TWI583834B - A fiber structure with adsorption of copper ion and the manufacturing method - Google Patents

Description

Fiber structure with function of adsorbing copper ions and manufacturing method

The invention relates to a method for preparing nanofibers prepared by surface amination electrospinning technology, and is suitable for treating copper-containing wastewater.

In recent years, industrial activities have flourished, and the application of heavy metals has increased dramatically. Copper has been widely used in the chemical industry, for example, in the manufacture of wires, thin metal sheets, and pipes, etc.; however, a considerable amount of copper contaminated water is produced in the process. And entering the water body, may cause environmental and biological hazards, therefore, the chemical industry discharge water standard formulated by the Environmental Protection Agency of China, the copper discharge water quality standard is 3.0mg / L ^-1 .

Since most heavy metal pollutants are extremely difficult to be decomposed by microorganisms in an aqueous environment, they are currently used in methods for removing heavy metal ions in water, mainly including chemical precipitation, reverse osmosis, electrodeposition, ion exchange, and adsorption. Method, solution extraction method, evaporation, solidification method and membrane separation, etc.; wherein the adsorption method is a method of using a porous material as an adsorbent to adsorb and remove heavy metal ions in wastewater. Since the adsorbent has various functional group characteristics such as a hydroxyl group, a mercapto group, a carboxyl group, an amino group and the like, these functional groups reach an adsorption metal ion by forming an ionic bond or a covalent bond with the adsorbed metal ion. For the purpose of the sub-segment, factors such as pH, temperature, adsorption time and initial concentration of adsorbate will affect the adsorption amount.

Due to the high adsorption efficiency, selectivity, regeneration and stability of the adsorption method, attention has been paid. On the other hand, it is difficult to recover the powdery adsorbent. Therefore, the nanofiber membrane has high surface area, high structural stability, large porosity, small pore size, and material properties favorable for recycling, and is extremely suitable as an adsorbent. In the adsorption method. Among the many nanofiber materials, a nanofiber membrane prepared by electrospinning technology, the fiber prepared by this method has the advantages of large surface area, small pore size and high porosity (Deitzel et al. , 2001; Huang et al., 2003); the electrospinning device, as shown in FIG. 11, mainly includes a high voltage power source A, a wire nozzle B and a collector C, when a high voltage is applied to the high In the molecular solution D, a deformed solution (Taylor cone) is generated at the tip end of the metal spinneret B. When the threshold voltage is higher, the electric power on the surface of the droplet is sprayed against the surface tension of the solution, and the polymer solution is stretched. The solvent evaporates during the process and is collected into a nanofiber membrane material. The fiber diameter prepared by this technology is mostly between about ten and several hundred nanometers, and can be applied to biomedicine, filtration, energy, protective materials, textiles, and the like.

However, a nanofiber material having only physical properties is difficult to have a good adsorption effect on heavy metals. Therefore, the present inventors have provided a nanofiber membrane with better adsorption of heavy metals, especially for bivalent. A nanofiber membrane made by an electrospinning technique for copper ion adsorption.

The object of the present invention is to provide a fiber structure having a function of adsorbing copper ions and a manufacturing method for reducing the concentration of divalent copper ions in water after the general copper-containing wastewater is treated by the fiber structure of the present invention.

The invention provides a fiber structure with a function of adsorbing copper ions and a manufacturing method thereof, the method comprising: A. preparing a polyacrylonitrile nanofiber (PAN) by single-needle electrospinning; and B. the polyacrylonitrile nanofiber The fibers (PAN) are surface modified to form an aminated polyacrylonitrile nanofiber (APAN).

By the above method, a divalent copper ion aqueous solution having a concentration of 5 to 40 ppm and a pH range of 4 to 8 can be used, and a large amount of NH2-functional groups on the surface of the aminated polyacrylonitrile nanofiber (APAN) can be used. The Cu(II) ion reacts and is adsorbed onto the aminated nanofiber. According to the experimental results, the adsorption effect on Cu(II) is up to 166.7 mg/g, and can be completely separated from the solution. It has good recyclability and can be used as an excellent adsorbent in water treatment technology.

