JP2017536980A - Preparation of chitosan-based microporous composite and its application - Google Patents

Abstract

Microporous glutaraldehyde cross-linked chitosan adsorbent, method of making and using it, and generator of radioisotope 99Mo containing adsorbent.

Description

1. FIELD Disclosed herein is a method for modifying chitosan that increases its versatility as an adsorbent, particularly as a radioisotope adsorbent, and further increases the ability of these materials to function in environments where radioactivity is present. . Also disclosed is the material itself and to separate and purify radioactive isotopes and to separate and purify contaminated materials in radioactive and non-radioactive streams contaminated by metal ions, particularly heavy metal ions. A method of using them for the purpose is also disclosed.

2. 2. Description of Related Art Radioactive isotopes are widely used for therapeutic and imaging applications, particularly in the field of nuclear medicine. However, these materials can present production, storage, and disposal problems due to their radioactivity and often due to their significant half-life.

More specifically, in the area of radiopharmaceuticals, ^99m Tc (having a half-life t _{1/2 of} about 6 hours) is obtained from the decay product of the parent ⁹⁹ Mo (t _1/2 is about 66 hours) and is a diagnostic medicine. Is one of the most widely used radioisotopes. ^99m Tc is a pure gamma emitter (0.143 MeV) ideal for use in pharmaceutical applications due to its short half-life (6 hours). It is used in 80-85% of the approximately 25 million nuclear medicine diagnostic techniques performed annually.

Although the parent ⁹⁹ Mo can be generated by irradiating ⁹⁸ Mo with thermal / external neutrons in a nuclear reactor, much of the world's supply of ⁹⁹ Mo is responsible for fission of highly enriched uranium (HEU) in the reactor. Derived from. The HEU process generates large amounts of radioactive waste and reprocessing of unused uranium targets is not permitted due to weapons spreading concerns.

Low enriched uranium (LEU, 20% or less ²³⁵ U) can be used as an alternative, but the presence of large amounts of unusable ²³⁸ U results in a large amount of waste. Currently, most of the world's ⁹⁹ Mo supply comes from sources outside the United States. The recent cessation of ⁹⁹ Mo production at these sources has disrupted medical care and proved that this supply chain is unreliable. This emphasizes the need for an economically viable alternative source to produce ^99m Tc from ⁹⁹ Mo.

The main concern of the ^{99 Mo} produced by neutron capture, as compared to the material produced by the more general fission above is that it requires both a lower specific activity and lower radioactivity level. Specific activity is significantly lower and is of great concern due to its impact on the scale, efficiency, and functionality of the ⁹⁹ Mo / ^99m Tc generator. Thus, the use of molybdates with lower specific activity is only possible with a more efficient adsorbent to reduce the generator scale and produce a dose that can be used in radiopharmaceuticals. Some research has focused on the use of molybdenum gel generators. Marageh, M.M. G. Et al., “Industrial-scale production of ^99m Tc generators for clinical use based on zirconium molecular gel,” Nuclear Technology, 269-284, 209-284G Et ^{al., "99 Mo / 99m Tc generators} performances prepared from zirconium molybdate gels" J. Braz. Chem. Soc. 19, 3, 380-388 (2008). Other studies have focused on the preparation of ⁹⁹ Mo / ^99m Tc generators based on polymers or inorganic oxides as ⁹⁹ Mo adsorbent materials. Masakazu, T .; ^Et al., “A ^99m Tc generator using a new organic polymer absorbent for (n, γ) ⁹⁹ Mo,” Appl. Radi. Isot. , 48, 5, 607-711 (1997); M.M. Et al., "Preparation and evaluation of hydrous titanium oxide as a high affinity adsorbent for molybdenum (99 Mo) and its potential for use in 99m Tc generator," Radiochim. Acta, 99, 231-235 (2011).

However, such medical use requires that ^99m Tc be produced in a highly pure form. For example, if ^99m Tc is produced by the decay of ⁹⁹ Mo, it is important to achieve a high degree of separation of the two elements to meet regulatory requirements.

One approach to achieving this level of purity, using the highly efficient selective adsorbent by eluting the ^99m Tc, for example, ⁹⁹ Mo is ^adsorbed, separating the ^99m Tc from 99 Mo It is. Attempts have been made to use alumina as such an adsorbent. However, the efficiency resulting from this alumina is about 25 mg Mo ⁹⁹ per gram of adsorbent. Therefore, there remains a need in the art for adsorbents that are efficient with respect to ⁹⁹ Mo adsorption and that are resistant to the harmful effects of ionizing radiation. Furthermore, there is a need for an adsorbent that is very selective for ⁹⁹ Mo, ie, capable of adsorbing ⁹⁹ Mo while providing good release of ^99m Tc.

  More generally, one or more materials that are readily available or can be produced from readily available materials and from which the material can remove components from a process stream that requires such purification. There is a need for an adsorbent that can be customized by modifying it to have multiple functional groups (which can be the same or different) and that is resistant to degradation by ionizing radiation.

  Ion exchange processes that have been used for decades to separate metal ions from aqueous solutions are often compared to adsorption. The main difference between these two processes is the stoichiometric process where ion exchange requires electrostatic forces in the solid phase matrix, whereas in adsorbent separation, solute uptake on the solid surface It is a point that requires both electrostatic force and van der Waals force. Several researchers have tried a number of inorganic, organic, and biosorbents, trying to find suitable ion exchange resins for removing cesium and strontium from the effluent, but their success has varied. Gu, D .; Nguyen, L .; Philip, C .; V. Huckmen, M .; E. , And Anthony, R .; G. “Cs ion exchange kinetics in complex electorative solutions using hydrous crystalline crystalline siliconates”, Ind. Eng. Chem. Res. 36, 5377-5383, 1997; S. Mohapatra, P .; K. , And Manchanda, V. K. “Extraction of actinides fission products from salt salts solutions using polyethylene glycols (PEGs)”, Journal of Radiological, 27, 63, 24. F. Simon, N .; Lamare, V .; "A solution for cereal removal high salinity acidic or alkalin liquid waste: The Crown calix [4] arenas" Sep. Sci. Technol. , 34 (6 & 7), 877-909, 1999; Arena, G .; , Contino, A .; , Margi, A .; “Stratesies based on calixcrows for the detection and removal of cerealions from alkali-containing solutions”, Ind. Eng. Chem. Res. 39, 3605-3610, 2000.

  However, the main disadvantage of the ion exchange process is the cost of the material when treating the radioactive stream and the regeneration for repeated use. Hassan, N .; Adu-Wsu, K .; , And Marra, J. et al. C. See "Resorcinol-formal deduction of ceaseum (Cs +) from Hanford waste solutions-Part I: Batch equilibrium study" WSRC-MS-2004. Disposal costs are also a major problem. The success of the adsorption process is largely dependent on the cost and capacity of the adsorbent and the ease of regeneration.

  Chitosan is a partially acetylated glucosamine polymer found in fungal cell walls. Chitosan is obtained by deacetylation of naturally abundantly available chitin, which is the main component of shellfish shells. This biopolymer is very effective in the adsorption of metal ions due to its complexing ability due to its very high content of amino and hydroxyl functional groups. In its natural form, chitosan is soft and has a tendency to agglomerate or form a gel in acidic media. Moreover, chitosan is non-porous in its natural form and the specific binding site of this biopolymer is not readily available for adsorption. However, it is necessary to provide physical support and chemical modifications to increase the accessibility of metal binding sites for process applications. It is also essential that the metal binding functionality should be retained after any such modification.

  It is well known that polysaccharides can be degraded by breaking glycosidic bonds with ionizing radiation. IAEA-TECDOC-1422, “Radiation processing of polysaccharides”, International Atomic Energy Agency, November, 2004. Hydrogels based on polysaccharides and their derivatives have been extensively studied, but very few studies have so far reported on the effects of radiation on chitosan-based microporous composites and their metal ion uptake capacity Yes.

  Chitosan is a non-toxic and biodegradable material. Chitosan has been studied for many new applications because of its availability, polycation properties, membrane effects, and the like. The amino group present in the structure of chitosan is an active metal binding site, but this amino group makes chitosan soluble in weak acids. In acidic media, chitosan tends to form a gel, which is not suitable for metal ion adsorption in a continuous process.

  Several reports have shown that when chitosan is cross-linked with glutaraldehyde, it becomes acid or alkali resistant. Elwakel, KZ. , Atia, A .; A. , And Donia, A .; M.M. “Removal of Mo (VI) as oxanions from aquaous solutions using chemical modified chitsan resins”, Hydrometallurgy, 97, 21-28, 200C; Vincent, T .; , And Guitar, E .; “Metal anion on chitosan and deliberate materials: a strategy for polymer modification and optimum use”, Reactive and Functional Polymers, Nur. , Kumar. G. G. Han, S .; S. Nahm, K .; S. , And Lee, Y .; S. See “Synthesis and characterization of potential fungalidal silver nano-sized parsicles and chitosan membrane contanning silver part 3”. Glutaraldehyde is a five-carbon molecule that ends with an aldehyde group at both ends and is soluble in water and alcohol, and organic solvents. This reacts rapidly with the amine group of chitosan during cross-linking through a Schiff reaction, resulting in a thermally and chemically stable cross-link. Migneault, I.M. , Dartugenave, C, Bertrand, M .; J. et al. , And Waldron, K .; C. See “Gluraldehyde: behavior in aquatic solutions, reaction with proteins, and application to enzyme crosslinking” Bio Technologies, 37 (5), 790-802, 2004. The amine group is also believed to be an active metal binding site for chitosan. Thus, it has been reported that cross-linking with glutaraldehyde makes chitosan resistant to acids or alkalis, but reduces the ability to adsorb metals.

  Li and Bai (2005) is a method of capping the amine group of chitosan by performing formaldehyde treatment before crosslinking with glutaraldehyde, and the formaldehyde is sufficiently treated with 0.5 M HCl solution after the treatment. A method was proposed to remove from the chitosan structure by washing. Li, Nan, and Bai, R.A. “A novel amine-shielded surface cross-linking of chitosan hydrobeads for enhanced metal advertisement performance” Ind. Eng. Chcm. Res. , 44, 6692-6700, 2005.

  The cross-linking of various functional groups with chitosan is thought to depend mainly on cross-linking reaction conditions such as pH, temperature, ionic concentration, and surface charge of the material.

  Singh et al. (2006) showed that the swelling properties of formaldehyde-crosslinked chitosan hydrogels depend on the reaction behavior of pH, temperature, and ionic strength. Singh, A .; , Narvi, S .; S. , Duta, Ρ. Κ. , And Pandey, N .; D. “External stimuli response on a novel chitosan hydrogel crossed with formaldehyde” Bull. Mater. Sci. 29 (3), 233-238, 2006.

The surface charge of chitosan, which determines the type of bond that forms between the crosslinker and chitosan, depends on the pH of the solution. Hasan, S .; , Krishniah, A .; , Ghosh, T .; K. Viswanath, D .; S. Boddu, V .; M.M. , And Smith, E .; D. “Adsorption of divergent cadmium from aquaous solutions on chitosan-coated perlite beads”, Ind. Eng. Chem. Res. 45, 5066-5077, 2006. The value of the zero charge point (PZC) of pure chitosan is in the range of pH 6.2 to 6.8. Hasan, S .; Ghosh, T, K .; Viswanath, D .; S. Loyalka, S .; K. , And Sengupta, B .; See “Preparation and evaluation of fullers earth for removal of cereal from waste streams” Separation Science and Technology, 42 (4), 717-738, 2007. Chitosan is not soluble at alkaline pH, but is soluble at acidic pH, and amine groups present in chitosan can undergo protonation to become NH ₃ ⁺ or (NH ₂ —H ₃ O) ⁺ .

Li et al. (2007) reported cross-linked chitosan / polyvinyl alcohol (PVA) beads with high mechanical strength. They observed that H ⁺ ions in solution can also act as protection of the amino group of chitosan during the crosslinking reaction. Li, M.M. , Cheng, S .; , And Yan, H .; "Preparation of crosslinked chisan / poly (vinyl alcohol) blend beads with high mechanical strength", Green Chemistry, 9, 894-898, 2007.

  Farris et al. (2010) studied the reaction mechanism of cross-linking of glutaraldehyde and gelatin. Farris, S .; Song, J .; , And Huang, Q .; “Alternative reaction mechanism for the cross-linking of gelatin with glutadehyde” J. et al. Agric. Food Chem. 58, 998-1003, 2010. They show that at higher pH values, the crosslinking reaction is dominated by the Schiff base reaction, but at lower pH, the reaction requires the —OH group of hydroxyproline and hydroxylysine, which results in the formation of hemiacetal. Suggested to get.

  Hardy et al. (1969) proposed that at acidic pH, glutaraldehyde is in equilibrium between its cyclic hemiacetal and the polymer of cyclic hemiacetal, and as temperature increases, it produces free aldehydes in acidic solution. . Hardy, P.M. M.M. Nicholas, A .; C. , And Rydon, H .; N. “The nature of glutardehyde in aqueous solution” Journal of the Chemical Society (D), 565-566, 1969.

  Some studies have focused on chitosan-based cross-linked materials for medical use and use as radiopharmaceuticals and have had some success. For example, Hoffman, B .; Seitz, D .; , Mencke, A .; Kokkot, A .; , And Ziegler, G .; “Glutaraldehyde and oxidized extentant as crosslinker reagents for chitosan-based scaffolds for cartridge tissue engineering” J. Mater Sci: Mater Med, 20 (7). 1495-1503, 2009; Safmawi, K .; M.M. “Gamma radiation-induced crosslinked PVA / Chitosan blends for wound dressing” Journal of Macromolecular Science, Part A: Pure and Applied Chem 44, 54. G. , And Park. H. J. et al. “Study of gamma-irradiation effects on chitosan microparticulates” Drug Delivery, 13, 39-50, 2006; Silva, R .; M.M. , Silva, G .; A. Coutinho, O .; P. Mano, J .; F. , And Reis, R .; L. “Preparation and charac- terization in simulated body conditions of globaldehydrated crosslinked chitosan membranes”, Journal of Material Science: 110-Journal of Material Science: 110.

