Transforming <i>Sargassum</i> into Valuable Solid Carbon Materials: A Review of Synthesis Methods

The valorization of Sargassum into valuable carbon materials is not only driven by the need to manage its massive accumulation on beaches every year, posing ecological, economic, and health challenges, but also by its unique composition rich in carbohydrates and bioactive materials, making it an ideal precursor for carbon-rich materials. Among various thermal transformation methods, hydrothermal carbonization, slow pyrolysis, and microwave-assisted methods (microwave-assisted hydrothermal carbonization and microwave-assisted pyrolysis) have been employed to convert Sargassum into solid carbon-based materials, such as hydrochar, biochar, carbon quantum dots (CQDs), and activated carbon. These materials have demonstrated a significant role in diverse applications, including water purification, soil enhancement, energy storage, catalysis, and biomedical fields. This review discusses these synthesis methods, essential pretreatment processes to prepare Sargassum before the synthesis processes, and posttreatment processes aimed at enhancing the carbon material properties. Finally, the work also discusses the challenges of Sargassum valorization and presents future directions. Given the scale of Sargassum overgrowth affecting coastlines in the Caribbean, Gulf of Mexico, and Atlantic Ocean, this review is significant in highlighting strategies for transforming marine biomass into high-value carbon materials and provides a review of the existing studies on the conversion of Sargassum into carbon materials.