Please refer to FIG. 1 , which is a flow chart of a preferred embodiment of the present invention, comprising: A. preparing a polyacrylonitrile nanofiber (PAN) by single-needle electrospinning; and B. The nanofiber (PAN) is surface modified to form an aminated polyacrylonitrile nanofiber (APAN).

Wherein step A. is a method for preparing PAN polyacrylonitrile nanofibers: dissolving polyacrylonitrile in dimethylacetamide (DMAc) solvent to prepare a 6 wt% polymer solution at 280 rpm min ^{- 1} magnetic stirring for 4 hours, 1 hour of ultrasonic vibration to obtain PAN homogenization solution; finally, the prepared spinning solution was placed in a 10mL syringe with 23# stainless steel needle, and then electrospinning on the collector by electrospinning process Polyacrylonitrile nanofiber layer; the flow rate of the mixed solution is controlled at 1.0 mL/hr, the distance between the collector and the needle is 15 cm, the control voltage is about 13-16 KV, and the collection rotation is between 20 and 30 cm sec ^-1 ; The fiber diameter of the nitrile nanofiber membrane was measured by SEM.

Further, the step B. is a method for preparing an APAN aminated polyacrylonitrile nanofiber: dissolving 1 g of sodium carbonate as a catalyst in 70 mL of ultrapure water, and adding 30 mL of diethylenetriamine (DETA) to be configured The diethylenetriamine solution is poured into a 250 mL beaker, and the polyacrylonitrile nanofiber membrane is put into a diethylenetriamine solution, and the reaction is carried out at 120 ° C for 3 to 5 hours until the fiber color changes to orange color, and the fiber is taken out. The mixture was washed with neutral water to neutrality, and dried under vacuum at 35 ° C for 24 hours to obtain an amine-modified PAN nanofiber and a directly aminated PAN nanofiber.

The reagent used in the manufacturing method of the preferred embodiment of the present invention comprises: the spinning solution applied to the electrospinning technology, which is a polyacrylonitrile (PAN) polymer, and the average relative molecular weight is M=150000, and the spinning The silk solvent is dimethylacetamide (DMAC), all from SIGMAALDRICH, USA; the pH adjustment is based on the use of 95% sodium hydroxide (NaOH) and 37% Hydrochloric acid (HCl). Japan NIHON SHIYAKU REAGENT company; providing ethylene-derived diethylenetriamine DETA, the catalyst in the reaction is from Japan NIPPON SHIYAKU KOGYO KK; and 99% sodium carbonate Sodium Carbonate Anhydrous is from Japan NIHON SHIYAKU REAGENT company.

Analysis of the characteristics of the instrument: Scanning Electron Microscope (SEM): produced by Hitachi, Japan, model S-4700. First, a small amount of sample is first dispersed in an alcohol solution and dispersed by ultrasonic vibration. After drying the sample, it is fixed on a metal stage by carbon glue to increase its conductivity (gold plating thickness 150Å), and then The surface morphology and microstructure change of the catalyst can be observed; the X-ray diffraction (XRD) is the MXP18 type produced by Japan MAC Science Co., Ltd., and the light source is CuK as the radiation source (λ = 0.1541 nm), and the output is The power is 18KW, the scanning range is 200-800, and the scanning degree is 0.50 min-1. The crystal microstructure and grain size can be analyzed by using the diffraction angle and diffraction intensity of the obtained spectrum. The bonding and functional groups of the self-made aminated nanofibers were analyzed and analyzed by Fourier transform infrared spectrometer (FTIR), which was produced by Perkin Elmer Inc, USA, Model Spectrum 100. The outside of the analytical instrument is flushed with nitrogen to keep it dry, and the effect of moisture is minimized. A proper amount of sample powder is evenly covered onto the ITR detector, and the tablet is pressed down to make the sample in the infrared detector. It can be analyzed and detected in a thin shape with the tablet knob. The Cu ²⁺ ion content in the solution was measured by inductively coupled plasma optical emission spectrometer ICP-AES, Agilent Technologies' AU12440312 model; the pH of the solution was measured with a pH meter and made in Taiwan, model SP-701.

