KR102205242B1 - Composite for removing cesium and cation and method for preparing the same - Google Patents

Abstract

The present invention relates to a complex for removing cesium and cations and a method for preparing the same, and more particularly, to a metal-amino clay (M-AC), carboxymethylcellulose (CMC), and polyhedral oligomeric silsesquioxane, It relates to a complex for removing cesium and cations and a method for preparing the same, including POSS) or a derivative thereof.

Description

Complex for removing cesium and cations, and manufacturing method thereof {COMPOSITE FOR REMOVING CESIUM AND CATION AND METHOD FOR PREPARING THE SAME}

The present invention relates to a complex for removing cesium and cations and a method for preparing the same, and more particularly, to a metal-amino clay, carboxymethylcellulose (CMC) and polyhedral oligomeric silsesquioxane (POSS) or derivatives thereof Including, it relates to a complex that has selectivity to cesium and capable of effectively removing cation and a method for producing the same.

Environmental pollution is one of the biggest problems causing irreparable damage to the earth, and water pollution caused by heavy metal ions, organic dyes, and radionuclides has recently been pointed out as a serious cause of environmental pollution. In particular, nuclear power, which is regarded as a major power source to solve the global warming problem and meet the increasing energy demand, has a difficult problem in controlling radionuclides emitted from nuclear power plants. For example, cesium (137Cs) among radionuclides poses a threat to humans and ecosystems due to its long half-life (30.2 years) and high water solubility. In addition, aromatic dye molecules having a non-degradable structure such as methylene blue (MB) and chrysoidine G (CG) are known as mutagenic substances, carcinogenic substances and toxic substances.

Technologies such as oxidation, electrochemical processes, biodegradation and membrane separation have been applied to remove such harmful inorganic (heavy metals) and organic (dye) and radionuclides. Adsorption is currently evaluated as the most effective technology. Oxide, activated carbon, zeolite, natural clay minerals, zeolites, and the like have been studied to remove dyes and radionuclides from wastewater, but there is a problem in that the adsorption and adsorption capacity of various pollutants is limited.

On the other hand, metal-amino clay, such as iron-amino clay (FeAC), has a specific layered structure, is less toxic, has high chelating performance with metal, and has high cation exchange capacity and excellent expansion ability. However, some modification of the clay material is essential to improve the adsorption capacity and affinity for specific adsorbents.

In addition, carboxymethylcellulose (CMC) is a biodegradable polymer derived from cellulose and has excellent biocompatibility. For example, JP2015-199057A discloses a dispersion-type polymer flocculant for aqueous solutions containing cationic and anionic polymers as a dispersive polymer flocculant that can be applied to water purification, and carboxymethylcellulose can be used as anionic polymer. It is starting. However, in the case of such a dispersion type coagulant, there is a problem that the post-treatment process after coagulation is not easy.

Accordingly, it is possible to remove not only radionuclides but also harmful cations, and when a complex with improved adsorption removal efficiency and easy recovery is provided by establishing a specific structure, it is expected to be widely applied in related fields.

One aspect of the present invention is to provide a complex for removing cesium and cations having significantly improved adsorption capacity due to structural properties as well as chemical interactions.

Another aspect of the present invention is to provide a method of preparing the complex for removing cesium and cation of the present invention.

According to one aspect of the present invention, cesium and cation removal including metal-amino clay (M-AC), carboxymethylcellulose (CMC) and polyhedral oligomeric silsesquioxane (POSS) or derivatives thereof A dragon complex is provided.

According to another aspect of the present invention, preparing a first mixture in which a metal-amino clay (M-AC) and carboxymethylcellulose (CMC) are mixed in a solvent; Preparing a second mixture by adding polyhedral oligomeric silsesquioxane to the first mixture; Heating the second mixture to obtain a solid; And there is provided a method for producing a composite for removing cesium and cations, including the step of firing the solid.

According to the present invention, a composite having excellent radionuclide and cation adsorption capacity is provided by electrostatic attraction, ion exchange, and surface complexation. In particular, the complex of the present invention has significantly improved radionuclide and cation adsorption capacity based on the structural characteristics in which polyhedral oligomeric silsesquioxane is disposed between the layered metal-amino clay layer, and is widely used for adsorption and removal of radionuclides and cations. Can be applied.

1 shows the chemical structures of methylene blue (a), chrysoidin G (CG) (b) and Fe-amino clay (Fe-AC).
Figure 2 schematically shows the formation process of the FeAC / CMC / POSS composite of the present invention.
Figure 3 shows the results of (a) XRD and (b) FT-IR analysis of FeAC, CMC, FeAC/CMC and FeAC/CMC/POSS.
Figure 4 is a SEM morphology analysis of (a) FeAC, FeAC / CMC (b and c) and (d and e) FeAC / CMC / POSS, (f) FeAC / CMC / POSS showing the presence of Fe, Si and N Is the result of element mapping.
5 is an element mapping result of FeAC/CMC/POSS showing the presence of (ae) TEM images and (f) Fe, Si and N at various magnifications for FeAC/CMC/POSS.
Figure 6 shows the TGA curves of FeAC, FeAC / CMC and FeAC / CMC / POSS.
7 shows the results of UV-vis analysis for measuring (a) flat adsorption capacity of MB and CG at various pHs (between 6 and 11), and (b) temperature of MB and (c) CG solutions.
Fig. 8(a) shows the adsorption mechanism of Cs, MB and CG, and Fig. 8(b) relates to a secondary kinetics model, suitable for adsorption of (i) Cs, (ii) MB and (iii) CG. Do.
9 shows Langmuir and Freundlich isotherm models for adsorption of (a) Cs, (b) MB and (c) CG.
10 is an XPS analysis of FeAC/CMC/POSS, (a) a survey scan spectrum, and (b) O 1s, (c) C 1s, (d) Si 2p, (e) Fe 2p and (f) It shows the spectrum of N 1.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

According to the present invention, not only radionuclides but also harmful cations can be removed together, and the adsorption removal efficiency is improved by establishment of a specific structure, and a complex is easily recovered. Such a complex of the present invention can be particularly effectively applied to remove cesium and harmful cations used as dyes.

