EP3221265A1 - Préparation de matière composite microporeuse à base de chitosane et ses applications - Google Patents

Préparation de matière composite microporeuse à base de chitosane et ses applications

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Publication number
EP3221265A1
EP3221265A1 EP15861884.3A EP15861884A EP3221265A1 EP 3221265 A1 EP3221265 A1 EP 3221265A1 EP 15861884 A EP15861884 A EP 15861884A EP 3221265 A1 EP3221265 A1 EP 3221265A1
Authority
EP
European Patent Office
Prior art keywords
mpcm
sorbent
chitosan
solution
molybdenum
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP15861884.3A
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German (de)
English (en)
Other versions
EP3221265A4 (fr
Inventor
Shameem Hasan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Perma Fix Environmental Services Inc
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Perma Fix Environmental Services Inc
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Filing date
Publication date
Priority claimed from US14/547,201 external-priority patent/US20150139870A1/en
Application filed by Perma Fix Environmental Services Inc filed Critical Perma Fix Environmental Services Inc
Publication of EP3221265A1 publication Critical patent/EP3221265A1/fr
Publication of EP3221265A4 publication Critical patent/EP3221265A4/fr
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G39/00—Compounds of molybdenum
    • C01G39/003—Preparation involving a liquid-liquid extraction, an adsorption or an ion-exchange
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
    • B01D15/08—Selective adsorption, e.g. chromatography
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D59/00—Separation of different isotopes of the same chemical element
    • B01D59/22—Separation by extracting
    • B01D59/26—Separation by extracting by sorption, i.e. absorption, adsorption, persorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/04—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of alkali metals, alkaline earth metals or magnesium
    • B01J20/041—Oxides or hydroxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/04—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of alkali metals, alkaline earth metals or magnesium
    • B01J20/046—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of alkali metals, alkaline earth metals or magnesium containing halogens, e.g. halides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/24—Naturally occurring macromolecular compounds, e.g. humic acids or their derivatives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/26—Synthetic macromolecular compounds
    • B01J20/265—Synthetic macromolecular compounds modified or post-treated polymers
    • B01J20/267—Cross-linked polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J20/28057—Surface area, e.g. B.E.T specific surface area
    • B01J20/28059—Surface area, e.g. B.E.T specific surface area being less than 100 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/3071—Washing or leaching
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/3078—Thermal treatment, e.g. calcining or pyrolizing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/3085—Chemical treatments not covered by groups B01J20/3007 - B01J20/3078
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/34—Regenerating or reactivating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/34—Regenerating or reactivating
    • B01J20/3425—Regenerating or reactivating of sorbents or filter aids comprising organic materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/34—Regenerating or reactivating
    • B01J20/345—Regenerating or reactivating using a particular desorbing compound or mixture
    • B01J20/3475—Regenerating or reactivating using a particular desorbing compound or mixture in the liquid phase
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G39/00—Compounds of molybdenum
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G99/00—Subject matter not provided for in other groups of this subclass
    • C01G99/003—Preparation involving a liquid-liquid extraction, an adsorption or an ion-exchange
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
    • G21F9/04—Treating liquids
    • G21F9/06—Processing
    • G21F9/12—Processing by absorption; by adsorption; by ion-exchange
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/48—Sorbents characterised by the starting material used for their preparation
    • B01J2220/4812—Sorbents characterised by the starting material used for their preparation the starting material being of organic character
    • B01J2220/485—Plants or land vegetals, e.g. cereals, wheat, corn, rice, sphagnum, peat moss

Definitions

  • Radioactive isotopes are widely used, particularly in the field of nuclear medicine ⁇ both for therapy and imaging.
  • these materials can present production, storage, and disposal challenges due to their radioactivity, as well as their often significant half-lives.
  • 99m Tc (having a half-life t 1/2 ⁇ 6h), is one of the most widely used radioisotopes in diagnostic medicine, obtained from the decay product of parent 99 Mo ( t 1/2 ⁇ 66 h).
  • 99m Tc is a pure gamma emitter (0.143 MeV) ideal for use in medical applications due to its short half-life (6 hours). It Is used in 80-85% of the approximately 25 million diagnostic nuclear medicine procedures performed each year.
  • the parent 99 Mo can be produced by ihe irradiation of 98 Mo with
  • HEU highly enriched uranium
  • a sorbent that is readily available, or producible from readily available materials, and that is customizable by modification to have one or more functional groups (which may be the same or different) allowing the material to remove constituents from a process stream requiring such purification, and that is resistant to degradation by ionizing radiation.
  • the ion exchange process which has been used for decades to separate metal tons from aqueous solution, is often compared to adsorption. The primary difference between these two processes is that ion exchange is a stoichiometric process involving electrostatic forces within a solid matrix, whereas in adsorptive separation, uptake of the solute onto the solid surface involves both electrostatic and Van dcr Waals forces.
  • Chitosan is a non-toxic, biodegradable material, It has been investigated for many new applications because of its availability, polycationic character, membrane effect, etc.
  • the amino group present in the chitosan structure is the active metal binding site, but it also renders chitosan soluble in weak acid. In acidic media, chitosan tends to form a gel which is not suitable for adsorption of metal ions in a continuous process.
  • Li and Bai (2005) proposed a method to cap the amine group of chitosan by formaldehyde treatment before cross-linking with gluteraldchyde, which was then removed from the chitosan structure by washing thoroughly with 0.5M HC1 solution.
  • Li, Nan, and Bai, R. A novel amine-shielded surface cross-linking of chitosan hydrogel beads for enhanced metal adsorption performance" Ind. Eng. Chcm. Res., 44, 6692-6700, 2005, Crosslinking of chitosun with different functional groups is thought to depend mainly on the crosslinking reaction conditions, such as pH, temperature, ionic concentration, and the surface charge of the materials.
  • the surface charge of the chitosan that determines the type of bond that will form between the cross-linking agent and chitosan depends on the pH of the solution. Hasan, S., Krishnaiah, A., Ghosh, T.K., Viswanath, D.S., Boddu, V.M., and Smith, E. D. "Adsorption of divalent cadmium from aqueous solutions onto chitosan-coated perlite beads, lnd. Eng. Chem. Res., 45, 5066-5077, 2006, The point of zero charge (P2C) value of pure chitosan is in the pH range of 6.2-6.8.
  • Chitosan is not soluble in alkaline pH, but at acidic pH, the amine groups present in the chitosan can undergo protonation to NH3 * or ( ⁇ 2- ⁇ 3 O) + .
  • SUMMARY One embodiment disclosed herein relates to a radiation-resistant sorbent comprising glutaraldchyde-crossl inked chitosan.
  • chitosan-bascd microporous composite micron-size particles and chitosan-titania microporous composite materia! which was prepared by cross-linking chitosan with glutcraldchydc in the presence of a catalyst.
  • a sorbent containing a microporous material of chitosan that has been crossiinked with glutaraidchyde in the presence of a catalyst, such as an acid (e.g., HCi) to a glutaraidchyde concentration of about 2 to 4 wt%guard and which is resistant to degradation from exposure to beta and gamma radiation, and to degradation from exposure to acids or alkaline solutions.
  • a catalyst such as an acid (e.g., HCi) to a glutaraidchyde concentration of about 2 to 4 wt%guard and which is resistant to degradation from exposure to beta and gamma radiation, and to degradation from exposure to acids or alkaline solutions.
  • the cross-linked microporous chitosan matrix enhances the acid resistance and mechanical strength of the chitosan particle.
  • the uptake capacity of the cross-linked particles increases for metal tons from acidic or alkaline radioactive solution in comparison to available commercial resins and commercial aluminas. This increased uptake can result in efficiencies for molybdenum as high as 500-700 mg/g of sorbent, more particularly, about 600 mg/g of sorbent.
  • Described herein arc embodiments of chitosan-bascd microporous composite materials which were prepared using solution casting and combination of solution casting and sol-gel method.
