CN111018037B - Method for removing heavy metal mercury ions in water based on polyacrylonitrile nano-film compound - Google Patents
Method for removing heavy metal mercury ions in water based on polyacrylonitrile nano-film compound Download PDFInfo
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
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- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
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Abstract
The invention relates to a method for removing heavy metal mercury ions in water based on a polyacrylonitrile nano film compound, which comprises the following steps: (1) taking polyacrylonitrile powder to prepare a polyacrylonitrile filter membrane; (2) soaking the polyacrylonitrile filter membrane in NaOH solution to obtain a carboxylated polyacrylonitrile filter membrane; (3) placing the carboxylated polyacrylonitrile filter membrane into deionized water, dripping a ferrous salt precursor solution under the stirring condition, performing ultrasonic treatment, aging, filtering, washing and drying to obtain a polyacrylonitrile-ferric oxide composite film; (4) the polyacrylonitrile-ferric oxide composite film is used as a filtering and adsorbing film, and the water body to be treated passes through the filtering and adsorbing film at a constant speed, so that the heavy metal mercury ions in the water body are removed. Compared with the prior art, the invention can realize high-efficiency membrane filtration and adsorption of heavy metal ions, and obtain higher adsorption efficiency and cyclic use performance.
Description
Technical Field
The invention belongs to the technical field of water pollution treatment, and relates to a method for removing heavy metal mercury ions in water based on a polyacrylonitrile nano film compound.
Background
Heavy metal pollution brings great harm to ecological environment and human health, and is one of the most important world environmental problems. In order to cope with the increasingly serious heavy metal pollution, researchers have developed various treatment methods to treat various heavy metal ions. The adsorption method has the advantages of small equipment investment, simple operation, high adsorption efficiency and large saturated adsorption capacity, and thus becomes a hot spot for research and application in recent years. Various adsorbent materials have respective characteristics, exert respective unique adsorption effects, and the common adsorption methods are mainly divided into physical adsorption and chemical adsorption according to the adsorption mechanism.
The physical adsorption is characterized in that the high specific surface area has better adsorption capacity to heavy metal ions, such as porous carbon and the like of porous structural materials, the porous materials can play a role in providing a main reaction site, communicating pore structures and enhancing diffusion in a liquid phase reaction environment, and the high specific surface area and the proper mesopores provide rich surface modification and functionalization sites. Adsorption is performed by van der waals interaction between the considerable inner surface of the porous material and the heavy metal ions. The physical adsorption method has the characteristics of simple preparation of the adsorbent, low cost and the like, but the problems of long adsorption period, difficult recovery of treated products, secondary pollution and the like exist in single physical adsorption. The chemical adsorption is mainly to adsorb heavy metals by using chemical reactions of adsorbents or chemical effects of complexing effect of the adsorbents and the adsorbed heavy metal ions. The chemical adsorbent is typically represented by metal oxide, and by utilizing the functional group of the metal oxide, the complexing effect and surface coordination can be carried out on heavy metal ions, so that higher adsorption capacity is achieved.
On the basis of the research, in order to take the adsorption efficiency and the saturation adsorption capacity of the adsorbent into consideration, scientific researchers explore the combination of physical adsorption and chemical adsorption to prepare a more efficient compound adsorbent. Although the physical and chemical synergistic carbon-based composite adsorbent can combine the advantages of the two in the aspects of adsorption rate and saturated adsorption capacity, the adsorbent is poor in recoverability, adsorption products are not easy to treat, and the recycling efficiency of the adsorbent is low. In addition, the research is also limited to the solution with a narrow original heavy metal concentration range, and the difference of the solution with the heavy metal concentration standard (0.05-0.1 mg L-1) of the water for practical production and living still has an order of magnitude. The traditional adsorbent has poor recycling performance mainly because most of carbon-based adsorbents are powdery and are dispersed in a solution for adsorption, and products after adsorption are difficult to recover and intensively treat.
Chinese patent ZL201610883839.3 discloses a preparation method of a zero-valent nano iron-based polyacrylonitrile membrane composite material, which is prepared by steps of hydrophilic membrane preparation, functional membrane modification, a liquid phase reduction method and the like. Although the composite material for heavy metal pollution treatment can be prepared, the composite material has the defects of complex raw materials, high cost, low stability of the preparation process and the like.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a method for removing heavy metal mercury ions in water based on a polyacrylonitrile nano film compound, which is based on a high-molecular polymer film and takes the in-situ growth of metal oxide nano particles as an adsorption active substance, is applied to the field of water treatment for removing the heavy metal ions in water, can realize high-efficiency film filtration and adsorption of the heavy metal ions, and obtains higher adsorption efficiency and recycling performance.
