CN111850725B - Polyacrylonitrile-1-methyl piperazine chromogenic fiber and synthetic method and application thereof - Google Patents
Polyacrylonitrile-1-methyl piperazine chromogenic fiber and synthetic method and application thereof Download PDFInfo
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Abstract
The invention discloses polyacrylonitrile-1-methyl piperazine chromogenic fiber, which is prepared by taking Polyacrylonitrile (PAN) as a matrix and 1-Methyl Piperazine (MP) as a ligand, adding PAN, MP and sodium carbonate into ethylene glycol, heating to 110-145 ℃, and reacting for 10-40 min to obtain PAN-MP; and mixing the PAN-MP, the glycol, the formaldehyde and the PAR, heating to synthesize the color-developing fiber, and synthesizing at the temperature of 110-140 ℃ for 10-30 min to obtain the PAN-MP-PAR of the polyacrylonitrile-1-methylpiperazine color-developing fiber. PAN-MP-PAR selectively adsorbs Cu (II), and can be used for rapidly detecting Cu (II).
Description
Technical Field
The invention belongs to the technical field of chemistry, and particularly relates to a polyacrylonitrile-based-1-methylpiperazine color-developing fiber, a synthetic method and application thereof.
Background
Because the heavy metal has serious damage effect on human bodies and is difficult to metabolize, the detection of the content of the heavy metal in food is an important barrier for limiting the excessive intake of heavy metal ions by human bodies. In the existing detection method, the detection precision of a large-scale instrument and equipment is high, the result accuracy is high, but the equipment is expensive, complex to maintain and maintain, complex to operate, high in requirement on operators, long in detection period and suitable for detection scenes of laboratories and the like. The rapid detection method can save cost to a certain extent, quickens detection efficiency, improves detection capability and is more flexible and flexible to apply. The simple safety detection of large-scale food by means of large-scale instrument detection equipment cannot meet the detection requirement, and the simple, convenient, cheap, rapid, accurate and digital rapid detection equipment is the trend of food safety detection.
The polyacrylonitrile chelate fiber is developed on the basis of ion exchange fiber research, the working principle of adsorption is that a chelate with stable structure is formed between lone pair electrons contained in N, O, P, S and other elements in functional groups in an adsorption material and target ions, and a color developing agent is grafted on the basis, so that the rapid detection of the selected adsorbed heavy metal ions is significant according to the color change of the fiber.
2018102997183 patent of invention provides a modified polyacrylamide and its preparation method and application, taking polyacrylonitrile microsphere as parent, carrying out synthetic reaction with ligand (2-amino-4, 6-dimethyl pyrimidine) (ADMP), able to obtain chelate resin with high nitrogen content, which has good adsorption property to Cd (II).
201510447588X invention, namely 'a modified polyacrylonitrile', discloses a modified polyacrylonitrile, which consists of polyacrylonitrile, a filler, a curing agent, an accelerator, a coupling agent, a toughening agent and a vulcanizing agent, wherein the filler is glass fiber, the curing agent is N-aminoethyl piperazine, the accelerator is zinc dimethyldithiocarbamate, the coupling agent is methacryloxypropyl trimethoxysilane, the toughening agent is an acrylonitrile-butadiene-styrene copolymer, and the vulcanizing agent is benzoyl peroxide. The modified polyacrylonitrile has the characteristics of high strength, high wear resistance, good tear resistance and good fatigue resistance by adding the filler, the curing agent, the accelerator, the coupling agent, the toughening agent and the vulcanizing agent into the polyacrylonitrile.
Disclosure of Invention
The invention aims to provide a polyacrylonitrile-based chromogenic fiber PAN-MP-PAR which integrates the functions of enrichment, separation, chromogenic reaction and detection and is applied to the rapid detection of copper ions.
