Synthesis of a novel magnetic nano-scale biosorbent using extracellular polymeric substances from Klebsiella sp. J1 for tetracycline adsorption

The magnetic nano-scale biosorbent (Fe₃O₄/MFX) was synthesized by the chelation and cross-linking procedure with extracellular polymeric substances (MFX) and Fe₃O₄. Fe₃O₄/MFX possessed the porous structure and numerous functional groups (i.e., amino, carboxyl, and hydroxyl), and its core region had a typical size of ∼11nm. The maximum adsorption capacity was 56.04mgg^-1 at pH 6.0, 10mgL^-1 of tetracycline, and 160mgL^-1 of Fe₃O₄/MFX. The data is properly fitted by the Langmuir, Freundlich, and pseudo-second-order kinetics models. As elucidated by the model parameters and FTIR analysis, chemical ion exchange and COOH could mainly contribute to the adsorption. Meanwhile, the desorption and regeneration experiments implied the adsorption efficiency decreased by only 3.37-8.37% after five adsorption-desorption cycles, and the detection of iron leaching by ICP-OES showed a fine stability of Fe₃O₄/MFX. Therefore, this technically facile, easily recyclable, and environmentally friendly biosorbent has potential for practical applications in antibiotic removal.