RU2700051C2 - Sorbent containing microporous material, and method for production thereof - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: group of inventions relates to chitosan-based microporous sorbents. Disclosed is a sorbent containing chitosan, cross-linked with glutaraldehyde in the presence of an acid catalyst. Concentration of glutaric aldehyde ranges from about 2 to about 4 wt. %. After crosslinking, the sorbent is oxidised, at least in part, with an oxidant which is chlorite in concentration of 1 mM to 10 mM. Also disclosed is a method of producing the sorbent and use thereof. Invention provides high selectivity of the sorbent to Mo(VI) relative to Tc(VII).EFFECT: sorbent is resistant to degradation under the influence of beta and gamma radiation and under action of acids.17 cl, 24 dwg, 12 tbl, 10 ex

Description

BACKGROUND

1. The technical field to which the invention relates.

This application discloses methods for modifying chitosan-based materials that increase their versatility as sorbents, in particular as sorbents of radioisotopes, as well as the ability of these materials to work in radioactive environments. The present application also discloses the materials themselves and methods of their use for the separation and purification of radioisotopes and for the separation and purification of contaminated materials, in particular, streams of radioactive and non-radioactive materials contaminated with metal ions, in particular heavy metal ions.

2. Description of the Related Art

Radioactive isotopes are widely used, in particular, in the field of nuclear medicine, both for therapy and for imaging. However, the receipt, storage and disposal of these materials can be difficult due to their radioactivity, and often also due to their long half-lives.

More specifically, in the field of radiopharmaceutical drugs (radiopharmaceuticals), ^99m Tc (having a half-life of t _1/2 = 6 hours) is one of the most widely used in medical diagnostics of radioactive zootopes, which is obtained from the decay product of the original ⁹⁹ Mo (t _1/2 = 66 h). ^99m Tc is a true source of gamma radiation (0.143 MeV), ideal for use in medicine due to its short half-life (6 hours). It is used in 80-85% of approximately 25 million radionuclide diagnostic procedures performed annually.

The initial ⁹⁹ Mo can be obtained by irradiating (under the influence of radiation, radiation) ⁹⁸ Mo with thermal / epithermal neutrons in a nuclear reactor, but most of the world's ⁹⁹ Mo supplies are obtained from the fission product of highly enriched uranium (HEU, HEU) in the reactor. The HEU process produces large amounts of radioactive waste, and its rules do not allow the recovery of unused uranium due to concerns about the proliferation of (nuclear) weapons. Instead of HEU, low enriched uranium (LEU), 20 percent or less than ²³⁵ U, could be used, but this would produce large volumes of waste due to the large amounts of unusable ²³⁸ U present. Currently, most of the world's ⁹⁹ Mo supply is from sources outside of the united states. Recent interruptions in the supply of ⁹⁹ Mo from these sources have disrupted medical procedures and demonstrated the unreliability of this supply chain. This emphasizes the need for economically viable alternative sources of ^99m Tc from ⁹⁹ Mo.

The main concerns regarding ⁹⁹ Mo obtained by the neutron capture reaction, compared to the most common fission product described above, include both lower curie yield and lower specific activity. The specific activity is much lower, which is very important, since this affects the size, efficiency and technical capabilities of the ⁹⁹ Mo / ^99m Tc generator. Therefore, the use of molybdate with reduced specific activity is economically feasible only with a more effective sorbent in order to reduce the size of the generator and to obtain a dose acceptable for radiopharmaceuticals. Some studies focus on the use of a molybdenum generator in the form of a gel. See Marageh, MG, et al, "Industrial-scale production of ^99m Tc generators for clinical use based on zirconium molybdate gel" Nuclear Technology, 269, 279-284 (2010); Monoroy-Guzman, F. et at, " ⁹⁹ Mo / ^99m Tc generators performances prepared from zirconium molybdate gels", J. Braz. Chem. Soc. 19, 3, 380-388 (2008). Other studies are aimed at creating a ⁹⁹ Mo / ^99m Tc generator using a polymer material or inorganic oxide as an adsorbent for ⁹⁹ Mo. See Masakazu, T, et al, "A ^99m Tc generator using a new organic polymer absorbent for (η, γ) ⁹⁹ Mo", Appl. Radia Isot, 48, 5, 607-711 (1997); Qazi, QM et al, "Preparation and evaluation of hydrous titanium oxide as a high affinity adsorbent for molybdenum ( ⁹⁹ Mo) and its potential for use in ^99m Tc generator," Radiochim. Acta 99, 231-235 (2011).

However, for such medical use, ^99m Tc is required to be obtained in a highly pure form. For example, when ^99m Tc is obtained by decaying ⁹⁹ Mo, it is important to achieve a high degree of separation of the two elements in order to meet regulatory requirements.

One way to achieve this level of frequency involves separating ^99m Tc from ⁹⁹ Mo using a highly efficient selective sorbent, for example, by sorption of ⁹⁹ Mo and elution with ^99m Tc. Attempts have been made to use alumina as such a sorbent. However, the Mo ⁹⁹ productivity of such alumina is about 25 mg / g sorbent. Therefore, in the prior art there remains a need for a sorbent that simultaneously adsorbs ⁹⁹ Mo efficiently and is resistant to harmful side effects of radioactive radiation. In addition, there remains a need for a sorbent with high selectivity for ⁹⁹ Mo, i.e. in such a sorbent that is capable of adsorbing ⁹⁹ Mo, while at the same time providing optimal release of ^99m Tc.

In general, there remains a need for a sorbent that is readily available, or that can be obtained from readily available materials, which can be modified so that it contains one or more functional groups (which may be the same or different), allowing this material to remove components from the technological a stream providing for such cleaning, and which is resistant to splitting under the influence of ionizing radiation.

The ion exchange process, which has been used for decades to isolate metal ions from an aqueous solution, is often compared with adsorption. The main difference between the two processes is that ion exchange is a stoichiometric process in which electrostatic forces act in a solid matrix, while adsorption separation, the capture of solute on the surface of a solid phase, includes both electrostatic interactions and forces Van der Waals. In order to find a suitable ion-exchange resin to remove cesium and strontium from the effluent (liquid waste), some researchers have tested with varying success a number of inorganic, organic and bioadsorbents. See Gu, D., Nguyen, L., Philip, CV, Huckmen, ME, and Anthony, RG "Cs ⁺ ion exchange kinetics in complex electrolyte solutions using hydrous crystalline silicotitanates", Ind. Eng. Chem. Res., 36, 5377-5383, 1997; Pawaskar, CS, Mohapatra, PK, and Manchanda, VK, "Extraction of actinides fission products from salt solutions using polyethylene glycols (PEGs)" Journal of Radioanalytical and Nuclear Chemistry, 242 (3), 627-634, 1999; Dozol, JF, Simon, N., Lamare, V., et al. "A solution for cesium removal from high salinity acidic or alkaline liquid waste: The Crown calyx [4] arenas" Sep. Sci. Technol. 34 (6 & 7), 877-909, 1999; Arena, G., Contino, A., Margi, A, et al. "Strategies based on calixcrowns for the detection and removal of cesium ions from alkali-containing solutions. Ind. Eng. Chem. Res., 39, 3605-3610, 2000.

However, the main disadvantage of the ion-exchange process when working with radioactive streams is the cost of material and regeneration for reuse. See Hassan, N., Adu-Wusu, K., and Marra, J, C. "Resorcinol-formaldehyde adsorption of cesium (Cs +) from Hanford waste solutions-Part I: Batch equilibrium study" WSRC-MS-2004. The cost of disposal (waste) is also a big problem. The industrial utility of adsorption processes is largely determined by the cost and adsorption capacity of adsorbents and ease of regeneration.

Chitosan is a partially acetylated glucosamine polymer contained in the cell walls of fungi. It is formed as a result of deacetylation of chitin, which is the main component of the shell of crustaceans and is widespread in nature. This biopolymer adsorbs metal ions very efficiently due to its ability to complexation due to the high content of amino and hydroxyl functional groups. In its natural form, chitosan is flexible and in an acidic environment tends to agglomerate and form gels. Also, natural chitosan is not porous, and specific binding sites (centers) of this biopolymer are not readily available for sorption. However, for use in the process, it is necessary to provide a physical substrate and carry out chemical modification to increase the availability of metal binding sites. It is also important that the functional group for metal binding is maintained after any such modification.

It is well known that polysaccharides can decompose by cleavage of glycosidic bonds under the influence of ionizing radiation .. IAEA-TECPOC-.1422, "Radiation processing of polysaccharides" International Atomic Energy Agency, November, 2004. Hydrogel based on polysaccharides and their derivatives was studied comprehensively, but To date, there is very limited information on the effect of radiation on chitosan-based composite materials and on their absorption capacity of metal ions.

Chitosan is a non-toxic biodegradable substance. It was studied in order to find many new applications because of its availability, polycationic nature, membrane effect, etc. The amino group present in the structure of chitosan is the site (center) of binding of the active metal, but it also promotes the dissolution of chitosan in a weak acid. In an acidic environment, chitosan tends to form a gel that is not suitable for adsorption of metal ions in a continuous process.

Some reports indicate that crosslinking of chitosan with glutaraldehyde makes chitosan resistant to acid or alkali. See Elwakeel, K.Z., Atia, A.A. and Donia, A.M. "Removal of Mo (IV) as oxoanions from aqueous solutions using chemically modified magnetic chitosan resins", Hydrometallurgy, 97, 21-28, 2009; Chassary, P., Vincent, T. and Guibal, E. "Metal anion sorption of chitosan and derivative materials: a strategy for polymer modification an optimum use" Reactive and Functional Polymers, 60, 137-149, 2004; Velmurugan, N., 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. Glutaraldehyde is a molecule containing five carbon atoms, at both ends of which aldehyde groups soluble in water and alcohol, as well as in organic solvents. It quickly reacts with the amino groups of chitosan in the process of crosslinking according to the Schiff reaction and gives thermally and chemically stable cross-links. See Migneault, I., Dartiuenave, C, Bertrand, M.J., and Waldron, K.C. "Gluteraldehyde: behavior in aqueous solution, reaction with proteins, and application to enzyme crosslinking" Bio Techniques, 37 (5), 790-802, 2004. Amino groups are also considered as binding sites of the active metal in chitosan. Therefore, according to reports, as a result of crosslinking with glutaraldehyde, chitosan becomes resistant to acid or alkali, but its adsorption capacity with respect to metal ions decreases.

Li and Bai (2005) proposed a way to protect the amino group of chitosan with formaldehyde before crosslinking with glutaraldehyde, which was then removed from chitosan, thoroughly rinsing it with a 0.5 M HCl solution. Li, Nan, and Bai, R. "A novel amine-shielded surface cross-linking of chitosan hydrogel beads for enhanced metal absorption performance" Ind. Eng. Chem. Res., 44, 6692-6700, 2005.

It is believed that crosslinking of chitosan through various functional groups depends mainly on the conditions of the crosslinking reaction, such as pH, temperature, ion concentration and surface charge of substances.

Sing et al. (2006) showed that the swelling ability, swelling ability of a chitosan hydrogel crosslinked using formaldehyde depends on the corresponding changes in 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 crosslinked with formaldehyde" Bull. Mater. Sci., 29 (3), 233-238, 2006,

The surface charge of chitosan, which determines the type of bond formed between the crosslinking agent and chitosan, depends on the pH of the solution. Hasan, S., Krishnaiah, A., Ghosh, T.K., Viswanath, DS, Boddu, VM, and Smith, ED, Adsorption of divalent cadmium from water solutions onto chitosan-coated perlite beads, Ind. Eng. Chem Res., 45, 5066-5077, 2006. The zero charge point (PZC) of pure chitosan ranges from pH 6.2-6.8. See Hasan, S., Ghosh, T.K., Viswanath, DS, Loyalka, SK and Sengupta, B. "Preparation and evaluation of Fuller's earth for removal of cesium from waste streams Separation Science and Technology, 42 (4), 717-738, 2007. Chitosan does not dissolve at alkaline pH, but at acidic pH values of the amino group present in chitosans can be protonated to form NH ₃ ⁺ or (NH ₂ -H ₃ O) ⁺ .

Li et al. (2007) described granules of crosslinked chitosan / polyvinyl alcohol (PVA) with high mechanical strength. They observed that during the crosslinking reaction, H ⁺ ions in a solution can simultaneously behave as a protection of the amino groups of chitosan. Li, M., Cheng, S., and Yan, H, "Preparation of crosslinked chitosan / poly (vinyl alcohol) blend heads with high mechanical strength", Green Chemistry, 9, 894-89B, 2007.

Farris et al. (2010) studied the mechanism of gelatin crosslinking by glutaraldehyde. Farris, 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 elevated at pH values, the crosslinking reaction is determined by the Schiff base reaction, while at low pH the –OH groups of hydroxyproline and hydroxylisine can also participate in the reaction, which leads to the formation of hemiacetals.

Hardy et al, (1969) suggested that at acidic pH, glutaraldehyde is in equilibrium with its cyclic hemiacetal and polymers of cyclic hemiacetal, and with an increase in temperature, pure aldehyde is formed in the acidic solution. Hardy, P.M., Nicholas, A.S., and Rydon, H.N. "The nature of gluteraldehyde in aqueous solution" Journal of the Chemical Society (D), 565-566, 1969.

In some studies, with some success, the main focus is on the use of a crosslinked product in medicine and for (receiving) radiopharmaceuticals. See, e.g., Hoffman, B, Seitz, D., Mencke, A., Kokott, A., and Ziegler, G. "Gluteraldehyde and oxidized dextran as crosslinker reagents for chitosan-based scaffolds for cartilage tissue engineering" J. Mater Sci: Mater Med, 20 (7), 1495-1503, 2009; Salmawi, K.M., "Gamma radiation - induced crosslinked PVA / Chitosan blends for wound dressing" Journal of Macromolecular Science, Part A: Pure and Applied Chemistry, 44, 541-545, 2007; Desai, K.G., and Park, H.J., "Study of gamma-irradiation effects on chitosan microparticles" Drug Delivery, 13, 39-50, 2006; Silva, R. M., Silva, G. A., Coutinho, O. P., Mano, J. F., and Reis, R. L. "Preparation and characterization in simulated body conditions of gluteraldehyde crosslinked chitosan membranes" Journal of Material Science: Materials in Medicine, 15 (10), 1105-1112, 2004.

