KR20190010399A - Nanofiber membrane for mercury(ⅱ) adsorption, method for preparing using thereof and and applicatio thereof - Google Patents

Abstract

The present invention relates to a nano fiber membrane for mercury adsorption, a method of manufacturing the same and an application of the same. To be specifically, the present invention relates to the nano fiber membrane manufactured by using a polysulfide produced by an inverse vulcanization reaction of sulfur and hydrophilic comonomer, the method of manufacturing the same and the application of the same. In the present invention, the nano fiber membrane containing the polysulfide produced by an inverse vulcanization reaction of sulfur and hydrophilic comonomer has excellent mercury adsorption in water system, has a high mercury selectivity, is easy to process and can be reused repeatedly.

Description

TECHNICAL FIELD [0001] The present invention relates to a nanofiber membrane for mercury adsorption, a method of manufacturing the same, and an application thereof. [0002]

The present invention relates to a nanofiber membrane for mercury adsorption, a method for producing the nanofiber membrane, and a method for producing the same, and more particularly, to a nanofiber membrane for mercury adsorption, which is produced by using a polysulfide prepared by the reverse vulcanization reaction of sulfur and a hydrophilic comonomer, A method for producing the same, and an application technique therefor.

Mercury (Hg) is a toxic, biodegradable heavy metal, and the amount of mercury released into the environment has increased considerably due to anthropogenic activities such as fossil fuel combustion and mining. The mercury element (Hg ⁰ ) released to the atmosphere reacts with a naturally occurring oxidant such as bromine (Br) to form divalent form (Hg ^{2 +} ). This inorganic mercury produces methyl mercury, a potential neurotoxin that is concentrated at each stage of the food chain through methylation. Because of this adverse effect of mercury, the Minamata Convention of Mercury (2013) was adopted to protect human health and the environment from the threat of mercury worldwide.

Mercury treatment methods include plant purification, biological purification, adsorption and precipitation. Of these mercury processing methods, adsorption is known as a promising mercury processing method because it is inexpensive and has proven its efficacy in water treatment. Recently, it has been found that the thiol-functionalized porous aromatic framework (PAF-SH) is very effective in removing Hg ^{2 +} from an aqueous solution (uptake capacity 1000 mg g -1) . These 'nano-traps' are now regarded as benchmarks for adsorbents for mercury separation.

The PAF was synthesized by a method in which tetraquis (4-bromo-phenyl) methane and a phenyl ring were bonded to each other through a nickel-catalyzed cross-linking reaction. PAF-based nanotrapes show very high levels of mercury adsorption capacity, but they are expensive to apply to large-scale applications and are difficult to handle because they are in powder form and have the disadvantage of being difficult to recycle. Therefore, there is a need for research on alternative methods of adsorbing mercury efficiently.

Recently, Chung et al. (2013) disclosed a method for producing a high-content sulfur polymer through an inverse vulcanization reaction. The sulfur element S ₈ is then subjected to a ring opening polymerization (ROP) reaction followed by the addition of a base to a free-radical polymerization reaction with a divinylic comonomer such as 1,3-diisopropenylbenzene (DIB) Up to now have been heated to a temperature above the floor temperature (T _f = 159 ° C). To date, most of the inverse vulcanized polymers are lithium-sulfur batteries, high refractive index polymeric optics, In addition, Crockett et al. (2015) used styril-responsive polymeric systems and photocatalytic particles and semiconducting particles to cope with d-limonene, which is known to potentially remove lead and mercury. However, most of the reverse-vulcanized polymers have limited application to mercury separation due to the vitrified characteristic.

Korean Patent No. 10-1443718

The present invention provides a nanofiber membrane for mercury adsorption, which is produced by using a polysulfide prepared by an inverse vulcanization reaction of sulfur and a hydrophilic comonomer, a method for producing the nanofiber membrane, and an application technique therefor.

The present invention relates to a mercury adsorption method comprising the step of adding a polysulfide (PS) prepared by an inverse vulcanization reaction of a hydrophilic comonomer having sulfur and an acrylate group to a dope solution in which a polymer substance is mixed with a solvent, A method for producing a nanofiber membrane is provided.

Wherein the comonomer is selected from the group consisting of methacrylic acid, 2-carboxyethyl acrylate, diallyl maleate, and glycidyl methacrylate. And most preferably 2-carboxyethyl acrylic acid.

In the present invention, a comonomer means another monomer among the other monomers used as a raw material for the hybridization, when considering a monomer as a center.

The reverse vulcanization reaction may be carried out at 50 to 80 ° C for 3 to 5 hours, followed by cooling at room temperature for 3 to 5 hours. The room temperature may be between 1 and 35 ° C.

In the present invention, inverse vulcanization refers to the reaction of adding a small amount of a polymer chain to a large amount of sulfur, as opposed to a 'vulcanization' in which a small amount of sulfur is added to a polymer chain.

The sulfur and the hydrophilic comonomer can be reacted at a molar ratio of 1: 0.5 ~ 2.

The polymeric material may be selected from the group consisting of polyacrylonitrile, polysulfone, polyethersulfone, polyvinylidene fluoride, cellulose acetate, and polyvinyl chloride. And may include at least one selected. Most preferably polyacrylonitrile.

The solvent may include at least one member selected from the group consisting of dimethylformamide, dimethylformaldehyde, tetrahydrofuran, dimethylacetamide and methylpyrrolidone.

The dope solution in which the polymer material is mixed with the solvent may contain 5 to 15% by weight of the polymer material.

The polysulfide may be added in an amount of 100 to 200 parts by weight based on 100 parts by weight of the polymer material.

The present invention also relates to a mercury-adsorbing nano-particle (hereinafter, also referred to as " noble metal ") produced by adding a polysulfide (PS) prepared by inverse vulcanization reaction of a hydrophilic comonomer having an acrylate group and sulfur to a dope solution in which a polymer substance is mixed with a solvent, Fiber membrane.

The present invention also provides a mercury-adsorbing nanofiber membrane comprising a polysulfide (PS) and a polymer substance, wherein the polysulfide is prepared by an inverse vulcanization reaction of a hydrophilic comonomer having sulfur and an acrylate group to provide.

The polymeric material may be at least one selected from the group consisting of polyacrylonitrile, polysulfone, polyethersulfone, polyvinylidene fluoride, cellulose acetate, and polyvinyl chloride chloride, and the like. Most preferably polyacrylonitrile.

The present invention also provides a method for producing a polysulfide for mercury adsorption comprising a step of subjecting a hydrophilic comonomer having sulfur and an acrylate group to an inverse vulcanization reaction.

The present invention also provides a polysulfide for mercury adsorption formed by an inverse vulcanization reaction of a hydrophilic comonomer having sulfur and an acrylate group.

The hydrophilic comonomer may be selected from the group consisting of methacrylic acid, 2-carboxyethyl acrylate, diallyl maleate, and glycidyl methacrylate. And most preferably may be 2-carboxyethyl acrylic acid.

The present invention also provides a mercury adsorbent prepared by adding a polysulfide (PS) prepared by an inverse vulcanization reaction of a hydrophilic comonomer having sulfur and an acrylate group to a dope solution in which a polymer substance is mixed with a solvent and then electrospinning do.

The present invention also relates to a nanofiber mercury adsorbent comprising a polysulfide (PS) and a polymer substance, wherein the polysulfide is produced by an inverse vulcanization reaction of a hydrophilic comonomer having sulfur and an acrylate group Thereby providing an adsorbent.

