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Fibrous amidoxime adsorbents were prepared by radiation-induced co-grafting of acrylonitrile (AN) and methacrylic acid (MAA) and subsequent amidoximation. Adsorption of uranium in seawater was evaluated by pumping seawater into the adsorbent column. The best monomer ratio of AN and MAA was 7 : 3 for continual usage of uranium adsorption. Though hydrochloric acid is an effective eluting agent for the metals adsorbed on the adsorbent, amidoxime groups were simultaneously damaged after five cycles of adsorption -desorption. This deterioration was reduced by an alkaline treatment of the adsorbents after each elution. Furthermore, various organic acids were examined as elution agents. It was found that the 80% of adsorption activity was still maintained after five cycles of adsorption -desorption when tartaric acid was used for eluting agent.

Secondary and tertiary amino groups were introduced into polymer chains grafted onto a polyethylene flat-sheet membrane to evaluate the effects of surface properties on the adhesion and viability of a strain of the Gram-negative bacterium Escherichia coli and a strain of the Gram-positive bacterium Bacillus subtilis. The characterization of the surfaces containing amino groups, i.e. ethylamino (EA) and diethylamino (DEA) groups, revealed that the membrane potentials are proportional to amino-group densities and contact angle hysteresis. A high bacterial adhesion rate constant k was observed at high membrane potential, which indicates that membrane potential could be used as an indicator for estimating bacterial adhesion to the EA and DEA sheets, especially in B. subtilis. The bacterial adhesion rate constant of E. coli markedly increased at a membrane potential higher than "7?8 mV, whereas that of B. subtilis increased at a membrane potential higher than "8?3 mV, at which the dominant effect on bacterial adhesion is expected to change. The viability experiments revealed that approximately 80 % of E. coli cells adhering to the sheets with high membrane potential were inactivated after a contact time of 8 h, whereas 60 % of B. subtilis cells were inactivated. Furthermore, E. coli viability significantly decreased at a membrane potential higher than "8 mV, whereas B. subtilis viability decreased as membrane potential increased, which reflects differences in cell wall structure between E. coli and B. subtilis.

Total amount of uranium resource in seawater is one thousand times of that in terrestrial ores. A polymeric adsorbent being capable of collecting uranium in seawater was developed in early 1980s, since uranium is inevitable resource to operate atomic power plants. This adsorbent fabric was synthesized by radiation-induced graft polymerization which could impart a desired functional group into fibrous trunk polymers. The amidoxime group was selected as a high affinity group for uranium collection from seawater. As a marine experiment, 350kg of the adsorbent stacks was dipped at 7 km offing of Mutsu-Sekine seashore in Aomori prefecture, Japan. In total 9 tests over three years, 1 kg of uranium could be collected successfully as a yellow cake. A new braid type adsorbent has been developed to achieve the practical cost of uranium collection. This braid adsorbent can stand on the bottom of the sea and does not need the heavy adsorbent cage for adsorbent stacks. The adsorption performance in marine experiment indicated 1.5 g-U/kg-ad for 30 day soaking. This value was three times higher than that of adsorbent stacks. The collection cost of uranium was calculated by including processes of adsorbent production, uranium collection, and purification at annual collection scale of 1200 t-U. The uranium collection cost based on the adsorbent durability in the laboratory scale experiment, 32 thousand yen/kg-U. When the braid type is utilized 18 times, the collection cost reaches 25 thousand yen/kg-U which

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