и

, образующиеся в результате радиолиза в процессе облучения воды, ускоряют расщепление молекулярной цепи хитозана. Реакция между вышеприведенным свободным радикалом и молекулами хитозана приводит к быстрому распаду хитозана в водном растворе. См. IAEA- TECDGC-I422, "Radiation processing of polysaccharides" International Atomic Energy Agency, November, 2004. Эти исследования подтверждают, что применение хитозана в условиях, в которых он может подвергаться действию излучения и возможному радиолизу, является проблематичным.However, Sabharwal et al, (2004) reported that radiation treatment (irradiation) of natural polymers attracts less attention, since natural polymers undergo high-energy radiation splitting. Sabharwal, S., Varshney, L., Chaudhary, AD, and Ramnani, SP, "Radiation processing of natural polymers: Achievements &Trends" in "Radiation processing of polysaccharides", 29-37, IAEA, November, 2004. Reportedly that irradiation of chitosan causes a decrease in viscosity and splitting of the chitosan chain. See Kume, T., and Takehisa, M. "Effect of gamma-irradiation on sodium alginate and carrageenan powder" Agric. Biol. Chem., 47, 889-890, 1982; Ulanski, P., and Rosiak, JM, "Preliminary studies on radiation induced changes in chitosan" Radiat. Phys. Chem. 39 (1), 53-57, 1992. Radicals

and

resulting from radiolysis during irradiation of water accelerate the cleavage of the molecular chain of chitosan. The reaction between the above free radical and chitosan molecules leads to the rapid decomposition of chitosan in an aqueous solution. See IAEA-TECDGC-I422, "Radiation processing of polysaccharides" International Atomic Energy Agency, November, 2004. These studies confirm that the use of chitosan under conditions in which it may be exposed to radiation and possible radiolysis is problematic.

However, current requirements for biocompatible polymer materials for the treatment of radioactive waste and radio pharmaceutical waste have increased interest in developing economically viable alternative sources of polymer mesh structures that are resistant to acids, alkalis and radiation. Recent advances in the use of chitosan-based materials in medical, radioactive and radiopharmaceutical waste have attracted attention due to their availability and biocompatibility. See Alves, NM, and Mano, JF "Chitosan derivatives obtained by chemical modifications for biomedical and environmental applications" International Journal of Biological Macromolecules, 43, 401-414, 2008; Berger, J., Reist, M., Mayer, JM, Felt, O., Peppas, NA, and Gurny, R. "Structure and interactions in covalently and ionically crosslinked chitosan hydrogels tor biomedical applications", European Journal of Pharmaceutics and Biopharmaceutics , 57, 19-34, 2004. It is reported that under the influence of radiation, chemical changes occur in chitosan, and the degree of the reaction depends on the polymer network structure. See Zasnol, I., Akil, N.M. and Mastor, A. "Effect of γ-ray irradiation on the physical and mechanical properties of chitosan powder" Material Science and Engineering C, 29, 292-297, 2009; Chang, KP, Cheng, CH, Chiang, YC, Lee, SC, et al., "Irradiation of synthesized magnetic nanoparticles and its application for hyperthermia" Advanced Materials Research, 47-50, 1298-1301, 2008; Casmiro, MH, Botelho, ML, Leal, JP, and Gil, MH "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 al. "Radioactive chitosan complex for radiation therapy" US patent No. 5,762,903, dated June 9, 1998; Wenwei, Z., Xiaoguang, Z., Li, Yu, Yuefang, Z., and Jiazhen, S. "Some chemical changes in chitosan induced by γ-ray irradiation" Polymer Degradation and Stability, 41, 83-84, 1993; Lim, LY, Khor, E., and Koo, O. "γ irradiation of chitosan" Journal of Biomedical Material Research, 43 (3), 282-290, 1998; Yoksan, R., Akashi, M., Miyata, M., and Chirachanchai, S, "Optimal γ-ray dose and irradiation conditions for producing low molecular weight chitosan that retains its chemical structure" Radiation Research, 161, 471-480, 2004; Lu, YH, Wei, GS, and Peng, J. "Radiation degradation of chitosan in the presence of H ₂ O ₂ " Chinese Journal of Polymer Science, 22 (5), 439-444, 2004. However, available information regarding exposure The radiation to a composite based on crosslinked chitosan is very limited.

SUMMARY OF THE INVENTION

One embodiment of the present invention relates to a radiation resistant sorbent containing chitosan crosslinked with glutaraldehyde.

More specifically, the present disclosure discloses microporous micron particles of chitosan-based composite materials (composites) and a microporous chitosan titanium dioxide-based composite material that was prepared by crosslinking chitosan with glutaraldehyde in the presence of a catalyst.

Even more specifically, the present disclosure discloses a sorbent containing a microporous material based on chitosan crosslinked with glutaraldehyde in the presence of a catalyst, for example, such as an acid (e.g., HCl), with a concentration of glutaraldehyde from about 2 to 4 weight. %, and resistant to degradation under the influence of beta and gamma radiation and to degradation in acid or alkaline solutions.

Without linking themselves to any theory, it is believed that the microporous matrix of crosslinked chitosan increases acid resistance and the mechanical strength of the chitosan particle. As a result, the absorption capacity of the crosslinked particles with respect to metal ions from an acidic or alkaline radioactive solution increases compared to commercially available resins and commercial alumina (alumina). As a result of this increased absorption, the molybdenum efficiency can reach up to 500-700 mg / g of sorbent, more specifically up to about 600 mg / g of sorbent.

This application presents options for microporous composite (composite) materials (composites) based on chitosan, which were obtained by casting from a solution and a combination of casting from a solution and the sol-gel method.

In one embodiment, chitosan was crosslinked with glutaraldehyde in the presence of an acid as a catalyst at a temperature of about 70 ° C. with constant stirring. Not wishing to be bound by any theory, it is believed that the amino groups contained in the structure of chitosan are protonated, and therefore this protects them from reaction with glutaraldehyde. It is believed that at temperatures of about 70 ° C more aldehyde groups are available for the reaction than at room temperature. At the same time, without linking themselves to any theory, it is believed that glutaraldehyde undergoes aldol condensation and the free aldehyde group reacts with -OH groups of chitosan in the presence of an acid catalyst, thus, the polymerization of chitosan is a polycondensation (condensation polymerization). The reaction time usually ranges from about 4 hours to about 8 hours. In one embodiment, it is desirable to maintain a molar ratio of hydroxyl groups to glutaraldehyde of about 4/1.

According to a specific embodiment, further processing of the crosslinked product can be carried out, namely washing to remove excess glutaraldehyde, drying, wet or dry grinding and further chemical treatment. An example of such additional chemical treatment, which, as it turned out, was the most suitable, is at least partial oxidation with an oxidizing agent. In particular, the oxidation of one or more reagents selected from the group consisting of permanganate (e.g., potassium permanganate solution containing at least about 14 mg Mn / L solution), peroxide, chlorite, hypochlorite, dichromate (dichromate) or metal oxide, or another amphiphilic oxidizing agent is particularly suitable for increasing the selectivity of the sorbent for Mo (VI) relative to Tc (VII), and for efficient and rapid elution and regeneration of technetium from a loaded sorbent. More specifically, it is desirable to use an oxidizing agent containing one or more reagents selected from the group: alkali metal chlorite, alkali metal hypochlorite and alkali metal dichromate or transition metal oxide. More specifically, it is desirable to use an oxidizing agent containing one or more reagents selected from the group: sodium chlorite, sodium hypochlorite, potassium dichromate or cerium oxide. In addition to oxidizing the crosslinked substance of the sorbent, these oxidizing agents can preferably be included in an eluting solution (eluent solution) used to release technetium from the sorbent. It is desirable that such oxidizing agents include from about 5 to about 40 mM chlorites or hypochlorites in an eluting solution containing salt (sodium chloride).

It is desirable that the surface area of the sorbent is from about 10 to about 100 m ² / g, and more specifically, about 25 m ² / g. It is also desirable that the point of zero charge is in the range from about 7.5 to about 8.8, and more specifically, is equal to about 8.8.

The sorbent variants described herein have excellent molybdenum capacity and can sorb molybdenum in amounts of about 60% by weight, based on the dry weight of the sorbent, or higher. This capacity (retention capacity) may be about 6.25 mmol / g sorbent or higher. Sorbents also have excellent molybdenum selectivity for technetium and are able to retain molybdenum, while passing pertechnetate ion in a sodium chloride solution with an efficiency of at least about 80%. Variants of the sorbents of this invention also provide excellent capacity for heavy metals, including, for example, the ability to sorb Hg in an amount of 2.96 mmol / g dry sorbent or higher from an aqueous solution at pH 6.

In another embodiment, titanium oxide is included in a composite polymer matrix based on chitosan crosslinked with glutaraldehyde. The development of materials based on crystalline titanosilicate (CST) and titanium oxides paved the way for studies of the adsorption of metal ions from radioactive and non-radioactive waste streams on titanium oxide. See Anthony, RG, Dosch, RG, Gu _; D., and Philip, CV "Use of silicotitanates for removing cesium and strontium from defense waste" Ind. Eng. Chem, Res., 33, 2702-2705, 1994; Maria, P., Meng, X., Korfiatis, GP, and Jing, C. "Adsorption mechanism of arsenic on nanocryslalline titanium dioxide" Environ. Sci. Technol, 40, 1257-1262, 2006; Meng et al., "Methods of preparing a surface-activated titanium oxide product and of using the same in water treatment process" US Pat. No. 7,497,952 B2, March 3, 2009, Qazi and Ahmed (2011) report aqueous titanium oxide as an adsorbent for ⁹⁹ Mo and the possibility of its use in a ^99m Tc generator. Qazi, QM, and Ahmed, M. "Preparation and evaluation of hydrous titanium oxide as a high affinity adsorbent for molybdenum ( ⁹⁹ Mo) and its potential for use In ^99m Te generators" Radiochimica Acta, Doi: 10.1524 / ract. 2011. 18172011. It has been suggested that titanium oxide can form a surface complex with a metal ion as a result of bidentate binding to oxygen atoms on the surface. Hasan, S., Ghosh, T.K., Prelas, M.A., Viswanath, DS, and Boddu, VM "Adsorption of uranium on a novel bioadsorbent chitosan coated perlite" Nuclear Technology, 159, 59-71, 2007.

However, none of these documents disclosed that TiO ₂ dispersed on a chitosan matrix increases the overall absorption capacity of metal ions from a solution of radioactive waste. According to the method of the present invention, an aqueous titanium oxide gel was prepared according to the sol-gel method. A titanium oxide gel was incorporated into a chitosan matrix crosslinked with glutaraldehyde in the presence of HCl as a catalyst.

Accordingly, one embodiment of the invention relates to a method for producing a sorbent that is resistant to radiation, including:

mixing chitosan with water in the presence of acid to form a chitosan gel,

adding glutaraldehyde to the gel to form a semi-solid mass in the presence of a catalyst at 70 ° C;

washing a semi-solid mass to remove unreacted glutaraldehyde and forming a washed mass;

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

drying the neutralized crosslinked mass with the formation of a sorbent resistant to radiation.

Another embodiment of the invention relates to such a method, further comprising:

the formation of an amorphous titanium dioxide gel by acid-catalyzed hydrolysis and condensation of titanium isopropoxide;

mixing an amorphous titanium dioxide gel with chitosan under conditions sufficient for the gels to react before the indicated addition of glutaraldehyde.

In one embodiment, the microporous chitosan-based composite material is then suspended in a solution of pH 3 and irradiated at 50,000 crad using ⁶⁰ Co radiation. The specific objectives of this work were: 1) obtaining microporous composite materials based on chitosan for the adsorption of metal ions from highly acidic or highly alkaline solutions of radioactive waste; and 2) optimization of the crosslinking process to obtain the maximum number of metal binding sites (centers).

Accordingly, another embodiment of the invention relates to a method for isolating isotopes from mixtures of isotopes, including:

contacting the mixture of at least two isotopes with a radiation resistant sorbent according to claim 1, which preferably sorb at least one of said isotopes;

sorption of at least one of said isotopes on or in said sorbent, while one or more of the remaining isotopes are sorbed by this sorbent to a small extent; removing said one or more remaining isotopes from said sorbent.

Crosslinked chitosan composite material is an excellent inexpensive alternative adsorption material compared to existing resins, and therefore is a suitable adsorbent material for the extraction of metal ions from radioactive and non-radioactive aqueous solutions. It was found that the success of adsorption processes in ⁹⁹ Mo / ^99m Tc generator systems is largely dependent on the cost and capacity of the adsorbents and the ease of isolation of ^99m Tc from the generator. The main objective in this particular method from the point of view of radiation safety is to “slip” or partially elute the original ⁹⁹ Mo along with ^99m Tc from the generator, which should (which should) remain within the standards of the Nuclear Regulatory Commission (MRC). Embodiments of the materials and methods of this invention provide for the proper selective separation of ^99m Tc from the generator, thereby solving this problem and satisfying the need for such a generator.

Also, crosslinked chitosan composite materials can be used in a separation or concentration method, or both, of heavy metals from a liquid stream, for example, from a waste stream or a process stream, by contacting a liquid stream containing one or more heavy metals with a composite material based on crosslinked chitosan, and by sorption on this material of one or more of these heavy metals.

BRIEF DESCRIPTION OF THE FIGURES

Various aspects of the embodiments of the invention as described herein may be better understood from a consideration of the figures, which should not be construed as limiting the claimed invention.

In FIG. 1 is a microphotogram obtained by a scanning electron microscope, which shows chitosan and specific examples of modified chitosan (MRM) disclosed in this description. FIG 1a shows unmodified chitosan; in FIG. 1b shows a variant of the MPCM material.

In FIG. 2 is a graph showing the results of a thermogravimetric analysis (TGA, TGA) of chitosan and a variant of MPM.

In FIG. 3 is a graph showing an X-ray diffraction pattern of chitosan and a variant of the MPCM material.

In FIG. 4 shows the infrared spectrum with the Fourier transform (FTIR, Fourier-IKS) of chitosan and a variant of the MRM material according to this description,

In FIG. Figure 5 presents a survey image obtained by x-ray photoelectron spectroscopy (XPS, XPS) for chitosan and a variant of MRSM.

In FIG. Figure 6 shows the spectra obtained by X-ray photoelectron spectroscopy (XPS, XPS) (XPS) for chitosan and a variant of the MRM. In FIG. 6a, 6b, and 6c show C 1s, O 1s, and N 1s positions, respectively.

In FIG. 7 presents the data of microanalysis obtained by energy dispersive x-ray spectroscopy (EDS) for the variant of MRSM according to this description. In FIG. 7a shows the spectra of chitosan and the MPCM variant before and after irradiation. In FIG. 7b compares the spectra of chitosan and a variant of MPM. In FIG. 7c, a comparison is made of the spectra of the MPCM variant before and after irradiation.

In FIG. 8 shows reaction schemes for producing MPCM variants of the invention.

In FIG. 9 shows FTIR spectra of a variant of the modified chitosan of the present invention before and after irradiation.

