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

Abstract

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 (22–32mg/L) feed flow rate (1–3mL/min) SBC@β-FeOOH bed depth (0.7–1.5cm) 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.