In order to solve the technical problems, the invention provides polyacrylonitrile-1-methyl piperazine chromogenic fiber (PAN-MP-PAR), which has a structural formula as follows:
the invention also provides a synthetic method of the PAN-MP-PAR, which comprises the following steps:
1) polyacrylonitrile (PAN) is used as a matrix, and 1-Methylpiperazine (MP) is used as a ligand; adding polyacrylonitrile fiber, 1-methylpiperazine and sodium carbonate into ethylene glycol (serving as a solvent), heating (microwave-assisted heating) to 110-145 ℃, and reacting for 10-40 min to obtain polyacrylonitrile-1-methylpiperazine chelate fiber (PAN-MP);
functional group-C ≡ N of PAN: MP ═ 1: 2-5 molar ratio; PAN: sodium carbonate 1: 2-5 mass ratio;
PAN: polyacrylonitrile fiber, MP: 1-methylpiperazine; PAN-MP: polyacrylonitrile-1-methylpiperazine chelate fibers;
the reaction process is as follows:
2) adding PAN-MP, ethylene glycol, formaldehyde and 4- (2-pyridylazo) resorcinol (PAR) into a container, heating (microwave-assisted heating) to synthesize a color-developing fiber, and synthesizing at 110-140 ℃ for 10-30 min to obtain polyacrylonitrile-1-methylpiperazine color-developing fiber (PAN-MP-PAR);
PAN-MP: PAR 1-3: 1 in mass ratio;
PAR: 4- (2-pyridylazo) resorcinol;
the reaction process is as follows:
the post-treatment modes after the reaction of the step 1) and the step 2) are as follows: and filtering the reaction product, washing a filter cake with water, and drying.
The improvement of the synthesis method of the polyacrylonitrile-1-methyl piperazine chromogenic fiber (PAN-MP-PAR) of the invention comprises the following steps:
in the step 1), the material-liquid ratio of PAN to glycol is 50.0mg (30 +/-5) ml;
in the step 2), the feed-liquid ratio of PAN-MP to glycol to formaldehyde is 30.0mg: (25. + -. 5) ml: (5 +/-1) ml;
the step 1) and the step 2) both adopt a microwave-assisted heating mode.
Step 1), the microwave power is 800W; in the step 2), the microwave power is 400W. This parameter can be used when every 50mg of polyacrylonitrile fiber is used as the raw material.
As a further improvement of the synthesis method of the polyacrylonitrile-1-methylpiperazine colored fiber (PAN-MP-PAR) of the invention:
in the step 1), the material-liquid ratio of PAN to glycol is 50.0mg to 30 ml; functional group-C ≡ N of PAN: MP ═ 1: 2 in a molar ratio; PAN: sodium carbonate 1: 3 in mass ratio; the heating (microwave-assisted heating) temperature is 130 ℃, and the reaction time is 15 min;
in the step 2), the feed-liquid ratio of PAN-MP to glycol to formaldehyde is 30.0mg:25 ml: 5ml of the solution; PAN-MP: PAR 3: 1 in mass ratio; the reaction temperature is 120 ℃ and the reaction time is 15 min.
The invention also provides the application of the polyacrylonitrile-1-methyl piperazine chromogenic fiber (PAN-MP-PAR): selectively adsorbing Cu (II).
As an improvement of the use of the present invention: and (3) rapidly detecting the Cu (II), namely establishing a qualitative detection method for macroscopic variation of the Cu (II).
As a further improvement of the use of the invention: in HAc-NaAc buffer solution with pH 6 and concentration of 0.2mol/L, PAN-MP-PAR has selective adsorption effect on Cu (II), and the adsorption amount is 184.76mg/g at 35 deg.C.
As a further improvement of the use of the invention: the HAc-NaAc buffer solution with the pH value of 6 and the concentration of 0.2mol/L is added with metal salt to be tested (or food suspected to contain Cu (II) pollution) and PAN-MP-PAR, the fiber color is darkened (the fiber color is changed from orange red to tan), and the metal salt is Cu (II) salt. The time required for the color reaction is at least 5 min.
In a HAc-NaAc buffer solution at a concentration of 0.2mol/L at pH 6, PAN-MP-PAR had a clear coloration effect on Cu (ii) and this coloration effect was visible to the naked eye, the fiber color changed from orange-red to tan, but not on the other test ions. That is, at pH 6, PAN-MP-PAR rapidly develops color to Cu (II) solution compared with other heavy metal ions, and fiber color changes from orange red to brown within 10min (at least 5 min).
As a further improvement of the use of the invention: the structural formula after PAN-MP-PAR binds copper ions is:
the synthetic formula of the invention is as follows:
the invention adopts the microwave-assisted method to prepare PAN-MP-PAR, so that the PAN-MP-PAR can effectively and selectively adsorb Cu (II), has good adsorption effect, and can be applied to the rapid detection of Cu (II) in food.
