WO2019190791A1 - Preparation of chitosan-based microporous composite material and its applications - Google Patents

Abstract

Microporous glutaraldehyde/crosslinked chitosan sorbents include a plurality of nanoparticles of a high Z element. The nanoparticles are disposed in the cross-linked chitosan-gluteraldehyde composite matrix and integrated with the cross-linked chitosan-gluteraldehyde composite matrix to reduce primary impact of high radiation flux and minimize radiolytic effect on said cross-linked chitosan-gluteraldehyde composite matrix. The plurality of nanoparticles is made from the high Z element such as hafnium (Hf). Methods of making and using the microporous glutaraldehyde/crosslinked chitosan sorbents, and a generator for the radioisotope ⁹⁹Mo containing the sorbents.

Description

PREPARATION OF CHITOSAN-BASED MICROPOROUS

COMPOSITE MATERIAL AND ITS APPLICATIONS

CROSS REFERENCING TO RELATED APPLICATION

|0OOI] This application claims the benefit of and priority to U.S. CSP Patent

Application 15/935,398, filed March 26, 2018, the entire contents of which is incorporated herein by reference for all purposes,

BACKGROUND L Field

fSM)82J Disclosed herein are methods for modification of chitosan that increases their versatility as sorbents, particularly as sorbents of radioisotopes, as well the ability of these materials to function in environments where radioactivity is present. Also disclosed are the materials themselves, as well as methods of using them to separate and purify· radioisotopes, and to separate and purify contaminated materials, in particular those radioactive and nonradioaetive streams contaminated by metal ions, particularly those of heavy metals,

2, Description of Related Art

|0dt 3| Radioactive isotopes are widely used, particularly in the field of nuclear medicine, both for therapy and imaging. However, these materials can present production, storage, and disposal challenges due to their radioactivity, as vveii as their often significant half-lives,

[00©4] More particularly, in the radiopharmaceutical area, ^w¾Te (having a half-life n ^™ 6h), is one of the most widely used radioisotopes in diagnostic medicine, obtained from the decay product of parent "Mo ft:.;· 66 h).

is a pure gamma emitter

(0, 143 MeV) ideal for use in medical applications due to its short half-life (6 hours). It is used n §0-85% of the approximately 25 million diagnostic nuclear medicine procedures performed each year.

[SMS] The parent ^wMo can be produced by the irradiation of ⁹⁸ Mo with thermal/epithermal neutrons in a nuclear reactor, but much of the world supply of "Mo comes from the fission product of highly enriched uranium (HEU) in a reactor. The HEU process generates large quantities of radioactive waste and does not permit reprocessing of the unused uranium targets due to weapons prol feration concerns,

[0006] Low enriched uranium (LEU, 20 percent ^SU or less) could be used as a substitute, but would yield large volumes of waste due to the large quantities of un-useahle ^23SU present. Currently, most of the world supply of "Mo comes from sources outside of the United States, Recent "Mo production outages at these sources have disrupted medical procedures and have demonstrated the unreliability of this supply chain. This stresses the need for economically feasible alternative sources to produce ^95mTe from "Mo.

[0007] The main concerns with neutron capture-produced ^wMo, as compared to the more common fission-produced material described above, involves both lower curie yield and Sower specific activity, The specific activity is significantly lower and is of great concern due to impacts on " G/^TC generator size, efficiency, and functionality. Therefore, use of lower specific activity molybdate is only feasible with a more efficient sorbent to reduce the generator size and to yield a usabie dose at the ra iopharmaey. Several research works have been focused ors the uses of a molybdenum gel generator. See Marageh, M.G., el a!., ’’industrial-scale production of ^99mTc generators for clinical use based on zirconium molybdate gel," Nuclear Technology, 269, 279-284 (2010); Morsoroy-Guzman, F, et aL, ^l,99Mo/"^mTe generators performances prepared from zirconium molybdate gels'^{* j}, Braz. Clte . Soc., 19, 3, 3SQ-3S8 (2008), Others focused ors preparation of ⁹⁹Mo/"^mTc generator based on polymeric or inorganic oxide as an adsorbent material for "Mo, See y Masakazu, T. el al,₅ ^" A generator using a new organic polymer absorbent for (h,g)

"Mo,ⁿ AppL Radla, Isot., 48, 5, 607·?! 1 (1997); Qazi, Q,M. et ai., '"Preparation and evaluation of hydrous titanium oxide as a high affinity adsorbent for molybdenum ("Mo) and its potential for use i " Tc generator," Radiochim. Acta, 99, 231-235 (201 1),

|000§| However, such medical uses require that the "^f,rfe he produced in highly purified form, For example, when "^mTc is produced from the decay of "Mo, it is important to achieve a high degree of separation of the two elements in order to meet regulatory requirements,

|O0Q9] One approach to achieving this level of purity is to separate ¾^Tc from

"Mo using a highly efficient, selective sorbent, e,g, by sorbing "Mo and eluting "^mTc, Attempts have been made to use alumina as such a sorbent. However, this alumina provides an efficiency for Mo" of about 25 ntg/g of sorbent. Accordingly, there remains a need in the art for a sorbent that is both efficient in the adsorption of "Mo, and resistant to the adverse effects of ionizing radiation. In addition, there remains a need for a sorbent that is highly selective for "Mo, he,, that is capable of sorbing "Mo while providing good release off^Te.

[0010] More generally, there remains a need for a sorbent that is readily available, or producible from readily available materials, and that is customizable by modification to have one or more functional groups (which may be the same or different) allowing the material to remove constituents from a process stream requiring such purification, and that is resistant to degradation by ionizing radiation,

|IHH 1| The ion exchange process, which has been used for decades to separate metal ions from aqueous solution, is often compared to adsorption. The primary' difference between these two processes is that ion exchange is a stoichiometric process involving electrostatic forces within a solid matrix, whereas in adsorptive separation, uptake of the solute onto the solid surface involves both electrostatic and Van der Waais forces, In an

atempt to Had a suitable ion exchange resin for the remove! of cesium and strontium from waste solution, several Investigators have tried a number of inorganic, organic, and bioadsorbents, with a varying degree of success. See Gu, D., Nguyen, L, Philip, C.V., Huekmen, M.E., and Anthony, R,G.“Cs ion exchange kinetics in complex electrolyte solutions using hydrous crystalline sHicotitanafes’k Ind, Eng. Chem, Res., 36, 5377-5383. 1997; Pawaskar, C.S., Mohapatra, P.K., and anchanda, V.K. “Extraction of actinides fission products from sail soiutions using polyethylene glycols (PEGs)” Journal of Radioanalytical and Nuclear Chemistry, 242 (3), 627-634, 1999; Dozol, J.F., Simon, N., Lamare, V,, et ah“A solution for cesium removal from high salinity acidic or alkaline liquid waste: The Crown ealyx[4]arenas” Sep. Sch Technol., 34 (6&7), 877-909, 1999; Arena, G,, Cont o, A,, Margi, A. et al.“Strategies based on ca! crowns for the detection and removal of cesium ions from alkali- containing solutions. Ind. Eng, Chem. Res,, 39, 3605-3610, 2000, (00121 However, major disadvantages with the ion exchange process are the cost of the materia! and regeneration for repeated use when treating radioactive streams. See Hassan, R,Adu-Wusu, K., and Marra, J.C.“Resorcinol-formaldehyde adsorption of cesium (Cs+) from Hanford waste solutions-Part S: Batch equilibrium study” WSRC-MS-2GG4. The cost of disposal is also a major issue. The success of adsorption processes depends largely on the cost and capacity of the adsorbents and the ease of regeneration.

|tM>!3| Chhosan is a partially acety Sated glucosamine polymer encountered in the cell wails of fungi, it results from the deacetylation of chitin, which is a major component of crustacean shells and available in abundance in nature. This biopolymer is very effective in adsorbing metal ions because of its ability' for complexation due to high content of amino and hydroxyl functional groups, in their natural form, chhosan is soft and has a tendency to agglomerate or form gels in acidic medium. Moreover, chitosan, in its natural form, is non-porous and the specific binding sites of this biopolymer arc not readily available for sorption. However, it is necessary to provide physical support and chemical modification to increase the accessibility of the metal binding sites for process applications. It is also essential that the metal binding functional group should be retained after any such modification.

|00!4J ft is well known that polysaccharides can be degraded due to scission of glycoside bonds by ionising radiation 1AEA-TECDGC-1422,“Radiation processing of polysaccharides’ International Atomic Energy Agency, November, 2004 The hydrogel based on polysaccharides and their derivatives has been extensively studied, but very limited work has been reported so far on the Impact of radiation on the chitosan-based mscroporous composite materials and their metal ion uptake capacity.

}001S| Chitosan is a non-toxic, biodegradable material. it has been investigated for many new applications because of its availability, poiycationic character, membrane effect, etc. The amino group present in the chitosan structure is the active metal binding site, but It also renders chitosan soluble in weak add. In addle media, chitosan tends to form a gel which is not suitable for adsorption of metal ions in a continuous process.

(03P6] Several reports indicated that the cross-linking of chitosan with giuteraldehyde make chitosan acid or alkali resistant. See Elwakeel, K.Z., Atia, A.A., and Donia, A.M.“ Removal of Mo(VI) as oxoanlons from aqueous solutions using chemically modified magnetic chitosan resins. Hydrometallurgy, 97, 21-28, 2009; Chassary, P , Vincent. T , and Guibal, E.“ Metal anion sorption on chitosan and derivative materials: a strategy for polymer modification and optimum use” Reactive and Functional Polymers, 60, 137-149, 2004; Veimurugart, R, Kumar, G.G , Han, S.S., Nahm, K.S., and Lee, Y.S.“Synthesis and characterization of potential fungicidal silver nano-sized particles and chitosan membrane containing silver particles” Iranian Polymer Journal, 18 (5), 383-392, 2009. Giiiteraidehyde is a five carbon molecule terminated at both ends by aldehyde groups which are soluble in water and alcohol, as well as in organic solvents. It reacts rapidly with amine groups of chitosan daring cross-linking through Schiffs reaction and generates thermally and chemically stable cross-links. See Migneault, L, Dartiguenave, C., Bertrand, MJ., and Waldron, &,€. "Gluteraidehyde; behavior in aqueous solution, reaction with proteins, and application to enzyme crossiinking" Bio Techniques, 37 (5), 79G-802, 2004. The amine groups are also considered as the active metal binding sites of ehhosan. Therefore, by cross- linking with gluteraidehyde, the ehhosan is reported to be add or alkali resistant but the metal adsorption capacity will be reduced,

[OCn 7] Li and Bai (2005) proposed a method to cap the amine group of ehhosan by formaldehyde treatment before cross-linking with gluteraidehyde, which was then removed from the ehhosan structure by washing thoroughly with 0.5M MCI solution, Li, Nan, and Bai, R.“ A novel amine-shielded surface cross-linking of ehhosan hydrogel beads for enhanced metal adsorption performance" Ind Eng. Chem Res., 44, 6692-6700, 2005.

|0018] Crosslinking of ehhosan with different functional groups is thought to depend mainly on the crosslinking reaction conditions, such as pH, temperature, ionic concentration, and the surface charge of the materials,

|QQ19| Sing et at. (2006) showed that swelling properties of ehhosan hydrogel cross-linked with formaldehyde depends on the responsive behavior of pH, temperature, and ionic strength. Singh, A , Narvi, S.S., Dutta, P.K., and Pandey, N.D,“External stimuli response on a novel chitosan hydrogel crosslmked with formaldehyde" Bull. Mater SeL, 29 (3), 233-238, 2006.

100201 The surface charge of the chitosan that determines the type of bond that will form between the cross-linking agent and chitosan, depends on the pH of the solution. Hasan, S., Krishnaiah, A., Ghosh, T. ., Viswanath, D.S., Boddu, V.M., and Smith, E. D,“Adsorption of divalent cadmium from aqueous solutions onto chitosan-eoaied perlite beads, ind, Eng, Chem, Res., 45, 5066-5077, 2006. The point of zero charge (FZC) value of pure chitosan is in the pH range of 6.2-6.8. See Hasan, S., Ghosh, T,K„ Viswanath, D.S., Loyalka, S.K., and Sengupta, B,“Preparation and evaluation of fullers earth for removal of cesium from waste streams” Separation Science and Technology, 42 (4), 717-738, 2007. Chitosan is not soluble in alkaline pH, but at acidic pH, the amine groups present in the chitosan can undergo protonation to NiTY or (NHb-HsO)*.

[©6211 Li et al. (2007) reported cross-linked chitosan/poiyvinyl alcohol (PVA) beads with high mechanical strength. They observed that the IT ions in the solution can act as both protection of amino groups of chitosan during the crossiinking reaction, Li, M,, Cheng, S., and Yan, H,“Preparation of cross! inked chitosan/poiy(vln l alcohol) blend beads with high mechanical strength”, Green Chemistry, 9, 894-898, 2007,

[0022] Farris et al, (2010) studied the reaction mechanism for the cross- linking of gelatin with gluteraldehyde, Parris, S,, Song, J., and Huang, Q.“Alternative reaction mechanism for the cross-linking of gelatin with gluteraldehyde” J. Agric. Food Chem., 58, 998-1003, 2010. They suggested that, at higher pH values, the cross-linking reaction is governed by Sehiffs base reaction, whereas at low pH, the reaction may aiso involve -GH groups of hydroxyproilne and hydroxylysine, leading to the formation of hemiacelals.

[0023] Hardy et al. (1969) proposed that, at acidic pH, gluteraldehyde is in equilibrium with its cyclic hemiaceta! and polymers of the cyclic hemiacetal and an increase in temperature produces free aldehyde in acid solution, Hardy, FMVi., Nicholas, A.C., and Rydon, H.N.“The nature of gluteraldehyde in aqueous solution” Journal of the Chemical Society (D), 565-566. 1969, (0024] Several studies focused on ehitosan-based cross-linked material for medical and radiopharmaceutical uses with some success. See, e.g., Hoffman, B,, Seitz, D,, Mencke, A., Kokort, A., and Ziegler, G,“G!uteraldehyde and oxidized dextran as crosslinker reagents for ehitosars-based scaffolds for cartilage tissue engineering” J. Mater Set: Mater Med, 20(7), 1495-1503, 2009; Saimawi, K.M, “Gamma radiation-induced crossiinked PVA/Chitosan blends for wound dressing” Journal of aeromoleeular Science, Part A: Pure and Applied Chemistry, 44, 541-545, 2007; Desai, &, G,, and Park, HJ,“Study of gamma- irradiation effects on chitosan microparticles” Drug Delivery, 13, 39-50, 2006; Silva, R.M,, Sliva, G,A,, Coutinho, O.P., Mano, J.1%, and Reis, R.L.“Preparation and characterization in simulated body conditions of gluteraldehyde crossiinked chitosan membranes” Journal of Material Science: Materials in Medicine, 15 ( 10), 1 105-1 1 12, 2004.