The purpose of the invention can be realized by the following technical scheme:
a method for removing heavy metal mercury ions in water based on a polyacrylonitrile nano-film compound comprises the following steps:
(1) taking polyacrylonitrile powder to prepare a polyacrylonitrile filter membrane;
(2) soaking the polyacrylonitrile filter membrane in NaOH solution to obtain a carboxylated polyacrylonitrile filter membrane;
(3) placing the carboxylated polyacrylonitrile filter membrane into deionized water, dripping a ferrous salt precursor solution under the stirring condition, performing ultrasonic treatment, aging, filtering, washing and drying to obtain a polyacrylonitrile-ferric oxide composite film;
(4) the polyacrylonitrile-ferric oxide composite film is used as a filtering and adsorbing film, and the water body to be treated passes through the filtering and adsorbing film at a constant speed, so that the heavy metal mercury ions in the water body are removed.
Further, in the step (1), the preparation process of the polyacrylonitrile filter membrane is as follows:
dissolving polyacrylonitrile powder in N, N-dimethylformamide, and stirring at 70 ℃ for 8h to form PAN casting liquid; and then statically defoaming at room temperature for 12h, pouring the defoamed PAN casting liquid on a glass plate, and immediately immersing the glass plate into a water condensation bath to obtain the polyacrylonitrile ultrafiltration membrane.
Further, the concentration of the obtained PAN casting fluid was 18 wt%.
Furthermore, the concrete process conditions of the water-solidifying bath are as follows: and treating for 24 hours at the treatment temperature of 25 +/-2 ℃ in a deionized water environment.
Further, in the step (2), the concentration of the NaOH solution is 2 mol/L;
the soaking conditions are specifically as follows: soaking at 50 deg.C for 3 h.
Further, in the step (3), the ferrous salt precursor solution is FeSO4And (3) solution.
Further, in the step (3), the amount of the dropwise added ferrite precursor solution satisfies the following conditions: the mass ratio of PAN to Fe is 2.5-10: 1.
Further, in the step (3), the stirring, ultrasonic treatment and aging treatment processes are as follows: stirring for 1-2h, performing ultrasonic treatment for 30min, and standing for 12 h.
Further, in the step (4), the concentration of mercury ions in the water body to be treated is 1 mg/L.
Further, in the step (4), the filtration adsorption membrane is arranged in a syringe type filtration cylinder body, and the filter is obtained, wherein the inner diameter of the syringe type filtration cylinder body is 25 mm.
Further, the speed of the water body to be treated passing through the filtering and adsorbing membrane is 2.5 mL/min.
The invention takes a polyacrylonitrile ultrafiltration membrane as a matrix, performs carboxylation treatment, and prepares the polyacrylonitrile-ferric oxide nano composite material by dipping ferrous sulfate precursor solution. Because the surface of the carboxylated polyacrylonitrile film has a large number of carboxyl and hydroxyl functional groups, the method is favorable for the in-situ growth of iron oxide nano particles on the surface of the polyacrylonitrile film, improves the adsorption activity, and realizes high-efficiency film filtration by cooperating with the physical adsorption and the chemical activity adsorption with high specific surface area.
Compared with the conventional method of adopting zero-valent nano iron as a composite phase of polyacrylonitrile, the method adopts iron oxide nano particles as the composite phase, the iron oxide is the most stable form of an iron compound and is not easy to change in quality, and the iron oxide is interacted with the polyacrylonitrile through oxygen-containing functional groups, so that the binding force is strong and the stability is high. The iron oxide nanoparticles have high activity and higher adsorption activity on heavy metal ions. Moreover, the preparation process of the iron oxide-based polyacrylonitrile film compound is simple, convenient and easy to operate, low in energy consumption, free of pollution, and economical and environment-friendly. In addition, the method has the advantages of low cost, environmental friendliness, high adsorption efficiency, stable cyclic use performance and great significance for heavy metal pollution treatment.
The polyacrylonitrile film is easy to process and modify due to its own characteristics, can form a film, and has various active groups, so that the polyacrylonitrile film can be conveniently and effectively combined with other adsorption active substances such as metal oxides to improve the adsorption performance. Meanwhile, the film forming property of the adsorption material can change the heavy metal removal from the traditional 'dispersion type' adsorption to the 'filtration type' adsorption, so that the effective breakthrough of the adsorption mode is realized. The biological polymer has biodegradability and is a green resource. Many traditional carbonaceous adsorbents are extracted from biomass precursors through treatments such as calcination, etc., and the polyacrylonitrile polymer is directly used as an adsorbent, has more functional groups, inherits and retains the structure of a high polymer, saves the calcination treatment step, and has the characteristics of low cost, simplicity and high efficiency.