In the invention, the response surface method is utilized to further optimize the synthesis parameters, and the PAN-MP-PAR fiber obtained by the invention is subject to color change for detection of target heavy metal ions, because the selection of the synthesis conditions also needs to refer to the color depth of the fiber. Wherein the response surface method model is subjected to three-factor three-level experimental design on the reaction temperature, the reaction time and the molar ratio of the raw materials in the step 1), and takes the adsorption capacity as a measurement standard, and the specific model is as follows:
the table of variance analysis of the quadratic polynomial of the synthetic model in the three-factor three-level response surface optimization experiment process is shown in table 1.
TABLE 1 ANOVASTIC TABLE OF SECONDARY POLYMER OF RESPONSE SURFACE METHOD OPTIMIZED SYNTHETIC MODEL FOR PAN-MP SYNTHESIS
The concrete model obtained finally is as follows:
the influence of the interaction of the three factors on the adsorption amount and the screening of the optimization conditions are shown in figure 1. In combination with the color change of the developed fiber (fig. 2), the optimal level of the three factors finally determined is: 130 ℃, 15min, -CN: the MP molar ratio is 1: 2.
the invention has the following technical advantages:
(1) the compound synthesized by the invention is a new compound;
(2) the invention adopts the microwave-assisted method for preparation, and has simple synthetic method, high speed and less byproducts;
(3) the polyacrylonitrile-1-methylpiperazine color-developing fiber synthesized by the invention has the advantages of good adsorption selectivity to Cu (II), high adsorption speed, large adsorption quantity, good color development and the like.
(4) The polyacrylonitrile-1-methylpiperazine color fiber synthesized by the invention has good detection and removal effects on Cu (II) in food polluted by Cu (II).
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
FIG. 1 shows the influence of the interaction of three factors on the adsorption amount during the PAN-MP synthesis process and the screening of optimization conditions;
FIG. 2 is a comparison of fiber photographs of PAN, PAN-MP-PAR;
FIG. 3 is an infrared spectrum;
(a) is an infrared spectrum of PAN-MP fiber or the like
(b) Is an infrared spectrum synthesized by PAN-MP-PAR fiber;
FIG. 4 is a thermogravimetric plot of PAN, PAN-MP-PAR;
FIG. 5 is an XRD pattern for PAN, PAN-MP, and PAN-MP-PAR;
FIG. 6 shows the selective adsorption effect of PAN-MP-PAR fibers;
FIG. 7 is a representation of the presence of copper ions in solution;
FIG. 8 shows the adsorption effect of PAN-MP-PAR fibers at different contact times;
FIG. 9 is the effect of initial concentration on the adsorption capacity of PAN-MP-PAR fibers;
FIG. 10 is a graph of the effect of buffer solution pH on the matrix color produced by PAN-MP-PAR fibers;
FIG. 11 shows the effect of heavy metal ion species on the color rendering effect of PAN-MP-PAR;
FIG. 12 is a graph showing the effect of contact time on PAN-MP-PAR color rendering.
Detailed Description
The invention will be further described with reference to specific examples, but the scope of the invention is not limited thereto:
example 1, a preparation method of polyacrylonitrile-1-methylpiperazine color developing fiber, the following steps were carried out in sequence:
1) 50mg (containing 1.425 mmol-C.ident.N group) of polyacrylonitrile fiber (PAN) as a precursor, 2.85mmol of 1-Methylpiperazine (MP) as a ligand and 150mg of sodium carbonate were weighed, sequentially added to a three-necked flask, and 30mL of ethylene glycol was further added, and transferred to a microwave synthesis station.
Setting the microwave power of 800W, the temperature of 130 ℃ and the time of 15 min.
After the reaction is finished, cooling the three-neck flask to room temperature, taking out the fibers (namely, filtering, taking filter cakes) and putting the fibers on a sand core funnel, adding deionized water, repeatedly performing suction filtration until the liquid (namely, the obtained washing liquid) is clear, so as to wash out the residual ligand and sodium carbonate on the surface, and then placing the liquid in a vacuum drying oven at 50 ℃ to dry until the weight is constant, so as to obtain the polyacrylonitrile-1-methylpiperazine chelate fiber (PAN-MP).
