Optimization of Activated Carbon Yield from Sargassum spp. Using Response Surface Methodology and Ridge Analysis

Sargassum spp. is an abundant marine biomass whose massive accumulation along Caribbean coasts has generated environmental and economic impacts. Its conversion into activated carbon (AC) provides an alternative for biomass utilization. In this study, the preparation conditions of activated carbon from Sargassum spp. were optimized using Response Surface Methodology (RSM) and Ridge analysis, with the objective of maximizing activated carbon yield. A 32 factorial design with three replicates per treatment was used to evaluate the effects of the H3PO4 impregnation ratio (1:1, 2:1, and 3:1) and activation temperature (400, 450, and 500 °C). A second-order polynomial model was fitted and evaluated through analysis of variance, lack-of-fit testing, coefficients of determination, and residual analysis. The fitted model showed adequate statistical performance, with an adjusted R2 = 0.820 and a non-significant lack of fit. Canonical analysis indicated a saddle-type stationary point located outside the experimental region, which motivated the use of Ridge analysis to identify feasible conditions associated with maximum predicted yield within the design region. The highest predicted yield along the feasible Ridge trajectory corresponded to an impregnation ratio of approximately 2.13:1 and an activation temperature of approximately 400 °C, with a maximum estimated yield of 44.91%. The results show the usefulness of combining RSM, canonical analysis, and Ridge analysis for identifying high-yield feasible operating conditions for the conversion of Sargassum spp. into activated carbon when the stationary point lies outside the experimental domain.