In FIG. 10 shows X-ray photoelectron spectra (XPS) for the MPCM variant before and after irradiation. In FIG. 10a, 1b, and 10c show C 1s, O 1s, and N 1s positions, respectively.

In FIG. 11 is a graph showing the surface charge of an MPCM variant with and without exposure with 1% Mo (VI) in solution in the presence of 1 M NaNO ₃ .

In FIG. 12 is a graph showing the effect of pH on the sorption of molybdate in the MPCM variant; initial conditions: concentration of 5.21 mmol / l and temperature of 298 ° K.

In FIG. 13 schematically presents the mechanisms of Mo (VI) sorption reactions on a variant of MPCM from an aqueous solution.

In FIG. Figure 14 shows the isotherms of uniform sorption during the extraction of Mo (VI) by the MPCM variant, showing that the experimental data (*) correlate with the adsorption model of the Langmuir isotherms (solid line) under conditions when the concentration of Mo (VI) in the solution varies from 1 mmol / l to 94 mmol / l, temperature 298 ° K, pH ~ 3.

In FIG. 15a is a graph showing a slip curve for adsorption of Mo (VI) on an MPCM carrier, the influx concentration at the inlet was 5.21 mmol of Mo (VI) / L at pH 3; In FIG. 15b is a graph showing the effect of the influx pH on the slip curve for Mo (VI) from a column filled with a variant of the MPCM. The inlet concentration at the inlet was 5.21 mmol Mo (VI) / l with 153.8 mmol NaCl / l at a pH of 4 to 1, respectively. In both Figures, the height of the carrier in the column was 3.2 cm, the flow rate was 1 ml / min.

In FIG. 16 is a graph showing breakthrough curves for pertechnenate from a column filled with a variant of MPCM without oxidation with a load of 6.25 mM Mo (VI) / gram MPCM. The column volume was 2.5 cm ³ . The inflow rate was 1 ml / min. The concentration of the inflowing stream was 0.25 mM pertechnenate / L in saline (0.9% NaCl) solution.

In FIG. 17 is a graph showing the surface charge of oxidized and non-oxidized MPCM exposed to 1% Mo (VI) in an aqueous solution in the presence of 1N NaNO ₃ .

In FIG. 18 is a graph showing an elution profile for ^99m Tc from an MPCM variant loaded with Mo (VI) with the addition of an exact concentration of ⁹⁹ Mo.

In FIG. 19 is a graph showing the relationship between the number of elution (s) and the percentage release (recovery) of ^99m Tc and Mo (VI) from the MPCM variant as the sorbent.

In FIG. 20 is a block diagram of a process applying the generator systems ^99m Tc / ⁹⁹ Mo and ⁹⁹ receiving Mo by neutron capture an embodiment MRFM as a sorbent.

In FIG. Figure 21 is a graph showing the effect of temperature on the absorption of molybdenum by composite MPCM-ClO ₂ under the following conditions: initial concentration of a solution of 1% Mo with 25 mM NaOCl, pH 3.0, and the ratio of solids to liquid 1: 100, contact time 0.5 hours.

In FIG. 22 shows a curve of the heat of adsorption at different loads and temperatures (from 24 ° C to 50 ° C) of the composite of FIG. 21.

In FIG. 23 is a diagram of the expected specific activity of the proposed MPCM-based generator with a column volume of 6 ml.

In FIG. 24 shows an FTIR spectrum of chitosan and another embodiment of the modified chitosan of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The methods according to this description and the resulting materials based on modified chitosan, as well as methods for their use, can be better understood using the following examples, which are intended to illustrate but not to limit the attached claims.

Medium molecular chitosan (from about 190,000 to about 310,000 as determined by the viscometric method), 75-85% deacetylated, was obtained from Sigma-Aldrich Chemical Corporation, WI, USA. All chemical reagents used in the examples were reagents of analytical purity.

The modified chitosan according to this invention can be obtained by the reactions schematically represented in FIG. 7 by crosslinking with glutaraldehyde in an acidic medium at the temperature indicated below. Although the amount of glutaraldehyde used may vary slightly, it has been found that it is effective to use from about 2 ml to about 10 ml, more specifically, from about 2 ml to about 8 ml, more specifically, about 6 ml of glutaraldehyde per 4 g of chitosan. The pH in the crosslinking reaction between glutaraldehyde and chitosan can also vary to some extent, but it has been found that a pH of from about 0.7 to about 3, more specifically, from about 0.7 to 2, and more specifically, about 1.0, is effective. The crosslinking temperature may also vary, but is preferably from about 50 ° C to about 80 ° C, more specifically, about 70 ° C.

EXAMPLE 1

The sorption capacity of the chitosan used in this study for ions, measured by the standard titration method, ranged from 9 to 19 milliequivalents / g. About 4 g of chitosan was added to 300 ml of DI water with 1 ml of acetic acid and stirred for 2 hours at 70 ° C until gel formation. Approximately 5 ml of HCl / HNO _{3 was} added to the chitosan gel and left under constant stirring at 70 ° C for another 1 h to facilitate protonation of the amino groups, which is expedient for the reasons indicated below.

The reaction with glutaraldehyde was carried out by adding dropwise about 6 ml of a solution of glutaraldehyde with a concentration of 50% to the chitosan acid gel with constant stirring (the mixing speed was established by trial and error, but usually it is from 200 rpm to 500 rpm) at 70 ° C. The final pH of the mixture was approximately 1.0. The amount of glutaraldehyde used in this study was determined by trial and error. The mixture was kept under constant vigorous stirring (500 rpm) at 70 ° C for another 1 hour, a semi-solid gel was obtained. The amino groups contained in chitosan are significantly more reactive with respect to the aldehyde in the Schiff reaction than the hydroxyl groups of chitosan. It was assumed that at 70 ° C there will be more free aldehyde groups in the solution than at room temperature. In an acidic solution, protonation of the amino group inhibits the formation of a complex between the aldehyde and the amino group. In addition, glutaraldehyde can undergo aldol condensation, and the reaction of the hydroxyl groups of chitosan with free aldehyde can be catalyzed by acid at 70 ° C.

Then the resulting mass was thoroughly washed with 2% monoethanolamine to remove the smallest impurities of unreacted glutaraldehyde. Then the mass was suspended in 0.1 M NaOH solution for 4-6 hours. The crosslinked chitosan mass was separated from the solution and washed with 0.1 M HCl and then with deionized water (DI) until the pH of the wash solution reaches 7. Then, the crosslinked mass was dried in a vacuum oven overnight at 70 ° C. A composite material based on chitosan crosslinked with glutaraldehyde is referred to herein as “MPM” or “microporous composite material”.

MPCM was crushed in a laboratory vibratory mill to obtain particles ranging in size from about 50 to 200 microns. Some of these MPCM particles were suspended overnight in an aqueous solution of pH 3. The pH of the solution was maintained with 0.1 M HNO ₃ . Suspended MPCM particles were irradiated using ⁶⁰ Co as a radiation source. MPCM particle characteristics were obtained using SEM, EDS X-ray microanalysis, FOR and XPS spectroscopic analysis.

A raster micrograph (SEM, raster electron micrograph, SEM) of chitosan and MRM material was used to study surface morphology, as shown in FIG. 1. A SEM microphotogram of the secondary electrons of the samples was obtained using reflected electrons with an accelerating voltage of 10 keV. A SEM microphotogram of crosslinked chitosan and an MPCM sample is shown in FIG. 1a and 1b, respectively. In FIG. 1a shows that chitosan is not porous, but as shown in FIG. 1b, MPCM is obviously microporous in nature.

TGA (thermogravimetric) analysis of freshly prepared MPCM in the laboratory and pure chitosan, respectively, was carried out on a TGA analyzer (TA Instruments) in a nitrogen stream (200 ml / min). For each experiment, approximately 20 mg of MPCM was heated to a temperature of 30 to 600 ° C in an open refractory crucible at a given heating rate. TGA measures the amount and rate of change in mass of a sample as it heats up at a given rate. Thermogravimetric analysis of both MPCM and chitosan provided additional information about changes in composition as it warms up under controlled conditions. The heating rate in this analysis was set to 5 ° C / min. TGA profiles shown in FIG. 2 indicate a two-stage decomposition process for pure chitosan, while MPCM slowly decomposes with increasing temperature.

Thermogravimetric analysis (TGA) of chitosan at a heating rate of 5 ° C / min in a nitrogen atmosphere (200 ml / min) shows that complete dehydration occurs at 250 ° C with a mass loss of 8%. Anhydrous chitosan decomposes further in the second stage with a mass loss of 32% at 360 ° C. It completely burned at 600 ° C with a further mass loss of 12%. The remaining 48% is chitosan residue burnt at 600 ° C.

In the case of MRSM, complete dehydration occurs at 230 ° C with a weight loss of 12%. Anhydrous MPCM completely burned out at 600 ° C with a mass loss of 36%. The remaining 52% is the MPCM residue burnt at 600 ° C. It can be noted that the MPCM combustion product is 4% less compared to chitosan, which indicates that the MPCM contains 4% of a crosslinking agent, such as glutaraldehyde, which is completely burnt in this heating range.

The swelling process and acid resistance of the MPCM material were also analyzed. The MPMM swelling process was carried out by immersing it in deionized water and sodium chloride solution (saline) according to the method described by Yazdani-Pedram et al., "Synthesis and unusual swelling behavior of combined cationic / non-ionic hydrogels based on chitosan," Macromol. Biosci., 3, 577-581 (2003).

Also studied the process of swelling of chitosan in deionized water and saline.

The degree of swelling of chitosan and MRSM was calculated using the equation below:

where V _s is the volume of the swollen MPCM and V _d is the volume of the dry sample. It was observed that in deionized water, chitosan swelled by about 105% of its initial volume during equilibrium for 24 hours, in the case of MRM, a very fast swelling process was observed, an increase of about 200% was achieved within five minutes, and equilibrium was established after 24 hours. The study of swelling in deionized water was carried out in the pH range from 3 to 6. In equilibrium, the maximum volume of MPCM was almost 219% more than the volume in the dry state.

A similar MPCM swelling process was also observed for saline (0.9% NaCl) solution. In the equilibrium state, the volume of MPCM increases to 223% of its initial volume in the dry state in saline. The results of the study of swelling show that the hydrophilicity of MPCM is higher than the hydrophilicity of chitosan. It was reported that the process of swelling of the chitosan hydrogel depends on the ionized groups present in the gel structure. See Ray et al., Development and Characterization of Chitosan Based Polymeric Hydrogel Membranes, Designed Monomers & Polymers, Vol.13, 3, 193-206 (2010). Due to the protonation of -NH ₂ groups in MPCM in solution in the pH range from 3 to 6, the fast swelling of MPCM in deionized water can be attributed to the strong repulsion of the -NH ₃ ⁺ groups. In a salt solution at a pH above 6, the carboxyl groups of carboxylic acids are ionized and the electrostatic repulsive forces between charges (COO-) cause an increase in swelling. See Yazdani-Pedram et al., See above; Radhakumari et al., "Biopolymer composite of Chitosan and Methyl Methacrylate for Medical Applications," Trends Biomater. Artif. Organs, 18, 2, (2005); Felinto et al., "The swelling behavior of chitosan hydrogel membranes obtained by UV- and γ-radiation," Nuclear Instruments and Methods in Physics Research B, 265, 418-424 (2007).

The MPCM sample was immersed in an acidic medium at various concentrations of HCl, HNO ₃ and H ₂ SO ₄ acids for 24 hours. Chitosan tends to gel in acidic media, which makes it unsuitable for use in an adsorption column for the extraction of metal ions from aqueous solutions. One of the main goals of this study was to obtain an acid-resistant material based on chitosan simultaneously with exposing a larger number of -NH ₂ groups, which are active metal binding sites (centers) for chitosan. Table 1 shows the results showing the degree of tolerance of MPCM to acid. It was observed that the MPCM material exhibits a higher degree of tolerance to HCl than to HNO ₃ and to H ₂ SO ₄ . There is no significant change in the physical size and shape of the MPCM up to the concentrations of the 12M HCl solution, 12M H ₂ SO ₄ and 3.9 M HNO ₃ , but the MPCM appears to be completely soluble in the 7.8 M HNO ₃ solution. It is clear that MRM is more acid resistant than chitosan.

= не растворим

= not soluble

= тенденция образовывать гель или полностью растворяться

= tendency to gel or completely dissolve

The Figure 3 presents the XRD pattern for granules of pure chitosan and MPCM. For a chitosan (X-ray) sample, a diffraction peak is observed near 20 °, which indicates a relatively regular crystal lattice (110, 040) of chitosan. See Wan et al., "Biodegradable Polylactide / Chitosan Blend Membranes," Biomacromolecules 7 (4): 1362-1372 (2006). The peak observed for MRSM is broadened, from which it can be concluded that the MRSM sample is amorphous in nature. This also indicates that chitosan and glutaraldehyde complexed in the presence of acid; therefore, the crystal structure of chitosan is disturbed by the formation of a chemical bond between chitosan and glutaraldehyde.

The Fourier transform infrared (FTIR) spectra of an MPCM sample previously obtained were studied on a BRUKER FTIR spectrometer equipped with a N- ₂ cooled broadband detector based on cadmium-mercury telluride (MCT, MCT) and a KCl beam splitter. FTIR absorption spectra were recorded with a resolution of 8 cm ^–1 , 128 images were taken in the range from 400 to 4000 cm ^–1 . The intermolecular interactions between chitosan and glutaraldehyde in the presence of HCl acid are reflected in a change in the characteristics of the IR spectrum. In FIG. 4 gives a comparison of the IR spectra of chitosan and MPCM. In the spectral region from 2900 cm ⁻¹ to 3500 cm ⁻¹ , peaks at 3498 cm ⁻¹ and at 2950 cm ⁻¹ , respectively, are observed for chitosan and MRSM, which corresponds to stretching vibrations of OH and NH groups and stretching vibrations of CH in CH and -CH ₂ . Peaks in the region from 1350 to 1450 cm ^-1 show a saturated hydrocarbon bond CH.

The complex nature of the absorption spectra in the region of 1650–1500 cm ^–1 suggests that the bands of the aromatic ring and double bonds (C = C) overlap with the bands of stretching vibrations C = O and the bands of bending vibrations of OH. Peaks expected in this IR region include the band of protonated amine (-NH ₃ ⁺ ), amine (-NH ₂ ) and carbonyl group (-CONHR). In FIG. 4 shows a peak at 1600 cm ⁻¹ with a shoulder-like peak with a center of about 1570 cm ⁻¹ and 1670 cm ⁻¹ , representing —NH ₂ and chitosan amide group 1, respectively. However, the presence of a relatively sharper peak at 1590 cm ⁻¹ in the MPCM spectrum than in the chitosan spectrum suggests the presence of an NH3 ⁺ band in the MPCM sample.

