SYNOPSISA number of lightly cross-linked poly (acrylonitrile-co-divinylbenzene) beads ( RN-5 ) have been synthesized by suspension polymerization. The use of solvating diluents such as chloroform, dichloroethane, and tetrachloroethane resulted in copolymer beads having highly porous structures. The chelating resins containing amidoxime as a functional group (RNH-5 ) have been prepared by the reaction of copolymer beads with 3% hydroxylamine in methanol. A detailed analysis is made of the pore structure of lightly cross-linked copolymers of acrylonitrile-divinylbenzene and their amidoxime derivatives in the anhydrous state including pore-size distribution, specific surface area, and pore structure in the aqueous media by means of gel permeation chromatography (GPC) . A set of experiments have been performed to ascertain the potential of the resins for the adsorption of uranium from seawater. Because of their modified pore structures, the chelating resins exhibited a marked adsorption rate for uranium in seawater as high as 23 pg of U/cm3 of resinlday without alkaline treatment.

It was found that the chelating resins (RNH) containing amidoxime groups show the selective adsorption ability for uranium in sea water. The favorable chelating resins were prepared by the reaction of macroreticular acryronitrile-divinylbenzene copolymer beads with hydroxylamine in methanol. When sea water (104 times as large as the resin volume) was passed through the RNH column at the space velocity of 60 hr-1, 80% of uranium on that in sea water was recovered. The elution of uranium adsorbed on RNH was accomplished by passing 1 N sulfuric acid solution through it. The recycle of adsorption and elution was found to be satisfactory.

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SY NOPSlSPolypropylene fibers and polyethylene hollow fibers were used as trunk polymers and were irradiated by electron beams with a dose of 200 kGy under Nz atmosphere. Grafting of acrylonitrile to those irradiated fibers was carried out at 40°C for different periods of time. The degree of grafting was determined as a function of time. The fibrous adsorbents containing amidoxime groups were prepared by the reaction of acrylonitrile-grafted polymers with 3% hydroxylamine in a methanol-water mixture ( 1 : 1 ) . Distribution of copper ions complexed with amidoxime groups at various adsorption times was obtained by electronprobe X-ray microanalysis. The amidoxime groups are homogeneously distributed in the cross section of fibrous adsorbents. The fibrous adsorbents based upon polypropylene fiber of 40 pm showed a remarkable kinetic behavior for Cu2+. Even after 15 min, the adsorption capacity was 2.32 mmol Cu2+ per gram of fiber. Also, the functionalization with hydroxylamine was carried out at different conditions to compare the adsorption characteristics of the resultant adsorbents. Despite having superficially different properties (elemental microanalysis, ion-exchange capacities, adsorption capacity for UO ;+), the polypropylenebased fibrous adsorbents showed similar adsorption properties for uranium from sea water. The adsorption tests proved the performance of the polypropylene-based fibrous adsorbents as a promising material for uranium recovery from sea water. In addition, uranium uptake of fibrous adsorbents increased in proportion to the volume of sea water. 0 1993

Lightly crosslinked poly(acry1onitrile-co-divinylbenzene) beads (RN-5) have been synthesized by suspension polymerization. The use of dichloroethane and chloroform as a porogen produced lightly crosslinked copolymer beads having highly porous structures. The chelating resins containing amidoxime groups (RNH-5) have been prepared by the reaction of copolymer beads with NHzOH in MeOH. The resulting chelating resins have been used in the batchwise adsorption of UO:+ from nitrate solutions containing 0.01 m~l . d m -~ UO:+ at pH 3.25. In order to get some measure of the relative performance of each resin in kinetic terms, the extraction of UO:+ was monitored with time and some adsorption profiles were obtained. An increase in porogen content resulted in a marked increase in the batchwise adsorption of UO:+. Alkaline treatment allowed a high swelling and hence rapid accessibility of UO:+ to the ligands. Even after 30 minutes, the alkali-treated resins were 50% loaded.

