New insight into enhanced transport of multi-component porous covalent-organic polymers with alkyl chains as injection agents for levofloxacin removal in saturated sand columns

Levofloxacin (LEV) is prone to be retained in aquifers due to its strong adsorption affinity onto sand, thus posing a threat to groundwater quality. In-situ injection technology for remediating LEV-contaminated soil and groundwater is still challenging owing to the lack of appropriate remedial agents. Herein, two novel multi-component porous covalent-organic polymers (namely, SLEL-1 and SLEL-2) with alkyl chains were constructed through Schiff-base reactions to adsorb LEV from an aqueous solution, in which the kinetics, isotherms, influenced factors were investigated. Plausible adsorption mechanisms were proposed through characterization and experimental analysis, including pore filling effect, π-π electron-donor-acceptor (EDA) interaction, hydrogen bonding force, hydrophobic-hydrophobic interaction as well as electrostatic force. In addition, response surface methodology (RSM) revealed the treatment optimization and reciprocal relationship within multi-variables. Furthermore, taking advantage of favorable dispersion and outstanding competitive behavior, SLEL-1 was established as an in-situ adsorptive agent in dynamic saturated columns on a laboratory scale to investigate the removal of LEV from water-bearing stratum. Overall, the findings of this work provided an insight into the fabrication of SLELs as long-term mobile and reusable adsorptive agents for practical in-situ applications in the future.