XPS analysis of chitosan and the MPCM sample obtained above was performed to better understand the intermolecular interaction between chitosan and glutaraldehyde. XPS analysis performed an overview scan to ensure that the energy range is applicable to detect all elements. XPS data was obtained using a KRATOS XPS spectrometer model AXIS 165 with a Mg-based monochromatic x-ray source (hν = 1253.6 eV) as an excitation source at a power of 240 watts. The spectrometer was equipped with an eight-channel hemispherical detector, and during the analysis of the samples, the pass energy was 5-160 eV. Each sample was exposed to x-ray radiation at the same time and with the same intensity. The XPS system was calibrated against the peaks of UO ₂ (4f7 / 2), where the binding energy was 379.2 eV. For analysis of samples, a sensor angle of 0 ° was used.

In FIG. Figure 5 shows the positions of the C 1s, O 1s, and N 1s peaks obtained by an overview scan of chitosan and the MPCM sample obtained above, respectively. In FIG. Figure 6 shows in detail the positions of the peaks for C 1s, O 1s, and N 1s in chitosan and in MRM. After deconvolution (signal separation), instead of one C-1s peak, two peaks were observed, one for C-N at 284.3 eV and the other for C-C at 283.5 eV (FIG. 6a). In the MPCM sample, the C-Cs peak appears to be collapsed and slightly shifted, while the C-N peak has an increased intensity compared to chitosan (FIG. 6a). Peaks for oxygen-containing groups (O 1s) are found at 530.5 eV and 531.1 eV for chitosan and MRSM, respectively (Figure 6b).

Compared to the C 1s and O 1s peaks for MRM, the C – C peak of chitosan at 283.5 eV is curtailed, and the O1s peak is shifted from 530.5 eV to 531.1 eV due to the crosslinking reaction with glutaraldehyde. This suggests that the O1s component can be connected by an ordinary chemical bond corresponding to the OH or C — O group in the structure for various surface functional groups containing oxygen. See Wen et al., "Copper-based nanowire materials: Templated Syntheses, Characterizations, and Applications," Langmuir, 21, 10, 4729-4737 (2005). Chemical shifts are considered significant if they exceed 0.5 eV. See Hasan et al., "Adsorption of divalent cadmium from aqueous solutions onto chitosan-coated perlite beads," Ind. Eng. Chem. Res., 45, 5066-5077 (2006). Thus, the shift of the O 1s peak in the MPCM sample also indicates that glutaraldehyde reacted with the oxygen-containing functional groups of chitosan. XPS data indicate that the chemical binding of glutaraldehyde occurs according to the —CH ₂ OH or OH groups on the chitosan structure, which is also consistent with the results obtained by FTIR analysis (FIG. 4).

N 1s peak for chitosan was at 397.5 eV (FWHM 1.87) for Nitrogen -NH ₂ group in chitosan (FIGURE 6c.); For MRM, peak N 1s was at 397.7 eV. One of the goals of studying the N 1s peak was to determine whether the amino groups that are the binding sites of active metals with chitosan actually participated in crosslinking reactions with glutaraldehyde. In FIG. Figure 6c shows a clear N 1s peak for MPCM at 397.7 eV, which can be attributed to the -NH ₂ groups, which suggests that the amino groups of chitosan did not participate in the crosslinking reaction with glutaraldehyde. This also appears from the FTIR spectrum (FIG. 4).

Table 2 shows the results obtained by XPS by elemental analysis of the surface of an MPCM sample, by determining the peak area adjusted for an experimentally determined sensitivity factor (± 5%). It was found that the preparation of a porous material based on chitosan, in this case the MPCM variant described above, leads to the exposure of more NH ₂ groups on the surface of the material. The nitrogen concentration, as determined based on the N 1s peak of the MPCM sample, was almost twice as high as that calculated for chitosan (Table 2). It is believed that the nitrogen contained in the MPCM has completely transferred from chitosan. The high nitrogen content in the MPCM shown in Table 2 is due to the microporous nature of the MPCM, which gives access to more amino groups on the surface than in the case of non-porous chitosan. This is also consistent with the results reported by Hasan et al., See above, obtained by dispersing chitosan on perlite. It is believed that the change in the intensity of the C 1s peak and the binding energy of the O 1s peaks at 531.0 eV of the MPCM sample as compared to chitosan is due to the reaction with glutaraldehyde in the presence of acid as a catalyst.

• MRSM-1 sample after irradiation at 50,000 krad using a Co source of gamma radiation.

Microanalysis by energy dispersive x-ray spectroscopy (EDS) was performed on the same MRM sample as used for SEM microphotography (scanning electron micrograph, SEM). EDS microanalysis was used for elemental analysis of MRSM (FIG. 7). Peaks for carbon atoms, oxygen and nitrogen, the main components of chitosan, are shown at 0.3 keV, 0.36 and 0.5 keV, respectively (FIG. 7a, 7b). Due to the reaction with glutaraldehyde, the intensity of the carbon peak for MRSM increases; while the intensity of the peak oxygen decreases compared with chitosan (FIG. 7b). In FIG. 7b also shows that the peak of nitrogen in the MPCM sample is shifted due to protonation of amino groups (—NH ₂ ) compared to the peak of nitrogen in chitosan. Based on the analysis by FTIR, EDS and XPS methods and without any theory, possible mechanisms for the reaction of glutaraldehyde with -OH groups of chitosan through the formation of acetal bonds are presented in FIG. 8.

The radiation resistance (radiation resistance) of the MPCM sample described above was evaluated by irradiating it using a ⁶⁰ Co source. The IR spectra of the sample MPCM composite before and after irradiation using a ⁶⁰ Co source are shown in FIG. 9. In FIG. Figure 9 shows that an MPCM sample suspended in water at pH 3.0 can withstand gamma radiation of up to about 50,000 crad without a noticeable (percentage) loss of its identification characteristics.

In FIG. 7c shows the energy dispersive X-ray spectra (EDS) of chitosan particles and MPMs before and after irradiation with a dose of 50,000 crad from a source of ⁶⁰ Co. FIG. 7c shows that the intensity of the peaks of carbon, oxygen and nitrogen did not change after irradiation of the sample. In FIG. Figure 10 shows the positions of the peaks of carbon, oxygen, and nitrogen obtained by analysis of the MPCM sample by XPS (X-ray photoelectron spectroscopy) before and after irradiation. It is seen that the total binding energy for the C 1s peak changed after irradiation, as shown in Table 2. The C 1s peak for the MPCM sample was 283.5 eV, while for the MPCM sample, two peaks were observed at 283.5 and 284.5 eV (FIG. 10a ) Peak N 1s of about 397.5 eV, which is present in the MPCM sample after irradiation, can be attributed to NH ₂ groups in the MPCM structure. For the O 1s peak of the irradiated MPCM sample, no change is observed. The magnitude of the shift in the binding energy depends on the concentration of various atoms, especially on the surface of the material. Compared to XPS (FIG. 10a-c), there was no shift in the N 1s and O 1s peaks of the MPCM sample before and after irradiation (Table 2), this shows that the chemical characteristics of N atoms were not very affected. This is also observed in the spectra of EDS and FTIR, as can be seen in FIG. 7 and 9.

Analysis of the sorption of molybdenum by the above-described MPCM sample was carried out in the form of a periodic process. About 1.0 grams of MPCM adsorbent was suspended in 100 ml of a solution containing ammonium molybdate in a concentration range from 1 mmol / L to 94 mmol / L. The initial pH of the solutions was adjusted from 2.0 to 8.0 using either a 0.01 M NaOH solution or a 0.1 M HCl solution. Then the solutions were placed on a rocking chair (shuttle apparatus) (160 rpm) for 24 hours at 298 ° K. After 24 hours, the final pH of each solution was fixed and the solutions were centrifuged for 5 minutes at 3000 rpm to separate the supernatant from the solution. Then the supernatant was filtered through a 0.45 μm membrane filter and the filtrate was checked for molybdenum removal using an Agilent 7700X Inductively Coupled Plasma Mass Spectrometer (ICP, ICP-MS), which is adapted to detect molybdenum. The adsorption isotherm was built by varying the initial concentration of molybdenum from the solution. The amount of adsorbed molybdenum per unit mass of adsorbent (q _e ) was calculated by the equation:

where C _i and C _e denote the initial and equilibrium concentrations in mg / l, respectively, V denotes the volume of solution in liters (l), and M denotes the mass of adsorbent in grams (g).

The surface charge of the granule of the MPCM sample was determined by the standard method of potentiometric titration in the presence of a symmetric electrolyte, sodium nitrate, as described by Hasan et al., See above. The magnitude and sign of the surface charge was measured relative to the point of zero charge (PZC). The pH value at which the resulting surface charge of a solid is zero at all electrolyte concentrations is called the point of zero charge. The pH of the PZC zero charge point for a given surface depends on the relative acidic and basic properties of the solid and makes it possible to evaluate the resulting absorption of H ⁺ and OH ^- ions from solution. The results are presented in FIG. eleven.

It was found that the PZC value of the MPCM sample obtained as described above is 8.8, and it is similar to the value reported by Hasan et al., See above for perlite granules coated with chitosan. It is reported, however, that the PZC value for pure chitosan varies in the range of pH values from 6.2 to 6.8. See Hasan et al., See above. In FIG. 11 shows that a positively charged surface prevailed in a relatively low pH range. The surface charge of the MPCM was almost zero in the pH range from 7.5 to 8.8. Protonation of the MPCM sharply increased the pH range from 7.5 to 2.5, making the surface positively charged. At pH below 2.5, the difference between the initial pH value and pH after equilibrium was established is insignificant, which indicates the complete protonation of the amino groups (-NH ₂ ) present in the MPCM. At a higher pH value, from 7.5 to 8.8, the surface charge of the MPCM slowly decreases, which indicates a slow protonation of the MPCM. In the case of chitosan, the degree of protonation was reported to reach 97% at pH 4.3. However, it decreases as the pH rises. It is reported that the degree of protonation of the chitosan surface is 91%, 50% and 9% at pH 5.3, 6.3 and 7.3, respectively. See Hasan et al., "Dispersion of chitosan on perlite for enhancement of copper (II) adsorption capacity" Journal of Hazardous Materials, 52 2, 826-837, 2008.

Without binding themselves to any theory, it is believed that the PZC value of 8.8 and the nature of the change in the surface charge of the MPCM are due to the modification of chitosan due to its crosslinking with glutaraldehyde in the presence of acid as a catalyst, which makes it amphoteric in nature in the pH range from 7.5 to 8.8.

The effect of pH on the adsorption of molybdenum using MRM was studied by changing the pH of the solution in the range from 2 to 8 (FIG. 12). The pH of the molybdenum solutions was first adjusted between 2 and 8 using either 0.1NH ₂ SO ₄ or 0.1 M NaOH, and then MRM was added. As adsorption progressed, the pH of the solution slowly increased. During the experiment, no attempts were made to maintain a constant solution pH. Quantitative adsorption of molybdenum at equilibrium concentration in solution is shown for each initial pH of the solution in FIG. 12. The adsorption of molybdenum by MPCM increased with increasing pH from 2 to 4. Although the maximum adsorption was observed at pH 3, with an increase in the pH of the solution above 6, the adsorption of molybdenum on MPCM began to decrease. Accordingly, experiments were not performed at a pH above the PZC of the MPCM sample.

et al., "Molybdenum (VI) Binded to Humic and Nitrohumic Acid Models in Aqueous Solutions. Salicylic, 3-Nitrosaliculic, 5-Nitrosalicylic and 3,5 Dinitrosalicylic Acids, Part 2" J. Braz. Chem. Soc, 17, 3, 482-490, 2006. Сообщается, что даже если полианион присутствует в растворе, адсорбция по-прежнему происходит через образование MoO₄ ^2-. См. Jezlorowski et al., "Raman and Ultraviolet Spectroscopic Characterization of Molybdena on Alumina" The Journal of Physical Chemistry, 83, 9, 1166-1173, 1979; El Shafei et al., "Association of Molybdenum Ionic Species with Alumina Surface," Journal of Colloid and Interface Science, 228, 105-113, 2000. Деградация полианионов в растворе происходит вследствие повышенного локального рН близ поверхности адсорбента.In order for a metal ion to adsorb from a solution on an adsorbent, the metal must form an ion in the solution. The types of ions formed in the solution and the degree of ionization depend on the pH of the solution. As for MRM, the amino acid group (—NH ₂ ) is the main functional group responsible for the adsorption of the metal ion. Depending on the pH of the solution, these amino groups can be protonated to form NH ₃ ⁺ or (NH ₂ -H ₃ O) ⁺ , and the protonation rate depends on the pH of the solution. In view of the foregoing, the surface charge on the MPCM will determine the type of bond formed between the metal ion and the surface of the adsorbent. Depending on the pH of the solution, molybdenum in the aqueous solution can hydrolyze to form various particles. At relatively high and low pH values, mainly MoO ₄ ^2- and various isopolyanions predominate (mainly MO ₈ O ₂₄ ^6- ). In an acidic environment, the MoO ₄ ^2– anion forms many different polyanions. See Guibal et al., "Molybdenum Sorption by Cross-linked Chitosan Beads: Dynamic Studies". Water Environment Research, 71, 1, 10-17, 1999;

et al., "Molybdenum (VI) Binded to Humic and Nitrohumic Acid Models in Aqueous Solutions. Salicylic, 3-Nitrosaliculic, 5-Nitrosalicylic and 3,5 Dinitrosalicylic Acids, Part 2" J. Braz. Chem. Soc, 17, 3, 482-490, 2006. It is reported that even if the polyanion is present in the solution, adsorption still occurs through the formation of MoO ₄ ^2- . See Jezlorowski et al., "Raman and Ultraviolet Spectroscopic Characterization of Molybdena on Alumina" The Journal of Physical Chemistry, 83, 9, 1166-1173, 1979; El Shafei et al., "Association of Molybdenum Ionic Species with Alumina Surface," Journal of Colloid and Interface Science, 228, 105-113, 2000. The degradation of polyanions in solution occurs due to the increased local pH near the surface of the adsorbent.

