While the RSM model captured some meaningful trends, its overall predictive performance was limited. The moderate R 2 value of 0.031924 suggests that the model explains a portion of the variability in Kd, but the high p-values for many terms indicate potential overfitting or insufficient data diversity. These limitations are likely due to multicollinearity among variables, the inherently nonlinear nature of PFAS adsorption, and the relatively small dataset size. Despite these limitations, the RSM analysis provides practical insights into optimizing PFAS adsorption.