The polymeric material may be selected from the group consisting of polyacrylonitrile, polysulfone, polyethersulfone, polyvinylidene fluoride, cellulose acetate, and polyvinyl chloride. And may include at least one selected. Most preferably polyacrylonitrile.

In addition, the present invention relates to a method for producing a mercury-adsorbing nanofiber membrane (hereinafter, referred to as " nanofiber membrane ") for mercury adsorption by adding a polysulfide (PS) prepared by inversely vulcanizing a hydrophilic comonomer having sulfur and an acrylate group to a dope solution containing a polymer substance mixed with a solvent, Lt; / RTI > And a step of adsorbing mercury from a solution containing mercury by using the membrane.

In the present invention, a nanofiber membrane including a polysulfide prepared by inverse vulcanization reaction of sulfur and a hydrophilic comonomer has excellent mercury adsorption ability in a water system, has high selectivity to mercury, is easy to process, and can be repeatedly used . In addition, most of the conventional reverse-vulcanized polymers have limited application to mercury separation due to their vitrification properties, but according to the present invention, this problem can be solved.

Figure 1 relates to Na ⁺ recovery of PS-PAN NM (deionized water pH adjustment with 1 M NaOH, V = 50 mL, m = 25 mg PS).
Figure 2 is a schematic view of a method of direct addition of CEA to S ₈ , (a) an optical image of the reaction process from the addition of elemental sulfur, CEA, to the formation of a black product with uniform viscosity, and (b) a schematic diagram of a process for forming a poly (Sr-CEA) from copolymerization of S _8.
Figure 3 relates to the FTIR spectra of poly (Sr-CEA) (poly (sulfur-random-carboxyethylacrylate) with CEA and S: CEA molar ratios.
Fig. 4 relates to an elemental analysis result of PS (S: CEA = 2: 1; 100 wt%).
FIG. 5 is a graph illustrating the oscillatory rheology of a PS sample with PS (a) S: CEA = 1: 2, (b) S: CEA = 1: It relates to the sample.
FIG. 6 shows the result of confirming the viscosity change of the polysulfide at S: CEA molar ratio according to the temperature.
FIG. 7 relates to the results of simultaneous thermal analysis of polysulfides at S: CEA molar ratios in a nitrogen atmosphere at a heating rate of 20 ml / min and 10 ° C / min.
Figure 8 shows poly (Sr-CEA) prepared using (a) melt electrospinning and (b) solution electrospinning using DMF as a solvent.
FIG. 9 is a graph showing the strength of carbon and sulfur in the polysulfide with S: CEA mole ratio according to binding energy. FIG. (a) 1: 2 (b) 1: 1 (c) 2: 1
Fig. 10 shows the result of confirming the contact angle of polysulfide with S: CEA molar ratio.
11 is a schematic diagram of a method for producing PS-PAN nanofibers by (a) a method of producing a polysulfide by a reverse vulcanization method according to the present invention, and (b) mixing a polysulfide and PAN.
Fig. 12 relates to SEM images (insertion degree: optical image) and fiber diameter distribution of PS-PAN nanofibers according to the amount of PS loading.
Figure 13 relates to (a) the nitrogen adsorption-desorption curves and (b) the mechanical properties of the nanofibers with respect to the amount of polysulfide loading.
Figure 14 relates to the effect of S: CEA molar ratio on adsorption capacity of polysulfides and nanofibers (C _o = 100 mg L ^-1 , pH = 5.4, T = 30 ° C, 150 rpm, 48 h).
Figure 15 relates to mercury adsorption capacity and% removal rate of PS by initial pH (S: CEA = 2: 1, 100 wt%, C _o = 100 mg L ^-1 , T = 30 属 C, 150 rpm, 48 h).
Figure 16 relates to the equilibrium adsorption capacity of PS-PAN NF with PS loading (S: CEA = 2: 1) (C _o = 100 mg L ^-1 , pH = 6, T = 30 ° C, 48h).
Figure 17 relates to adsorption isotherms of PS (a) q _e diagram of PS for the Langmuir and Prodrive isotherm constants and thermodynamic properties (C _o = 100-1000 mg L ^-1 , pH = 6, 150 rpm , 48h) (b) Langmuir equation (c) Prodrive equation.
Figure 18 relates to the adsorption isotherms for PS-NM PAN (a) Langmuir and pro Aldrich temperature of each PS-PAN NM for the isothermal constants and the thermodynamic properties q _e Table (C _o = 100-800 mg L ^{- 1} , pH = 6, 150 rpm, 48 h) (b) Langmuir equation (c) Prodrive equation.
Figure 19 relates to the spectroscopic characteristics of mercury-binding interactions. (A) FTIR spectra of PS-PAN NM before mercury adsorption (red) and after (black), (b) Before mercury adsorption and (c) -PAN NM shows the result of EDS mapping.
FIG. 20 shows the spectra of carbon, oxygen, sulfur and mercury constituting the PS-PAN NM before mercury adsorption and (b) the spectrum of the PS-PAN after the mercury adsorption, through the electron probe microanalysis (EPMA) Oxygen, sulfur and mercury constituting the NM.
FIG. 21 shows a Van Hope plot using mercury with C _o = 100-800 mg L ^-1 in a solution with pH = 6.0 and m = 25 mg PS.
Figure 22 shows the time profiles (C ₀ = 200 and 800 mg L ^-1 ; T = 30 ° C) for mercury adsorption at PS = PAN NM (S: CEA = 2: 1, 150% .
FIG. 23 is a graph showing the re-use ability of PS-PAN nanofiber as a mercury adsorbent. (A) eluent (C ₀ = 800 mg L ^-1 , V = 50 mL); (b) HCl concentration optimization; (c) adsorption-desorption cycle performance of PS-PAN nanofibers.

Hereinafter, the present invention will be described in more detail with reference to Examples. The objects, features and advantages of the present invention will be readily understood through the following examples. The present invention is not limited to the embodiments described herein, but may be embodied in other forms. The embodiments described herein are provided to enable those skilled in the art to fully understand the spirit of the present invention. Therefore, the present invention should not be limited by the following examples.

In the present invention, a poly (sulfur-random-acrylate) (PS) nanofiber membrane (membrane mat) was designed to efficiently remove Hg ^{2 +} from contaminated water and the like. Different hydrophilic comonomers (e.g., methacrylic acid, 2-carboxyethylacrylic acid, glycidyl methacrylate and diallyl maleate) were used to alleviate the hydrophobicity of the sulfur.