As noted above, the maximum adsorption capacity of MPCM for molybdenum ions from solutions is observed at a pH of about 3. Without being bound by any theory, it is believed that the amino group in the MPCM contains an unshared electron pair at the nitrogen atom, which mainly behaves as an active center (site ) to form a complex with a metal ion. As mentioned earlier, at lower pH values, the amino group in the MPCM is protonated to form NH ₃ ⁺ , which results in increased electrostatic attraction between N ₃ ⁺ and the anion of the sorbed substance. Since the MPCM surface has a positive charge in the pH range from 2.5 to 7.5, molybdenum in anionic form (Mo (VI)) is apparently the main particle adsorbed due to the forces of electrostatic (Coulomb) interaction. As mentioned earlier, it was found that the pH of the solution increases after adsorption, which can be attributed to H ⁺ ions released from the surface of the MPCM as a result of sorption of molybdenum-containing anions from the solution. As for MRM, the protonation of NH ₂ groups occurs in the range of fairly low pH values. The fact that the pH of the solution rises during adsorption suggests that Mo (VI) forms a covalent bond with the NH ₂ group.

Since the pH of the equilibrium solution increased from a lowered pH to a pH in PZC (pH _pzc ), the reduced Mo (VI) recovery as a percentage was attributed to a decrease in the electrostatic attraction between the surface of the MPCM and Mo (VI) particles in anionic form. It can be noted that it was found that the PZC of the MPCM sample shifts to 4.5 in the presence of molybdenum ions compared to the PZC of the MPCM sample without these ions (FIG. 11). The shift of the PZC of the MPCM material toward lower pH indicates a high specific adsorption and the formation of the inner sphere of the complex due to the adsorption of molybdenum. Similar results were obtained when studying the adsorption of molybdenum on gibbsite. See Goldberg, S. "Competitive Adsorption of Molybdenum in the Presence of Phosphorus or Sulfur on Gibbsite," Soil Science, 175, 3, 105-110, 2010. Based on surface charge analysis and pH studies, conclusions about reaction mechanisms were made. between the surface of the MPCM and the molybdenum ions, these mechanisms are presented in FIG. 13.

The equilibrium adsorption isotherm in the process of molybdenum absorption on the MRM was constructed using the results of measurements at a temperature of 298 ° K in the concentration range from 1 mmol / L to 94 mmol / L. As indicated in the previous section, the maximum adsorption capacity for molybdenum on MPCM is observed at pH 3. Therefore, unless otherwise indicated, experiments to construct an equilibrium isotherm were carried out at pH 3. Concentration profiles during the adsorption of molybdenum on MPCM from solutions with different concentrations show that approximately 60% of molybdenum was adsorbed in the first 4 hours of the experiment. During the experiments, in most experiments the equilibrium was established gradually after 24 hours.

The MRMM material contains amino groups available for the formation of specific coordination bonds with metal ions. The adsorption of metal ions, in the case of its dependence on pH, can be described by the following Langmuir equation for one site. The effect of pH was included by introducing the parameter "α", which depends on the pH of the solution. The equation is given below:

Maximum adsorption of metal ions (mmol / g)

where q is the adsorption capacity corresponding to the concentration of metal ions [M], q _m is the maximum adsorbed amount of molybdenum ions (mmol / g), [H ⁺ ] is the concentration of hydrogen ions, K _H and K _M are the equilibrium concentration. Equation 5 was used to correlate the adsorption capacity of the MPCM sample. The equilibrium data for molybdenum could correlate with the Langmuir equation within ± 5% of the experimental value. The constants in Equation 5 were obtained using non-linear regression of the experimental data and are presented in Table 3. It was noted that Equation 5 adequately represents the nature of the adsorption of molybdenum on MRM (Figure 14). These adsorption isotherms obtained at pH 3 showed that the adsorption isotherm is of Type I.

This indicates a monolayer adsorption of molybdenum on MRM. Table 3 shows the maximum adsorption capacity of MPCM according to Mo (VI) obtained using the Langmuir equation (Equation 5). It was found that the adsorption capacity of MPCM for molybdenum was equal to ~ 6.25 mmol Mo / g MPCM at 298 ° K, when the equilibrium concentration of Mo (VI) in the solution was 54.1 mmol / L and the initial pH of the solution was 3.0 (FIG. 14). NH ₂ groups in MRM are the main active centers for the adsorption of molybdenum. As can be seen in FIG. 13, two NH ₂ groups are necessary for the adsorption of one molybdenum ion. Other centers on the surface, for example, such as СН ₂ ОН or ОН groups in the MPCM, could participate in the adsorption of molybdenum at a solution pH of 3. Also, the adsorption capacity of the MPCM exposed to radiation with a dose of 50,000 crad was determined, determining the extraction (absorption) of molybdenum from an aqueous solution. As shown in Table 3, it was observed that the adsorption capacity of the irradiated MPCM practically (essentially) did not change.

* MPCM-I: Sample after irradiation with a dose of 50,000 crad, ⁶⁰ Co gamma source

To study the adsorption of Mo (VI) in the presence or absence of ions in solution in a dynamic mode, a column was used. For the manufacture of the column with a volume of 2.5 cm ³ with an inner diameter of 0.5 cm and a height of 3.2 cm, approximately 1.125 grams of MRM were used. During the experiment, the flow rate was 1 ml / min. The experiment lasted for 1500 minutes, and samples at the outlet of the column were taken at regular intervals. During this time, the carrier layer saturated, as shown by the concentration of Mo (VI) at the outlet. When the inlet concentration was 5.21 mmol Mo (VI) / l at pH 3 and the flow rate through the column was 1 ml / min, a molybdenum slip through the column was observed after passing 320 volumes of the support layer (FIG. 15a). The column was completely saturated after passing through 500 volumes of the carrier layer. Breakthrough curves were also obtained using a mixed solution containing 5.21 mmol of Mo (VI) / L and 153.8 mM NaCl / L at pH 6.86 and 4.0, respectively (Figure 15b). In both cases, the solution was passed through a column of a size similar to the size indicated above, while maintaining the same height of the carrier layer and the same flow rate. It was observed that leakage occurred through the column rapidly by passing 42 bed volumes ^of the mixed solution to a pH of 6.86, however, required approximately 125 bed volumes to breakthrough the column in the case of a mixed solution having a pH of 4.0. It is important to note that the breakthrough time for a molybdenum solution with a sodium chloride concentration of 153.8 mmol NaCl / L can be delayed by using a larger amount of MPCM adsorbent and a longer column. The aim of the experiment was to study the effect of the pH of the mixed solution at the inlet on the characteristics of the Mo (VI) slip from the column; therefore, no attempts were made to determine the layer length for prolonging the slip time for the mixed solution.

To assess the effectiveness of MRSM in the process of adsorption of technetium in the presence and absence of other ions from an aqueous solution in the pH range from 3 to 11, the long-lived isotope of technetium ( ⁹⁹ Tc) was used. Technetium is chemically inert and has several oxidation states ranging from I to VII. The predominant technetium ion in wastewater streams is pertechnetate ion (TcO ₄ ^- ). See Gu et al., Development of Novel Bifunctional Anion-Exchange Resin with Improved Selectivity for Pertechnetate sorption from contaminated groundwater, Environ. Sci. Technol., 34, 1075-1080, 2000. The adsorption of pertechnetate (TcO ₄ ^- ) from aqueous solutions on MRM was studied during the process under equilibrium by a periodic method according to the method set forth elsewhere. The effect of pH on the adsorption of technetium on MRM was analyzed in the pH range from 3 to 11 using a solution containing 0.11 μmol of technetium / L in the presence or absence of 0.9% NaCl, respectively. When studying the effect of pH on the adsorption capacity, the initial pH of the solutions was adjusted to the desired value by adding either 0.1 M HCl or 0.1 M NaOH. The pH of the solution during the adsorption was not controlled. After adsorption experiments, the solutions were filtered and the activity of ⁹⁹ Tc in the filtrate, which was taken into a vial (vial) for a given time, was evaluated using a liquid scintillation counter (Packard Tricarb 2900TR). The amount of technetium adsorbed on the MRM was determined by Equation 2.

Table 4 shows that the adsorption of technetium on MPCM does not depend on pH in the pH range of the solution from 3 to 11. It was observed that approximately 95% of the solution with a concentration of 1 μM technetium / L was adsorbed on MPCM in the pH range from 3 to 11, whereas removal (desorption) of technetium was reduced to 56% in the presence of 0.9% NaCl in the pH range from 3 to 11. As mentioned earlier, a positive charge is observed in the MPCM in the pH range from 3 to 7.5. FTIR spectrum of MPCM confirms the presence of groups - NH ₂ , CHOH and CH ₂ OH on the surface of MPCM (FIG. 4). It was hypothesized that the positive charge is due to the protonation of sites on the surface of the MPCM in the pH range from 3 to 7.5 and technetium is bound by covalent bonding to the positive centers on the surface of the MPCM. In the case of the presence of 0.9% NaCl in the solution, the adsorption capacity of MPCM by technetium decreased, since the pertechnetate ions had to compete with chloride ions in the solution. In addition, the adsorption of technetium in the pH range from 9 to 11 in the presence of a 0.9% NaCl solution can correspond to the ion exchange reaction that occurs in this pH range. The result, shown in Table 4, confirms that the MPCM exhibits high affinity (degree of affinity) for pertechnetate ion from aqueous solutions.

MPCM was also used to adsorb Mo (VI) and Tc (VII) simultaneously from a mixed solution containing 1 mmol of Mo (VI) / L and 0.11 μmol of pertechnetate / L in the presence or absence of 0.9% NaCl. It was found that MPCM adsorbs molybdenum and technetium from a solution simultaneously at a solution pH of 3. It was observed that approximately 95% of pertechnetate and 99% of molybdenum were adsorbed from a mixed solution with a concentration of 0.11 μmol of pertechnetate and 1 mmol of molybdenum. In the presence of molybdenum (MoO ₄ ^2- ) in solution, pertechnetate (TcO ₄ ^- ) had to compete for positive sites on the surface of the MPCM. In another experiment, the adsorption of technetium on MRM from a mixed solution containing 153.8 mmol NaCl / l, 1 mmol Mo (VI) / l and 0.11 μmol pertechnetate / l was studied. Table 5 shows that molybdenum (MoO ₄ ^2- ) was preferably adsorbed on the surface of the MPCM, while the adsorption of pertechnetate (TcO ₄ ^- ) was reduced to 55% from a mixed solution with a concentration of 0.11 μmol of technetium / L. It is believed that in the presence of 0.9% NaCl in solution at pH 3, the adsorption of pertechnetate (TcO ₄ ^- ) on the MPCM surface was reduced due to competition for surface centers with chloride ions. In another experiment, a column with an inner diameter of 1 cm was used to study the adsorption of pertechnetate on an MPCM. A column was prepared with an MPCM, which was first loaded with Mo (VI). A periodic equilibrium process was used to adsorb 6.25 mmol of Mo (VI) / g MPCM at 298 ° K, the equilibrium concentration of Mo (VI) in the solution being 54 mmol / L, and the initial pH of the solution was 3.0. Approximately 1.125 grams of MRSM loaded with Mo (VI) was used to prepare a 2.5 cm ³ layer. During the experiment, a saline (0.9% NaCl) solution, to which 0.25 mM pertechnetate / l was added (additive method), was passed through a column using a peristaltic pump at a flow rate of 1 ml / min.

In FIG. Figure 16 shows that the pertechnetate anion has affinity for accessible surface MRCM centers in the presence of a molybdenum anion (MoO ₄ ^2- ). It was observed that at 10 bed volumes, about 15% of the pertechnetate concentration at the inlet (to the column) was eluted with saline (0.9% NaCl) solution. It can be noted that approximately 60% of the concentration of pertechnetate at the inlet was obtained in the eluent, which was collected in 20 volumes of the layer (adsorbent) (FIG. 15). The column quickly reached saturation by technetium, while an additional volume of technetium-containing saline solution equal to 40 volumes of the layer (adsorbent) was passed through it. After reaching the saturation of technetium in the column, more than 95% of the technetium fed to the column was collected at the outlet of the column as an eluent. The aim of this study was to determine the maximum adsorption of pertechnetate (TcO ₄ ^- ) on the MPCM with a load of 6.25 mM Mo (VI) / gram MPCM. No attempt was made to determine the length (height) of the layer to reduce the release of pertechnetate from the MPCM layer loaded according to Mo (VI).

Although studies of batch processes and column processes show that MPCM has excellent Tc (VII) adsorption capacity, its removal from the adsorbent layer was a difficult problem. To study the desorption of technetium from an MPCM sample, a column was prepared with a technetium-loaded MPCM layer. Technetium adsorption on MRM was carried out under equilibrium in a batch process. It was observed that approximately 0.12 μM ⁹⁹ Tc per gram of MPCM was adsorbed from a ⁹⁹ Tc solution with a concentration of 0.48 μM / L at a temperature of 298 ° K. To study the desorption of ⁹⁹ Tc, 1.125 grams of MPCM containing 0.12 μM ⁹⁹ Tc / gram MPCM was used to prepare the column. Pertechnetate is soluble in water, so deionized water was used to regenerate technetium from the column. It was observed that only 1% of technetium was desorbed from the MPCM layer when water was passed in an amount equal to 10 volumes of the layer. Preliminary studies show that the complete extraction of technetium from MRM is difficult even when using different concentrations of NaCl solution. It was observed that the extraction of 10% ⁹⁹ Tc from the column required a volume of a 1.5% NaCl solution equal to approximately 50 volumes of the adsorbent layer. Similar amounts of low concentrated (<1 M) solutions of HCl, H ₂ SO ₄ and HNO ₃ acids were also used without any significant regeneration. In another experiment, to study the effect of oxidation on the adsorption / desorption of technetium on the oxidized sorbent / s of the oxidized sorbent MPCM, this MPCM sorbent was oxidized with potassium permanganate or hydrogen peroxide in various concentrations.

EXAMPLE 2

In another embodiment, the MPCM was oxidized with hydrogen peroxide at various concentrations, either in the presence or absence of transition metals, as catalysts. The temperature also changed. The study of the oxidation of MPCM by hydrogen peroxide was carried out in order to determine whether controlled oxidation alone could increase the extraction of technetium from the MPCM sorbent loaded with technetium. The concentration of hydrogen peroxide ranged from 1% to 5%. A batch process was used to adsorb technetium on the oxidized sorbent MPCM. Regeneration of technetium from oxidized MPCM was carried out on a column. A column was prepared containing 0.12 μmol ⁹⁹ Tc / gram of oxidized MPCM. Technetium with oxidized MPM was desorbed using a 0.9% NaCl solution. It was observed that the extraction of technetium was not as high as we would like, since from 10 to 17% of the available technetium was extracted from the layer of oxidized MRSM (Table 6). In addition, the adsorption of Mo (VI) on peroxidized MPCM decreased to 4.6 mmol / g compared with the amount of 6.25 mmol / g adsorbed on unoxidized MPCM.