  • chitosan was cross-linked with giuterakiehyde in the presence of acid as a catalyst at temperatures of around 70°C under continuous stirring.
  • acid as a catalyst
  • amino groups present in the chitosan structure are protonated, and thus shielded from the reaction with glutcraldchydc it is also believed that at temperatures of around ?0°C, more aldehyde groups arc available for reaction than are available at room temperature.
  • glutaraldehydc undergoes aldol condensation and the free aldehyde group will react with -OH groups of chitosan in the presence of an acid catalyst, so that the polymerization of chitosan with glutaraldehydc is a condensation polymerization.
  • Reaction times generally range from about 4 hours to about 8 hours.
  • the mole ratio of chitosan hydroxyl group to glutcratdchydc is desirably maintained at around 4/1.
  • the crosslinkcd material can be further processed by, washing to remove excess glutaraldchyde, drying, wet or dry milling, and additional chemical processing.
  • additional chemical processing that has been found to be particularly suitable is at least partial oxidation with an oxidizer.
  • oxidation with one of more of a permanganate e.g., by a potassium permanganate solution containing at least about 14 mg Mn/L of solution
  • a peroxide, a chlorite, a hypochlorite, u dichromate, or a metal oxide, or other ambiphilic oxidizer is especially suitable for increasing the selectivity of the sorbent for Mo(VT) with respect to Tc(VII), and for the efficient and rapid clution and recovery of technetium from loaded sorbent.
  • an oxidizer comprising one or more of an alkali metal chlorite, an alkali metal hypochlorite, an alkali metal dichromate, or a transition metal oxide is desirably used.
  • an oxidizer comprising one or more of sodium chlorite, sodium hypochlorite, potassium dichromatc, or cerium oxide is desirably used.
  • these oxidizers can desirably be included in an eluent solution used to release technetium from the sorbent.
  • such oxidizers are included in a saline-containing eluent solution in concentrations ranging from about 5 to about 40 mM for chlorites or hypochlorites.
  • the sorbent has a surface area that ranges between about 10 and about 100 m 2 /g, and more particularly is about 25 m 2 /g.
  • the sorbent has a point of zero charge ranges from about 7.5 to about 8.8, and more particularly is about 8.8.
  • Embodiments of the sorbents described herein have an excellent holding capacity for molybdenum, and can sorb molybdenum in amounts of around 60 wt%, based on the dry weight of the sorbent, or higher. This holding capacity can be around 6.25 mmol/g of sorbent, or higher.
  • the sorbents also have excellent selectivity for molybdenum with respect to technetium, and are able to hold molybdenum while passing pertechnate ion in saline solution with an efficiency of at least about 80%.
  • Embodiments of the sorbents disclosed herein also provide excellent capacity to sorb heavy metals, including, e.g., the ability to sorb Hg in amounts of 2.96 mmol/g dry sorbent or higher from aqueous solution at pH 6.
  • titunium oxide was incorporated into the chitosan gluteraldehyde composite polymer matrix.
  • CST crystalline silica titanate
  • titanium-based oxide materials have paved the way for metal ions adsorption studies onto hydrous titanium oxide from the radioactive and nonradioactive waste streams.
  • one embodiment relates to a method for preparing a radiation-resistant sorbent, comprising:
  • Another embodiment relates to such a method further comprising: forming an amorphous titania gel by acid catalyzed hydrolysis and condensation of titanium isopropoxide;
  • the chitosan-bascd microporous composite materia! was then suspended in a solution with pH 3 and irradiated at 50,000 krad using
  • Another embodiment relates to a method of separating isotopes from mixtures thereof, comprising:
  • Chitosan cross-linked composite is an excellent low cost alternative adsorption material compare to available resins, and thus a desirable adsorbent material to remove metal ions from radioactive and nonradioactive aqueous solutions. It has been found that the success of adsorption processes in the 99 Mo/ 99m TC generator systems depends largely on the cost and capacity of the adsorbents and the ease of 99m Tc release from the generator. The main problem with this particular method from a radiation safety standpoint involves the "breakthrough", or partial elution of the 99 Mo parent along with the 99m Tc from the generator, which must be kept within Nuclear Regulatory Commission (NRC) standards. Embodiments of the materials and methods described herein provide good, selective release of 99m Tc from the generator, thereby solving this problem and fulfilling a need for such a generator.
  • NRC Nuclear Regulatory Commission
  • embodiments of the chitosan crosslinked composites disclosed herein can be used in a method for separating or concentrating or both one or more heavy metals from a liquid stream, such as a waste stream or a process stream, by contacting a liquid stream containing one or more heavy metals with the chitosan crosslinked composite and sorbing one or more of said heavy melals thereon.
  • FIG. 1 is a scanning electron microscope photomicrograph that shows chitosan and embodiments of modified chitosan (MPCM) disclosed herein.
  • FIG la shows unmodified chitosan;
  • FIG. lb shows the an embodiment of MPCM material.
  • FIG. 2 is a graph showing the results of a thermogravimetric analysis (TGA) of chitosan and an embodiment of MPCM.
  • TGA thermogravimetric analysis
  • FIG. 3 is a graph showing an X-ray diffraction pattern of chitosan and an embodiment of MPCM material.
  • FIG. 4 is a graph showing Fourier Transform Infrared (FTIR) spectra of chitosan and an embodiment of MPCM material disclosed herein.
  • FTIR Fourier Transform Infrared
  • FIG. 5 is a graph showing X-ray photoelectron spectroscopy (XPS) survey scans for chitosan and an embodiment of MPCM.
  • FIG. 6 is a graph showing X-ray photoelectron spectroscopy (XPS) spectra for chitosan and an embodiment of MPCM.
  • FIG. 6a, 6b, and 6c show the C Is, O Is, and N Is positions, respectively.
  • FIG. 7 is a graph of energy-dispersive X-ray spectrometry (EDS)
  • FIG 7a shows spectra of chitosan and an embodiment of MPCM before and after irradiation.
  • FIG 7b shows comparison of chitosan and an embodiment of MPCM.
  • FIG 7c shows comparison of an embodiment of MPCM before and after irradiation.
  • FIG. 8 is a schematic diagram showing a reaction pathway for the preparation of an embodiment of MPCM described herein.
  • FIG. 9 is a graph showing FT1R spectra of an embodiment of modified chitosan disclosed herein before and after irradiation.
  • FIG. 10 is a graph showing X-ray photoelectron spectroscopy (XPS) spectra for un embodiment of MPCM before an after radiation.
  • FIG. 10a, I Ob, and 10c show the C Is, O Is, and N Is positions, respectively.
  • FIG. 11 is a graph showing surface charge of an embodiment of MPCM with and without exposure to 1 % of Mo (VI) in solution in the presence of 1 M NaNO 3 .
  • FIG. 12 is a graph showing the effect of pH on moiybdate sorption on an embodiment of MPCM, with initial conditions of a concentration of 5.21 mmol/L and temperature 298 K.
  • FIG. 13 is a schematic diagram showing reaction mechanisms for sorption of Mo (VI) onto an embodiment of MPCM from aqueous solution.
  • FIG. 14 is a graph showing equilibrium sorption isotherms for Mo (VI) uptake on an embodiment of MPCM, showing experimental data (*) correlated with the Langmuir isotherm model (solid line) under conditions where the concentration of Mo(Vl) in solution is in the range of 1 mmol/L to 94 mmol/L, temperature 298 K, pH -3.
  • FIG. 15a is a graph showing a breakthrough curve for Mo (VI) sorption on a bed of MPCM, the inlet influent concentration was 5.21 mmoie Mo (V])/L at the pH of 3,;
  • FIG. 15b is a graph showing the effect of influent solution pH on the breakthrough curve for Mo (VI) from a column packed with an embodiment of MPCM, The inlet influent concentration was 5.21 mmolc Mo (VIVL with 153.8 mmolc NaCI/L at the pH of 4 to 7, respectively.