In one embodiment of the present invention, a polysulfide (PS) using 2-carboxyethylacrylic acid as a comonomer is prepared in consideration of the fact that the boiling point is high and the carboxyl group can provide an additional crosslinking site for the bivalent ion. The prepared PS has a flow rheology and can be dissolved in a common solvent containing dimethylformamide (DMF). Polyacrylonitrile (PAN) was used as a polymer filter because it is relatively hydrophilic, chemically stable, and soluble in DMF and can be advantageous for producing homogeneous PS-PAN doping solution. The PS-PAN doping solution was prepared by electrospinning to produce PS-PAN nanofiber membrane (NM), which is favorable in morphological and mechanical properties, and is effective as a recyclable Hg ^{2 +} adsorbent for separation.

material

Sulfur (99.5 +%, being purified) were purchased from Acros Organics-(USA), 2- carboxyethyl acrylate (2-carboxyethyl acrylate, CEA) and polyacrylonitrile (polyacrylonitrile, PAN, average molecular weight = 150,000 g mol ^{- 1} ) was purchased from Sigma Aldrich (USA). Mercury chloride (HgCl ₂ , 99.5%), chromium chloride (CrCl ₂ , 99.9%), zinc chloride (ZnCl ₂ , 98+%), and Alfa a chloride of lead purchased from Aesar (USA) (lead chloride, PbCl 2, 99%), chloride, cadmium _{(cadmium chloride, CdCl 2,>} 99%), copper chloride purchased from Sigma Aldrich (USA) (copper chloride , CuCl 2 , ≫ = 99%) and nickel chloride hexahydrate (NiCl ₂ ) purchased from Fisher Chemicals (UK) 6H ₂ O,> 98%) were used to prepare simulated mercury ions and heavy metal solutions used in batch adsorption experiments. Heavy metal grade nitric acid (HNO ₃ , RHM 70%) purchased from Daejung Chemicals Co., Ltd. (South Korea), hydrochloric acid (HCl, RHM 35-37%) purchased from Samchun Pure Chemical Co. Ltd. Ethylenediaminetetraacetic acid (0.5M EDTA pH 8.0) purchased from Promega Corp. (USA) was used to evaluate the desorption of mercury ions loaded on PS-based nanofibers. All chemicals were used without further purification.

≪ Example: Preparation of nanofiber membrane for mercury adsorption >

Synthesis of polysulfides

Sulfur (2 g, 0.06 moles) was added to a 20 mL glass vial equipped with a magnetic stirrer and heated at 185 [deg.] C until sulfur had dissolved (~ 2 min). The amount of comonomer pre-heated to produce PS (polysulfide) with various molar ratios of S: comonomer was added via a syringe. When comonomer was added, after 25-30 minutes, two layers slowly homogenized by constant agitation (black solution formation) were observed. Thereafter, the heating was stopped and the product was cooled to form a viscous product, followed by vacuum drying at 70 DEG C for 24 hours.

Preparation of polysulfide nanofiber membrane (NM)

10 wt% of polyacrylonitrile (PAN) was dissolved in DMF (dimethylformamide) at 60 ° C to prepare a dope solution. In the dissolution process of the PAN (1 hour), PS (100, 150 and 200 wt% based on the weight of PAN) was added and further stirred for 3 hours. After mixing for 4 hours at 60 ° C, the PS-PAN dope solution was cooled at room temperature with constant stirring for 4 hours.

The dope solution was electrospun to an electrospinning machine (Model: ESP200D / ESP100D, NanoNC Co., Ltd., South Korea). 12 mL of the dope solution was transferred to a polypropylene syringe and injected via a needle having an internal diameter of 0.21 mm at a constant flow rate of 4 mL h ^-1 using a syringe pump (KD Scientific 750, South Korea) . A 22-25 kV DC power source was placed between the metal nozzle and a rotating stainless steel receiver wrapped with aluminum foil. The drum-rotatable collector was rotated at 500 rpm and spaced 120 mm from the needle. PS-PAN NM was vacuum dried at 30 ° C for 24 hours.

<Experimental Example>

Property Analysis

Fourier transform infrared (FTIR) spectra of PS samples were analyzed using a Cary 630 FTIR (Agilent Technologies, USA) spectrophotometer at room temperature using standard ATR methods. Elemental analysis was carried out using an Elementar Vario EL cube (Germany). Carbon, hydrogen, oxygen, nitrogen and sulfur (% CHONS) in PS were determined by combustible analysis using a thermal conductivity detector. A simultaneous DTA-TG instrument (DTG-60H, DTA-TG instrument, Shimadzu, Japan) was used to measure the thermal behavior of the PS sample. Samples between 20-25 mg were used for each experiment. The furnace was purged with nitrogen at a rate of 20 mL min ^-1 and heated from 30 ° C to 1000 ° C at a heating rate of 10 ° C min ^-1 . The rheologies of the PS samples were determined using a standard oscillatory temperature ramp method using an Ares G2 rheometer (USA). The sample was placed on a forced convection oven parallel plate (25 mm) and the sample was injected at a heating rate of 6.28 rad s ^-1 at a heating rate of 1 ° C min ^-1 from 35 ° C to 85 ° C, The storage (G ') and loss (G ") moduli of elasticity, viscosity and phase angle (δ) were determined. The morphology and surface characteristics of PS-PAN NM were measured by field emission scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDS, 50 mm ² X-max ^N , Horiba, Japan) Field Emission Scanning Electron Microscope, FE-SEM, SU-70 Jitachi, Japan). The mechanical properties of NM were evaluated by a pull-to-break test using a Universal Testing Machine (UTM LFPlus, Lloyd Instruments, Ametec Inc., UK) equipped with a 1 kN load cell. Cut samples (20 mm x 50 mm) preloaded by 0.02 kg-f were analyzed at a cross-head speed of 50 mm min ^-1 . The actual density (rho _T ) of the nanofibers produced was measured by a pycnometer method. Brunauer-Emmett-Teller (BET) surface area was performed using Belsorp-mini II (Mel Japan, Inc.). Nitrogen adsorption / desorption isotherms were determined in a relative pressure range ( pp _o ^-1 ) between 0.01 and 1.0. The pore size distribution of the nanofibers was measured using a capillary flow porometer (CFP-1200AE, Porous Materials, Inc., USA). The drying / wetting mode was carried out using a wetting agent, Galwick (surface tension: 15.9 dynes / cm).

Adsorption experiment

The effects of PS and PS-PAN on mercury separation were evaluated through equilibrium adsorption experiments. (25 mg), pure PAN nanofibers (25 mg) and different amounts of PS (sample mass: 100 wt% = 50 mg; 150 wt% = 41.67 mg; 200 wt% = 37.31 mg; The PS-PAN loaded with 25 mg poly (Sr-CEA) was washed with 0.5 M HCL and then rinsed thoroughly with DI water until pH = 7. The samples were vacuum dried at 50 ° C for 12 hours, then stored in a desiccator and weighed to determine the actual mass ( m ). The samples were immersed in 50 mL simulated Hg ^{2 +} solution and placed in a shaker incubator (160 rpm) at 30 ° C for 24 hours. Adsorption capacity ( q _e ) values were calculated according to the following equation:

(방정식 1)

(Equation 1)

Where C _o and C _e mean initial mercury concentration and equilibrium mercury concentration, respectively, and V means the volume of the solution.

Since it was confirmed in the preliminary experiment (FIG. 1) that PS-PAN NM had no affinity for Na ⁺ , 1 M NaOH was used to adjust the pH of the infusion solution in experiments confirming the effect of pH on mercury adsorption Respectively. To determine the adsorption isotherm and thermodynamic properties for mercury adsorption in PS-PAN NM, adsorption experiments were performed at different initial mercury concentrations (C _o = 100-800 mg L ^-1 ) at different temperatures (30-60 ° C) Respectively. The adsorption behavior was evaluated by measuring the lithium recovery ( q _t ) during the time of adsorption ( t ) change until equilibrium was reached (equation 2):

(방정식 2)

(Equation 2)

The affinity of PS-PAN NM to other heavy metals is determined by the simulated heavy metal solution (eg Cr ^{3 +} , Cu ^{2 +} , Zn ^{2 +} , etc.) based on the average acid-extractable concentration of heavy metals in agricultural soils Pb ^{2 +} , Ni ^{2 +} , Cd ^{2 +} and Hg ^{2 +} ). Cation concentration before and after adsorption equilibrium was analyzed by inductively coupled plasma mass spectrometry (ICP-MS Agilent series, USA).

