Novel sea buckthorn biocarbon SBC@β-FeOOH composites: Efficient removal of doxycycline in aqueous solution in a fixed-bed through synergistic adsorption and heterogeneous Fenton-like reaction

Akaganeite (β-FeOOH) nanoparticles were successfully anchored on the surface of porous sea buckthorn biocarbon (SBC) via a simple low-temperature hydrothermal process without use of surfactants or external forces. The SBC@β-FeOOH composite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). On the basis of characterization methods, a possible mechanism of formation of the SBC@β-FeOOH composite was discussed. The SBC@β-FeOOH composite was used in fixed-bed columns for the effective removal of doxycycline (DC) from an aqueous solution, by the synergistic effect of adsorption and subsequent Fenton-like oxidation reaction, which oxidized the sorbed DC. The effects of inlet DC concentration (22-32 mg/L) feed flow rate (1-3 mL/min) SBC@β-FeOOH bed depth (0.7-1.5 cm) and pH (2-11) on the adsorption breakthrough profiles were investigated. The adsorption process was controlled by the ionic speciation of the adsorbate DC and the available binding sites of SBC@β-FeOOH. It was simulated by the Thomas and Yoon-Nelson models under different conditions. The bed of SBC@β-FeOOH saturated with DC was readily regenerated, in situ, by a heterogeneous Fenton-like oxidation reaction. The synergistic effect resulting from the biosorption nature of SBC and the catalytic oxidation properties of the supported β-FeOOH nanoparticles results in a new promising composite material for water treatment and purification.