[0025] However, Sabharwal et at. (2004) reported that the radiation processing of natural polymers has drawn less attention as the natural polymers undergo chain scission reaction when exposed to high energy radiation. Sabharwal, S., Varshney, L., Chaudhary, A.D., and Ramnani, S.P. “Radiation processing of natural polymers: Achievements & Trends” Sn Radiation processing of polysaccharides, 29-37, IAEA, November, 2004. it is reported that irradiation of chitosan yields lower viscosity and chain scission of chitosan. See Kurne, T., and Takehisa, M.“Effect of gamma-irradiation on sodium alginate and carrageenan powder” Agrlc. Biol. Che . 47, §89-890, 1982; Uianski, P., and Rosiak, J.M,“Preliminary studies on radiation induced changes in chitosan” Radiat. Phys, Chem. 39(1), 53-57, 1992, The H⁺ and OH radicals formed by radiolysis during irradiation of water accelerate the molecular chain scission of chitosan. The reaction between the above free radical and chitosan molecules leads to rapid degradation of chitosan in aqueous solution. See !AEA-TECDOC-1422, “Radiation processing of polysaccharides’ International Atomic Energy Agency, November, 2004, These studies suggest that the use of a chitosan in environments where it will be exposed to irradiation and potential radioiysis is problematic.

|Q026] Nevertheless, the current demands for biocompatihle polymeric materials in radiopharmaceutical and radioactive waste treatment have increased the interest in developing economically feasible alternative sources of addle, alkaline, and radiation resistant polymer network structures, Recent development of chitosan-based materials in the area of medical, ra iopbarmaceuticals, and radioactive waste has drawn attention due to their availability and btocompatibihty. See Alves, N.M., and Mano, IF.“Chitosan derivatives obtained by chemical modifications for biomedical and environmental applications” International Journal of Biological Maeromotecules, 43, 401-414, 2008; Berger, I, Reist, M, Mayer, j.fvb, Felt, G., Peppas, N.A., and Gumy, R.“Structure and interactions in covalently and ioniealiy crosslinked chitosan hydrogels for biomedical applications, European Journal of Pharmaceutics and Biopharmaeeutics, 57, 19-34, 2004. It is reported that the chemical changes in chitosan occur due to irradiation and the extent of radiation-induced reaction depends on the polymer network structure. See Zainol, I,, Aki!, H.M, and Maxtor, A,“Effect oί g-ray irradiation on the physical and mechanical properties of chitosan powder” Material Science and Engineering C, 29, 292-297, 2009; Chang, K.P., Cheng, C.H., Chiang, Y.C., Lee, S.C. el a!.,“Irradiation of synthesized magnetic nanoparticles and its application for hyperthermia” Advanced Materials Research, 47-50, 1298-1301 , 200S; Casmlro, M.H., Boteiho, M.L., Leal J.F., and Gil, M.H.“Study on chemical, UV and gamma radiation- induced grafting of 2~hydroxyethyl methacrylate onto chitosan” Radiation Physics and Chemistry', 72, 731 -735, 2005; Park et ah “Radioactive chitosan complex for radiation therapy” US Patent 5,762,903, June 9, 1998; Wemvei, Z,, Xiaoguang, Z., Li, Yu, Yuefang, Z., and JiaZhen, S.“Some chemical changes in chitosan induced by y-ray irradiation” Polymer Degradation and Stability, 41 , 83-84, 1993; Lim, L. Y., Khor, E,, and Koo, O.“y irradiation of chitosan” Journal of Biomedical Material Research, 43 (3), 282-290, 1998; Yoksan, R., Akashi, M, Miyata, M, and Chiraehanchai, S, “Optimal g-ray dose and irradiation conditions for producing low molecular weight chitosan that retains its chemical structure” Radiation Research, 161, 471-480, 2004; Lo, Y.B, Wei, G.S., and Peng, 3, ’‘Radiation degradation of chitosan in the presence of HjC” Chinese Journal of Polymer Science, 22 (5), 439-444, 2004, However, there is very limited information available on the radiation effect on cross-linked chitosan composite matrices,

^M27J Current research in the area of radiation resistance adsorbent materials, pertaining to the technology development, for the selective separation of Isotopes and their applications In medical and nuclear environmental Held are the forefront of science and engineering. One of the main concerns of the adsorption techniques is the cost of the resin and their performance under high radiation environment. The chemical properties of the functional groups of the resin, which is active metal binding sites for resin, are subject to change by the interaction with ionizing radiation. In adsorption process, this may cause poor selectivity of the resin materials for metal ions and therefore hinders their application.

|0028| The active surface of the resin is considered to be the critical structures of MPCM resin. In case of exposing the MPCM resin to higher radiation field, the critical structure of the resin, which will primarily interact with the imparted energy from the ionizing radiation, needs to be protected. It is evident from SR and XPS analysis that MPCM resin may undergoes radiation induced cross-1 hiking reaction under high radiation field but the performance for metal ion uptake before and after the irradiation reported to he remained same. However, the main constituents of MPCM resin are low Z elements (with less stopping power), therefore, the negative impact of high energy particles on MPCM surface can be minimized by maintaining proper aspect ratio of the column. Furthermore, the critical

I w structure of the resin, which is also porous in nature, is assumed to be thin, due to range consideration; it should he protected also front interaction of radiation.

SUMMARY

(TO2 J One embodiment disclosed herein relates to a radiation-resistant sorbent comprising giutara!dehyde-crosslinked chitosan.

|Sb3S| More particularly, disclosed herein are chitosan-based ieroporous composite micron-size particles and chitosan-titania mieroporous composite material which was prepared by cross-linking chitosan with giuteraldehyde in the presence of a catalyst.

[0D311 Even more particularly, disclosed herein is a sorbent containing a mieroporous materia! of chitosan that has been crosslinked with glutaraldehyde in the presence of a catalyst, such as an acid (e,g., HCl) to a giuiaraldehyde concentration of about 2 to 4 wt%, and which is resistant to degradation from exposure to beta and gamma radiation, and to degradation from exposure to adds or alkaline solutions,

f 01)32 Without wishing to be bound by theory, it is believed that the cross- linked mieroporous chitosan matrix enhances the add resistance and mechanical strength of the chitosan parfide. As a result, the uptake capacity of the cross-linked particles increases for metal ions from acidic or alkaline radioactive solution in comparison to available commercial resins and commercial aluminas. This Increased uptake can result in efficiencies for molybdenum as high as 500-700 mg/g of sorbent, more particularly, about 600 mg/g of sorbent.

|0C133| Described herein arc embodiments of chitosan-based mieroporous composite materials which were prepared using solution easting and combination of solution easting and sol-gel method.

[0©34| In one embodiment, chitosan was cross-linked with gluteraidehyde in the presence of add as a catalyst at temperatures of around 70"C under continuous stirring. Without wishing to he bound by theory, it is believed that amino groups present in the chiiosan structure are protonated, and thus shielded from the reaction with gluteraldehyde, it is also believed that at temperatures of around ?0^t!C, more aldehyde groups are available for reaction than are available at room temperature. In this ease, without wishing to be bound by theory, it is believed that glutaraidehyde undergoes aldol condensation and the free aldehyde group will react with OH groups of chitosan in the presence of an acid catalyst, so that the polymerization of chitosan with giutaraldehyde is a condensation polymerization. Reaction times generally range from about 4 hours to about 8 hours. In one embodiment, the mole ratio of chitosan hydroxyl group to gluteraldehyde is desirably maintained at around 4/1 ,

|0I13S In a particular embodiment, the crosslirsked material can be further processed by, washing to remove excess giutaraldehyde, drying, wet or dry milling, and additional chemical processing. One example of this additional chemical processing that has been found to be particularly suitable is at least partial oxidation with an oxidizer, In particular, oxidation with one of more of a permanganate (e,g._« by a potassium permanganate solution containing at least about 14 mg n/L of solution), a peroxide, a chlorite, a hypochlorite, a dichromate, or a metal oxide, or other ambiphilte oxidizer, is especially suitable for increasing the selectivity of the sorbent for o(Yl) with respect to Tc(VIl), and for the efficient and rapid elution and recovery of technetium from loaded sorbent. More particularly, an oxidizer comprising one or more of an alkali metal chlorite, an alkali metal hypochlorite, an alkali metal diehromate, or a transition metal oxide is desirably used. More particularly, an oxidizer comprising one or more of sodium chlorite, sodium hypochlorite, polassium diehromate, or cerium oxide is desirably used. In addition to oxidizing the erosslinked sorbent material, these oxidizers can desirably be Included in an eluent solution used to release technetium from the sorbent. Desirably, such oxidizers are included in a saline-containing eluent solution in concentrations ranging from about 5 to about 40 m for chlorites or hypochlorites.

10036] Desirably, the sorbent has a surface area that ranges between about 10 and about 100 m¾ and more particularly is about 25 m²/g, Also desirably, the sorbent has a point of zero charge ranges from about 7.5 to about 8.8, and more particularly is about 8.8,

|0037j Embodiments of the sorbents described herein have an excellent holding capacity for molybdenum, and can sorb molybdenum in amounts of around 60 wt%, based on the dry weight of the sorbent, or higher. This holding capacity can be around 6,25 mmoi/g of sorbent, or higher. The sorbents also have excellent selectivity for molybdenum with respect to technetium, and are able to hold molybdenum while passing pertechnale ion in saline solution with an efficiency of at least about 80%, Embodiments of the sorbents disclosed herein also provide excellent capacity to sorb heavy metals, including, e.g., the ability to sorb Hg in amounts of 2,96 mmo!/g dry sorbent or higher front aqueous solution at pH 6,

[0Q38] In another embodiment, titanium oxide was incorporated into the chitosan gluteraldehyde composite polymer matrix, The development of crystalline silica tltanate (CST) and titanium-based oxide materials has paved the way for metal ions adsorption studies onto hydrous titanium oxide from the radioactive and non-rad I oac live waste streams. See Anthony, R. G,, Doseh, R.G,, Gu, D._s and Philip, C.V. "‘Use of siSicotitarsates for removing cesium and strontium from defense waste” Ind. Eng, Chem. R.es„ 33, 2702-2705, 1994; Maria, P,, Meng, X,, orfiatts, G,P., and iing, C, “Adsorption mechanism of arsenic on nanocrystalline titanium dioxide” Environ, Sci, Techno!, 40, 1257- 1262, 2006; Meng el ah,“Methods of preparing a surface-activated titanium oxide product and of using same in water treatment process” US Patent 7,497,952 B2, March 3, 2009. Qazi and Ahmed (201 1 ) reported the hydrous titanium oxide as an adsorbent for "Mo and its

l potential for use in ^Te generator, Qazl, Q,M, and Ahmed. M.“Preparation and evaluation of hydrous titanium oxide as a high affinity adsorbent for molybdenum (^9SMo) and its potential for use in ^99mTe generators” Radioehimtea Acta, Doi: SQ,1524/raet.201 M S 17201 1. (1 has been suggested that titanium oxide can form surface complex with metal ion resulting from a bidenate bonding mode to surface oxygen atoms, Hasan, 3,, Ghosh, T.K., Prelas, M.A., Viswanath, D.S., and Boddu, V.IVL“Adsorption of uranium on a novel bioadsorhent ehitosan coated perlite” Nuclear Technology, 159, 59-71, 2007,

[0039] However, none of these documents disclose that TiC¾, when dispersed on ehitosan matrix, would enhance the overall capacity for metal Ions uptake from radioactive waste solution. In the method disclosed herein, hydrous titanium oxide gel was prepared using the sol-gel technique. The titanium oxide gel was incorporated into the ehitosan and glutcraldehyde matrix in the presence of HCi as a catalyst.

[0040] Thus, on embodiment relates to a method for preparing a radiation- resistant sorbent, comprising:

[0041] combining ehitosan with water in the presence of an acid to form a ehitosan gel;

[0042] adding glutaraldehyde to the gel to form a semi-solid mass in presence of catalyst at 7Q“C;

[0043] washing the semi-solid mass to remove unreacted giuiaraidehyde and form a washed mass;

[00441 suspending the washed mass in aqueous base to form a neutralized cross! inked mass; and

[00451 drying the neutralized crosslinked mass to form the radiation-resistant sorbent

[0046] Another embodiment relates to such a method further comprising:

4 |0047J forming an amorphous titansa gd by add catalysed hydrolysis and condensation of titanium isoprapoxide;

(G048| mixing the amorphous tkania gel with the ch tosan gel under conditions sufficient for the gets to react prior to said adding giutaraldehyde,

[0049] in one embodiment, the chhosan-based microporous composite material was then suspended in a solution with pH 3 and irradiated at 50,000 krad using ^Coirradiatior. The specific objectives of this work were to 1) prepare eh tosan-based microporous composite particles to adsorb metal ions from highly acidic or alkaline radioactive waste solutions; and 2) optimize the cross-linking process to obtain maximum metal binding sites.

{0050] Thus, another embodiment relates to a method of separating isotopes from mixtures thereof, comprising:

fSSSl] contacting a mixture of at least two isotopes with a radiation resistant sorbent according to claim i that preferentially sorbs at least one of said Isotopes;

|TO52] sorbing at icast one of said isotopes onto or into said sorbent while one or more of the remaining isotopes are not significantly sorbed by the sorbent;

|0OS3] removing said one or more remaining isotopes from said sorbent. fCNDSdJ Chltosan cross-linked composite is an excellent low cost alternative adsorption materia! compare to available resins, and thus a desirable adsorbent material to remove metal ions from radioactive and nonradioaetive aqueous solutions, it has been found that the success of adsorption processes in the ^wMo/"^mTe generator systems depends largely on the cost and capacity of the adsorbents and the ease of "^Tc release from the generator. The main problem with this particular method from a radiation safety standpoint involves the “breakthrough”, or partial elution of the "Mo parent along with the "^mTc from the generator, which must be kept within Nuclear Regulatory Commission (NRC) standards. Embodiments of the material and methods described herein provide good, selective release of ^99,:5Tc from the generator, thereby solving this problem and fulfilling a need for such a generator.

|O055j it is believed that chemical dement with a high atomic number of protons in the nucleus, a high 2 element, with higher stopping power wiH have affinity for certain isotopes can be cross linked with MPCM resin matrix. U is also envisaged that the radiation tolerance limit and selectivity of the MPCM resin for certain isotopes, can be further enhanced by the high Z dement crosslinked MPCM resin as it will not he limited by the radiolytic driven reaction. Therefore, it is a further embodiment to provide a sorbent that will reduce the primary impact of high radiation flux and minimize the dlolytic effect on to the PGVTs porous critical structure compared to regular organic based resin such as MPCM resin.

The sorbent includes a microporous materia! Including chitosan which has been erosslinked with glutaraldehyde in the presence of a catalyst to a glutaraldehyde concentration of about 2 to about 4 wt% to produce a cross-linked chitosan-gluteraldehyde composite matrix. The cross-linked chitosan-gluteraldehyde composite matrix Is resistant to degradation from exposure to beta and gamma radiation and from exposure to acids. A plurality of nanoparticles of a high Z element is disposed in the cross-linked chitosan- gluteraldehyde composite matrix and is integrated with the cross-linked chitosan- gluteraldehyde composite matrix.

|©CS571 It is a further embodiment to provide a method for preparing a radiation-resistant sorbent. The method includes the steps of combining chitosan with water in the presence of an acid to form a chitosan get, The method also includes a step of adding glutaraldehyde to the gel to form a semi-solid mass in the presence of catalyst at 70*0, in w'here condensation polymerization of reaction mass occurs. The method further includes a step of washing the semi-solid mass to remove unreaeied glutaraldehyde and form a washed

lb mass. The next step of the method is suspending the washed mass in aqueous base to form a neutralized crosslinked mass. Then, a plurality of nanoparticles of a high Z element is disposed on the neutralized crosslinked mass. Next, the neutralized crosslinked mass including the plurality of nanoparticles is dried under vacuum to form the radiation-resistant sorbent.

|0058] it is a further embodiment to provide a method for preparing a plurality of nanoparticles for use in a radiation-resistant sorbent. The method includes a first step of grinding a salt of a high Z element with a surfactant under an inert atmosphere. The method also includes a step of adding deionized water of between 5ml to 10ml during the step of grinding to form a homogenous mixture. The method further includes a step of adding an alkaline solution to the homogenous mixture under sonicaiion to nucleate and grow the nanoparticles under an inert atmosphere. Next, the surfactant of the homogenous mixture is transferred into an alcohol solution containing the nanoparticles, Then, the alcohol solution is sonicated to obtain a uniform intermediate stage of the nanoparticles. The precipitates, e.g. intermediate stage of nanoparticles, are then sonicated and washed thoroughly wit ethanol and deionized water to remove surfactant and impurities, respectively.

1 d§ ] In addition, embodiments of the chitosan crosslinked composites disclosed herein can be used in a method for separating or concentrating or both one or more heavy metals from a liquid stream, such as a waste stream or a process stream, by contacting a liquid stream containing one or more heavy metals with the chitosan crosslinked composite and sorbing one or more of said heavy metals thereon,

BRIEF DESCRIPTION OF DRAWINGS

]9868] Various aspects of the embodiments disclosed herein can be understood more clearly by reference to the drawings, which should not be interpreted as li iting the claimed invention.

[8861] FIG, 1 Is a scanning electron microscope photomicrograph that shows chitosan and embodiments of modified chitosan {MPCM} disclosed herein, FSG la shows unmodified chitosan; FIG. lb shows an embodiment of MPCM material.

[8862] FIG 2 is a graph showing the results of a ther ogravi etric analysis

(TO A) of chitosan and an embodiment of MPCM.

