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Environmentally friendly magnetic sodium alginate beads with glutaraldehyde cross-linking catalyzed by acetic acid-hydrochloric acid were successfully designed (FSSi@SA), and the magnetic bio-sorbents after amide reaction (FSSi@SA-sula) were utilized to absorb fluoroquinolone antibiotics in water. After amidation, FSSi@SA-sula exhibited strong pH adaptability (pH = 6.0–12.0). Langmuir and pseudo-first-order models can better describe the isotherm and kinetic process well, respectively. Under the optimization conditions with pH = 7 and temperature of 318.15 K, the maximum adsorption capacities of FSSi@SA-sula on the third-generation FQs ciprofloxacin (CIP) and the fourth-generation FQs moxifloxacin (MOX) respectively reached 365.66 and 149.57 mg g−1. The thermodynamics research indicated that the as-prepared FSSi@SA-sula is spontaneous and feasible. And after five adsorption cycles, the loss of adsorption capacity was less than 20% for both CIP and MOX, demonstrating the fine reusability and stability of the designed magnetic bio-sorbent. This study provides some ideas for facile synthesis of acid-catalyzed sodium alginate-glutaraldehyde cross-linking, which has promising applications in grafting various types of groups onto the retained carboxyl groups of sodium alginate spheres for the various contaminants removal in wastewater. [Display omitted] • FSSi@SA-sula beads were prepared by acid-catalyzed glutaraldehyde cross-linking. • FSSi@SA-sula showed excellent adsorption and reusability for CIP and MOX. • Langmuir and pseudo-first-order models better fitted adsorption process. • The mechanisms include electrostatic interactions, hydrogen bonding and n-π EDA. • Provided new ideas for facile synthesis of functional sodium alginate adsorbents. [ABSTRACT FROM AUTHOR]

In this paper, a novel magnetic sorbent based on silica coated iron oxide (Fe 3 O 4 /SiO 2 , denoted as FS), poly(ethylene imine) (PEI), sodium p-styrenesulfonate (SPS) and sodium alginate (SA) polymer (Fe 3 O 4 /SiO 2 /SA-PEI-SPS, denoted as FSSEP) is successfully prepared by free radical polymerization. Antibiotic (ciprofloxacin, CPX), dye (methylene blue, MB) and heavy metal (copper ion, Cu2+) are used to test the adsorption capacity of the prepared adsorbent. Compared with other adsorbents, FSSEP exhibited good capture efficiency for the pollutants in this study, especially for organic pollutants (CPX and MB). The maximum sorption capacity of FSSEP reached 203.99 mg g−1 for CPX, 423.69 mg g−1 for MB, 41.81 mg g−1 for Cu2+. Hydrogen bonding, electrostatic interaction, π-π interaction and cationic exchange are involved in the sorption mechanism. This study suggests a strategy for the design and synthesis of eco-friendly modified sodium alginate adsorbents through free radical polymerization and explores their potential application in the field of removal of different types of toxic substances. [Display omitted] • A new magnetic composite of FSSEP was synthesized by free radical polymerization. • Dye (MB), antibiotic (CFX) and Cu2+ ion were efficiently captured via FSSEP. • FSSEP microparticles can be regenerated and quickly separated from solution. • Adsorption mechanism of FSSEP was analyzed and discussed in this work. [ABSTRACT FROM AUTHOR]