In more detail, the complex for removing cesium and cation of the present invention includes metal-amino clay (M-AC), carboxymethylcellulose (CMC), and polyhedral oligomeric silsesquioxane (POSS) or derivatives thereof. Is to do.

The complex for removing cesium and cation of the present invention has a remarkably increased adsorption efficiency due to a specific structure, and the polyhedral oligomeric silsesquioxane is disposed between layers of layered metal-amino clay. When the polyhedral oligomeric silsesquioxane is disposed between the layers of the layered metal-amino clay as in the present invention, the interlayer spacing is expanded to facilitate the introduction of the material to be adsorbed, and sufficient space to effectively confine it is provided.

The polyhedral oligomeric silsesquioxane is preferably included in an amount of 5 to 15 parts by weight based on 1 part by weight of metal-amino clay, and more preferably 8 to 12 parts by weight based on 1 part by weight of metal-amino clay. It is included as, for example, may be included in an amount of 10 parts by weight per 1 part by weight of metal-amino clay.

At this time, if the polyhedral oligomeric silsesquioxane is less than 5 parts by weight based on 1 part by weight of metal-amino clay, there is a problem that the interlayer spacing of the metal-amino clay is not sufficiently expanded, and if it exceeds 15 parts by weight, the appearance There is a problem in that the properties are impaired and the intended structure is not obtained.

On the other hand, the carboxymethylcellulose is preferably included in an amount of 1 to 4 parts by weight based on 1 part by weight of metal-amino clay, more preferably 1.5 to 3 parts by weight based on 1 part by weight of metal-amino clay. And, for example, metal-amino clay may be included in an amount of 2 parts by weight per 1 part by weight.

When metal-amino clay and carboxymethylcellulose are used together, carboxylate ions (COO ^- Na ⁺ ) present in the main chain of carboxymethylcellulose act as ion exchange sites, and Cs ⁺ through cation exchange with Na ⁺ ions. , Involved in the adsorption of heavy metals and cationic dyes. Further, in the composite of the present invention, polyhedral oligomeric silsesquioxane is disposed between layers of layered metal-amino clay to expand the interlayer space to facilitate the introduction of substances to be adsorbed such as dyes, heavy metals, and radionuclides.

In the metal (M)-amino clay, the metal (M) is Zn ^{2 +} , Sn ^{2 +} , Ca ^{2 +} , Al ^{3 +} , Fe ^{3 +} , Ni ²⁺ , Co ^{2 +} , Cu ^{2 +} , Mn ^{2 +} , Ag ^{2 +} and Ce ^{3 +} may be at least one selected from the group consisting of, preferably Fe ^{3 +} , for example, the metal-amino clay may be iron-amino clay (FeAC). The metal-amino clay has a positively charged metal ion as a backbone, and an amine group (-NH ₂ ) is attached to both ends.

The metal (M)-amino clay that can be used in the present invention is commercially available or can be prepared by a known method. For example, 3-aminopropyltriethoxysilane (APTES) is used as a cationic metal. It can be synthesized by dropwise addition to the contained ethanol solution under atmospheric conditions (normal temperature/normal pressure), that is, by a one-pot sol-gel reaction.

In more detail, the iron-amino clay is reacted by dissolving Fe ^{3 +} Cl ₃ ·6H ₂ O in ethanol at room temperature (20-25° C.) and adding 3-aminopropyl triethoxysilane (APTES) to the above. The precipitated slurry obtained after mixing may be separated by centrifugation, washed with ethanol, and then dried at 40 to 55° C. for 6 to 48 hours, but the manufacturing method is not limited thereto. The unit structure FeAC of the iron-amino clay thus obtained consists of a central octahedral brucite-like Fe(OH) ₂ structure, and tetrahedral silica is superimposed on the upper and lower portions thereof, and the flexible -(CH ₂ ) It is capped with a vertical layer of ₃ NH ₂ groups. The schematic structure of the FeAC clay is shown in Fig. 1(c).

Polyhedral oligomeric silsesquioxane (POSS) is a nanostructured inorganic organic molecule composed of an inorganic silica-like core (Si ₈ O ₁₂ ) surrounded by eight corner groups that can be amines, esters, alcohols, isocyanates and silanes. Is one of them.

The complex of the present invention contains one or more selected from the group of polyhedral oligomeric silsesquioxane (POSS) or derivatives imparting reactivity thereto as an essential component. The polyhedral oligomeric silsesquioxane or a derivative thereof that can be used in the present invention may be at least one represented by the following formula (1).

[화학식 1]

[Formula 1]

Here, the R groups may be the same or different, at least one R group is a reactive group, and the R reactive groups are independently hydrogen, hydroxy, alkoxy, amine, epoxy, isocyanate, methacrylate, acrylate, methacrylamine, acrylic It is selected from the group consisting of amide, nitrile, norbornenyl, vinyl, styrenyl, and thiol, and the rest are R non-reactive groups, and may be selected from the group consisting of C _1-30 alkyl and C _6-30 aryl.