SynopsisThe macroreticular chelating resins (RSP, RSPO, RCSP, and RCSPO) containing dihydroxyphosphino and/or phosphono groups were prepared and their adsorption capacity for UO$+ and the recovery of uranium from sea water were investigated. RSP and RCSP were prepared by phosphorylation of macroreticular styrene-divinylbenzene copolymer beads and the chloromethylated copolymer beads, respectively. RSPO and RCSPO were prepared by oxidation of RSP and RCSP, respectively. The order of recovery of uranium from sea water with these four resins is as follows:The adsorption of uranium in sea water was not only affected by the chemical structure, but also by physical structure of the resins. Uranium adsorbed on the resins was eluted with 0.25 -1 m~l -d m -~ Na2C03 or NaHC03 solution by batch and column methods. The average recovery ratios of uranium from sea water with Na-form and H-form RCSP on 10 recycles were 84.9% and 90.5%, respectively, when 20 dm3 of sea water was passed through the column (resin 4 cm3, 10 mm $J X 50 mm) at the space velocity of 60 h-l. RCSP has a high physical stability and resistance against acid and alkali solution.

SYNOPSISEight types of amidoxime-type resin ( RNH) were derived from macroreticular acrylonitriledivinylbenzene copolymer beads, which were synthesized by varying the amount of polymerization initiator. Although these RNH are similar in chemical properties and physical pore structure, they exhibited different adsorption abilities for uranium. The porous structure of RNH in swollen state was analyzed by gel permeation chromatography in aqueous medium. The calibration curves yielded useful information on the pore structure of RNH in the swollen state and it was recognized that the pore structure in the swollen state is important for the improvement of the adsorption rate.

SynopsisWe have synthesized macroreticular chelating resins containing amidoxime groups from acrylonitrile (AN)-divinylbenzene (DVB)-alkyl acrylate, alkyl methacrylate, or vinylpyridine (VPy) copolymer beads. It was found that the chelating resin (RNMH)-containing amidoxime groups prepared from AN-DVB-methyl acrylate (MA) indicated the highest adsorption ability for uranium in seawater. Hydroxamic acid and carboxylic groups in addition to amidoxime groups were formed during the reaction of the copolymer beads with a methanol solution of hydroxylamine. The adsorption ability for uranium was greatly influenced by the physical pore structure (macropore) and the pore structure formed by the swelling(microp0re). RNMH prepared with 10 mol% of DVB and 10 mol% of MA had the highest adsorption ability and physical stability for uranium. On the other hand, improved adsorption ability for uranium was not obiserved in the case of the macroporous resins (RNPyH) prepared by the copolymerization of VPy as the basic component. After seawater was passed through the column packed with RNMH10-10 at a space velocity (SV) of 180 h-' (up-flow) for 10 days, the amount of uranium adsorbed on the resin was about 100 mg/&-R and 260 mg/kg-R. INTRODUCTIONSince atomic power is expected to play an important role in energy resources, the industrial system of uranium recovery from natural seawater, which contains approximately 4 billion tons of uranium, must be established in the near future. We have already synthesized the macroreticular chelating resins containing amidoxime1-6 and dihydroxyphosphino and/or phosphono groups,' which are highly effective for the recovery of uranium from seawater.'-" In this research, it has become apparent that the physical and chemical structure of adsorbents greatly influence the adsorption ability for uranium from seawater. In recent years there have been reports on the synthesis of some adsorbents and the application of uranium recovery from seawater (e.g., chelating resins containing dithiocarbamate groups,12 amidoxime group^,^^*^* 1,2-dihydroxyanthraquinone groups,15 and aminomethylphosphonic acid group^.'^^") In these reports, the physical and chemical structure of uranium adsorbents seems not to be well defined. In our recent study,6 the macroreticular chelating resins containing amidoxime groups with various pore structures have been prepared by using several crosslinking reagents, and the inhence of the pore structure on the adsorption ability for uranium was were washed with pure water until hydroxylamine was not released in the wash water, then were air-dried, and dried in vacuo at 40°C for 6 h. Each resin (1 g) was treated with 100 cm3 of 0.1 mol * dmP3 sodium hydroxide solution at 3OoC for 15 h (alkali treatment) or with a 100 cm3 of 1 mol . dm-3 hydrochloric acid solution at 60°C for 5 h (acid treatment). The resulting resins were washed with deionized water until the wash water became neutral and then were air-dried and dried in vacuo at 40°C for 2 h. An apparent anion and cation exchange capaci...