The method of applying the APAN aminated polyacrylonitrile nanofiber to adsorb Cu(II): preparing 100 mL of different concentrations (5, 10, 20 and 0 ppm) of Cu ²⁺ standard solution in a 500 mL reagent bottle, and inputting 0.2 g The nanofibers were placed in a constant temperature oscillator with a oscillating speed of 125 rpm/min and oscillated at different temperatures (15, 25, 34 and 5 °C). Adjust the pH of the solution (4, 6, 7, 8) with 1M HCl or 1M NaOH, sample at 5, 10, 15, 20, 30, 45, 60, 90, 120, 150 minutes and use inductively coupled plasma The emission spectrometer (ICP-AES) was used to analyze the change in Cu ²⁺ content in the solution.

Please refer to Figure 2 for a scanning electron microscopy (SEM) photograph of PAN nanofibers (PAN) and directly aminated polyacrylonitrile nanofibers (APAN). It can be seen from the figure that before modification (Fig. a) After the properties (Fig. b), the structural morphology of the fibers did not change greatly. There was no bond between the modified fibers, and the high porosity of the electrospun nanofiber membrane was maintained. However, the diameter of the fiber before the modification was found to be in the range of 100 to 250 nm, and the diameter range after the modification was increased to 200 to 600 nm.

Referring to FIG, based PAN is a FTIR spectrum comparison with FIG APAN in FIG 3 at 2239 cm ^-1, 1731cm ^-1 and 1200-1300cm ^-1, respectively (C≡N), (C = O ), ( The bending vibration of CO) is a characteristic peak of PAN, and the corresponding characteristic peak can also be observed also on APAN. The (C≡N) absorption peak at 2239 cm ^-1 after amination reaction and the (CO) absorption peak at 1731 cm ^-1 were significantly weakened, indicating that the cyano group was gradually destroyed in the amination reaction and was at 1561 cm ^{-1 .} The stretching vibration peak of the NH group appeared, indicating that the NH group was introduced to the surface of the PAN, and the cyano group of PAN had been reacted with diethylenetriamine and successfully converted into an amine group and a guanamine group.

Please refer to FIG. 4 , which is an XRD pattern of PAN nanofibers before and after amino group modification, wherein the XRD diffraction pattern of PAN nanofibers exhibits a broad peak at 2θ= 17.1°, which can be attributed to the crystal plane. PAN crystallite structure. It can be seen from the XRD diffraction pattern of APAN that the amination process does not destroy the fiber crystallinity; the amorphous structure of PAN nanofibers may be due to the solvent in the process of electrospinning from the needle. It is rapidly evaporated, thereby preventing the formation of crystallization between macromolecular chains, so that the density of the fibers is lowered, and thus, the obtained composite nanofibers exhibit an amorphous structure.

5 and FIG. 6 are diagrams showing Cu(II) adsorption performance test results of the fiber structure of the present invention. First, referring to FIG. 5, comparing the adsorption efficiency of Cu ²⁺ by PAN nanofibers before and after amine modification, respectively PAN and APAN nanofibers were added to 100 mL of 10 ppm Cu ²⁺ solution with a pH of 6 to compare the adsorption effects of the two. As shown in Fig. 5, the PAN curve tends to be gentle and has no obvious adsorption effect. It shows that the pure PAN fiber does not have the ability to adsorb heavy metal copper; while the APAN fiber has a significant decrease in the early stage of adsorption, and then tends to be flat and reaches the adsorption equilibrium in 120-150 minutes, and the adsorption efficiency reaches 90%, indicating that the amine group is modified. The adsorption efficiency of the rear fiber is greatly increased.