However, Sabharwal et al. (2004) reported that the processing of natural polymers with radiation received less attention because natural polymers undergo chain scission reactions when exposed to high energy radiation. Sabharwal, S .; , Varshney, L .; , Chaudhary, A .; D. , And Ramnani, S .; P. “Radiation processing of natural polymers: Achievations & Trends” In Radiation processing of polymerases, 29-37, IAEA, November, 2004. Chitosan radiation has been reported to result in lower viscosities and chitosan chain scission. Kume, T .; , And Takehisa, M .; “Effect of gamma-irradiation on sodium alloy and carriageen powder” Agric. Biol. Chem. 47, 889-890, 1982; Ulanski, P .; , And Roseak, J .; M.M. “Preliminary studies on radiation induced changes in chitosan” Radiat. Phys. Chem. 39 (1), 53-57, 1992. H ⁺ and OH ⁻ radicals formed by radiolysis upon water irradiation accelerate the molecular chain scission of chitosan. The reaction between the free radicals and the chitosan molecules causes rapid degradation of chitosan in aqueous solution. See IAEA-TECDOC-1422, “Radiation processing of polysaccharides” International Atomic Energy Agency, November, 2004. These studies suggest that the use of chitosan in environments exposed to radiation and potential radiolysis is problematic.

Nevertheless, the current demand for biocompatible polymer materials in radiopharmaceutical and radioactive waste treatment has developed an economically viable alternative source of acid, alkali, and radiation resistant polymer network structures There is growing interest in doing. The recent development of chitosan-based materials in the medical, radiopharmaceutical, and radioactive waste areas has attracted attention due to their availability and biocompatibility. Alves, N.M. M.M. , And Mano, J .; F. “Chitosan derivatives by by chemical modification for biomedical and environmental applications,” International Journal of Biologic. 200, Bio43. , Reist, M .; , Mayer, J .; M.M. Felt, O .; , Peppas, N .; A. , And Gurny, R, "Structure and interactions in covariantly and ionic crossed chitosan hydrogels for bioapplications", Europe. It has been reported that chemical changes in chitosan occur upon irradiation and that the extent of the reaction induced by radiation depends on the polymer network structure. Zainol, I. et al. Aquil, H .; M.M. , And Mastor, A .; “Effect of γ-ray irradiation on the physical and mechanical properties of chitosan powder” Material Science and Engineering C, 29, 292-297, 2009; P. , Cheng, C.I. H. , Chiang, Y .; C. Lee, S .; C. "Irradiation of synthetic nanomaterials and it's application for hypermia" Advanced Materials Research, 47-50, 1298-1301, 2008; H. Botelho, M .; L. , Lcal, J. et al. P. , And Gil, M .; H. “Study on chemical, UV and gamma radiation-induced grafting of 2-hydroxyethyl hydrated onto chitosan” Radiation Physics and Chemistry, 72, 731-73, 73-73; 903, June 9, 1998; Wenwei, Z, Xiaogang, Z .; Li, Yu, Yuefang, Z .; , And Jiazhen, S .; “Some chemical changes in chitosan induced by γ-ray irradiation”, Polymer Degradation and Stability, 41, 83-84, 1993; Y. , Khor, E .; , And Koo, O .; “Γ irradiation of chitosan”, Journal of Biomedical Material Research, 43 (3), 282-290, 1998; Akashi, M .; , Miyata, M .; , And Chirachanchai, S. “Optical γ-ray dose and irradiation conditions for producing low molecular weight chitsan that retains chemical structure, Y4-4, ResearchRe4. H. , Wei, G .; S. , And Peng, J .; See “Radiation degradation of chitsan in the presence of H ₂ O ₂ ” Chinese Journal of Polymer Science, 22 (5), 439-444, 2004. However, the information available on the effect of radiation on the crosslinked chitosan composite matrix is very limited.

  One embodiment disclosed herein relates to a radiation resistant adsorbent comprising glutaraldehyde cross-linked chitosan.

  More specifically, disclosed herein are chitosan-based microporous composite micron-sized particles and chitosan-titania microporous composites prepared by cross-linking chitosan with glutaraldehyde in the presence of a catalyst.

  Even more particularly, herein, chitosan cross-linked with glutaraldehyde in the presence of a catalyst such as an acid (eg, HCl) at a glutaraldehyde concentration of about 2-4 wt. An adsorbent containing a microporous material of chitosan that is resistant to degradation by exposure to and to degradation by exposure to acid or alkaline solutions is disclosed.

  Without wishing to be bound by theory, it is believed that the crosslinked microporous chitosan matrix enhances the acid resistance and mechanical strength of the chitosan particles. As a result, the metal ion uptake capacity of the crosslinked particles from acidic or alkaline radioactive solutions is increased compared to commercial resins and commercial aluminas. With this increased uptake, high efficiencies of 500-700 mg per gram of adsorbent and more specifically about 600 mg per gram of adsorbent can be obtained for molybdenum.

  Described herein are embodiments of chitosan-based microporous composite materials prepared using solution casting and a combination of solution casting and sol-gel methods.

  In one embodiment, chitosan cross-linked with glutaraldehyde in the presence of acid as a catalyst at a temperature around 70 ° C. with continuous stirring. Without wishing to be bound by theory, it is believed that the amino group present in the chitosan structure is protonated and thus protected from reaction with glutaraldehyde. Further, at a temperature around 70 ° C., it is considered that more aldehyde groups than can be used at room temperature can be used for the reaction. In this case, without wishing to be bound by theory, glutaraldehyde undergoes aldol condensation, and the free aldehyde group reacts with the —OH group of chitosan in the presence of an acid catalyst, so that polymerization of chitosan and glutaraldehyde occurs. Is considered to be a condensation polymerization. The reaction time is generally in the range of about 4 hours to about 8 hours. In one embodiment, the molar ratio of chitosan hydroxyl groups to glutaraldehyde is desirably maintained around 4/1.

  In certain embodiments, the crosslinked material can be further processed by washing to remove excess glutaraldehyde, drying, wet or dry milling, and further chemical processing. One example of this further chemical treatment that has been found to be particularly suitable is at least partial oxidation with an oxidizing agent. In particular, permanganate (eg, with a potassium permanganate solution containing at least about 14 mg Mn per liter of solution), peroxide, chlorite, hypochlorite, dichromate, or metal Oxidation with one or more of oxides, or other acid-base amphoteric oxidants, to increase the selectivity of the adsorbent for Mo (VI) compared to Tc (VII) as well as packed adsorption Particularly suitable for efficient and rapid elution and recovery of technetium from the agent. More specifically, an oxidizing agent comprising one or more of alkali metal chlorites, alkali metal hypochlorites, alkali metal dichromates, or transition metal oxides is desirably used. More specifically, an oxidant comprising one or more of sodium chlorite, sodium hypochlorite, potassium dichromate, or cerium oxide is desirably used. In addition to oxidizing the cross-linked adsorbent material, these oxidants can desirably be included in the elution solution used to release technetium from the adsorbent. Desirably, such an oxidizing agent is included in the saline-containing elution solution at a concentration ranging from about 5 to about 40 mM with respect to chlorite or hypochlorite.

Desirably, the adsorbent has a surface area in the range of about 10 to about 100 m < ² > / g, more specifically about 25 m < ² > / g. Also desirably, the adsorbent has a zero charge point in the range of about 7.5 to about 8.8, more specifically about 8.8.

  The adsorbent embodiments described herein have excellent retention capacity for molybdenum and are capable of adsorbing near or higher amounts of molybdenum based on the dry weight of the adsorbent. it can. This retention capacity can be around 6.25 mmol or more than 6.25 mmol per gram of adsorbent. The adsorbent also has excellent selectivity for molybdenum compared to technetium and can retain molybdenum with an efficiency of at least about 80% while passing pertechnetate in saline solution. The adsorbent embodiments disclosed herein also have an excellent capacity for adsorbing heavy metals, including, for example, the ability to adsorb Hg in amounts of 2.96 mmol per gram dry adsorbent or greater than 2.96 mmol from an aqueous pH 6 solution. Also provide.

In another embodiment, titanium oxide was incorporated into a chitosan glutaraldehyde complex polymer matrix. The development of crystalline silica titanate (CST) and titanium-based oxide materials has opened the way to studies of metal ions adsorbed on hydrous titanium oxide from radioactive and non-radioactive waste streams. Anthony, R.A. G. Dosch, R .; G. Gu, D .; , And Philip, C.I. V. “Use of silicotitanates for removing cesium and strontium from defense waste” Ind. Eng. Chem. Res. 33, 2702-2705, 1994; Maria, P .; , Meng, X .; , Korfiatis, G .; P. , And Jing, C.I. “Adsorption mechanism of arsenic on nanocrystallin titanium dioxide” Environ. Sci. Technol, 40, 1277-1262, 2006; Meng et al., “Methods of preparing a surface-activated titanium oxide product and of using same in the United States, 3rd year, United States No. 3, 7th year, United States, No. 3, 1995 Please refer to the day. Qazi and Ahmed (2011) reported hydrous titanium oxide as an adsorbent of ⁹⁹ Mo and its potential for use in a ^99m Tc generator. Qazi, Q .; M.M. , And Ahmed, M .; “Preparation and evaluation of hydrous titanium oxide as a high affinity adsorbent for moltibdenum ( ⁹⁹ Mo) and its potential for use in ^99m tent. 2011, 18172011. Titanium oxide has been suggested to be able to form surface complexes with metal ions due to the bidentate mode of binding to surface oxygen atoms. Hasan, S .; , Ghosh, T .; K. Prelas, M .; A. Viswanath, D .; S. , And Boddu, V, M .; “Adsorption of uranium on a novel biosorbent chitosan coated perlite”, Nuclear Technology, 159, 59-71, 2007.

However, none of these documents disclose that TiO ₂ dispersed in a chitosan matrix enhances the overall metal ion uptake capacity from radioactive waste liquors. In the method disclosed herein, hydrous titanium oxide gel was prepared using sol-gel technology. The titanium oxide gel was incorporated into a chitosan and glutaraldehyde matrix in the presence of HCl as a catalyst.

Thus, one embodiment is a method of preparing a radiation resistant adsorbent comprising:
Mixing chitosan and water in the presence of acid to form a chitosan gel;
Adding glutaraldehyde to the chitosan gel to form a semi-solid mass at 70 ° C. in the presence of a catalyst;
Removing unreacted glutaraldehyde by washing the semi-solid mass to form a washed mass;
Suspending the washed mass in an aqueous base to form a neutralized crosslinked mass; and drying the neutralized crosslinked mass to form a radiation resistant adsorbent;
Relates to a method comprising:

Another embodiment is:
Forming an amorphous titania gel by acid-catalyzed hydrolysis and condensation of titanium isopropoxide;
Mixing the amorphous titania gel with the chitosan gel under conditions that allow the gel to fully react before adding the glutaraldehyde,
Further comprising a method.

In one embodiment, a chitosan-based microporous composite was suspended in a pH 3 solution and irradiated at 50,000 krad using a ⁶⁰ Co irradiation apparatus. The specific objectives of this study are: 1) preparing chitosan-based microporous composite particles to adsorb metal ions from highly acidic or alkaline radioactive effluents; and 2) optimizing the crosslinking process; It was to obtain the largest metal binding site.

Thus, another embodiment is a method for separating an isotope from a mixture thereof:
Contacting the radiation-resistant adsorbent of claim 1 preferentially adsorbing at least one of the isotopes with a mixture of at least two isotopes;
Adsorbing at least one of the isotopes on or in the adsorbent with one or more of the remaining isotopes not significantly adsorbed by the adsorbent;
Removing the one or more remaining isotopes from the adsorbent;
Relates to a method comprising:

Chitosan cross-linked composites are excellent low cost alternative adsorbent materials compared to available resins and are therefore desirable adsorbent materials for removing metal ions from radioactive and non-radioactive aqueous solutions. It has been found that the success of the adsorption process in a ⁹⁹ Mo / ^99m Tc generator system is highly dependent on the cost and capacity of the adsorbent and the ease of ^99m Tc release from the generator. The main problem with this particular method from a radiation safety standpoint is that the parent ⁹⁹ Mo, which must be maintained in accordance with US Nuclear Regulatory Commission (NRC) standards, “leaks” or partially elutes from the generator at ^99m Tc. It is a point that involves. The material and method embodiments described herein provide good and selective release of ^99m Tc from the generator, thereby solving this problem and meeting the requirements of such a generator. .

  Further, embodiments of the chitosan cross-linked composite disclosed herein include contacting the chitosan cross-linked composite with a liquid stream containing one or more heavy metals and one or more of the heavy metals thereon. Can be used in a method for separating and / or concentrating one or more heavy metals from a liquid stream, such as a waste stream or treated water stream.

  Various aspects of the embodiments disclosed herein may be more clearly understood with reference to the drawings, which should not be construed as limiting the invention as claimed.

