Manganese Ferrite–Mesoporous Silica Adsorbent for Tetracycline Removal: Adsorption Behavior and Hydrogen Peroxide-Enabled Regeneration

Antibiotic residues in wastewater and natural waters require adsorbents that combine efficient capture, facile separation, and mild regeneration. However, conventional adsorption systems often suffer from incomplete desorption, secondary waste generation, or high regeneration costs. In this study, MnFe2O4@MCM-48 was constructed as a magnetic mesoporous adsorbent to integrate tetracycline (TC) adsorption with H2O2-assisted oxidative regeneration through Fe/Mn-mediated H2O2 activation. This design endows the composite with magnetic separability, accessible adsorption sites, and H2O2-activating redox centers, enabling separation, TC adsorption, and oxidative regeneration within one system. The optimized material exhibited a Langmuir model-estimated maximum adsorption capacity of 134.41 mg·g–1 at 298 K and maintained effective removal under varied pH values, coexisting ions, and water matrices. The adsorption of TC was associated with pore filling, electrostatic interactions, hydrogen bonding, and possible surface complexation. More importantly, H2O2 regeneration restored adsorption performance more effectively than NaOH elution. After five cycles, the H2O2-regenerated adsorbent retained 82.09% of its initial adsorption capacity, markedly higher than that after NaOH elution (49.17%), while preserving good magnetic recoverability. Reactive species identification, intermediate analysis, DFT calculations, and toxicity prediction showed that •OH dominated the oxidative process, during which TC underwent ring opening, dehydroxylation, demethylation, and amide-bond cleavage. Toxicity predictions indicated lower toxicity for most downstream products, while algal assays showed less inhibition by the regeneration solution than by TC under the tested conditions. Overall, this study provides an integrated separation–adsorption–regeneration strategy for constructing regenerable antibiotic adsorbents.