Magnetically recoverable Fe₃O₄-chitosan/ZIF-8 beads for tetracycline removal from aqueous solution

The remediation of water contaminated by persistent antibiotic residues necessitates advanced treatment technologies that combine high removal efficiency with facile operational recovery. This study presents the development of a magnetically retrievable composite adsorbent, synthesized via ionic cross-linking co-assembly of pre-formed Fe₃O₄ nanoparticles and ZIF-8 nanocrystallites with industrial-grade chitosan. Comprehensive characterization (PXRD, FTIR, SEM, BET) confirmed the successful integration of components into a cohesive, macroporous bead architecture with robust mechanical stability. Process optimization utilized a hierarchical approach: initial univariate screening identified key operational parameters, which subsequently informed a multivariate Box-Behnken design. The derived second-order response surface model (R² = 0.9930) provided a benchmark for comparison against multiple machine learning algorithms, including support vector regression (SVR), Artificial Neural Networks, and tree-based ensembles. The SVR model demonstrated superior predictive accuracy (R² = 0.9994, RMSE = 0.434) and reliable extrapolation (predicted R² = 0.9618), enabling precise parameter optimization. At the identified optimum conditions (10 mg L⁻¹ tetracycline, 300 mg L⁻¹ sorbent, 135 min, pH 8.5), a sequestration efficiency of 74.04% was achieved. The composite exhibited excellent reusability, retaining > 60% of its initial capacity over five consecutive adsorption-desorption cycles, facilitated by rapid magnetic separation. Kinetic studies revealed that uptake followed a pseudo-second-order model (R² = 0.991), indicative of chemisorption, with an experimental maximum capacity of 24.5 mg g⁻¹. By unifying low-cost materials, a clear structure-property relationship, and a sophisticated modeling framework, this work provides a practical, magnetically separable adsorption system for the targeted removal of tetracycline in engineered water treatment.