[8863] FIG, 3 is a graph showing an X-ray diffraction pattern of chitosan and an embodiment of MPCM material.

[8864] FIG. 4 is a graph showing Fourier Transform Infrared (FT!R) spectra of chitosan and an embodiment of MPCM material disclosed herein,

[886S] FIG, 5 is a graph showing X-ray photoelectron spectroscopy (XPS) survey scans for chitosan and an embodiment of MPCM,

[8866] FIG, 6 is a graph showing X-ray photo ectron spectroscopy (XPS) spectra for chitosan and an embodiment of MPCM. FIG. 6a, 6h, and 6c sh w' the C Is, O i , and N I positions, respectively.

[8867] FIG. 7 is a graph of energy-dispersive X-ray spectrometry (EDS) mlcroarsalysis spectra of an embodiment of MPCM herein FSG 7a shows speetra of chitosan and an embodiment of MPCM before and after Irradiation FIG 7b shows comparison of chitosan and an embodiment of MPCM, FIG 7e shows comparison of an embodiment of MPCM before and after irradiation

[8868] FIG 8 is a schematic diagram showing a reaction pathway for the preparation of an embodiment of MPCM described herein. FIG. 9 Is a graph showing FT5R spectra of an embodiment of modified ehitosan disclosed herein before and after irradiation.

[Q070] FIG. 10 is a graph showing X-ray photoeiectron spectroscopy (XPS) spectra for an embodiment of MPCM before an after radiation, FIG. 10a, 10b, and 10c show the C I s, O 1 s, and N 1 s positions, respectively,

[0071] F!G, S S is a graph showing surface charge of an embodiment of

MPCM with and without exposure to 1% of Mo (VI) in solution In the presence of 1 M NaNOi.

[0072] FIG. 12 is a graph showing the effect of pH on molybdate sorption on an embodiment of MPCM, with initial conditions of a concentration of 5.21 moi/L and temperature 298 K.

[0073] FIG. 13 Is a schematic diagram showing reaction mechanisms for sorption of Mo (VI) onto an embodiment of MPCM from aqueous solution,

[0074] F1C, 14 is a graph showing equilibrium sorption isotherms for Mo (VI) uptake on an embodiment of MPCM, showing experimental data (*) correlated with the Langmuir isotherm model (solid line) under conditions where the concentration of Mo(Vi) in solution is in the range of i mmoi/L to 94 mmoi/L, temperature 298 K, pH ~3.

[0075] FIG. 15a is a graph showing a breakthrough curve for Mo (Vi) sorption on a bed of MPCM, the inlet influent concentration was 5.21 mmole Mo (Vi)/L at the pH of 3.; FiG. 15b is a graph showing the effect of influent solution pH on the breakthrough curve for Mo (VI) from a column packed with an embodiment of MPCM, The inlet influent concentration was 5.21 mmole Mo (Vi)/L with 153,8 mmole NaC!/L at the pH of 4 to 7, respectively. For both figures, the bed height of the column was 3.2 cm. the inlet influent flow rate was 1 mL min. |q§76] FIG, 16 is a graph showing breakthrough curves for pestechreale from a column packed with an embodiment of MPCM without oxidation which was loaded with 6.25 mM of Mo (VT)/gram of MPCM. The volume of the column was 2,5 cm³. The inlet Slow rate was 1 mb' min. The inlet influent concentration was 0,25 mM pertechnetate /L in saline (0.9% aCS) solution.

|IM>77J F G. 17 is a graph showing the surface charge of oxidized and non- oxidized MPCM exposed to 1 % Mo (VS) In aqueous solution in the presence of IN NsNOj.

|8078f FIG, I S is a graph showing an elution profile for ^9¾Tc from an embodiment of MPCM loaded with Mo (VI) spiked with "Mo,

(0879] FIG. 19 is a graph showing the relationship between number of eiution(s) and the percentages of ^9¾nTc and Mo (VI) release from an embodiment of MPCM as sorbent.

]8088| FIG, 20 is a flow diagram for a process using a ^99mTe/"Mo generator systems and a "Mo production using neutrons capture method, using an embodiment of MPCM as the sorbent,

(0881 ] FIG. 2 Ns a graph showing the effect of temperature on molybdenum uptake onto MPCM-CiCh resin under conditions of initial solution concentration of 1% Mo solution with 25 mM NaOCl, pH of 3,0, and solid to liquid ratio of 1 : 100 with a contact time of 0.5 hour,

(0082] FIG, 22 is a graph showing heat of adsorption at different loading and temperature (24°C to 50°€) of the resin of FIG, 21 ,

|CH S3] FIG. 23 Is a graph showing the projected specific activity of a proposed MPCM based generator with a column volume of 6- mL

(0084jj FSG. 24 is a graph showing FT!R spectra of chitosan and another embodiment of modified chitosan disclosed herein. ]0085| FIG, 25 is asi 1R spectra of unirradiated molybdenum loaded MPCM-Z resin and the molybdenum loaded MPCM-Z resin irradiated at 250 kGy.

]O086j FIG, 26 is an IR spectra of unirradiated molybdenum loaded MPCM-Z resin and the molybdenum loaded MPCM-Z resin irradiated at 250 kGy

[0087] FIG, 27 is a graph illustrating the relationship between intensity ratios from C-O-C group { 13 oso/l _{Ϊ &}2Q) and hydroxy! group i asidinoo) and radiation doses (kGy).

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

0O88] The methods disclosed herein and the resulting modified chitosan materials, as well as methods for the use thereof, can be beter understood by reference to the following examples, which are intended illustrate, not to limit, the invention or the appended claims.

[0089] Medium molecular weight chitosan (about 190,000 to about 310,000, as determined by viscosity data) that has been 75-85% deaeetyiated was obtained from Sigma-AIdrieh Chemical Corporation, Wl, USA, All chemicals used in the examples were of analytical grade,

[0090] The modified chitosan disclosed herein can be prepared according to the reactions shown schematically in FIG, 7, by crosslinking with giuiaraidehyde under addle conditions at temperature conditions set forth below. While the amount of giuiaraidehyde used may vary somewhat, it has been found effective to use from about 2 ml to about 10 ml, more particularly from about 2 ml to about 8 ml, even more particularly, about 6 ml, of giuiaraidehyde per 4 g of chitosan. The pH of the cross! inking reaction between giuiaraidehyde and chitosan may also vary somewhat, but it has been found effective to use a pH of between about 0.7 and about 3, more particularly between about 0,7 and 2, even more particularly, of about 1.0. The temperature of the erosslink g reaction may also vary, but is desirably between about 50 °C and about 80 °C, more particularly, around 70 ^eC, j009t| It another aspect of the preseat disclosure to provide a sorbent for use in connection with separating isotopes from mixtures, The sorbent comprises a microporous material including chitosan which has been crosslinked with glutaraldehyde in the presence of a catalyst to a glutaraldehyde concentration of about 2 to about 4 w % to produce a cross-linked chitosan-glutera!dehyde composite matrix. The cross-linked chitosan- gluteraldehyde composite matrix is resistant to degradation from exposure to beta and gamma radiation and from exposure to adds. The cross-linked chitosan-g!uteraldehyde composite matrix includes a plurality of nanoparticles, made from a high Z element, disposed in the cross-linked ehitosan-gluteraldehyde composite matrix and integrated with the cross-linked chitosan-gluteraidehyde composite matri to reduce primary impact of high radiation flux and minimize radiolytie effect on said cross-linked chitosan-gluteraidehyde composite matrix,

[0092] Without being bound by theory, it is believed that chemical element with a high atomic number of protons in the nucleus, the high Z element, with higher stopping power will have affinity for certain isotopes can be crosslinked with MPCM resin matrix, It is also believed that the radiation tolerance limit and selectivity of the MPCM resin for certain isotopes, can be further enhanced by the high Z element crosslinked MPCM resin as it will not be limited fey the radiofytie driven reaction. Therefore, it is the inclusion of the high Z element will reduce the primary impact of high radiation flux and minimize the radiolytie effect on to the MPCM’s porous critical structure compared to regular organic based resin such as MPCM resin,

[0093] The main objective of addition the high Z element, other than

Molybdenum (Mo), into the cross-linked chitosan-gluteraidehyde composite matrix is to protect the structure of the matrix from the Mo-99 related radiolytie impact. Preferably, the plurality of nanoparticles is made from the high Z element of Hafnium (HI). Hf is a

‘>7 preferable high Z element for use connection with the cross-linked chitosan-gksteraldehyde composite matrix because Hf has no known toxicity and, therefore, can be qualified to use in medical applications. More preferably, Hf is present in the cross-linked ehitosan- gluieraldehyde composite matrix at a range of between 0, 15g to 0 35 g per grams of the cross-linked ehitosan-gluteraldehyde composite matrix H should be appreciated that the amount of Hf added to the composite matrix directly corresponds to the amount of activity of Molybdenum. For example, the composite matrix with lower amount of Hf is suitable for lower specific activity, e.g natural Mo, while the composite matrix with higher amount of Hf is suitable for higher activity enriched Mo. St should also be noted that excess amount of Hf also reduce resin capacity for molybdenum.

(0094) It Is another aspect to provide a method for preparing a radiation- resistant sorbent. The method includes a first step of combining chitosan with water in the presence of an acid to form a chitosan gel. The next step of the method is to add giuiaraidehyde to the gel to form a semi-solid mass in the presence of catalyst at ?G^&C, in where condensation polymerization of reaction mass occurs. The semi-solid mass is then washed to remove unreacled giutaraldehyde and form a washed mass Next, the washed mass is suspended in aqueous base to form a neutralized crosslinked mass Then, a plurality of nanopartic!es of a high 2 dement is disposed on the neutralized crosslinked mass. It should be appreciated that the high Z element being used is for the step of disposing is made from hafnium (Hi) between 0 15g and 0,3Sg per grams of the neutralized crosslinked mass. After disposing the high Z e!e ent the neutralized crosslinked mass including the plurality of nanopartides is dried under vacuum to form the radiation-resistant sorbent it should be appreciated that the high Z element such as hafnium can be integrated in to the neutralized crosslinked mass either self-asse bles or radiation induced cross-linking process. f(HI95] It is another aspect to provide a method for preparing a plurality of mmopartieies for use in a radiation-resistant sorbent. The method includes a first step of grinding a salt of a high Z element with a surfactant under an inert atmosphere, It should be appreciated that the salt of the high Z element is an aqueous salt that cars be soluble in water such as Hafnium Chloride of HfCbO®SI-bO, The amount of surfactant used for making the nanopartides ranges between 4 wL to 20 wt%. The next step of the method is adding deionized water of between 5 mi to lOtnl during the step of grinding to form a homogenous mixture. The deionized water is added to the surfactant and the high Z dement under continuous grinding. It should be appreciated that, during the step of adding the deionized water, there is no chemical reaction formed instead the homogenous mixture of the surfactant and the high Z element is formed. The next step of the method is to add an alkaline solution to the homogenous mixture to nucleate and grow the nanopartides. It should be appreciated the addition of the alkaline solution to the homogenous mixture of the surfactant and the salt of a high Z element can be conducted under sonication to obtain a homogenously dispersed solution. Preferably, the alkaline solution added to the homogenous mixture is selected from NaOH or NRtOH. To avoid impurities and possibie side reactions, the steps of grinding, adding the deionized water, and adding the alkaline solution are conducted in an inert atmosphere, e.g. under Nitrogen. The growth of the nanopartides can be further facilitated with the addition of excess amount of ethanol in the final solution obtain a uniform intermediate stage of the nanopartides. The precipitates, e.g, the intermediate stage of Hafnium oxide nanoparticles, are then sonicated and washed thoroughly with ethanol and deionized water to remove the surfactant and impurities, respectively, In this step, the mass of the hafnium nanopartides are mixed with chitosan gel before adding glutaraldehyde in the final step of MPCM preparation process. By this way, the hafnium nanopartides can be deposited onto the MPCM resin matrix and the MPCM resin matrix can be dried under vacuum and at 120°C for 12 hours.

EXAMPLE 1

|iMI9f j The ionic capacity of the chitosan used in this study was in the range of

9 to 19 rmi!iequiva!ents/g, measured using a standard titrametric method, About 4 g of chitosan was added to 300 mL Di water with i mL acetic acid and stirred for 2 hr at 70°C to form a gel Approximately 5 mL of HCI/HNO3 was added into the chitosan gel and kept under continuous stirring for another i hr at 70“C to assist protonation of the amino substituent groups, which is beneficial for the reasons given below.

@Q97| The reaction with gluteraldehyde was performed by drop-wise addition of approximately 6 ml. g!uieraidehyde solution, having a concentration of 50%, to the acidic chitosan gci under continuous stirring (established based on trial and error, but generally from 200 rpm to 500 rpm) at 7Cf€ The final pH of the the mixture was approximately l ,0. The amount of gluteraldehyde was used in this study was established based on trial and error basis. The mixture was kept under continuous vigorous stirring (500 rpm) at 70*0 for another i hr to obtain semi-solid gel. The amino groups present in the chitosan are much more reactive with aldehyde through Schiff s reaction than the hydroxyl groups of chitosan, it was envisaged that, at 70°C, more free aldehyde groups will be present in the solution than would be present at room temperature. In acidic solution, the protonation of the amine group will inhibit the formation of complexes of aldehyde and amino groups. Moreover, gluteraldehyde may undergo aldo! condensation and the reaction of hydroxyl groups of chitosan with free aldehyde can be catalyzed by acid at 7CPC.

1S098J The resulting mass was then thoroughly washed with 2% onoethanoi amine to remove any unreaeied gluteraldehyde. The mass was then suspended in 0J M NaQH solution for 4 to 6 hours. The cross-linked mass was separated from the solution and washed with G.1 M HCI and then with deionized water (D!) until the pH of the effluent solution was 7, The cross-linked mass was then dried in a vacuum oven overnight at 70^iSC. The cross-linked ehiiosan-g!uiera!dehyde composite is referred to as "MPCM" or "mieroporous composite materia!" herein.

|0099] The MPCM was ground using a laboratory jar mill to a particle size in the range of about 50 to 200 pm, An amount of these MPCM particles was suspended overnight in aqueous solution having pH 3, The pH of the solution was maintained using 0. I M HN(¾. The suspended MPCM particles were irradiated using ⁶ Co as a y source, The characterizations of the MPCM sample were performed using SEM, EDS X-ray mieroanalysis, FT1R, and XPS spectroscopic analysis,

[00100] A scanning electron micrograph (SEM) of chitosan and MPCM material was taken to study the surface morphology and is shown in FIG. i , The SEM secondary electron micrograph of the samples %'ere obtained using baekseatter electrons with an accelerating potential of 10 kcVh The SEM micrograph of the cross-section of chitosan and MPCM sample is shown In FIG. l a and l b, respectively, It appears from FIG. la that chitosan Is nonporous, and from PIG, l b the MPCM appears to be mieroporous in nature,

[Q01Q1] TGA analysis of the MPCM as-prepared in the lab and pure chitosan, respectively, was performed using a TGA (TA Instruments) analyzer in a flowing nitrogen atmosphere {200 mtimm), For each experiment, approximately 20 g of MPCM was heated to the temperature range from 30 to 6QG^yC in an open alumina crucible at predetermined heating rate, TGA measures the amount and rate of weight change of the sample as it is heated at a specified rate. Thermogravimetrie analysis of both MPCM and chitosan was obtained providing complimentary information about changes in composition as heating progresses under controlled conditions, The heating rate in this analysis was set to 5°C/mln.

7/s TGA profiles as shown in FIG. 2 indicate a two-step decomposition process for pore ehitosan while for MPCM it decomposes slowly with the increase in temperature.

[M1Q2| The rmogravi metric analysis (TGA) of the ehitosan at a heating rate of

5 °C /min in nitrogen atmosphere (200 mL/ in) Indicates that complete dehydration occurs at 250°C with a weight loss of 8%. The anhydrous ehitosan further decomposed in the second step with a weight loss of 32% at 360°C. It was burned out completely at 600°C with a further 12% loss of weight.. The remaining 48% is the burnt residue of the ehitosan at 6GCFC,

1 >f 103 in ease of MPCM, The complete dehydration occurs at 230°C with a weight loss of 12%. The anhydrous MPCM burned out completely at 600“C with a weight loss of 36%. The remaining 52% Is the burnt residue of MPCM at 6G⁽F'C. It may be noted that the combustion product of MPCM Is 4% less compared to ehitosan, which Indicates that MPCM contains 4% of crossl inking agent, such as glutaraldehyde, that was burned out completely in this heating range.

