Facile fabrication of sea buckthorn biocarbon (SB)@α-Fe2O3 composite catalysts and their applications for adsorptive removal of doxycycline wastewater through a cohesive heterogeneous Fenton-like regeneration

Abstract

A facile, low-cost and novel route for successful synthesis of SB@α-Fe₂O₃ composite catalysts was described through a simple thermal conversion process from SB@β-FeOOH precursor. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and Fourier transformed infrared spectroscopy (FTIR) analysis, respectively. The experimental results indicated that α-Fe₂O₃ phase nanoparticles in the SB@α-Fe₂O₃ composites appeared in spindly nanorods and were highly dispersed on the surface of sea buckthorn biocarbon (SB) platform. The mechanism of thermal conversion from SB@β-FeOOH precursor to SB@α-Fe₂O₃ products was discussed. Subsequently, the naked SB and resultant SB@α-Fe₂O₃ composites were applied in fixed-bed columns for the effective pre-adsorption of doxycycline (DO) from an aqueous solution. Breakthrough curves for DO adsorption were carried out at different empty bed contact times (EBCTs). The results showed that the adsorption capacity of SB@α-Fe₂O₃ was much better than that of SB at all tested EBCTs. The DO-saturated SB@α-Fe₂O₃ bed was almost completely regenerated in situ through triggering a succedent heterogeneous Fenton-like regeneration process with an H₂O₂ dose of 1% w/v for 3 h, while the naked SB was hardly regenerated by a parallel processes. In view of the facile synthetic method of composites, the superior adsorption performance and the effective way of regeneration for consecutive pre-adsorption/regeneration cycles, the heterogeneous Fenton-like oxidation of DO-exhausted SB@α-Fe₂O₃ presents to be a promising and viable strategy for the regeneration of adsorbent. Regeneration mechanism of SB@α-Fe₂O₃ was in-depth investigated.