Mitigation of levofloxacin from aqueous media by adsorption: a review

Levofloxacin (LEV) is an antibiotic that has a negative ecotoxicological effect. Its mitigation from the aqueous environment is achievable by adsorption. The aim of this paper was to review the removal of LEV from aqueous media via adsorption. The goal was to carefully study the trends of research findings by various authors over the past two decades, analysing key results, observing trends and similarities and identifying interesting areas that future researchers should consider. It was observed that modified carbon-based adsorbents are the best class of adsorbent for LEV uptake. The highest reported adsorption capacity for LEV is 1111 mg/g for corncob–Ag NPs composite adsorbent. This was the only adsorbent that could remove more than its weight of LEV. The major mechanisms of uptake of LEV are π–π interactions, electrostatic interactions, complexation and hydrogen bonds. The Langmuir or Freundlich classical isotherm model was the best fit in most cases to describe the adsorption equilibrium. LEV is easily desorbed from various adsorbents, It possesses a desorption rate > 60% after the first regeneration cycle. Also, > 20% retention of original adsorption capacity can still be achieved after about 5 cycles. The uptake of LEV is seriously hampered (20–60% decrease) by salt competing species in the aqueous phase. Interesting areas for future research identified were the choice of eluent for desorption, the choice of competing species, and statistical physics modelling.