Novel Polymeric Chelating Fibers for Selective Removal of Mercury

We report here the synthesis and characterization of two new classes of chelating fibers, namely, (1) polymercaptopropylsilsesquioxane (PMPS) and (2) ...
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Environ. Sci. Technol. 2003, 37, 4261-4268

Novel Polymeric Chelating Fibers for Selective Removal of Mercury and Cesium from Water CHUNQING LIU, YONGQING HUANG, NATHANIEL NAISMITH, AND JAMES ECONOMY* Department of Materials Science and Engineering, University of Illinois, 1304 West Green Street, Urbana, Illinois 61801 JONATHAN TALBOTT Illinois Waste Management and Research Center, One East Hazelwood Drive, Champaign, Illinois 61820

We report here the synthesis and characterization of two new classes of chelating fibers, namely, (1) polymercaptopropylsilsesquioxane (PMPS) and (2) copper(II) ferrocyanide complexed with poly[1-(2-aminoethyl)-3aminopropyl]silsesquioxane (Cu-FC-PAEAPS) fibers. These fibers were evaluated for selective removal of trace amount of mercury and cesium ions respectively in the presence of competing metal ions from water. The PMPS and Cu-FC-PAEAPS fibers were prepared by coating their corresponding soluble prepolymers, which are derived from mercaptopropyltrimethoxysilane and [1-(2-aminoethyl)3-aminopropyl]trimethoxysilane monomers, respectively, on a glass fiber substrate, followed by a cross-linking step at 120 °C. The fibers were characterized through infrared spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). These novel materials are extremely efficient in removing low concentrations of mercury and cesium ions from water in the presence of high concentrations of sodium or potassium ions. They were shown to remove trace mercury and cesium contaminants effectively to well below parts per billion concentrations under a variety of conditions.

Introduction Mercury pollution has been identified as a serious problem at waste-contaminated sites (1). One estimate of the total annual global input of mercury to the atmosphere from all sources including natural, anthropogenic, and oceanic emissions is 5500 tons (2), prompting the establishment of increasingly stringent government regulations demanding that levels of this contaminant be lowered. Radioactive cesium contamination of water is also of serious social and environmental concern since it is a significant fraction of the radioactivity of the liquid waste (3). The separation of mercury and cesium from various solutions has been done for many years principally using ion exchange, solvent extraction, or precipitation processes. However, all of these processes have some impediments for use in industrial applications. For example, there are a number of drawbacks associated with the traditional approach to ion exchange bead synthesis. During functionalization of the polymeric systems, swelling * Corresponding author phone: (217)333-9260; fax: (217)333-2736; e-mail: [email protected]. 10.1021/es0343104 CCC: $25.00 Published on Web 08/19/2003

 2003 American Chemical Society

agents must be used to reduce effects of osmotic shock and to maintain the spherical form of the bead. Furthermore, environmentally unfriendly solvents used including toluene, methylene chloride, perchloethylene, and carbon tetrachloride, etc. are used in the synthesis and carry an added expense not only in their initial cost but also in the EPA requirements for handling spent solvents (4, 5). In recent years, Economy et al. (6-8) have developed a new family of polymeric ion-exchange fibers using low-cost glass fibers as substrate that display a number of important advantages over conventional ion-exchange beads. These include simplification of the overall synthesis including faster more efficient functionalization, elimination of toxic solvents, and overall process simplification. Another advantage of the fibers is their ability to be easily fabricated into other geometries including felts, papers, or fabrics, which exhibit a greatly improved contact efficiency with the media. This enhances both the rates of reaction and regeneration. Additionally, physical and mechanical requirements of strength and dimensional stability have been achieved by use of a glass fiber substrate. The ion exchange fibers have the potential to remove a wide range of contaminant ions from water such as mercury, cadmium, lead, and cyanide ions as well as radioactive ions such as cesium and strontium. However, the ion exchange fibers are not particularly selective to remove specific toxic ions from water in the presence of high concentrations of nontoxic ions such as sodium and potassium. Recently, a new encouraging branch of research has evolved on the synthesis of rationally designed materials capable of specifically removing mercury or cesium from aqueous systems (9-19). In particular, through the marriage of ordered mesoporous silica materials with self-assembled monolayer chemistry, a powerful new class of sorbent materials functionalized with thiol groups (13) or copper(II) ferrocyanide groups (19) has been designed for remediation of mercury and cesium contamination, exhibiting both excellent binding capacity as well as binding selectivity for mercury and cesium ions, respectively. However, environmentally hazardous solvents, such as toluene, were used in the functionalization process of the materials (13, 19). Furthermore, the final product is generally limited to small particles, which may require costly containment systems. Thus exploration of alternate synthesis strategies for preparing thiol- and copper(II) ferrocyanide-functionalized new adsorbents may yield more cost-effective preparation techniques. In the present study, we designed two new kinds of chelating fibers that show extremely high selectivity for mercury and cesium respectively, by coating a low-cost glass fiber substrate with organosilsesquioxane prepolymers, followed by a cross-linking step. The polymeric chelating materials as fibers do not need complex synthetic procedures and expensive containment systems, unlike the powder form of mesoporous organosilica materials.

