Chitosan-based adsorbents for antibiotic removal with insights from batch and dynamic studies: A review

Removing antibiotics from water systems is an urgent concern for modern society due to their toxicity and potential long-term ecological consequences. Among many treatment methods, adsorption by chitosan composites has proven to be one of the most promising approaches due to their biodegradability, abundant functional groups (amino and hydroxyl), and ease of modification. This review offers a detailed and up-to-date overview of the applications of chitosan-based composites for antibiotic removal, focusing on their effectiveness in both batch and dynamic (fixed-bed column) operations. It highlights that tetracycline is the most studied contaminant, and magnetic chitosan materials are the predominant adsorbents used. Chitosan-metal-organic frameworks composites exhibit some of the highest reported adsorption capacities. Adsorption is influenced by factors such as pH, initial concentration, and adsorbent dosage, with electrostatic attraction, hydrogen bonding, and π-π interactions identified as the main mechanisms. Kinetic analyses show that the pseudo-second-order model best describes adsorption rates, while the Langmuir isotherm often fits equilibrium data well. Both batch and dynamic (fixed-bed) studies demonstrate substantial removal efficiencies, although dynamic systems better simulate real wastewater treatment conditions and offer improved adsorbent utilization. This review emphasizes the possibility of using chitosan adsorbents in removing antibiotics and calls for further dynamic studies to validate their application in wastewater treatment.