Water treatment through adsorption is widely used to remove organic and inorganic micropollutants. This study aims to evaluate the removal of Safranin O, a cationic dye, using activated carbons derived from marine algae. The performance of these bio-based activated carbons was compared to that of a commercial activated carbon. Adsorption isotherms were modeled using the Langmuir, Freundlich, and Temkin models in both their linear and nonlinear forms. The results were validated through error analyses, including the chi-square (χ²) test and the Average Percentage Error (APE). The maximum adsorption capacities observed were 384.61 mg×g-1 for activated carbon derived from brown algae, 526 mg×g-1 for green algae, and 400 mg×g-1 for the commercial activated carbon. Among the studied models, the linear form I of the Langmuir model and the nonlinear forms of all three models accurately described the adsorption of Safranin O onto the prepared and commercial activated carbons, with correlation coefficients (R²) exceeding 0.90 and low error values.