Repeated adsorption / desorption experiments

Different acid solutions were used as stripping agents to elute the adsorbed mercury. Mercury-loaded PS-PAN NM was treated with 50 mL of 0.5 M HCL, 0.5 M HNO _3, or 0.5 M EDTA. The eluents were analyzed using ICP-MS (see section below) and the effect of eluents on desorbed mercury was compared. The most effective concentration of eluent was optimized to elute 100% of adsorbed mercury. The optimal concentration of the most effective eluent was then applied to an adsorption-desorption cycle repeat experiment to evaluate the reusability of PS-PAN NM. The regenerated nanofibers were washed with DI water until neutral pH was reached. The washed nanofibers were vacuum dried for 4 hours at 50 &lt; 0 &gt; C, weighed again and used for the next adsorption cycle.

Analysis method

An aqueous solution, such as the injection solution, the mercury-eluted solution and the acid solution for eluting mercury was collected and filtered through a 0.2 μm PVDF syringe filter. Prior to ICP-MS analysis, 5 mL sample portion to MARS-5 was a microwave oven (CEM, USA) pre-treatment _{(10 mL 60% HNO 3,} 0.2 mL 35% HCl and 5 mL DI water) in the acid. The treated sample was transferred to a 100 mL polypropylene volumetric flask by gravity, filtered and diluted with deionized (DI) water. Elemental analysis was performed using inductively coupled plasma mass spectrometry (ICP-MS Agilent 7500 series, USA). In order to avoid the memory effect of the mercury, Au ^{3 + -} the (5 mg L ¹⁾ was added to all samples and standards and cleaning solutions in the form of AuCl _3.

EXPERIMENTAL EXAMPLE 1 Analysis of Copolymerization Properties of Synthesized Polysulfide (PS)

One of the considerations in comonomer selection for the synthesis of PS by the reverse vulcanization reaction is the high boiling point which can inhibit volatilization of comonomers at higher temperatures than the bottom temperature of S ₈ ( T _f = 159 ° C) )to be. At this temperature, it is expected that the radicals will be formed through ROP (ring opening polymerization) and the radical will react with the vinyl group of the comonomer. Previously, 1,3-diisopropenylbenzene (DIB bp = 231 ° C), 1,3-diethynylbenzene (DEB bp = 189 ° C) and d-limonene (d-limonene (bp = 178 ° C)) was used. However, for application to mercury separation, the hydrophilicity of the final polysulfide must also be considered to reduce the hydrophobicity of the sulfur. This can promote the diffusion of mercury ions from the bulk feed solution to the adsorbent by maintaining good contact between the PS and the aqueous source (and consequently the adsorption of mercury ions on the polysulfide). In this experiment, a copolymerization test with a sulfur element (S ₈ ) was conducted by directly adding methacrylic acid, 2-carboxyethyl acrylic acid, diallyl maleate and glycidyl methacrylic acid at 180 ° C. Table 1 shows the structure of each comonomer reacting with S ₈ and the optical image of the final product.

The hydrophilic comonomer (sulfur: comonomer (mol) = 1: 1) reacting with the sulfur element (S ₈ ) Comonomer rescue The reaction product of sulfur and comonomer Methacrylic acid

2-carboxyethylacrylic acid

Diallyl maleate

Glycidyl methacrylic acid

Carboxylated monomers such as methacrylic acid and 2-carboxyethyl acrylic acid have been tested for the first time since the carboxyl groups of the monomers may provide cross-linking sites for divalent ions. When the comonomer was added to the molten sulfur, two liquid phase layers could be observed (Figure 2a). The molten sulfur is not usually mixed with the organic reagent, resulting in a mixture having two phases. However, by stirring the mixture in the S ₈ T _f or more and the heating temperature may facilitate the mixing of the S _8. The mixing facilitated the reaction between S ₈ and the comonomer to form a single-phase, black, viscous solution (Figure 2a). It was observed that when the methacrylic acid was added to the molten S ₈ , the liquid mixture boiled. This was due to the evaporation of methacrylic acid at the reaction temperature (180 ° C) because the boiling point (161 ° C) of methacrylic acid was almost similar to the T _f of S ₈ . The optical image of the reaction product shows an uneven color distribution because the reaction is incomplete due to evaporated methacrylic acid. It was therefore determined that 2-carboxyethylacrylic acid ( T _b = 271 ° C) was a good comonomer candidate. As a result of reacting 2-carboxyethyl acrylic acid with S ₈ , a black viscous product was formed. Dialyl malate ( T _b = 264 ° C) containing three vinyl groups in the potential cross-linking sites was also tested. Reaction of diallyl maleate with S ₈ resulted in the formation of a solid inviscid product. However, at 180 ° C, the product remained a solid, meaning that there was a very high degree of cross-linking between the sulfur chain and the diallyl maleate. Finally, the glycidyl monomer is used as the epoxy resin dill methacrylic acid (T _b = 189 &lt; 0 &gt; C). As a result of the experiment, a product similar to that in the experiment with diallyl maleate was obtained. The resulting product was also solid at 100 占 폚. On the basis of these experimental results, further experiments were carried out on the polysulfides having consistent properties produced by the reaction of S ₈ with 2-carboxyethylacrylic acid.

Figure 3 shows the FTIR spectra of 2-carboxyethylacrylic acid (CEA) and PS with different molar ratios of S: CEA. A broad peak of 2500-3400 cm ^-1 corresponding to the OH of the carboxy group was observed in all samples. The characteristic peaks appearing in all samples were a strong peak of 1640-1810 cm ^-1 indicating sp ² C = 0 and a peak of 1050-1150 cm ^-1 indicating alkoxy CO bonding. A notable spectrum is the sp ² C = C bond between 1620-1680 cm ^-1 observed in CEA, which is not present in the spectrum of the polysulfide product. This means that the consumption by the radical attack of free radicals produced by the vinyl group of the CEA ROP of S _8. In addition, in the polysulfide product, a peak of 550-700 cm ^-1 corresponding to SS stretching, a peak of 570-710 cm ^-1 corresponding to CS stretching, and a very weak 2640-2650 cm ^-1 peak corresponding to the SH bond were observed. However, CEA Not observed. This means that successful free radical polymerization between sulfur and CEA was achieved as shown in the elemental analysis, producing sulfur rich (42%) PS (FIG. 4).

Experimental Example  2: Of polysulfide (PS) Rheology  Characteristic and thermal characterization

The oscillatory rheology combined with simultaneous thermal analysis (STA) was performed to confirm the effect of sulfur: comonomer mole ratio on the thermodynamic properties of PS, and the results are shown in FIG. All samples were confirmed to be temperature dependent and exhibited a viscous state (Figure 6). The viscosity range (ie, viscosity) increased with increasing molar amount of CEA. PS at S: CEA = 2: 1 exhibited the smallest viscosity (2,864 Pa-s) at an initial temperature of 35 ° C, followed by PS with S: CEA = 1: 1 (10,004 Pa-s) , And the PS with S: CEA = 1: 2 (36,670 Pa-s) was the most viscous.