Experimental Methods Materials. Mercaptopropyltrimethoxysilane and [1-(2-aminoethyl)-3-aminopropyl]trimethoxysilane were purchased from Gelest Inc. and used without further purification. The substrate fiber was a nonwoven fiberglass mat, Craneglass 230 (0.015 nominal, fiber diameter of 6.5 µm), made by CRANE & CO. Characterization. FTIR spectra of the polymers were obtained on KBr pellets using a Nicolet Magna IR TM spectrophotometer 550. A Varian Mercury 400 spectrometer VOL. 37, NO. 18, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 1. Synthesis of PMPS fibers. operating at 400.2 MHz (1H) and 100.6 MHz was used to record 1H and 13C NMR spectra. 29Si NMR spectra were obtained with a Varian Chemagnetics Infinity Plus 500 spectrometer operating at 99.3 MHz. Average molecular weights (Mn) and distributions were measured using gel permeation chromatography (GPC) performed in N-methylpyrolidinone (NMP) with 0.05 M LiBr at 25 °C. GPC was carried out using a series of three light scattering (7.8 × 300 mm) columns filled with a mixed bed of 10 µm Polymer Laboratories Pl gel, a Waters 515 HPLC pump, and a Viscotek model 300 triple detector array. Polystyrene was used as a standard for the calculation of the Mw. TGA measurements were performed on a Hi-Res TA Instruments 2950 Thermogravimetric Analyzer. SEM images were acquired using a Hitachi S4700 scanning electron microscope with an acceleration voltage of 5 kV. Mercury was determined in adsorption isotherm solutions with a PS Analytical Cold Vapor Atomic Fluorescence Spectrometer. Sodium was measured with a Varian 300+ Atomic Absorbance (AA) Spectrometer. A Thermo Elemental ExCell Inductively Coupled Plasma Mass Spectrometer (ICP-MS) was used to determine solution concentrations of Cs, Cr, Zn, Ag, Ba, and Pb. Synthesis of Mercaptopropylsilsesquioxane (MPS) Prepolymer. To a stirred 50 mL round-bottomed flask containing 19.6 g (0.1 mol) of mercaptopropyltrimethoxysilane was added 0.01 g (0.078 mmol) of 30% aqueous hydrochloric acid at room temperature. The acidified silanes were then hydrolyzed by the dropwise addition of 5.4 g (0.3 mol) of water. The reaction mixture was allowed to stir at room temperature for 2 h and then at 60 °C for 12 h. All the low molecular weight components including methanol, water, hydrolyzed mercaptopropyltrimethoxysilane, etc. were removed under reduced pressure. Yield: 94%. The resulting sticky oil was diluted with ethanol to produce two MPS solutions with 10 wt % (MPS-10%) and 20 wt % (MPS-20%) concentrations. 4262

