MFO@NZVI/hydrogel for sulfasalazine degradation: Performance, mechanism and degradation pathway

The fabrication of heterogeneous photocatalyst with superior redox capability has been emerged as a prospective strategy for wastewater remediation. In this study, we optimized the conformation of MFO@NZVI/hydrogel photocatalyst, which exhibited superior photocatalytic activity towards sulfasalazine (SFZ), up to 77.88% within 180 min. The effect of diversified influencing parameters on the photodegradation efficiency was systematically investigated. Besides, we conducted XRD, SEM, FT-IR and UV–vis DRS to investigate the structure, morphology and optical properties of MFO@NZVI/hydrogel, respectively. Meanwhile, we tested that the band gaps of photocatalyst were as follow: pure hydrogel (4.51 eV) > MFO@NZVI (3.29 eV) > MFO (2.74 eV) > MFO@NZVI/hydrogel (2.45 eV) > NZVI (1.59 eV). Hence, we suggested that MFO@NZVI/hydrogel could rapidly capture and transport electrons for effective charge separation, promoting the generation of reaction oxygen species (∙O₂^–, ∙OH, h⁺ and ¹O₂) for photocatalytic. Furthermore, a possible mechanism and intermediates for SFZ photodegradation has been elucidated. Moreover, the photodegradation efficiency of MFO@NZVI/hydrogel was 77.68% for SFZ after 9 cycles, contributing to its excellent recovery and stability. Therefore, we demonstrated the feasibility of MFO@NZVI/hydrogel photocatalytic system and provided insight on the design of high-performance photocatalyst for removal process of persistent pollutants.