EXAMPLE 3

MPM was also oxidized with potassium permanganate in solution. The concentration of sodium permanganate was determined by trial and error. The concentration of potassium permanganate and the pH of the solution ranged from 0.1% to 5% and from 3 to 11, respectively. The oxidation time ranged from 30 minutes to 24 hours. The surface charge of oxidized and non-oxidized MPCM loaded according to Mo (VI) was also determined to determine the adsorption pattern of pertechnetate (TcO ₄ ^- ) on oxidized MPCM.

It was observed that a permanganate solution containing 0.04 mmol Mn / L solution, in the pH range from 3 to 4.5 and for 12 hours, is sufficient to partially oxidize the MPCM in order to maximize the adsorption (capture) of molybdenum and the simultaneous release of technetium from the MPCM sorbent . The characteristics of oxidized MRM were evaluated by a periodic method to determine the adsorption of molybdenum from aqueous solutions. It was found that oxidized MPCM can adsorb 6.25 mmol of Mo (VI) / g MPCM at 298 ° K, and the equilibrium concentration of Mo (VI) in the solution was 54 mmol / L at pH 3.0.

In another experiment, two separate columns were prepared using oxidized MPCM and oxidized MPCM with a load of 6.25 mmol Mo (VI) / g, respectively. A 0.9% NaCl solution with the addition of approximately 0.11 μmol of pertechnetate (TCO ₄ ^- ) / L solution was passed through both columns at a flow rate of 1 ml / min. It is interesting to note that pertechnetate (TCO ₄ ^- ) was not adsorbed on oxidized MPCM in the presence or absence of a load according to Mo (VI) and that approximately 90% of pertechnetate (TCO ₄ ^- ) in the solution passed through both of these columns as eluent. The results confirm that pertechnetate (TcO ₄ ^- ) was not adsorbed on both of these columns with oxidized MPCM and with oxidized MPCM loaded according to Mo (VI). The aim of this work was to maximize the absorption of Mo (VI) and at the same time maximize the release of technetium from the surface centers (sites) of MRSM.

MRSM exhibits high affinity for both Mo (VI) and Tc (VII) from an aqueous solution. The surface charge of the MPCM loaded according to Mo (VI) revealed (FIG. 11) that Mo (VI) was adsorbed onto the MPCM via a complexation reaction to form the inner sphere of the complex. It can be noted that on the MPCM loaded according to Mo (VI), a positive charge is observed in the pH range from 3 to 4.5; most likely, as a result of this, the pertechnetate anion formed covalent bonds with accessible positive sites (centers) on the surface. Interestingly, the adsorption of pertechnetate on MPCM is approximately 55% from a solution containing 0.9% NaCl in the pH range from 3 to 8 (Table 4). Almost 95% of the solution of pertechnetate with a concentration of 1 mmol was adsorbed on the MPCM in the presence of 1 mmol of Mo (VI) in the solution. This confirms that pertechnetate (TCO ₄ ^- ) was adsorbed on the surface centers (sites) of MRSM.

The permanganate ion is amphiphilic in nature. In an acidic solution, potassium permanganate Mn (VII) ions are reduced to possible intermediates, such as Mn (VI), Mn (V), Mn (IV), and Mn (III), which are eventually reduced to Mn (II) . - See Dash et al., "Oxidation by Permanganate: Synthetic and mechanistic aspects" Tetrahedron, 65, 707-739, 2009. It is reported that the permanganate ion (MnO ₄ ^- ) in potassium permanganate is chemically active in the acid-catalyzed chitosan oxidation reaction . See Ahmed et al "Kinetics of Oxidation of Chitosan polysaccharide by Permanganate Ion in Aqueous Perchlorate solutions" Journal of Chemical Research, v 2003, n 4, p. 182 - 183, 2003. The reactions between the MnO ₄ ^- and H ion are given below. ⁺ possible in an acidic environment:

Due to the protonation of the MnO ₄ ^- ion, an HMnO ₄ molecule can form in an acidic solution, which is also a strong oxidizing agent. . See Sayyed et al, "Kinetic and Mechanistic Study of Oxidation of Ester by KMnO _4" International Journal of ChemTech Research, v 2, n 1, p 242-249, 2010. The formation of the colloidal MnO ₂ MnO probably due response ₄ ^- with H ⁺ and depending on the acidity of the solution, it can further react with H ⁺ , giving Mn ²⁺ in solution. Ahmed et al., 2002, reported the oxidation of chitosan with permanganate as a reaction that leads to the formation of diketocarboxylic acids of chitosan derivatives. See Ahmed et al., "Kinetics of Oxidation of Chitosan polysaccharide by Permanganate Ion in Aqueous Perchlorate solutions" Journal of Chemical Research, v 2003, n 4, p, 182 183, 2003.

In the acid-catalyzed oxidation reaction of MPCM with permanganate, permanganate ion (MnO ₄ ^- ) can be considered as an active oxidizing agent. The effect of the oxidation of MPCM with permanganate on the simultaneous adsorption processes on the surface and the release of Mo (VI) and Tc (VII) from the surface of the oxidized MPCM was determined by analyzing the surface charge of the MPCM sample. The oxidation of MRM by potassium permanganate changes its selectivity of adsorption from an aqueous solution. In FIG. Figure 17 shows the surface charge pattern of an MPCM-loaded Mo (VI) sample in the presence of oxidation and in the absence of oxidation. As regards the unoxidized MPCM sample with a load of Mo (VI), it seems that the surface gradually increased in the pH range from 4.5 to 3. Therefore, in this pH range, pertechnetate formation of covalent bonds with positive centers on the surface of the MPCM loaded on Mo is possible. At pH <2.9, the difference between the initial pH and pH at the time of equilibrium establishment for the MPCM sample with Mo (VI) load was insignificant, which means the complete protonation of the MPCM sample.

The study of the surface charge of oxidized MPCM loaded with Mo (VI) shows an almost zero charge in the pH range from 3 to 4.5, compared with the sample of unoxidized MPCM loaded with Mo (VI) (FIG. 17). In an acidic medium in the pH range from 3 to 4.5, the surface functional groups of unoxidized MPCM have a positive charge, as a result of which they can also undergo a reaction with MnO ₄ ^- during oxidation. It is believed that the trivalent manganese ion (MnO ₄ ^- ) enters the MPCM porous matrix and partially oxidizes the positive surface functional groups, donating electrons, followed by reduction in solution to the Mn ^{2+ ion} . The formation of colloidal manganese in the solution was also controlled, maintaining the pH of the solution in the range from 3 to 4.5, more specifically, at pH 4. In addition, the ratio of the number of Mn ^{2+ ions} to the positive surface centers of the MPCM promotes further adsorption of Mn ²⁺ on the MPCM surface. Both batch processes and column studies showed that technetium was not adsorbed on oxidized MPCM loaded with Mo (VI), while at the same time it showed high affinity for a sample of unoxidized MPCM loaded on Mo (VI). This indicates that the lack of a positive charge on the surface of the loaded Mo (VI) oxidized MPCM does not stimulate technetium to form a covalent bond, in contrast to the surface of the unoxidized MPCM loaded on Mo (VI). It is interesting to note that technetium was not adsorbed on oxidized MPCM, while almost 95% of a 1-mmolar solution of technetium was adsorbed on non-oxidized MPCM. This confirms that technetium was adsorbed on the surface of unoxidized MPCM and was not adsorbed on oxidized MPCM due to the formation of covalent bonds.

The study of periodic equilibrium adsorption processes was carried out by exposing the oxidized MPCM with 1% Mo (VI) solution with the addition of 5.0 ml of ⁹⁹ Mo (2 μCi / ml). First, a 1% solution of molybdenum (compound) was prepared by dissolving 4.5 ml of ammonium hydroxide and 1.5 g of MoO ₃ in 95 ml of deionized water. The mixture was stirred until complete dissolution of MoO ₃ . A solution containing 5.0 ml of ⁹⁹ Mo (2 mCi ⁹⁹ Mo / ml) was thoroughly mixed with 97.5 ml of a 1% molybdenum solution. The pH of the solution with the additive was adjusted to 3 by adding a 0.1N solution of either HCl or NaOH. The final specific activity of Mo (VI) in the solution was 78.12 μCi / ml.

About 0.5 grams of oxidized MPCM was placed in a 125 ml plastic bottle containing 50 ml of the additive solution (additive method). Then the solution was placed on a rocking chair (160 rpm) and stirred for 3 hours at 25 ± 1 ° C. Another series of experiments was also performed to duplicate the results. After 3 hours, the final pH of the solution was fixed and the solution was centrifuged for 5 minutes at 3000 rpm to separate the MPCM from the supernatant solution. Then, the MPCM loaded with Mo (VI) was washed twice with deionized water to remove the smallest amounts of Mo (VI) from its surface. MRSM loaded with Mo (VI), and the supernatant and wash solutions were analyzed for molybdenum content using a dose calibrator and ICP-MS (inductively coupled plasma mass spectrometer). It was observed that, at equilibrium, the capacity of the oxidized MPCM was 2.47 mmol Mo / g MPCM, where the activity of 1300 μCi is due to the addition of ⁹⁹ Mo.

Activity of ⁹⁹ Mo and ^99m Tc was evaluated using both a dose calibrator and a gamma spectrometer. The dosimeter (Atomlab 400) was equipped with a small lead sampler that effectively protected against ^99m Tc of gamma radiation, while at the same time passing most of the ⁹⁹ Mo gamma radiation through a protective shield into the detector. Thus, the readings taken while the sample is in a shielded vessel relate exclusively to the activity of Mo. The readings taken without a screen are the sum of the activities of both Mo and ^99m Tc.

After experiments on periodic adsorption, MPCM loaded with both ⁹⁸ Mo and ⁹⁹ Mo was transferred to a column (0.5 cm × 3.2 cm with particles of polytetrafluoroethylene (PTFE) at the bottom of the column). The two ends of the column were covered with a silicone membrane. The column was thoroughly washed with deionized water to completely remove the molybdenum solution on the surface of the MPCM. The washed sample was taken from the column into evacuated (evacuated) vials. The column was eluted with brine (0.9% NaCl) after it had withstood its maximum time required for accumulation in the ^99m Tc column, the daughter product of the decay remaining in the ⁹⁹ Mo column. The column was washed using 9 ml of saline, which was successively collected in 3 separate evacuated vials, 3 ml each. The eluate was collected from the column at predetermined intervals. After each selection, the eluate was analyzed for molybdenum and manganese leaving the column on an inductively coupled plasma quadrupole mass spectrometer (ICP-MS) with an external reference signal source. Activity due to pertechnetate or ⁹⁹ Mo was evaluated using a dose calibrator or gamma spectroscopy.

In FIG. Figure 18 shows the elution profile from a column filled with 0.5 grams of MPCM with a load of 2.47 mmol Mo (VI) / gram of oxidized MPCM, with an activity of 1300 µCi due to adsorbed ⁹⁹ Mo. Elution from the column with saline (0.9%) NaCl) was started the day after the preparation of the column and the elution was continued for 8 days. Note: the first series of elution (Elution 1) was performed 8 hours after column preparation to verify the desorption pattern of ^99m Tc from the MPCM column. The remaining elution series, from number 2 to number 8, was carried out at 24-hour intervals, except that the elution of number 5 was carried out at least 45 hours after the elution of number 4. It was found that the elution efficiency of the ^99m Tc decay product from the column varies in the range from 75 to 90% (FIG. 18). As shown in FIG. 18, during Elution 1, more than 80% of the activity due to ^99m Tc was obtained by passing 9 ml of saline (0.9% NaCl), with 62% of the available ^99m Tc activity being eluted with the first 3 ml of isotonic saline. The second elution, Elution 2, was performed 24 hours after the first elution, and it was seen that ^99m Tc activity in the column ranged from 70% to 90% and that ^99m Tc could be recovered using 3 to 9 ml of NaCl solution. In all cases, the eluate was transparent and its pH ranged from 6 to 7. The column was washed (elution) continuously for 8 days, on average ~ 82% of the total ^99m Tc was eluted from the column.

In FIG. 19 shows the percentage of ^99m Tc and Mo (VI) released from the column over 8 days. The concentration of Mo (VI) in the eluates ranged from 1% to 3% of 6.25 mmol of Mo (VI) / gram MPCM in the column. The capture of any amount of molybdenum passing through the column (i.e., preventing the passage of molybdenum from the column) by passing through the MPCM with the catalyst is possible, as shown in FIG. 15, while the concentrations of Mo (VI) and Mn (VII) in the eluent are reduced to extremely low levels. Another way to control the breakthrough of molybdenum from the column can be carried out by maintaining the pH of the saline solution (0.9% NaCl) in the range from 4 to 4.5 (FIG. 15). In this case, an additional pre-column (protective column) to control the leakage (outflow) of Mo (VI) from the column is not necessary.

EXAMPLE 4

The production of ⁹⁹ Mo by the neutron capture method has attracted attention as an alternative to the method of obtaining ⁹⁹ Mo from fission products (uranium) due to problems associated with the proliferation of (nuclear) weapons. ⁹⁹ Mo obtained by neutron activation of natural molybdenum could provide a less complex, less expensive and more convenient domestic method for producing and using ^99m Tc.

However, it is obvious that the specific activity obtained by the radiation method of neutron capture is not high enough to create small chromatographic generators. But this limitation can be overcome by using an adsorbent, for example, such as MPCM, which has an increased adsorption capacity for molybdenum. It has been shown that MPCM is capable of adsorbing more than 6.25 mmole of Mo (VI) / gram (600 mg Mo (VI) / g MPCM) from an aqueous solution of pH 3, which is also applicable to ⁹⁹ Mo, which is easily obtained by the (n, γ) reaction natural molybdenum. In this case, the generator consists of an MPCM layer loaded with ⁹⁹ Mo, thereby combining the efficiency of the chromatographic generator and the use of (n, γ) ⁹⁹ Mo. In the case of using an adsorbent in a ^99m Tc / ⁹⁹ Mo generator, the MPCM is capable of holding up to 60% by weight of its weight compared to only 0.2 weight. % for alumina. The effectiveness of MPCM as an adsorbent for creating a ⁹⁹ Mo / ^99m Tc generator was studied using a 1% solution of Mo (VI) supplemented with ⁹⁹ Mo (2 mCi / ml). It was observed that MPCM adsorbed Mo (VI) with the addition of ⁹⁹ Mo in accordance with its capacity demonstrated by adsorption from an aqueous solution with pH 3. It was also observed that ^99m Tc, which was the decay product of ⁹⁹ Mo, was eluted with physiological (0.9%) saline solution with a yield of more than 80% when eluting. A typical process scheme for producing ^99m Tc / ⁹⁹ Mo generator based MRFM as the adsorbent is shown in Figure 20.