  • the bed height of the column was 3.2 cm.
  • the inlet influent flow rate was 1 mlJmin
  • FIG. 16 is a graph showing breakthrough curves for pertechnate from a column packed with an embodiment of MPCM without oxidation which was loaded with 6.25 mM of Mo (Vl)/gram of MPCM.
  • the volume of the column was 2.5 cm 3 .
  • the inlet flow rate was 1 mL/ min.
  • the inlet influent concentration was 0.25 mM pcrtechnetatc /L in saline (0.9% NaCl) solution.
  • FIG. 17 is a graph showing the surface charge of oxidized and non-oxidized MPCM exposed to 1% Mo (VI) in aqueous solution in the presence of IN NaNC ⁇ 3.
  • FIG. 18 is a graph showing an elution profile for 99m Tc from an embodiment of MPCM loaded with Mo (VI) spiked with 99 Mo.
  • FIG. 19 is a graph showing the relationship between number of clution(s) and the percentages of 99m Tc and Mo (VI) release from an embodiment of MPCM as sorbent.
  • FIG. 20 is a flow diagram for a process using a 99m Tc/ 99 Mo generator systems and a 99 Mo production using neutrons capture method, using an embodiment of MPCM as the sorbent.
  • FJG. 21 is a graph showing the effect of temperature on molybdenum uptake onto MPCM-CIO 2 resin under conditions of initial solution concentration of 1% Mo solution with 25 mM NaOCl, pH of 3.0, and solid to liquid ratio of 1 : 100 with a contact time of 0.5 hour.
  • FIG. 22 is a graph showing heat of adsorption at different loading and temperature (24°C to 50°C) of the resin of FIG. 21.
  • FIG. 23 is a graph showing the projected specific activity of a proposed MPCM based generator with a column volume of 6- mL
  • FIG. 24 is a graph showing FTTR spectra of chitosan and another embodiment of modified chitosan disclosed herein.
  • the modified chitosan disclosed herein can be prepared according to the reactions shown schematically in FIG. 7, by crosslinking with glutaraldehyde under acidic conditions at temperature conditions set forth below. While the amount of glutaraldehyde used may vary somewhat, it has been found effective to use from about 2 ml to about 10 ml, more particularly from about 2 ml to about 8 ml, even more particularly, about 6 ml, of glutaraldehyde per 4 g of chitosan.
  • the pH of the crosslinking reaction between glutaraldchyde and chitosan may also vary somewhat, but it has been found effective to use a pH of between about 0.7 and about 3, more particularly between about 0.7 and 2, even more particularly, of about 1.0.
  • the temperature of the crosslinking reaction may also vary, but is desirably between about 50 "C and about 80 °C, more particularly, around 70 "C.
  • the ionic capacity of the chitosan used in this study was in the range of 9 to 19 milHequivalents/g, measured using a standard tttramcrric method.
  • About 4 g of chitosan was added to 300 mL Dl water with 1 mL acetic acid and stirred for 2 hr at 70°C to form a gel.
  • Approximately 5 mL of HCl/HNOj was added into the chitosan gel and kept under continuous stirring for another 1 hr at 70°C to assist protonation of the amino subsutuent groups, which is beneficial for the reasons given below.
  • the reaction with gluteraldehydc was performed by drop-wise addition of approximately 6 mL gluteraldehydc solution, having a concentration of 50%, to the acidic chitosan gel under continuous stirring (established based on trial and error, but generally from 200 rpm to 500 rpm) at 70°C.
  • the final pH of the the mixture was approximately 1.0.
  • the amount of gluteraldehydc was used in this study was established based on trial and error basis.
  • the mixture was kept under continuous vigorous stirring (500 rpm) at 70°C for another 1 hr to obtain semi-solid gel.
  • the amino groups present in the chitosan are much more reactive with aldehyde through Schiff's reaction than the hydroxyl groups of chitosan.
  • the resulting mass was then thoroughly washed with 2% monoethano! amine to remove any unreacted gluteraldehyde.
  • the mass was then suspended in 0.1M NaOH solution for 4 to 6 hours.
  • the cross-linked mass was separated from the solution and washed with 0.1M HC1 and then with deionized water (DI) until the pH of the effluent solution was 7.
  • DI deionized water
  • the cross-linked mass was then dried in a vacuum oven overnight at 70°C.
  • the cross-linked chitosan-gluteraldchydc composite is referred to as "MPCM" or "microporous composite material" herein.
  • the MPCM was ground using a laboratory jar mill to a particle size in the range of about 50 to 200 ⁇ . An amount of these MPCM particles was suspended overnight in aqueous solution having pH 3. The pH of the solution was maintained using 0.1M HNO 3 . The suspended MPCM particles were irradiated using 60 Co as a ⁇ source. The characterizations of the MPCM sample were performed using SEM, EDS X-ray microanalysis, FTIR, and XPS spectroscopic analysis.
  • FIG. 1 A scanning electron micrograph (SEM) of chitosan and MPCM material was taken to study the surface morphology and is shown in FIG. 1.
  • the SEM secondary electron micrograph of the samples were obtained using backscatter electrons with an accelerating potential of 10 keV.
  • the SEM micrograph of the cross-section of chitosan and MPCM sample is shown in FIG. la and lb, respectively. It appears from FIG. la that chitosan is nonporous, and from FIG. lb the MPCM appears to be microporous in nature.
  • Thermogravimetric analysis (TGA) of the chitosan at a heating rate of 5 °C /min in nitrogen atmosphere (200 mL/min) indicates that complete dehydration occurs at 250°C with a weight loss of 8%.
  • the anhydrous chitosan further decomposed in the second step with a weight loss of 32% at 360°C. It was burned out completely at 600°C with a further 12% loss of weight. The remaining 48% is the burnt residue of the chitosan at 600°C.
  • the swelling behavior and acid tolerance of the MPCM material were also evaluated.
  • the swelling behavior of MPCM was performed by immersing it in deionized water and saline solution using a process 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). Swelling behaviour of chitosan was also studied with deionized water and saline solution.
  • the swelling ratio of the chitosan and MPCM was calculated using the following equation:
  • V is the volume of swollen MPCM and V d is the volume of dry sample.
  • V d is the volume of dry sample.
  • MPCM shows very fast swelling behavior reaching approximately 200% increase within five minutes and reaching equilibrium at 24 hours.
  • the swelling studies with deionized water were performed within the pH range of 3 to 6. At equilibrium, the maximum volume of the MPCM was almost 219% more than its dry volume.
  • the MPCM sample was submerged in different concentrations of HCl, HNO 3 , and H 2 SO 4 acid for 24 hours. Chitosan tends to form a gel in acidic media making it unsuitable for its use in an adsorption column for separation of metal tons from aqueous solutions.
  • One of the main objectives of this study was to make a chitosan- based acid resistant material while exposing more - ⁇ H 2 groups, which is the active metal binding site for chitosan.
  • Table 1 shows the results for ihe acid tolerance capacity of MPCM. It was observed that MPCM material show.s better HCl tolerance capacity than it docs tolerance for HNO3 and H 2 SO 4 .
  • MPCM The physical size and shape of MPCM did not show any significant change up to 12M HCl, 12M H 2 SO 4 and 3.9 M HNOj solution but the MPCM appeared to be dissolved completely in 7.8 M HNO 3 solution. It is evident that the MPCM is more acid resistant compared to chitosan.
  • Figure 3 shows the XRD pattern for pure chitosan and MPCM beads.
  • the chitosan sample showed a diffraction peak near 20°, indicative of the relatively regular crystal lattices (110, 040) of chitosan.
  • Sec Wan et al. "Biodegradable Polylactide/Chitosan Blend Membranes,” Biomacromolecules 7(4): 1362-1372 (2006).