The polyacrylonitrile-1-methyl piperazine chelate fiber (PAN-MP) is synthesized by the following formula:
2) adding ethylene glycol, formaldehyde and PAR (4- (2-pyridylazo) resorcinol) as a color developing agent into chelate fiber PAN-MP, heating at 120 deg.C with the assistance of microwave, reacting for 15min,
after the reaction is finished, filtering, repeatedly washing a filter cake by deionized water, and drying in a vacuum drying oven at 50 ℃ to constant weight to obtain PAN-MP-PAR;
chelate fiber PAN-MP: color developing agent PAR 3: 1 in mass ratio; the microwave power is 400W; the feed-liquid ratio of the chelate fibers to the ethylene glycol is 30mg/25 ml; the feed-liquid ratio of the chelate fibers to the formaldehyde is 30mg/5 ml.
The polyacrylonitrile-1-methylpiperazine color-developing fiber (PAN-MP-PAR) has the synthetic formula:
the invention uses Fourier infrared spectrometer to carry out structural characterization on the synthesized new compound PAN-MP-PAR:
FIG. 3 is a graph of the infrared spectra resulting from (a) PAN-MP fibers and (b) PAN-MP-PAR fibers;
as shown in (a), PAN-MP was 2244cm in comparison with PAN, a raw material fiber -1 The peak of cyano group is obviously weakened; also 1636cm was concomitantly present -1 And C is an N stretching vibration peak, which indicates that the reaction of polyacrylonitrile and the ligand is mainly consumption of cyano. (b) In the figure, the reaction between PAN-MP and PAR is at 1364cm -1 A symmetric absorption peak of N-O bond appears at the position, and the asymmetric peak is at 1550cm -1 Here, it is presumed that the bonding mode of PAR and PAN-MP may be such that oxygen in phenolic hydroxyl group-OH is bonded to N in C ═ NH to form N — O bond, and grafting of the color developer to the chelate fiber is completed to obtain a color-developed fiber.
Description of the drawings: PAN + MP in the figure represents a mechanical mixture of PAN and MP.
FIG. 4 is a thermogravimetric plot of PAN, PAN-MP-PAR;
as shown in the thermogravimetric plot of fig. 4, the initial decomposition temperature of PAN was 274 ℃, the terminal decomposition temperature was 831 ℃, and the mass change reached 100%. The PAN-MP-PAR had a mass change of about 6.9% before 100 c, which was caused by the evaporation of bound water, followed by an initial decomposition temperature of 275 c, two successive smaller decomposition gradients caused by N evaporation, and then a rapid decomposition to 707 c was terminated.
From SEM images comparison of PAN, PAN-MP and PAN-MP-PAR fibers: SEM images of PAN show that the PAN fiber is uniform in thickness and 11.7 μm in diameter, and a large number of slight wrinkles exist on the surface, which are beneficial to increasing the specific surface area of the PAN fiber. The fibers obtained after chelation become rough, the chelating fibers are 22.5 mu m directly, the surface roughness of PAN-MP-PAR is not much different from that of the chelating fibers, and the diameter is obviously increased to 29.4 mu m. From the above analysis, it was found that the diameter of the fiber gradually increased and the roughness gradually increased after the two-step reaction, probably because in the severe microwave reaction process, the ligand attacks the active groups on the fiber surface and in the body by means of the ethylene glycol solvent, the electrostatic repulsion between the fibers after grafting the ligand increased, resulting in fiber thickening, and after further reaction with the color developer, the fiber structure became looser due to the complex chemical structure of PAR, resulting in regular change in diameter.
FIG. 5 is an XRD pattern for PAN, PAN-MP, and PAN-MP-PAR;
as can be seen in fig. 5, the PAN fiber has a sharp diffraction peak at 16.9 °, which means that the PAN fiber has a similar crystal structure, and the index of the diffraction lattice plane is (100), which is actually mainly due to the intermolecular repulsion between-CN dipoles in the PAN fiber, while parallel molecular rods are formed in the fiber matrix and exhibit hexagonal characteristics in an array. After the first-step chelation reaction, the-CN dipole in the PAN is attacked by the active group of the ligand, so that the regular arrangement of the-CN dipole is damaged, the intensity of the diffraction peak is weakened, after the second-step chelation reaction, N in the-CN dipole is further combined with the PAR group, so that the electrons in the-CN dipole are rearranged again, the rule of the hexagonal system is further damaged, and the diffraction intensity is weakened. And further analysis shows that the 2 theta angle corresponding to the diffraction peak of the fiber moves towards the high angle direction after the two-step reaction, because the repulsion force between fiber molecules is further increased by grafting of each functional group, so that the interplanar spacing is increased. According to the bragg equation, the diffraction angle and interplanar spacing, as the diffraction angle increases within the test range, the interplanar spacing decreases as the incident wavelength does not change, consistent with the above analysis.