In the treatment process, the addition of each treatment raw material (such as the quality of ferrous sulfate), treatment process parameters (such as NaOH soaking temperature, concentration and the like) and the like are further limited, and from the view point of action mechanism, because the addition of the ferrous sulfate is too low, the content of iron oxide in the final compound is low, and the adsorption activity is reduced; if the addition amount of the ferrous sulfate is too high, the ferric oxide is compounded and supersaturated, so that the phenomenon that the nano particles on the surface of the compound are not uniformly distributed and even compounded and unstable is caused, and the adsorption efficiency is also reduced; the reasonable ferrous sulfate addition enables the iron oxide nanoparticles generated in situ to be stably combined on the surface of polyacrylonitrile, so that higher adsorption activity is brought. In the limitation of the processing technological parameters, the polyacrylonitrile substrate structure or surface groups can be changed due to the overhigh soaking temperature, overhigh concentration or overlong soaking time of NaOH, and the polyacrylonitrile substrate cannot be completely carboxylated due to the overlow soaking temperature, low concentration or short soaking time.
In addition, in the preparation process of the polyacrylonitrile filter membrane, polyacrylonitrile powder is subjected to dissolution, heating and stirring to form a casting liquid, so that the PAN dispersion liquid is homogenized and the operation is easy; static defoaming is carried out for 12h to remove bubbles, so that the prepared polyacrylonitrile film has a complete structure and stronger mechanical property; and the water bath treatment is carried out for 24h, so that the formed polyacrylonitrile film is completely separated from the glass plate to form the polyacrylonitrile film.
Compared with the prior art, the invention has the following advantages:
(1) compared with common powder dispersion type adsorbents, the high molecular polymer film adsorbent has better adsorption efficiency and recycling performance, and can realize efficient film filtration and adsorption of heavy metal ions by combining the porous structure of an organic polymer and active substances and functional groups with rich surfaces.
(2) The composite phase used in the invention is the iron oxide nanophase with higher adsorption activity and stability, is simpler and more convenient to operate in the preparation process, has low energy consumption and no pollution, and has economic and environmental protection properties.
Drawings
FIG. 1 is a schematic diagram of preparation and application of a polyacrylonitrile-iron oxide nano-film composite;
FIG. 2 is a scanning electron micrograph of the polyacrylonitrile-iron oxide nano-film composite obtained in example 1, the front of the film;
FIG. 3 is a scanning electron micrograph of the polyacrylonitrile-iron oxide nano-film composite obtained in example 1, the reverse side of the film;
FIG. 4 is a scanning electron micrograph of the polyacrylonitrile-iron oxide nano-film composite obtained in example 1, which is a film section;
FIG. 5 is a scanning electron micrograph of the pure polyacrylonitrile nano-film obtained in example 5, the front of the film;
FIG. 6 is a scanning electron micrograph of the pure polyacrylonitrile nano film obtained in example 5, the reverse side of the film;
FIG. 7 is a scanning electron micrograph of the pure polyacrylonitrile nano-film obtained in example 5, which is a film cross-section.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.
In the following examples, unless otherwise specified, the starting materials or treatment techniques are all conventional and commercially available in the art.
Example 1
A method for removing heavy metal mercury ions in water based on a polyacrylonitrile nano-film compound comprises the following steps:
dissolving polyacrylonitrile powder in N, N-Dimethylformamide (DMF), stirring at 70 ℃ for 8 hours to form 18wt. (18 wt%) of casting liquid, statically defoaming at room temperature for 12 hours, pouring the PAN solution (i.e. the defoamed casting liquid) on a glass plate, wherein the height of a blade (i.e. the thickness of the glass plate) of the PAN solution is 200 mu m, and immediately immersing the PAN solution in a water condensation bath to obtain a polyacrylonitrile ultrafiltration membrane;
soaking the polyacrylonitrile ultrafiltration membrane in 2mol/L NaOH solution at 50 ℃ for 3h, and performing carboxylation through hydrolysis to generate carboxyl functional groups on the membrane surface;
placing the carboxylated polyacrylonitrile ultrafiltration membrane into deionized water, and mixing the materials in a mass ratio of PAN: fe-5: 1, dropwise adding FeSO while stirring4Continuing stirring the precursor solution for 1-2h, performing ultrasonic treatment for 30min, standing the mixed solution for 12h, and washing and drying the compound to obtain a polyacrylonitrile-iron oxide composite film;
step four, taking the polyacrylonitrile-iron oxide composite film as a filtering and adsorbing film, and preparing the film filter by adopting a syringe type filter and accessory installation (namely, directly installing the filtering and adsorbing film in a filtering cavity of the syringe type filter and separating the filtering cavity into two parts), wherein the diameter (inner diameter) of the syringe type filter is 25mm, the thickness of the filtering and adsorbing film is about 0.22 mu m, and a simple filtering device is built by connecting a peristaltic pump;
connecting one end of the filter with the original Hg2+One end of the solution is connected with a container for collecting liquid, membrane filtration and adsorption are carried out under the constant-speed liquid feeding of a peristaltic pump, and filtered original Hg is adsorbed2+The concentration of the solution is 1mg/L, and the constant liquid feeding speed is 2.5 mL/min. The adsorption experiment environment conditions are that the pH is 7 and the temperature is 25 +/-0 ℃.