  • the peak observed for MPCM is appeared to be broadened suggesting that the MPCM sample is amorphous in nature. It also indicates that chitosan and glutaraldchyde formed a complex in the presence of acid; therefore the crystalline structure of the chitosan was disrupted by the chemical bonding between chitosan and glutaraldchyde.
  • FTIR Fourier Transformed infrared spectra
  • chitosan and MPCM exhibited peaks at 3498 cm -1 and 2950 cm"', respectively, corresponding to the stretching O-H and N-H groups and C-H stretching vibration in CH, and -CH2,.
  • the peaks at 1350 to 1450 cm - 1 indicate alkane C-H bending.
  • FIG. 4 shows a peak at 1600 cm -1 with a shoulder like peak centered at around 1570 cm 4 and 1670 cm 4 represent -NH 2 and amide I, respectively for chitosan.
  • the presence of a comparatively sharper peak at 1590 cm -1 in MPCM than the peak observed for chitosan suggests the presence of NH3 + band in the MPCM sample.
  • the XPS analysis of chitosan and the MPCM sample prepared above was performed to gain a better understanding of intcrmolecular interaction between chitosan and glutcraldchydc.
  • a survey scan was used to ensure that the energy range was suitable to detect all the elements.
  • the XPS data were obtained using a KRATOS model AXIS 165 XPS spectrometer with monochromatic Mg X-rays (hv ⁇ 1253.6 cV), which were used as the excitation source at a power of 240W.
  • the spectrometer was equipped with an eight-channel hemispherical detector, and the pass energy of 5-160 cV was used during the analysis of the samples.
  • FIG. 5 shows the peak positions of C Is, O Is, and N Is obtained by the survey scan of chitosan and the MPCM sample prepared above, respectively.
  • FTG. 6 shows the peak positions in detail for C Is, O Is, and N Is present in chitosan and MPCM.
  • the C-ls peak observed showed two peaks on deconvolution, one for C-N at 284.3 eV and the other one for C-C at 283-5 eV (FIG. 6a).
  • the C-Cs peak appears to be folded and shifted slightly, whereas the C-N peak showed higher intensity compared to chitosan (FIG. 6a).
  • the peaks for oxygen containing groups (O Is) were found at 530,5 eV and 531.1 cV for chitosan and MPCM, respectively ( Figure 6b).
  • the N Is peak for chitosan was at 397.5 eV (FWHM 1.87) for nitrogen in the - NH 2 group of chitosan (FIG. 5c); for the MPCM the N Is peak appeared at 397.7 eV.
  • One of the objectives for investigating the N Is peak was to identify whether amine groups, which arc active metal binding sites for chitosan, were involved in cross- linking reactions with glutaraldchyde.
  • FIG. 6c shows a strong Nls peak for MPCM at 397.7 eV, which can be assigned to -NH 2 groups, suggesting that the amine groups of chitosan were not affected by the cross-linking reaction with glutaraldchyde. This is also evident from the FTIR spectra (FIG, 4).
  • Table 2 shows the XPS data for surface elemental analysis of the sample of MPCM, as determined from the peak area, after correcting for the experimentally determined sensitivity factor ( ⁇ 5%). It has been found that by preparing porous chitosan based material, in this case the embodiment of MPCM described above, results in the exposure of more NH 2 groups on the surface of the material. The nitrogen concentration, as determined from the N Is peak on the sample of MPCM, was almost twice that calculated for chitosan (Table 2). It is believed that the nitrogen content in the MPCM came entirely from chitosan.
  • the high nitrogen content in the MPCM was due to the microporous nature of the MPCM which makes more amine groups available on the surface than is the case in the nonporous chitosan. This is also consistent with the results reported by Hasan ct al leverage supra, obtained by dispersing chitosan onto pcrlitc.
  • the changes in peak intensity of C Is and binding energy of O Is peaks at 531 ,0 eV of the MPCM sample compared to chitosan arc believed to be due to the reaction with glutaraldchyde in presence of acid as a catalyst.
  • Table 2 Absolute Binding Energy (BE) for the elements present in the chitosan and MPCM obtained from X-ray Photoelectron Spectroscopy (XPS) Analysis.
  • the energy dispersive spectroscopy (EDS) X-ray microanalysis was performed on the same MPCM sample as was used for the SEM micrograph.
  • the EDS microanalysis was used for elemental analysis of MPCM (FIG. 7).
  • the peaks for carbon, oxygen, and nitrogen are shown at 0.3 keV, 0.36, and 0.5 keV, respectively, which are the main components of chitosan (FIG. 7a, 7b). Due to the reaction with glutaraldchyde, the intensity of the carbon peak for MPCM increases; whereas, the intensity of the oxygen peak decreases in comparison to chitosan (FIG. 7b).
  • FIG. 7 Due to the reaction with glutaraldchyde, the intensity of the carbon peak for MPCM increases; whereas, the intensity of the oxygen peak decreases in comparison to chitosan (FIG. 7b).
  • the MPCM sample described above was evaluated for radiation stability by irradiation with a 60 Co source.
  • the 1R spectra of the MPCM composite sample before and after being irradiated using a 60 Co source arc shown in FIG. 9.
  • the results in FIG. 9 shows that the MPCM sample suspended in water at pH 3.0 can tolerate v-radiation to about 50,000 krad without losing a substantial percentages of its identity.
  • FIG. 7c shows EDS spectra of chitosan and MPCM particles before and after irradiation at 50,000 krad with a 60 Co source.
  • FIG. 7c indicates that the intensity of carbon, oxygen, and nitrogen peaks did not change substantially after irradiation of the sample.
  • FIG. 10 shows the peak positions of carbon, oxygen, and nitrogen obtained by the XPS analysis of the MPCM sample before and after irradiation. It was observed that the magnitude of total C Is peak binding energy changed after irradiation as shown in Table 2.
  • the C Is peak for the MPCM sample was 283.5 eV, while for the MPCM sample after irradiation; two peaks were observed at 283.5 and 284.5 cV (FIG. 10a).
  • the Nls peak present in the MPCM sample after irradiation around 397.5 eV can be assigned to NH 2 groups in the MPCM structure. No change was observed for O-1s peak of the irradiated MPCM sample. The magnitude of the binding energy shift depends on the concentration of different atoms, in particular on the surface of a material . In comparison with the XPS (FIG. 10a-c), the N Is and O 1s peak of the MPCM sample did not shift before and after irradiation (Table 2), indicating that the chemical state of N atoms was not much affected after irradiation. This is also reflected in the EDS and FTIR spectra as shown in FIG. 7 and 9.
  • the MPCM sample described above was evaluated for molybdenum sorption using batch techniques.
  • About 1,0 gram of MPCM adsorbent was suspended in lOOmL solution containing ammonium molybdate in the range of I mmole/L to 94 mmole/L.
  • the initial pH values of solutions were adjusted from 2.0 to 8.0 using cither 0.01 M NaOH or 0.1 M HCl solution.
  • the solutions were then kept in a shaker (160 rpm) for 24 hrs at 298K, After 24 hrs, the final pH was recorded for each solution and the solutions were centrifuged for 5 minutes at 3000 rpm to separate the supernatant from the solution.
  • the supernatant was then filtered through a 0.45- ⁇ membrane filter and the filtrate was analyzed for molybdenum removal by an Inductively Coupled Plasma (ICP) (Agilent 7700X) that is equipped with mass spectroscopy for molybdenum detection.
  • ICP Inductively Coupled Plasma
  • the adsorption isotherm was obtained by varying the initial concentration of molybdenum in the solution, The amount of molybdenum adsorbed per unit mass of adsorbent (q e ) was calculated using the equation,
  • V is the volume of the solution in liters (L)
  • M is the mass of the adsorbent in gram (g).
  • the surface charge of a bead of MPCM sample was determined by a standard potentiometric titration method in the presence of a symmetric electrolyte, sodium nitrate, as per Hasan et al., supra.