EXAMPLE 5

In an experiment to maximize the adsorption of Mo (VI) and increase the release of technetium from a column prepared using a molybdenum-loaded MPCM composite, the MPCM composite was oxidized with sodium hypochlorite (NaClO ₂ ) and sodium chlorite (NaOCl), respectively. The concentration of sodium chlorite or sodium hypochlorite in solution and the oxidation time were determined by trial and error. The concentration of sodium chlorite and the pH of the solution were varied from 1 mmol / L to 10 mmol / L and from 3 to 11, respectively. The oxidation of MRSM with either sodium chlorite or sodium hypochlorite was carried out at a solid to liquid ratio of 1: 100. The oxidation time varied from 30 minutes to 24 hours. Both in the case of sodium chlorite and in the case of sodium hypochlorite, it was observed that a solution containing ~ 0.02% chlorine, calculated as Cl ₂ , in the pH range of 3 to 4.5 and an oxidation time of 2 hours was sufficient for partial oxidation of MPMM to facilitate the adsorption of molybdenum , as well as for the release (desorption) of technetium from the sorbent MPCM. MPCM composites that have been partially oxidized with sodium chlorite and sodium hypochlorite are designated MPCM-ClO ₂ and MPCM-OCl in this application, respectively. The effectiveness, characteristics of MPCM-ClO ₂ and MPCM-OCl were evaluated by the adsorption of molybdenum from aqueous solutions by periodic methods. It was noted that oxidized MPCM can adsorb approximately 6.25 mM (~ 600 mg) Mo (VI) per g of oxidized MPCM at 298 ° K, when the equilibrium concentration of Mo (VI) in solution is 54 mmol / L at pH 3.0.

The analysis of the surface charge of molybdenum-loaded non-oxidized MPCM and molybdenum-loaded MPCM-ClO ₂ was carried out using the methods described above. Similar experiments on surface charge analysis were also performed for molybdenum-loaded MPCM-OCl and the results were compared with the surface charge of the unoxidized MPCM composite. The pattern of results obtained by analyzing the surface charge of MPCM-CIO ₂ loaded with molybdenum and MPCM-OCl is similar to the pattern for molybdenum-loaded MPCM oxidized with potassium permanganate.

To evaluate the adsorption capacity by Tc-99, two separate columns were prepared containing molybdenum-loaded MPCM-ClO ₂ and MPCM-OCl, respectively. For comparison, tests for the passage of TC-99 through these oxidized MCPM composites were carried out according to the methods described above. The results confirmed that pertechnetate (TcO ₄ ^- ) was not adsorbed on both MPCM-ClO ₂ and MPCM-OCl loaded with Mo (VI).

Table 7 compares the effects of various oxidizing agents on the release of technetium from a column prepared with oxidized MPCM. The oxidized MPCM composites shown in Table 7 were exposed with a 1% molybdenum solution supplemented with the exact amount of molybdenum-99. The activity of molybdenum-99 varied from 45 mCi to 1.39 Ci (at the end of irradiation, or EOI), respectively. To prepare the corresponding chromatographic columns, molybdenum-loaded MPCM composites oxidized by various oxidizing agents were used. Then the columns were washed with NaCl solution, the results are shown in Table 7.

The release of technetium from the column was almost 100% when the initial activity of Mo-99 in the column was approximately 45 mCi (Table 7). The release of technetium from the column was relatively very low for all oxidizing agents when Mo-99 with increased specific activity was used in the column. Without any connection with any theory, it is believed that, with increased activity, technetium was reduced from Tc (VII) to Tc (IV) and the reduced anionic pertechnetate probably formed covalent bonds with free sites on the surface of the MPCM composite. The release of technetium from the column was approximately 10% when molybdenum-99 with an activity of 900 mCi was loaded onto an MPCM sample oxidized using 31 mM potassium permanganate (Table 7). This composition, when passing the eluent, also released more manganese compared to the MPCM composite, which was oxidized with 6.3 mM potassium permanganate. With increased activity of Mo-99 (1.39 Ci in EOI) in the column for MPCM-ClO ₂ and MPCM-ClO composites, a slight increase in the percentage of technetium released from the column was observed compared to composites that were oxidized with potassium permanganate and hydrogen peroxide (Table 7).

At a higher specific activity (1.39 Ci in EOI) of the molybdenum in the column, the release of technetium from the column was significantly reduced compared to the column prepared using the MPCM composite loaded with molybdenum-99 with low specific activity. Without regard to any theory, it is believed that with increased activity, the valency corresponding to the oxidation state of the metal ions that are in the column can change; this decreases the release of technetium from the column. It is believed that the presence of an oxidizing agent in the molybdenum solution could support the MPCM composite and molybdenum in the solution in the oxidized state during the entire adsorption cycle, which can contribute to the release of technetium from the column. In addition, the addition of an oxidizing agent in an eluent saline solution was also considered in order to further increase the release of technetium-99 from a column loaded with oxidized MPM molybdenum.

The MPCM-ClO ₂ and MPCM-OCl composites were studied further in order to evaluate their effectiveness with respect to the adsorption of molybdenum in the presence of various concentrations of the oxidizing agent in the solution. The adsorption study was carried out for 24 hours using various concentrations of sodium chlorite and sodium hypochlorite (from 5 mm to 50 mm), with the addition of 1% molybdenum in solution (obtained from a molybdenum salt without radioactive molybdenum (Mo-99)). In all experiments, the pH of the molybdenum solution was first adjusted to ~ 3.0. Samples were taken at various intervals and analyzed for sorption (absorption) of molybdenum on the composite. Table 8 shows that in the presence of sodium chlorite or sodium hypochlorite, the absorption capacity of molybdenum by the oxidized MPCM composite ranges from 5.21 mM (500 mg / g) to 6.25 mm (600 mg / g) of oxidized MPCM.

Molybdenum began to slowly precipitate from solution after 12 hours of exposure, when the concentration of oxidizing agent in the solution was 45 mM or higher. No precipitation of molybdenum from the solution was observed when the concentration of either sodium chlorite or sodium hypochlorite ranged from 5 mM to 40 mM. Molybdenum did not precipitate from the solution during the first 4 hours of exposure to sodium hypochlorite at any concentration used in this study.

It was found that sorption (absorption) of molybdenum on MPCM-ClO ₂ constantly occurred in the presence of all concentrations of sodium hypochlorite in a 1% molybdenum solution (Table 8). Compared with the results obtained using an oxidizing agent-free molybdenum solution, the sorption of molybdenum on MPCM-ClO ₂ was approximately 6.25 mM / g from a 1% molybdenum solution containing 25 mM hypochlorite (NaOCl) in solution (Table 8). This suggests that the presence of hypochlorite in a molybdenum solution does not significantly affect the MPCM composite, partially oxidized with sodium chlorite.

Thus, it was believed that in this experiment, MPCM-ClO ₂ adsorbs molybdenum in the presence of sodium hypochlorite (NaOCl) at various concentrations as an oxidizing agent in a 1% Mo solution. MPCM-ClO ₂ loaded with molybdenum was then used to prepare a chromatographic column. Sodium chlorite and sodium hypochlorite were also mixed with (physiological) saline in order to study their oxidative effect on the release of both technetium and molybdenum from the column. The columns were then washed with brine mixed with sodium chlorite and sodium hypochlorite, respectively, at a concentration of 5 mM at pH 4. Before passing through the column, an exact amount of Tc-99 was also added to the eluate (stoichiometrically equivalent to ~ 1 Ki Tc-99m per 10 ml) .

More than 99% TC-99 passed through the column in the presence of either sodium chlorite or sodium hypochlorite as an oxidizing agent in the eluent, without adsorption in the column (Table 9). The release of molybdenum from the column during the elution with saline (sodium chloride) mixed with sodium hypochlorite was similar to the release from molybdenum from the column eluted with saline (sodium chloride) mixed with sodium chlorite (Table 9). For example, columns prepared with MPCM-ClO ₂ adsorbing molybdenum from a solution containing 1% molybdenum and 25 mM sodium hypochlorite were washed with 5 mM sodium chlorite and sodium hypochlorite, respectively (Table 9). In the case of a sodium chloride solution with sodium chlorite, it was found that the release of molybdenum was approximately 2% of the 6.25 mM molybdenum adsorbed on the MPCM-ClO ₂ used to fill the column, while it was found that approximately 7.5% of the molybdenum was released with a similar column that was eluted with a mixed solution of sodium hypochlorite and sodium chloride, as shown in Table 9. From this study, it becomes clear that MPCM-ClO ₂ is capable of adsorbing approximately 6.25 mM of molybdenum from a solution containing 1% molybdenum and 25 mm sodium hypochlorite. Regarding the chromatographic column prepared using molybdenum-loaded MPCM-ClO ₂ and then eluted with a mixed solution of sodium chloride and sodium chlorite with the addition of an exact amount of Tc-99, it was found that this system was able to retain the maximum amount of molybdenum and also release columns the maximum number of TC-99.

The effect of various concentrations of sodium chlorite in the eluent on the release of molybdenum and technetium from the column was also studied. Columns were prepared with MPCM-ClO ₂ , which adsorbed molybdenum from a solution containing 1% molybdenum and 25 mM sodium hypochlorite. Then the columns were washed with saline (NaCl) mixed with sodium hypochlorite in various concentrations. Then the columns were washed with saline (NaCl) mixed with sodium chlorite at various concentrations (Table 10). The concentration of sodium chlorite in saline solution ranged from 5 mm to 20 mm. Also, TC-99 additives (stoichiometrically equivalent to ~ 1 Ki TC-99m per 10 ml) were added to the elution mixtures before passing through the column. It was observed that more than 99% of technetium-99 passed through the column in the presence of sodium chlorite as an oxidizing agent (concentration from 5 mM to 20 mM) in the eluent, not adsorbing in the column (Table 10). The amount of molybdenum released (desorbed) from the column was approximately 2% to 5% of the amount of molybdenum deposited on the column when the concentration of sodium chlorite in the saline solution was 5 mM and 20 mM, respectively. This suggests that in order to obtain molybdenum-free technetium, it is advisable to use a pre-column in the eluent solution.

EXAMPLE 6

The efficiency of the MPCM-ClO ₂ composite as an adsorbent for creating a ⁹⁹ Mo / ^99m Tc generator was evaluated by exposing it with a 1% molybdenum solution obtained by radiation neutron capture with an activity of 13.9 mCi / ml, irradiation was carried out at the MURR reactor (at the University Research Reactor Missouri State, USA, the University of Missouri Research Reactor, USA,). A similar experiment was also performed on POLATOM using a 1% solution of natural molybdenum with the addition of molybdenum, a fission product (~ 1.89 Ci ⁹⁹ Mo / g Mo). Experiments with periodic adsorption of molybdenum on an MPCM-ClO ₂ composite were carried out at room temperature, while the initial pH of the solution in both experiments was approximately 3.0. The sorption of molybdenum on the composite in both experiments amounted to about 60% of the molybdenum present in the solution. In each experiment, a ⁹⁹ Mo / ^99m Tc generator was prepared, consisting of a 6 ml column containing an MPCM-ClO ₂ composite loaded with ⁹⁹ Mo. ^99m Tc, a ⁹⁹ Mo degradation product, was eluted with saline (0.9% NaCl) mixed with sodium chlorite as an oxidizing agent. Table 11 shows the elution characteristics for a typical generator prepared by exposing 1 g of MPCM-ClO ₂ composite with 100 ml of 1.39 Ci ⁹⁹ Mo in a solution with a total molybdenum concentration of ~ 1% with an initial pH of ~ 2.8. Analysis of the distribution of activity showed the adsorption efficiency of Mo 63.4%. In these experiments, the exposure time of the MPCM-ClO ₂ composite with a molybdenum solution was 24 hours. After the adsorption cycle, the composite was thoroughly washed with deionized water to remove any molybdenum residues from the surface.

Table 11 shows that the amount of TC-99m released from the column increases with increasing concentration of sodium chlorite in the eluent solution. A concentration of about 20 mM sodium chlorite in the eluent, a saline solution with a pH of 4.0, is apparently sufficient to extract more than 95% Tc-99m from the column with an initial column activity of about 1 Ci.

The Tc-99m radioisotope, in the form of an intermediate solution, was then passed through an alumina pre-column as an adsorbent. Elution results were collected for three consecutive days and these results showed that> 90% of the theoretical amount of ^99m Tc available was eluted from the generator. The ⁹⁹ Mo content in the eluent was less than 0.15 µCi ⁹⁹ Mo per mCi ^99m Tc. The eluent solution was further treated with either 1 M sodium thiosulfate or sodium sulfite to neutralize the oxidizing agent present in the solution. Sodium sulfite can effectively neutralize the oxidizing agent, which may be in the final eluent. A typical composition of the eluent obtained in these experiments is presented in Table 12.

EXAMPLE 7

We also studied the use of potassium dichromate additives (about 200 mg of chromate) and 5% cerium oxide as oxidizing agents with saline, which was used with some success for washing the column with MPCM-ClO ₂ loaded with molybdenum. In the case of potassium dichromate or cerium oxide in saline as an eluent, the release of TC-99 from a column prepared with molybdenum-loaded composite MPCM-ClO ₂ was about> 75%. A significant amount of chromium or cerium was present in the final eluent solution, which indicates the necessity of using a pre-column to obtain technetium that does not contain an oxidizing agent in the final eluent.

EXAMPLE 8

The effect of temperature and the ratio of solids to liquids in the presence of an oxidizing agent (sodium hypochlorite) in solution on the sorption of molybdenum on the MPCM-ClO ₂ composite was studied. Studies of periodic processes were carried out at various given temperatures in accordance with the methods described above. For each experiment, about 1 gram of the MPCM-ClO ₂ composite was kept in 100 ml of a 1% molybdenum solution in the presence of an oxidizing agent (25 mM NaOCl) for 4 hours at pH ~ 3.0 (data not shown). Preliminary data shown in Figure 21 show that the sorption of molybdenum on the MPCM-ClO ₂ composite at a solution temperature in the range from 25 ° C (298 ° K) to 70 ° C (343 ° K) changed only slightly (in the range from 5.38 mM up to 5.53 mM Mo (VI) / gram MPCM-ClO ₂ composite). In most cases, approximately 50% of the molybdenum present in the solution was adsorbed on the MPCM-ClO ₂ composite in the first half hour of the experiment without any signs of precipitation, followed by a slow movement to equilibrium.

