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

A new study published in the journal Environmental Surfaces and Interfaces compares two isocyanurate-based hyper-cross-linked resins—ICY-AM and ICYAN-PA—for removing caffeine and four reactive dyes from real batik wastewater.

The researchers from King Fahd University of Petroleum and Minerals in Saudi Arabia tested the materials under both batch and continuous fixed-bed conditions, and supported their experiments with density functional theory (DFT) simulations.

“In batch tests, caffeine adsorption was strongly dependent on pH, reaching maximum Langmuir capacities of 121.2 mg/g for ICY-AM and 104.8 mg/g for ICYAN-PA near each resin’s point of zero charge,” shares Professor Nisar Ullah, corresponding author of the study. “DFT calculations showed that adsorption thermodynamics are governed by the resin’s charge state: neutral surfaces bind caffeine markedly more strongly because they avoid the energy penalty of stripping away solvating water molecules.”

At the molecular level, ICY-AM showed the more favorable intrinsic affinity toward caffeine.

“Notably, the resin with the stronger intrinsic affinity in batch tests was not the one that performed best under continuous flow,” adds Ullah. “Thermodynamic binding strength alone does not predict how an adsorbent will behave in a real fixed-bed column, where mass transfer is often the deciding factor.”

In fixed-bed column experiments, ICYAN-PA delivered the superior dynamic performance for both caffeine and batik wastewater. Breakthrough modeling predicted higher dynamic capacities for ICYAN-PA (about 54.84–65.39 mg/g) than for ICY-AM (about 48.81–58.39 mg/g) for caffeine. For batik wastewater, ICYAN-PA achieved higher removal efficiencies (64.5–95.3%) and longer service times than ICY-AM (46.3–87.3%), an advantage attributed to its greater density of amine sites and narrower mass-transfer zones.

“The findings highlight the complementary roles of intrinsic binding affinity and mass-transfer behavior in determining how an adsorbent performs, and position isocyanurate-based resins as promising, tunable materials for the simultaneous removal of multiple pollutants from complex wastewater streams,” says Ullah.

Contact author details: Nisar Ullah, Interdisciplinary Research Center for Refining & Advanced Chemicals, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia. Email: nullah@kfupm.edu.sa

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