Comparative insights into performance and mechanisms of Fenton and persulfate oxidation on iron-functionalized activated biochar for removal of aqueous tetracycline antibiotics

In this work, a novel iron-functionalized activated biochar (FA-BC) was applied for adsorption and regeneration with Fenton and persulfate (PS) oxidation to effectively remove tetracycline (TC) in wastewater and water. FA-BC exhibited an excellent TC adsorption capacity (69.39 mg/g) via surface complexation, hydrogen bonding, and π-π EDA interaction. Fenton oxidation exhibited high regeneration efficiency for TC-spent FA-BC at only pH 3, while PS oxidation effectively regenerated the TC-spent FA-BC at pH 3–8. Increasing the temperature from 20 to 50 °C enhanced the regeneration performance with Fenton oxidation, while decreasing with PS oxidation. In addition, increasing the temperature from 20 to 50 °C led to the enhancement of TC diffusion, H2O2 and PS reaction rates by the factors of 2.20, 1.58, and 4.07. HO· and SO4.− radicals would mainly participate in the regeneration of TC-spent FA-BC via Fenton and PS oxidation, respectively, while both radicals could oxidize the TC molecules which were desorbed from TC-spent FA-BC and diffused from the interior to exterior of FA-BC. Under the optimal conditions, Fenton and PS oxidation effectively regenerated the TC-spent FA-BC with regeneration efficiencies of 99.41 % and 99.24 %. Moreover, both fresh and regenerated FA-BCs also effectively removed TC (>99 % removal efficiency) in water at environmentally relevant concentrations. Adsorption/Fenton oxidation and adsorption/PS oxidation using FA-BC were also applied to treat TC from a real dairy wastewater, achieving the regeneration efficiencies of 94.99 % and 93.36 %. Thus, this study indicated great potential for application of FA-BC in TC treatment from water and wastewater. [Display omitted] •Iron-functionalized activated biochar (FA-BC) was applied for TC adsorption.•TC spent FA-BC was effectively regenerated by Fenton and persulfate (PS) oxidation.•PS oxidation was applicable at wider pH ranges than Fenton oxidation.•TC diffusion significantly affected the regeneration of TC-spent FA-BC.•Adsorption-Fenton/PS regeneration by FA-BC can remove TC in dairy wastewater.