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Synthesis of 1-(2-Aminoethyl)-3-aminopropylsilsesquioxane (AEAPS) Prepolymer. To a stirred 50 mL roundbottomed flask containing 10.0 g (45 mmol) of [1-(2aminoethyl)-3-aminopropyl]trimethoxysilane was added dropwise a sodium hydroxide aqueous solution (0.03 g (0.75 mmol) of NaOH in 2.43 g (0.14 mol) of water) at room temperature. The reaction mixture was allowed to stir at 60 °C for 3 h and then at 80 °C for 12 h. All the low molecular weight components including methanol, water, hydrolyzed [1-(2-aminoethyl)-3-aminopropyl]trimethoxysilane, etc. were removed under reduced pressure. Yield: 96%. The resulting sticky oil was diluted with ethanol to produce two AEAPS solutions at 10 wt % (AEAPS-10%) and 20 wt % (AEAPS-20%). Preparation of Thiol-Functionalized Polymercaptopropylsilsesquioxane (PMPS) Chelating Fibers. A glass fiber substrate was dip-coated with a MPS-10% (or MPS-20%) solution for 1 min, and placed on a fine mesh screen. The coated glass fibers were dried in a hood at room temperature for 30 min. The dried fibers were cured at 80 °C for 12 h and then at 120 °C for 48 h in a vacuum oven. The cured fibers were allowed to cool to room temperature slowly and weighed immediately. The final thiol-functionalized chelating fibers prepared from MPS-10% and MPS-20% coating solutions are designated as PMPS-10% and PMPS-20%, respectively. Weight gains for the PMPS-10% and PMPS-20% fibers after coating were 50% and 85%, respectively. Preparation of Ethylenediamine-Functionalized Poly[1-(2-aminoethyl)-3-aminopropyl]silsesquioxane (PAEAPS) Chelating Fibers. A glass fiber substrate was dip-coated with a AEAPS-10% (or AEAPS-20%) solution for 1 min and placed on a fine mesh screen. The coated glass fibers were dried in a hood at room temperature for 30 min. The dried fibers were cured at 80 °C for 12 h and then at 120 °C for 72 h in a vacuum oven. The cured fibers were allowed to cool to room temperature slowly and weighed immediately thereafter to determine yield. The final ethylenediamine-func-

FIGURE 3. FTIR spectra of (a) original Crane-230 glass fiber substrate and (b) PMPS-10% fiber.

FIGURE 2. 1H NMR spectra of (a) mercaptopropyltrimethoxysilane and (b) MPS (solvent: ethanol-d6). tionalized chelating fibers prepared from AEAPS-10% and AEAPS-20% coating solutions were designated as PAEAPS10% and PAEAPS-20%, respectively. Weight gains for the PAEAPS-10% (from AEAPS-10%) and PAEAPS-20% (from AEAPS-20%) fibers after coating were 40% and 74%, respectively. Immobilization of Copper(II) onto PAEAPS Chelating Fibers (Cu-PAEAPS). PAEAPS-10% (0.3 g) (or 0.2 g of PAEAPS20%) fibers were stirred in a 100 mL aqueous solution of 0.06 M copper(II) chloride for 6 h to produce Cu-PAEAPS-10% and Cu-PAEAPS-20% fibers, respectively. The metallized fibers were collected, washed with DI water, washed in 2-propanol, and dried in oven at 80 °C overnight to give Robin’s egg blue fibers. Immobilization of Ferrocyanide onto Cu-PAEAPS-10% and Cu-PAEAPS-20% Fibers (Cu-FC-PAEAPS). Cu-PAEAPS10% (1.0 g) (or 0.5 g of Cu-PAEAPS-20%) in chloride form was converted to the hexacyanoferrate (II) form by shaking with a 50 mL solution of 0.25 M Na4Fe(CN)6 for 3 h. The fibers were thoroughly washed with high purity water to remove dissolved salts, air-dried, and stored for use. The final composite fibers were reddish brown in color and designated as Cu-FC-PAEAPS-10% and Cu-FC-PAEAPS-20% from Cu-PAEAPS-10% and Cu-PAEAPS-20%, respectively. Hydrolytic Stability Test of PMPS and PAEAPS Fibers. The PMPS (or PAEAPS) fibers were mixed with water and refluxed for 2 days. The fibers were then dried at 80 °C for 12 h in a vacuum oven, allowed to cool to room-temperature slowly, and weighed.