The complex for removing cesium and cation obtained by the present invention exhibits excellent adsorption capacity because more Cs ⁺ and cationic dye molecules can be encapsulated by increasing the interlayer space. In particular, the complex for removing cesium and cations of the present invention, for example, the FeAC/CMC/POSS complex, has -NH _{2 of} FeAC, -OH of CMC and -NH ₂ of the -COOH group at a high pH value of 10 to 11 Since deprotonation can obtain a net negative charge resulting in high adsorption of positively charged cationic MB and CG dyes, better adsorption power for cationic dyes (MB and CG) can be obtained.

According to another aspect of the present invention, a method for preparing the complex for removing cesium and cation of the present invention is provided, and in more detail, the method for preparing the complex for removing cesium and cation of the present invention is a metal-amino clay (M-AC) And preparing a first mixture obtained by mixing carboxymethylcellulose (CMC) in a solvent. Preparing a second mixture by adding polyhedral oligomeric silsesquioxane to the first mixture; Heating the second mixture to obtain a solid; And calcining the solid material.

In the preparing of the first mixture, a separate solution is prepared by mixing metal-amino clay and carboxymethylcellulose in a solvent, or a solution is prepared by mixing metal-amino clay and carboxymethylcellulose together in a solvent. step; And adding a metal-amino clay solution to the carboxymethylcellulose solution to prepare a first mixture.

Meanwhile, in the step of preparing the first mixture, the solvent is preferably purified water or water, and alcohol or the like may be used. However, the solvent is not particularly limited thereto, and is preferably purified water or water.

The step of preparing the first mixture and the second mixture is preferably carried out with stirring for 3 to 24 hours at a temperature of 50° C. or more and less than 100° C., and more preferably, a temperature of 75 to 95° C. Mixing is accompanied by stirring for 6 to 18 hours at.

For example, iron-amino clay is dispersed in deionized water and stirred at about 85° C. for about 8 hours to prepare an iron-amino clay solution, and sodium carboxymethylcellulose is separately dispersed in deionized water, and then at about 85° C. Stirring for a period of time to prepare a carboxymethylcellulose solution, stirring the iron-amino clay solution while slowly adding the carboxymethylcellulose solution, stirring was performed, and maintained at about 85° C. for about 12 hours to add amino POSS to the obtained colloidal solution. It may be further added and stirred at about 85° C. for about 12 hours to obtain the second mixture.

Thereafter, a step of obtaining a solid is performed by heating the second mixture, wherein the heating may be performed at a temperature of 100 to 200°C, preferably at a temperature of 120 to 180°C, for example, 150°C. It can be carried out at a temperature of. When the second mixture is heated, when the heating temperature is less than 100°C and exceeds 200°C, there is a problem that the change in the shape of the composite structure may be affected.

When the second mixture is heated, a solid material, more specifically a cake-like product is obtained, and then the step of firing the solid material is performed.

In this case, the sintering may be performed at a temperature of more than 200° C. and not more than 300° C., preferably at a temperature of 220 to 280° C., for example, at a temperature of 250° C. When the firing temperature is 200° C. or less, there is a problem that the amount of adsorption to the adsorbed material of the calcined material may decrease, and when it exceeds 300° C., physical properties may be deformed.

When the firing step is completed, the step of pulverizing the fired product obtained by the firing step: washing the pulverized product; And drying the washed pulverized material may be further performed. The method of pulverizing the fired product is not particularly limited, and may be performed by any method known in the art.

The pulverized product thus obtained is washed several times with ethanol, distilled water, or a combination thereof.

The washed pulverized product is subsequently dried at 30 to 90°C, preferably 45 to 75°C, to finally obtain the composite for removing cesium and cations of the present invention. In this case, the drying method is not particularly limited, and may be performed by, for example, hot air drying, oven drying, natural drying, or the like.

According to the present invention, a complex having excellent radionuclide and cation adsorption capacity is provided by electrostatic attraction, ion exchange, and surface complexation, and can be widely applied to adsorption and removal of radionuclides and cations.

Hereinafter, the present invention will be described in more detail through specific examples. The following examples are only examples to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

1. Materials and experimental methods

(1) compound

3-aminopropyltriethoxysilane (APTES, 99%), iron (III) chloride, carboxymethylcellulose (CMC, MW, 90000) and cesium chloride (CsCl) were purchased from Sigma-Aldrich (USA). Used without further purification. Cationic dye methylene blue (hereinafter'MB', C ₁₆ H ₁₈ ClN ₃ S, molecular weight 319.85 g mol-1, λmax = 664 nm) and chrysoidine G (hereinafter'CG' or basic orange 2, C ₁₂ H ₁₂ N ₄ HCl, molecular weight 248.71, λmax = 449 nm) was also obtained from Sigma-Aldrich (USA), and its structures are shown in FIGS. 1(a) and 1(b).

Stock solutions of MB and CG were used by dissolving 2000mg MB or CG in 1 liter of water. The organic modifier, aminopropylisooctyl polyhedral oligomeric silsesquioxane (POSS), was supplied from Sigma-Aldrich (USA). The pH value of the solution was adjusted using sodium hydroxide and hydrochloric acid obtained from Merck (Darmstadt, Germany).