The polyacrylonitrile-iron oxide composite film can reach the equilibrium adsorption rate of 98.5 percent by adsorbing mercury ions under the conditions, and the use time is 6 hours. After recycling for 4 times, the adsorption rate was 58%.
Example 2
A method for removing heavy metal mercury ions in water based on a polyacrylonitrile nano-film compound comprises the following steps:
dissolving polyacrylonitrile powder in N, N-Dimethylformamide (DMF), stirring at 70 ℃ for 8 hours to form 18wt. casting liquid, statically defoaming at room temperature for 12 hours, pouring the PAN solution on a glass plate, wherein the blade height of the PAN solution is 200 mu m, and immediately immersing the PAN solution in a water condensation bath to obtain a polyacrylonitrile ultrafiltration membrane;
soaking the polyacrylonitrile ultrafiltration membrane in 2mol/L NaOH solution at 50 ℃ for 3h, and performing carboxylation through hydrolysis to generate carboxyl functional groups on the membrane surface;
placing the carboxylated polyacrylonitrile ultrafiltration membrane into deionized water, and mixing the materials in a mass ratio of PAN: fe 2.5:1, stirring while adding dropwise FeSO4Continuing stirring the precursor solution for 1-2h, performing ultrasonic treatment for 30min, standing the mixed solution for 12h, and washing and drying the compound to obtain a polyacrylonitrile-iron oxide composite film;
step four, taking the polyacrylonitrile-ferric oxide composite film as a filtering adsorption film, preparing a film filter by installing a syringe filter and accessories, wherein the diameter (inner diameter) of the syringe filter is 25mm, the thickness of the film is about 0.22 mu m, and connecting a peristaltic pump to build a simple filtering device;
connecting one end of the filter with the original Hg2+One end of the solution is connected with a container for collecting liquid and is fed at a constant speed by a peristaltic pumpPerforming membrane filtration adsorption under liquid to adsorb the filtered original Hg2+The concentration of the solution is 1mg/L, and the constant liquid feeding speed is 2.5 mL/min. The adsorption experiment environment conditions are that the pH is 7 and the temperature is 25 +/-0 ℃.
The polyacrylonitrile-iron oxide composite film can reach an equilibrium adsorption rate of 97.0 percent by adsorbing mercury ions under the conditions.
Example 3
A method for removing heavy metal mercury ions in water based on a polyacrylonitrile nano-film compound comprises the following steps:
dissolving polyacrylonitrile powder in N, N-Dimethylformamide (DMF), stirring at 70 ℃ for 8 hours to form 18wt. casting liquid, statically defoaming at room temperature for 12 hours, pouring the PAN solution on a glass plate, wherein the blade height of the PAN solution is 200 mu m, and immediately immersing the PAN solution in a water condensation bath to obtain a polyacrylonitrile ultrafiltration membrane;
soaking the polyacrylonitrile ultrafiltration membrane in 2mol/L NaOH solution at 50 ℃ for 3h, and performing carboxylation through hydrolysis to generate carboxyl functional groups on the membrane surface;
placing the carboxylated polyacrylonitrile ultrafiltration membrane into deionized water, and mixing the materials in a mass ratio of PAN: fe 7.5:1, stirring while adding dropwise FeSO4Continuing stirring the precursor solution for 1-2h, performing ultrasonic treatment for 30min, standing the mixed solution for 12h, and washing and drying the compound to obtain a polyacrylonitrile-iron oxide composite film;
step four, taking the polyacrylonitrile-ferric oxide composite film as a filtering adsorption film, preparing a film filter by installing a syringe filter and accessories, wherein the diameter (inner diameter) of the syringe filter is 25mm, the thickness of the film is about 0.22 mu m, and connecting a peristaltic pump to build a simple filtering device;
connecting one end of the filter with the original Hg2+One end of the solution is connected with a container for collecting liquid, membrane filtration and adsorption are carried out under the constant-speed liquid feeding of a peristaltic pump, and filtered original Hg is adsorbed2+The concentration of the solution is 1mg/L, and the constant liquid feeding speed is 2.5 mL/min. The adsorption experiment environment conditions are that the pH is 7 and the temperature is 25 +/-0 ℃.