[C 0104| The swelling behavior and acid tolerance of the MPCM material were also evaluated. The swelling behavior of MPCM w performed by Immersing it In deionized water and saline solution using a process described by Yazdani-Pedram el ah, ’’Synthesis and unusual swelling behavior of combined cationic/non-ionic hydrogels based on ehitosan," Macromol. BioseL 3, 577-5 1 (2003).

[d010S Swelling behaviour of ehitosan was also studied with deionized water and saline solution.

1Q0106| The swelling ratio of the ehitosan and MPCM was calculated using the following equation;

Swelling ratio {%}” [(V_s - Vd}/Vd| * 100, 1

where ¥_s is the volume of swollen MPCM and Y_<i is the volume of dry sample, in deionized water it was observed that the ehitosan swelled by approximately 105% of its original volume at 24 hours of equilibrium lime. MPCM shows very fast swelling behavior reaching approximately 200% increase within five minutes and reaching equilibrium at 24 hours, The swelling studies with deionized water were performed within the pH range of 3 to 6. At equilibrium, the maximum volume of the MPCM was almost 219% more than its dry volume.

Similar swelling behavior of MPCM was also observed for saline (0.9% NaCl) solution. At equilibrium, the MPCM volume increases up to 223% of its original dry volume in saline solution. The results of the swelling studies indicate that the hydropbilieity of the MPCM is greater than chitosan. St is reported that the swelling behavior of chitosan hydrogel depends on the ionisable groups that are present within the gel structure. See Ray et at, Development and Characterization of Chitosan Based Polymeric Hydrogel Membranes, Designed Monomers & Polymers, Vo!. 13, 3, 193-206 (2010). Due to protonatson of -NHa groups of MPCM in the solution pH range of 3 to 6, the rapid swelling behavior of MPCM in deionized water can be attributed to high repulsion cf NHf groups. In saline solution, at pH higher than 6, the carboxylic acid groups become ionized and the electrostatic repulsive forces between the charge sites (COO-) cause increasing in swelling, See Yazdani-Pedram el ah, supra; Radhakumari et ah,’’Biopolymer composite of Chitosan and Methyl Methacrylate for Medical Applications," Trends Biomater. Art if. Organs, 18, 2, (2005); Felintc el al._s“The swelling behavior of chitosan hydrogel membranes obtained by UV- and g-radiatk ," Nuclear Instruments and Methods in Physics Research B, 265, 418-424 (2007).

|0 l08j The MPCM sample was submerged in different concentrations of HCf H O3, and H2SO4 acid for 24 hours. Chitosan tends to form a gd in addle media making it unsuitable for its use in an adsorption column for separation of metal ions from aqueous solutions. One of the main objectives of this study was to make a chitosan-based add resistant material while exposing more Ni l:· groups, which is the active metal binding site

38 for chitosan. Table 1 shows she results for the acid tolerance capacity of MPCM. It was observed that MPCM material shows better HCI tolerance capacity than it does tolerance for HNC¾ and PbS(¾. The physical size and shape of MPCM did not show any sign! (leant change op to !2M HCI, I2M H₂SO and 3,9 M HNOj solution hoi the MPCM appeared to be dissolved completely in 7.8 M HNCh solution, it is evident that the MPCM Is more acid resistant compared to chitosan.

Table I . Effect of different concentrations of acid on the physical properties of material

i nol-dissolved

k ~ tends to form gel or completely issolve

fOO!OS] Figure 3 shows the XRD pattern for pure chitosan and MPCM beads. The chitosan sample showed a diffraction peak near 20^s, indicative of the relatively regular crystal lattices (1 10, 040) of chitosan. See Wan et ah, "Biodegradable PolySaetk /Chhosan Blend Membranes," Blomacromolecules 7(4): 1362-1372 (2006). The peak observed for MPCM Is appeared to be broadened suggesting that the MPCM sample is amorphous in nature. St also indicates that chitosan and glntaraidehyde formed a complex in the presence of acid; therefore the crystalline structure of the chitosan was disrupted by the chemical bonding between chitosan and g!utaraldehyde.

[6Q1 I0] Fourier Transformed infrared spectra (FUR) of the MPCM sample prepared above were examined on a BRUKER FTSR. spectrometer equipped with a broadband, h½ cooled mercury-cadmitsm-idluride (MCT) detector and a KCi beam splitter. FT1R spectra were collected in absorbance mode with 8 cm ¹ resolution using 128 scans ranged from 400 to 4000 cm * . The iniermoieetdar interactions between ehitosan and g!uterafdehyde in the presence of HO acid are reflected by changes in the characteristics of IR peaks. FIG, 4 shows the comparison of l spectra of ehitosan with MPCM . In the region of 2900 cm⁴ to 3500 cm ^® of the spectrum, ehitosan and MPCM exhibited peaks at 3498 cm ⁵ and 2950 cm ⁵, respectively, corresponding to the stretching O-H and N-H groups and C~H stretching vibration in CH, and €H_¾. The peaks at 1350 to 1450 em ^J indicate alkane C-H bending.

100111] The complicated nature of absorption spectrum in the 1650-1500 cm⁴ region suggests that aromatic ting bands and double-bond (O-C) vibrations overlap the OO stretching vibration bands and OH bending vibration bands. The peaks expected in this region of IR spectra include proionaied amine (-NiV), amine (-Nib), and carbonyl (- CON HR) band. FIG. 4 shows a peak at 1600 cm * with a shoulder like peak centered at around S 570 c ⁴ and 1670 cm ¹ represent --MFfe and amide I, respectively for ehitosan. However, the presence of a comparatively sharper peak at 1590 cm⁴ In PCM than the peak observed for ehitosan suggests the presence of NHy^: band In the MPCM sample.

f0Ol !2J The XPS analysis of ehitosan and the MPCM sample prepared above was performed to gain a better understanding of mtermolecnlar interaction between ehitosan and gluteraidehyde. In the XPS analysis, a survey scan was used to ensure that the energy range was suitable to detect all the elements. The XPS data were obtained using a &RATQS model AXIS 165 XPS spectrometer with monochromatic Mg X-rays (hv^Si 1253.6 eV)_t which were used as the excitation source at a power of 240 W. The spectrometer was equipped with an eight-channel hemispherical detector, and the pass energy of 5-160 eV was used during the analysis of the samples. Each sample was exposed to X-rays for the same period of time and Intensity, The XPS system was calibrated using peaks of U0₃(4f7/2), whose binding energy was 379,2 eV. A 0° probe angle was used for analysis of the samples, [001 ί 3] FiG, 5 shows the peak positions of C Is, O is, and N i s obtained by the survey scan of chitosan and the MPCM sample prepared above, respectively, FiG. 6 shows the peak positions in detail for C Is, G is, and N i present in chitosan and MFC hi. The C-l s peak observed showed two peaks on deconvolution, one for C~N at 284,3 eV and the other one for C-C at 283,5 eV (FiG. 6a). in the MPCM sample, the C-Cs peak appears to be folded and shifted slightly, whereas the C-N peak showed higher intensity compared to chitosan (FIG, 6a), The peaks for oxygen containing groups (O is) were found at 530.5 eV and 531.1 eV for chitosan and PCM, respectively (Figure 6b),

[60114] Compared with the C Is and Ol s peaks of MPCM, it was observed that the C-C peak of chitosan at 283.5 eV folded and Ols peak shifted from 530.5 eV to 531.1 eV due to cross-linking reaction with glutaraldehyde, This suggests that the Ols component may be single bonded corresponding to -OH or C~0 moiety in the structure for different surface oxygen containing functional groups. See Wen et ah, "Copper-based nanowire materials: Tempiated Syntheses, Characterizations, and Applications," Langmuir. 21 , S O, 4729-4737 (2005), Chemical shifts are considered significant when they exceed 0,5eV. See Hasan et ah, "Adsorption of divalent cadmium from aqueous solutions onto chi osan-coated perlite beads," ind. Eng, Chem. Res., 45, 5066-5077 (2006). As a result, shifting of the O Is peak in MPCM sample also indicates that the glutaraldehyde reacted with oxygen-containing functional groups of chitosan. The XPS data suggests that the chemical binding of glutaraldehyde occurs with the C1TOH or OH groups on the chitosan structure which is also in agreement with the data obtained from FTIR analysis (FIG, 4).

[00115] The N Is peak for chitosan was at 397,5 eV (FWHM 1 ,87) for nitrogen in the -Nhb group of chitosan (FIG. 5c); for the MPCM the M Is peak appeared at 397.7 eV. One of the objectives for investigating the N I peak was to Identify whether amine groups, which are active metal binding sites for chitosan, were Involved in cross-linking reactions

3! with giutaraidehyde, FIG. 6c shows a strong M is peak for MPCM at 397,7 eV, which can be assigned to ~NHs groups_* suggesting that the amine groups of chitosan were not affected by the cross-linking reaction with giutaraidehyde. This is also evident from the FTIR spectra (FIG. 4).

|M116| Table 2 shows the XPS data for surface elemental analysis of the sample of MPCM, as determined from the peak area, after correcting for the experimentally determined sensitivity factor (±5%), it has been found that by preparing porous chiiosan based material, in this case the embodiment of MPCM described above, results in the exposure of more NFh groups on the surface of the material. The nitrogen concentration, as determined from the N I s peak on the sample of MPCM, was almost twice that calculated for chiiosan (Table 2). It is believed that the nitrogen content in the MPCM came entirely from chiiosan. The high nitrogen content in the MPCM, as shown in the Table 2. was due to the microporous nature of the MPCM which makes more amine groups available on the surface than is the case in the nonporous chiiosan. Tins is also consistent with the results reported by Hasan et al„ supra, obtained by dispersing chiiosan onto perlite. The changes in peak intensity of C I s and binding energy of O is peaks at 531.0 eV of the MPCM sample compared to chiiosan are believed to be due to the reaction with giutaraidehyde in presence of ac d as a catalyst.

Table 2: Absolute Binding Energy (BE) for the elements present in the chitosan and MPCM obtained from X-ray Pboloeieetron Spectroscopy (XPS) Analysis,

IQIIP71 Th energy dispersive spectroscopy (EDS) X-ray microanaiysis was performed on the same MPCM sample as was used for the SEM micrograph. The EDS microanaiysis was used for elemental analysis of MPCM (FIG. 7), The peaks for carbon, oxygen, and nitrogen are shown at 0,3 keV, 0.36, and 0,5 keV, respectively, which are the main components of chitosan (F3G. 7a, 7b). Due to the reaction with glutaraldehyde, the intensity of the carbon peak for MPCM increases; whereas, the intensity of the oxygen peak decreases in comparison to chitosan (FIG, 7b), FIG, 7b also shows that the nitrogen peak present in the MPCM sample shifted, due to protonation of amine groups (-N¾) compared to the nitrogen peak in chitosan. Based on the FOR, EDS, and XPS analysis, and without wishing to be bound by theory, the possible reaction mechanisms of glutaraldehyde with the OH groups of chitosan through the formation of acetal bonds are given in FIG, 8,

[091 IB] The MPCM sample described above was evaluated for radiation stability by irradiation with a ^S0Co source. The IR spectra of the MPCM composite sample before and after being irradiated using a ⁰Co source are shown in FIG, 9. The results in FIG, 9 shows that the MPCM sample suspended in w¾ter at pH 3,0 can tolerate y-radiation to about 50,000 krad without losing a substantial percentages of Its Identity.

|0O119| FIG. 7c shows EDS spectra of chitosan and MPCM particles before and after irradiation at 50.000 krad with a ^®Co source. FIG, 7c indicates that the intensity of 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 the XPS analysis of the MPCM sample before and after irradiation. It was observed that the magnitude of total C I s peak binding energy changed after irradiation as shown In Table 2. The C I s peak for the MPCM sample was 283.5 eV, while for the MPCM sample after irradiation^* two peaks were observed at 283.5 and 284,5 eV (PIG, SGa). The N Is peak present in the MPCM sample after irradiation around 397,5 eV can be assigned to Nfb groups in the MPCM structure. No change was observed for O-l s peak of the irradiated MPCM sample. The magnitude of the binding energy shift depends on the concentration of different atoms, in particular on the surface of a material. In comparison with the XPS (FIG. 10a~e), the Is and O i s peak of the MPCM sample did not shift before and after irradiation (Table 2), indicating that the chemical state of atoms was not much affected after irradiation. This is also reflected in the EDS and FTIR spectra as shown in FIG. 7 and 9,

[0(1120 j ^'Hie MPCM sample described above was evaluated for molybdenum sorption using batch techniques. About 1 ,0 gram of MPCM adsorbent was suspended in lOO L solution containing ammonium molybdate in the range of 1 mmoie/L to 94 mmoie/L, The initial pH values of solutions were adjusted from 2,0 to 8.0 using either 0,01 M NaOH or 0.1 M HC! so ution. The solutions were then kept in a shaker (160 rpm) for 24 hrs at 298K. After 24 hrs, the final pH was recorded for each solution and the solutions were centrifuged for 5 minutes at 3000 rpm to separate the supernatant from the solution. The supernatant was then filtered through a 0.45-pm membrane filter and the filtrate was analyzed for molybdenum removal by an Inductively Coupled Plasma (ICP) (Agilent 7700X) that is equipped with mass spectroscopy for molybdenum detection. The adsorption isotherm was obtained by varying the Initial concentration of molybdenum in the solution. The amount of molybdenum adsorbed per unit mass of adsorbent (qv) was calculated using the equation,

where Q and€V represent initial and equilibrium concentrations in mg/t, respectively, F is the volume of the solution In liters (L), and M is the mass of the adsorbent in gram (g).

[©©1211 The surface charge of a bead of MPCM sample was determined by a standard potentiometric titration method in the presence of a symmetric electrolyte, sodium nitrate, as per Hasan ef a!,, supra. The magnitude and sign of the surface charge was measured with respect to the point of zero charge (PZC), The pH at which the net surface charge of the solid is zero at all electrolyte concentrations is termed as the point of zero charge. The pH of the PZC for a given surface depends on the relative basic and acidic properties of the solid and allows an estimation of the net uptake of H and OH ions from the solution. The results are shown in FIG. 1 1 ,

(88122] The PZC value of the sample of MPCM 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 bead. However, it is reported that the PZC value of pure chitosan is within the pH range of 6.2 to 6.8. See Hasan et al, supra. It is observed from FIG, S S that a positively charged surface prevailed at a 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 the MPCM sharply increased at the pH range of 7,5 to 2.5 making the surface positive, At pH below 2,5, the difference between the initial pH and the pH alter the equilibration time was not significant, suggesting complete protonalion of amine (-NH ) groups present in MPCM. At higher pH, 7.5 to 8,8. the surface charge of the MPCM slowly decreased, indicating slow protonation of MPCM. In ease of chitosan, the extent of protonation is reported to be as high as 97% at a pH of 4.3. However, it decreases as the pH increased, The extent of protonalion of chitosan surface is reported to be 91 %, 50%, and 9% at pH 5.3, 6,3, and 7,3, respectively, Sec Hasan el al.” Dispersion of chitosan on perlite for enhancement of copper (SI) adsorption capacity” Journal of Hazardous Materials, 52 2, 826-837, 2008,

3 [Qd123[ Without wishing to be bound by theory, it is believed that the PZC value of 8.8 and the behavior of the surface charge of the MPCM is due to the modification of chitosan when cross-linked with g!utaraldehyde in the presence of add as a catalyst, which makes it amphoteric in nature in the pH range of 7.5 to 8.8.

[611124] The effect of pH on adsorption of molybdenum by MPCM was studied by varying the pH of the solution between 2 and 8 (FIG. 12). The pH of molybdenum solutions were first adjusted between 2 and 8 using either O. IN H₂SO or OH NaOH, and then MPCM was added. As the adsorption progressed, the pH of the solution increased slowly. No attempt was made to maintain a constant pH of the solution during the course of the experiment. The amount of molybdenum uptake at the equilibrium solution concentration is shown for each different initial pH of the solution in FIG, 12, The uptake of molybdenum by MPCM increased as the pH increased from 2 to 4, Although a maximum uptake was noted at a pH of 3, as the pH of the solution increased above 6, the uptake of molybdenum onto MPCM started to decrease. Accordingly, experiments were not conducted at a pH higher than the PZC of the MPCM sample.