Through STA, PS was decomposed between 220-290 ° C, and a significant amount of PS was decomposed up to 250 ° C (FIG. 7). This decomposition is an endothermic reaction due to the depolymerization process (SS bond cleavage). In addition, the decomposition temperature profile as well as the glass transition temperature ( T _g ) decreased with increasing sulfur content (eg S: CEA molar ratio increase). As the amount of sulfur in the copolymer increased, the viscosity, remaining% weight and T _g tended to decrease. This tendency is consistent with the hypothesis that the higher the amount of sulfur, the longer the sulfur rank in the PS. Such as ^{- (1 799 kJ mol) SS} (226 kJ mol -1) the binding energy the ^{CS (272 kJ mol -1),} CC (346 kJ mol -1), CO (358 kJ mol -1) and C = O Considering that it is weaker than an intermolecular bond, PS with a large amount of sulfur (eg S: CEA = 2: 1) decomposes at a relatively lower temperature than PS with a low amount of sulfur and has a low T _g &Lt; / RTI &gt; Thus, the thermodynamic properties of PS can be controlled by varying the ratio of sulfur to CEA.

Experimental Example 3: Characterization of PS-PAN nanofiber membrane (NM)

The samples were processed by melt electrospinning considering the temperature dependence and the flowing viscosity of the poly (S-r-CEA) sample at elevated temperature. During electrospinning (FIG. 8A), the polysulfide was heated in a polypropylene syringe using a syringe heater (Heater Kit 5SP, New Era Pump Systems, Inc., USA). The syringe heater was set at 60 캜. At this temperature, it was confirmed that PS of S: CEA = 2: 1, 1: 1 and 1: 2 had viscosities of 3.26 Pa-s, 25.14 Pa-s and 101.6 Pa-s, respectively. Although the viscosity (viscosity) of the PS exceeds the viscosity (<5 Pa-s) of the polymer dope solution generally prepared in solution electrospinning, the general molten polymer (40-200 Pa-s) Lt; / RTI &gt;

The process parameters such as flow rate, voltage, collection distance and spinneret diameter were adjusted to extract the fibers from the PS, but they were difficult to fabricate with fibers. Similar results were obtained when PS was processed through solution electrospinning.

The poly (S-r-CEA) dope solution (Fig. 8b) was then prepared by dissolving poly (S-r-CEA) in DMF. PS was loaded in DMF in different amounts to control the viscosity of the dope solution. However, similar stains were observed between the PSs produced. This is because the evaporation of the solvent in cooling or solution electrospinning in molten electrospinning causes staining due to the viscosity of the temperature sensitive PS while the temperature is slightly increased while the PS is curing in the receiver.

To overcome this, PAN was added as a polymer filler. PAN was selected considering hydrophilicity and solubility in DMF. The fibers were successfully extracted and a stable film was formed. Different amounts of PS (e.g. 100 wt%, 150 wt% and 200 wt% added to PAN) were prepared (Fig. 11). Up to 200 wt% PS (S: CEA = 2: 1) may be added to a 10 wt% PAN solution. 250 wt% of PS was observed in an undissolved state.

The morphology of PS-PAN NM loaded with varying amounts of PS (FIG. 12) appeared in well-formed fiber forms (e.g., 100 wt% and 150 wt%) without bead formation. This means that the dope solution and the electrospinning conditions used during the preparation of PS-PAN NM were suitable. However, when the PS concentration was increased to 200 wt%, it was observed that PS fragments were produced. This is because the flow of the dope solution is limited as defects (or bead generation) occur in the nanofibers as the concentration of the dope solution increases beyond a threshold value (for example, a concentration at which homogeneous nanofibers are formed without beads).

The average fiber diameter of the fibers loaded with 100 wt% of PS was 1055 nm (Fig. 12). This is almost twice the diameter of pure PAN nanofiber (about 500 nm in diameter) at the same concentration (ie 10 wt% wrt pure dope solution) because of the high polymer concentration by the addition of PS, The average fiber diameter decreased as the PS loading increased, and the average fiber diameter decreased as the PS loading increased. beaded fiber, this may be because the highly concentrated polymer solution on the needles is physically disturbed and the fibers are split into smaller fibers, which can be seen from the uneven distribution of fiber diameters with more PS loading. PS-PAN NM in wt% loaded fibers was found to have a bimodal distribution with average diameters of 627 nm and 1032 nm PS There was a change in the surface area and mechanical properties of the fibers depending on the shape of the PS-PAN nanofibers, which vary depending on the loading (Figure 13). The average size of the fibers decreases with increasing polysulfide content, The SEM image of a 200 wt% fiber, which tends to aggregate due to the texture of the texture, can also be seen, which can reduce the void space between fibers and affect the porosity of the nanofiber. All of the samples showed an isotherm of type II as shown in the nitrogen adsorption-desorption branches of the PS-PAN nanofibers (Figure 13a) according to Figure 1. 100 wt% of the fibers had a hysteresis loop indicating the porosity, While the fibers of 200 wt% showed a similar shape to the non-porous pure type II isotherms. In fact, the porosity (P) calculated from the apparent density (r _B ) and the true density (r _T ) , The interplanar diameter and BET surface area calculated from the CFP analysis decreased with increasing amounts of polysulfides, even though the mean diameter size of the fibers decreased (Table 2).

Structural characteristics of PS-PAN NM PS loading amount
(weight%) ρ _T (g cm ^-3 ) ρ _B (g cm ^-3 ) P (%) Pore diameter
(탆) BET SA
m ² g ^-1 100 1.15 ± 0.06 0.29 + 0.03 74.46 1.64 + 0.02 5.65 150 1.19 ± 0.01 0.38 ± 0.01 67.96 1.12 + 0.06 2.35 200 1.28 + 0.04 0.65 ± 0.01 49.30 0.55 + - 0.01 1.81

When increasing PS loading, the mechanical properties of PS-PAN NM including maximum load, strength and Young's modulus were improved (FIG. 13B). As the PS loading increases, the average fiber diameter decreases, which can result in an increase in the number of fiber-to-fiber contacts, which can improve the mechanical properties. In addition, the adhesion properties of PS can complement the improvement of the mechanical properties of PS-PAN NM with high PS loading.

This is one of the advantages of PS-PAN NM compared to composite nanofibers in which the inorganic adsorbent is immobilized on the electrospinning polymer matrix. In the case of such composite nanofibers, aggregate protrusions can cause microfine defects in the nanofiber structure, which can mechanically weaken the nanofiber composite, which conflicts with the loading of the adsorbent. However, in PS-PAN NM, increasing the PS loading not only optimizes for mercury ion recovery, but also improves the mechanical properties of nanofibers.

Experimental Example 4: Confirmation of mercury adsorption performance of PS-PAN NM

After producing PS-PAN NM, mercury separation was evaluated through batch adsorption experiments. First, the effect of S: CEA mole ratio on mercury adsorption of PS and PS-PAN NM was evaluated. PAN nanofibers adsorb Hg ^{2 +} a minimal ^were (6.9 mg ¹ g) (Fig. 14). Therefore, the separation of Hg ^{2 +} by PS-PAN nanofibers can be mainly due to PS. In addition, all PS adsorbed more mercury than each PS-PAN NM. In the process of removing heavy metals with PAN, the nitrile group is transformed into amidoxime through the reaction in methanolic hydroxylamine. Otherwise, when the PAN is used as a lithium recovery support, it will show only minimal affinity for certain cations. In addition, the PAN-modified resin also showed low affinity for mercury.

