Combining Electrospinning and Hydrothermal Methods to Prepare Bi2S3@SiO2 Nanostructure-Based Membranes for Enhanced Capture Capacity of Off-Gas Iodine from a Nuclear Plant

As the main fission products of nuclear power plants, radioactive iodine isotopes are of great concern because of their great harm to public safety. In this work, a nanocomposite of bismuth sulfide coated with the electrospinning SiO2 nanofibers with a diameter of about 280 nm nanostructure-based membranes (Bi2S3@SiO2) was successfully prepared to dispose of gaseous iodine. Results showed that the adsorption capacity of Bi2S3@SiO2 for iodine can be up to 1180 mg g–1, which is higher than the commercial silver-exchanged zeolite (AgZ) and other bismuth-based adsorbents. Chemisorption is the major adsorption behavior of iodine capture. Thermogravimetric analysis results demonstrated that the Bi2S3@SiO2 nanocomposites were stable up to 300 °C before and after capturing iodine. X-ray diffraction results revealed that BiSI was initially formed and then transformed to BiI3. Scanning electron microscopy revealed that the sulfur element remains in the samples after interacting with iodine, and X-ray absorption near-edge spectra further confirmed that its oxidation states are a mixture of S0, S3+, and S6+. The oxidation states of bismuth and iodine are Bi3+ and I–, respectively, revealed by X-ray photoelectron spectroscopy. The reactions between Bi2S3@SiO2 nanocomposites and I2 vapor are as follows: I2 was reduced to be I– and the BiI3 crystalline phase is the final form; S2– in Bi2S3 was oxidized to higher valences (S0, S3+, and S6+), and amorphous phases are their final forms. The research results demonstrated that the nanostructure-based membranes prepared by this work would be a promising candidate nanomaterial for capturing iodine in the plant off-gas streams.