Figure illustrates the non-linear relationship between Log Kow and surface area, and its interactive effect on Kd. Low Log Kow resulted in low Kd and high Log Kow resulted in high Kd, regardless of the surface area. These findings support the idea that PFAS compounds with higher hydrophobicity will have higher distribution coefficient and removal regardless of the adsorbent material. The surface plot in Figure illustrates the relationship between the Kd, pH, and pHpzc, providing insight into how electrostatic interactions influence PFAS adsorption. The quadratic response surface model (RSM) results indicate that both pH and pHpzc significantly impact adsorption, with regression coefficients of -1315.724 for pH and 302.180 for pHpzc, and respective p-values of 0.022 and 0.031, confirming their statistical significance. The negative coefficient for pH suggests that increasing pH decreases Kd, which aligns with the expected electrostatic behavior of PFAS adsorption. At high pH, the adsorbent surface is negatively charged (pH > pHpzc), leading to electrostatic repulsion with the anionic PFAS species, thereby reducing adsorption efficiency. Conversely, at low pH, the adsorbent surface carries a positive charge (pH < pHpzc), promoting electrostatic attraction and enhancing PFAS adsorption. The positive coefficient for pHpzc indicates that materials with a higher pHpzc exhibit greater Kd, suggesting that high pHpzc materials are more effective for PFAS adsorption. A higher pHpzc value means the material retains a positive charge over a wider pH range, reinforcing electrostatic attraction with anionic PFAS.