  • the magnitude and sign of the surface charge was measured with respect to the point of zero charge (PZC).
  • PZC point of zero charge
  • the pH at which the net surface charge of the solid is zero at all electrolyte concentrations is termed as the point of zero charge.
  • the pH of the PZC for a given surface depends on the relative basic and acidic properties of the solid and allows an estimation of the net uptake of H + and OH ' ions from the solution. The results arc shown in FIG. 11.
  • the PZC value of the sample of MPCM prepared as described above was found to be 8.8, which was similar to that reported by Hasan ct al., supra, for chitosan coated perlite bead. However, it is reported that the PZC value of pure chitosan is within the pH range of 6.2 to 6.8. See Hasan ct alirri supra. It is observed from FIG. 11 that a positively charged surface prevailed at a relatively low pH range. The surface charge of MPCM was almost zero in the pH range of 7.5 to 8.8. The protonation of the MPCM sharply increased at the pH range of 7.5 to 2.5 making the surface positive.
  • the PZC value of 8.8 and the behavior of the surface charge of the MPCM is due to the modification of chitosan when cross-linked with glutaraldchydc in the presence of acid as a catalyst, which makes it amphoteric in nature in the pH range of 7.5 to 8.8.
  • the effect of pH on adsorption of molybdenum by MPCM was studied by varying the pH of the solution between 2 and 8 (FIG. 12), The pH of molybdenum solutions were first adjusted between 2 and 8 using either 0.1N H 2 SO 4 or 0.1M NaOH, and then MPCM was added. As the adsorption progressed, the pH of the solution increased slowly. No attempt was made to maintain a constant pH of the solution during the course of the experiment. The amount of molybdenum uptake at the equilibrium solution concentration is shown for each different initial pH of the solution in FIG. 12.
  • the metal In order to adsorb a metal ion on an adsorbent from a solution the metal should form an ion in the solution.
  • the types of ions formed in the solution and the degree of ionization depends on the solution pH.
  • the main functional group responsible for metal ion adsorption is the amine (-NHj) group.
  • these amine groups can undergo protonation to NH3 + or (NH 2 -H 3 O) + , and the rate of protonation will depend on the solution pH. Therefore, the surface charge on the MPCM will determine the type of bond formed between the metal ion and the adsorbent surface.
  • molybdenum in an aqueous solution can be hydrolyzed with the formation of various species. At relatively high and low pH values both the M and various isopolyanions
  • the MPCM had a maximum adsorption capacity at a pH of around 3 from a solution of molybdenum ions.
  • the amine group of the MPCM has a lone pair of electrons from nitrogen, which primarily act as an active site for the formation of a complex with a metal ion.
  • the amine group of MPCM undergoes protonation, forming NH3 + leading to an increased electrostatic attraction between NH3 + and sorbate anion.
  • the anionic molybdenum (Mo (VI)) is presumably the major species being adsorbed by Coulombic interactions.
  • the pH of the solution was found to increase after adsorption, which cun be attributed to the H 1 ions released from the surfuce of the MPCM as the result of sorption of the molybdenum-containing anions from solution.
  • the protonation of NH 2 groups occurs at a rather low pH range. The fact that pH of the solution increased as the adsorption progressed suggests that Mo (VI) formed a covalent bond with a NH 2 group.
  • the equilibrium adsorption isotherm of molybdenum uptake on MPCM was determined at 298K temperature in the concentration range of 1 mmole/L to 94 mmoie/L. As mentioned in the previous section, the maximum adsorption capacity of molybdenum on MPCM occurs at a pH of 3. Therefore, the equilibrium isotherm experiments were carried out at a pH of 3, if not stated otherwise.
  • the concentration profiles during molybdenum uptake by the MPCM from various concentrations of the solution shows that approximately 60% of molybdenum was adsorbed during the first 4 hours of an experimental run. The equilibrium was attained monotonically at 24 hours in most of the experimental runs.
  • the MPCM material contains amino groups that are available for characteristic coordination bonding with metal ions. Adsorption of metal ion, when pH dependent, may be described by the following one-site Langmuir equation. The effect of pH was incorporated by introducing a parameter "a" that is dependent on pH of the solution. The expression is given below:
  • Equation 5 was used to correlate the adsorption capacity of the MPCM.
  • the equilibrium data for molybdenum could be correlated with the Langmuir equation within ⁇ 5% of experimental value.
  • the constants of Equation 5 arc obtained by non-linear regression of the experimental data and are given in Table 3. It was noted that Equation 5 represented the adsorption behavior of molybdenum on the MPCM adequately ( Figure 14).
  • the adsorption isotherm data obtained at pH 3 showed Type I behavior.
  • Table 3 shows the maximum adsorption capacity of MPCM for Mo (VI), using Langmuir Equation (Equation 5). It was noted that the adsorption capacity of MPCM for molybdenum is approximately -6.25 mmoi Mo/g of MPCM at 298K 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).
  • the ⁇ H 2 groups of MPCM arc the main active sites for molybdenum adsorption. As can be seen from the FIG. 13, two ⁇ H 2 groups will be necessary for the adsorption of one molybdenum ion.
  • a column was used to study the adsorption of Mo (VI) with or without the presence of ions in the solution under dynamic conditions.
  • Approximately 1.125 gram of MPCM was used to make a 2.5 cm 3 column with 0.5 cm inner diameter and 3.2 cm height
  • a flow rate of 1 mL/minute was used during a run. The run was continued for 1500 minutes, and samples at the bed out let were collected at a regular time intervals. The bed becomes saturated during this time period, as indicated by the outlet Mo (VI) concentration.
  • the inlet concentration was 5.21 mmole Mo (Vl)/L at pH 3 and the flow rate was 1 mL/ minute through the column, molybdenum broke through the column after 320 bed volumes (FIG. 15a). Complete saturation of the column occurred after 500 bed volumes.
  • Breakthrough curves were also obtained from a mixed solution containing 5.21 mmole Mo (VI) / L and 153.8 mM NaCl/ L at pH 6.86 and 4.0, respectively ( Figure 15 b).
  • the solution was passed through a similar size of column as mentioned earlier maintaining same bed height and flow rate. It was observed that column broke through quickly at 42 bed volume for the mixed solution with pH 6.86 however approximately 125 bed volumes were required to break through the column for the mixed solution with pH 4.0. It is important to note that the break through time for molybdenum solution with J 53.8 mM NaCl/ L can be delayed, through the use of larger quantity of MPCM adsorbent and a longer column. The objective was to investigate the effect of inlet mixed solution pH on the breakthrough characteristic of Mo (VI) from the column, therefore, no attempt were made to determine the bed length to prolong the breakthrough time for mixed solution.
  • the long lived technetium ( 99 Tc) was used to evaluate the performance of MPCM to adsorb technetium with and without the presence of other ions from an aqueous solution in the pH range of 3 to 11.
  • Technetium is chemically inert and has multiple oxidation states ranging from I to VII.
  • the most dominant species of technetium that is found in aqueous waste streams is pertechnetate (TcO 4 -) Sec Gu et al., Development of Novel Bifunctional Amon-Exchangc Resin with Improved Selectivity for Pertechnetate sorption from contaminated groundwater, Environ. Sci. Technol., 34, 1075- 1080, 2000.
  • Table 4 shows that the adsorption of technetium onto MPCM is pH independent in the solution pH range of 3 to 11. It was observed that approximately 95% of 1 ⁇ technetium/L of solution was adsorbed onto MPCM in the pH range of 3 to 11, whereas the technetium removal was reduced to 56% in present of 0.9% NaCI over the pH range of 3 to 11. As it was mentioned earlier, MPCM shows positive charge in the pH range of 3 to 7.5, FTIR spectrum of MPCM confirms the presence of ⁇ NH2, CHOH, and CH 2 OH groups on MPCM surface (FIG. 4).