Referring again to Figure 6, 0.2 g of aminated PAN fiber was added to a 10 ppm Cu ²⁺ solution at pH 3, 5, 7 and 9, respectively. The adsorption time and Cu ²⁺ concentration results are shown in Figure 6; All the curves also showed a significant downward trend in the initial stage of adsorption. With the increase of time, the adsorption effect became more and more gentle until the adsorption equilibrium state was reached. The pH ²⁺ solution has the best Cu ²⁺ adsorption effect, which is obviously better than other pH solutions, and it is found from Fig. 6 that too high or too low pH value is not conducive to Cu ²⁺ adsorption, mainly because: 1 Too low a pH value, containing a H+ ion concentration that is too high, competes with metal ions for the same adsorption site, resulting in a decrease in adsorption capacity. 2. When the pH value is about 6, the presence of an appropriate amount of H ⁺ does not cause competition, so the slightly acidic environment contributes to the adsorption reduction of Cu ²⁺ . 3. The solution of high pH value, containing a large amount of OH ^- ions are present, the hydrolysis reaction easily precipitate with the metal ions to be adsorbed to the surface of the composite nano-fiber, hindered amine in contact with Cu ^2+; and The electrostatic repulsion between the solution and the composite fiber increases with increasing pH, which also increases the difficulty of Cu ²⁺ ions adsorbing onto the fiber surface.

In order to better describe and understand the mechanism of adsorption behavior of nanofiber structure created by the present invention for Cu(II), the pseudo-first-order kinetic model and the pseudo-second-order kinetic model are used to analyze experimental data. ; as expressed by the following equation: The pseudo first-order dynamics model Ln(q _{e . exp} -q _t ) = Lnq _{e . Cal} – Pseudo-second-kinetic model where q _t represents the adsorption capacity of aminated nanofibers for copper ions (mg/g) at any time t; q _e represents the adsorption capacity of aminated nanofibers for copper ions in equilibrium ( Mg/g); K ₁ is a pseudo first-order kinetic reaction constant, and K ₂ is a pseudo second-order kinetic reaction constant. By setting a function of time t vs. Log(q _e -q _t ), the calculated value q _e and the reaction constants K ₁ and K ₂ can be obtained by the slope and intercept of the straight line, and the results are shown in FIGS. 7 and 8 . The correlation coefficient R ² is summarized in Table 1. Table 1. Comparison of the results of the pseudo first-order kinetic model and the pseudo-second-kinetic model analysis<TABLE border="1"borderColor="#000000"width="85%"><TBODY><tr><td> ion concentration ( Ppm) </td><td>experiment</td><td> pseudo first-order kinetic reaction</td><td> pseudo second-order kinetic reaction</td></tr><tr><td> q _e_._exp (mg/g) </td><td>q_e_._cal (mg/g) </td><td>K₁</td><td>R²</td><td>q_e_._cal (mg/g) </td><td>K₂</td><td>R²</td></tr><tr><td> 5 10 20 40 </td><td> 23.8 45.0 78.2 144.2 </td><td> 2.34 3.48 5.74 8.48 </td><td> 0.03 0.04 0.04 0.03 </td><td> 0.779 0.780 0.956 0.930 </td><td> 19.6 23.25 20.00 166.67 </td><td> 0.02 0.02 0.01 0.01 </td><td> 0.999 0.997 0.994 0.990 </td></ Tr></TBODY></TABLE> Note: q _{e . Exp} (mg/g): the equilibrium adsorption capacity obtained in the actual experiment; q _{e . Cal} (mg/g): calculated equilibrium adsorption capacity according to the model

Referring first to Figure 7, Figure 8, and Table 1, according to the correlation coefficient R ² in the above model, the fitting degree of the pseudo second-order dynamics is better than the pseudo-first-order dynamics model, and according to the pseudo-second-order dynamics model. The qe value obtained is closer to the actual experimental data than the qe value obtained by the pseudo first-order kinetic model. Finally, the pseudo-second-kinetic model of the adsorption of copper ions by the aminated nanofibers in this experiment is more suitable than the pseudo-first-order kinetic model.

