At low pKa values (~ -4 to 0), Kd remains low, likely due to the adsorbate being predominantly ionized, which weakens its interaction with the adsorbent. Similarly, at extreme pHpzc values (~2 or ~10-12), Kd declines, possibly due to strong repulsive forces between the adsorbate and adsorbent surface. The wave-like curvature of the surface plot emphasizes the complex interplay between electrostatic interactions and hydrophobic adsorption mechanisms, reinforcing the importance of balancing adsorbate chemistry (pKa) and adsorbent surface charge (pHpzc) for maximizing adsorption performance. Figure illustrates the interaction between pHpzc and temperature (°C) on the distribution coefficient (Kd) for PFAS adsorption. The surface displays a nonlinear curvature, indicating that both variables significantly influence adsorption performance. Temperature has a positive effect on Kd, with moderate increases in temperature promoting adsorption, possibly due to enhanced molecular interactions and increased kinetic energy facilitating PFAS diffusion to adsorption sites. However, the plot also reveals a saturation effect, where the influence of temperature and pHpzc plateaus at higher values, suggesting that further increases in these parameters do not yield proportional improvements in adsorption efficiency. The interaction between temperature and pHpzc suggests optimal adsorption conditions at moderate temperature levels (around 30 -35 °C) and higher pHpzc values. These insights highlight the need for balancing operational parameters to maximize PFAS removal efficiency under practical environmental conditions.