FIGURE 4. SEM images of (a) original Crane-230 glass fiber substrate and (b) PMPS-10% fiber. Equilibration Adsorption Isotherm Experiments of PMPS Fibers with Mercury Solutions. Tenth gram samples of PMPS-10% (or PMPS-20%) fibers were equilibrated with 10 mL solutions containing various concentrations of mercury at room temperature. After the mixtures were shaken for 2 h, they were filtered through a 0.22 µm Nylon 66 filter and analyzed by atomic fluorescence for residual metal content. Mercury Sorption Kinetics. Kinetic experiments were conducted in the same fashion as the adsorption isotherm experiments, except that the mixtures were shaken for 1 min, 5 min, 30, 60, and 120 min, respectively, then filtered through VOL. 37, NO. 18, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 5. Synthesis of PAEAPS fibers. a 0.22 µm Nylon 66 filter, and analyzed by atomic fluorescence for residual metal content. Regeneration Studies on Mercury-Loaded PMPS Fibers. Mercury-loaded PMPS-10% fibers were soaked in a concentrated HCl (10.1 M) solution for 12 h. The mixture was filtered, and the mercury concentration in the filtrate was determined by Atomic Fluorescence Spectrometry. The leached fibers were rinsed with DI water and oven dried at 60 °C overnight prior to reuse. Tenth gram samples of leached PMPS-10% fibers were allowed to equilibrate in 10 mL solutions of 3.0 ppm mercury and 2300 ppm sodium for 2 h with shaking at room temperature. The solution was filtered through a 0.22 µm Nylon 66 filter and analyzed for mercury by Atomic Fluorescence Spectrometry and for sodium by AA. Equilibrium Adsorption Isotherm Experiments of CuFC-PAEAPS Fibers with Cesium Solutions. Tenth gram samples of Cu-FC-PAEAPS-10% (or Cu-FC-PAEAPS-20%) fibers were allowed to equilibrate at room temperature in 10 mL of solutions containing various concentrations of cesium for 2 h with shaking. After equilibration the solution was filtered through a 0.22 µm Nylon 66 filter and analyzed by ICP-MS for residual metal content. Cesium Sorption Kinetics. Kinetic experiments were conducted in the same fashion as equilibrium adsorption isotherm experiments, except that the mixtures were shaken for 1 min, 5 min, 30, 60, and 120 min, respectively, then filtered through a 0.22 µm Nylon 66 filter, and analyzed by ICP-MS for residual metal concentrations.

Results and Discussion Synthesis and Characterization of Thiol-Functionalized PMPS Fibers. Thiol functional groups have been recognized to be efficient chelating ligands for mercury and other heavy metals such as lead and silver. Here, we incorporate the thiol 4264

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groups into the side chains of cross-linked polysilsesquioxane coated glass fibers in order to efficiently remove mercury from contaminated aqueous solutions. Trimethoxysilane with a thiol group was used to prepare mercaptopropylsilsesquioxane (MPS). The MPS was synthesized by hydrolysis and condensation of mercaptopropyltrimethoxysilane in the presence of hydrochloric acid catalyst (Figure 1). Figure 2 illustrates the 1H NMR spectra of mercaptopropyltrimethoxysilane monomer and MPS. The strong sharp peak at 3.5 ppm, representing methoxyl group hydrogens in the spectrum of the monomer (Figure 2a), disappears in the spectrum of MPS (Figure 2b, the weak peak at 3.55 ppm is from EtOD) and indicates complete hydrolysis of the Si-OCH3 groups. Moreover, the peaks assigned to Si-CH2, Si-CH2-CH2, and Si-CH2CH2CH2 in the spectrum of MPS are broad compared with the sharp peaks in the spectrum of the monomer, suggesting formation of the prepolymer. MPS has an average molecular weight (Mn) of 1650 and a polydispersity of 3.4 as measured by GPC. 29Si NMR shows that it has two characteristic signals of T2 and T3, with a ratio of 45:55. The thiol-functionalized MPS solution was dip-coated on a Crane-230 glass fiber substrate, followed by curing to form an insoluble cross-linked network structure. The FTIR spectra of the original Crane-230 fiber and PMPS-10% fiber are shown in Figure 3. It can be seen that there is no apparent absorption band in the spectrum of the original fiber, while several absorption bands appear in Figure 3b after coating. An absorption band displayed in Figure 3b at 2559 cm-1 is characteristic of a stretching vibration for thiol groups. The broad band from 3600 to 3100 cm-1 is a conspicuous feature of an O-H stretching vibration and indicates the existence of some Si-OH groups on the coated fiber. Additionally, the typical absorption band at 2930 cm-1 stands for the stretching vibration for C-H. The strong peak in the region of 1031 cm-1 to 1124 cm-1 is due to the Si-O stretching vibration of