(2) device

An XRD (X-ray diffraction) pattern was obtained using a Bruker D2 PHASER (Germany) diffraction apparatus and Cu Ka radiation.

XPS (X-ray photoelectron spectroscopy) was performed using a Thermo Scientific, K-Alpha electron spectrometer equipped with an Al X-ray source (XPS peak was equipped with CASA XPS software and the binding energy was 284.6 eV).

FTIR spectra were acquired using a Jasco FT/IR-6600 apparatus using KBr pellets at 4000-400 cm ^-1 .

An S-4800SE microscope was used to obtain an SEM image to investigate the morphology of the sample at an accelerating voltage of 15 kV.

TEM was carried out at an acceleration voltage of 200 kV using a Tecnai G2 (FEI, the Netherlands) device equipped with EDS.

TGA was performed using Tarsus TG 209 F3 at a temperature rising rate of 10°C/min at room temperature to 1000°C in a nitrogen atmosphere.

ICP-MS (Inductively Coupled Plasma Mass Spectrometry) was performed using PerkinElmer ELAN6100 and used for metal measurement.

The pH value was measured using a JENWAY3510 pH Meter.

2. Preparation of FeAC/CMC/POSS composite

Example One: FeAC / CMC / POSS Complex

(1) Preparation of Fe-amino clay (FeAC)

3-Aminopropyl-functionalized iron phyllosilicate is a previously known method (Lee, Y. -C.; Kim, EJ; Ko, DA; Yang, J. -W. Water-soluble organo-building blocks of aminoclay) as a soil-flushing agent for heavy metal contaminated soil. J. Hazard. Mater. 2011, 196, 101-108. Briefly, FeCl ₃ · 6H ₂ O (24 g) was dissolved in 250 mL of ethanol contained in a 250 mL beaker with constant stirring for 30 minutes. To this, 3-aminopropyltriethoxysilane (32 mL) was added, and the molar ratio of FeCl ₃ ·6H ₂ O and C ₉ H ₂₃ NO ₃ Si was adjusted to 0.7:1. The mixture was stirred to equilibrate for 12 hours, and the precipitated AIP clay thus obtained was washed with ethanol, washed repeatedly with water, and then centrifuged at 8000 rpm for 20 minutes. The washed clay was heated at 50° C. for 24 hours to obtain FeAC. The unit structure FeAC consists of a central octahedral brucite-like Fe(OH) ₂ structure, and tetrahedral silica is overlapped at the top and bottom, and the flexible -(CH ₂ ) ₃ NH ₂ group is vertical. Capped with a layer. The structure of the FeAC clay is shown in Fig. 1(c).

(2) Manufacture of FeAC/CMC and FeAC/CMC/POSS

The FeAC (1g) obtained in 2. (1) was dispersed in 50 mL of deionized water and stirred at 85° C. for 8 hours. Separately, sodium carboxymethylcellulose (CMC, 2.0 g) was slowly added to 100 mL of deionized water in a beaker and stirred at 85° C. for 12 hours. The FeAC solution was slowly added to the CMC solution while stirring and maintained at 85° C. for 12 hours. Amino POSS (0.1 g) was slowly added to the brick red colloid solution obtained with continuous stirring, and stirring was continued at 85° C. for 12 hours. The weight ratio of amino POSS and FeAC in the mixture was kept at 10:1. The resulting mixture was heated to 150° C. to obtain a cake-like final product, which was fired by heating at 250° C. in a muffle furnace, pulverized, washed several times with ethanol and distilled water, and 60° C. It was dried in to prepare a final product (FeAC/CMC/POSS). A schematic of the synthesis of FeAC/CMC/POSS is shown in FIG. 2.

Comparative Example 1: FeAC/CMC

FeAC/CMC was prepared by the same procedure as in Example 1, except that amino POSS was not added.

3. Adsorption experiment

(1) Adsorption isotherm

The adsorption isotherm determines the distribution of adsorbed water molecules between the solid and liquid states and the nature of the equilibrium state. The adsorption isotherm is defined using the Langmuir and Freundlich isotherm models, and the adsorption capacity is predicted using the constant given by the isotherm. The Langmuir isotherm provides a single-layer adsorption model, according to which adsorption occurs on the surface of a homogeneous adsorbent at the same site with equal energy, the same number of molecules attached to each site, and the adsorbed molecules do not interact. In this study, adsorption experiments were performed to determine the adsorption capacity of FeAC/CMC/POSS according to the concentrations of Cs, MB and CG. These adsorption experiments showed that the adsorption capacity of FeAC/CMC/POSS increased with increasing Cs, MB and CG concentrations due to the availability of many active sites. The experimental data were fitted to the Langmuir and Freundlich isotherm models (Fig. 9). According to the experimental data for Cs adsorption (Fig. 9(a)), the Langmuir model is more suitable for a model with an R ² value of 0.99 than the Freundlich model. Using the Freundlich model (Table 1), the calculated values of the constants K _F and n were 0.65 and 1.48.

Langmuir's linear and nonlinear isotherm equations are as follows.

(1)

(One)

(2)

(2)

Here, qe and qmax represent the equilibrium adsorption capacity and the single bed maximum adsorption capacity (mgg-1), respectively, and the constant KL describes the affinity between the adsorbent and the adsorbate.

Meanwhile, the Freundlich adsorption isotherm model is based on an empirical formula that predicts multilayer adsorption on heterogeneous adsorption surfaces with different adsorption energies. The Freundlich model is described by the following equation.