(1) Selective adsorption
5mg of PAN-MP-PAR fiber synthesized in example 1 is weighed and added into 10mL of solution, the solution contains Pb (II), Cu (II), Zn (II), Ni (II) and Cd (II) with the concentration of 100mg/L, the buffer solution used in the solution preparation is prepared by 0.2mol/L HAc and 0.2mol/L NaAc according to a certain volume ratio, the accurate pH value is determined by an acidimeter, an adsorption experiment is carried out at 25 ℃, the adsorption capacity is measured after 24 hours of adsorption, and meanwhile, a parallel experiment is carried out.
The results are shown in fig. 6, the PAN-MP-PAR fibers achieved maximum Cu (ii) adsorption at pH 6; the influence rule of pH on the fiber adsorption of Cu (II) basically accords with the ionization tendency of Cu (II) in an aqueous solution, and as shown in figure 7, when the pH is less than 5, the Cu (II) in the solution is basically Cu 2+ Form exists, Cu in the process of increasing pH from 5 to 8 2+ Gradual conversion to Cu (OH) + When the pH continues to increase, the Cu (II) in the solution is further hydrolyzed into Cu (OH) 2 . From the aspect of adsorption quantity, when the pH value is lower, the fiber contains a large number of reaction sites which can react with Cu in time 2+ The reason for the reaction, but the lower adsorption capacity is: large amount of H exists in the solution + With Cu 2+ Form competitive adsorption between the two; in addition, functional groups in the fibers can be protonated, so that electrostatic repulsion is formed between the functional groups and copper ions, and adsorption is prevented. As the pH increases, the phenomenon gradually weakens, and Cu (II) still adopts Cu in the solution 2+ Mainly, so the adsorption quantity is rapidly increased, and when the pH value is 6, Cu in the solution 2+ The ratio is about 97%, Cu (OH) + Only 3% and Cu (OH) 2 Hardly occurs, which is very advantageous for its complex formation. If the pH continues to increase, the form of Cu (II) in the solution changes rapidly, Cu 2+ The ratio decreases rapidly, resulting in a gradual decrease in the amount of adsorption.
(2) Effect of contact time on adsorption quantity
As shown in FIG. 8, the reaction time and temperature are two factors that are important in the chemical reaction, and this is also fully reflected in the adsorption reaction of the color-developing fiber to Cu (II). As can be seen from fig. 8, the adsorption amount of the colored fibers significantly increased with the increase of the reaction time after the start of the reaction, but the increase of the adsorption amount became slow as the reaction time approached 20min until the adsorption amount completely leveled off, and the phenomenon exhibited similar variation trends at 15 ℃, 25 ℃, 35 ℃. This is because, under certain initial conditions (200mg/L), the concentration of Cu (II) in the solution is high at the very beginning of the reaction, and the active reaction sites in the colored fibers are not occupied, so that the probability of collision is high, and the probability of effective collision is also high, the reaction rate is high, and the chelation process is very rapid. As the reaction proceeds and the reaction time is prolonged, the reaction sites in the color-developing fiber are gradually occupied, and even if the concentration of Cu (II) in the solution is still high, the effective collision probability between the Cu (II) and the active groups of the color-developing fiber is reduced, so that the reaction rate is reduced, and moreover, a large amount of Cu (II) in the solution is consumed in the reaction process. After 20min, the active sites of the fiber novel copper ion color development sensor in the preparation and application research of the fiber novel copper ion color development sensor in food are basically occupied, the concentration of Cu (II) is also reduced, the reaction rate tends to be gentle, and the dynamic balance of adsorption and desorption is gradually achieved.
