Decontamination of Extra-Diluted Radioactive Cesium in Fukushima Water Using Zeolite–Polymer Composite Fibers

Zeolite and poly­(ethersulfone) (PES) were composited by wet spinning technique to be Cesium (Cs) fiber adsorbent having porous morphology. The coagulation process was carried out by using PES-N-methyl-2-pyrrolidone solution dispersed with zeolite powde, and then, the extruded spinning solution was coagulated at 25 °C in water to form zeolite composite fibers. The resultant fiber composited with 59 wt % zeolite loading in PES fiber had 0.75 nm diameter and 136 m2/g surface area and adsorbed 136 mg/g saturation binding to nonradioactive Cs, obeying Langmuir analysis. For decontamination of radioactive Cs in the city of Date during October–December 2012 for 28 days, the fiber adsorbent was used in a rice field side river. A total of 7700 Bq/kg of radioactive Cs was captured in the composite fiber, while zeolite powder was shown with 33 Bq/kg. The comparison indicated that the fiber adsorbent was excellent during their long termed immersion in the field river. Also, in the town of Okuma in January–November 2015 for 338 days, the fiber adsorbent detected 6800 Bq/kg by flowing river immersion. Evidence was noted that the fiber adsorbent effectively remediated contaminant water with extra-low-level concentrations of radionuclides. Even four years after the accident, results strongly suggested that the Cs contamination still distributed in the field water with extra-low-level concentrations at the tested areas. It was described as first report especially that low-level Cs in the flowing river was effectively decontaminated by the fiber adsorbent, preventing its flow further downstream by the diffusion of radioactive Cs through water contaminant in natural environments.