An electrochemical method for the sustainable extraction of iodine and sodium alloys

Extracting molecular iodine (I 2 ) from iodine resources is crucial for ensuring a sustainable I 2 supply, as high-grade brines/mines are depleting. Conventional extraction methods use chlorine gas (Cl 2 ) and sulfur dioxide (SO 2 ) and generate secondary wastes. To address these challenges, we propose an electrochemical method to extract I 2 from iodine resources or I − -containing wastewater using electrons instead of Cl 2 and SO 2 . First, an I − -vacancy BiOI film adsorbs iodide salts (primarily NaI) extracted from seaweeds. The extracted iodide salts are then electrochemically split into I 2 vapor (>99.6 %) and Na alloys in molten salt at 630 °C. The liquid metal cathode reduces energy consumption and prevents I 2 from reacting with Na. The resulting Na alloys can be used directly or further processed to produce pure Na. Life cycle assessment shows that this process has a global warming potential of only 1.48 kg CO 2 per kg of I 2 and an end-point environmental impact of 57.9 mPt due to the avoidance of Cl 2 (154.0 mPt for the conventional method). This study offers a clean approach to reducing reagent usage, decreasing solid waste, and promoting environmentally sustainable resource extraction.