What do we know about the utilization of the Sargassum species as biosorbents of trace metals in Brazil?

In the last decades, metal pollution has become one of the most critical environmental and public health concerns. Human use and processing of trace metals have altered these metals' natural biogeochemical cycles, which is causing adverse impacts on human beings, natural communities, and aquatic ecosystems. In Brazil, mining and smelting are relevant metal contamination sources that affect many aquatic systems, besides agricultural residues, industrial and urban effluent discharges. In this context, seaweed biosorption is a promising technology for the removal of metals from wastewater that could prevent environmental contamination. Seaweeds show high metal sequestering capacities, cost-effectiveness, and eco-friendliness. In this review, we aimed to assess previous studies on trace metals biosorption using the brown seaweed of the genus Sargassum conducted in Brazil during the last two decades (1999-2019). An overview of metal pollution in Brazil and its possible treatments are presented. A theoretical basis regarding Sargassum and its mechanism of sorption of trace metals is described. We also discuss previous Brazilian studies on this topic, including their aims, the trace metals analyzed, and the experimental conditions that increase biosorption effectiveness, which include pH, temperature, algae pretreatment, and immobilization of the biosorbent in a matrix. Given the abundance of this genus throughout the Brazilian coast and its high metal recovering capacity, the algae sorption process remains an underexplored resource. We conclude this work with a patent search and a discussion of the future perspectives of Sargassum use by society.