin can reach adsorption saturation within several hours. The reason is that the monofilament diameter of the acrylic chelating fiber is only 20-30 microns, and the mass transfer distance of metal ions in the fiber is short; meanwhile, the acrylic chelating fiber has larger specific surface area, so the acrylic chelating fiber has better dynamic performance. It can also be seen from the figure that temperature also has an effect on the adsorption rate and the adsorption amount. The adsorption rate and the adsorption amount of the fiber are sequentially increased along with the temperature increase, which shows that the temperature increase is favorable for the adsorption within the experimental temperature range.

Experiments 1-3: static desorption experiment

Weighing 15.0mg of acrylic fiber chelating fiber IAHF in multiple parts, placing into a 100mL iodine measuring flask, transferring into 25mL of HAc-NaAc buffer solution with optimal adsorption pH, standing for 6h, adding 5mL of metal ion standard solution, performing shaking adsorption balance at 25 ℃, at 100 rmp. Sampling and determining the concentration of residual metal ions in the solution. Filtering the fiber after adsorption balance, washing with deionized water for multiple times, air drying, placing into a new 100mL iodine measuring flask, adding 30mL desorbent, at 25 deg.C, 100rmp, and oscillating until the concentration of heavy metal ions (C) in the solution is determined by desorption balance_e"). Desorption rate (E'):

in the formula C₀And C_eRespectively the initial concentration (mg/mL) and the equilibrium concentration (mg/mL) of the metal ions in the adsorption stage; c_e' is the concentration of metal ions in the conical flask after desorption equilibrium.

In this experiment, the metal ion standard solution is a standard solution of heavy metal ions Hg (II). The resolving agents are HCl and HNO with different concentrations₃. The results of the experiment are shown in table 3.

TABLE 3 Desorption Rate of two different Desorption Agents for adsorption of Hg (II) to IAHF

As is clear from Table 3, the type and concentration of the desorbent greatly influence the analysis effect. In the desorption of Hg (II), 3.0 mol/L HCl can completely desorb IAHF.

Example 2

Putting 0.5g acrylic fiber chelating fiber IAHF, 0.3g PAR, 35mL water and 5mL formaldehyde water solution into a 100mL three-necked flask, stirring under nitrogen protection, heating and refluxing for 4h, stirring at 70 deg.C until the reaction is finished, taking out the fiber, and heating at room temperatureRepeatedly washing the fiber with water to be neutral, and putting the fiber into an oven to be dried (50 ℃) for 2 hours to obtain the color developing fiber IAHF-PAR. And (3) respectively placing the color developing fiber IAHF-PAR in various heavy metal ion solutions at room temperature, and observing the color developing effect. Wherein the heavy metal ion solution comprises Cd²⁺、 Hg²⁺、Al^{3 +}、Pb²⁺、Zn²⁺、Cr³⁺。

As shown in FIG. 6, the chromogenic fiber IAHF-PAR was aligned to 100ppm Cd²⁺、Hg²⁺、Al³⁺、Pb²⁺、Zn²⁺、Cr³⁺The six heavy metals are developed, and compared with a blank tube without any metal ions, the IAHF-PAR discoloring fiber Hg clearly shown in the experimental result of figure 6²⁺Has obvious color change response, changes the color from orange yellow to purple red, has poor color development effect on other five heavy metals, and shows that the fiber has better color development selectivity.

In the invention, the synthesis principle chemical formula of the IAHF-PAR of the color-changing fiber is as follows:

in addition, FIG. 7 shows a schematic representation of the color development effect of the color-developing fibers IAHF-PAR on Hg (II) at different pH values. As shown in FIG. 7, pH has a large influence on the color development of the color-developing fiber IAHF-PAR when it meets metal, at a lower pH, the color-developing fiber IAHF-PAR does not develop color or develops color incompletely, and when the pH is increased to 6, the color-developing fiber can develop color sufficiently. This is because, when the pH is lowered, the amine groups on the fibers and the pyridine groups on the PAR molecules will be protonated, which reduces the complexing power for the metal ions in solution, and only effective complexing will cause the fibers to change color. When the pH value is more than 6, metal ions in the solution are easy to precipitate, so that the color development process is unstable, and the color development experiment result is influenced.

Comparative example 2-1

The PAR in the example 2 was changed to 8-hydroxyquinoline and chrome black T, and the rest was the same as in the example 2; the results of comparison between the obtained colored fibers, i.e., the colored fiber I and the colored fiber II, and the colored fiber IAHF-PAR of the present invention are shown in Table 4.