FIGURE 6. 1H NMR spectra of (a) [1-(2-aminoethyl)-3-aminopropyl]trimethoxysilane and (b) AEAPS (solvent: ethanol-d6). the Si-O-Si bond. These FTIR results not only confirm that PMPS has been coated on the glass fiber substrate successfully but also prove that thiol groups on PMPS remain intact after curing. Figure 4 shows the SEM images of the original Crane230 fiber and the PMPS-10% fiber. It can be concluded by comparing these two images that, although some bridging exists, most of the PMPS polymer is coated on the surface of the fibers rather than occurring randomly within the void volume between the fibers. The remaining void volume facilitates diffusion and access of metal ions to thiol groups on the surface of the fibers. Thermogravimetric analysis (TGA) revealed that both PMPS-10% and PMPS-20% fibers are thermally stable up to 250°C. Additionally, the PMPS polymer coating on the surface of the fibers is hydrolytically stable. Weight loss of the coated fiber after refluxing in water for 2 days was less than 2%. Synthesis and Characterization of Cu-FC-PAEAPS Fibers. Based on previous studies by Fryxell and co-workers (19), it is known that copper ferrocyanide groups are highly selective for cesium ion. In this work, we synthesized a polyorganosilsesquioxane containing copper ferrocyanide groups on a glass fiber matrix. [1-(2-Aminoethyl)-3-amino-

propyl]silsesquioxane (AEAPS) was prepared by hydrolysis and condensation of [1-(2-aminoethyl)-3-aminopropyl]trimethoxysilane using NaOH as a catalyst (Figure 5). The structure of AEAPS was confirmed by 1H, 13C, and 29Si NMR spectra. It is evident from the 1H NMR spectrum in Figure 6 that all hydrogen peaks assigned to the monomer broaden after hydrolysis and condensation. Furthermore, the strong sharp peak, designated as f in Figure 6a and representing methoxyl group hydrogens in the monomer, disappears after condensation and indicates that hydrolysis of the Si-OCH3 groups is complete. GPC measurement revealed that the assynthesized AEAPS has a Mn of 1540 and polydispersity of 3.5. The immobilization of copper ferrocyanide into PAEAPS fibers was carried out following procedures described elsewhere (19). Figure 7, after Fryxell et al. (19), illustrates the synthetic procedures. Figure 8 shows the FTIR spectra of (a) the original Crane-230 fiber, (b) PAEAPS-10% fiber, and (c) Cu-FC-PAEAPS-10% fiber. Several absorption bands evident in Figure 8a,b and representing vibrations of NH and NH2 groups at 3600 cm-1 to 3100 cm-1, 1665 cm-1 and 928 cm-1, and the stretching vibration of Si-O-Si bonds at 1030-1127 cm-1 appear after the PAEAPS polymer is coated on the fiber substrate. Moreover, a new strong absorption peak appears at 2095 cm-1 in Figure 8c. This intense peak is characteristic of numerous cyanide groups and confirms successful immobilization of copper ferrocyanide on the surface of the fibers. SEM images of the original Crane-230 fiber and of the PAEAPS-10% fiber are illustrated in Figure 9. By comparing these two images, it is evident that most of the PAEAPS polymer is coated on the surface of the fibers rather than lodging in the void volume between the fibers. As with PMPScoated fibers, the void volume facilitates diffusion and access of metal ions to chelating sites on the surface of the fibers. TGA results indicate that the PAEAPS fibers are also thermally stable up to 250 °C. In addition, the weight loss of less than 5% for the PAEAPS coated fibers after refluxing in water for 2 days indicates that the PAEAPS polymer coating on the fibers is hydrolytically stable. Equilibrium Adsorption Experiments for Mercury. The ability of PMPS fibers to adsorb mercury from contaminated solutions under a wide range of conditions was investigated. Table 1 summarizes ion concentrations of several different contaminated solutions before and after treatment with PMPS-10% and PMPS-20% fibers. It can be seen from Table 1 that a single treatment with either PMPS-10% or PMPS20% fiber reduces the mercury concentration in solution to well below the U.S. Environmental Protection Agency’s regulatory limit for this contaminant in hazardous waste and even below the drinking water standard. Likewise, silver concentrations were reduced to sub-ppb levels. Lead also was reduced to below its respective regulatory limit for a hazardous waste. The equilibrium adsorption experiments for mercury shown in Table 1 were performed in the presence of a large excess of background ions, such as sodium, barium, and zinc. The adsorption tests show that sodium, barium, and zinc do not chelate to PMPS and that PMPS materials remain effective for Hg adsorption in the presence of high concentration of such ions. The selectivity of the PMPS coated fiber for mercury can be inferred from its distribution coefficient (Kd) for mercury (Table 1). Kd is a measure of the affinity of an ion exchanger for a particular ion and an indicator of the selectivity of the ion exchanger to the particular ion in the presence of a complex matrix of interfering ions (19). As indicated from the results in Table 1, the mercury distribution coefficients for all the equilibrium adsorption experiments are in excess of 299 900 mL/g, and some of them are even significantly in excess of 1 500 000 mL/g. VOL. 37, NO. 18, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 7. Synthesis of Cu-FC-PAEAPS fibers.

