Direct extraction of bromine from seawater through an electrolysis-driven styrene enrichment process

The seawater contains approximately 99% of Earth’s bromide reserves. Therefore, the extraction of bromine from the seawater offers a promising approach to ensure a sustainable supply of bromine. However, the traditional electrochemical extraction method for direct bromine extraction are inapplicable, owing to the low concentration of bromide in seawater (~60 ppm). In this work, we develop an electrolysis-driven styrene enrichment process for efficient bromide recovery from seawater. As for the electrooxidation of bromide, we screen a series of metal phthalocyanines supported on carbon nanotube as the electrocatalysts. Through accelerating the bromine evolution reaction and suppressing the side reaction, nickel phthalocyanine supported on carbon nanotubes exhibit the highest activity with the Faradic efficiency of 97.8% for bromine production among all catalysts. Coupling this catalyst with the ESE process for direct bromine extraction from the Yellow Sea’s seawater, the extraction efficiency of 90.0% is achieved with the product of pure KBr powder. Moreover, the co-produced styrene oxide can be efficiently separated via vacuum distillation, significantly promoting the economic value of this ESE process. Direct bromine extraction from seawater holds promise for sustainable bromine production but remains challenging. Here, the authors report an electrolysis-driven styrene enrichment process that captures and concentrates bromine species, enabling selective bromine extraction directly from seawater.