TABLE 4 color development of different color-developing fibers to heavy metal ions

Color-developing fiber	Color development results
		Chromogenic fiber IAHF-PAR	For Hg2+Metal ions have color development
Color-developing fiber I: 8-hydroxyquinoline color-developing fiber	Non-response
		And (3) color-developing fiber II: chrome black T color-developing fiber	Non-response

Experiment 2-2

The IAHF-PAR fiber test piece is provided with PAR, if the PAR is deteriorated in a short time, the test piece cannot be normally used, so that the fiber test piece with short storage time cannot be used as an effective test tool. Therefore, the prepared IAHF-PAR test piece is respectively placed in dark and natural light, one part of the prepared IAHF-PAR test piece is placed at room temperature for storage, the other part of the prepared IAHF-PAR test piece is placed at low temperature (5-10 ℃) for storage, and the IAHF-PAR test piece is taken out every half month and compared with a standard colorimetric plate to determine whether the color rendering performance of the IAHF-PAR test piece is declined.

Experiments show that the color of the acrylic fiber IAHF-PAR which is preserved under natural light at room temperature is continuously darkened along with the increase of time, and after 2 months, the color level of a standard solution of 10mg/L Hg (II) is determined to be inconsistent with that of a standard colorimetric plate, so that the storage time at room temperature under natural light is 2 months. Similarly, the acrylic fiber chromogenic fiber IAHF-PAR can be stably stored for 6 months at room temperature and in a dark place; and the storage time can be prolonged to 1 year under the condition of low temperature (5-10 ℃).

Experiment 2 to 3

Preparing a series of Hg (II) standard solutions with different concentrations, namely 0ppm, 0.1ppm, 0.2ppm, 0.3ppm, 0.4ppm, 0.5 ppm, 1ppm, 2ppm, 3ppm, 4ppm, 5ppm, 10ppm, 20ppm, 50ppm and 100ppm, completely immersing the prepared acrylic fiber chromogenic fiber IAHF-PAR in the different standard solutions, taking out after 2s, and spin-drying. The fiber color values were taken with a digital camera and input into a computer, converted to RGB values with a Photoshop CS4 pipette tool, and recorded as shown in Table 5. The developed IAHF test piece is shot by a digital camera, the image is imported into a computer, the color of the test piece is converted into RGB mode (R represents Red, G represents Green and B represents Blue) information by a pipette tool in Photoshop CS4 software, and the numerical value is between 0 and 255. The color is digitalized, so that the accuracy is improved for the manufacture of the standard colorimetric plate.

TABLE 5 IAHF-PAR Standard color plate

As can be seen from Table 5, the overall color in the color comparison plate is from light to dark, and the color is uniform between different sampling points, and the data difference is not more than 10.

Example 3

(1) Preparing acrylic chelate fiber IAHF: the specific procedure was as for the preparation of IAHF in example 1.

(2) Preparation of color-developing fiber IAHF-PAR: the procedure was as described for the preparation of IAHF-PAR in example 2.

(3) Pretreatment of a sample to be detected: weighing a certain amount of mashed and homogenized sample, placing the sample into a polytetrafluoroethylene tube, and adding a certain amount of 30% H₂O₂And HNO₃Soaking overnight, placing into a digestion tank, placing into a digestion instrument, setting digestion conditions, wherein 30% H is added into the sample₂O₂And HNO₃The microwave digestion parameters under the set parameter conditions are shown in table 6 below. Take out poly-tetra after digestionPlacing a fluoroethylene tube on an electric heating plate, heating at 120 ℃ for 2h, dispelling acid until about 1mL of digestion solution is left, transferring into a volumetric flask, and fixing the volume to 25mL by using deionized water to be measured.

TABLE 6 microwave digestion parameters for agricultural products

(4) Completely immersing the IAHF-PAR acrylic fiber prepared by masking in a colorimetric tube for 2s, taking out, drying, converting the color into an RGB value after complete color development, and comparing with a standard colorimetric card to obtain the concentration of Hg (II) in the solution.

Comparative example 3-1

Preparing Hg with different concentrations²⁺10mL of each standard solution is taken, 10mL of sample solution with constant volume after the agricultural product is digested is taken, and the concentration of Hg (II) in the sample solution is measured by ICP-AES.