2 is a scanning electron micrograph showing embodiments of chitosan and modified chitosan (MPCM) disclosed herein. FIG. 1a shows unmodified chitosan; FIG. 1b shows one embodiment of MPCM material. 2 is a graph showing the results of thermogravimetric analysis (TGA) of one embodiment of chitosan and MPCM. 2 is a graph showing an X-ray diffraction pattern of one embodiment of chitosan and MPCM material. 2 is a graph illustrating Fourier transform infrared (FTIR) spectra of one embodiment of chitosan and an MPCM material disclosed herein. 2 is a graph showing an X-ray photoelectron spectroscopy (XPS) survey scan of one embodiment of chitosan and MPCM. 2 is a graph showing an X-ray photoelectron spectroscopy (XPS) spectrum of one embodiment of chitosan and MPCM. Figures 6a, 6b, and 6c show the C1s, O1s, and N1s positions, respectively. 2 is a graph showing an X-ray photoelectron spectroscopy (XPS) spectrum of one embodiment of chitosan and MPCM. Figures 6a, 6b, and 6c show the C1s, O1s, and N1s positions, respectively. 2 is a graph showing an X-ray photoelectron spectroscopy (XPS) spectrum of one embodiment of chitosan and MPCM. Figures 6a, 6b, and 6c show the C1s, O1s, and N1s positions, respectively. 2 is a graph of an energy dispersive X-ray spectroscopy (EDS) micro-analysis spectrum of one embodiment of the MPCM described herein. FIG. 7a shows the spectrum of one embodiment of chitosan and MPCM before and after irradiation. FIG. 7b shows a comparison of one embodiment of chitosan and MPCM. FIG. 7c shows a comparison of one embodiment of MPCM before and after irradiation. 2 is a graph of an energy dispersive X-ray spectroscopy (EDS) micro-analysis spectrum of one embodiment of the MPCM described herein. FIG. 7a shows the spectrum of one embodiment of chitosan and MPCM before and after irradiation. FIG. 7b shows a comparison of one embodiment of chitosan and MPCM. FIG. 7c shows a comparison of one embodiment of MPCM before and after irradiation. 2 is a graph of an energy dispersive X-ray spectroscopy (EDS) micro-analysis spectrum of one embodiment of the MPCM described herein. FIG. 7a shows the spectrum of one embodiment of chitosan and MPCM before and after irradiation. FIG. 7b shows a comparison of one embodiment of chitosan and MPCM. FIG. 7c shows a comparison of one embodiment of MPCM before and after irradiation. FIG. 2 is a schematic diagram showing a reaction pathway for preparing one embodiment of MPCM described herein. 2 is a graph showing FTIR spectra before and after irradiation of one embodiment of a modified chitosan disclosed herein. 2 is a graph showing X-ray photoelectron spectroscopy (XPS) spectra before and after irradiation of one embodiment of MPCM. Figures 10a, 10b and 10c show the C1s, O1s and N1s positions, respectively. 2 is a graph showing X-ray photoelectron spectroscopy (XPS) spectra before and after irradiation of one embodiment of MPCM. Figures 10a, 10b and 10c show the C1s, O1s and N1s positions, respectively. 2 is a graph showing X-ray photoelectron spectroscopy (XPS) spectra before and after irradiation of one embodiment of MPCM. Figures 10a, 10b and 10c show the C1s, O1s and N1s positions, respectively. 2 is a graph showing the surface charge of one embodiment of MPCM exposed and unexposed to 1% Mo (VI) in solution in the presence of 1M NaNO ₃ . FIG. 6 is a graph showing the effect of pH on molybdate adsorption to one embodiment of MPCM, with initial conditions of a concentration of 5.21 mmol / L and a temperature of 298K. It is the schematic which shows the reaction mechanism of adsorption | suction of Mo (VI) from aqueous solution to one Embodiment of MPCM. FIG. 6 is a graph showing an equilibrium adsorption isotherm for the incorporation of Mo (VI) into one embodiment of MPCM, where the Mo (VI) concentration in the solution is in the range of 1 mmol / L to 94 mmol / L, and the temperature is 298K. Experimental data ( ^* ) correlated with the Langmuir isotherm model (solid line) under the condition that the pH is about 3. FIG. 15a is a graph showing a leakage curve of Mo (VI) adsorption on the MPCM bed, and the inlet concentration of the influent at the inlet was 5.21 mmol / L of Mo (VI) at pH3. FIG. 15b is a graph showing the effect of pH of the injection on the leakage curve of Mo (VI) from a column packed with one embodiment of MPCM. The influent concentration at the inlet was pH 4-7, and was 5.21 mmol / L Mo (VI) containing 153.8 mmol / L NaCl, respectively. In both figures, the column bed height was 3.2 cm and the inlet influent flow rate was 1 mL / min. FIG. 15a is a graph showing a leakage curve of Mo (VI) adsorption on the MPCM bed, and the inlet concentration of the influent at the inlet was 5.21 mmol / L of Mo (VI) at pH3. FIG. 15b is a graph showing the effect of pH of the injection on the leakage curve of Mo (VI) from a column packed with one embodiment of MPCM. The influent concentration at the inlet was pH 4-7, and was 5.21 mmol / L Mo (VI) containing 153.8 mmol / L NaCl, respectively. In both figures, the column bed height was 3.2 cm and the inlet influent flow rate was 1 mL / min. FIG. 5 is a graph showing pertechnetate leakage curves from a column packed with one embodiment of MPCM without oxidation packed with 6.25 mM Mo (VI) per gram of MPCM. The column volume was 2.5 cm ³ . The inlet flow rate was 1 mL / min. The inlet influent concentration was 0.25 mM pertechnetate per liter of saline (0.9% NaCl) solution. FIG. 6 is a graph showing the surface charge of oxidized and non-oxidized MPCM exposed to 1% Mo (VI) aqueous solution in the presence of 1N NaNO ₃ . FIG. 5 is a graph showing the elution profile of ^99m Tc from one embodiment of MPCM loaded with Mo (VI) with ⁹⁹ Mo added. FIG. 5 is a graph showing the relationship between the number of elutions from one embodiment of MPCM as an adsorbent and the percentage of ^99m Tc and Mo (VI) release. FIG. 6 is a flow chart of ⁹⁹ Mo generation using a process using a ^99m Tc / ⁹⁹ Mo generator system and neutron capture using one embodiment of MPCM as an adsorbent. Graph showing the effect of temperature on molybdenum uptake into MPCM-ClO ₂ resin under conditions of 25 mM NaOCl, pH 3.0 and solid-liquid ratio 1: 100 at a first solution concentration of 1% Mo solution and a contact time of 0.5 hour. It is. It is a graph which shows the adsorption heat of resin of FIG. 21 in various filling amount and temperature (24 to 50 degreeC). FIG. 6 is a graph showing the predicted specific activity of the proposed MPCM-based generator with a column volume of 6 mL. 2 is a graph showing FTIR spectra of chitosan and another embodiment of the modified chitosan disclosed herein.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS The methods disclosed herein and the resulting modified chitosan materials, and methods of use thereof are intended to be illustrative and are not intended to limit the invention or the appended claims. A better understanding can be obtained by reference to the following examples.

  Intermediate molecular weight chitosan (about 190,000 to about 310,000, determined by viscosity data), 75-85% deacetylated, was obtained from Sigma-Aldrich Chemical Corporation, WI, USA. All chemicals used in this example were of analytical grade.

  The modified chitosan disclosed herein can be prepared by crosslinking with glutaraldehyde under acidic conditions of the temperature conditions described below, according to the reaction schematically shown in FIG. The amount of glutaraldehyde used may vary somewhat, but it is effective to use about 2 ml to about 10 ml of glutaraldehyde per 4 g of chitosan, more specifically about 2 ml to about 8 ml, and even more specifically about 6 ml. It has been found that The pH of the cross-linking reaction between glutaraldehyde and chitosan can also vary somewhat, but the pH is about 0.7 to about 3, more specifically about 0.7 to 2, even more specifically about 1.0. Has been found to be effective. The temperature of the cross-linking reaction can also vary, but is desirably between about 50 ° C. and about 80 ° C., and more particularly around 70 ° C.

[Example 1]
The ionic capacity of chitosan used in this test was in the range of 9-19 meq / g as measured using standard titration methods. About 4 g of chitosan was added to 300 mL of DI water containing 1 mL of acetic acid and stirred at 70 ° C. for 2 hours to form a gel. Approximately 5 mL of HCl / HNO ₃ was added to the chitosan gel and maintained at 70 ° C. for an additional hour with continuous stirring to assist in the protonation of the amino substituent, which is beneficial for the reactions described below.

  The reaction with glutaraldehyde was performed by continuously stirring approximately 6 mL of a 50% concentration glutaraldehyde solution in an acidic chitosan gel at 70 ° C. (established based on trial and error, but generally 200 rpm to 500 rpm). This was done by adding dropwise. The final pH of the mixture was approximately 1.0. The amount of glutaraldehyde used in this test was established on a trial and error basis. The mixture was maintained at 70 ° C. for an additional hour with vigorous stirring (500 rpm) to give a semi-solid gel. The amino groups present in chitosan are more reactive towards aldehydes in the Schiff reaction than the hydroxyl groups of chitosan. At 70 ° C., it is envisioned that more free aldehyde groups are present in the solution than are present at room temperature. In an acidic solution, formation of a complex of an aldehyde and an amino group is inhibited by protonation of an amine group. Moreover, glutaraldehyde can undergo aldol condensation, and the reaction of the chitosan hydroxyl group with the free aldehyde can be catalyzed by an acid at 70 ° C.

  The resulting mass was then washed thoroughly with 2% monoethanolamine to remove any unreacted glutaraldehyde. The mass was then suspended in 0.1 M NaOH solution for 4-6 hours. The cross-linked mass was separated from the solution, washed with 0.1 M HCl, and then washed with deionized water (DI) until the pH of the elution solution was 7. The crosslinked mass was dried in a 70 ° C. vacuum oven overnight. The crosslinked chitosan-glutaraldehyde complex is referred to herein as “MPCM” or “microporous composite material”.

MPCM was ground using a laboratory ball mill to a particle size in the range of about 50-200 μm. An amount of these MPCM particles was suspended in an aqueous solution of pH 3 overnight. The pH of the solution was maintained using 0.1 M HNO _3. Suspended MPCM particles were irradiated using ⁶⁰ Co as a gamma ray source. MPCM sample characterization was performed using SEM, EDS X-ray microanalysis, FTIR, and XPS spectroscopy.

  To examine the surface morphology, scanning electron micrographs (SEM) of chitosan and MPCM materials were taken and are shown in FIG. A SEM secondary electron micrograph of the sample was obtained using backscattered electrons at an acceleration voltage of 10 keV. SEM micrographs of cross sections of chitosan and MPCM samples are shown in FIGS. 1a and 1b, respectively. From FIG. 1a, chitosan appears to be non-porous, and from FIG. 1b, MPCM appears to be essentially microporous.

  TGA analysis of MPCM and pure chitosan prepared in the laboratory was each performed using a TGA (TA Instruments) analyzer under a nitrogen flow atmosphere (200 mL / min). For each experiment, approximately 20 mg of MPCM was heated in a temperature range of 30-600 ° C. in an alumina crucible at a predetermined heating rate. TGA measures the amount and rate of weight change of a sample when heated at a specific rate. Thermogravimetric analysis was obtained for both MPCM and chitosan, providing supplemental information regarding compositional changes as heating progressed under controlled conditions. The heating rate in this analysis was set to 5 ° C./min. The TGA profile shown in FIG. 2 shows a two-stage degradation process for pure chitosan, but MPCM degrades gradually with increasing temperature.

  Thermogravimetric analysis (TGA) of chitosan at a heating rate of 5 ° C./min in a nitrogen atmosphere (200 mL / min) shows that complete dehydration occurs at 250 ° C. and the weight loss is 8%. Anhydrous chitosan further decomposed in the second step with a weight loss of 32% at 360 ° C. This burned out completely at 600 ° C. and the weight was further reduced by 12%. The remaining 48% is chitosan husk at 600 ° C.

  In the case of MPCM, complete dehydration occurs at 230 ° C. and the weight loss is 12%. Anhydrous MPCM burned out completely at 600 ° C. and the weight loss was 36%. The remaining 52% is MPCM husk at 600 ° C. It can be seen that the combustion products of MPCM are 4% less compared to chitosan, which indicates that MPCM contains 4% of a cross-linking agent such as glutaraldehyde, which is completely in this heating range. Indicates that it has burned out.

  The swelling behavior and acid resistance of the MPCM material were also evaluated. The swelling behavior of MPCM is described by Yazdani-Pedram et al., “Synthesis and unusual swelling behavior of combined cation / non-ionic hydrocarbons based on chitosan,” Macromol. Biosci. , 3, 577-581 (2003), was performed by immersing MPCM in deionized water and saline solution.

The swelling behavior of chitosan was also investigated with deionized water and saline solution.
The swelling ratio of chitosan and MPCM was calculated using the following formula:

Where V _s is the volume of the swollen MPCM and V _d is the volume of the dried sample. In deionized water, chitosan was observed to swell to approximately 105% of its original volume with an equilibration time of 24 hours. MPCM exhibits a very rapid swelling behavior, reaching an increase of approximately 200% within 5 minutes and reaching equilibrium in 24 hours. The swelling test with deionized water was carried out in the range of pH 3-6. The maximum volume of MPCM at equilibrium was approximately 219% greater than its dry volume.

Similar swelling behavior of MPCM was also observed for saline solution (0.9% NaCl). The volume of MPCM at equilibrium increases to 223% of its original dry volume in saline solution. Swell test results indicate that the hydrophilicity of MPCM is greater than that of chitosan. It has been reported that the swelling behavior of chitosan hydrogels depends on the ionizable groups present in the gel structure. Ray et al., Development and Characterisation of Chitosan Based Polymer Hybrids, Designed Monomers & Polymers, Vol. 13, 3, 193-206 (2010). By the solution in the range of pH3~6 the -NH ₂ group of the MPCM is protonated, rapid swelling behavior of MPCM in deionized water may be due to the high repulsive force of _-NH ^{3 +} group. In saline solution, at pH higher than 6, the carboxylic acid groups are ionized and the electrostatic repulsion between charge sites (COO ⁻ ) causes an increase in swelling. Yazdani-Pedram et al., Supra; Radhakumari et al., “Biopolymer composite of Chitosan and Methyl Methacrylate for Medical Applications,” Trends Biometer. Artif. Organs, 18, 2, (2005); Felinto et al., “The well-being of of chitosan hydrogel membranes ob- tained by UV-and γ-radiation, 4 Re-synthetic. I want to be.

MPCM samples were submerged in various concentrations of HCl, HNO ₃ , and H ₂ SO ₄ acid for 24 hours. Chitosan tends to form a gel in acidic media, which is unsuitable for use in adsorption columns for separating metal ions from aqueous solutions. One of the main objectives of this study was to create a chitosan-based acid resistant material while exposing more of the —NH ₂ group, which is an active metal binding site in chitosan. Table 1 shows the results of acid resistance ability of MPCM. It has been observed that the MPCM material exhibits a better HCl resistance than the resistance for HNO ₃ and H ₂ SO ₄ . The physical size and shape of MPCM did not show any significant difference in HCl up to 12M, H ₂ SO ₄ up to 12M, HNO ₃ solution up to 3.9M, but in 7.8M HNO ₃ solution MPCM appeared to dissolve completely. It is clear that MPCM is acid resistant compared to chitosan.