The polyacrylonitrile-iron oxide composite film can reach 96.6% of equilibrium adsorption rate by adsorbing mercury ions under the conditions.
Example 4
A method for removing heavy metal mercury ions in water based on a polyacrylonitrile nano-film compound comprises the following steps:
dissolving polyacrylonitrile powder in N, N-Dimethylformamide (DMF), stirring at 70 ℃ for 8 hours to form 18wt. casting liquid, statically defoaming at room temperature for 12 hours, pouring the PAN solution on a glass plate, wherein the blade height of the PAN solution is 200 mu m, and immediately immersing the PAN solution in a water condensation bath to obtain a polyacrylonitrile ultrafiltration membrane;
soaking the polyacrylonitrile ultrafiltration membrane in 2mol/L NaOH solution at 50 ℃ for 3h, and performing carboxylation through hydrolysis to generate carboxyl functional groups on the membrane surface;
placing the carboxylated polyacrylonitrile ultrafiltration membrane into deionized water, and mixing the materials in a mass ratio of PAN: fe 10:1, stirring while adding dropwise FeSO4Continuing stirring the precursor solution for 1-2h, performing ultrasonic treatment for 30min, standing the mixed solution for 12h, and washing and drying the compound to obtain a polyacrylonitrile-iron oxide composite film;
step four, taking the polyacrylonitrile-ferric oxide composite film as a filtering adsorption film, preparing a film filter by installing a syringe filter and accessories, wherein the diameter (inner diameter) of the syringe filter is 25mm, the thickness of the film is about 0.22 mu m, and connecting a peristaltic pump to build a simple filtering device;
connecting one end of the filter with the original Hg2+One end of the solution is connected with a container for collecting liquid, membrane filtration and adsorption are carried out under the constant-speed liquid feeding of a peristaltic pump, and filtered original Hg is adsorbed2+The concentration of the solution is 1mg/L, and the constant liquid feeding speed is 2.5 mL/min. The adsorption experiment environment conditions are that the pH is 7 and the temperature is 25 +/-0 ℃.
The polyacrylonitrile-iron oxide composite film can reach 96.9% of equilibrium adsorption rate by adsorbing mercury ions under the conditions.
Example 5
A method for removing heavy metal mercury ions in water based on a polyacrylonitrile nano-film compound comprises the following steps:
dissolving polyacrylonitrile powder in N, N-Dimethylformamide (DMF), stirring at 70 ℃ for 8 hours to form 18wt. casting liquid, statically defoaming at room temperature for 12 hours, pouring the PAN solution on a glass plate, wherein the blade height of the PAN solution is 200 mu m, and immediately immersing the PAN solution in a water condensation bath to obtain a polyacrylonitrile ultrafiltration membrane;
soaking the polyacrylonitrile ultrafiltration membrane in 2mol/L NaOH solution at 50 ℃ for 3h, performing carboxylation through hydrolysis to generate carboxyl functional groups on the membrane surface, and then washing and drying;
step three, taking a polyacrylonitrile film as a filtering adsorption film, preparing a film filter by installing a syringe type filter and accessories, wherein the diameter (inner diameter) of the syringe type filter is 25mm, the thickness of the film is about 0.22 mu m, and connecting a peristaltic pump to build a simple filtering device;
step four, connecting one end of the filter with the original Hg2+One end of the solution is connected with a container for collecting liquid, membrane filtration and adsorption are carried out under the constant-speed liquid feeding of a peristaltic pump, and filtered original Hg is adsorbed2+The concentration of the solution is 1mg/L, and the constant liquid feeding speed is 2.5 mL/min. The adsorption experiment environment conditions are that the pH is 7 and the temperature is 25 +/-0 ℃.
The polyacrylonitrile-iron oxide composite film can reach an equilibrium adsorption rate of 62.9% by adsorbing mercury ions under the conditions.