(3)

(3)

(4)

(4)

KF is related to the multilayer adsorption capacity of the adsorbent, and n determines the adsorption strength.

Parameters of Langmuir and Freundlich models for adsorption of Cs, MB and CG by FeAC/CMC/POSS absorbent Langmuir parameters Freundlich parameter K _L (L/mg) q _max (mg g ^-1 ) R ² K _F (L/mg) n R ² Cs 0.0009 152.16 0.99 0.65 1.48 0.98 MB 0.0352 438.34 0.96 61.03 3.15 0.79 CG 0.0104 791.91 0.96 98.04 3.56 0.81

As a result of experimental data and isotherm analysis, the equilibrium Cs ⁺ ion adsorption capacity (qe) of the FeAC/CMC/POSS complex was 152.16 mg g ^{-1, which} was higher than that previously reported (Table 2). Component of FeAC / CMC / POSS has played a role in the adsorption of Cs + ions through the respective electrostatic attraction, ion exchange and surface complexes, Cs ⁺ ions are attracted by a deprotonated amine (-NH ₂ on the FeAC) or a hydroxyl group It attaches to the clay by forming coordination bonds with nitrogen or oxygen atoms. Carboxy methyl cellulose present in FeAC/CMC/POSS has a large number of carboxylates (COO-Na ⁺ ) and hydroxyl groups (-OH) in its main chain, and these are more Cs ⁺ exchange and electrostatic attraction by ionic bonding. Makes it possible. Further, the increased amount of Cs ⁺ ion adsorption may be caused by expansion of the inter-lamellar space of FeAC due to incorporation of POSS molecules and Cs ⁺ ion encapsulation.

Adsorption capacity of Cs ⁺ ions, MB and CG in FeAC/CMC/POSS and other reported substances Adsorbents Adsorbates q _max (mg g ^-1 ) Montmorillonite-Prussian blue hybrid Cs 57.47 Ammonium-pillared montmorillonite-CoFe ₂ O ₄ 86.46 K ₂ Zn ₃ [Fe(CN) ₆ ]] ₂ @Ni-P complex 54.95 rGO/Fe ₃ O ₄ (Reduced graphene oxide/Magnetite 128.2 Prussian Blue/Cellulose Airgel (PB/CA) 13.70 FeAC/CMC/POSS 152 MMT/Fe ₂ O ₃ MB 71.12 Dodecyl sulfobetaine-modified montmorillonite 150.2 Organo-bentonite/sodium alginate 414 Magnetic Montmorillonite / Chitosan 82 Moroccan clay 135 FeAC/CMC/POSS 438 CuS-NP-AC (Copper sulfide nanoparticle loaded activated carbon) CG 89.3 FeAC/CMC/POSS 791

Adsorption studies for cationic dyes MB (Fig. 9(b)) and CG (Fig. 9(c)) showed that the Langmuir isotherm model fits better with R ² values of 0.96 and 0.96, respectively. The KF and n values calculated using the Freundlich model were 61.03 and 3.15 for MB system and 98.04 and 3.55 for CG, respectively (Table 2). Langmuir model showed that FeAC/CMC/POSS had impressive qmax values of 438.34 and 791.91 mg g-1 for MB and CG, respectively.

(2) adsorption kinetics

Adsorption rate provides an important means of determining the adsorption mechanism and the ability of the adsorbent to remove contaminants. The kinetic parameters determined experimentally were calculated using the plot of Fig. 8(b) and shown in Table 3.

Kinetic parameters of pseudo-first-order and pseudo-second-order models for Cs, MB and CG adsorption by FeAC/CMC/POSS Initial concentration C ₀ (mgL ^-1 ) 1st model Quadratic model k ₁ (min ^-1 ) q _e (mg g ^-1 ) R ² k ₂ (gmg ^{- 1} min ^-1 ) q _e (mgg ^-1 ) R ² Cs-50 0.0081 0.4736 0.6162 0.1329 4.5188 0.9999 MB-100Y:\C&S\Sookyung Jeong\Drawings 2019\DPP18-1292-EN 0.0116 4.6037 0.7148 0.0146 48.5437 0.9999 CG-100 0.0105 3.7553 0.7874 0.0222 45.7247 0.9999

The secondary kinetics of Cs adsorption had qe and k2 values of 4.5188 mg g-1 and 0.13290 g mg-1 min-1, respectively (Table 3). The results showed that the second-order model of U showed better suitability than the first-order model of having an R2 value of 0.9999, and that the FeAC/CMC/POSS adsorption rate was dependent on the active site, not the access cesium concentration. Secondary kinetics analysis for MB and CG showed qe and k2 values of 48.5437 mg g-1 and 0.0146 g mg-1 min -1 for MB and 45.7247 mg g-1 and 0.0222 g mg-1 min-1, respectively. Was calculated. For CG, these results showed that the second order kinetics fit better with R2 values of 0.9999 and 0.9999 for MB and CG, respectively. In particular, this R2 value was much higher than the value assumed for pseudo-first-order kinetics, and the calculated q value was in good agreement with the experimental data. Thus, the 2nd order kinetics of s well explains the adsorption behavior of Cs, MB and CG on FeAC/CMC/OSS.