  FIG. 3 shows the XRD pattern of pure chitosan and MPCM beads. The chitosan sample shows a diffraction peak near 20 °, indicating a relatively regular crystal lattice (110,040) of chitosan. See Wan et al., “Biodegratable Polylactide / Chitosan Blend Membranes,” Biomacromolecules 7 (4): 1362-1372 (2006). The peaks observed for MPCM appear to be broad, indicating that the MPCM sample is essentially amorphous. It has also been shown that chitosan and glutaraldehyde form a complex in the presence of acid, and thus the crystal structure of chitosan was destroyed by the chemical bond between chitosan and glutaraldehyde.

Fourier Transform Infrared Spectroscopy (FTIR) of the MPCM sample prepared above was examined with a BRUKER FTIR spectrometer equipped with a broadband N ₂ cooled mercury-cadmium-telluride (MCT) detector and a KCl beam splitter. FTIR spectra were collected in the absorption mode resolution ^{8 cm -1} using 128 scans the range of 400~4000cm ^-1. The intermolecular interaction between chitosan and glutaraldehyde in the presence of HCl acid is reflected as a change in IR peak characteristics. FIG. 4 shows a comparison of the IR spectra of chitosan and MPCM. In the 2900 cm ^{−1 to} 3500 cm ⁻¹ region of the spectrum, chitosan and MPCM show peaks at 3498 cm ⁻¹ and 2950 cm ⁻¹ , respectively, which indicate stretching of the O—H and N—H groups and CH and —CH _2. Corresponds to the stretching vibration of C—H. The peak at 1350 to 1450 cm ⁻¹ indicates an alkane C—H deflection.

The complex nature of the absorption spectrum in the 1650-1500 cm ⁻¹ region suggests that the aromatic ring band and double bond (C═C) vibration overlap with the C═O stretching vibration band and the OH bending vibration band. doing. The expected peaks in this region of the IR spectrum include protonated amine (—NH ₃ ⁺ ), amine (—NH ₂ ), and carbonyl (—CONHR) bands. Figure 4 shows a peak at 1600 cm ^-1, shoulder-like peak centered around about 1570 cm ^-1 and 1670 cm ^-1, respectively, represent an -NH ₂ and amide I of chitosan. However, the presence of a relatively sharp peak at 1590 cm ⁻¹ in MPCM than that observed for chitosan suggests the presence of an NH ₃ ⁺ band in the MPCM sample.

To gain a better understanding of the intermolecular interaction between chitosan and glutaraldehyde, XPS analysis of chitosan and MPCM samples prepared as described above was performed. In XPS analysis, a survey scan was used to confirm that the energy range was suitable for detecting all elements. XPS data was obtained using a KRATOS model AXIS 165 XPS spectrometer with monochromatic Mg X-rays (hν = 1253.6 eV) used as an excitation source at a power of 240 W. The spectrometer was equipped with an 8-channel hemispherical detector and used a path energy of 5 to 160 eV when analyzing the sample. Each sample was exposed to X-rays for the same period and intensity. The XPS system was calibrated using the UO ₂ (4f7 / 2) peak, but its binding energy was 379.2 eV. A probe angle of 0 ° was used for sample analysis.

  FIG. 5 shows the peak positions of C1s, O1s, and N1s obtained by the respective survey scans of chitosan and the MPCM sample prepared above. FIG. 6 shows the detailed peak positions of C1s, O1s, and N1s present in chitosan and MPCM. The observed C1s peak showed two peaks by deconvolution, one was 284.3 eV CN and the other was 283.5 eV CC (FIG. 6a). In the MPCM sample, the C-Cs peak appeared to be folded and slightly shifted, but the C-N peak showed higher intensity compared to chitosan (Figure 6a). Oxygen-containing group (O1s) peaks were found at 530.5 eV and 531.1 eV for chitosan and MPCM, respectively (FIG. 6b).

Compared to MPCM C1s and O1s peaks, the cross-linking reaction with glutaraldehyde causes the chitosan CC peak at 283.5 eV to fold and the O1s peak to shift from 530.5 eV to 531.1 eV. Observed. This suggests that the O1s component can be a single bond corresponding to the —OH or C—O moiety in the structure for various surface oxygen-containing functional groups. See Wen et al., “Copper-based nanomaterials: Templated Synthesis, Characterizations, and Applications,“ Langmuir, 21, 10, 4729-4737 (2005). A chemical shift is considered significant when it exceeds 0.5 eV. Hasan et al., “Adsorption of divergent cadmium from aquaous solutions on chitosan-coated perlite beads,” Ind. Eng. Chcm. Res. 45, 5066-5077 (2006). As a result, the shift of the O1s peak in the MPCM sample also indicates that glutaraldehyde reacted with the oxygen-containing functional group of chitosan. XPS data suggests that the chemical bonding of glutaraldehyde occurs at the —CH ₂ OH or OH group of the chitosan structure, which is also consistent with the data obtained from FTIR analysis (FIG. 4).

The N1s peak for chitosan was 397.5 eV (FWHM 1.87) for nitrogen in the —NH ₂ group of chitosan (FIG. 5c), whereas for MPCM, the N1s peak appeared at 397.7 eV. One of the purposes of examining the N1s peak was to identify whether the amine group, which is an active metal binding site in chitosan, is involved in the crosslinking reaction with glutaraldehyde. FIG. 6c shows a strong N1s peak at 397.7 eV that can be assigned to the —NH ₂ group for MPCM, suggesting that the amine group of chitosan was not affected by the cross-linking reaction with glutaraldehyde. doing. This is also evident from the FTIR spectrum (Figure 4).

Table 2 shows the XPS data of the surface chemistry analysis of the MPCM sample determined from the peak area after correction for the experimentally determined sensitivity factor (± 5%). By preparing a porous chitosan-based material, it has now been found that more NH ₂ groups are exposed on the surface of the material in this MPCM embodiment. The nitrogen concentration determined from the N1s peak in the MPCM sample was approximately twice that calculated for chitosan (Table 2). The nitrogen content in MPCM is believed to have been derived entirely from chitosan. As shown in Table 2, the high chitosan content of MPCM is due to the microporous nature of MPCM, and more amine groups are available on the surface than non-porous chitosan. This is also consistent with the results obtained by dispersing chitosan on perlite reported by Hasan et al., Supra. Compared to chitosan, the change in C1s peak intensity of the MPCM sample and the binding energy of the O1s peak at 531.0 eV is believed to be due to reaction with glutaraldehyde in the presence of acid as a catalyst.

Energy dispersive spectroscopy (EDS) X-ray microanalysis was performed on the same MPCM sample used for SEM micrographs. EDS microanalysis was used for elemental analysis of MPCM (Figure 7). Carbon, oxygen, and nitrogen peaks are shown at 0.3 keV, 0.36, and 0.5 keV, respectively, which are the main components of chitosan (FIGS. 7a, 7b). Reaction with glutaraldehyde increases the intensity of the carbon peak of MPCM; whereas the intensity of the oxygen peak decreases compared to chitosan (FIG. 7b). FIG. 7b also shows that the nitrogen peak present in the MPCM sample shifted due to protonation of the amine group (—NH ₂ ) compared to the nitrogen peak in chitosan. Based on FTIR, EDS, and XPS analyses, and not wishing to be bound by theory, the possible reaction mechanism between glutaraldehyde and the —OH group of chitosan through the formation of an acetal bond is shown in FIG.

The above MPCM samples were evaluated for radiation stability by irradiation with a ⁶⁰ Co radiation source. FIG. 9 shows IR spectra of the MPCM composite sample before and after irradiation using a ⁶⁰ Co radiation source. The results in FIG. 9 show that an MPCM sample suspended in pH 3.0 water can withstand about 50,000 krad of gamma radiation without losing a substantial percentage of its identity.

FIG. 7c shows EDS spectra of chitosan and MPCM particles before and after irradiation at 50,000 krad with a ⁶⁰ Co source. FIG. 7c shows that the intensity of the carbon, oxygen, and nitrogen peaks did not change substantially after irradiation of the sample. FIG. 10 shows the peak positions of carbon, oxygen, and nitrogen obtained by XPS analysis of the MPCM sample before and after irradiation. It was observed that the magnitude of the binding energy of the entire C1s peak changed after irradiation as shown in Table 2. The C1s peak of the MPCM sample was 283.5 eV, but two peaks were observed at 283.5 and 284.5 eV in the MPCM sample after irradiation (FIG. 10a). The N1s peak present in the vicinity of 397.5 eV of the MPCM sample after irradiation can be assigned to the NH ₂ group of the MPCM structure. No change was observed for the O1s peak of the irradiated MPCM sample. The magnitude of the binding energy shift depends in particular on the concentration of various atoms on the material surface. Compared to XPS (FIGS. 10a-c), the N1s and O1s peaks of the MPCM samples did not shift before and after irradiation (Table 2), indicating that the chemical state of N atoms was not significantly affected after irradiation. This is also reflected in the EDS and FTIR spectra as shown in FIGS.

The above MPCM samples were evaluated for molybdenum adsorption using a batch technique. About 1.0 gram of MPCM adsorbent was suspended in a 100 mL solution containing ammonium molybdate ranging from 1 mmol / L to 94 mmol / L. The initial pH value of the solution was adjusted from 2.0 to 8.0 using either 0.01 M NaOH or 0.1 M HCl solution. The solution was then maintained at 298K for 24 hours in a shaker (160 rpm). After 24 hours, the final pH of each solution was recorded and the solution was centrifuged at 3000 rpm for 5 minutes to separate the supernatant from the solution. The supernatant was then filtered through a 0.45 μm membrane filter and the filtrate was analyzed for molybdenum removal by inductively coupled plasma (ICP) (Agilent 7700X) equipped with a mass analyzer for molybdenum detection. Adsorption isotherms were obtained by changing the initial concentration of molybdenum in the solution. The amount of molybdenum adsorbed per unit mass of adsorbent (q _e ) was calculated using the following formula:

Where C _i and C _e represent the initial and equilibrium concentrations expressed in mg / L, V is the amount of solution expressed in liters (L), and M is the adsorbent expressed in grams (g). Is the mass.

The surface charge of the MPCM sample beads was determined by standard potentiometric titration in the presence of symmetric electrolyte sodium nitrate as described above by Hasan et al. The magnitude and sign of the surface charge was measured with respect to the zero charge point (PZC). The pH at which the solid's true surface charge is zero at all electrolyte concentrations is called the zero charge point. The pH of the PZC for a given surface depends on the relative acid-base properties of the solid and allows estimation of the true uptake of H ⁺ and OH ⁻ ions from the solution. The results are shown in FIG.

The PZC value of the MPCM sample prepared as described above was found to be 8.8, which was similar to that reported by Hasan et al., Supra for chitosan coated perlite beads. However, the PZC value of pure chitosan has been reported to be in the range of pH 6.2-6.8. See Hasan et al., Supra. From FIG. 11, it can be observed that the positively charged surface was dominant in the relatively low pH range. The surface charge of MPCM was almost zero in the pH range of 7.5 to 8.8. The protonation of MPCM increased rapidly in the pH range of 7.5 to 2.5, and the surface became positive. When the pH was below 2.5, the difference between the initial pH and the pH after the equilibration time was not significant, suggesting that the amine group (—NH ₂ ) present in MPCM was fully protonated. At higher pH 7.5-8.8, the surface charge of MPCM decreased gradually, indicating slower protonation of MPCM. In the case of chitosan, the degree of protonation has been reported to be as high as 97% at pH 4.3. However, this decreases with increasing pH. The degree of protonation on the chitosan surface has been reported to be 91%, 50%, and 9% at pH 5.3, 6.3, and 7.3, respectively. See, Hasan et al., “Dispersion of chitsan on perl for enhancement of copper (II) adsorption capacity” Journal of Hazardous Materials, 522, 826-837, 2008.

  While not wishing to be bound by theory, it is believed that the PCMC value of 8.8 and surface charge behavior of MPCM is due to the modification of chitosan when cross-linked with glutaraldehyde in the presence of acid as a catalyst, which makes MPCM pH 7 It becomes essentially amorphous in the range of .5 to 8.8.

The effect of pH on the adsorption of molybdenum by MPCM was investigated by changing the pH of the solution between 2-8 (FIG. 12). The pH of the molybdenum solution, initially adjusted to 2-8 using one of 0.1 N H ₂ SO ₄ or 0.1 M NaOH, and then added MPCM. As adsorption progressed, the pH of the solution gradually increased. No attempt was made to maintain a constant pH of the solution during the course of the experiment. The molybdenum uptake at the solution concentration at equilibrium is shown in FIG. 12 for solutions with different initial pH values. The uptake of molybdenum by MPCM increased as the pH increased from 2 to 4. Maximum uptake was observed at pH 3, but as solution pH increased above 6, molybdenum uptake into MPCM began to decrease. Therefore, the experiment was not performed at a pH higher than the PCM of the MPCM sample.

In order for the metal to be adsorbed from the solution to the adsorbent, the metal must form ions in the solution. The type of ions formed in the solution and the degree of ionization depend on the pH of the solution. In the case of MPCM, the main functional group involved in the adsorption of metal ions is an amine group (—NH ₂ ). Depending on the pH of the solution, these amine groups undergo protonation to NH ₃ ⁺ or (NH ₂ —H ₃ O) ⁺ , and the rate of protonation depends on the pH of the solution. Thus, the surface charge on the MPCM determines the type of bond formed between the metal ion and the adsorbent surface. Depending on the pH of the solution, molybdenum in the aqueous solution can be hydrolyzed to form various species. At relatively high and low pH values, both MoO ₄ ²⁻ and various isopolyanions (mainly Mo ₈ O ₂₄ ⁶⁻ ) dominate. MoO ₄ ^2- anions are formed into many different polyanions in acidic solution. Guibal et al., “Molybdenum Sorption by Cross-linked Chitosa Beads: Dynamic Studies”. Water Environment Research, 71, 1, 10-17, 1999; Merce et al., “Molybdenum (VI) Binded to Humic and Nitrohumic Acid Models in Aquatic Solutions, 3-Nitralic, 3-Nitralic. 2 "J. Braz. Chem. See Soc, 17, 3, 482-490, 2006. Even if polyanions are present in the solution, it is reported that adsorption still occurs via MoO ₄ ²⁻ . Jezlorowski et al., "Raman and Ultraviolet Spectroscopic Characterization of Molybdena on Alumina" The Journal of Physical Chemistry, 83,9,1166-1173,1979; El Shafei, et al., "Association of Molybdenum Ionic Species with Alumina Surface," Journal of Colloid and Interface Science, 228, 105-113, 2000. Degradation of the polyanion in solution occurs by an increase in local pH close to the adsorbent surface.

