A sustainable global energy transition will entail increased use of renewable energy sources, particularly wind and solar, and nuclear energy as a low-carbon energy source. Nuclear energy is “carbon-free,” meaning that, like wind and solar, it does not directly produce carbon dioxide (CO2) or other greenhouse gases that contribute to climate change. This makes nuclear energy instrumental in alleviating the global energy crisis and reducing greenhouse gases. However, the reprocessing of nuclear fuel has become an increasingly concerning issue for countries around the world today. Radioactive matter produced in the reprocessing of spent fuel is hazardous to the environment and human health, especially volatile radioactive iodine. (1) As a volatile radioactive waste, radioactive iodine has an extremely long half-life ( ¹²⁹I, t _1/2 = 1.57 × 10⁷ years) (2) with beta minus and gamma emissions (131I). (3) In addition, due to the thyroid’s enrichment of iodine, they can cause continuous damage to human health through the respiratory tract and food chains. (3,4) Therefore, there is a great need to remove radioactive iodine from the environment. (5,6)

So far, adsorption has become a widely used method of iodine capture for its versatility, effectiveness, and maneuverability. Common porous solid adsorbents include silver-containing materials, (7) metal–organic frameworks (MOFs), (8?10) conjugated microporous polymers, (11?13) covalent organic frameworks (COFs), (14?17) porous aromatic frameworks, (18,19) etc. Furthermore, ionic liquids (ILs) and deep eutectic solvents (DESs) have been used to efficiently capture and store I2 due to the halogen bonding between I2 and halides in ILs/DESs. (20?22) Although most of these adsorbents have considerable iodine adsorption capabilities, they are inevitably synthesized by expensive monomers and catalysts, complex preparation processes, or harsh conditions, which are not suitable for large-scale applications. Therefore, developing effective iodine adsorbents directly from accessible and low-cost starting materials, especially natural biomass resources, is a feasible strategy.

Seaweeds, mainly macroalgae that can be seen with the naked eye, are classified into three major groups: brown algae (Phaeophyceae), green algae (Chlorophyta), and red algae (Rhodophyta). (23) There are many kinds of seaweeds, and to date, tens of thousands of different seaweeds have been identified. (24) Seaweeds generally reproduce asexually, which allows for fast propagation of the species. Moreover, it has been more than 70 years since seaweeds were shown to be among Earth’s most productive organisms. (25) Due to their rapid regeneration, seaweeds grow in abundance in oceans. The annual macroalgae harvest from wild and cultivated crops was 28.4 million tons in 2014. This is a rise of 43% compared to 2010, when 19.9 million tons of seaweed were harvested. (26) On the other hand, the massive scouring of coastal shores by seaweeds has caused serious economic damage to tourism, aquaculture, and traditional fisheries. The “algal bloom” caused by seaweed flooding occurred in 126 coastal countries globally. (27) Therefore, fast-regenerated and abundant seaweeds may be biomass resources for sustainable development. The industrialization of seaweeds has a history spanning more than 300 years. Whether from aquaculture or algal blooms, seaweeds contain considerable amounts of alginic acid (HAlg). Due to their abundance, renewability, and low cost, alginic acids are widely used in food, pharmaceuticals, and biomaterials. In the laboratory, alginate’s abundance of hydroxyl and carboxyl functional groups makes it an ideal raw material for the preparation of a variety of functional adsorbents...

Scheme 1. Fabrication of Alginate-Based Ionic Polymer Composite (AIP@MF)