Spray-dried zinc-alginate microparticles for antibiotic removal from water: a promising approach to mitigate antibiotic resistance

Antibiotic residues in gastrointestinal and environmental compartments promote the selection of resistant bacteria and the emergence of antimicrobial resistance (AMR). This study evaluates spray drying as a scalable method to produce crosslinked zinc-alginate (Zn-Alg-SD) microparticles for antibiotic removal from water via metal complexation, using ciprofloxacin (CIPRO) and amoxicillin (AMOX) as model compounds. Zn-Alg-SD microparticles were prepared by spray drying at varying zinc (Zn2+) concentrations. Particle characteristics were assessed by FTIR, optical particle size analysis, SEM, and ICP-MS, demonstrating improved particle uniformity, surface area, water stability, and crosslinking density. Zn-Alg-SD microparticles prepared with 0.25% and 0.5% (w/v) Zn2+ exhibited minimal swelling in aqueous media, indicating enhanced structural integrity. Antibiotic removal studies showed high adsorption capacity, particularly for CIPRO, with a 20-fold increase compared to Zn-Alg beads produced by conventional ionotropic gelation. Kinetic modelling indicated a chemosorption mechanism for both antibiotics, supporting Zn2+-mediated complexation within the crosslinked alginate matrix. Overall, spray drying represents an efficient alternative to ionotropic gelation for producing crosslinked alginate adsorbents, offering a scalable platform for biological and environmental antibiotic removal.