(3) Evaluation of adsorption properties of FeAC/CMC/POSS composites

Cesium ions (Cs ⁺ ) and two cationic dyes (MB and CG) were used to evaluate the adsorption properties of the FeAC/CMC/POSS complex. Adsorption isotherms were obtained by performing batch experiments at different adsorbate and solution pH values. The initial Cs concentration varied from 1 to 500 mg L ^-1 . A fixed amount of adsorbent (20 mg) was added to 20 mL of an aqueous solution of cesium, and when equilibrium was reached, the mixture was shaken at 40 rpm for 24 hours using a rotary shaker. The adsorbent was recovered, separated by filtration, and the cesium concentration was analyzed by ICP-MS. For the dye adsorption experiment, 20 mg of FeAC/CMC/POSS was dispersed in 20 mL of MB or CG solution at a concentration of 1 to 3000 mg L ^-1 while gently stirring. The adsorption capacity at equilibrium was calculated using the following equation (1).

(1)

(One)

Where q _e is the equilibrium adsorption capacity (mg g ^{- 1} ) at t min (min), C ₀ and C _t are the adsorbate concentration after 0 and t min (mg L ^{- 1} ), respectively, and V is the solution volume ( mL), and m is the adsorbent mass (g). Experiments were conducted by varying the pH, dose rate and contact time. The pH value was varied between 5 and 11 using dilute HCl and NaOH.

As a result of the adsorption experiment, the FeAC/CMC/POSS composite showed an unexpected amount of superior cesium ion adsorption performance compared to the cesium adsorption capacity of each component.This is confirmed in the following XRD analysis when POSS molecules are incorporated between the layered structures. This is because the interlayer spacing is extended from 12.83Å to 14.53Å as possible, so that such interlayer space provides sufficient space to trap cesium ions having a much smaller diameter (0.226 nm). A schematic mechanism of adsorption of cesium by the composite of the present invention is shown in Fig. 8(a).

Furthermore, MG and CG molecules also showed high affinity for FeAC/CMC/POSS and were easily adsorbed. At high pH, the amino groups (-NH ₂ ) on the clay surface are deprotonated to obtain a pure negatively charged surface charge. These negatively charged clay surfaces electrostatically attract positively charged cationic dyes. In addition, the improved cation adsorption capacity of the FeAC/CMC/POSS complex may be due to the conversion of siloxane to negatively charged silanol groups at high pH 10, and these negatively charged silanol groups are adsorbed by hydrogen bonding. The dose can be increased. In addition, at elevated pH, ionization of the carboxyl group (-COOH) of the CMC backbone may electrostatically interact with MB and CG (FIG. 8). In addition, the FeAC/CMC/POSS composite of the present invention obtained a structure capable of accommodating a relatively large number of MB and CG molecules by expanding the interlayer spacing of FeAC by incorporating POSS molecules.

Accordingly, the high adsorption capacity of the FeAC/CMC/POSS composite of the present invention is (i) electrostatic attraction between surface functional groups (deprotonated amine and silanol groups at high pH) and cationic dyes, 　 (ii) abundant surface carboxyl groups on CMC. And the electrostatic attraction between the hydroxyl group and the cationic dye, (iii) the additional confinement of the dye molecules in the interlayer space of FeAC expanded by POSS (Fig. 8).

4. Structure observation

(1) X-ray diffraction pattern

The textures, structures and interlayer spacing of the fabricated material were determined by XRD. Figure 3 shows the X-ray diffraction patterns of CMC, FeAC, FeAC/CMC and FeAC/CMC/POSS.

The XRD of CMC shows a semi-crystalline nature with peak 2θ = 19.81°. FeAC is at 2θ values of 6.87°, 11.31°, 22.23°, 35.56° and 59.93° corresponding to the (001), (002), (020, 110), (130, 200), and (060, 330) planes. It represents broad in-plane reflection peaks. The interplanar spacing of the FeAC prepared above is d ₀₀₁ = 12.83 Å, d ₀₀₂ = 0.78, d ₀₂₀ , 110 = 0.39 nm, d _130,200 = 0.25 nm and d _{060, 330} = 0.15 nm. The low-angle inerlayer d ₀₀₁ reflection at 2θ = 6.87° (d ₀₀₁ = 12.83Å) and the low-intensity smectite reflection at 2θ = 60.03° (plane 060) are the organics of 1:1 stacked phylosilicate. -It was observed to be an inorganic hybrid layered clay structure. The layer structure of the FeAC clay was further confirmed by HR-TEM.

The formation of the FeAC/CMC clay-polymer complex became evident as the characteristic peak of FeAC shifted to a lower 2θ value after CMAC addition.

The characteristic peaks of FeAC/CMC/POSS showed a clear peak shift with a low 2θ value compared to FeAC/CMC due to the addition of POSS. This peak shift indicates that the POSS molecules are intercalated between the layers of FeAC and expand the interlayer space. After the change by POSS, the basic spacing (d001 value) of FeAC increased from 12.83 Å to 14.53 Å as evidenced by its property shifting from 6.87° to 6.08°. In the spectra of FeAC/CMC and FeAC/CMC/POSS, the strong diffraction peaks located at 31.6°, 45.32° and 56.43° may be due to trace amounts of crystalline Si and FeSi ₂ formed during the firing process.