  • MPCM was also used to adsorb Mo (VI) and Tc(VIl) simultaneously from a mixed solution containing 1 mmole of Mo(Vl)/L and 0,1 1 ⁇ mole of pcrtcchneiete/L with or without the presence of 0.9% NaCl.
  • MPCM was found to adsorb molybdenum and technetium simultaneously from the solution at solution pH 3. It was observed that approximately 95% of 0. 11 ⁇ mole pertechnetate was adsorbed onto MPCM surface, whereas 99% of 1 mmole molybdenum was adsorbed from the mixed solution. In the presence of molybdenum in the solution, pertechnetate (TcO 4 -) had to compete for the positive surface sites of MPCM.
  • FJG. 16 shows that the pertechnetate anion has affinity towards available surface sites of MPCM in the presence of molybdenum anion. It was
  • the objective of this study was to investigate the maximum amount of pcrtechnctate (TcO 4 -) uptake onto MPCM loaded with 6.25 mM of Mo (VI)/ gram of MPCM. No attempts were made to determine the bed length to reduce the pertechnetatc release from the Mo (VI) loaded MPCM bed.
  • Pertcchnetate is soluble in water, therefore, deionized water was used to regenerate technetium from the column. It was observed that only 1% of technetium was desorbed from the MPCM bed using 10 bed volumes of water. Preliminary studies show that complete recovery of technetium from the MPCM is challenging even using when different concentrations of NaCI solution. It was observed thai approximately 50 bed volumes of 1.5% NaCI was required to regenerate 10% of 99 Tc from the column. Similar amounts of low concentration acid solutions ( ⁇ 1M) of HCl, H 2 SO 4 , and HNO 3 , were also used, without any significant regeneration. In another attempt, the MPCM sorbent was oxidized with different concentrations of potassium permanganate or hydrogen peroxide, to study the effect of oxidation on absorption/desorption of technetium on to the oxidized MPCM sorbent.
  • MPCM was oxidized with different concentrations of hydrogen peroxide with or without the presence of transition metal catalysts. Temperature was also varied. The oxidation studies of MPCM with hydrogen peroxide were performed to determine whether controlled oxidation alone would improve technetium recovery from the technetium loaded MPCM. The concentration of hydrogen peroxide was varied from 1% to 5%. Batch technique was used to adsorb technetium onto oxidized MPCM. The regeneration of technetium from the oxidized MPCM was conducted in a column. The column was prepared with 0.12 ⁇ mole of 9 9 Tc / gram of oxidized MPCM. The column was regenerated to desorb technetium from the oxidized MPCM using 0.9% NaCl solution.
  • MPCM was also oxidized using potassium permanganate in solution.
  • concentration of potassium permanganate in the solution and the oxidation time was determined based on trial and error.
  • concentrations of potassium permanganate and the pH of the solution were varied from 0.1% to 5% and 3 to 11, respectively.
  • the oxidation time was varied from 30 minutes to 24 hours.
  • the surface charge analysis of oxidized and non-oxidi2cd MPCM loaded with Mo (VI) was also performed to elucidate the pertechnctate (TcO 4 -) adsorption pattern on oxidized MPCM.
  • permanganate solution containing 0.04 mmole of Mn /L of solution at the pH range of 3 to 4.5 and 12 hours time period was sufficient to oxidize MPCM partially to facilitate maximum uptake of molybdenum and simultaneous release of technetium from the MPCM sorbent.
  • the performance of the oxidized MPCM was evaluated for molybdenum adsorption from aqueous solutions using batch technique. It was noted that oxidized MPCM can adsorb 6.25 mmole of Mo (VI)/ g of MPCM at 298K. when the equilibrium concentration Mo (VI) in the solution was 54 mmol/L at pH 3.0.
  • MPCM shows great affinity for both Mo (VI) and Tc(VlI) from the aqueous solution.
  • the surface charge of Mo (VI) loaded MPCM revealed (FIG. 11) that Mo (VI) was adsorbed onto MPCM through an inner-sphere surface complcxation reaction. It may be noted that Mo (VI) loaded MPCM exhibited positive charge in the pH range of 3 to 4.5; therefore, anionic pertcchnetate presumably formed covalent bonds with the available positive surface sites.
  • the adsorption of pcrtechnctatc on to MPCM is approximately 55% from a solution containing 0,9% NaCl at the pH range 3 to 8 (Table 4).
  • the permanganate ion is ambiphilic in nature.
  • Mn (VII) ions of potassium permanganate change to possible intermediate products such as Mn (VI), Mn (V), Mn (IV), end Mn (111), which are ultimately reduced to Mn (II) ⁇
  • Mn (VII) ions of potassium permanganate
  • the permanganate (MnO 4 ) content in the potassium permanganate is reported to be the reactive oxidizing species for acid catalyzed permanganate oxidation of chitosan.
  • HMnO 4 species Due to protonation of the MnO 4 " ion in the acidic solution, the HMnO 4 species can be formed, which is also a powerful oxidant. See Sayycd ct al, "Kinetic and Mechanistic Study of Oxidation of Ester by KMnO 4 " International Journal of ChcmTcch Research, v 2, n 1 , p 242-249, 2010 The formation of colloidal MnO 2 is possible due to the reaction of MnO 4 " with and depending on the acidity of the solution which may further undergo reaction with H *+ to produce Mn 2 + in solution.
  • Ahmed ct al. 2002 reported permanganate oxidation of chitosan as an acid catalyzed reaction that led to formation of dikcto-acid derivatives of chitosan.
  • Sec Ahmed ct 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.
  • FIG. 17 shows the surface charge pattern for Mo (VI) loaded MPCM sample with or without oxidization. In the case of non-oxidized MPCM sample loaded with Mo (VI), the protonation of the surface appeared to be increased gradually at the pH range of 4.5 to 3.
  • the surface charge of Mo (VI) loaded oxidized MPCM shows almost zero charge in the pH range of 3 to 4.5, compared to the Mo (VI) loaded onto the non- oxidized MPCM sample (FIG. 17).
  • the surface functional groups of non-oxidized MPCM show positive charge which may further undergo reaction with MnO 4 during the oxidation reaction. It is assumed that the manganic (MnO 4 ) ion entered into the porous matrix of MPCM and partially oxidized the positive surface functional groups by donating electrons followed by reduction to Mn 2+ ion in the solution.
  • formation of colloidal manganese in the solution was controlled by controlling the solution pH in the range of 3 to 4.5, more specifically at pH 4.
  • the MPCM loaded with Mo (VI) and the supernatant and rinsed solutions were analyzed for molybdenum uptake using a dose calibrator, and a ICP-MS, It was observed that at equilibrium, the oxidized MPCM had a capacity of 2.47 mmolc Mo/g of MPCM where 1300 ⁇ Ci of activity arc from the spiked 99 Mo.
  • the activity for 99 Mo and 99m Tc was evaluated using both a dose calibrator and a gamma spectrometer.
  • the dose calibrator (Atomlab 400) is equipped with a small lead sample vessel that effectively shielded of 99m Tc gammas while allowing the majority of 99 Mo gammas to pass through the shield and into the detector. Therefore, readings taken while the sample is contained within the shielded vessel is assigned solely to Mo activity. Readings taken without the shield are the sum of both Mo and 99m Tc activities.
  • the MPCM loaded with both 99 Mo and 99 Mo was transferred to a column (0.5 cm" 3.2 cm with polytetrafluoroethylene (PTFE) frit at the bottom). Two ends of the column were closed with silicon rubber septum. The column was thoroughly rinsed with dc-ionizcd water to remove any molybdenum solution on the surface of the MPCM. The rinsed sample was collected from the column using evacuated vials. The column was eluted with saline (0.9% NaCl) solution after allowing it maximum time required to build-up the daughter product 99m Tc from the decay of the remaining 99 Mo in the column.