[00125] In order to adsorb a metal Ion on an adsorbent from a solution the metal should form an ion in the solution. The types of ions formed in the solution and the degree of ionisation depends on the solution pH, In the case of MPCM, the main functional group responsible for metal son adsorption is the amine (-NI½) group. Depending on the solution pH, these amine groups can undergo profanation to NHb or (NFh-HbG)^, and the rate of protonation will depend on the solution pH. Therefore, the surface charge on the MPCM will determine the type of bond formed between the metal ion and the adsorbent surface, Depending on the solution pH, molybdenum in an aqueous solution can be hydrolyzed with the formation of various species. At relatively high and low pH values both the MoOf and various isopo!yanions (mainly Mt¾£¾ ) predominate. The MoO i ^" anion undergoes formation of many different polyanions in acidic solutions. See Guibal et ah, ‘‘Molybdenum Sorption by Cross-linked Chitosa Beads: Dynamic Studies”. Water Environment Research, 71 , I, 10-17, 1999; Merce et al„“Molybdenum (Vi) Binded to Humis and Mkrohumic Acid Models in Aqueous Solutions, Salicylic, 3-Nltrosalieulie, 5- Nitrosaiicylic and 3,5 Dinitrosalieyiic Acids, Part 2” J. Braz. Chem. Soc,, 17, 3, 482-490, 2906, it is reported that even if the polyanion is present in the solution the adsorption still occurs via MoOf formation. See iezlesrowski et a ,“Raman and Ultraviolet Spectroscopic Characterization of Molybdena on Alumina” The Journal od Physical Chemistry, 83, 9, 1 166- 1 173, 1979; El Shafel et ah,“Association of Molybdenum ionic Species with Alumina Surface,” Journal of Colloid and interface Science, 228, 105-1 13, 2000, The degradation of polyanions In the solution occurs due to an Increased local pH dose to the adsorbent surface.

1001261 As noted above, It was observed that the MPCM had a maximum adsorption capacity at a pH of around 3 front a solution of molybdenum Ions. Without wishing to be bound by theory', it is believed that the amine group of the MPCM has a lone pair of electrons from nitrogen, which primarily act as an active site for the formation of a complex with a metal ion. As mentioned earlier, at lower pH values, the amine group of MPCM undergoes protonallon, forming NH * leading to an Increased electrostatic attraction between NHs and sorbate anion. Since the surface of MPCM exhibits positive charge in the pH range of 2.5 to 7.5, the anionic molybdenum (Mo (VI)) Is presumably the major species being adsorbed by Coulo blc Interactions. As mentioned earlier, the pH of the solution was found to Increase after adsorption, which can be attributed to the H Ions released from the surface of the MPCM as the result of sorption of the molybdenum-containing anions from solution. In the case of MPCM, the protonation of NHh groups occurs at a rather low pH range. The fact that pH of the solution increased as the adsorption progressed suggests that Mo (VI) formed a covalent bond with a NH; group. [©©127] As the equilibrium pH increased from lower pH toward the pH at the PZC ipH]_¾c}_f the decreased percentage removal of Mo (V!) was attributed to the decreasing electrostatic attraction between the surface of MPCM and anionic Mo (VI) species. It may be noted that the PZC of MPCM is found to be shifted towards 4.5 in the presence of molybdenum ions, as compared to the PZC of MPCM without said ions (PIG. 1 1). The shift of PZC of MPCM towards lower pH indicates strong specific adsorption and inner-sphere surface eompiexation occurs due to molybdenum adsorption. Similar findings were reported by with the adsorption of molybdenum onto gibbslte, See Goldberg, S, “Competitive Adsorption of Molybdenum in the Presence of Phosphorus or Sulfur on Gibbsite,” Soil Science, 175, 3, 505- 1 30, 2010, Based on the surface charge analysis and pH studies, the reaction mechanisms that are occurs between the surface of MPCM and molybdenum species in solution are given in FIG. 13.

[Q0128] The equilibrium adsorption isotherm of molybdenum uptake on MPCM was determined at 298K temperature in the concentration range of 1 mmoie/L to 94 mmole/L. As mentioned in the previous section, the maximum adsorption capacity of molybdenum on MPCM occurs at a pH of 3. Therefore, the equilibrium isotherm experiments were carried out at a pH of 3, if not stated otherwise. The concentration profiles during molybdenum uptake by the MPCM from various concentrations of the solution shows that approximately 60% of molybdenum was adsorbed during th first 4 hours of an experimental run. The equilibrium was attained onotonica!ly at 24 hours in most of the experimental runs.

[©0129] The MPCM material contains amino groups that are available for characteristic coordination bonding with metal ions. Adsorption of etal ion, when pH dependent, may be described by the following one-site Langmuir equation. The effect of pH was incorporated by introducing a parameter "‘a” that is dependent on pH of the solution. The expression is given below:

~SH ~>~S + H⁺; Au S: surface concentration 3

-S + M «-*-SM km M: metal ion 4

q_m = maximum adsorption amount of metal ions (mmoSe/g)

where q is the adsorption capacity corresponding to metal ion concentration [M], q_m is the maximum adsorbed amount of molybdenum sons (mmol/g), [1-T] the hydrogen son concentration, Ku and Km are equilibrium concentration, Equation 5 was used to correlate the adsorption capacity of the MPCM. The equilibrium data for molybdenum could be correlated with the Langmuir equation within ± 5% of experimental valise. The constants of Equation 5 are obtained by non-linear regression of the experimental data and are given in Table 3. It was noted that Equation 5 represented the adsorption behavior of molybdenum on the MPCM adequately (Figure 14), The adsorption isotherm data obtained at pH 3 showed Type 1 behavior,

| 13tl| This suggests a monolayer adsorption of molybdenum on MPCM, Table 3 shows the maximum adsorption capacity of MPCM for Mo (VS), using Langmuir Equation (Equation 5). It was noted that the adsorption capacity of MPCM for molybdenum is approximately -6.25 mmol Mo/g of MPCM at 298K when the equilibrium concentration of Mo(VS) In the solution was 54,1 mmo!/L and the initial pH of the solution was 3.0 (FIG. 14). The NHj groups of MPCM are the main active sites for molybdenum adsorption. As can be seen from the FIG. 13, two Nfb groups will be necessary for the adsorption of one molybdenum ion, Other surface sites such as Ci OH or OH groups of MPCM might have been involved in adsorbing molybdenum at the solution pH of 3. The adsorption capacity of MPCM that was irradiated at 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.

Table 3. Estimated parameters for the Langmuir model

MPCM-I: Sample after irradiation at 50,000

⁶ⁱ⁵Co y-source.

[00131 j A column was used to study the adsorption of Mo (VI) with or without the presence of ions in the solution under dynamic conditions. Approximately 1 .125 gram of MPCM was used to make a 2.5 cm³ column with 0,5 cm inner diameter and 3.2 cm height. A flow rate of I mL/m snute was used during a run, The run was continued for 1 500 minutes, and samples at the bed out let were collected at a regular time intervals. The bed becomes saturated during this time period, as indicated by the outlet Mo (V!) concentration, When the inlet concentration was 5.21 mmole Mo {Vl)/L at pH 3 and the flow rate was 1 trsL/ minute through the column, molybdenum broke through the column after 320 bed volumes (FIG. 15a). Complete saturation of the column occurred after 500 bed volumes. Breakthrough curves were also obtained from a mixed solution containing 5.21 mmole Mo (VI) / L and 153.8 M NaC!/ L at pH 6.86 and 4,0, respectively (Figure 15 b). In both cases, the solution was passed through a similar size of column as mentioned earlier maintaining same bed height and flow rate. St was observed that column broke through quickly at 42 bed volume for the mixed solution with pH 6,86 however approximately 125 bed volumes were required to break through the column for the mixed solution with pH 4.0. It is important to note that the break through time for molybdenum solution with 153.8 mM NaCi/ L can be delayed, through the use of larger quantity of MPCM adsorbent and a longer column. The objective was to investigate the effect of inlet mixed solution pH on the breakthrough characteristic of Mo (VI) from the column, therefore, no attempt were made to determine the bed length to prolong the breakthrough time for mixed solution,

|00132] The long lived technetium (^¾¾Tc) was used to evaluate the performance of MPCM to adsorb technetium with and without the presence of other ions from an aqueous solution in the pH range of 3 to 1 1. Technetium is chemically inert and has multiple oxidation states ranging from I to VIS. The most dominant species of technetium that is found in aqueous waste streams is pertechnetate (TcQ^) See Gu et ah, Development of Novel Bifunctsonal Anion-Exchange Resin with improved Selectivity for Pertechnetate sorption from contaminated groundwater, Environ, Sci. Techno!., 34, 1075-1080, 2000, The adsorption of pertechnetate ( Tc0₄ ) from an aqueous solutions on MPCM was studied under batch equilibrium conditions following a process outlined elsewhere. The effect of pH on technetium adsorption onto MPCM w^ras evaluated over the pH range of 3 to 1 1 using a solution containing of 0, 1 1 pmole technetium /L with and without the presence of 0,9% NaCi, respectively, While studying the effect of pH on the adsorption capacity, the initial pH of the solutions 'as adjusted to a desired value by adding either 0.1 SV1 HCI or 0,1 M NaOH, The pH of the solution was not controlled during the adsorption process. Following the adsorption experiments, the solutions were filtered and the activity of "Tc in the filtrate, which was collected in a vial at a predetermined time, was evaluated using a liquid- scintillation counter (Packard Triearh 290GTR), The amount of technetium adsorbed onto MPCM was determined following the Equation 2.

[00133] Table 4 shows that the adsorption of technetium onto MPCM is pH independent in the solution pH range of 3 to 1 1 , It was observed that approximately 95% of 1 mM technetium/L of solution was adsorbed onto PCM in the pH range of 3 to I I , whereas the technetium removal was reduced to 56% in present of 0,9% NaCI over the pH range of 3 to I I . As it was mentioned earlier, MPCM shows positive charge in the pH range of 3 to 7,5. FUR spectrum of MPCM confirms the presence of --NH , CHQH, and CHbQH groups on PCM surface (FIG. 4). It was assumed that the positive charge occurs due to protonation of the surface sites of MPCM in the pH range of 3 to 7.5 and technetium undergoes covalent bonding with the positive surface sites of MPCM In the ease of 0,9% HaCi in solution, the adsorption capacity of MPCM for technetium was reduced as the periechnetate ions had to compete with the chloride ions in solution, Moreover, the uptake of technetium in the pH range of 9 to 1 1 in the presence of 0.9% NaCI solution may correspond to an ion-exchange reaction that occurs at this pH range. The result shown in Table 4 confirms that MPCM has strong affinity for periechnetate ion from aqueous solutions.

Table 4. Adsorption of technetium on to MPCM at different pH

[001341 MPCM was also used to adsorb Mo (VI) and Te{VlS) simultaneously from a mixed solution containing 1 mmole of Mo(Vl)/L and O.I i pmole of perteehnetate/L with or without the presence of 0,9% NaCI. MPCM was found to adsorb molybdenum and technetium simultaneously from the solution at solution pH 3. It was observed that approximately 95% of 0.1 I p oie periechnetate was adsorbed onto MPCM surface, whereas 99% of 1 mmole molybdenum was adsorbed from the mixed solution, in the presence of molybdenum fA/oO ") in the solution, pertechnetate (7T£L^'"} had to compete for the positive surface sites of MPCM. In another attempt, the adsorption of technetium onto MPCM was studied from a mixed solution containing 153,8 mmole NaCi/L, I mmole Mo (Vi) /L of and O. l l pmoie pertechnetate/L, Table 5 shows that molybdenum (M Or~) was adsorbed preferentially on to the MPCM surface, whereas the adsorption of pertechnetate (rcfL^") was reduced to 55% of 0.1 I pmole teehnetium/L in the mixed solution. It is assumed that in the presence of 0.9% NaC!, the sorption of pertechnetate (G cfL^“) onto MPCM surface was reduced due to the competition for surface sites with chloride ions at solution pH 3. In another attempt, a column with 1 cm inner diameter was used to study the pertechnetate adsorption onto MPCM. The column was prepared with MPCM that was loaded initially with Mo (VI), Batch equilibrium process was used to adsorb 6,25 mmole Mo (VI)/ g MPCM at 298 K when the equilibrium concentration of Mo (VI) in the solution was 54 mmolc/L and the initial pH of the solution was 3,0. Approximately 1.125 gram of Mo (Vi) loaded MPCM was used to prepare a 2.5 cm³ bed. A saline (0 9% NaCl) solution spiked with 0.25 mM pertechnetate/L was passed through the column using a peristaltic pump at a flow rate of l mL mirs during the run.

Table 5. Adsorption of pertechnetate and molybdenum on to MPCM from a mixed solution

|00!3S] FIG 16 shows that the pertechnetate anion has affinity towards available surface sites of MPCM in the presence of molybdenum (MoOr^~) anion. It was observed that at 10 bed volumes, approximately 15% of the inlet concentration of pertechnetate was eluted with saline (0.9% NaCI) solution. H may be noted that approximately 60% of the inlet perleehnetaie concentration was obtained in the eluent that was collected at 20 bed volumes (FIG. 15). The column reaches saturation fairly quickly for technetium while an additional 40 bed-volume of technetium spiked saline solution w¾s passed through the column. After the column reached its saturation for technetium, more than 95% of the technetium fed to the column was collected at the column outlet as eluent. T he objective of this study was to investigate the maximum amount of pertechneiate (fc0 ) uptake onto MPCM loaded with 6,25 uiM of Mo (VI)/ gram of MPCM, No attempts were made to determine the bed length to reduce the pertechneiate release from the Mo (VS) loaded MPCM bed.

|IMI136| Although batch and column studies show that MPCM exhibited excellent adsorption capacity for Tc(VH), Us removal from the bed was challenging. A technetium loaded MPCM bed was prepared In a column to study the desorption of technetium from the MPCM sample. The adsorption of technetium onto MPCM was conducted under hatch equilibrium conditions. It was observed that approximately 0, 12pM of "Te was adsorbed per gram of MPCM from a "Te concentration of 0,4SpM/L solution at 298 temperature. For ^¾¾Tc desorption studies, about 1 ,125 gram of MPCM containing 0.12mM of ^¾¾Te / gram of MPCM was used to prepare the column. Pertechneiate is soluble in water; therefore, deionized water was used to regenerate technetium from the column, H was observed that only 1% of technetium was desorbed from the MPCM bed using 10 bed volumes of water. Preliminary studies show that complete recovery of technetium from the MPCM is challenging even using when different concentrations of NaCI solution, St was observed that approximately 50 bed volumes of 1 ,5% NaC! was required to regenerate 10% of^wTe from the column. Similar amounts of low concentration acid solutions (< I ) of HCi, H₂SQ4, and HNO₃, were also used, without any significant regeneration. In another attempt, the MPCM sorbent was oxidized with different concentrations of potassium permanganate or hydrogen peroxide, to study the effect of oxidation on adsorptson/desorption of technetium on to the oxidized MPCM sorbent.

EXAMPLE 2

|00137] In another embodiment, MPCM was oxidised with different concentrations of hydrogen peroxide with or without the presence of transition metal catalysts. Temperature was also varied. The oxidation studies of MPCM with hydrogen peroxide were performed to determine whether controlled oxidation alone would improve technetium recovery from the technetium loaded MPCM, The concentration of hydrogen peroxide was varied from !% to 5%, Batch technique was used to adsorb technetium onto oxidized MPCM, The regeneration of technetium from the oxidized MPCM was conducted in a column. The column was prepared with 0, 12 pmoie of ^?9Te / gram of oxidized MPCM. The column was regenerated to desorb technetium from the oxidized MPCM using 0,9% NaCI solution. It was observed that the recovery of technetium was not as high as was desired, since 10 to 17% of available technetium was recovered from the oxidized MPCM bed (Table 6), Moreover, the adsorption of Mo (VI) onto peroxide-oxidized MPCM reduced to 4,6 m ole/g compared to 6,25 mmoic/g adsorbed by non-oxidized MPCM.