As described above, MPCM was observed to have a maximum adsorption capacity around pH 3 from a molybdenum ion solution. Without wishing to be bound by theory, the amine group of MPCM has a lone pair from nitrogen, which is thought to act primarily as an active site for complexation with metal ions. As mentioned earlier, at lower pH values, the amine group of MPCM undergoes protonation to form NH ₃ ⁺ , resulting in an increase in electrostatic attraction between NH ₃ ⁺ and the sorbate anion. The main species adsorbed by Coulomb interaction is probably anionic molybdenum (Mo (VI)) since the surface of MPCM exhibits a positive charge in the range of pH 2.5-7.5. As mentioned earlier, the pH of the solution was found to increase after adsorption, due to H ⁺ ions released from the surface of MPCM as a result of adsorption of molybdenum-containing anions from the solution. It can be. In the case of MPCM, NH ₂ group protonation occurs in the somewhat lower pH range. The fact that the pH of the solution increases as the adsorption proceeds suggests that Mo (VI) has formed a covalent bond with the NH ₂ group.

When the equilibrium pH increases from a lower pH to the pH of the _PZC (pH _PZC ), the decrease in the rate of Mo (VI) removal indicates the electrostatic attraction between the surface of the MPCM and the anionic Mo (VI) species. The decrease was caused by It can be seen that MPCM PZC was found to shift towards 4.5 in the presence of molybdenum ions compared to MPCM PZC in the absence of said ions (FIG. 11). . The shift of MPCM PZC towards lower pH indicates strong specific adsorption, and inner-sphere surface complexation occurs by molybdenum adsorption. Similar findings were reported by the adsorption of molybdenum on gibbsite. Goldberg, S.M. “Competitive Adsorption of Polybdenum in the Presence of Phosphorus or Sulfur on Gibbsite,” Soil Science, 175, 3, 105-110, 2010. Based on surface charge analysis and pH testing, the reaction mechanism that occurs between the surface of MPCM and the molybdenum species in solution is shown in FIG.

  The equilibrium adsorption isotherm of molybdenum uptake into MPCM was determined at a temperature range of 298 K with a concentration range of 1 mmol / L to 94 mmol / L. As mentioned in the previous chapter, the maximum adsorption capacity of molybdenum on MPCM occurs at pH 3. Therefore, equilibrium isotherm experiments were performed at pH 3 unless otherwise stated. Concentration profiles upon molybdenum uptake by MPCM from various concentrations of solution indicate that approximately 60% of the molybdenum was adsorbed during the first 4 hours of the experiment. Equilibrium was achieved monotonically in 24 hours in most of the experiments.

  MPCM materials contain amino groups that are available for characteristic coordination bonds with metal ions. If the adsorption of metal ions is pH dependent, it can be explained by the following single-site Langmuir equation. The effect of pH was incorporated by introducing a parameter “α” that depends on the pH of the solution. The formula is shown below:

In the formula, q is an adsorption capacity corresponding to the metal ion concentration [M], q _m represents a maximum adsorption amount (mmol / g) of molybdenum ions, and [H ⁺ ] is a hydrogen ion concentration. K _H and K _M are equilibrium concentrations. Equation 5 was used to correlate the adsorption capacity of MPCM. The molybdenum equilibrium data can be correlated with the Langmuir equation within ± 5% of the experimental value. The constants of Equation 5 are obtained by nonlinear regression of experimental data and are shown in Table 3. Equation 5 was found to adequately represent the adsorption behavior of molybdenum on MPCM (FIG. 14). The adsorption isotherm data obtained at pH 3 showed type I behavior.

This suggests a monolayer adsorption of molybdenum on MPCM. Table 3 shows the maximum adsorption capacity of MPCM for Mo (VI) using Langmuir's equation (Equation 5). The adsorption capacity of MPCM with respect to molybdenum is approximately 6.25 mmol of molybdenum per gram of MPCM at 298 K when the equilibrium concentration of Mo (VI) in the solution is 54.1 mmol / L and the initial pH of the solution is 3.0. (Fig. 14). The NH ₂ group of MPCM is the main active site for molybdenum adsorption. As can be seen from FIG. 13, two NH ₂ groups are required for one molybdenum ion to adsorb. Other surface sites such as MPCM CH ₂ OH or OH groups are involved in molybdenum adsorption in pH 3 solutions. The adsorption capacity of MPCM irradiated with 50,000 krad was also performed for molybdenum uptake from aqueous solution. It was observed that the adsorption capacity of irradiated MPCM did not change substantially as shown in Table 3.

A column was used to test the adsorption of Mo (VI) in the presence or absence of ions in solution in a dynamic state. Approximately 1.125 grams of MPCM was used to make a 2.5 cm ³ column with an inner diameter of 0.5 cm and a height of 3.2 cm. A flow rate of 1 mL / min was used for the outflow. Outflow continued for 1500 minutes and samples were taken at regular intervals at the exit of the bed. The bed saturates during this period as indicated by the outlet Mo (VI) concentration. When the injection concentration was 5.23 mmol / L Mo (VI) at pH 3 and the flow rate in the column was 1 mL / min, molybdenum leaked from the column after 320 bed volumes (FIG. 15a). Full saturation of the column occurred after 500 bed volumes. Leak curves were also obtained at pH 6.86 and 4.0, respectively, from a mixed solution containing 5.21 mmol / L Mo (VI) and 153.8 mM / L NaCl (Figure 15b). In either case, the solution passed through a column similar in size to the previously mentioned column, maintaining the same bed height and flow rate. The column was observed to leak rapidly at 42 bed volumes for the mixed solution at pH 6.86, but approximately 125 bed volumes were required for the mixed solution to leak from the column at pH 4.0. It is important to note that the leakage time of molybdenum solutions with 153.8 mM / L NaCl can be delayed by using a larger amount of MPCM adsorbent and a longer column. Since the objective was to investigate the effect of the pH of the injected mixed solution on the leakage characteristics of Mo (VI) from the column, no attempt was made to determine the bed length that would extend the mixed solution leakage time.

Using the long half-life technetium ( ⁹⁹ Tc), the ability of MPCM to adsorb technetium from aqueous solutions in the pH range of 3 to 11 in the presence and absence of other ions was evaluated. Technetium is chemically inert and has a number of oxidation states from I to VII. The most prevalent species of technetium found in the wastewater stream is pertechnetate (TcO ₄ ⁻ ). Gu et al., Development of Novell Bifurcation Anion-Exchangc Resin with Improved Selectivity for Pertechnetation formated groundwater. Sci. Technol. 34, 1075-1080, 2000. The adsorption of pertechnetate (TcO ₄ ⁻ ) from aqueous solution onto MPCM was tested in batch equilibrium conditions according to the process outlined elsewhere. The effect of pH on technetium adsorption on MPCM was evaluated in the range of pH 3 to 11 using solutions containing 0.11 μmol / L technetium in the presence and absence of 0.9% NaCl, respectively. did. While examining the effect of pH on adsorption capacity, the initial pH of the solution was adjusted to the desired value by adding either 0.1 M HCl or 0.1 M NaOH. The pH of the solution was not controlled during the adsorption process. After the adsorption experiment, the solution was filtered and the activity of ⁹⁹ Tc in the filtrate collected in the vial at a predetermined time was evaluated using a liquid scintillation counter (Packard Tricarb 2900TR). The amount of technetium adsorbed on MPCM was determined according to Equation 2.

Table 4 shows that the adsorption of technetium on MPCM is pH independent in solutions in the pH range 3-11. Approximately 95% of 1 μM technetium in 1 L of solution was adsorbed to MPCM in the range of pH 3-11, but in the presence of 0.9% NaCl, technetium removal is reduced to 56% in the range of pH 3-11. It was observed. As mentioned earlier, MPCM exhibits a positive charge in the range of pH 3-7.5. The presence of —NH ₂ groups, CHOH groups, and CH ₂ OH groups on the MPCM surface is confirmed by the FTIR spectrum of MPCM (FIG. 4). It was hypothesized that positive charge occurs due to protonation of the surface region of MPCM in the range of pH 3 to 7.5, and technetium undergoes covalent bonding with the positive surface region of MPCM. The presence of 0.9% NaCl in the solution reduced the adsorption capacity of MPCM for technetium because pertechnetate ions had to compete with chloride ions in solution. Moreover, uptake of technetium in the pH range of 9-11 in the presence of 0.9% NaCl solution can correspond to ion exchange reactions occurring in this pH range. From the results shown in Table 4, it is confirmed that MPCM has a strong affinity for pertechnetate ions from an aqueous solution.

MPCM was also used to form Mo (VI) from a mixed solution containing 1 mmol / L Mo (VI) and 0.11 μmol / L pertechnetate in the presence or absence of 0.9% NaCl. Tc (VII) was adsorbed simultaneously. MPCM was found to simultaneously adsorb molybdenum and technetium from a pH 3 solution. It was observed that approximately 95% of 0.11 μmol pertechnetate adsorbs on the MPCM surface, while 99% of 1 mmol molybdenum adsorbs from the mixed solution. In the presence of molybdenum (MoO ₄ ²⁻ ) in solution, pertechnetate (TcO ₄ ⁻ ) had to compete for the positive surface area of MPCM. In another attempt, adsorption of technetium on MPCM from a mixed solution containing 153.8 mmol / L NaCl, 1 mmol / L Mo (VI), and 0.11 μmol / L pertechnetate was investigated. Table 5 shows that molybdenum (MoO ₄ ²⁻ ) was preferentially adsorbed on the MPCM surface, but the adsorption of pertechnetate (TcO ₄ ⁻ ) was 55% of 0.11 μmol / L technetium in the mixed solution. It shows that it was reduced. In the presence of 0.9% NaCl, it is hypothesized that adsorption of pertechnetate (TcO ₄ ⁻ ) to the MPCM surface was reduced by competing with chloride ions for surface sites in the pH 3 solution. In another attempt, pertechnetate adsorption on MPCM was investigated using a 1 cm ID column. A column was prepared by MPCM and this was initially packed with Mo (VI). Using a batch equilibration process, if the equilibrium concentration of Mo (VI) in the solution is 54 mmol / L and the initial pH of the solution is 3.0, 6.25 mmol of Mo (VI) per gram of MPCM is 298K. Adsorbed. A 2.5 cm ³ bed was prepared using approximately 1.125 grams of Mo (VI) filled MPCM. A saline (0.9% NaCl) solution supplemented with 0.25 mM / L was passed through the column at a flow rate of 1 mL / min using a peristaltic pump during the outflow.

FIG. 16 shows that pertechnetate anions have an affinity for the available surface sites of MPCM in the presence of molybdenum (MoO ₄ ²⁻ ) anions. At 10 bed volumes, it was observed that pertechnetate with an injection concentration of approximately 15% was eluted with saline solution (0.9% NaCl). It can be seen that approximately 60% of the injected pertechnetate concentration was obtained in the eluate collected at 20 bed volumes (FIG. 15). The column reaches saturation fairly rapidly for technetium while an additional 40 bed volume of technetium-added saline solution passes through the column. After the column reached its saturation with respect to technetium, over 95% of the technetium applied to the column was recovered from the column outlet as eluent. The purpose of this study was to determine the maximum amount of pertechnetate (TcO ₄ ⁻ ) uptake into MPCM loaded with 6.25 mM Mo (VI) per gram of MPCM. No attempt was made to determine the bed length to reduce the release of pertechnetate from the Mo (VI) filled MPCM bed.

Batch and column tests showed that MPCM showed excellent adsorption capacity for Tc (VII), but its removal from the bed was a challenge. In order to examine the detachment of technetium from the MPCM sample, a technetium packed MPCM bed was prepared in the column. Adsorption of technetium on MPCM was performed under batch equilibrium conditions. It was observed that approximately 0.12 μM ⁹⁹ Tc per gram of MPCM was adsorbed from a solution having a ⁹⁹ Tc concentration of 0.48 μM / L at a temperature of 298 K. ^{For the 99} Tc desorption test, a column was prepared using about 1.125 grams of MPCM containing 0.12 μM ⁹⁹ Tc per gram of MPCM. Pertechnetate is water soluble and therefore deionized water was used to regenerate technetium from the column. It was observed that only 1% technetium was detached from the MPCM bed using 10 bed volumes of water. Preliminary tests have shown that complete recovery of technetium from MPCM is a challenge even when using various concentrations of NaCl solution. It was observed that approximately 50 bed volumes of 1.5% NaCl were required to regenerate 10% of ⁹⁹ Tc from the column. Similar concentrations of low concentration (<1M (less than 1M)) acid solutions of HCl, H ₂ SO ₄ , and HNO ₃ were also used but did not yield any significant regeneration. In another attempt, MPCM adsorbents were oxidized with various concentrations of potassium permanganate or hydrogen peroxide to investigate the effect of oxidation on technetium adsorption / desorption for oxidized MPCM adsorbents.

[Example 2]
In another embodiment, MPCM was oxidized with various concentrations of hydrogen peroxide in the presence or absence of a transition metal catalyst. The temperature was also changed. An oxidation test of MPCM with hydrogen peroxide was performed to determine whether only controlled oxidation would improve the recovery of technetium from technetium-filled MPCM. The hydrogen peroxide concentration was varied from 1% to 5%. Technetium was adsorbed on oxidized MPCM using a batch technique. Technetium regeneration from oxidized MPCM was performed in the column. Columns were prepared with 0.12 μmol ⁹⁹ Tc per gram of oxidized MPCM. The column was regenerated and technetium was desorbed from the MPCM using a 0.9% NaCl solution. Since 10-17% of the available technetium was recovered from the oxidized MPCM bed, it was observed that the recovery of technetium was not as high as desired (Table 6). Moreover, the adsorption of Mo (VI) to peroxide oxidized MPCM was reduced to 4.6 mmol / g compared to 6.25 mmol / g adsorbed by non-oxidized MPCM.

