Experimental and modeling investigations for high-efficiency removal of polar iodinated contrast media from water through engineered clays

Emerging contaminants such as polar iodinated contrast media (ICMs) are increasingly detected in aquatic environments and remain difficult to remove due to their high solubility, limited sorption affinity, and resilience to conventional treatment. This study presents a comprehensive experimental and modeling investigation aimed at engineering a dually modified montmorillonite (Mt-II) for efficient adsorption of the non-ionic ICM iohexol. Batch and continuous-flow experiments are synergistically integrated with a stochastic multimodel analysis to quantify parameter uncertainty and objectively evaluate competing model formulations using rigorous selection criteria. In batch systems, Mt-II achieves rapid uptake and high removal efficiency (∼93%), outperforming pristine and singly modified clays. Equilibrium data are most plausibly described by the Langmuir and Sips isotherms. On the other hand, kinetic analysis identified external film diffusion as the dominant rate-limiting step, indicating accessible engineered sorption sites. Under flow-through column conditions, Mt-II maintains strong performance, solute breakthrough behavior being governed by mass-transfer regimes dependent on sorbent loading, flow rate, and influent concentration. Stochastic modeling supports a conceptual picture according to which the Thomas and Yan models can reliably capture breakthrough dynamics across diverse operating conditions. Importantly, column capacities remain stable even at elevated influent concentrations, suggesting operation near the practical saturation capacity of the newly engineered material. Density-functional electrostatic potential mapping reveals complementary hydrogen-bonding and π-interaction domains between iohexol and the Mt-II interlayer, providing mechanistic support for macroscopic adsorption behavior. Collectively, these results establish a mechanistically grounded and statistically robust framework elucidating the behavior of tailored amphiphilic organoclays in the presence of pharmaceuticals such as non-ionic ICMs and advancing their potential application in next-generation water treatment technologies.