Considering the inactive PAN moiety, the amount of mercury adsorption per unit of the total material is expected to be considerably reduced. In the case of S: CEA = 2: 1, the nanofibers (96 mg g ^{- 1} ) retained 47% of the adsorption capacity of pure PS (206 mg g ^{- 1} )

Experimental Example 5: Hg ²⁺ Identification of initial pH effect on adsorption

Since the initial pH of the solution had various effects on the environment of the adsorption system, the effect of initial pH on adsorption of Hg ^{2 +} using PS-PAN NM was investigated (FIG. 15).

As a result, the mercury adsorption uptake increased from pH = 2, and the Hg ^{2 +} adsorption rate (101 mg g ^-1 ) reached 98% at pH = 6. However, at higher pH (> 6), Hg ^{2 +} adsorption began to decrease. In certain acidic water systems (eg pH <2.0), Hg ^{2 +} is mostly present in hydrated Hg ^{2 +} (hydrated Hg ^{2 +} (aq)). These Hg ^{2 +} (aq) is hydrolyzed with increasing pH (2.0 to 5.0), a positive charge _{^{(HgOH +, pK OH, 1}} = 3.87) and a neutral metal-hydroxide species _{(Hg (OH) 2, pK} OH, ₂ = 2.77).

These mercury-hydroxyl species have a high affinity for binding sites because of their softer properties as Lewis acid or hydrated Hg ^{2 +} aq)), which is relatively small in hydrated size. In this experiment, the reduction of mercury adsorption in the range of pH 4.0 to 2.0 is considered to be due to the decrease of HgOH ⁺ and Hg (OH) ₂ concentrations at low pH and the competitive binding of proton to the adsorbent sites. The reason for the decrease in the mercury adsorption capacity at high pH may be that PS is dissolved in the basic solution as observed in the affinity test of PS-PAN NM for Na ⁺ (FIG. 1).

Experimental Example 6: Hg ²⁺  Analysis of the effect of PS loading on adsorption

When PS loading increases from PS-PAN NM been shown to be the Hg ^{+ 2} adsorption increases. This fact was confirmed when the loading was increased from 100 wt% (99.31 mg g ^-1 ) to 150 wt% (124.86 mg g ^-1 ) (Fig. 16). After the 150% by weight of PS was treated with PS-loaded PAN NM Hg ^{2 +} concentration is 0.04 mg L from 100.6 mg L ^{-1 -} The 99.96% was removed to ^one. However, when the loading was increased from 150 wt% to 200 wt%, the adsorption capacity decreased (92.28 mg g ^{- 1} ). At 200 wt%, agglomeration began to be formed, and the distribution of polysulfide was found to be non-uniform during electrospinning. This heterogeneity distribution was more evident when loading 250 wt%, and the undissolved PS was carried in the dope solution and was not used in subsequent experiments. The evaluation of adsorption characteristics of PS-PAN NM was confirmed by applying nanofibers loaded with 150 wt% of PS with S: CEA = 2: 1.

Experimental Example 7: Determination of adsorption isotherm and thermodynamic characteristics of PS-PAN NM

Simultaneous adsorption isotherm and thermodynamic experiments confirmed adsorption mechanisms and intrinsic energy changes associated with Hg ²⁺ adsorption of PS-PAN NM. Batch adsorption experiments were performed using different initial mercury concentrations ( C _o = 100-800 mg L ^-1 ) at different temperatures (30-60 ° C). The adsorption capacity was fitted to the Langmuir model (Equation 3) and the Freundlich model (Equation 4).

(방정식 3)

(Equation 3)

(방정식 4)

(Equation 4)

Wherein q _m And K _L mean the maximum adsorption capacity and the Langmuir constant, respectively. K _F is the prodrug constant for the adsorption capacity and n is the adsorption intensity.

Represent the q _e (q _e with C _o) increased (Fig. 17a, 18a) is higher Hg ^{2 +} availability (availability) of according to C _o at all temperatures, which as a result Hg in the active site of PS and PS-PAN NM ^{2 +} can be increased.

Taking into account the calculated adsorption isotherm coefficients (Table 3, Table 4), the adsorption of Hg ^{2 +} on PS and PS-PAN nanofibers was more pronounced than on Freundlich (Figures 17c and 18c) by the single layer Langmuir type (Figures 17b and 18b) Can be better characterized.

S: Adsorption isotherm constant of PSA with different molar ratio of CEA S: CEA molar ratio Proindrih Langmuir n K _f
(mg g ^-1 ) r ² K _L
(L mg ^-1 ) q _m
(mg g ^-1 ) r ² 1: 2 1.75 13.24 0.98 0.0014 588.24 > 0.99 1: 1 2.16 40.01 0.96 0.0015 666.67 > 0.99 2: 1 2.73 123.73 0.95 0.0011 909.09 > 0.99

[ C _o = 100-1000 mg Hg ^{2 +} L ^-1 ; pH = 6]

Adsorption isotherm constants of PS-PAN NM (S: CEA = 2: 1 loading of PS 150 wt%) by temperature Temperature Proindrih Langmuir n K _f
(mg g ^-1 ) r ² K _L
(L mg ^-1 ) q _m
(mg g ^-1 ) r ² 30 ℃ 5.05 136.5 0.94 0.03 473.0 > 0.99 40 ℃ 4.98 157.5 0.89 0.05 525.7 > 0.99 50 ℃ 5.22 206.9 0.83 0.13 591.4 > 0.99 60 ° C 6.41 270.2 0.74 0.45 611.6 > 0.99

[ C _o = 100-800 mg Hg ²⁺ L ^-1 ; pH = 6]

These results thiol functionalized and zinc using the doped biological magnetite particles (thiol-functionalized Zn-doped biomagnetite particles) with a thiol functionalized porous aromatic skeleton (thiol-functionalized porous aromatic framework, PAF-SH) Hg 2 + Which is similar to the case of separation. The Langmuir adsorption model is consistent with the above data because the mercury adsorption is dependent on the specific binding sites (reduced organic groups (like thiols), carbonyl-O, and carboxyl-O present in PS and PS- Seat) function. The maximum Hg ^{2 +} adsorption capacities (q _m ) in PS samples with S: CEA molar ratios of 1: 2, 1: 1 and 2: 1 in Table 3 were 588.24, 666.67 and 909.09 mg g ^-1 , respectively. These values were determined for sulfur-functionalized porous carbon (518 mg g ^-1 ), porous silica (298 mg g ^-1 ), chalcogen-1 (645 mg g ^-1 ) SH (1014 mg g &lt; ^-1 &gt;). This excellent mercury adsorption capacity may be due to the abundance of the bonding sites of Hg ^{2 +} present in the PS especially in the PS with S: CEA molar ratio of 2: 1.

In Table 4, the maximum Hg ^{2 +} adsorption capacity (q _m ) of PS-PAN NM (S: CEA = 2: 1 loading of PS 150 wt%) is determined by adsorption at 30 ° C, 40 ° C, 50 ° C and 60 ° C , Respectively, and 473.0, 525.7, 591.4 and 611.6 mg g ^{- 1} , respectively. This value is lower than the pure PS, which may be due to a PAN fraction with minimal affinity for Hg ^{2 +} .

