Synthesis of sponge-loaded Bi₂WO₆/ZnFe₂O₄ magnetic photocatalyst and application in continuous flow photocatalytic reactor

The magnetic photocatalyst Bi₂WO₆/ZnFe₂O₄ was loaded on the surface of polyurethane sponge with polyvinyl butyral (PVB) as an immobilizing agent. The as-prepared photocatalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and element mapping. The best operating conditions of the reactor were determined to be 0.10 wt% PVB, mass ratio of sponge to catalyst = 1:1.25, volume ratio of sponge to mixture = 8 g/L and load temperature at 80 °C. The average load rate of the photocatalyst was 56.18%. The photodegradation ratio of tetracycline hydrochloride (TCH, 50 mg/L) was above 98.35% with the load of 5 g/L photocatalyst within 90 min under visible-light irradiation. The best conditions were photocatalyst quantity = 6 g/L, light source intensity = 140000 lux and pollutant concentration = 50 mg/L. The TCH photodegradation ratio reached 91.59%. The addition of PVB increased the fall-off of the photocatalyst and the magnetism of photocatalyst facilitated the recovery. The photocatalyst fall-off rate was 2.53%, and the fall-off part of the powder photocatalyst was adsorbed by magnet, and the recovery rate was 95.13%.