Comparative evaluation of isocyanurate-based resin performance towards organic contaminants in a fixed-bed adsorption system

Caffeine and dyes are persistent anthropogenic pollutants frequently detected in municipal and industrial wastewater. In this study, two isocyanurate-based hyper-cross-linked resins (ICY-AM and ICYAN-PA) were comparatively evaluated for the removal of caffeine and four reactive dyes from real batik wastewater under batch and continuous fixed-bed conditions, supported by density functional theory (DFT) simulations. Batch caffeine adsorption was strongly pH-dependent, with maximum Langmuir capacities of 121.2 mg/g for ICY-AM and 104.8 mg/g for ICYAN-PA, achieved near the point of zero charge of each resin. Density functional theory (DFT) calculations revealed that adsorption thermodynamics are governed by the resin charge state, with neutral surfaces exhibiting markedly stronger binding due to reduced solvation penalties. ICY-AM showed significantly more favorable intrinsic affinity toward caffeine. In contrast, fixed-bed column experiments demonstrated superior dynamic performance for ICYAN-PA for both caffeine and batik wastewater. Breakthrough modeling predicted higher dynamic capacities for ICYAN-PA (≈ 54.84–65.39 mg/g) than ICY-AM (≈ 48.81–58.39 mg/g) for caffeine. Notably, the resin with higher intrinsic batch affinity (ICY-AM) was outperformed under continuous flow by ICYAN-PA, demonstrating that thermodynamic binding strength does not predict column performance. For batik wastewater, ICYAN-PA achieved higher removal efficiencies (64.5–95.3%) and longer service times than ICY-AM (46.3–87.3%), attributed to its greater amine site density and narrower mass transfer zones. These findings highlight the complementary roles of intrinsic binding affinity and mass-transfer behavior in determining adsorbent performance and position isocyanurate-based resins as promising materials for multi-pollutant wastewater remediation.