The main functional groups of the CMC are hydroxyl (-OH), methylene (-CH ₂₎ and carboxylate (COO ^-) is characterized by a peak in the groups 3483, 2878 and 1602 cm ^-1 corresponding to each. The main characteristic peaks of FeAC are -OH (3451 cm ^-1 ), -CH ₂ (3026 cm ^-1 ), -NH ³⁺ (2010 cm ^-1 ), -NH ₂ (1605 cm ^-1 ), Si-O- Si (1102 cm ^-1 ), Fe-O-Si (692 cm ^{- 1} ) and Si-O (478 cm ^{- 1} ), which are consistent with previous studies. FeAC/CMC and FeAC/CMC/POSS show changes in intensity and peak, and the peak shifts compared to FeAC and CMC due to the -OH stretching vibrations of CMAC. The intensity of the NH ₃ ⁺ peak (2010 cm-1) of FeAC was found to decrease in FeAC/CMC and FeAC/CMC/POSS, indicating that the amine group of FeAC is involved in the reaction of FeAC and CMC. In addition, when FeAC and CMC are added, a pair of intense peaks occur around 2878 and 2953 cm ^-1 in both FeAC/CMC and FeAC/CMC/POSS, which is -CH ₂ and -CH ₃ by CMC addition. It may be due to the symmetrical and asymmetrical vibration of. The absorption peaks of 1611 and 1630 cm ^-1 in the spectra of FeAC/CMC and FeAC/CMC/POSS can be attributed to carboxamide as a result of the reaction between the carboxy group of CMC and -NH ₂ on the surface of -FeAC. The strength of the carboxamide and Si-O-Si stretching vibrations is higher in FeAC/CMC/POSS than in FeAC/CMC due to the addition of -NH ₂ and Si-O-Si groups of POSS. This indicates the presence of POSS in the FeAC/CMC/POSS complex.

(2) SEM and TEM confirmation

SEM and TEM characterizations were used to observe the morphology of FeAC and its complexes (FeAC CMC and FeAC/CMC/POSS). Figure 4(a) shows an SEM image of FeAC. The shape of the FeAC/CMC complex showed pores in a specific study area due to the addition of CMAC with FeAC (Fig. 4(b)), but most of the areas showed agglomerated sharp flake shape (Fig. 4(c)). ). On the other hand, SEM images of FeAC/CMC/POSS (FIGS. 4(d) and (e)) show the smooth layer of non-aggregated flakes derived by the addition of POSS. Incorporation of POSS by intercalation leads to the layered form of FeAC. The presence of Si, N, and Fe in the FeAC/CMC/POSS composite was confirmed by elemental mapping (Fig. 4(f)).

Furthermore, Figures 5(a) to (e) show HR-TEM images of FeAC/CMC/POSS, and the incorporation of POSS enables excellent dispersion of the modified clay in the CMC matrix, remarkable layer formation, and clay plates. I did. The edge views of FeAC/CMC/POSS (Figs. 5(d) and (e)) show a clear layered structure and inserted clay sheets arranged in a regular and uniform manner. Elemental mapping (Fig. 5(f)) confirms the presence of Si, Fe, O and C in the composite.

(3) Check the TG curve

The TG curves of FeAC, FeAC/CMC and FeAC/CMC/POSS are shown in FIG. 6. Multiple decomposition patterns were observed in all three samples, and the decomposition process of all of them resulted in the first major weight loss below 200 °C, which is believed to be due to the evaporation of the adsorbed water and dehydration of the water molecules absorbed between the pores and silicate layers. Showed. The weight loss in the second (240-450°C) and third (450-600°C) steps in FeAC is due to the decomposition of the aminopropyl functional group and the dehydroxylation of the silanol group, respectively. Regarding FeAC/CMC, mixing CMC slightly increases the thermal stability of FeAC, and the second (270-400°C) and third (> 400°C) of the polymer backbone through thermal decomposition and polar interactions of carboxymethylcellulose. Each corresponds to the evaporation of water molecules tightly bound to the carboxyl group. This incorporation of the clay into the polymer matrix improves thermal stability. On the other hand, in relation to FeAC/CMC/POSS, the mass loss at 300 ~ 450°C is due to the decomposition of the incorporated POSS modifier, and the weight loss above 450°C corresponds to the decomposition of structural hydroxyl groups. FeAC/CMC/POSS showed much higher thermal stability than FeAC/CMC due to the molecular stiffness of POSS and the thermal stability of Si-O from POSS.

(4) XPS analysis

The chemical composition and oxidation state of the elements present in FeAC/CMC/POSS were determined by XPS. Sharp peaks in the full scan survey spectrum (Fig. 10(a)) indicate the presence of C, O, Si, Fe and N on the surface of the FeAC/CMC/POSS composite. In the O1s spectrum of FeAC/CMC/POSS (FIG. 10(b)), six different peaks centered on the binding energies of 530.39, 531.14, 532.04, 532.73, 532.86 and 535.43 eV were observed, which are Si-O-Si, O=CO, SiO2, Si-OH, C-OH, and CO-Si groups respectively. The C 1s spectrum of FeC/CMC/POSS (FIG. 10(c)) was deconvoluted into five peaks with binding energy, and SiC, CN, CC, CO and OC = 283.88 and 285.55 corresponding to O groups, respectively. , 284.67, 286.23, and 288.0 eV peaks. The main peaks of the Si 2p spectrum of FeAC/CMC/POSS (FIG. 10(d)) are 100.73, 101.822, 102.77, indicating the presence of FeSi ₂ , Si-O-Si, Si-OH, SiO ₂ and Si-OC, respectively. It was deconvolved into five configurations of 103.78 and 105.15 eV. Fe 2p spectrum (Fig. 10 (e)) is a peak corresponding to Fe2P _3/2 and Fe2p _1/2, respectively indicated at 711.55 and 724.39eV showed the formation of Fe ₃ O _4. In the N 1s spectrum of FeAC/CMC/POSS (FIG. 10(f)), the peak at 399.6 eV was arranged with amine (-NH ₂ ) nitrogen and NH ³⁺ groups at 401.78 eV.