  • saline (0.9% NaCl
  • the column was eluted with 9 mL saline solution that was collected subsequently in 3 individual evacuated vials of 3 mL each.
  • the cluate was obtained from the column at predetermined time intervals.
  • the eluute from each collection was analyzed for molybdenum and manganese released from the column using quadruple inductively coupled plasma mass spectrometry (ICP-MS) with an external calibrator.
  • ICP-MS quadruple inductively coupled plasma mass spectrometry
  • the activity related to pertechnctale or 99 Mo was evaluated using dose calibrator and gamma spectroscopy.
  • FIG. 18 shows the elution profile of the column consisting of 0.5 gram of MPCM loaded with 2.47 mmole of Mo (VI) /gram of oxidized MPCM where 1300 ⁇ Ci activity is from adsorbed 99 Mo.
  • the column started eluting with saline (0.9% NaCl) solution on the day after the column was prepared and the elution was continued over the period of 8 days.
  • Elution 1 was performed at 8 hours after the column was prepared in order to verify the desorption behavior of 99m Tc from the MPCM column.
  • the rest of the elutions, number 2 to 8, were performed at 24 hours intervals except elution number 5 were performed at least 45 hours after the clution number 4.
  • the elution efficiency for the daughter product 99m Tc from the column was found to be within the range of 75 to 90% (FIG. 18).
  • elution I as shown in FIG. 18, more than 80% of the activity due to 99m Tc is obtained within 9 mL of saline (0.9% NaCi) in where 62% of the available 99m Tc activity clutcd in first 3 mL volume of normal saline.
  • the second clution was collected at 24 hours after the first clution and shows that the 99m Tc activity in the column ranged from 70% to 90% and can be recovered using 3 to 9 mL of saline solution.
  • the eiuate was clear, and the pH was in the range of 6 to 7.
  • the column was continuously clutcd over the period of 8 days with an average -82% of the whole 99m Tc eluted from the column.
  • FIG. 19 shows the percentage of 99m Tc and Mo (VI) released from the column over the period of 8 days.
  • the concentration of the Mo (VI) in the eluates was within the range of 1% to 3% of the 6.25 mmole Mo (VI)/ gram of MPCM in the column.
  • the process of capturing any molybdenum leakage from the column by passing it through acid catalyzed MPCM is possible as shown in FIG. 15 thus reducing the Mo (VI) and Mn(VII) concentrations in the elucnt to extremely low levels.
  • Another way of controlling molybdenum leakage from the column can be achieved by controlling the pH of the saline (0.9% NaCl) solution within the range of 4 to 4.5 (FIG. 15). In that case, an additional guard column will not be necessary to control the leakage of Mo (VI) from the column.
  • MPCM is capable of adsorbing more than 6.25 mmolc Mo (VI)/ gram (600 mg Mo (Vl)/g of MPCM) from an aqueous solution at pH 3, which is also applicable to 99 Mo obtained easily by the (n, ⁇ ) reaction of natural molybdenum.
  • the generator in this case consists of MPCM loaded 99 Mo thus combines the performances of the chromatographic generator and the use of (n, y) 99 Mo.
  • the MPCM is able to hold up to 60 wt% of its body weight, in comparison with only 0.2 wt% in the alumina.
  • MPCM resin was oxidized using sodium hypochlorite (NaC102) and sodium chlorite (NaOCl), respectively.
  • concentration of sodium chlorite or sodium hypochlorite in the solution and the oxidation time was determined based on trial and error.
  • concentrations of sodium chlorite and the pH of the solution were varied from 1 mmole/L to 10 mmole/L and 3 to 11, respectively.
  • the oxidation of MPCM by either sodium chlorite or sodium hypochlorite solution was carried out at a solid to liquid ratio of 1 : 100.
  • the oxidation time was varied from 30 minutes to 24 hours.
  • oxidized MPCM can adsorb approximately 6.25 mM (-600 mg) of Mo (VI) per g of oxidized MPCM at 298K. when the equilibrium concentration Mo (VI) in the solution was 54 mmol/L at pH 3.0.
  • a surface charge analysis of molybdenum loaded non-oxidized MPCM and molybdenum loaded MPCM-CIO 2 was carried out using procedures described above. Similar surface charge experiments were also performed with molybdenum loaded MPCM-OCl and the data was compared with the surface charge of molybdenum loaded non-oxidized MPCM resin.
  • the surface charge data of molybdenum loaded MPCM-CIO 2 and MPCM-OCl shows a similar pattern to that of molybdenum loaded MPCM that was oxidized by potassium permanganate.
  • Tc-99 uptake capacity two separate columns were prepared using molybdenum loaded MPCM-CIO 2 and MPCM-OCl, respectively.
  • Tc-99 pass through tests with both of these oxidized MCPM resins were performed following the procedures described above. The results confirmed that pertechnetate (TcO-f ) did not adsorb onto both MPCM ⁇ CIO 2 and MPCM-OCl loaded with Mo (VI).
  • Table 7 shows the comparison of the effects of different oxidizers on technetium release from a column prepared with oxidized MPCM. The oxidized MPCM resins, as shown in Table 7, were exposed to 1% molybdenum solution that was spiked with molybdenurn- 99.
  • molybdenum-99 was varied from 45 mCi to 1.39 Ci (at the end of irradiation, or EOI), respectively.
  • the molybdenum loaded MPCM resins that were oxidized by different oxidizers were used to prepare respective chromatographic columns. The columns were then flushed with saline solution and the data arc shown in Table 7.
  • Mo-99 in the column was approximately 45 mCi (Table 7).
  • the release of technetium from the column was comparatively very low for all oxidizing agents when Mo-99 with higher specific activity was used in the column.
  • technetium reduced from Tc(VU) to Tc(l V) and the reduced anionic pertechnetate presumably formed covalent bonds with the free surface sites of MPCM resin.
  • the release of technetium from the column was approximately 10% when molybdenum-99 with activity of 900mCi was loaded onto MPCM sample that was oxidized with 31 mM potassium permanganate (Table 7).
  • the MPCM-CIO 2 and MPCM-OCI resins were further studied to evaluate their potential for molybdenum adsorption in presence of different concentrations of oxidizing agent in the solution.
  • the adsorption study was carried out for 24 hours using different concentrations of sodium chlorite and sodium hypochlorite (5 mM to 50 mM) which were spiked with 1% molybdenum in solution (prepared from molybdenum salt, without radioactive molybdenum (Mo-99)).
  • the molybdenum solution pH was initially adjusted at - 3.0 for all the experiments. The samples were collected at different intervals and were analyzed for molybdenum uptake onto the resin.
  • Table 8 shows that, in the presence of sodium chlorite or sodium hypochlorite in the solution, the molybdenum uptake capacity of the oxidized MPCM resin was in the range of 5.21 mM (500 mg/g) to 6.25 mM (600 mg/g) of oxidized MPCM.
  • Molybdenum started precipitating out slowly in the solution after 12 hours of exposure when the oxidizer concentration in the solution was 45 mM or higher. No molybdenum precipitation in the solution was observed for the solution in which the concentrations of cither sodium chlorite or sodium hypochlorite were in the range of 5 mM to 40 mM. Molybdenum did not precipitate in the solution during first 4 hours of the exposure for any concentration of sodium hypochlorite that was used in this study.
  • Table 8 Adsorption cycle (I gram oxidized MPCM in 1% Molybdenum solution and exposure time 24h at pH— 3.0).
  • Molybdenum uptake was found to be fairly consistent onto MPCM-CIO 2 in presence of all concentrations of sodium hypochlorite in the 1% molybdenum solution (Tabic 8). Compared to the data obtained from oxidizer-free molybdenum solution, the uptake of molybdenum onto MPCM-CIO 2 was approximately 6.25 mM/g from a 1% molybdenum solution containing of 25 mM of sodium hypochlorite (NaOCl) in the solution (Table 8). This suggests that presence of hypochlorite in the molybdenum solution did not affect molybdenum adsorption substantially onto MPCM resin that was partially oxidized by sodium chlorite,
  • MPCM-CIO 2 was considered in this attempt to adsorb molybdenum in presence of different concentrations of sodium hypochlorite (NaOCl) as oxidizer in the 1% Mo solution.