Table 6. Desorption "Tc from oxidized MPCM using 0.9% NaCI solution

EXAMPLE 3

[09!3S] MPCM was also oxidised using potassium permanganate n solution. The concentration of potassium permanganate in the solution and the oxidation time was determined based on trial and error. The concentrations of potassium permanganate and the pH of the solution were varied from 0.1% to 5% and 3 to 1 1, respectively. The oxidation time was varied from 30 minutes to 24 hours. The surface charge analysis of oxidized and non-oxidized MPCM loaded with Mo (VI) was also performed to elucidate the perteehnetate (T cCA ) adsorption pattern on oxidized MPCM.

[00139] It was observed that permanganate solution containing 0,04 mmole of Mn /L of solution at the pH range of 3 to 4.5 and 12 hours time period was sufficient to oxidize MPCM partially to facilitate maximum uptake of molybdenum and simultaneous release of technetium from the MPCM sorbent. The performance of the oxidized MPCM was evaluated for molybdenum adsorption from aqueous solutions using batch technique, It was noted that oxidized MPCM can adsorb 6.25 mmole of Mo (VI)/ g of MPCM at 298K when the equilibrium concentration Mo (VI) in the solution was 54 oi/L at pH 3,0.

[00140] In another attempt, two separate columns were prepared using oxidized MPCM and oxidized MPCM that was loaded with 6.25 mmol of Mo(Vl)/ g„ respectively. A 0.9% NaO solution spiked with about 0,1 1 pmole Perteehnetate {7Y£T^”)/L of solution was passed through both columns at a i L/min flow rate, it was interesting to note that perteehnetate (TcQ^) did not adsorb onto oxidized MPCM with or without Mo (VI) loading and approximately 90% of perteehnetate (TcO/ ) in the solution passed through both types of columns as an eluent, The results confirm that perteehnetate (G OJ^") did not adsorb onto both oxidized MPCM and MPCM loaded with Mo (VI). The objective of this work was to maximize Mo (Vi) uptake and enhance technetium release simultaneously from the MPCM surface sites, [00I4I I MPCM shows great afflrsit for both Mo (VI) and Tc(Vf l) from the aqueous solution. The surface charge of Mo (VI) loaded MPCM revealed (FIG, 1 1 ) Shat Mo

(VI) was adsorbed onto MPCM through an inner-sphere surface completion reaction. It may be noted that Mo (Vi) loaded MPCM exhibited positive charge in the pH range of 3 to 4,5; therefore, anionic pertechnetate presumably formed covalent bonds with the available positive surface sites. Interestingly, the adsorption of pertechnetate on to MPCM is approximately 55% from a solution containing 0.9% NaCi at the pH range 3 to 8 (Table 4). Almost 95% of 1 mmole pertechnetate was adsorbed onto MPCM In the presence of 1 mmole Mo (VI) In the solution. This confirms that pertechnetate (TcQ ~) was adsorbed onto MPCM surface sites,

jO0!42| The permanganate ion is ambiphilic in nature, In acidic solution, n

(VII) ions of potassium permanganate change to possible intermediate products such as Mn (VI), Mn (V), Mu (IV), and Mn (HI), which are ultimately reduced to Mn (II). See Dash et a!,,“Oxidation by Permanganate: Synthetic and mechanistic aspects'⁵ Tetrahedron, 65. 707- 739, 2009, The permanganate { MnO ) content in the potassium permanganate is reported to be the reactive oxidizing species for add catalyzed permanganate oxidation of chitosan. See Ahmed et ah,“Kinetics of Oxidation of Chitosan polysaccharide by Permanganate Ion in Aqueous Perchlorate solutions’⁵ Journal of Chemical Research, v 2003, n 4, p, 182 - 183, 2003. In an acidic medium, the possible reactions between the MnO ton and H are as follows:

|0D143] Due to protonation of the M?£¾ ton In the acidic solution, the

HMhO_L species cart be formed, which is also a powerful oxidant. See Sayyed et al,“Kinetic and Mechanistic Study of Oxidation of Ester by KMnCb” International Journal of ChemTecb Research, y 2, n I, p 242-249, 2010 The formation of colloidal MnCh is possible due to the reaction of MnQ_A with H~ and depending on the acidity of the solution which may further undergo reaction with H~ to produce Mi^2* in solution. Ahmed et a!, 2002 reported permanganate oxidation of chitosars as an acid catalyzed reaction that led to formation of diketo-acid derivatives of chltosan. See Ahmed et ah,“Kinetics of Oxidation of Chitosan polysaccharide by Permanganate Ion in Aqueous Perchlorate solutions” Journal of Chemical Research, v 2003, n 4, p. 182 · I S3, 2003.

(0Q144] In add catalyzed permanganate oxidation of MPCM. permanganate (¾/ϊ?ί7~) Ion ears be considered as the reactive oxidizing agent. The effect of permanganate oxidation on MPCM for the adsorption and release of Mo (Vi) and Tc (VII), simultaneously, from the oxidized MPCM surface was evaluated by the surface charge analysis of the MPCM sample. The oxidation of MPCM by potassium permanganate changes its adsorption selectivity from aqueous solution. FIG, 17 shows the surface charge pattern for Mo (VI) loaded MPCM sample with or without oxidization. In the case of non-oxidlzed MPCM sample loaded with Mo (VI), the protonation of the surface appeared to be increased gradually at the pH range of 4,5 to 3, Therefore, at this pH range, the formation of covalent bonding by pertechnetate with the positive surface sites of Mo loaded MPCM surface is possible. At pH < 2,9, the difference between the initial pH and pH after the equilibration time for MPCM loaded with Mo (VI) sample was not significant, suggesting complete protonation of the MPCM sample.

|Q0145| The surface charge of Mo (VI) loaded oxidized MPCM shows almost zero charge in the pH range of 3 to 4,5, compared to the Mo (VI) loaded onto the non- oxidized MPCM sample (FIG, 17), in the acidic pH range from 3 to 4.5, the surface functional groups of nors-oxidized MPCM show positive charge which may further undergo reaction with MnOl during the oxidation reaction. It is assumed that the manganic { Mn0₄ } ion entered into the porous matrix of MPCM and partially oxidized the positive surface functional groups by donating electrons followed by reduction to M«^z+ ion in the solution. In addition, formation of colloidal manganese in the solution was controlled by controlling the solution pH In the range of 3 to 4,5, more specifically at pH 4. Moreover the ratio of Mn^2* ion to positive surface sites of MPCM favors further adsorption of Mnⁱ⁺ onto MPCM surface. It was observed from the both batch and column studies that technetium did not adsorb on to Mo (VI) loaded oxidized MPCM whereas k shows a strong affinity for the Mo (VI) loaded non-oxidized MPCM sample. This indicates that the lack of a positive charge on the Mo (VI) loaded oxidized MPCM surface did not attract technetium to form a covalent bond compared with the surface of non-oxidized MPCM loaded with Mo (VI). it is interesting to note that technetium did not adsorb onto oxidized MPCM whereas almost 95% of 1 mmole solution of technetium was adsorbed onto non-oxidized MPCM. This confirms that technetium adsorbed onto the surface of non-oxidized MPCM and was not adsorbed on to the oxidized MPCM through covalent bonding.

[Q0146] Equilibrium batch adsorption studies were carried out by exposing the oxidized MPCM to 1% Mo(Vl) solution that was spiked with 5.0 ntL of "Mo (2 mCi/ L}, Initially 1% molybdenum was prepared by dissolving 4.5 mL of ammonium hydroxide and 1.5 g of MQG_J in 95 mL of deionized water. The mixture was kept under stirring until jVtoCb completely dissolved in solution. A solution containing 5.0 mL of "Mo (2 mCi "Mo/mL) was mixed thoroughly with 97.5 mL of 1% molybdenum solution. The pH of the spiked solution was adjusted to 3 using either 0. IN HCS or NaOH solution. The final specific activity ofthe Mo (VS) in the solution was 78.12 pCi/ L.

|0QI47| About 0.5 gram of he oxidized MPCM was added to a 125 mL plastic vial containing 50 L of spiked solution. The solution was then kept on the shaker ( 160 rpm) for 3 hrs at 25±1 *€. Another set of similar experiments was also performed to duplicate the data. After 3 hrs, the final pH was recorded for the solution, and the solution was centrifuged for 5 minutes at 3000 rpm in order to separate the MPCM from the supernatant solution. The MPCM loaded with Mo (VI) was then rinsed with deionized water couple times to remove any adhered Mo (VI) from its surface. The MPCM ioaded with Mo (VS) arsd the supernatant and rinsed solutions were analyzed for molybdenum uptake using a dose calibrator, and a ICP-MS. St was observed that at equilibrium, the oxidized MPCM had a capacity of 2.47 mmole Mo/g of MPCM where 1300 pCi of activity are from the spiked "Mo.

]fl0148] The activity for "Mo and "^mTe was evaluated using both a dose calibrator and a gamma spectrometer, The dose calibrator (Atemlab 400) is equipped with a small lead sample vessel that effectively shielded of ^93raTe gammas while allowing the majority of "Mo gammas to pass through the shield and Into the detector. Therefore, readings taken while the sample is contained within the shielded vessel is assigned solely to " o activity. Readings taken without the shield are the sum of both " o and "^mTe activities.

[00149] Following the batch adsorption run, the MPCM loaded with both ^3SMo and "Mo was transferred to a column (0.5 cm* 3.2 cm with poiytetrafluoroethylene (PTFE) frit at the bottom). Two ends of the column were closed with silicon rubbe septum. The column was thoroughly rinsed with de-ionized water to remove any molybdenum solution on the surface of the MPCM, The rinsed sample was collected from the column using evacuated vials. The column was eluted with saline (0.9% NaCi) solution after allowing it maximum time required to bui!d-up the daughter product ^9¾BTc from the decay of the remaining "Mo in the column. The column was eluted with 9 mL saline solution that was collected subsequently in 3 individual evacuated vials of 3 mL each. The eluate was obtained from the column at predetermined time intervals. The eluate from each collection was analyzed for

53 molybdenum and manganese released from tSie column using quadruple inductively coupled plasma mass spectrometry (!CP-MS) with an external calibrator. The activity related to periechnetate or "Mo was evaluated using dose calibrator and gamma spectroscopy.

]CMI 15 | FIG. 18 shows the elution profile of the column consisting of 0,5 gram of MPCM loaded with 2.47 mmole of Mo (VI) /gram of oxidized MPC where 1300 m€ΐ activity is from adsorbed "Mo. The column started eluting with saline (0.9% aC!) solution on the day after the column was prepared and the elution was continued over the period of 8 days. A note Is that the first set of elution (Elution 1) was performed at 8 hours after the column was prepared in order to verify the desorption behavior of "^wTc from the MPCM column, The rest of the elutions, number 2 to 8, were performed at 24 hours intervals except elution number 5 were performed at least 45 hours after the elution number 4, The elution efficiency for the daughter product "^t!,Tc from the column was found to be within the range of 75 to 90% (FIG. 18). In elution S, as shown in FIG, 18, more than 80% of the activity due to "^mTc is obtained within 9 mL of saline (0.9% NaCI) in where 62% of the available "Tc activity eluted in first 3 L volume of normal saline. The second elution was collected at 24 hours after the first elution and shows that the "^mTc activity in the column ranged from 70% to 90% and can be recovered using 3 to 9 mL of saline solution. In all the cases, the eluate was dear, and the pH was in the range of 6 to 7. The column was continuously eluted over the period of 8 days with an average -82 of the whole ""Tc eluted from the column.

[00151] FIG, 19 shows the percentage of "^raTc and Mo (VI) released from the column over the period of 8 days. The concentration of the Mo ( VI) in the eluates was within the range of 1% to 3% of the 6.25 mmole Mo (Vi)/ gram of MPCM in the column. The process of capturing any molybdenum leakage from the column by passing it through add catalyzed MPCM is possible as shown in FIG, 15 thus reducing the Mo (VI) and Mn(Vli) concentrations in the eluent to extremely low levels. Another way of controlling molybdenum

S I leakage from the column can be achieved by controlling the pH of the saline (0,9% NaCl) solution within the range of 4 to 4.5 (FIG. 15). in that ease, an additional guard column will not be necessary to control the leakage of Mo (VI) from the column.

EXAMPLE 4

|0¾1S2| Production of "Mo via neutron capture method draws attention as an alternative of fission derived " o due to non-proliferation issues. The "Mo produced by the neutron activation of natural molybdenum would provide a less complex, less expensive, and more practical route for indigenous production and use o ^99mTc, However, it is evident that the specific activities produce by the neutron capture method are not sufficiently high for the preparation of small chromatographic generators. This limitation, however, ears be overcome by the use of adsorbent such as MPCM, which has higher adsorption capacity for molybdenum, it is demonstrated that MPCM is capable of adsorbing more than 6.25 mmole Mo (Vi)/ gram (600 mg Mo {VI)/g of MPCM) from an aqueous solution at pH 3, which is also applicable to "Mo obtained easily by the (n, y) reaction of natural molybdenum. The generator in this case consists of MPCM loaded ^¾Mo thus combines the performances of the chromatographic generator and the use of (n, y) "Mo, In case of using as an adsorbent in "^mTc/"Mo generator, the MPCM is able to hold up to 60 wl% of its body weight, in comparison with only 0.2 wt% in the alumina. The potential for MPCM as an absorbent for the preparation of the "Mo/"^mTc generator has been explored using 1% Mo (Vi) solution spiked with "Mo (2 Ci/mL). It was observed that MPCM adsorbed Mo (VI) spiked with "Mo as per its demonstrated capacity from an aqueous solution at pH 3. It was also observed that "^mTe, which was the decay product of "Mo, was eluted with normal (0,9%) saline solution to yield more than 80% elution, A typical "^mTc/"Mo generator preparation flow sheet based on MPCM as an adsorbent is given in Figure 20. EXAMPLE 5

|00I53f In an attempt to maximize Mo (VI) uptake arid enhance technetium release from the column prepared using molybdenum loaded MPCM resin, MPCM resin was oxidized using sodium hypochlorite (NaClQ2) and sodium chlorite ( aGCI), respectively. The concentration of sodium chlorite or sodium hypochlorite in the solution and the oxidation time was determined based on trial and error. The concentrations of sodium chlorite and the pH of the solution were varied from i mmoie/L to 10 mmole/t and 3 to 1 i, respectively. The oxidation of MPCM by either sodium chlorite or sodium hypochlorite solution was carried out at a solid to liquid ratio of 1 : 100, The oxidation time was varied from 30 minutes to 24 hours. For both sodium chlorite and sodium hypochlorite, it was observed that solution containing -0.02% chlorine, calculated as C at a pH range of 3 to 4.5 and an oxidation time of 2 hours was sufficient to oxidize MPCM partially to facilitate maximum uptake of molybdenum and also release of technetium from the MPCM sorbent. The MPCM resins that were partially oxidized by sodium chlorite and sodium hypochlorite are denoted as MPCM- CIOs and MPCM-OCI, respectively, herein. The performance of the MPCM-ClCb and MPCM-GO was evaluated for molybdenum adsorption from aqueous solutions using batch techniques. It was noted that oxidized PCM can adsorb approximately 6,25 M {-600 mg) of Mo (VI) per g of oxidized MPCM at 298 when the equilibrium concentration Mo (VI) In the solution was 54 m oi/L at pH 3.0.

