Covalent organic polymer-based sodium alginate composite beads: Decontamination of ciprofloxacin micro-polluted groundwater in a PRB system

The ecological threat posed by ciprofloxacin (CIP) contaminated groundwater could be settled by permeable reactive barriers (PRB) technology. However, exploiting proper and recyclable backfill medium was a major challenge for a PRB system. Herein, a novel three-component covalent organic polymer (SLEL-7) was synthesized by a solvothermal method for the adsorptive purification of CIP in groundwater, followed by the successful introduction into sodium alginate to acquire excellent recyclable beads (SLEL-7@SA beads) achieving enhanced adsorption behaviors. Plausible adsorption mechanisms were proposed through characterizations and adsorption studies in addition to the main controlling factors, including pore filling effect, hydrogen bonding and π-π EDA interaction, of course, hydrophilic-lipophilic balance and electrostatic interaction also took part in. Aside from that, a laboratory PRB column loading SLEL-7@SA beads as backfill medium was established which could continuously treat 60 bed volumes (BVs) of CIP (500 μg·L –1 ). And to be more specific, the Thomas, Yoon-Nelson and Adams-Bohart models were applied to predict the dynamic behaviors of CIP adsorption in the column. Overall, this work emphasized the structural and functional design of three-component COPs and the great potential of macroscopic COP@SA composite beads for in-situ remediation of CIP micro-polluted groundwater.