Example 6
A method for removing heavy metal mercury ions in water based on a polyacrylonitrile nano-film compound comprises the following steps:
dissolving polyacrylonitrile powder in N, N-Dimethylformamide (DMF), stirring at 70 ℃ for 8 hours to form 18wt. casting liquid, statically defoaming at room temperature for 12 hours, pouring the PAN solution on a glass plate, wherein the blade height of the PAN solution is 200 mu m, and immediately immersing the PAN solution in a water condensation bath to obtain a polyacrylonitrile ultrafiltration membrane;
soaking the polyacrylonitrile ultrafiltration membrane in 2mol/L NaOH solution at 50 ℃ for 3h, and performing carboxylation through hydrolysis to generate carboxyl functional groups on the membrane surface;
step three, placing the carboxylated polyacrylonitrile ultrafiltration membrane into deionizationIn water, PAN: fe-5: 1, dropwise adding FeSO while stirring4Continuing stirring the precursor solution for 1-2h, performing ultrasonic treatment for 30min, standing the mixed solution for 12h, and washing and drying the compound to obtain a polyacrylonitrile-iron oxide composite film;
step four, taking the polyacrylonitrile-ferric oxide composite film as a filtering adsorption film, preparing a film filter by installing a syringe filter and accessories, wherein the diameter (inner diameter) of the syringe filter is 25mm, the thickness of the film is about 0.22 mu m, and connecting a peristaltic pump to build a simple filtering device;
connecting one end of the filter with the original Hg2+One end of the solution is connected with a container for collecting liquid, membrane filtration and adsorption are carried out under the constant-speed liquid feeding of a peristaltic pump, and filtered original Hg is adsorbed2+The concentration of the solution is 1mg/L, and the constant liquid feeding speed is 2.5 mL/min. The adsorption experiment environment conditions are that the pH is 3 and the temperature is 25 +/-0 ℃.
The polyacrylonitrile-iron oxide composite film can reach an equilibrium adsorption rate of 41.1% by adsorbing mercury ions under the above conditions.
Example 7
A method for removing heavy metal mercury ions in water based on a polyacrylonitrile nano-film compound comprises the following steps:
dissolving polyacrylonitrile powder in N, N-Dimethylformamide (DMF), stirring at 70 ℃ for 8 hours to form 18wt. casting liquid, statically defoaming at room temperature for 12 hours, pouring the PAN solution on a glass plate, wherein the blade height of the PAN solution is 200 mu m, and immediately immersing the PAN solution in a water condensation bath to obtain a polyacrylonitrile ultrafiltration membrane;
soaking the polyacrylonitrile ultrafiltration membrane in 2mol/L NaOH solution at 50 ℃ for 3h, and performing carboxylation through hydrolysis to generate carboxyl functional groups on the membrane surface;
placing the carboxylated polyacrylonitrile ultrafiltration membrane into deionized water, and mixing the materials in a mass ratio of PAN: fe-5: 1, dropwise adding FeSO while stirring4Continuing stirring the precursor solution for 1-2h, performing ultrasonic treatment for 30min, standing the mixed solution for 12h, and washing and drying the compound to obtain a polyacrylonitrile-iron oxide composite film;
step four, taking the polyacrylonitrile-ferric oxide composite film as a filtering adsorption film, preparing a film filter by installing a syringe filter and accessories, wherein the diameter (inner diameter) of the syringe filter is 25mm, the thickness of the film is about 0.22 mu m, and connecting a peristaltic pump to build a simple filtering device;
connecting one end of the filter with the original Hg2+One end of the solution is connected with a container for collecting liquid, membrane filtration and adsorption are carried out under the constant-speed liquid feeding of a peristaltic pump, and filtered original Hg is adsorbed2+The concentration of the solution is 1mg/L, and the constant liquid feeding speed is 2.5 mL/min. The adsorption experiment environment conditions are that the pH is 5 and the temperature is 25 +/-0 ℃.
The polyacrylonitrile-iron oxide composite film can reach an equilibrium adsorption rate of 65.3 percent by adsorbing mercury ions under the conditions.
Example 8
A method for removing heavy metal mercury ions in water based on a polyacrylonitrile nano-film compound comprises the following steps:
dissolving polyacrylonitrile powder in N, N-Dimethylformamide (DMF), stirring at 70 ℃ for 8 hours to form 18wt. casting liquid, statically defoaming at room temperature for 12 hours, pouring the PAN solution on a glass plate, wherein the blade height of the PAN solution is 200 mu m, and immediately immersing the PAN solution in a water condensation bath to obtain a polyacrylonitrile ultrafiltration membrane;
soaking the polyacrylonitrile ultrafiltration membrane in 2mol/L NaOH solution at 50 ℃ for 3h, and performing carboxylation through hydrolysis to generate carboxyl functional groups on the membrane surface;
placing the carboxylated polyacrylonitrile ultrafiltration membrane into deionized water, and mixing the materials in a mass ratio of PAN: fe-5: 1, dropwise adding FeSO while stirring4Continuing stirring the precursor solution for 1-2h, performing ultrasonic treatment for 30min, standing the mixed solution for 12h, and washing and drying the compound to obtain a polyacrylonitrile-iron oxide composite film;
step four, taking the polyacrylonitrile-ferric oxide composite film as a filtering adsorption film, preparing a film filter by installing a syringe filter and accessories, wherein the diameter (inner diameter) of the syringe filter is 25mm, the thickness of the film is about 0.22 mu m, and connecting a peristaltic pump to build a simple filtering device;
connecting one end of the filter with the original Hg2+One end of the solution is connected with a container for collecting liquid, membrane filtration and adsorption are carried out under the constant-speed liquid feeding of a peristaltic pump, and filtered original Hg is adsorbed2+The concentration of the solution is 1mg/L, and the constant liquid feeding speed is 2.5 mL/min. The adsorption experiment environment conditions are that the pH is 9 and the temperature is 25 +/-0 ℃.