[Example 3]
MPCM was also oxidized using potassium permanganate solution. The concentration and oxidation time of potassium permanganate solution were determined based on trial and error. The potassium permanganate concentration and the pH of the solution were varied from 0.1% to 5% and 3 to 11, respectively. The oxidation time was varied from 30 minutes to 24 hours. In order to elucidate the adsorption pattern of pertechnetate (TcO ₄ ⁻ ) on oxidized MPCM, surface charge analysis of oxidized and non-oxidized MPCM loaded with Mo (VI) was also performed.

  A permanganate solution containing 0.04 mmol of Mn per liter of solution in the pH range of 3 to 4.5 and a period of 12 hours partially maximized molybdenum uptake and simultaneous release of technetium from the MPCM adsorbent. It was observed to be sufficient to oxidize MPCM to promote. Batch technology was used to evaluate the performance of oxidized MPCM for molybdenum adsorption from aqueous solutions. Oxidized MPCM was found to be able to adsorb 6.25 mmol Mo (VI) per gram of MPCM at 298 K when the equilibrium concentration of Mo (VI) in solution is 54 mmol / L at pH 3.0. .

In another attempt, two different columns were prepared using oxidized MPCM and oxidized MPCM loaded with 6.25 mmol Mo (VI) per gram of MPCM, respectively. A 0.9% NaCl solution with about 0.11 μmol pertechnetate (TcO ₄ ⁻ ) added per liter of solution was passed through both columns at a flow rate of 1 mL / min. Pertechnetate (TcO ₄ ⁻ ) did not adsorb to oxidized MPCM in the presence or absence of Mo (VI) loading, and approximately 90% of the pertechnetate (TcO ₄ ⁻ ) in solution was It was interesting to see that it passed through both columns as eluent. The results confirm that pertechnetate (TcO ₄ ⁻ ) did not adsorb to either oxidized MPCM or oxidized MPCM loaded with Mo (VI). The purpose of this study was to maximize Mo (VI) uptake while simultaneously enhancing technetium release from MPCM surface sites.

MPCM shows a large affinity for both Mo (VI) and Tc (VII) from aqueous solution. From the surface charge of the Mo (VI) -filled MPCM, it was revealed that Mo (VI) is adsorbed to the MPCM through the inner sphere surface complex formation reaction (FIG. 11). It can be seen that the Mo (VI) filled MPCM showed a positive charge in the range of pH 3-4.5. Thus, the anionic pertechnetate probably formed a covalent bond with the available positive surface area. Interestingly, the adsorption of pertechnetate to MPCM from solutions containing 0.9% NaCl in the pH range 3-8 is approximately 55% (Table 4). Nearly 95% of 1 mmol pertechnetate was adsorbed to MPCM in the presence of 1 mmol Mo (VI) in solution. This confirms that pertechnetate (TcO ₄ ⁻ ) was adsorbed on the MPCM surface site.

Permanganate ions are essentially both acid and base. In acidic solution, the Mn (VII) ion of potassium permanganate is transformed into possible intermediate products such as Mn (VI), Mn (V), Mn (IV), and Mn (III). Is finally reduced to Mn (II). See Dash et al., "Oxidation by Permanganate: Synthetic and mechanical aspects" Tetrahedron, 65, 707-739, 2009. Permanganate (MnO ₄ ⁻ ) content in potassium permanganate has been reported to be a reactive oxidizing species for acid-catalyzed permanganate oxidation of chitosan. Ahmed et al., “Kinetics of Oxidation of Chitosan polysaccharide by Permanganate Ion in Aqueous Percolate Solutions,” Journal of Chemical Research 4, v 2003. See 182-183, 2003. In an acidic medium, possible reactions between MnO ₄ ⁻ ions and H ⁺ are as follows:

Although HMnO ₄ species can be formed by protonation of MnO ₄ ⁻ ions in acidic solution, it is also a strong oxidant. See Sayyed et al., “Kinetic and Mechanical Study of Oxidation of Establish by KMnO ₄ ” International Journal of ChemTech Research, v2, n1, p242-249, 2010. Forming colloidal MnO ₂ is, MnO ₄ ^- by the reaction between the ^{H +,} and it can occur depending on the solution acidity, these are subjected to further reaction with ^{H +,} a _Mn ^{2 +} in solution Can be generated. Ahmed et al., 2002 reported that chitosan was oxidized by permanganic acid as an acid-catalyzed reaction, thereby forming a diketo acid derivative of chitosan. Ahmed et al., “Kinetics of Oxidation of Chitosan polysaccharide by Permanganate Ion in Aqueous Percolate Solutions” Journal of Chemical Research, v2003. See 182-183, 2003.

In the acid-catalyzed permanganate oxidation of MPCM, permanganate (MnO ₄ ⁻ ) ions can be considered as reactive oxidants. The effect of permanganate oxidation on MPCM on the simultaneous release from Mo (VI) and Tc (VII) adsorption and oxidized MPCM surface was evaluated by surface charge analysis of MPCM samples. Oxidation of MPCM with potassium permanganate changes its adsorption selectivity from aqueous solutions. FIG. 17 shows the surface charge pattern of Mo (VI) loaded MPCM samples in the presence or absence of oxidation. In the case of non-oxidized MPCM samples loaded with Mo (VI), surface protonation appeared to increase gradually in the pH range of 4.5-3. Therefore, in this pH range, the formation of a covalent bond between the positive surface portion of the Mo-filled MPCM surface and pertechnetate can occur. At pH <2.9, the difference between the initial pH of MPCM loaded with Mo (VI) sample and the pH after equilibration time is not significant, suggesting that the MPCM sample is fully protonated.

The surface charge of oxidized MPCM filled with Mo (VI) shows almost zero charge in the range of pH 3 to 4.5 as compared to Mo (VI) filled into the non-oxidized MPCM sample (FIG. 17). In the acidic pH range of pH 3 to 4.5, the surface functional groups of non-oxidized MPCM show a positive charge, which can further undergo a reaction with MnO ₄ ⁻ during the oxidation reaction. Manganese (MnO ₄ ⁻ ) ions are assumed to enter the MPCM porous matrix, partially oxidize the positive surface functionality by donating electrons, and then reduced to Mn ²⁺ ions in solution. The Furthermore, the formation of colloidal manganese in the solution was controlled by controlling the solution pH in the range of pH 3 to 4.5, more specifically pH 4. Moreover, the ratio of Mn ²⁺ ions to the positive surface area of MPCM is convenient for further adsorption of Mn ²⁺ ions on the MPCM surface. It was observed from both batch and column studies that technetium does not adsorb to Mo (VI) -filled oxidized MPCM, but it shows a strong affinity for Mo (VI) -filled non-oxidized MPCM samples. This was due to the lack of positive charge on the Mo (VI) -filled oxidized MPCM surface, which did not attract technetium and formed a covalent bond compared to the non-oxidized MPCM surface filled with Mo (VI). It is shown that. It is interesting that technetium did not adsorb to the oxidized MPCM, but it was found that approximately 95% of the 1 mmol solution of technetium was adsorbed to the non-oxidized MPCM. This confirms that technetium was adsorbed on the surface of non-oxidized MPCM but not adsorbed on oxidized MPCM through covalent bonds.

An equilibrium batch adsorption test was performed by exposing oxidized MPCM to a 1% Mo (VI) solution supplemented with 5.0 mL of ⁹⁹ Mo (2 mCi / mL). First, 1% molybdenum was prepared by dissolving 4.5 mL ammonium hydroxide and 1.5 g MoO _{3 in} 95 mL deionized water. The mixture was maintained with stirring until the MoO ₃ was completely dissolved in the solution. A solution containing 5.0 mL of ⁹⁹ Mo (2 mCi ⁹⁹ Mo / mL) was thoroughly mixed with 97.5 mL of 1% molybdenum solution. The pH of the added solution was adjusted to 3 using either 0.1N HCl or NaOH solution. The final specific activity of Mo (VI) in solution was 78.12 μCi / mL.

About 0.5 grams of oxidized MPCM was added to a 125 mL plastic vial containing 50 mL of added solution. The solution was maintained on a shaker (160 rpm) at 25 ± 1 ° C. for 3 hours. Another set of similar experiments was also performed to perform data replication experiments. After 3 hours, the final pH of the solution was recorded and the solution was centrifuged at 3000 rpm for 5 minutes to separate the MPCM from the supernatant solution. The Mo (VI) filled MPCM was rinsed twice with deionized water to remove any adhered Mo (VI) from the surface. MPCM loaded with Mo (VI), supernatant, and rinse solution was analyzed for molybdenum uptake using a dose calibrator and ICP-MS. At equilibrium, oxidized MPCM had a capacity of 2.47 mmol Mo per gram of MPCM, but the active 1300 μCi was observed to be derived from the added ⁹⁹ Mo.

The activity of ⁹⁹ Mo and ^99m Tc was evaluated using both a dose calibrator and a gamma-ray spectrometer. The dose calibrator (Atomlab 400) comprises a small lead sample container that effectively shields ^99m Tc gamma rays but allows most of the ⁹⁹ Mo gamma rays to pass through the shield to the detector. Therefore, the reading obtained when the sample is contained in a shielded container is assigned only to ⁹⁹ Mo activity. The reading obtained without shielding is the sum of both ⁹⁹ Mo and ^99m Tc activity.

After the batch adsorption experiment, MPCM packed with both ⁹⁸ Mo and ⁹⁹ Mo was transferred to a column (0.5 cm × 3.2 cm with polytetrafluoroethylene (PTFE) frit at the bottom). Both ends of the column were closed with a silicon rubber septum. The column was rinsed thoroughly with deionized water to remove any molybdenum solution on the MPCM surface. The rinsed sample was taken from the column using a vacuum vial. The column was allowed to stand for the maximum time necessary to produce the daughter product ^99m Tc from the decay of ⁹⁹ Mo remaining in the column, and then eluted with a saline solution (0.9% NaCl). The column was eluted with 9 mL of saline solution, which was then collected in 3 mL aliquots in 3 individual vacuum vials. The eluate was obtained from the column at predetermined time intervals. The eluate from each collection was analyzed for molybdenum and manganese released from the column using quadrupole inductively coupled plasma mass spectrometry (ICP-MS) equipped with an external calibrator. Activity associated with pertechnetate or ⁹⁹ Mo was assessed using a dose calibrator and gamma spectrometer.

FIG. 18 shows the elution profile of a column consisting of 0.5 grams of MPCM packed with 2.47 mmol of Mo (VI) per gram of oxidized MPCM derived from ⁹⁹ Mo adsorbed with 1300 μCi of activity. Elution of the column was started with saline solution (0.9% NaCl) the day after the column was prepared, and elution was continued for 8 days. Note that the first set of elutions (elution 1) was performed 8 hours after column preparation to confirm the desorption behavior of ^99m Tc from the MPCM column. The remaining elution numbers 2-8 were performed at 24 hour intervals, while elution number 5 was performed at least 45 hours after elution number 4. The elution efficiency of the daughter product ^99m Tc from the column was found to be in the range of 75-90% (FIG. 18). In elution 1, as shown in FIG. 18, over 80% of the activity with ^99m Tc was obtained in 9 mL of saline (0.9% NaCl), and 62% of the available ^99m Tc activity was with normal saline. Eluted in the first 3 mL volume of. When the second elution was collected 24 hours after the first elution, the ^99m Tc activity in the column was in the range of 70% -90% and could be recovered using 3-9 mL of saline solution. Is shown. In all cases, the eluate was clear and the pH was in the range of 6-7. The column was eluted continuously over 8 days with an average of about 82% of the total ^99m Tc eluting from the column.

FIG. 19 shows the percentage of ^99m Tc and Mo (VI) released from the column over 8 days. The concentration of Mo (VI) in the eluate was in the range of 1% to 3% of 6.25 mmol of Mo (VI) per gram of MPCM in the column. A process of capturing any molybdenum leakage from the column by passing it through the acid-catalyzed MPCM is possible, as shown in FIG. Is reduced to a very low level. Another way to control molybdenum leakage from the column can be achieved by controlling the pH of the saline solution (0.9% NaCl) in the range of 4-4.5 (FIG. 15). In that case, no additional guard column is needed to control leakage of Mo (VI) from the column.

[Example 4]
Generation of ^{99 Mo} by neutron capture method is attracting attention as a substitute for ^{99 Mo} from fission by nuclear proliferation problem. ⁹⁹ Mo produced by neutron activation of natural molybdenum provides a less complicated, less expensive and more practical path for the original production and use of ^99m Tc. However, it is clear that the specific activity produced by the neutron capture method is not high enough for the preparation of small chromatography generators. However, this limitation can be overcome by the use of an adsorbent such as MPCM that has a high adsorption capacity for molybdenum. MPCM can adsorb more than 6.25 mmol Mo (VI) per gram MPCM (600 mg Mo (VI) per gram MPCM) from aqueous solution at pH 3, which is also the natural (n, γ) reaction of molybdenum. It has been proved that the present invention can also be applied to ⁹⁹ Mo that can be easily obtained. Generator in this case ^consists MPCM filled with 99 Mo, In this way the chromatography generator (n, ^gamma) combines the performance of use of the 99 Mo. ^When used as an adsorbent in a ^99m Tc / ⁹⁹ Mo generator, MPCM can hold up to 60% by weight of its body weight compared to only 0.2% by weight for alumina. The potential of MPCM as an adsorbent for the preparation of a ⁹⁹ Mo / ^99m Tc generator has been investigated using a 1% Mo (VI) solution supplemented with ⁹⁹ Mo (2 mCi / mL). MPCM was observed to adsorb Mo (VI) to which ⁹⁹ Mo was added according to its proven volume from aqueous solution at pH 3. It was also observed that ^99m Tc, a decay product of ⁹⁹ Mo, was eluted with a normal (0.9%) saline solution, resulting in an elution of over 80%. A typical ^99m TC / ⁹⁹ Mo generator preparation flow sheet based on MPCM as adsorbent is shown in FIG.

