Removal of Iodinated Contrast Media Using Surfactant-Modified Montmorillonite Clay: Batch and Column Studies

This study investigates removal of iodinated contrast media (ICMs) agents from water using modified clay materials. ICMs pose a significant environmental challenge due to their high stability and resistance to conventional treatment methods. Their global annual consumption exceeds 12 × 10⁶ kg and are characterized by near-complete excretion within 24 hours of medical administration [1,2]. Recent advances in surfactant-modified organoclays have demonstrated their exceptional potential as sustainable remediation materials for emerging contaminants, including per- and polyfluoroalkyl substances (PFAS), antibiotic compounds, and other persistent organic pollutants [3,4]. No such study has investigated their applicability for the removal of ICMs. Here, we synthesized and investigated three montmorillonite-based adsorbents: pristine montmorillonite (Mt), single-modified montmorillonite functionalized with cationic surfactant cetyltrimethylammonium chloride (Mt-CTAC), and dual-modified montmorillonite incorporating both cetyltrimethylammonium chloride and anionic sodium dodecyl sulfate surfactants (Mt-CTAC/SDS). Batch adsorption experiments using Iohexol as a model ICM compound demonstrates superior removal efficiency for Mt-CTAC/SDS as compared to unmodified Mt and single-modified Mt-CTAC across various concentrations (5-150 mg/L). The dual-modified clay shows enhanced adsorption capacity, removal efficiencies reaching up to 90% under optimal conditions. Fixed-bed column studies are conducted using Mt-CTAC/SDS at different clay-to-sand ratios (0.05:1, 0.1:1, and 0.3:1), investigating the effects of flow rate (0.1-2.5 mL/min) and initial ICM concentration on solute breakthrough behavior. The ensuing breakthrough curves show that increasing clay content in the composite improves removal capacity, higher flow rates consistently leading to earlier breakthrough. Our findings highlight the potential of dual-modified montmorillonite as an effective adsorbent for ICM removal from water systems, providing insights for scaling up this treatment approach in environmental remediation applications.

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