The Langmuir and Freundlich adsorption isotherms models were used to observe the size of the adsorption capacity. Langmuir model: Usually used to describe the adsorbate in a homogeneous solution, the surface of the adsorbent is relatively flat, and the adsorption site on the surface of the adsorbent can only be used once, that is, monolayer adsorption occurs. It can be expressed by the following equation: where qm represents the maximum adsorption capacity of aminated nanofibers for copper ions (mg/g); qe represents the ability of aminated nanofibers to adsorb copper ions in equilibrium (mg/g) ;Ce represents the copper ion concentration (mg / L) in equilibrium; b is the Langmuir adsorption constant (L / g). By setting the function of time C _e to C _e /q _e , the calculated value q _m and the reaction constant b can be obtained by the slope and intercept of the straight line. The result is shown in Fig. 9. The data and experiment calculated according to the Langmuir model. There is a big gap in the value, the experimental data is scattered on both sides of the curve, which can also be derived from R ² , and the fit is better than the Freundlich model. The correlation coefficient R ² is summarized in Table 2. Freundlich model: It is usually used to describe the adsorption of one-to-one adsorption of a monolayer, which is carried out in a multi-phase solution on the surface of the adsorbent, and can be expressed by the following formula: where q _e represents the equilibrium of the aminated naphthalene The adsorption capacity of rice fiber for copper ions (mg/g); C _e represents the copper ion concentration (mg/L) in equilibrium; n and K _F are Freundlich adsorption constants. By setting the function of TimeLogC _e to Logq _e , the adsorption constants n and K _F values can be obtained by the slope and intercept of the straight line. As a result, as shown in FIG. 10, the correlation coefficient R ² is also summarized in Table 2. Table 2 Comparison of Langmuir model and Freundlich model analysis results<TABLE border="1"borderColor="#000000"width="85%"><TBODY><tr><td> Langmuir coefficients <img wi="145" he= "32"file="02_image009.jpg"img-format="jpg"></img></td><td> Freundlich coefficient <img wi="145"he="52"file="02_image009.jpg"Img-format="jpg"></img></td></tr><tr><td>q_m(mg/g) b(L g^-1)R²</td><td>K_F (mg/g) n R²</td></ Tr><tr><td> 166.7 3.17 0.821 </td><td> 0.001 0.498 0.960 </td></tr></TBODY></TABLE>

In summary, as shown in Table 2 and Figure 9, it can be clearly seen that the data analyzed by the Freundlich model has a good fit to the experimental values, and the adsorption of copper ions by the aminated nanofibers is not a single The one-to-one adsorption of the molecular layer is carried out in a multiphase solution in which the adsorbate is on the surface of the adsorbent. Therefore, according to the higher R ² value obtained by the Freundlich model, the Freundlich model for the adsorption of copper ions in the experimental aminated nanofibers can better describe the experimental adsorption behavior than the Langmuir model.

The invention discloses the PAN nanofiber prepared by the single-needle electrospinning technology, and is modified and aminated by DETA, and then analyzed the characteristics of the nanofiber before and after modification by using FTIR, SEM and XRD, and confirmed in the optimum condition. It can adsorb heavy metal copper ions in 90% aqueous solution. From the FTIR analysis, it was found that the APAN nanofibers obtained sufficient amine-based modification; it was confirmed from the SEM analysis that the fiber diameter of the aminated APAN nanofiber structure was thickened by the amine group on the surface, and further The pH value of the solution also has a significant effect on the adsorption of APAN nanofibers, and the weakly acidic solution environment is more suitable for adsorbing copper ions. By using the Langmuir and Freundlich models to study the adsorption mechanism, it is found that the Freundlich model has better consistency with the experimental data of this experiment, and proves the feasibility of the nanofibers produced by the method of the present invention for the adsorption treatment of copper ions.