Referring to Table 4, it can be seen that the higher the atomic ratio of Si in FeAC/CMC/POSS compared to FeAC/CMC, the POSS was mixed in FeAC/CMC.

Atomic percentage of various elements (Si, Fe, N, O, C and Cs) and peak binding energy obtained from XPS analysis element FeAC/CMC FeAC/CMC/POSS FeAC/CMC/POSS(Cs Adsorbed) Atomic% Peak BE Atomic% Peak BE Atomic% Peak BE Si 2.16 102.39 7.1 102.71 4.2 102.11 Fe 1.13 711.18 1.51 710.76 1.41 713.49 N 3.03 400.28 2.88 399.79 2.72 399.83 O 29.03 532.46 30 532.13 32.4 532.12 C 64.66 285.39 58.51 285.03 59.04 285 Cs - - - - 0.24 725.03

5. Effect of pH

pH can affect the charge transfer between the interface in liquid and solid. Adsorption of Cs ⁺ ions, MB and CG can be affected by the pH of the solution. The adsorption activity of FeAC/CMC/POSS was evaluated in Cs ⁺ , MB and CG solutions with pH varying between 5 and 11.

FeAC/CMC/POSS showed a non-negligible difference in the adsorption capacity of Cs ⁺ ions in the range of pH 5 to 11, so the adsorption study of Cs ⁺ ions was carried out at neutral pH in pure water, which is This means that the adsorbent treats Cs ⁺ ions over a wide pH range.

On the other hand, the FeAC/CMC/POSS complex showed higher adsorption to cationic dyes (MB and CG) at a high pH value of 10 pH (Fig. 7). At low pH, the protonation of amino groups (existing on the surface of FeAC), hydroxyl groups and carboxyl groups (existing in the main chain of CMC) causes electropositivity in FeAC/CMC/POSS, resulting in positively charged cation. This may be because it interferes with the adsorption of the MB and CG dyes. Conversely, at high pH, -NH ₂ of FeAC, -OH of CMC and -NH ₂ of -COOH group are deprotonated to obtain a net negative charge resulting in high adsorption of positively charged cationic MB and CG dyes. .

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations are possible without departing from the technical spirit of the present invention described in the claims. It will be obvious to those of ordinary skill in the field.

Claims (12)

Metal-amino clay (M-AC), carboxymethylcellulose (CMC) and polyhedral oligomeric silsesquioxane (POSS) or derivatives thereof, and the polyhedral oligomeric silsesquioxane is a layered metal- A complex for removing cesium and cations, disposed between layers of amino clay.
The complex for removing cesium and cations according to claim 1, wherein the polyhedral oligomeric silsesquioxane is contained in an amount of 5 to 15 parts by weight based on 1 part by weight of metal-amino clay.
The composite of claim 1, wherein the carboxymethylcellulose is contained in an amount of 1 to 4 parts by weight based on 1 part by weight of metal-amino clay.
delete According to claim 1, In the metal-amino clay (M-AC), the metal (M) is Zn ^{2 +} , Sn ²⁺ , Ca ^{2 +} , Al ^{3 +} , Fe ^{3 +} , Ni ^{2 +} , Co ^{2 +} , Cu ^{2 +} , Mn ^{2 +} , Ag ^{2 +} and Ce ^{3 +} At least one selected from the group consisting of, cesium and cation removal complex.
The complex for removing cesium and cations according to claim 1, wherein the polyhedral oligomeric silsesquioxane or a derivative thereof is at least one represented by the following formula (1).

[Formula 1]
(Wherein, R groups may be the same or different, one or more R groups are reactive groups, and the R reactive groups are independently hydrogen, hydroxy, alkoxy, amine, epoxy, isocyanate, methacrylate, acrylate, methacrylamine, It is selected from the group consisting of acrylamide, nitrile, norbornenyl, vinyl, styrenyl, and thiol, and the rest are R non-reactive groups, selected from the group consisting of C _1-30 alkyl and C _6-30 aryl.)
Preparing a first mixture in which a metal-amino clay (M-AC) and carboxymethylcellulose (CMC) are mixed in a solvent;
Preparing a second mixture by adding polyhedral oligomeric silsesquioxane to the first mixture;
Heating the second mixture to obtain a solid; And
Firing the solid material
Comprising a method for producing a complex for removing cesium and cations.
The method of claim 7, wherein the preparing of the first mixture comprises mixing metal-amino clay and carboxymethylcellulose in a solvent to prepare a separate solution and mixing them, or metal-amino clay and carboxymethylcellulose. A method of preparing a complex for removing cesium and cations, which is performed including preparing a solution by mixing them with a solvent.
The method of claim 7, wherein the step of preparing the first mixture and the second mixture is carried out with stirring for 3 to 24 hours at a temperature of 50° C. or more and less than 100° C., preparation of a complex for removing cesium and cations Way.
The method of claim 7, wherein the heating is performed at a temperature of 100 to 200°C.
The method of claim 7, wherein the sintering is performed at a temperature of more than 200°C and not more than 300°C.
The step of pulverizing the fired product according to claim 7, obtained by firing:
Washing the ground material; And
Drying the washed ground material
A method for producing a complex for removing cesium and cation further comprising a.

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