Adsorption of doxycycline from aqueous media: A review

The aim of this review was to examine the adsorption of doxycycline (DC) from aqueous media. The review investigated the performance of various adsorbents, analysed the adsorption mechanism, and discussed the isotherm, kinetics, thermodynamics and other aspects of the adsorption process. Furthermore, the purpose of this review was also to identify knowledge gaps and future perspectives in the research area. DC has a proven ecotoxicological risk hence its mitigation from the environment through adsorption is justified. The highest reported adsorption capacity for DC is 835.45 mg/g for hierarchical CoFe2O4/biosilica nanocomposite. The major mechanisms of DC uptake were electrostatic interaction and p-p interactions. DC was uptake was majorly best-fit to the Langmuir and Freundlich isotherm models, and the pseudo-second-order kinetics model. It was observed that DC is readily desorbed from various adsorbents and most of these can have >80% of the initial adsorption capacity retained after 4 cycles. Researchers on DC competitive adsorption have observed the salting-out effect, bridging effect and electrostatic screening effect. From this review, it can be concluded that DC can be efficiently mitigated from industrial effluents and wastewaters by the adsorption techniques. (C) 2021 Elsevier B.V. All rights reserved.