Collaboratively scavenge tetracycline and Cu²⁺ from their combined system by Fe³⁺-modified magnetic chitosan: Performance, mechanisms, and dynamic sorption process

Some trace heavy metals, used as feed additives to promote animal's growth, often coexist with antibiotics in aquaculture wastewater to form combined pollution, inevitably altering their adsorption behavior and mechanism on adsorbent surfaces. Until now, there are still no studies on systematically unravelling dynamic adsorption process of both heavy metals and antibiotics at different sorption stages. Thus, a novel Fe3+-modified magnetic chitosan composite (MCS-Fe3+) was facilely fabricated as a model adsorbent for revealing its coadsorption behavior and mechanism toward Tetracycline (TC) and Cu2+. It was found that the as-resultant adsorbent displayed extraordinary sorption capability toward TC with qmax value of 230.66 mg g(-1). The cooperation of multi-mechanisms (e.g., H-bonding, electrostatic attraction, and Fe3+-complexation) enables TC adsorption to reach equilibrium within 15 min. Interestingly, in TC-Cu2+ binary system, the co-existing Cu2+ or TC dramatically promoted each other's removal efficiency at pH of 6 due to formation of ternary complex (adsorbent-Cu2+-TC or adsorbent-TC-Cu2+). Most importantly, a 'Three-stage' adsorption profile of TC and Cu2+ in their mixed system was firstly proposed and described in details, providing unique insights into adsorption pattern of multi-pollutants in actual wastewater. Moreover, the as-designed composite was applied for treating simulated aquaculture wastewater bearing different ratios of TC and Cu2+ and satisfactory removal rates over 80 % were obtained, confirming its feasibility in simultaneously and cooperatively eliminating TC and Cu2+ in complex wastewater.