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内容記述 |
Gadolinium (Gd)-based contrast agents used in MRI investigations are structured with strong chelate bonds to ensure safety from human administration to urination. On the other hand, this Gd contrast agent is widely discharged into the environment after MRI investigations. After passing through sewage treatment, the treated waste water directory discharged into the environment, it denatures as highly toxic Gd3+ ions, which accumulate in aquatic organisms and have a high potential to affect biological life. However, acceptable concentration levels of Gd in aqueous media have not been established, raising concerns about future environmental contamination.We would like to propose a novel method to introduce chelating groups onto conventional polymeric materials. As one of the methods to remove Gd contract agent derivatives from water body, we examined an adsorption material with iminodiacetic acid groups introduced by radiation-induced graft polymerization (RIGP). RIGP has the advantage that general-purpose polymer materials with various shapes and properties can be freely selected, and desired functions can be introduced at high density. In this study, we report on the evaluation of the stability of Gd contrast agents and the characterization of Gd-adsorbent that can adsorb Gd, aiming at the establishment of a Gd removal technique from the environment.Based on previous results, the grafting using emulsified vinyl acetate monomer enhanced Dg (degree of grafting) 100 times higher than that obtained by grafting with the monomer dissolved in organic solvent such as methanol. This means that emulsification of GMA in water effectively promotes grafting, and showed that Tween 20 were suitable surfactants to stabilize GMA micelle in water. When the PE nonwoven fabric was used as a trunk polymer for emulsion graft polymerization, Dg reached 220 % for 1 h grafting at 40 °C. When Dg is 220%, the molar density of epoxy group is calculated to be 4.8 mmol/g-grafted PE fiber. If the conversion of the epoxy group is more than 50 %, the synthesized Gd adsorbent has 2.2 mmol/g-adsorbent. |