  • the molybdenum loaded MPCM-CIO 2 was then used to prepare a chromatographic column.
  • Sodium chlorite and sodium hypochlorite were also mixed with saline solution in order to investigate their oxidizing effects on the release of both technetium and molybdenum from the column.
  • the columns were then flushed with a saline solution mixed with 5 mM concentration of sodium chlorite and sodium hypochlorite, respectively, at pH 4.
  • the eluate mixture was further spiked with Tc-99 (stoichiometrically equivalent to - ⁇ lCi of Tc-99m per 10 mL) before being passed through the column.
  • Tabic 10 Effect of sodium chlorite concentration in the eluent on the release of technetium and molybdenum from column prepared using molybdenum loaded MPCM-ClCh.
  • MPCM-CIO 2 resin as an adsorbent for the preparation of 9 9 Mo/ 99m Tc generator was evaluated by exposing it to 1% neutron-captured produced molybdenum solution with an activity of 13.9 mCi/mL irradiated at MURR (the University of Missouri Research Reactor, USA). A similar experiment was also carried out at POLATOM using 1% natural molybdenum solution that was spiked with fission molybdenum ( ⁇ 1.89 Ci 99 Mo/g Mo). Batch adsorption experiments for molybdenum uptake on MPCM-CIOi resin were carried out at room temperature while the solution pH for both experiments was initially about 3.0.
  • Molybdenum uptake onto the resin for both experiments was approximately 60% of the available molybdenum in the solution.
  • a 99 Mo/ 99m Tc generator consisting of a 6 mJL column containing MPCM-CIO 2 resin loaded with 99 Mo was prepared.
  • Wra Tc the decay product of 99 Mo
  • Table 11 shows the elution performance of a typical generator that was prepared by exposing 1-g MPCM-CIO 2 resin to 100 mL of 1.39Ci 99 Mo in ⁇ 1% total molybdenum solution at an initial pH of -2,8.
  • the eluent solution was further subjected to treatment with either 1 M sodium thiosulfate or sodium sulfite to neutralize the presence of oxidizer in the solution.
  • the use of sodium sulfite can efficiently neutralize the oxidizer that may present in the final eluent.
  • Typical composition of the eluent obtained from these experiments is given in
  • Example 8 The effect of temperature and solid to liquid ratio in presence of oxidizing agent (sodium hypochlorite) in the solution on molybdenum uptake onto MPCM-CIO 2 resin were investigated. Batch studies were performed at predetermined different temperatures following the procedures previously mentioned. For each experiment, approximately 1 gram of MPCM-ClOj resin was exposed to 100 mL of 1%
  • the heat of adsorption at different loadings of molybdenum on oxidized MPCM is shown in Figure 22.
  • the heat of adsorption of molybdenum decreased with the increase of loading that can be attributed to heterogeneity of the surface and multi- layer coverage.
  • the heat of adsorption approached the integral heat of adsorption ( ⁇ value) at higher loading.
  • ⁇ value integral heat of adsorption
  • the subsequent increase in the heat of adsorption may be attributed to lateral interactions between the adsorbed molybdenum ions, which arc known to form complex molecules on a solid surface. It was expected that adsorption surface sites of the resin will be homogeneous energetically and, therefore, a constant heat of adsorption should be obtained. However, the resin surface seems to become heterogeneous energetically, because of the micro-porosity of the surface.
  • FIG. 23 shows experimental data of a 0.5 Ci (at the time elution) 99 Mo/ 99m Tc generator described above that typically requires approximately 1.6 to 1.8Ci 99 Mo (EOl) from the very beginning.
  • the MPCM-CIO 2 resin is capable of adsorbing almost 99% of the available molybdenum from a 1% molybdenum solution mixed with 25 mM sodium hypochlorite within 1 hour of exposure when a solid to liquid ratio of 2: 100 was used.
  • the molybdenum loaded MPCM-ClO 2 resin thoroughly using de-ionized water, at least 90% (or up to 95%) molybdenum found to be retained in the resin, which can be used to prepare a column for a generator. This will ultimately reduce the losses of 99 Mo activity during the adsorption cycle and during generator processing and handling.
  • chitosan was added to 300 mL dcionized (Dl) water with 1 mL acetic acid and stirred for 2 hr at 70°C to form a gel.
  • About 4 mL of HCI was added into the chitosan gel and kept under continuous stirring for another 1 hr at 70°C.
  • an amorphous titania gel was prepared by acid catalyzed controlled hydrolysis and condensation of titanium isopropoxide. See Hasan, S., Ghosh, T.K., Prelas, M.A., Viswaneth, D.S., and Boddu, V.M. "Adsorption of uranium on a novel bioadsorbent chitosan coated perlite" Nuclear Technology, 159, 59-71 , 2007; Schattka, J. H., Wong, E. H.-M., Antonictti, M., and Caruso, R.A.
  • IP H 2 O: ⁇ + ⁇ 0.0132:0.39: 1.67:0.01. Based on the concentration ratio of the reactants, the gel time was varied between 25 and 45 minutes.
  • a sol-gel solution of amorphous titania was mixed with chitosan gel.
  • the mixture was kept under stirring at 70°C for another 1 hr for complete reaction of chitosan and amorphous titanium oxide.
  • the reaction with gluteraldehyde was performed by drop-wise addition of about 6 mL gluteraldehyde solution having a concentration of 50% to the acidic chitosan titania gel under 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 hr to obtain a semi-solid gel.
  • the resulting mass was thoroughly washed with 2% monocthanol amine to remove any unreacted gluteraldehyde.
  • the mass was then suspended in 0.1 M NaOH solution for 4 to 6 hr.
  • the cross-linked mass was separated from the solution and washed with 0.1M HCl and then with deionized water (DI) until the pH of the washed solution was 7.
  • DI deionized water
  • the cross-linked mass was then dried in a vacuum oven overnight at 70°C.
  • the cross-linked chitosan gluteraldehyde composite prepared in this process is referred to as "CGST" herein.
  • chitosan shows two peaks at 1157 cm" 1 and 1070 cm -1 , corresponding to the stretching of a C-0 bond of C3 of chitosan (secondary OH) and C-O stretching of C6 of chitosan (primary OH), respectively.
  • MPCM chitosan based micro-porous composite material
  • the stabilization study for MPCM was conducted at 50,000 krad using a 60 Co irradiator as a y-sourcc.
  • FTIR, XPS, and EDS X-ray microanalysis spectra revealed that the intensity of C, O, and N peaks of MPCM did not change substantially after irradiation.
  • Mo (VI) adsorption from aqueous solution at 298K MPCM can hold up to 60% of its own body weight.
  • the MPCM and its derivatives demonstrates the capacity to adsorb 99 Mo and release the daughter product 99m Tc simultaneously under both batch and equilibrium conditions.
  • a 99 Mo/ 99m Tc generator based on low specific neutron captured produced molybdenum has been prepared using a novel MPCM resin as an adsorbent.
  • the oxidized MPCM resin is found to be capable of adsorbing >95% of available molybdenum from the 1% solution at solution pH 3.0 when solid to liquid ratio is 2:100.

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Abstract

L'invention concerne des sorbants microporeux de chitosane réticulés par le glutaraldéhyde, leurs procédés de fabrication et d'utilisation, et un générateur pour le radioisotope 99Mo contenant les sorbants.
EP15861884.3A 2014-11-19 2015-11-19 Préparation de matière composite microporeuse à base de chitosane et ses applications Withdrawn EP3221265A4 (fr)

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