Binding interactions between Hg ^{2 +} and thiol and sulfide groups as described above can be observed from FTIR before and after PS-PAN NM adsorption (Fig. 19A). IR spectra showed SH peak shifts from 2652 cm ^-1 to 2382 cm ^-1 and SS or CS peak shifts from 709 cm ^-1 to 628 cm ^-1 in mercury-loaded PS-PAN NM. This suggests strong binding interactions between mercury and thiol and sulfide groups. Effective adsorption of Hg ^{2 +} was confirmed by EDS mapping of nanofibers before (FIG. 19B) and after (FIG. 19C) adsorption experiments. Hg ^{2 +} was not detected before the adsorption experiment, while uniformly distributed Hg ^{2 +} was detected after adsorption (FIG. 20). This may be due to the uniform distribution of sulfur, which is a major factor promoting Hg ^{2 +} adsorption, on nanofibers.

In order to confirm the intrinsic energy change for mercury adsorption in PS-PAN NM, the change of Gibbs energy ( ΔG ^θ ), enthalpy ( ΔH ^θ ) and entropy ( ΔS ^θ ) were observed while changing the adsorption temperature. ΔG ^θ is a dimensionless standard equilibrium constant ( K ⁰ ) and PS-PAN nanofibers (ρ _NF ) determined by the partition coefficient K _d ( K _d = q _e / C _e ) = 1192.5 ± 0.01 kg m ^-3 ) (Equation 5). The Van't Hoff equation (Equation 6) is used to determine ΔH ^θ and ΔS ^θ , where R is the ideal gas constant (8.314 JK ^{- 1} mol ^{- 1} ) and T is the absolute temperature (K) :

(방정식 5)

(Equation 5)

(방정식 6)

(Equation 6)

(방정식 7)

(Equation 7)

As the temperature increased from 30 ° C to 60 ° C, the mercury q _e value at PS-PAN NM increased (Fig. 18a). During the increase of q _e , the required ΔG ^θ value for each mercury initial concentration became more negative, which means that the adsorption driving force increased with temperature (Table 5). In addition, the absolute value of ΔG ^θ increased at each initial concentration because the higher the temperature, the more spontaneous and thermodynamically stable mercury adsorption increases the q _e value.

Thermodynamic parameters of mercury adsorption in PS-PAN NM C _o = 100 mg L ^-1 T (占 폚) ΔH ^θ
(kJ mol ^-1 ) ΔS ^θ
(J mol ^-1 K ^-1 ) ΔG ^θ
(kJ mol ^-1 ) 30 68.92 348.60 -34.83 40 -42.92 50 -44.27 60 -45.72 C _o = 200 mg L ^-1 T (占 폚) ΔH ^θ
(kJ mol ^-1 ) ΔS ^θ
(J mol ^-1 K ^-1 ) ΔG ^θ
(kJ mol ^-1 ) 30 43.66 227.14 -25.32 40 -27.23 50 -29.64 60 -32.11 C _o = 300 mg L ^-1 T (占 폚) ΔH ^θ
(kJ mol ^-1 ) ΔS ^θ
(J mol ^-1 K ^-1 ) ΔG ^θ
(kJ mol ^-1 ) 30 62.74 276.92 -21.64 40 -23.17 50 -26.72 60 -29.75 C _o = 400 mg L ^-1 T (占 폚) ΔH ^θ
(kJ mol ^-1 ) ΔS ^θ
(J mol ^-1 K ^-1 ) ΔG ^θ
(kJ mol ^-1 ) 30 65.50 282.83 -20.54 40 -22.55 50 -25.72 60 -28.96 C _o = 500 mg L ^-1 T (占 폚) ΔH ^θ
(kJ mol ^-1 ) ΔS ^θ
(J mol ^-1 K ^-1 ) ΔG ^θ
(kJ mol ^-1 ) 30 63.26 274.30 -20.18 40 -22.25 50 -24.99 60 -28.46 C _o = 600 mg L ^-1 T (占 폚) ΔH ^θ
(kJ mol ^-1 ) ΔS ^θ
(J mol ^-1 K ^-1 ) ΔG ^θ
(kJ mol ^-1 ) 30 39.21 192.62 -19.29 40 -20.75 50 -23.29 60 -24.87 C _o = 700 mg L ^-1 T (占 폚) ΔH ^θ
(kJ mol ^-1 ) ΔS ^θ
(J mol ^-1 K ^-1 ) ΔG ^θ
(kJ mol ^-1 ) 30 24.97 143.26 -18.46 40 -19.72 50 -21.55 60 -22.62 C _o = 800 mg L ^-1 T (占 폚) ΔH ^θ
(kJ mol ^-1 ) ΔS ^θ
(J mol ^-1 K ^-1 ) ΔG ^θ
(kJ mol ^-1 ) 30 20.21 125.38 -17.80 40 -18.91 50 -20.48 60 -21.45

In all initial Hg ^{2 +} concentration van't Hoff equation (21) is a good linearity (r ^2> 0.95) if the indicated eoteuna ^{_{C o = 100 mg L -1 (}} r 2 = 0.53) did not have, which is optimized conditions (Eg, 100% Hg ^{2 +} removal) because mercury has been completely adsorbed (eg, in 100% Hg ^{2 +} removal). Subsequent experiments were therefore carried out using PS-PAN NM (S: CEA = 2: 1) loaded with 150 wt.% PS at C _o = 200 mg L ^-1 . On the other hand, the reciprocal of temperature and ln The linear negative correlation between K ^o suggests that mercury adsorption is an endothermic process in PS-PAN NM, which can be confirmed by the positive ΔH ^θ value at the initial concentration of mercury. The endothermic process may be due to the energy required to diffuse Hg ^{2 +} in the active site of PS-PAN NM. Spontaneity of this endothermic Hg ^{2 +} absorption can be verified more clearly by the amount of ΔS ^θ value, which may be due to increased and becomes higher random Fig dynamic movement (kinetic mobility) of the solution at the interface between the adsorbent.

Experimental Example 8: Determination of adsorption kinetics of PS-PAN NM

In order to confirm the adsorption behavior of Hg ^{2 +} in PS-PAN NM, the Hg ²⁺ adsorption rate, which determines the residence time required to complete the process, was investigated. As a result of the recovery experiment (FIG. 22), the amount of Hg ^{2 +} adsorbed at initial concentrations of 800 and 200 mg L ^-1 was increased, and adsorption reached equilibrium after 100 minutes and 150 minutes, respectively.

Kinetic models of the Lagergren pseudo-linear equation (equation 8) and a similar quadratic velocity equation (equation 9) were used to determine the overall rate of adsorption:

(방정식 8)

(Equation 8)

(방정식 9)

(Equation 9)

In the above equation, k ₁ and k ₂ are rate constants corresponding to the respective equations. The correlation (r ² value) value suggests that the similar quadratic model shows better results than the Lagrangian-like primary rate model of the two models (Table 6).