The polyacrylonitrile-iron oxide composite film can reach an equilibrium adsorption rate of 94.5 percent by adsorbing mercury ions under the conditions.
Example 9
A method for removing heavy metal mercury ions in water based on a polyacrylonitrile nano-film compound comprises the following steps:
dissolving polyacrylonitrile powder in N, N-Dimethylformamide (DMF), stirring at 70 ℃ for 8 hours to form 18wt. casting liquid, statically defoaming at room temperature for 12 hours, pouring the PAN solution on a glass plate, wherein the blade height of the PAN solution is 200 mu m, and immediately immersing the PAN solution in a water condensation bath to obtain a polyacrylonitrile ultrafiltration membrane;
soaking the polyacrylonitrile ultrafiltration membrane in 2mol/L NaOH solution at 50 ℃ for 3h, and performing carboxylation through hydrolysis to generate carboxyl functional groups on the membrane surface;
placing the carboxylated polyacrylonitrile ultrafiltration membrane into deionized water, and mixing the materials in a mass ratio of PAN: fe-5: 1, dropwise adding FeSO while stirring4Continuing stirring the precursor solution for 1-2h, performing ultrasonic treatment for 30min, standing the mixed solution for 12h, and washing and drying the compound to obtain a polyacrylonitrile-iron oxide composite film;
step four, taking the polyacrylonitrile-ferric oxide composite film as a filtering adsorption film, preparing a film filter by installing a syringe filter and accessories, wherein the diameter (inner diameter) of the syringe filter is 25mm, the thickness of the film is about 0.22 mu m, and connecting a peristaltic pump to build a simple filtering device;
connecting one end of the filter with the original Hg2+One end of the solution is connected with a container for collecting liquid, membrane filtration and adsorption are carried out under the constant-speed liquid feeding of a peristaltic pump, and filtered original Hg is adsorbed2+The solution concentration is 1mg/L, and the solution is fed at constant speedThe rate of (2) was 2.5 mL/min. The adsorption experiment environment conditions are that the pH is 11 and the temperature is 25 +/-0 ℃.
The polyacrylonitrile-iron oxide composite film can reach 80.6% of equilibrium adsorption rate by adsorbing mercury ions under the conditions.
The polyacrylonitrile-iron oxide nano-film composite prepared in the example 1 is shown in fig. 2-4, and as can be seen from the front structure of the polyacrylonitrile-iron oxide nano-film composite in fig. 2, the generated iron oxide nano-particles grow in situ on the surface of the polyacrylonitrile in an agglomerated form; as can be seen from the reverse structure of the composite in fig. 3, the micropores on the back surface are partially covered and filled with the iron oxide nanoparticles; as can be seen from the cross-sectional structure of FIG. 4, the thickness of the film after compounding iron oxide is increased, and the porous multi-layer structure presented on the cross-section is irregular.
The pure polyacrylonitrile nano-film prepared in the example 5 is shown in fig. 5-7, and as can be seen from the front structure of the pure polyacrylonitrile nano-film in fig. 5, the pure polyacrylonitrile surface is a homogeneous nano-scale porous structure; as can be seen from the back side of the polyacrylonitrile film in FIG. 6, the aperture of the back side is larger than that of the front side and is 1-2 μm; as can be seen from the cross-sectional structure of the film shown in FIG. 7, the thickness of the pure polyacrylonitrile film is about 100 μm, and the substrate is a multi-layer structure. It is also verified that the films prepared in example 1 and example 5 are different from each other in that the composite film prepared in example 1 by combining iron oxide nanoparticles has a heterogeneous porous structure and has increased surface activity.
In addition, the adsorption performance data of the thin film composite membrane obtained in examples 1 to 9 for treating mercury ions in water are shown in table 1 below.