(O0154| A surface charge analysis of molybdenum loaded non-oxidized MPCM and molybdenum loaded MPCM-C Gi was carried out using procedures described above. Similar surface charge experiments were also performed with molybdenum loaded MPCM- OCI and the data was compared with the surface charge of molybdenum loaded non-oxidized MPCM resin. The surface charge data of molybdenum loaded MPCM-CICh artd MPCM-OCI

5i shows a similar pattern to that of molybdenum loaded PCM that was oxidized by potassium permanganate.

|001 SS| in order to evaluate Te-99 uptake capacity, two separate columns were prepared using molybdenum loaded PCM-CICh and MPCM-OCI, respectively. For comparison, Te-99 pass through tests with both of these oxidized MPCM resins were performed following the procedures described above. The results confirmed that pertechnetate (TcGy } did not adsorb onto both MPCM-CICh and MPCM-OC1 loaded with Mo (VI), Table 7 shows the comparison of the effects of different oxidizers on technetium release from a column prepared with oxidized MPCM, The oxidized MPCM resins, as shown in Table 7, were exposed to 1 % molybdenum solution that was spiked with molybdenum-99. The activity of molybdenum-99 was varied from 45 mC to 1.39 Ci (at the end of srradiation, or EOl), respectively. The molybdenum loaded MPCM resins that were oxidized by different oxidizers were used to prepare respective chromatographic columns. The columns were then flushed with saline solution and the data are shown in Table ?,

[00156] Technetium release was almost 100% from the column when the initial activity of Mo-99 in the column was approximately 45 mCi (Table 7). The release of technetium from the column was comparatively very low for all oxidizing agents when Mo- 99 with higher specific activity was used in the column. Without wishing to be bound by theory, it is believed that, at higher activity, technetium reduced from Tc(VlI) to Te(IV) and the reduced anionic pertechnetate presumably formed covalent bonds with the free surface sites of MPCM resin. The release of technetium from the column was approximately 10% when moiybdenum-99 with activity of 9GQmCi was loaded onto MPCM sample that was oxidized with 31 niM potassium permanganate (Table 7). This combination also released more manganese in the eluent compared to the MPCM resin that was oxidized with 6.3 mM of potassium permanganate. In the case of higher activity of Mo-99 (1.39 Ci at EOl) in the column, a small increase of the percentage of technetium released from the column was observed for the MPCM-CICh an MPCM -CIO resins compared to the resins that were oxidized by potassium permanganate or hydrogen peroxide (Table 7).

Table 7: Micro-porous composite resin (MPCM) resin treatment with different oxidizer

|99157] At higher specific activity (L39C! at E01) of molybdenum in the column, the release of technetium from the column was reduced significantly compared to the column prepared by MPCM resin loaded with low specific activity molybdenum-99. Without wishing to be bound by theory, it is believed that at higher activity, the oxidation state of metal ions that are present in the column may change: thus reducing technetium release from the column. St is believed that the presence of oxidising agent in the molybdenum solution could keep the MPCM resin and molybdenum the solution in oxidi ed state throughout the adsorption cycle, which may facilitate technetium release from the column. Furthermore, addition of oxidizing agent in the eluent saline solution was also considered in order to enhance further technetium-99 release from the molybdenum loaded oxidized MPCM column

[60158] The MPCM -CIOs and MPCM-OCI resins were further studied to evaluate their potential for molybdenum adsorption in presence of different concentrations of oxidizing agent in the solution. The adsorption study was carried out for 24 hours using different concentrations of sodium chlorite and sodium hypochlorite (5 mM to 50 mM) which were spiked with t % molybdenum in solution (prepared from molybdenum salt, without radioactive molybdenum (Mo-99)). The molybdenum solution pH was initially adjusted at ·_" 3.0 for all the experiments. The samples were collected at different intervals and were analyzed for molybdenum uptake onto the resin. Table 8 shows that, in the presence of sodium chlorite or sodium hypochlorite in the solution, the molybdenum uptake capacity of the oxidized MPCM resin was in the range of 5.21 mM (500 mg/g) to 6.25 mM (600 mg/g) of oxidized MPCM. Molybdenum started precipitating out slowly in the solution alter 12 hours of exposure when the oxidizer concentration in the solution was 45 mM or higher. No molybdenum precipitation in the solution was observed for the solution in which the concentrations of either sodium chlorite or sodium hypochlorite were in the range of 5 mM to

40 mM. Molybdenum did not precipitate in the solution during first 4 hours of the exposure for any concentration of sodium hypochlorite that was used in this study.

Table 8: Adsorption cycle { ! gram oxidized MPCM in 1 % Molybdenum solution and exposure time 24h at oH-3.01,

s§ [OT159] Molybdenum uptake was found to be fairly consistent onto MPCfVl· CICb in presence of all concentrations of sodium hypochlorite in the 1% molybdenum solution (Table 8). Compared to the data obtained From oxidizer-free molybdenum solution, the uptake of molybdenum onto MPCM-ClCb was approximately 6.25 mM/g from a 1 % molybdenum solution containing of 25 mM of sodium hypochlorite fWaOCI) in the solution (Table 8). This suggests that presence of hypochlorite in the molybdenum solution did not affect molybdenum adsorption substantially onto tV!PCM resin that was partially oxidized by sodium chlorite.

[TO!dbJ Therefore, MPCIVl-CtCfe was considered in this attempt to adsorb molybdenum in presence of different concentrations of sodium hypochlorite (NaOCI) as oxidizer in the 1% Mo solution. The molybdenum loaded MPCM-CIO2 was then used to prepare a chromatographic column. Sodium chlorite and sodium hypochlorite were also mixed with saline solution in order to investigate their oxidizing effects on the release of both technetium and molybdenum from the column. The columns were then Slushed with a saline solution mixed with 5 mM concentration of sodium chlorite and sodium hypochlorite, respectively, at pH 4. The e!uaie mixture was further spiked with Te-99 (stoichlomeiricaliy equivalent to CI ofTc-99m per 10 mL) before being passed through the column.

(00161] More than 99% of Te-99 passed through the column in the presence of either sodium chlorite or sodium hypochlorite as oxidizing agent in the eluent without being adsorbed in the column (Table 9). The release of molybdenum from the column during elution with the saline solution mixed with sodium hypochlorite was similar to the column eluted with saline solution mixed with sodium chlorite (Table 9), For instance, columns prepared with MPCM~CIC¾ adsorbed molybdenum from a solution containing 1 % molybdenum and 23mM sodium hypochlorite, were flushed with 5 M sodium chlorite and sodium hypochlorite, respectively (Table 9). in the case of saline with sodium chlorite, the release of molybdenum was found to be approximately 2% of the 6.25 inM adsorbed molybdenum onto MPCM~CK¾ that was used to prepare the column, whereas molybdenum release was loured to be approximately 7.5% from a similar column that was eluted with sodium hypochlorite mixed saline solution as shown in Table 9, H was obvious from this study that fvfPCM-CICb is capable of adsorbing approximately 6.25 mM of molybdenum from a solution containing 1% molybdenum and 25 mM of sodium hypochlorite, In the case of a chromatographic column prepared using molybdenum loaded MPCM-CIGj and then eluted with Te-99 spiked saline mixed with sodium chlorite, it was found that this system was capable of holding maximum molybdenum and also releasing maximum Tc-99 from the column.

Table 9: Typical oxidizer concentration (5 mM) in the elution solution and related metal ions release from the column.

The effect of different sodium chlorite concentration in the eluent for releasing molybdenum and technetium from the column was further investigated. Columns were prepared with MPC -C!Cfe that adsorbed molybdenum from a solution containing 1 % molybdenum and 25 M sodium hypochlorite. The columns were then flushed with saline mixed with different concentration of sodium chlorite, respectively (Table 10). The concentration of sodium chlorite in the saline was in the range of 5 mM to 20 mM, The eluent mixtures were further spiked with Tc-99 (stoichiometricaily equivalent to ! C 1 of Tc~99m per 10 L) before being passed through the column. It was observed that more than 99% of technetium-99 passed through the column in presence of sodium chlorite as oxidizing agent (5mM to 20 mM concentration) in the eluent without being adsorbed in the column (Table 10). The amount of molybdenum release 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 S Svf and 20 mM, respectively. This suggests that a guard column is desirable in order to obtain molybdenum-free technetium in the eluent solution.

Table 10, Effect of sodium chlorite concentration in the eluent on the release of technetium and molybdenum from column prepared using molybdenum loaded MPQVTCiO .

EXAMPLE 6

[ 0163| The potential of MPCM-CIO resin as an adsorbent for the preparation of "Mo/^Tc generator was evaluated by exposing it to 1 % neutron-captured produced molybdenum solution with an activity of 13 9 mCi/mL irradiated at MURR (the University of Missouri Research Reactor, USA), A similar experiment was also carried out at POLATOM using 1% natural molybdenum solution that was spiked with fission molybdenum (- 1 ,89 Cl ^y9Mo/g Mo). Batch adsorption experiments for molybdenum uptake on MP€M~ClG resin were carried out at room temperature while the solution pH for both experiments was initially about 3.0, Molybdenum uptake onto the resin for both experiments was approximately 60% of the available molybdenum in the solution. In each experiment, a "Mo/^Tc generator consisting of a 6 mL column containing MPC -CICb resin loaded with "Mo was prepared ^99mTc, the decay product of ⁹⁹Mo_s was eluted with saline solution (0.9% NaCI) mixed with sodium chlorite as an oxidizing agent. Table i I shows the elution performance of a typical generator that was prepared by exposing !-g M PCM-Ci(¼ resin to 100 mL of 1.390 "Mo in " 1% total molybdenum solution at an initial pH of -2 8. Analysis of the activity distribution indicated a Mo adsorption efficiency of 63 4%. The time of exposure of MPCM-CICb resin to molybdenum solution was 24 hours for these experiments. Following the adsorption cycle, the resin was thoroughly rinsed with de-kmked water to remove any adhered molybdenum from the surface.

Table I i ; Concentration of sodium chlorite in the eluent vs, ^9teTc release.

From Table 1 1 , the amount of Tc-99m released from the column increases with the increase of the concentration of sodium chlorite in the eluent solution. Approximately 20 mM of sodium chlorite concentration in the eluent saline solution at pH 4.0 appears to be sufficient to remove more than 95% of the Tc~99m from the column when the column initial activity was approximately ICi,

0916Si The Tc-99m radioisotope, in the form of an intermediate solution, is then passed through a guard column with alumina as an adsorbent. The elution data were collected for three consecutive days and the data revealed that the elution contains a yield of > 90% of the theoretical amount of available front the generator. The ^¾¥Mo in the eluent was less than 0, 15 m€ΐ of "Mo per mCi of^“Te. The eluent solution was further subjected to treatment with either 1 M sodium thiosulfate or sodium sulfite to neutralize the presence of oxidizer In the solution. The use of sodium sulfite can efficiently neutralize the oxidizer that may present in the final eluent. Typical composition of the eluent obtained from these experiments is given in Table 12,

Table 12. Typical composition of the final eluent

EXAMPLE 7

[00166] Addition of potassium di-ehromate (approximately 200 g chromate) and 5% cerium oxide were also investigated as oxidizers with saline solution that was used to Hush a molybdenum loaded MPCM-CiOz column with some success. In the case of potassium dichromate or cerium oxide in the saline as eluent, Te-99 release from the column prepared from molybdenum loaded MPCM-CiCh resin was approximately >75%. A substantial amount of chromium or cerium was present In the final eluent solution which indicates a further requirement of a guard column unit to obtain oxidizer free technetium in the final eluent,

EXAMPLE 8

[O01b7| The effect of temperature and solid to liquid ratio in presence of oxidizing agent (sodium hypochlorite) in the solution on molybdenum uptake onto MPC3V1- Cl0₂ resin were investigated. Batch studies were performed at predetermined different temperatures following the procedures previously mentioned. Far each experiment, approximately S gram of MPCM-CSCb resin was exposed to 100 mL of 1% molybdenum solution with the presence of oxidker (25 mM of NaOCI) for 4 hours at pH -3.0 (data are not shown). Preliminary data as shown in Figure 21 reveals that the molybdenum uptake on to the M PC -CICh resin at solution temperature ranging from 25^aC (298K) to 70°C (343K) was varied only slightly (ranging from 5.38 mM to 5.53 mM Mo(Vl) / gram of MPCM-CICb resin), in most eases, approximately 50% of the available molybdenum in the solution was adsorbed on to MPQVl-OGz resin during the first 0,5 hours of operation without any precipitation, followed by slow movement toward equilibrium.

[^Q0168j The heat of adsorption at different loadings of molybdenum on oxidized MPCM is shown in Figure 22. The heat of adsorption of molybdenum decreased with the increase of loading that can be attributed to heterogeneity of the surface and multi- layer coverage. The heat of adsorption approached the Integra! heat of adsorption (DH value) at higher loading. Without wishing to be bound by any theory, it is believed that the surface became saturated with molybdenum and the heat of adsorption was approaching its equilibrium value. The initial decrease in the values of heat of adsorption cun be attributed to the heterogeneity of the surface and the multilayer coverage. The subsequent increase in the heat of adsorption may be attributed to lateral interactions between the adsorbed molybdenum ions, which are known to form complex molecules on a solid surface. It was expected that adsorption surface sites of the resin will be homogeneous energetically and. therefore, a constant heat of adsorption should be obtained. However, the resin surface seems to become heterogeneous energetically, because of the micro-porosity of the surface.

{00169} Batch studies were carried out varying the solid to liquid ratio in the presence of 25 mM sodium hypochlorite as an oxidizer in \¾ molybdenum solution at 25"C (298K), Almost 95% of the available molybdenum from a 1 % solution was adsorbed on to the MPCM-CICb resin within 1 ,0 hour of exposure when the solid to liquid ratio was 2: 100 (2 gram MPCM-CiQj ie 100 mL of a 1% molybdenum solution that was mixed with 25 mlVl sodium hypochlorite). This ratio is found to be the optimum adsorbent dose only for molybdenum uptake on to MPCM~C1C¾ in presence of 25 mM sodium hypochlorite in 1 % molybdenum solution, In the case of non-oxidized MPCM, using the same solid to liquid ratio and exposure time, the uptake of molybdenum was almost 35% less compared to the oxidized-MPCM (SVlPCM-CICh) resin. The surface charge modification of MPCM by oxidation and higher solid to liquid ratio in the process appear to be at least part of the reason for this phenomenon.

EXAMPLE 9

| f)170| Initial experimental data showed that oxidized- PCM resin is capable of adsorbing approximately 50 to 60% of available molybdenum from solution after 24 hours of exposure, It is also estimated that almost 28% of the "Mo activity decays away during 24 hours of the adsorption cycle. Moreover, another 10 to 15% of "Mo activity losses incurred doe to processing and handling of the generator. Figure 23 shows experimental data of a 0,5 Ci (at the time elution) "Mo/"^mTc generator described above that typically requires approximately 1.6 to I Ci "Mo (EOl) from the very beginning.