Kinetic constants of PS-PAN NM for mercury separation C _o
(mg L ^-1 ) Pseudo-first order Pseudo-second order q _e
(mg g ^-1 ) k ₁ x 10 ^-2
(min ^-1 ) r ² q _e
(mg g ^-1 ) k ₂ x 10 ^-4
(g mg ^{- 1} min ^-1) r ² 200 96.69 1.57 0.95 222.22 2.18 0.99 800 64.71 1.45 0.60 454.55 2.20 0.99

pH = 6 ± 0.1; m40 mg; T = 30 ° C

In Table 6, when the initial concentration of 200 and 800 mg L ^-1 k ₂ are respectively 2.18 × 10 ^-4 and 2.20 × 10 ^-4 g mg ^- was found to be ¹ min ^-1. Initial Hg ^{2 +} k ₂ is relatively high at high levels, it may indicate that the mercury is rich in the due to a large amount of the impregnation solution to the active site of PS-PAN NM Hg ^{+ 2} diffuses faster. The pseudo-second-order behavior model involves three successive stages in which the adsorbent (metal ion) adsorbs as a porous adsorbent: (1) migration of metal ions from solution to adsorbent surface; (2) migration of metal ions into adsorbent pores; And (3) adsorption of metal ions on the inner surface of the adsorbent.

Experimental Example 9: Determination of ion selectivity of nanofiber

To verify the ion selectivity of poly (S-r-CEA) nanofibers, simulations were conducted with heavy metal solutions based on average acid extractable concentrations of heavy metals in agricultural soils.

Determination of ion selectivity of PS-PAN NM (S: CEA = 2: 1, PS 150% by weight) Cation C _o (mg / L) C _o ( mmol / L) C _e ( mmol / L) Q _e ( mmol / g) K _d (mL / g) alpha (Hg / Me) CF
(L / g) Hg ^{2 +} 1.09 0.01 4.99 x 10 ^-6 0.01 1945341 1.00 1.79 Cr ^{2 +} 40.46 0.78 0.40 0.68 1729.45 1124.83 0.88 Cu ^{2 +} 45.01 0.71 0.59 0.21 348.06 5589.14 0.29 Zn ^{2 +} 120.70 1.85 1.49 0.63 425.64 4570.44 0.34 Pb ^{2 +} 49.01 0.24 0.13 0.18 1357.91 1432.60 0.77 Ni ^{2 +} 26.84 0.46 0.41 0.08 186.51 9.27 0.17 Cd ^{2 +} 1.81 0.02 0.02 0.00 26.07 13.35 0.03

In Table 7, mercury was not detected after PS-PAN NM treatment when the initial concentration was 1.1 mg L ^-1 . In contrast, the concentration of Cd ^{2 +} , which is similar to the initial concentration of mercury, did not decrease. The concentration of Ni ^{2 +} was not significantly decreased. PS-PAN NM were found to have affinity to Cr ^{3 +,} Zn ^{2 +} and Pb ^{+ 2} having some affinity for Cu ^{+ 2.} From this data it can be seen that PS-PAN NM is effective at separating other heavy metals at low concentrations.

Experimental Example 10: Confirmation of reusability of PS-PAN NM

HNO ₃ , HCl and EDTA were used as eluents to confirm the reusability of PS-PAN NM (FIG. 23A). As a result of the reusability test at the same concentration (0.5 mol L ^{- 1} ), not all eluents were able to elute the adsorbed Hg ^{2 +} . HCl showed the highest desorption rate (49.8%), followed by EDTA (45.9%) and HNO ₃ (42.6%). Through this, it was confirmed that HCl is an eluent that is optimal for the purpose of eluting 100% of mercury (FIG. 23B).

Desorption (stripping) efficiency increased with increasing HCl molarity, while ~ 100% desorption was achieved at 5 and 6 M HCl. This is a less concentrated than the 12 M HCl is used to remove the Hg ^{2 +} in a thiol functionalized porous aromatic skeleton (thiol-functionalized porous aromatic framework) and alkyl thiol TMMPS functionalized porous silica (alkythiols TMMPS-functionalized mesorporous silica) Value. The regenerated PS-PAN nanofibers were reused to separate Hg ²⁺ . As a result, the PS-PAN NM maintained> 97% of the original loading capacity during the 5 regeneration and reuse cycles (FIG. 23C).

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereto will be. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (18)

A method for preparing a nanofiber membrane for mercury-adsorbing adsorption comprising the step of adding a polysulfide prepared by inversely vulcanizing a hydrophilic comonomer having sulfur and an acrylate group to a dope solution in which a polymer material is mixed with a solvent, followed by electrospinning.
The method according to claim 1,
Wherein the comonomer is selected from the group consisting of methacrylic acid, 2-carboxyethyl acrylic acid, diallyl maleate, and glycidyl methacrylic acid.
The method according to claim 1,
Wherein the comonomer is 2-carboxyethyl acrylic acid.
The method according to claim 1,
Wherein the inverse vulcanization reaction is performed at 50 to 80 ° C for 3 to 5 hours and then at room temperature for 3 to 5 hours to cool the nanofiber membrane for mercury adsorption.
The method according to claim 1,
Wherein the sulfur and the hydrophilic comonomer are reacted at a molar ratio of 1: 0.5 to 2. The method for producing a nanofiber membrane for mercury adsorption according to claim 1,
The method according to claim 1,
Wherein the polymer material comprises at least one selected from polyacrylonitrile, polysulfone, polyethersulfone, polyvinylidene fluoride, cellulose acetate, and polyvinyl chloride.
The method according to claim 1,
Wherein the solvent comprises at least one selected from the group consisting of dimethylformamide, dimethylformaldehyde, tetrahydrofuran, dimethylacetamide and methylpyrrolidone.
The method according to claim 1,
Wherein the polysulfide is added in an amount of 100 to 200 parts by weight based on 100 parts by weight of the polymer material.
A nanofiber membrane prepared by adding a polysulfide (PS) prepared by inverse vulcanization reaction of a hydrophilic comonomer having sulfur and an acrylate group to a dope solution in which a polymer substance is mixed with a solvent and electrospinning.
Comprising a polysulfide and a polymer material,
Wherein the polysulfide is prepared by an inverse vulcanization reaction of a hydrophilic comonomer having sulfur and an acrylate group.
The method according to claim 9 or 10,
Wherein the polymer material is polyacrylonitrile. &Lt; RTI ID = 0.0 &gt; 21. &lt; / RTI &gt;
And a step of subjecting the hydrophilic comonomer having an acrylate group and sulfur to an inverse vulcanization reaction to produce a polysulfide for mercury adsorption.
A polysulfide for mercury adsorption formed by an inverse vulcanization reaction of a hydrophilic comonomer having sulfur and an acrylate group.
14. The method of claim 13,
Wherein the hydrophilic comonomer is 2-carboxyethyl acrylic acid.
A mercury sorbent prepared by adding a polysulfide prepared by an inverse vulcanization reaction of a hydrophilic comonomer having sulfur and an acrylate group to a dope solution mixed with a polymer material and then electrospinning.
A nanofiber mercury sorbent comprising a polysulfide and a polymeric material,
Wherein the polysulfide is prepared by an inverse vulcanization reaction of a hydrophilic comonomer having sulfur and an acrylate group.
The method according to claim 15 or 16,
Wherein the polymer material is polyacrylonitrile.
Preparing a nanofiber membrane for mercury adsorption by adding a polysulfide (PS) prepared by inversely vulcanizing a hydrophilic comonomer having sulfur and an acrylate group to a dope solution in which a polymer material is mixed with a solvent, and electrospinning the solution; And
And adsorbing mercury from a solution containing mercury using the membrane.

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