(3) Effect of initial concentration on adsorption amount
As shown in FIG. 9, the concentration of the heavy metal ion solution affects the probability of collision between the heavy metal ions and the functional groups in the fibers, and further affects the reaction rate and the adsorption amount, so the experiment (25 ℃, 15min) of the effect of the initial concentration on the adsorption amount of each color-developing fiber was performed by taking Cu (II) as an example. It can be seen from FIG. 9 that when the initial concentration of Cu (II) is less than 200mg/L, the Cu (II) adsorption amount of the colored fibers increases rapidly as the Cu (II) concentration increases. When the initial concentration reached 200mg/L, the amount of adsorption of the colored fibers increased but became slower by increasing the initial concentration. This is because the larger the initial concentration is, the higher the content of heavy metal ions per unit volume is, the higher the probability of direct collision with the color-developing fiber is, the higher the chelating probability is, and the higher the amount of adsorption in a certain period of time is. In the case of a Cu (II) solution having too low an initial concentration, the Cu (II) content per unit volume is low, and the total amount of Cu (II) in the solution is also low, and therefore, the active reaction sites in the colored fibers cannot be covered, and the amount of adsorption is low.
(4) Maximum adsorption capacity test
When the pH of the buffer solution was 6, the adsorption temperature was 35 ℃ and the adsorption time was 2 hours, the amount of copper ions adsorbed by PAN-MP-PAR was determined to be 184.76mg/g when the initial concentration of copper ions was 400mg/L according to the above-mentioned method.
Experiment 2, color development experiment of PAN-MP-PAR
Taking 5mg of color-developing fiber PAN-MP-PAR, adding 9mL of buffer solution (with a certain pH value), preparing the buffer solution by 0.2mol/L HAc and 0.2mol/L NaAc according to a certain volume ratio, determining the accurate pH value by an acidimeter, then respectively adding 1mL of 2000mg/L heavy metal ion standard solution, shaking up, respectively collecting reaction pictures at different time, and analyzing the pictures to obtain the rule of influence of color-developing time on color-developing performance. And respectively investigating the color rendering performance of single-factor experiments such as different heavy metal ion species, the pH value of the buffer solution, the time of color rendering reaction of the buffer solution and copper ions and the like on PAN-MP-PAR. The heavy metal ion species are as follows: pb (II), Cu (II), Cd (II), Ni (II) and Zn (II); the initial concentration of heavy metal ions in the color reaction system is 200 mg/L; the pH values are respectively 3, 4, 5 and 6; the color reaction time is 0-20 min.
(1) The influence of the pH value of the buffer solution on the PAN-MP-PAR fiber chromogenic substrate has the experimental parameters of 25 ℃, 3-6 of pH and no addition of heavy metal ions (namely, 1mL of 2000mg/L heavy metal ion standard solution), and the result shows that the pH value of the buffer solution can generate an obvious substrate effect, and the result is shown in figure 10. At lower pH conditions, the chromogenic fibers will hydrolyze under these conditions, resulting in PAR hydrolyzing off the chromogenic fibers, dissolving in the buffer solution, forming a red solution. The color of the solution can cause matrix effect during actual detection, and the detection result is interfered. Therefore, a pH of 6 was selected as the condition for the subsequent color development experiment.
That is, in the color chart of fig. 10, when the pH is 3, 4, or 5, the corresponding solution is red.
(2) The heavy metal ion species have influence on the PAN-MP-PAR color development effect, the experimental parameters are that the heavy metal ion species are Pb (II), Cu (II), Cd (II), Ni (II) and Zn (II), the initial concentrations are all 200mg/L, the pH value of the buffer solution is 6, the color development reaction time is 10min, the temperature is 25 ℃, and the color development result is shown in figure 11. Under the same experimental conditions, PAN-MP-PAR produces selective color development on copper ions, and the color of the fiber changes from orange red to tan and finally even to black. The fiber has no obvious color change to other heavy metal ion solutions.
(3) The contact time of copper ions influences the PAN-MP-PAR color development effect, the experimental parameter is that the initial concentration of the copper ions is 200mg/L, and FIG. 12 shows the influence of the contact time on the PAN-MP-PAR color development effect; from the figure, it can be seen that after the color-developing fiber is contacted with the copper ion solution, the color of the fiber is obviously changed within 5min, which indicates that the rapid detection of the copper ions can be realized within the time.
Comparative experiment 2, detection was performed according to experiment 1 using polyacrylonitrile as a matrix, N-Aminoethylpiperazine (NAP) as a ligand, and PAR as a color developer to obtain PAN-NAP-PAR; preferably, the maximum adsorption capacity of Cu (II) is about 115 mg/g.
Comparative example 1, the amount of PAN was kept constant and the amount of MP was varied so that the functional group-C ≡ N: the molar ratio of MP was changed to 1:1.5, and the rest was identical to example 1.