FIGURE 8. FTIR spectra of (a) original Crane-230 glass fiber substrate, (b) PAEAPS-10% fiber, and (c) Cu-FC-PAEAPS-10% fiber. Figure 10 shows the sorption kinetics of PMPS-10% fiber material with mercury in the presence of a high concentration of sodium. It can be seen from the figure that PMPS-10% fibers can reduce a 3.0 ppm mercury solution to less than 0.06 ppm within 30 min and to less than 5 ppb within 2 h, at a solution-to-solid ratio of 200 mL/g. In addition to two low initial mercury concentrations (3 and 6 ppm) tested, an initial high concentration of mercury (109 ppm) in water in the presence of high concentration of 4266

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sodium (2170 ppm) was tested by the PMPS-10% fibers. It was observed that the PMPS-10% fibers could selectively reduce the mercury concentration to 43 ppm with negligible adsorption of sodium. A mercury loading capacity of 0.16 mmol per gram of PMPS-10% fibers (equivalent to 32 mg/g) has been observed. Equilibrium Adsorption Experiments for Cesium. The ability of Cu-FC-PAEAPS fibers to remove cesium from contaminated solutions also was measured under a wide range of conditions. Table 2 shows the ion concentrations of several different contrived solutions before and after treatment with Cu-FC-PAEAPS-10% and Cu-FC-PAEAPS-20% fiber materials. The equilibrium results from Table 2 show that a single treatment with either Cu-FC-PAEAPS-10% or Cu-FC-PAEAPS-20% fiber material reduces a 2 ppm cesium solution to below 4 ppb (nearly 100% removed), even at high concentrations of sodium or potassium from both neutral and acidic solutions. The equilibrium adsorption experiments in Table 2 show that sodium and potassium are not sorbed by Cu-FC-PAEAPS fibers, and the chelating materials remain effective in the presence of high concentrations of such ions. The selectivity of the Cu-FC-PAEAPS fibers for cesium is apparent from its distribution coefficient (Kd) for this element. Results for Kd from 56 000 mL/g to 203 000 mL/g are reported in Table 2. Figure 11 shows the sorption kinetics of Cu-FC-PAEAPS10% fiber material with cesium in the presence of high concentrations of sodium. The figure illustrates that Cu-FCPAEAPS-10% fibers can reduce a 2.0 ppm cesium solution to less than 7 ppb within 5 min and to less than 4 ppb within 2 h at a solution-to-solid ratio of 200 mL/g. While sorption kinetics of the Cu-FC-PAEAPS fiber material for cesium are remarkably fast, it is a little bit slower than that of MCM-41

FIGURE 10. Changes of mercury concentrations as a function of time in the sorption reaction of PMPS-10%. Initial Hg concentration: 3.0 ppm in 0.1 M NaNO3, 10 mL of solution, and 0.05 g of PMPS-10%.

TABLE 2. Analyzed Concentrations of Cesium in Aqueous Solutions before and after Treatment with Cu-FC-PAEAPS-10% and Cu-FC-PAEAPS-20% Fiber Materialsa Cs concentration (ppb) (Kd of Cs, mL/g)

FIGURE 9. SEM images of (a) original Crane-230 glass fiber substrate and (b) PAEAPS-10% fiber.

solution

before treatment

after treatment after treatment with Cu-FCwith Cu-FCPAEAPS-10% PAEAPS-20%

0.01 M NaNO3 1 M NaNO3 3 M NaNO3 M NaNO3 + 0.1 M HNO3 1 MKNO3

1900 2210 2040 2030 2320

2.0 (94 900) 1.0 (189 900) 2.2 (100 354) 1.2 (184 067) 3.6 (56 566) 1.2 (169 067) 1.0 (202 900) 1.5 (154 566)

a

Ten milliliters of solution, 0.1 g of Cu-FC-PAEAPS.

TABLE 1. Analyzed Concentrations of Metal Contaminants in Aqueous Solutions before and after Treatment with PMPS-10% and PMPS-20% Fiber Materialsa Hg concentration (ppm) solution

Hg

Ag

Cr

Pb

Ba

Zn

Na

Kd of Hg (mL/g)

Initial Solution 1 2

3.0 6.1

1′ 2′

0.0010 0.0011

1′′ 2′′

0.0009 0.00016