The heat of adsorption at various loads of molybdenum on the oxidized MPCM is shown in Figure 22. The heat of adsorption of molybdenum decreased with increasing load, which can be attributed to the heterogeneity of the surface and the multilayer coating. At a higher load, the heat of adsorption approached the integral heat of adsorption (ΔН value). Without regard to any theory, it is believed that the surface was saturated with molybdenum, and the heat of adsorption approached the equilibrium adsorption value. The initial decrease in the heat of adsorption can be attributed to the heterogeneity of the surface and the multilayer coating. A subsequent increase in the heat of adsorption can be attributed to secondary interactions between the adsorbed molybdenum ions, which are known to form complex molecules on a solid surface. It was believed that the adsorption centers on the surface of the composite will be energetically homogeneous and, therefore, the heat of adsorption obtained should be constant. However, it is likely that the surface of the composite becomes energetically heterogeneous due to its microporosity.

The periodic studies were carried out by changing the ratio of solid to liquid in the presence of 25 mM sodium hypochlorite as an oxidizing agent in a 1% molybdenum solution at 25 ° C (298 ° K). Almost 95% of the available molybdenum from a 1% solution was adsorbed on the MPCM-ClO ₂ composite during the exposure time within 1.0 hour, when the ratio of solid to liquid substances was 2: 100 (2 grams of MPCM-ClO ₂ in 100 ml of a 1% solution of molybdenum in the mixture with 25 mM sodium hypochlorite). It was found that this ratio is the optimal adsorbent dose only for absorption (sorption) of molybdenum on MPCM-ClO ₂ in the presence of 25 mM sodium hypochlorite in a 1% molybdenum solution. As for unoxidized MPCM, with the same ratio of solids to liquid and at the same exposure time, the absorption of molybdenum was almost 35% less compared with the oxidized composite MPCM (MPCM-ClO ₂ ). The reason for this phenomenon, at least in part, is apparently the modification of the surface charge of the MPCM by oxidation and an increase in the ratio of solids to liquids in the process.

EXAMPLE 9

Preliminary experimental data showed that the oxidized MPCM composite is capable of adsorbing approximately 50 to 60% of the existing molybdenum from the solution after exposure for 24 hours. It is also estimated that almost 28% of ⁹⁹ Mo activity is lost due to decomposition within 24 hours of the adsorption cycle. In addition, other 10 to 15% of ⁹⁹ Mo activity is lost during the process and operations with the generator. 23 shows experimental data for a 0.5 Ci generator (during elution) of ⁹⁹ Mo / ^99m Tc described above, which typically requires about 1.6 to 1.8 Ci ⁹⁹ Mo (EOI) from the start.

However, experiments carried out by a periodic method indicate that at a temperature of 25 ° C (298 ° K) the MPCM-ClO ₂ composite is able to adsorb almost 99% of the available molybdenum from a 1% molybdenum solution mixed with 25 mM sodium hypochlorite over time exposure for 1 hour using a ratio of solids and liquids 2: 100. It was found that after thorough washing of the MPCM-ClO ₂ composite loaded with molybdenum with deionized water, at least 90% (or up to 95%) of molybdenum remains in the composite, which can be used to prepare the column for the generator. This ultimately reduces the loss of activity of ⁹⁹ Mo during the adsorption cycle and during the process and operations with the generator. Taking into account losses of ⁹⁹ Mo during a 24-hour adsorption cycle for preparing a 6 ml column for a generator with an activity of 0.5 Ci (during elution), it seems that a generator with a specific activity of 1.5 Ci to 2 Ci is possible if the solid to liquid ratio is maintained 2: 100 at a solution temperature of 25 ° C (298 ° K) during the adsorption cycle (Figure 23). It is also estimated that a ⁹⁹ Mo / ^99m Tc generator with an activity of 4 to 6 Ci based on ⁹⁹ Mo obtained by neutron capture is possible by adjusting the volume and number of columns in the system.

EXAMPLE 10

About 4 g of chitosan was added to 300 ml of deionized (DI) water with 1 ml of acetic acid and stirred for 2 hours at 70 ° C to form a gel. About 4 ml of HCl was added to the chitosan gel and kept under stirring for another 1 hour at 70 ° C.

In this example, an amorphous titanium dioxide gel was prepared by controlled hydrolysis and condensation of titanium isopropoxide. See Hasan, S., Ghosh, T.K., Prelas, M.A., Viswanath, DS, and Boddu, VM "Adsorption of uranium on a novel bioadsorbent chitosan coated perlite" Nuclear Technology, 159, 59-71, 2007; Schattka, JH, Wong, EH-M., Antonietti, M., and Caruso, RA "Sol-gel templating of membranes to form thick, porous titania, titania / zirconia and titania / silica films" Journal of Materials Chemistry, 16, 1414-1420, 2006; Agoudjil, N., and Benkacem, T. "Synthesis of porous titanium dioxide membranes" Desalination, 206, 531-537, 2007. Equal volumes of isopropanol (IP) and DI water were mixed in a specific amount of titanium isopropoxide with constant stirring at 70 ° C. . With constant stirring, HCl was added dropwise and heated at 70 ° C to obtain a clear solution. The hydrolysis and condensation reaction was controlled by controlling the ratio of water and titanium to H ⁺ and titanium in the mixture, respectively. The final pH of the mixture was approximately 2.0 and the final stoichiometric ratio of the reactants was Ti: IP: H ₂ O: H ⁺ = 0.0132: 0.39: 1.67: 0.01. Depending on the ratio of reagent concentrations, the gelation time ranged from 25 to 45 minutes.

At a time comprising approximately 75% of the total gelation time, a solution of amorphous titanium dioxide obtained by the sol-gel method was mixed with chitosan gel. The mixture was stirred at 70 ° C. for another 1 hour to complete the reaction of chitosan and amorphous titanium dioxide. The reaction with glutaraldehyde was carried out by adding dropwise about 6 ml of a solution of glutaraldehyde with a concentration of 50% to the acid gel of chitosan titanium dioxide with continuous stirring at 70 ° C. The pH of the final mixture was approximately 1.0. The mixture was kept under continuous vigorous stirring at 70 ° C for another 1 hour to obtain a semi-solid gel.

The resulting mass was thoroughly washed with 2% monoethanolamine, removing unreacted glutaraldehyde. Then the mass was suspended in a 0.1 M NaOH solution from 4 to 6 hours. The crosslinked mass was separated from the solution and washed with 0.1 M HCl and then with deionized water (DI) until the pH of the washed solution reached 7. Then, the crosslinked mass was dried in a vacuum oven overnight at 70 ° C. The resulting composite (composite material) based on glutaraldehyde crosslinked chitosan is referred to herein as “CGST”.

In the case of the CGST sample, it was found that the peak intensity at 1590 cm ⁻¹ became weaker, indicating that amide groups may participate in crosslinking reactions using (derivatives) of titanium. In the spectra of all three samples there is a band of the carbonyl group (-CONHR) at about 1650 cm ^-1 . The stretching bands CN of primary amines fall in the region between 1350 and 1150 cm ¹ .

In the spectra of chitosan and CGST, respectively, there is a peak at 1170 cm ¹ (FIG. 21). When compared with the chitosan spectrum in the spectrum of CGST samples, the peak at 1170 cm ^-1 becomes weaker and a new peak appears at 1090 cm ^-1 .

For the peak that appears at 1090 cm ⁻¹ , noticeable shifts are observed due to C = O (C — O!) Stretching vibrations of the ether bond.

In the range from 1000 cm ^-1 to 1200 cm ^-1 , two peaks are observed in the chitosan spectrum at 1157 cm ^-1 and 1070 cm ^-1 , corresponding to stretching vibrations of the CO bond at the C3 atom of chitosan (OH group of the secondary alcohol) and stretching vibrations of the bond C-O at the C6 atom of chitosan (OH group of the primary alcohol), respectively.

Compared with the band of the C — O group at 1070 cm – ¹ in the chitosan spectrum, the absorption peak of the secondary hydroxyl group of the CGST samples becomes “folded”, as shown in FIG. 24, and the OH band became less intense and shifted from 3498.0 to 3450.0 cm ^-1 , which suggests that OH groups of chitosan can react with glutaraldehyde in the presence of an acid catalyst through the formation of hemiacetal. The fact of a decrease in the chemical bond constant С-О and a significant decrease in the intensities of the peaks of stretching vibrations of OH groups (from 1000 to 1200 cm ^-1 ) confirms the presence of a complexation reaction between glutaraldehyde and surface oxygen-containing functional groups, for example, such as the secondary hydroxyl group of chitosan. As for the CGST sample, then, apparently, titanium oxide is involved in the reaction with the amino group of chitosan (FIG. 24).

Various variants of a microporous chitosan-based microporous composite material (composite) (MPM) were prepared by crosslinking with glutaraldehyde at 70 ° C. in the presence of a catalyst. MPCMs were obtained in the laboratory by phase inversion of a liquid suspension of chitosan dissolved in acetic acid and aldol condensation of glutaraldehyde for better exposure of amino groups (NH ₂ ). MRMS was characterized by scanning electron micrograph (SEM), which showed its porous nature. Also obtained two derivatives based on MPCM, such as oxidized MPCM and MPCM obtained with acid as a catalyst. The study of the stability of MPCM was carried out at 50,000 krad, using a ⁶⁰ Co emitter as a source of γ radiation. The FTIR, XPS, and EDS X-ray microanalysis spectra showed that the intensities of the C, O, and N peaks in the MPCM after irradiation did not change significantly. As for the adsorption of Mo (VI) from an aqueous solution at 298 ° K, the MPCM can retain adsorbed Mo (VI) in an amount of up to 60% of its own weight. MPCM and its derivatives demonstrate the ability to simultaneously adsorb ⁹⁹ Mo and release the daughter product of its ^99m Tc decay both in a batch process and in equilibrium. It was also observed that ^99m Tc, which was the decay product of ⁹⁹ Mo, was eluted with physiological (0.9% NaCl) saline in an elution yield of more than 80%. The results show that the yield of ^99m Tc as a result of elution is high, and the slip of Mo (VI) from the continuous column is minimal, therefore, MPCM and its derivatives can be used as adsorbent in the ^99m Tc / ⁹⁹ Mo generator without any pre-column (protective columns).

In this description, the terms “approximately”, “approximately”, and “about” with respect to a numerical value indicate that some deviation from a given numerical value is possible, by a maximum of ± 10% of the numerical value. It should be understood that unless otherwise indicated, the terms defining a case, a singular phenomenon include cases, plural phenomena.

A ⁹⁹ Mo / ^99m Tc generator based on the reaction of radiation capture of neutrons of molybdenum with low specific activity was created using the new MPCM composite as an adsorbent. It was found that the oxidized MPCM composite is capable of adsorbing> 95% of the available molybdenum from a 1% solution with pH 3.0, when the ratio of solid phase to liquid is 2: 100. Almost 90% of the available ^99m Tc was eluted from the generator with a solution containing mainly physiological saline (0.9% NaCl). The ⁹⁹ Mo slip and the pH of the eluent that passes through the alumina pre-column are within the normal range defined by the United States Pharmacopeia (USP) and the European Union Pharmacopeia (EUP).

The present invention is described with reference to certain specific variations and examples, but it should be understood that they are illustrative and do not limit the scope of the attached claims.

Claims (27)

1. Sorbent containing microporous material, including chitosan, crosslinked with glutaraldehyde in the presence of an acid catalyst, the concentration of glutaraldehyde being from about 2 to about 4 weight. %, where the specified sorbent is resistant to degradation under the influence of beta and gamma radiation and under the influence of acids, and moreover, this sorbent after crosslinking is oxidized, at least in part, with an oxidizing agent, which is chlorite, in a concentration of from 1 mm to 10 mm for increasing the selectivity of the indicated sorbent to Mo (VI) relative to Tc (VII). 2. The sorbent according to claim 1, having an increased selectivity of sorption of ⁹⁹ Mo relative to ^99m Tc. 3. The sorbent according to claim 1, the surface charge of which after loading Mo (VI) is approximately zero at pH 3-4. 4. Sorbent according to claim 1, the surface area of which ranges from 10 to 100 m ² / g. 5. The sorbent according to claim 4, the surface area of which is approximately 25 m ² / g. 6. The sorbent according to claim 1, the point of zero charge of which ranges from about 7.5 to about 8.8. 7. The sorbent according to claim 1, the capacity of which for molybdenum is from 5.4 to 6.25 mmol of molybdenum per gram of sorbent. 8. A method of producing a sorbent resistant to radiation, including: mixing chitosan with water in the presence of acid to form a chitosan gel; adding glutaraldehyde to the gel with the formation of a semi-solid mass in the presence of a catalyst at a temperature of 70 ° C, at which a condensation polymerization (polycondensation) reaction of the reaction mass occurs; washing a semi-solid mass to remove unreacted glutaraldehyde and forming a washed mass; suspending the washed mass in an aqueous base to form a neutralized crosslinked mass; drying the neutralized crosslinked mass with the formation of a sorbent resistant to radiation; and oxidation of a sorbent resistant to radiation by an oxidizing agent, which is chlorite, wherein said oxidizing agent is added to the solution at a concentration of from 1 mM to 10 mM to increase the selectivity of said sorbent to Mo (VI) relative to Tc (VII). 9. The method of claim 8, wherein said oxidation comprises: the addition of an oxidizing agent to a radiation-resistant sorbent at a pH in the range of from about 3 to about 11. 10. The method of claim 8, wherein said oxidation comprises contacting the oxidizing agent with a radiation-resistant sorbent for a duration of exposure of from about 30 minutes to about 24 hours. 11. The method according to p. 8, in which the concentration of the oxidizing agent ranges from about 1 mm / L to about 10 mm / L, or in which the ratio of solid to liquid substances is from about 1: 100 to about 2: 100, or which satisfies both of these conditions. 12. The method of separation of isotopes from their mixtures, including: contacting a mixture containing at least a ⁹⁹ Mo isotope and a ^99m Tc isotope with a radiation resistant sorbent according to claim 1, which preferably adsorbs ⁹⁹ Mo; sorption of ⁹⁹ Mo from said isotopes on or in said sorbent, while ^99m Tc or other isotopes are sorbed to a small extent by a sorbent; removal of ⁹⁹ Mo or other isotopes from the specified sorbent. 13. The method according to p. 12, in which the mixture of isotopes is an isotope present in the stream of radioactive waste. 14. The method according to p. 12, in which the removal of ⁹⁹ Mo or other isotopes from the sorbent comprises contacting the sorbent with a solution of eluent. 15. The method according to p. 14, in which the eluent solution contains one or more oxidizing agents selected from the group consisting of chlorite, hypochlorite, dichromate and cerium oxide. 16. A generator for ⁹⁹ Mo / ^99m Tc, containing the sorbent according to claim 1. 17. The method of separation or concentration, or both, of one or more heavy metals from a liquid stream, where the heavy metal is selected from Mo or Tc, comprising contacting the liquid stream containing the specified one or more heavy metals with a sorbent according to claim 1 and sorption on it of one or more of these heavy metals.

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