The resulting product was tested as described above for experiment 1; preferably, the maximum adsorption capacity of Cu (II) is about 131 mg/g.
Comparative example 2-1, the "temperature 130 ℃ C., time 15 min" in step 1) was changed to "temperature 110 ℃ C., time 20 min", and the rest was identical to example 1.
The resulting product was tested as in experiment 1 above; under the preferred condition, the maximum adsorption capacity of Cu (II) is about 108 mg/g.
The obtained product was tested as described in experiment 2, and color change started to occur only after it was in contact with copper ions for more than 20min, and the color development was significantly weaker than that of PAN-MP-PAR prepared under the optimal synthesis conditions (example 1).
Comparative example 2-2, the "temperature 130 ℃ and time 15 min" in step 1) was changed to "temperature 160 ℃ and time 15 min", and the rest was identical to example 1.
The resulting product was carbonized in appearance and caked, making subsequent experiments impossible.
Finally, it is also noted that the above-mentioned list is only a few specific embodiments of the present invention. It is obvious that the invention is not limited to the above embodiments, but that many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.
Claims (8)
1. The polyacrylonitrile-1-methyl piperazine chromogenic fiber is characterized in that the structural formula is as follows:
2. the method for synthesizing polyacrylonitrile-1-methylpiperazine color-developing fiber according to claim 1, characterized by comprising the following steps:
1) PAN is used as a matrix, and MP is used as a ligand; adding PAN, MP and sodium carbonate into ethylene glycol, heating to 110-145 ℃, and reacting for 10-40 min to obtain PAN-MP;
functional group-C ≡ N of PAN: MP ═ 1: 2-5 molar ratio; PAN: sodium carbonate 1: 2-5 mass ratio;
PAN: polyacrylonitrile fiber, MP: 1-methylpiperazine; PAN-MP: polyacrylonitrile-1-methylpiperazine chelate fibers;
2) adding PAN-MP, ethylene glycol, formaldehyde and PAR into a container, heating to synthesize the color-developing fiber, and synthesizing at the temperature of 110-140 ℃ for 10-30 min to obtain the polyacrylonitrile-1-methylpiperazine color-developing fiber;
PAN-MP: PAR 1-3: 1 in mass ratio;
PAR: 4- (2-pyridylazo) resorcinol.
3. The method for synthesizing polyacrylonitrile-1-methylpiperazine color fibers according to claim 2, characterized in that:
in the step 1), the material-liquid ratio of PAN to glycol is 50.0mg (30 +/-5) ml;
in the step 2), the ratio of the PAN-MP to the ethylene glycol to the formaldehyde is 30.0mg: (25. + -. 5) ml: (5 +/-1) ml;
the step 1) and the step 2) both adopt a microwave-assisted heating mode.
4. The method for synthesizing polyacrylonitrile-1-methylpiperazine color fibers according to claim 2 or 3, characterized in that:
in the step 1), the material-liquid ratio of PAN to glycol is 50.0mg to 30 ml; functional group-C ≡ N of PAN: MP ═ 1: 2 in a molar ratio; PAN: sodium carbonate 1: 3 in mass ratio; the heating temperature is 130 ℃, and the reaction time is 15 min;
in the step 2), the feed-liquid ratio of PAN-MP to glycol to formaldehyde is 30.0mg:25 ml: 5ml of the solution; PAN-MP: PAR 3: 1 in mass ratio; the reaction temperature is 120 ℃, and the reaction time is 15 min.
5. The use of polyacrylonitrile-1-methylpiperazine colored fibers as claimed in claim 1, characterized in that: selectively adsorbing Cu (II).
6. The use of polyacrylonitrile-based-1-methylpiperazine color-developing fibers according to claim 5, characterized in that: and rapidly detecting Cu (II).
7. The use of polyacrylonitrile-1-methylpiperazine color fibers according to claim 6, characterized in that:
adding a metal salt to be tested and PAN-MP-PAR into a HAc-NaAc buffer solution with the pH value of 6 and the concentration of 0.2mol/L, wherein the color of the fiber is darkened, and the metal salt is Cu (II) salt.
8. The use of polyacrylonitrile-based-1-methylpiperazine color-developing fibers according to any one of claims 5 to 7, characterized in that: the structural formula after PAN-MP-PAR binding copper ions is:
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