[Example 5]
In an attempt to maximize Mo (VI) uptake and enhance technetium release from columns prepared using molybdenum-filled MPCM resin, MPCM resin was combined with sodium chlorite (NaClO ₂ ) and sodium hypochlorite. Oxidized using (NaOCl) respectively. The concentration and oxidation time of sodium chlorite or sodium hypochlorite in the solution was determined based on trial and error. The concentration of sodium chlorite and the pH of the solution were changed to 1 mmol / L to 10 mmol / L and 3 to 11, respectively. Oxidation of MPCM with either sodium chlorite or sodium hypochlorite was performed at a solid-liquid ratio of 1: 100. The oxidation time was varied from 30 minutes to 24 hours. For both sodium chlorite and sodium hypochlorite, a solution containing about 0.02% chlorine, calculated as Cl _{2 in the} pH range of 3 to 4.5, and the oxidation time of 2 hours is the maximum of molybdenum. It was sufficient to partially oxidize MPCM to promote the uptake of and to promote the release of technetium from the MPCM adsorbent. MPCM resins partially oxidized by sodium chlorite and sodium hypochlorite are referred to herein as MPCM-ClO ₂ and MPCM-OCl, respectively. The performance of MPCM-ClO ₂ and MPCM-OCl was evaluated for molybdenum adsorption from aqueous solutions using a batch technique. It is observed that oxidized MPCM can adsorb approximately 6.25 mM (about 600 mg) of Mo (VI) per gram of oxidized MPCM at 298 K when the equilibrium concentration Mo (VI) in the solution is 54 mmol / L at pH 3.0. It was.

Surface charge analysis of molybdenum filled non-oxidized MPCM and molybdenum filled MPCM-OCl ₂ was performed using the technique described above. Similar surface charge experiments were also performed on molybdenum filled MPCM-OCl to compare the data with the surface charge of molybdenum filled non-oxidized MPCM resin. The surface charge data for molybdenum filled MPCM-ClO ₂ and MPCM-OCl show a similar pattern to the surface charge data for molybdenum filled MPCM oxidized by potassium permanganate.

In order to assess the uptake capacity of Tc-99, two different columns were prepared using molybdenum packed MPCM-ClO ₂ and MPCM-OCl, respectively. For comparison, Tc-99 passage tests for both of these oxidized MPCM resins were performed according to the technique described above. The results confirmed that pertechnetate (TcO ₄ ⁻ ) did not adsorb to either MPCM-ClO ₂ or MPCM-OCl filled with Mo (VI). Table 7 shows a comparison of the effect of various oxidants on technetium release from columns prepared with oxidized MPCM. The oxidized MPCM resin shown in Table 7 was exposed to a 1% molybdenum solution supplemented with molybdenum-99. The activity of molybdenum-99 was varied from 45 mCi to 1.39 Ci (at the end of irradiation or EOI), respectively. Each chromatography column was prepared using molybdenum packed MPCM resin oxidized with various oxidizing agents. Next, a saline solution was passed through the column and the data are shown in Table 7.

Technetium release from the column was almost 100% when the initial activity of Mo-99 in the column was approximately 45 mCi (Table 7). The release of technetium from the column was relatively very low for all oxidants when higher specific activity Mo-99 was used in the column. While not wishing to be bound by theory, at higher activities, technetium is reduced from Tc (VII) to Tc (IV), and the reduced anionic pertechnetate is probably the free surface site of MPCM resin. It is thought that a covalent bond was formed. When molybdenum-99 with an activity of 900 mCi was loaded into an MPCM sample oxidized with 31 mM potassium permanganate, the technetium release from the column was approximately 10% (Table 7). This combination also released more manganese in the eluate compared to MPCM resin oxidized with 6.3 mM potassium permanganate. When the activity of Mo-99 in the column is higher (1.39 Ci in EOI), the column for MPCM-ClO ₂ and MPCM-OC resins compared to resins oxidized by potassium permanganate or hydrogen peroxide It was observed that the increase in the proportion of technetium released from was small (Table 7).

  When the specific activity of molybdenum in the column (1.39 Ci in EOI) is higher, the release of technetium from the column is significantly higher compared to the column prepared by MPCM resin packed with lower specific activity molybdenum-99 Reduced. While not wishing to be bound by theory, it is believed that if the activity is higher, the oxidation state of the metal ions present in the column may change, thus reducing technetium release from the column. It is believed that if an oxidant is present in the molybdenum solution, the MPCM resin and molybdenum in the solution can be maintained in an oxidized state throughout the adsorption cycle, thereby facilitating the release of technetium from the column. In addition, the addition of an oxidizing agent in the eluted saline solution was also investigated to enhance the release of further technetium-99 from the oxidized MPCM column packed with molybdenum.

MPCM-ClO ₂ and MPCM-OCl resins were further investigated to evaluate the ability of molybdenum to adsorb in the presence of various concentrations of oxidant in solution. The adsorption test uses various concentrations of sodium chlorite and sodium hypochlorite (5mM to 50mM) supplemented with 1% molybdenum solution (prepared from molybdenum salt, free of radioactive molybdenum (Mo-99)) And went for 24 hours. The pH of the molybdenum solution was initially adjusted to about 3.0 for all experiments. Samples were taken at various intervals and analyzed for molybdenum incorporation into the resin. Table 8 shows that when sodium chlorite or sodium hypochlorite is present in the solution, the molybdenum uptake capacity of the oxidized MPCM resin is between 5.21 mM (500 mg / g) to 6.25 mM (600 mg / g) of oxidized MPCM. ). Molybdenum began to precipitate gradually in the solution after 12 hours of exposure when the oxidant concentration in the solution was 45 mM or greater than 45 mM. No molybdenum precipitation in the solution was observed in solutions in which the concentration of either sodium chlorite or sodium hypochlorite was in the range of 5 mM to 40 mM. Molybdenum did not precipitate in solution during the first 4 hours of exposure for any concentration of sodium hypochlorite used in this study.

The incorporation of molybdenum into MPCM-ClO ₂ was found to be fairly consistent in the presence of all concentrations of sodium hypochlorite in a 1% molybdenum solution (Table 8). Compared to the data obtained from the molybdenum solution without oxidizer, the incorporation of molybdenum into MPCM-ClO ₂ from a 1% molybdenum solution containing 25 mM sodium hypochlorite (NaOCl) in solution was approximately 6 25 mM / g (Table 8). This suggests that the presence of hypochlorite in the molybdenum solution did not substantially affect molybdenum adsorption on MPCM resin partially oxidized by sodium chlorite.

Therefore, in this attempt to adsorb molybdenum in 1% Mo solution in the presence of various concentrations of sodium hypochlorite (NaOCl) as oxidant, MPCM-ClO ₂ was investigated. Next, using the molybdenum filling MPCM-ClO _2, to prepare a chromatography column. To investigate the oxidative effect on the release of both technetium and molybdenum from the column, sodium chlorite and sodium hypochlorite were also mixed with the saline solution. Next, a saline solution in which 5 mM sodium chlorite and sodium hypochlorite were mixed at pH 4 was flowed through the column. To the eluate mixture was further added Tc-99 (stoichiometrically equal to about 1 Ci Tc-99 per 10 mL) and then passed through the column.

More than 99% of Tc-99 passed through the column in the presence of either sodium chlorite or sodium hypochlorite as oxidant in the eluate without adsorbing to the column (Table 9). . Release of molybdenum from the column upon elution with saline solution mixed with sodium hypochlorite was similar to the column eluted with saline solution mixed with sodium chlorite (Table 9). As an example, 5 mM sodium chlorite and sodium hypochlorite were passed through columns prepared by MPCM-ClO ₂ adsorbed with molybdenum from a solution containing 1% molybdenum and 25 mM sodium hypochlorite, respectively (Table 9). ). For saline containing sodium chlorite, the release of molybdenum was found to be approximately 2% of the 6.25 mM adsorbed molybdenum to MPCM-ClO ₂ used to prepare the column. From a similar column eluted with sodium hypochlorite mixed saline solution as shown in 9, the molybdenum release was found to be approximately 7.5%. It was clear from this study that MPCM-ClO ₂ can adsorb approximately 6.25 mM molybdenum from a solution containing 1% molybdenum and 25 mM sodium hypochlorite. In the case of a chromatographic column prepared using molybdenum filling MPCM-ClO _2, eluting with Tc-99 added saline mixed with sodium chlorite, the system can hold a maximum molybdenum And it has been found that maximum Tc-99 can be released from the column.

The effect of different sodium chlorite concentrations in the eluate to release molybdenum and technetium from the column was further investigated. A column was prepared by MPCM-ClO ₂ adsorbed with molybdenum from a solution containing 1% molybdenum and 25 mM sodium hypochlorite. Next, a saline solution mixed with various concentrations of sodium chlorite was passed through the column (Table 10). The concentration of sodium chlorite in saline was in the range of 5 mM to 20 mM. To the elution mixture was further added Tc-99 (stoichiometrically equal to about 1 Ci of Tc-99m per 10 mL) and then passed through the column. In the presence of sodium chlorite as the oxidizing agent (5-20 mM concentration) in the eluate, over 99% of technetium-99 was observed to pass through the column without being adsorbed on the column ( Table 10). The amount of molybdenum released from the column was approximately 2% and 5% of the molybdenum present in the column when the sodium chlorite concentration in the saline solution was 5 mM and 20 mM, respectively. This suggests that a guard column is desirable to obtain technetium that does not contain molybdenum in the elution solution.

[Example 6]
Neutron capture with activity of 13.9 mCi / mL irradiated with MURR (the University of Missouri Research Reactor, USA) the potential of MPCM-ClO ₂ resin as an adsorbent for the preparation of ⁹⁹ Mo / ^99m Tc generator The resin was evaluated by exposing the resin to a 1% molybdenum solution produced by Similar experiments were also performed with POLATOM using a 1% natural molybdenum solution supplemented with fission molybdenum (approximately 1.89 Ci ⁹⁹ Mo / g Mo). Batch adsorption experiments for molybdenum incorporation into MPCM-ClO ₂ resin were performed at room temperature, and the solution pH for both experiments was initially about 3.0. For both experiments, the molybdenum incorporation into the resin was approximately 60% of the molybdenum available in solution. In each experiment, a ⁹⁹ Mo / ^99m Tc generator consisting of a 6 mL column containing MPCM-ClO ₂ resin packed with ⁹⁹ Mo was prepared. ^99m Tc, which is a decay product of ⁹⁹ Mo, was eluted with a saline solution (0.9% NaCl) mixed with sodium chlorite as an oxidizing agent. Table 11 shows the elution performance of a typical generator prepared by exposing 1 g of MPCM-ClO ₂ resin to 100 mL of about 1% total molybdenum solution of 1.39 Ci ⁹⁹ Mo at an initial pH of about 2.8. . Analysis of the activity distribution showed that the Mo adsorption efficiency was 63.4%. The time to expose the MPCM-ClO ₂ resin to the molybdenum solution was 24 hours for these experiments. After the adsorption cycle, the resin was thoroughly rinsed with deionized water to remove any adhered molybdenum from the surface.

  From Table 11, the amount of Tc-99m released from the column increases as the concentration of sodium chlorite in the elution solution increases. A sodium chlorite concentration of approximately 20 mM in an eluted saline solution at pH 4.0 appears to be sufficient to remove more than 95% of Tc-99m from the column when the initial activity of the column is approximately 1 Ci. It seems to be.

The Tc-99m radioisotope in the form of an intermediate solution is passed through a guard column having alumina as an adsorbent. Elution data was collected for 3 consecutive days and the data revealed that the eluate contained a yield of> 90% (> 90%) of the theoretical amount of ^99m Tc available from the generator. ⁹⁹ Mo in the eluate was less than ⁹⁹ Mo 0.15 μCi per ^{99 m} Tc per mCi. The elution solution was further subjected to treatment with either 1M sodium thiosulfate or sodium sulfite to neutralize the presence of oxidant in the solution. By using sodium sulfite, the oxidant that may be present in the final eluate can be efficiently neutralized. Table 12 shows the typical composition of eluates obtained from these experiments.

[Example 7]
The addition of potassium dichromate (about 200 mg chromate) and 5% cerium oxide as an oxidant in the saline solution used to flow through the molybdenum packed MPCM-ClO ₂ column also gained some success. It was. When potassium dichromate or cerium oxide in saline was used as eluent, Tc-99 release from columns prepared with molybdenum-filled MPCM-ClO ₂ resin was approximately over 75% (> 75%). A substantial amount of chromium or cerium is present in the final eluate, which indicates that a further guard column unit is required to obtain technetium without oxidizing agent in the final eluate.

[Example 8]
The effect of temperature and solid-liquid ratio in the presence of an oxidizing agent (sodium hypochlorite) in solution on the incorporation of molybdenum into MPCM-ClO ₂ resin was investigated. Batch testing was performed at various predetermined temperatures according to the techniques already mentioned. For each experiment, approximately 1 gram of MPCM-ClO ₂ resin was exposed to 100 mL of 1% molybdenum solution at pH about 3.0 for 4 hours in the presence of oxidizing agent (25 mM NaOCl) (data not shown). Preliminary data shown in FIG. 21, 25 ℃ (298K) ~70 ℃ solution temperature in the range of (343 K), incorporation of molybdenum to MPCM-ClO ₂ resin is changed only slightly (MPCM-ClO ₂ resin Mo (VI) in the range of 5.38 mM to 5.53 mM per gram). In most cases, during the first 0.5 hour of operation, approximately 50% of the available molybdenum in the solution is adsorbed to the MPCM-ClO ₂ resin without any precipitation and then slowly moves towards equilibrium. did.

  The heat of adsorption at various loadings of molybdenum in oxidized MPCM is shown in FIG. The heat of adsorption of molybdenum decreased with increasing loading, which can be attributed to surface non-uniformity and multilayer coverage. The heat of adsorption approached the integrated heat of adsorption (ΔH value) at higher loadings. Without wishing to be bound by any theory, it is believed that the surface is saturated with molybdenum and the heat of adsorption is reaching its equilibrium value. The initial decrease in the value of heat of adsorption can be attributed to surface non-uniformity and multilayer coverage. Subsequent increases in heat of adsorption can be attributed to lateral interactions between adsorbed molybdenum ions that are known to form complex molecules at the solid surface. It was expected that the adsorption surface area of the resin would be energetically uniform and therefore a constant heat of adsorption should be obtained. However, the resin surface appears to be energetically non-uniform due to the microporosity of the surface.

