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

Abstract

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 SiO 2 nanofibers with a diameter of about 280 nm nanostructure-based membranes (Bi 2 S 3 @SiO 2 ) was successfully prepared to dispose of gaseous iodine. Results showed that the adsorption capacity of Bi 2 S 3 @SiO 2 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 Bi 2 S 3 @SiO 2 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 BiI 3 . 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 S 0 , S 3+ , and S 6+ . The oxidation states of bismuth and iodine are Bi 3+ and I − , respectively, revealed by X-ray photoelectron spectroscopy. The reactions between Bi 2 S 3 @SiO 2 nanocomposites and I 2 vapor are as follows: I 2 was reduced to be I − and the BiI 3 crystalline phase is the final form; S 2− in Bi 2 S 3 was oxidized to higher valences (S 0 , S 3+ , and S 6+ ), 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.