TABLE 7 comparison of the IAHF-PAR colorimetric assay with the ICP-AES assay

Referring to the international GB 2762-2012, the ICP-AES detection results shown in Table 7 show that the mercury content in lettuce, leaf lettuce, green vegetables, prawns, large yellow croakers, razor clams, pork livers, chicken livers, duck livers, mushrooms and agrocybe cylindracea in twelve agricultural products extracted in the experiment does not exceed the standard, but the mercury content in the agrocybe cylindracea exceeds the limit value. The national food safety standard defines the limit of mercury in edible fungi to be 0.1mg/kg, while the content of mercury in the golden mushroom to be 0.115mg/kg is 115% of the limit value, and sufficient attention should be paid. In addition, the mercury content in the mushroom is 0.090mg/kg, which is 90% of the limit value of the edible fungi; the mercury content in the prawns is 0.418mg/kg, which is 83.6 percent of the limit regulation (0.5mg/kg) of mercury in aquatic products in national food safety standards. The mercury content of the two agricultural products is within the safe limit, but the mercury content is close to the limit value, and people should pay attention. The content of Hg (II) in twelve agricultural products is extracted by using a color-changing fiber IAHF-PAR detection method and compared with an ICP-AES detection method. The result shows that the detection result of the IAHF-PAR color-changing fiber method is basically consistent with that of an ICP-AES conventional detection instrument, the method can be applied to the determination of the mercury content in aquatic products and agricultural products of edible fungi, and the analysis method has reliable result.

TABLE 8 test results of recovery with addition of the standard

And adding a certain amount of mercury standard solution, processing according to an experimental method, determining the content of mercury, and calculating the recovery rate, wherein the result is shown in Table 8, the result shows that the standard addition recovery rate is 97.3-98.6%, the result is satisfactory, and the feasibility of the method for detecting the content of mercury in agricultural products by using the modified polyacrylonitrile chelating color-changing fiber IAHF-PAR is further demonstrated. Compared with the conventional heavy metal detection method, the method effectively reduces the detection cost, simplifies the detection steps, and can be applied to detection and analysis of trace mercury in partial agricultural products.

The above embodiments do not limit the present invention in any way, and all technical solutions obtained by means of equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims (6)

1. A synthetic method of acrylic fiber chromogenic fiber IAHF-PAR is characterized in that: putting the acrylic fiber chelating fibers IAHF and PAR into a formaldehyde water solution, stirring, heating and refluxing for 2-6h under the protection of nitrogen, stirring and reacting at 70 ℃, washing with warm water, and drying to constant weight to obtain the color-developing fibers IAHF-PAR;

the synthetic method of the acrylic fiber chelating fiber IAHF comprises the following steps:

(1) taking acrylic fibers as a matrix, and soaking and swelling the acrylic fibers in toluene for 6 hours;

(2) adding a ligand into the product obtained in the step (1), and stirring at 40-100 ℃ under the protection of nitrogen until the reaction is finished, wherein the ligand is isoniazid, and the molar ratio of a matrix to the ligand is 1: 2-1: 6;

(3) washing the obtained substance in the step (2) with toluene to be colorless, and drying the washed substance to constant weight to obtain acrylic fiber chelating fiber IAHF;

in the step (1), the dosage ratio of the acrylic fiber to the toluene is 0.1-0.2g acrylic fiber/30 ml toluene; the molar ratio of the acrylic fiber to the isoniazid is 1: 3;

the washing in the step (3) is as follows: washing with anhydrous alcohol, acetone and diethyl ether in sequence; the reaction temperature in the step (2) is 100 ℃.

2. The method for synthesizing IAHF-PAR of acrylic fiber with color development according to claim 1, wherein the dosage ratio of the chelating fiber IAHF, PAR, water and formaldehyde is 0.5g IAHF/0.3g PAR/35mL water/5 mL formaldehyde.

3. A chromogenic fiber IAHF-PAR made according to the synthesis method of claim 1 or 2.

4. Use of the chromogenic fiber IAHF-PAR made by the synthesis method of claim 1 or 2 in the rapid detection of heavy metals in agricultural products.

5. Use of the chromogenic fiber IAHF-PAR according to claim 4 for the rapid detection of heavy metals in agricultural products, characterized in that: the heavy metal is Hg^{2 +}。

6. Use of the chromogenic fiber IAHF-PAR according to claim 5, for the rapid detection of heavy metals in agricultural products, characterized in that it comprises the following steps:

(1) pretreatment of a sample to be detected: the method comprises the steps of (1) obtaining a solution to be detected after a sample to be detected is smashed, digested and subjected to constant volume; the sample to be detected is an agricultural product;

(2) putting the digested agricultural product solution into a clean and transparent colorimetric tube, adjusting the pH value of the solution to be 7.0, immersing the chromogenic fiber IAHF-PAR in the solution to be detected for 2s, taking out the solution, spin-drying, converting the color information of the fiber color into RGB value after the chromogenic experiment is finished, and comparing the RGB value with a standard colorimetric card to obtain the content of Hg (II) in the agricultural product.

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