[1)0171] However the batch experiments suggest that at 25^ΰ€ (298K) temperature, the MPCM-CK¾ resin is capable of adsorbing almost 99% of the available molybdenum from a 1% molybdenum solution mixed with 25 M sodium hypochlorite within 1 hour of exposure when a solid to liquid ratio of 2: 100 was used. After rinsing the molybdenum loaded MPCM-CSOa resin thoroughly using de-ionized w'afer, at least 90% (or tip to 95%) molybdenum found to be retained in the resin, which can be used to prepare a column for a generator. This will ultimately reduce the losses of "Mo activity during the adsorption cycle and during generator processing and handling. Considering the loss of "Mo during 24 hours of the adsorption cycle to prepare a 6-mL generator column with activity of O.oCi (at the time of elution), it is projected that a generator with specific activity of 1.50 to 20 is possible when a solid to liquid ratio is maintained at 2; 100 with a 25^<!C (298K.) solution temperature during the adsorption cycle (Figure 23), It is also estimated that a "Mo/^Tc generator with activity of 4 to 6 Ci based on neutron captured "Mo is possible by adjusting the volume and number of column(s) In the system,

EXAMPLE SO

(00172| About 4 g of chitosan was added to 300 mL deionized (Dl) water with I mL acetic acid and stirred for 2 hr at 7G^aC to form a gel, About 4 l, of HCI was added into the chitosan gel and kept under continuous stirring for another 1 hr at 70^yC,

|00173] In Shis example, an amorphous titarha gel was prepared by acid catalyzed controlled hydrolysis and condensation of titanium isopropoxtde. See Hasan, S,, Ghosh, T.K., Preias, .A., Viswanath, D.S., and Boddu, V.M,“Adsorption of uranium on a novel bioadsorbent chitosan coated perlite” Nuclear Technology, 159, 59-71 , 2007; Sehaitka, i. FL, Wong, E. H,~M., Antonietti, M, and Caruso, R.A.“Sol-gel te platingof membranes to form thick, porous tltanla, titaniabdreonia and tltania/sillea Elms” Journal of Materials Chemistry, 16, 1414-1420, 2006; Agoudjil, N., and Benkaeem, T,“Synthesis of porous titanium dioxide membranes” Desalination, 206, 531-537, 2007. Equal volumes of isopropano! (SP) and DI water were mixed in a given amount of titanium isopropoxide under continuous stirring at 7G°C. Drop-wise addition of HCI under continuous stirring and heating at 7G^aC produced a clear solution. The hydrolysis and condensation reaction was controlled by the ratio of water and titanium and W and titanium in the mixture, respectively. The final pH of the mixture was approximately 2.0 and the final reactant stoichiometry' was Tk IF: HjO: H⁺ 0,0132:039: 1 ,67:0.01 , Based on the concentration ratio of the reactants, the gel time was varied between 25 and 45 minutes,

0 |M174] At about 75% of the total gel time, a sol-gel solution of amorphous titania was mixed with ehitosan g . The mixture was kept under stirring at 70°C for another 1 hr for complete reaction of ehitosan and amorphous titanium oxide. The reaction with gluteraidehyde was performed by drop-wise addition of about 6 mL gluteraidehyde solution having a concentration of 50% to the addle ehitosan titania gd under continuous stirring at 7O⁰C, The pH of the final mixture was approximately 1.0, The mixture was kept under continuous vigorous stirring at 70^fJC for another I hr to obtain a semi-solid gel.

|0S)!?5| The resulting mass was thoroughly washed with 2% monoethanol amine to remove any unreacted gluteraidehyde. The mass was then suspended in 0, 1 M NaOH solution for 4 to 6 hr. The cross-linked mass was separated from the solution and washed with G.1 M HQ and then with deionized water (Di) until the pH of the washed solution was 1. The cross-linked mass was then dried in a vacuum oven overnight at 7G^HC. The cross-linked ehitosan gluteraidehyde composite prepared in this process is referred to as "CGST^f! herein,

|09!76| In the case of the COST sample, the peak at 1590cm^‘s Is found to be weakened, indicating that the amide groups may be involved in cross-linking reactions with titanium. The carbonyl (-CONHR) spectra at around 1650 cm ¹ is observed for ail three samples, For primary aromatic amines, C-N stretching vibrations fall between 1350 and 1 150 cm ¹.

160177] There is a peak observed at 1 170 cm (FIG. 21} for ehitosan and COST samples, respectively. Irs comparison to ehitosan, the peak at 1 170 cm ¹ is found to be weakened and a new peak appears at 1090 cm⁰ for the CGST samples.

(00178] The peak that appears at 1090 cnr^! shows prominent shifts due to OO stretching vibrations of an ether linkage. [00Ϊ79] In the region of 1000 cm * to S 20Gcm chitosan shows two peaks at i [ 57 cm ¹ and 1070 cm ¹, corresponding to the stretching of a C-O bond of C3 of chitosan (secondary OH) and C~0 stretching ofC6 of chitosan (primary OH), respectively.

fOOlSOf Compared with the C-0 spectrum of chitosan obtained at 11)70 on ¹, the absorption peaks of the secondary hydroxyl group of the COST samples become folded, as indicated in FIG. 24 , and the O-H band was reduced and shifted from 349H0 to 3450.0 cm^*1 _» suggesting that the OH groups of chitosan may be involved in the reaction with gluteraldehyde through the formation of hemiaeeta! in the presence of the acid catalyst, The evidence of the decrease of the chemical bond constant of C-0 and the significant decline in the OH stretching peaks intensities O-H ( 1000 to 1200 cm *) supports the presence of a eomplexing reaction of gluteraldehyde with the surface oxygen functional groups, such us secondary hydroxyl group In chitosan, In the ease of the CGST sample, titanium oxide appears to be Involved in a reaction with the amine group of chitosan (FIG, 24),

(06181 ! Various embodiments of chitosan based micro-porous composite material (MPCM) was prepared by cross-linking gluteraldehyde at 7(PC in the presence of catalyst. MPCM was prepared in the laboratory via the phase inversion of liquid slurry' of chitosan dissolved in acetic acid and the aide! condensation of g!utaraldehyde for better exposure of amine groups ( Hs), The MPCM was characterized by scanning electron microscopy (SEM), which revealed its porous nature. Two MPCM based derivatives such as ox ized- PC and acid-catalvzed-MPCM were also prepared. The stabilization study for MPCM 'as conducted at 50,000 krad using a ^fi0Co irradiator as a y-source. FT1R, XPS, and EDS X-ray microanalysts spectra revealed that the intensity of C, G, and N peaks of MPCM did not change substantially after irradiation, in case of Mo (VI) adsorption from aqueous solution at 298K, MPCM can hold up to 60% of its own body weight. The MPCM and its derivatives demonstrates the capacity to adsorb " o and release the daughter product ^9¾ilTe simultaneously under both batch id equilibrium conditions, it was also observed that "" e, which was the decay product a!^' "MG, was eluted with normal (0.9%) saline solution to yield more than 80% elution. Data shows that the high elution yield of ^99mTe and the leakage of Mo (VI) from the continuous column was minimum therefore the MPCM and its derivatives can be used as an adsorbent in the ^99mTe/^¾?Mo generator without using any guard column.

jQ01S2] As used herein, the terms "around," "approximately,” and "about" in connection with a numerical value denote that some variation from the numerical value may be possible, to a maximum of ± 10% of the numerical value. The terms "a," "an,” "the," and the like which denote a single occurrence also should he understood to include a plurality of occurrences, unless clearly indicated otherwise,

(90183] A "Mo/"^ffiTc generator based on low specific neutron captured produced molybdenum has been prepared using a novel MPCM resin as an adsorbent. The oxidized MPCM resin is found to be capable of adsorbing >95% of available molybdenum from the 1% solution at solution pH 3.0 when solid to liquid ratio is 2: 100. Almost 90% of available ^9¾ffTc was eluted with mainly saline solution (0.9% NaCi) from the generator. The breakthrough of "Mo and the pH of the eluent that pass through an alumina guard column are within the United States Pharmacopeia (USP) and European Union Pharmacopeia (EUP) limits,

EXAMPLE 1 1

[80184] Nanopartides of high Z element of Hafnium (Hi) were prepared by crystal growth or surfactant tempiating methods using Hafnium chloride as precursor. Hafnium nanopartides were synthesized using either PEG-400 or Pluronic-123 as surfactant, The percentage of surfactant used to synthesize the nanopartides was varied from 4 to 20% by weight. Th synthesis procedure involved three steps. In the first step, Hafnium Chloride (HfChG-SlhO) and a surfactant 'eit r PEG-400 or Piufon -S23 were mixed thoroughly in

6? a mortar and pestle, and 5 to 10ml of deionized water was added under continuous grinding, In this step, a chemical reaction is not expected; only a homogeneous mixture is formed. In the second step, an alkaline solution ~ aOH or NI- OH was added to this mixture under sonieation to nucleate and grow the nanoparticles. Nitrogen gas was used to continuously purge the system during mixing and sonieation, Ethanol was added to the mixture to transfer the surfactant into the alcohol phase. The solution w¾s further sonicated using 500 ml of deionized water for 3 h to obtain uniform intermediate stage of hafnium nanopartieies,

[Q6185] The obtained hafnium particles without further drying or any processing were cross! inked or dispersed on to MPCM resin preparation matrix. Finally, the resin was dried at 120°C for 12 hours using vacuum oven, it was expected that high Z element such as Hafnium can be integrated in to the MPCM matrix either seif-assembles or radiation induced cross-linking process. The prepared resin is termed as MPCM-Z in this study. The potential for this MPCM-Z resin as an adsorbent for the preparation of "Mo/"^mTe generator has been evaluated by exposing it to 1 % molybdenum solution using both hatch and continuous process in presence of 5 mM sodium chlorite or hypochlorite as an oxidizer. In case of neutron activated Mo-98 solution, it is important to note that oxidizing agent keeps Mo-98 at hexavalent state thus facilitating molybdenum loading onto the resin without any precipitation. Both experiments demonstrated that the MPCM-Z resin absorbs >60 wt% molybdenum at solution pH 3.0. The molybdenum loaded MPCM-Z resin was further subjected to Irradiation up to 750 kGy using e-beam, to demonstrate its radiation resistance capability in presence of high radiation field. Figures 25 and 26 shows typical 1R spectra of un irradiated molybdenum loaded MPCM-Z resin and the molybdenum loaded MPCM-Z resin irradiated at 250 kGy and 750 kGy respectively.

[00186] As Illustrated in Figures 25 and 26, the absorption peaks that appears at ed for carbonyl, amide-I, and C-O-C groups

respectively. Since MPCM-Z resin was loaded with molybdenum, it is reported that the amine absorption spectra is considered to be unchanged. Therefore, the intensity ratio of hydroxyl, carbonyl and C-O-C spectra were calculated in terms of respective amine absorption spectra. The relationship between these intensity ratios and radiation doses are shown in Figure 27 and provided in Table 13 below.

^"fable 13. Relationship between radiation dose and peak intensity

|001871 Figure 27 shows that the C-Q-C group slightly increases with the increasing of radiation dose, suggesting that there may not any chain scission of C-0 bonds occurs due to radiation. Weinwei et a! reported that there are two kinds of C-0 bond in chitosan structure: a) half condensed aldehyde and glucosidic bonds, If the half condensed aldehyde bonds broken due to irradiation, carbonyl is believed to be formed. It is evident from Figure 27 that there is no substantial changes occur in the carbonyl peak intensity at peak position 1710 cnr^! due to irradiation. On the other hand scission of glucosidic bonds leads to the formation of hydroxyl groups. Therefore, if chain scission of glucosidic bond occurs, the hydroxyl peak intensity will increase with the increase of radiation dose. For molybdenum loaded MPCM-Z resin, the hydroxyl group concentration or peak intensity ratio is appeared to be decreased due to irradiation. Without being bound by theory, it was believed that the Hafnium ions in the MPCIVi matrix interact with the imparted energy from the ionizing radiation and protect or insulates the C-0 bond therefore no chain scission in MPCM matrix occurs due to radiation.

1 O!88| in this attempt, the MPCM-Z resin was further studied to evaluate their potential for molybdenum adsorption, A generator consisting of MPCM-Z resin loaded with ^w o (ICi/gratn of resin) was prepared following a process mentioned elsewhere. The molybdenum loaded MPCM-Z was then used to prepare chromatographic column. The columns were then H shed with a saline solution at pH 4 to remove any loosely bound molybdenum. "^mTc, the decay product of "Mo, was eluted with saline solution (0,9% NaCI). It was observed that about £50% of "^mTc was extracted from the column using 6 mL of saline as an eluent. The saline solution used to elute ^9w”Tc from the MPCM-Z was modified with additives such as sodium nitrate { 1 g/L) in an attempt to improve yield. The "^mTc recovery was markedly better - about ±70%. It seemed evident that the MPCM-Z resin showed better performance In higher radiation Held produced by the " o compared to partially oxidized MPCM resin, A guard column with alumina as an adsorbent was used to keep "Mo in the eluent > 1 Ci of "Mo per mCI of "mTc. The pH of the eluent was within 4,5 to 7,5, The elution contains a yield of > ±80% of the theoretical amount of "^mTe available from the "Mo over the life of the generator,

[00189! The present invention having been described with reference to certain specific embodiments and examples, it will be understood that these are illustrative, and do not limit the scope of the appended claims.

TO

Claims

What is claimed is;

I . A sorbent comprising:

a microporous material including chitosan which has been crosshnked with glutaraidehyde in the presence of a catalyst to a g!utaraldehyde concentration of about 2 to about 4 wt% to produce a cross-linked chitosan-g!uteraldehyde composite matrix which is resistant to degradation fro t exposure to beta and gamma radiation and fro exposure to acids; and

a plurality of nanopariieies of a high Z element disposed in said cross-linked cbhosan-g!uteraldehydfc composite matrix and integrated with said cross-linked chitosan- giuteraldehyde composite matrix to reduce primary' impact of high radiation (lux and minimize radiolyiic effect on said cross-linked chhosan-gluleraidehyde composite matrix.

The sorbent as set forth in claim 1 wherein said high 2 clement is hafnium

(Hf)

3, The sorbent as set forth in claim 2 wherein Hf is present in said cross-linked ch!tosan-giuteraidebyde composite matrix between 0, 15g and 035g per grams of said cross- linked chitosan-gluteraldehyde composite matrix,

4 The sorbent as set forth in claim 1 wherein the sorbent has increased selectivity for the sorption of ^¾ o with respect to ^9<>mTe.

5, The sorbent as set forth in claim I further including an additive of sodium nitrate being present at Ig/L. Ck A method for preparing a radiation-resistant sorbent, comprising:

combining chitosan with water in the presence of an acid to form a chiiosan g ;

adding giutaraldehyde to the gel to form a semi-solid mass ire the presence of catalyst at 70^aC, in where condensation polymerization of reaction mass occurs;

washing the semi-solid mass to remove unreacted g!utara!dehyde and form a washed mass;

suspending the washed mass in aqueous base to form a neutralized crosslinked mass;

disposing a plurality of nanopartides of a high Z element on the neutralized crosslinked mass: and

drying the neutralized crosslinked mass including the plurality of nanopartides under vacuum to form the radiation-resistant sorbent,

7. The method as set forth in claim 6 wherein said step of depositing is further defined as dispersing the plurality of nanopartides made from hafnium (Hi) on the neutralized crosslinked mass.

8. The method as set forth in claim 7 wherein said step of depositing Is further defined as dispersing the plurality of nanopartides made from hafnium (Hf) between 0 5g and 0.35 per grams of the neutralized crosslinked mass on the neutralized crosslinked mass.

9. A method for preparing a plurality of nanopartides for use in a radiation- resistant sorbent, said method comprising the steps of:

J2 grinding a salt of a high Z ele ent with a surfactant under an inert atmosphere;

adding deionized water of between 5ml to 10ml during said step of grinding to form a homogenous mixture;

adding an alkaline solution to the homogenous mixture under sonieation to nucleate and grow the nanoparticles under the inert atmosphere;

transferring the surfactant of the homogenous mixture including the nanoparticles into an alcohol solution containing the nanoparticks; and

sonicating the alcohol solution to remove the surfactant and impurities.

10. The method as set forth in claim 9 wherein said step of grinding is further defined as grinding the salt of Hafnium Chloride of HfChOeSHsO and the surfactant with the surfactant being present between 4 wt,% to 20 wt.%.

1 1. The method as set forth in claim 10 wherein said step of adding the alkaline solution is further defined as adding the alkaline solution selected from NaOH or MfisOH.

12. The method as set forth in claim 9 wherein said step of transferring is further defined as adding ethanol to the homogenous mixture containing the nanopartides.

13. The method as set forth in claim 9 further including a step of depositing the sonicated alcohol solution on the radiation-resistant sorbent.

14. A method of separating isotopes from mixtures thereof, comprising:

contacting a mixture of at least two Isotopes with a radiation resistant sorbent according to claim 1 that preferentially sorbs at least one of said isotopes;

sorbing at least one of said isotopes onto or into said sorbent while one or more of the remaining isotopes are not significantly sorbed by the sorbent;

removing said one or more remaining isotopes from said sorbent.

15. The method according to claim 14, wherein said at least two isotopes comprise "Mo and ^9<½vTc,

16. The method according to claim 15, wherein said sorbent preferentially sorbs said "Mo and wherein said "^mTe is not significantly sorbed by said sorbent.

17. The method according to claim 14, wherein one of said isotopes is a cesium isotope.

18. The method according to claim 17, w'hereln said one or more remaining isotopes comprise one or more isotopes present in a radioactive w^faste stream.

19. The method according to claim 14, wherein the removing of the one or more remaining isotopes from the sorbent comprises contacting the sorbent with an eluent solution.

20. The method according to claim 19, wherein the eluent solution comprises one or more oxidizers selected from the group consisting of a chlorite, a hypochlorite, a dichromate, and a metal oxide. A generator for ^¾¾Mo/^^mTc, comprising the sorbent of claim ! .

22, A method for separating or concentrating or both one or more heavy metals from a liquid stream, comprising contacting a liquid stream containing said one or more heavy metals with a sorbent according to claim I , and sorbing one or more of said heavy metals thereon.