<Single-needle type electrospinning device>
A‧‧‧High voltage power supply
B‧‧‧Wire nozzle
C‧‧‧ Collector
D‧‧‧ polymer solution

1 is a flow chart of a preferred embodiment of the present invention.

2 is a scanning electron micrograph of PAN polyacrylonitrile nanofibers and APAN aminated polyacrylonitrile nanofibers.

Figure 3 is a comparison of FTIR spectra of PAN polyacrylonitrile nanofibers and APAN aminated polyacrylonitrile nanofibers.

Figure 4 is a comparison of XRD of PAN polyacrylonitrile nanofibers with APAN aminated polyacrylonitrile nanofibers.

Fig. 5 is a schematic diagram showing the comparison of Cu ²⁺ adsorption efficiency between PAN polyacrylonitrile nanofibers and APAN aminated polyacrylonitrile nanofibers.

Figure 6 is a graph showing the change in concentration of Cu ²⁺ by adsorption of the product of the preferred embodiment of the present invention under different pH conditions.

Fig. 7 is a schematic diagram showing the adsorption results of the product of the preferred embodiment of the present invention by a pseudo first-order kinetic model regression analysis.

Fig. 8 is a schematic diagram showing the adsorption results of the product pseudo second-order dynamics model of the preferred embodiment of the present invention.

Figure 9 is a schematic diagram showing the results of adsorption analysis of the product of the preferred embodiment of the present invention by the Langmuir model.

Figure 10 is a schematic diagram showing the results of regression analysis of the product Freundlich model of the preferred embodiment of the present invention.

Figure 11 is a schematic view of an electrospinning device.

Claims (8)

A method for producing a fibrous structure having a function of adsorbing copper ions, the method comprising: A. preparing a polyacrylonitrile nanofiber (PAN) by a single needle electrospinning technique; and B. the polyacrylonitrile nanofiber ( PAN) Surface modification with diethylenetriamine (DETA) reagent to form monoaminated polyacrylonitrile nanofibers (APAN). The method of claim 1, wherein the step A. comprises: (a) preparing a polymer homogenous solution comprising polyacrylonitrile and dimethylacetamide (DMAc) solvent; And (b) converting the polymer homogeneous solution into the polyacrylonitrile nanofiber (PAN) by an electrospinning device. The method of claim 2, wherein the concentration of the polymer homogeneous solution disposed in the step (a) is 6 wt%. The method of claim 1, wherein the step A is in a voltage range of 16 kV to 20 kV, the distance between the collector and the spinneret is 14 cm to 16 cm, and the collection rotation is between 20 and 30 cm sec ^-1 . Performed under parameter conditions. The method of claim 1, wherein the step B. comprises: (a) preparing a diethylenetriamine solution comprising ultrapure water, diethylenetriamine (DETA), and carbonic acid. (b) reacting the polyacrylonitrile nanofiber (PAN) in the diethylenetriamine solution; and (c) changing the color of the polyacrylonitrile nanofiber (PAN) to orange, Aminated polyacrylonitrile nanofibers (APAN) were obtained. The method according to claim 5, wherein the step (c) is carried out in a temperature environment of 373 K to 423 K, and the reaction time is 3 to 5 hours. A fibrous structure having a function of adsorbing copper ions prepared according to the method described in claim 1 of the patent application, comprising: a reticular fiber layer interwoven by a plurality of nanofibers, wherein each of the nanofibers The diameter range is 200 to 600 nm; and a surface layer is provided on the surface of the network fiber layer, characterized in that the surface layer has a complex amine group or a complex amido group. The fiber structure of claim 7, wherein the fiber structure is an amorphous structure.