A batch test was conducted by changing the solid-liquid ratio at 25 ° C. (298 K) in the presence of 25 mM sodium hypochlorite as an oxidizing agent in a 1% molybdenum solution. When the solid-liquid ratio is 2: 100 (2 grams of MPCM-ClO _{2 in} 100 mL of 1% molybdenum solution mixed with 25 mM sodium hypochlorite), almost 95% of the molybdenum available from the 1% solution is exposed. It was adsorbed on MPCM-ClO ₂ resin within 1.0 hour. This ratio has been found to be the optimal adsorbent dose for molybdenum incorporation into MPCM-ClO ₂ in the presence of 25 mM sodium hypochlorite in a 1% molybdenum solution. For non-oxidized MPCM, using the same solid-liquid ratio and exposure time, molybdenum uptake was almost 35% less compared to oxidized MPCM (MPCM-ClO ₂ ) resin. The modification of the surface charge of MPCM by oxidation and the higher solid-liquid ratio in the process appears to be at least part of the reason for this phenomenon.

[Example 9]
Initial experimental data showed that oxidized MPCM resin can adsorb approximately 50-60% of the available molybdenum from solution after 24 hours of exposure. Moreover, almost 28% of ^{99 Mo} activity was estimated to disintegrate during the 24-hour adsorption cycle. Furthermore, ⁹⁹ Mo activity was further lost by 10-15% due to generator processing and handling. FIG. 23 shows that the above 0.5 Ci (at elution time) ⁹⁹ Mo / ^99m Tc generator experimental data typically requires approximately 1.6 to 1.8 Ci of ⁹⁹ Mo (EOI) from the very beginning. It is shown that.

However, from a batch experiment, using a solid / liquid ratio of 2: 100 at a temperature of 25 ° C. (298 K), MPCM-ClO ₂ resin was obtained from a 1% molybdenum solution mixed with 25 mM sodium hypochlorite within 1 hour of exposure. It has been suggested that nearly 99% of the available molybdenum can be adsorbed. After thorough rinsing of the molybdenum-filled MPCM-ClO ₂ resin using deionized water, it was found that at least 90% (or up to 95%) of the molybdenum was retained on the resin and was used A generator column was prepared. This ultimately reduces the decrease in ⁹⁹ Mo activity during the adsorption cycle and during generator processing and handling. Considering the ⁹⁹ Mo reduction during the 24 hours of the adsorption cycle to prepare a 6 mL generator column with an activity of 0.5 Ci (on elution), the solution was solid at 25 ° C (298 K) solution temperature during the adsorption cycle. If the liquid ratio is maintained at 2: 100, it is expected that a generator with a specific activity of 1.5 Ci to 2 Ci will be possible (Figure 23). It is also estimated that by adjusting the capacity and number of columns in the system, a ⁹⁹ Mo / ^99m Tc generator with a specific activity of 4-6 Ci based on neutron capture ⁹⁹ Mo is possible.

[Example 10]
About 4 g of chitosan was added to 300 mL of deionized (DI) water containing 1 mL of acetic acid and stirred at 70 ° C. for 2 hours to form a gel. About 4 mL of HCl was added to the chitosan gel and stirred continuously at 70 ° C. for an additional hour.

In this example, an amorphous titania gel was prepared by acid-catalyzed controlled hydrolysis and condensation of titanium isopropoxide. Hasan, S .; , Ghosh, T .; K. Prelas, M .; A. Viswanath, D .; S. , And Boddu, V. M.M. “Adsorption of uranium on a novel biosorbent chitosan coated perlite” Nuclear Technology, 159, 59-71, 2007; Schattka, J. et al. H. Wong, E .; H. -M. , Antonietti, M .; , And Caruso, R .; A. “Sol-gel templating of membranes to form thick, porous titania, titania / zirconia and titania / silica films, Journal of Materials Chem. , And Benkacem, T .; See “Synthesis of porous titanium dioxide membranes” Desalination, 206, 531-537, 2007. Equal amounts of isopropanol (IP) and DI water were mixed in a predetermined amount of titanium isopropoxide with continuous stirring at 70 ° C. HCl was added dropwise with continuous stirring and heating at 70 ° C., producing a clear solution. The hydrolysis and condensation reactions were controlled by the ratio of water and titanium, respectively, and the ratio of H ⁺ and titanium in the mixture. The final pH of the mixture was approximately 2.0 and the final reaction stoichiometry was Ti: IP: H ₂ O: Η ⁺ = 0.0132: 0.39: 1.67: 0.01. Based on the reactant concentration ratio, the gel time varied from 25 to 45 minutes.

  The amorphous titania sol-gel solution was mixed with the chitosan gel for about 75% of the total gel time. The mixture was maintained at 70 ° C. with stirring for an additional hour to allow complete reaction of chitosan and amorphous titanium oxide. The reaction with glutaraldehyde was carried out by adding dropwise about 6 mL of a glutaraldehyde solution having a concentration of 50% to an acidic chitosan titania gel with continuous stirring at 70 ° C. The pH of the final mixture was approximately 1.0. The mixture was maintained at 70 ° C. for an additional hour with continuous vigorous stirring to give a semi-solid gel.

  The resulting mass was thoroughly washed with 2% monoethanolamine to remove any unreacted glutaraldehyde. The mass was then suspended in 0.1 M NaOH solution for 4-6 hours. The crosslinked mass was separated from the solution, washed with 0.1 M HCl, and then washed with deionized (DI) water until the pH of the wash was 7. The crosslinked mass was then dried overnight at 70 ° C. in a vacuum oven. The cross-linked chitosan glutaraldehyde complex prepared in this process is referred to herein as “CGST”.

For the CGST sample, the peak at 1590 cm ⁻¹ was found to be weak, indicating that the amide group may be involved in the cross-linking reaction with titanium. A carbonyl (—CONHR) spectrum near 1650 cm ⁻¹ is observed for all three samples. For primary aromatic amines, the CN stretching vibration is in the range of 1350-1150 cm ⁻¹ .

A peak is observed at 1170 cm ⁻¹ (FIG. 21) for the chitosan and CGST samples, respectively. Compared to chitosan, the peak at 1170cm ^-1 respect CGST sample was found to be weaker, a new peak appears at 1090 cm ^-1.

The peak appearing at 1090 cm ⁻¹ shows a significant shift due to the C═O stretching vibration of the ether bond.

In the area of 1000cm ^-1 ~1200cm ^-1, chitosan, 1157cm ^-1 and 1070 cm ^-1 in showed two peaks, stretching (secondary OH) of each C3 C-O bonds of chitosan and C C6 chitosan Corresponds to -O expansion (first grade OH).

Compared to the C—O spectrum of chitosan obtained at 1070 cm ⁻¹ , the secondary hydroxyl group absorption peak of the CGST sample is folded as shown in FIG. Shifting from 0 to 3450.0 cm ⁻¹ , this suggests that the OH group of chitosan may be involved in the reaction with glutaraldehyde through the formation of hemiacetal in the presence of an acid catalyst. Evidence for a decrease in the chemical bond constant of C—O and a significant decrease in the OH stretching peak intensity OH (1000-1200 cm ⁻¹ ) is the result of glutaraldehyde and surface oxygen functional groups such as secondary hydroxyl groups in chitosan. Supports the existence of complex formation reactions. In the case of CGST samples, titanium oxide appears to be involved in the reaction with chitosan amine groups (FIG. 24).

Various embodiments of chitosan-based microporous composite (MPCM) were prepared by crosslinking glutaraldehyde at 70 ° C. in the presence of a catalyst. MPCM was prepared in the laboratory via phase transformation of a liquid slurry of chitosan dissolved in acetic acid and aldol condensation of glutaraldehyde so that the amine groups (NH ₂ ) were better exposed. Characterization of MPCM by scanning electron microscopy (SEM) revealed its porous nature. Two MPCM based derivatives were also prepared, such as oxidized MPCM and acid catalyzed MPCM. The MPCM stabilization test was performed at 50,000 krad using a ⁶⁰ Co irradiator as the gamma ray source. FTIR, XPS, and EDS X-ray microanalysis spectra revealed that the C, O, N peak intensities of MPCM did not change substantially after irradiation. In the case of Mo (VI) adsorption from an aqueous solution at 298K, MPCM can hold up to 60% of its body weight. MPCM and its derivatives prove to have ⁹⁹ Mo adsorption capacity and daughter product ^99m Tc simultaneous release capacity in both batch and equilibrium conditions. It was also observed that ^99m Tc, a decay product of ⁹⁹ Mo, was eluted with a normal (0.9%) saline solution, resulting in an elution exceeding 80%. The data show that the high elution yield of ^99m Tc and the leakage of Mo (VI) from the continuous column was minimal, so MPCM and its derivatives did not use ⁹⁹ g Tc without using any guard column. / ⁹⁹ Can be used as adsorbent in Mo generator.

  As used herein, the terms “near”, “approximately” and “about” in relation to a numerical value mean that some variation of the numerical value up to ± 10% can occur from the numerical value. Unless the terms “a”, “an”, “the”, etc. clearly indicate otherwise, the presence of a singular includes the presence of a plurality Means it should be understood.

A ⁹⁹ Mo / ^99m Tc generator based on molybdenum produced by low specific neutron capture has been prepared using novel MPCM resin as an adsorbent. Oxidized MPCM resin is found to be able to adsorb more than 95% (> 95%) of the available molybdenum from a 1% solution at a solution pH of 3.0 when the solid-liquid ratio is 2: 100. Nearly 90% of the available ^99m Tc was eluted from the generator primarily with saline solution (0.9% NaCl). The leakage of ⁹⁹ Mo and the pH of the eluate that passed through the alumina guard column are within the limits of the United States Pharmacopeia (USP) and the European Union Pharmacopeia (EUP).

  Although the invention has been described with reference to certain specific embodiments and examples, it will be understood that they are illustrative and do not limit the scope of the appended claims.

Claims (24)

Chitosan crosslinked with glutaraldehyde in the presence of a catalyst at a glutaraldehyde concentration of about 2 to about 4% by weight, comprising chitosan that is resistant to degradation by exposure to beta and gamma radiation and exposure to acids An adsorbent comprising a microporous material,
The adsorbent is at least partially oxidized after crosslinking with an oxidant selected from the group consisting of chlorite, hypochlorite, dichromate, and metal oxides. The adsorbent according to claim 1, wherein the selectivity for ⁹⁹ Mo adsorption is increased compared to ^99m Tc.   The adsorbent of claim 1, wherein the oxidant is selected from the group consisting of alkali metal chlorites, alkali metal hypochlorites, alkali metal dichromates, and transition metal oxides.   The adsorbent of claim 3, wherein the oxidant is selected from the group consisting of sodium chlorite, sodium hypochlorite, potassium dichromate, and cerium oxide.   The adsorbent of claim 4, wherein the oxidant is selected from the group consisting of sodium chlorite and sodium hypochlorite.   The adsorbent according to claim 3, wherein the surface charge of the adsorbent when filled with Mo (VI) is approximately zero at pH 3-4. The adsorbent according to claim 1, wherein the adsorbent has a surface area in the range of 10 to 100 m ² / g. The adsorbent of claim 7, wherein the adsorbent has a surface area of about 25 m ² / g.   The adsorbent of claim 1, wherein the zero charge point of the adsorbent ranges from about 7.5 to about 8.8.   The adsorbent of claim 1 having a molybdenum retention capacity of 5.4 to 6.25 mmol molybdenum per gram of adsorbent. A method for preparing a radiation resistant adsorbent comprising:
Mixing chitosan with water in the presence of acid to form a chitosan gel;
Adding glutaraldehyde to the chitosan gel in the presence of a catalyst at 70 ° C. where condensation polymerization of the reaction mass takes place to form a semi-solid mass;
Washing the semi-solid mass to remove unreacted glutaraldehyde to form a washed mass;
Suspending the washed mass in an aqueous base to form a neutralized crosslinked mass;
Drying the neutralized crosslinked mass to form the radiation resistant adsorbent; and selected from the group consisting of chlorite, hypochlorite, dichromate, or metal oxide Oxidizing the radiation resistant adsorbent with an oxidizing agent,
Including a method.   12. The method of claim 11, wherein the oxidant is selected from the group consisting of alkali metal chlorites, alkali metal hypochlorites, alkali metal dichromates, and transition metal oxides.   13. The method of claim 12, wherein the oxidizing comprises adding the oxidizing agent to the radiation resistant adsorbent at a pH between about 3 and about 11.   13. The method of claim 12, wherein the oxidizing comprises contacting the oxidant with the radiation resistant adsorbent for an exposure time of about 30 minutes to about 24 hours.   13. The concentration of the oxidant is in the range of about 1 mM / L to about 10 mM / L, or the solid / liquid ratio is about 1: 100 to 2: 100, or both. The method described. A method for separating isotopes from a mixture thereof;
Contacting the radiation-resistant adsorbent of claim 1 with preferential adsorption of at least one of the isotopes to a mixture of at least two isotopes:
Adsorbing at least one of the isotopes on or in the adsorbent, with one or more of the remaining isotopes not significantly adsorbed by the adsorbent;
Removing the one or more remaining isotopes from the adsorbent. The method of claim 16, wherein the at least two isotopes comprise ⁹⁹ Mo and ^99m Tc. The method of claim 17, wherein the adsorbent preferentially adsorbs the ⁹⁹ Mo and the ^99m Tc is not significantly adsorbed by the adsorbent.   The method of claim 16, wherein one of the isotopes is a cesium isotope.   The method of claim 19, wherein the one or more remaining isotopes comprise one or more isotopes present in a radioactive wastewater stream.   17. The method of claim 16, wherein removing one or more remaining isotopes from the adsorbent comprises contacting an elution solution with the adsorbent.   The method of claim 21, wherein the elution solution comprises one or more oxidants selected from the group consisting of chlorite, hypochlorite, dichromate, and metal oxides. A generator of ⁹⁹ Mo / ^99m Tc comprising the adsorbent according to claim 1.   A method of separating, concentrating, or both of one or more heavy metals from a liquid stream, wherein the adsorbent of claim 1 is contacted with the liquid stream comprising the one or more heavy metals. And adsorbing one or more of said heavy metals thereon.