Fabrication of poly(vinyl alcohol)/sodium alginate hydrogel beads and its application in photo-Fenton degradation of tetracycline

Developing a reusable and durable catalyst for heterogeneous photo-Fenton process is of great importance for the practical application in the environment remediation. In this study, poly(vinyl alcohol) (PVA)/sodium alginate (SA) hydrogel beads were constructed using FeCl3 and boric acid as cross-linking agents. Characterizations and tests were employed to investigate the structure, optical property and durability of the obtained beads. The photo-Fenton performance of the PVA/SA-FeCl3 beads was evaluated by degradation of tetracycline (TC) under visible-light irradiation. The results show that the constructed beads exhibit porous structure, display a broad absorption band in the visible region and behave excellent stability against mechanic effects. The photocatalytic experiment result indicates that the removal rate of TC reaches 90.5% under optimized conditions, while the removal rate of total organic carbon reaches 28.6%. By analyzing the degradation of TC after adding active species scavengers, a photocatalytic mechanism was proposed. Moreover, PVA/SA-6% FeCl3 beads could be easily separated and recycled in water purification. This work provides a facile and robust method to construct reusable and durable Fe(III)-containing hydrogel beads with acceptable photo-Fenton catalytic performance under visible-light irradiation, paving the way for its practical application in wastewater treatment.