TABLE 1
| Test items | Example 1 | Example 2 | Example 3 | Example 4 | Example 5 |
| Equilibrium adsorption Rate (%) | 98.5 | 97.0 | 96.6 | 96.9 | 62.9 |
| Test items | Example 6 | Example 7 | Example 8 | Example 9 | |
| Equilibrium adsorption Rate (%) | 41.1 | 65.3 | 94.5 | 80.6 |
Examples 1-5 compare different PANs according to the data in table 1: influence of Fe element mass ratio on equilibrium adsorption ratio, PAN used in example 1: the mass ratio of Fe element is 5:1, the highest adsorption efficiency is achieved, and the adsorption activity of the compound is reduced due to the fact that the content of iron oxide is too low; if the addition amount of the iron oxide is too high, the composite phase can reach supersaturation, so that the phenomenon that the nano particles on the surface of the composite are not uniformly distributed and even composite is unstable is caused, and the adsorption efficiency can also be reduced. Example 5 is a pure polyacrylonitrile film without added iron oxide, the equilibrium adsorption rate is low, showing that the adsorption activity of the composite iron oxide nanoparticles to polyacrylonitrile is greatly improved. Examples 6-9 compare the effect of different pH conditions on the equilibrium adsorption rate under the adsorption test, in example 1, the adsorption efficiency is highest in a neutral environment with pH 7, while too low pH causes the Zeta potential on the surface of the composite to be in a positive charge state, which is very unfavorable for adsorbing mercury ions with both positive charges, and too high pH causes too many hydroxide ions in the solution environment, which are easy to combine with mercury ions to reduce the adsorption efficiency. The thin film composites prepared according to the invention are therefore stable under optimal conditions, namely PAN: the mass ratio of Fe element is 5:1, and the mercury ion adsorption efficiency is high at 98.5% under the environment of pH 7.
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (9)
1. A method for removing heavy metal mercury ions in water based on a polyacrylonitrile nano film compound is characterized by comprising the following steps:
(1) taking polyacrylonitrile powder to prepare a polyacrylonitrile filter membrane;
(2) soaking the polyacrylonitrile filter membrane in NaOH solution to obtain a carboxylated polyacrylonitrile filter membrane;
(3) placing the carboxylated polyacrylonitrile filter membrane into deionized water, dripping a ferrous salt precursor solution under the stirring condition, performing ultrasonic treatment, aging, filtering, washing and drying to obtain a polyacrylonitrile-ferric oxide composite film;
(4) taking a polyacrylonitrile-ferric oxide composite film as a filtering and adsorbing film, and enabling the water body to be treated to pass through the filtering and adsorbing film at a constant speed, so that the heavy metal mercury ions in the water body are removed;
in the step (3), the amount of the dropwise added ferrite precursor solution meets the following requirements: the mass ratio of PAN to Fe is 2.5-10: 1.
2. The method for removing heavy metal mercury ions in water based on polyacrylonitrile nano-film compound according to claim 1, wherein in the step (1), the preparation process of the polyacrylonitrile filter membrane is as follows:
dissolving polyacrylonitrile powder in N, N-dimethylformamide, and stirring at 70 ℃ for 8h to form PAN casting liquid; and then statically defoaming at room temperature for 12h, pouring the defoamed PAN casting liquid on a glass plate, and immediately immersing the glass plate into a water condensation bath to obtain the polyacrylonitrile ultrafiltration membrane.
3. The polyacrylonitrile nano-film composite based method for removing the heavy metal mercury ions in water as claimed in claim 2, wherein the concentration of the obtained PAN casting liquid is 18 wt%.
4. The method for removing heavy metal mercury ions in water based on polyacrylonitrile nano-film compound as claimed in claim 2, wherein the specific process conditions of the water-cooling bath are as follows: and treating for 24 hours at the treatment temperature of 25 +/-2 ℃ in a deionized water environment.
5. The method for removing the heavy metal mercury ions in the water based on the polyacrylonitrile nano film compound, as claimed in claim 1, wherein in the step (2), the concentration of the NaOH solution is 2 mol/L;
the soaking conditions are specifically as follows: soaking at 50 deg.C for 3 h.
6. The method for removing heavy metal mercury ions in water based on polyacrylonitrile nano-film compound as claimed in claim 1, wherein the steps are as follows(3) In (1), the ferrous salt precursor solution is FeSO4And (3) solution.
7. The method for removing heavy metal mercury ions in water based on polyacrylonitrile nano-film compound as claimed in claim 1, wherein in the step (3), the ultrasonic and aging treatment process specifically comprises: firstly carrying out ultrasonic treatment for 30min, and then standing for 12 h.
8. The method for removing heavy metal mercury ions in water based on polyacrylonitrile nano-film compound as claimed in claim 1, wherein in step (4), the concentration of mercury ions in the water body to be treated is 1 mg/L.
9. The polyacrylonitrile nano film composite based method for removing heavy metal mercury ions in water according to the claim 1, wherein in the step (4), the filtering and adsorbing membrane is arranged in a syringe type filtering cylinder body and a filter is obtained, and the inner diameter of the syringe type filtering cylinder body is 25 mm;
the speed of the water body to be treated passing through the filtering and adsorbing membrane is 2.5 mL/min.
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