Ag2CrO4-NiO/g-C3N4 heterostructured nanocomposites as efficient visible-light-responsive materials for rapid degradation of persistent antimicrobial residues

• A g-C 3 N 4 -based photocatalyst from the infusion of Ag 2 CrO 4 –NiO heterostructure. • AN-20/g-C 3 N 4 photocatalyst revealed high durability and visible-light response. • Ofloxacin degradation was optimized by tuning crucial analytical parameters. • A Z-scheme catalytic pathway involving reactive oxygen species was elucidated. This study presents a strategic approach for designing a highly efficient, visible-light-responsive photocatalyst by integrating a novel Ag 2 CrO 4 -NiO (AN) heterojunction into a porous graphitic carbon nitride (g-C 3 N 4 ) sheet scaffold. The optimized composition, i.e., 20%Ag 2 CrO 4 and 80%NiO (AN-20), blended with g-C 3 N 4 (AN-20/g-C 3 N 4 ), demonstrates remarkable photocatalytic performance for the rapid degradation of ofloxacin, a widely used fluoroquinolone antibiotic. Comprehensive structural and surface analyses, including p-XRD, FT-IR, FE-SEM-EDX, HR-TEM-SAED, XPS, PLS, EIS, UV-Vis DRS, AFM, TrPL, and BET/BJH, reveal a high surface-area, porous heterostructure that promotes efficient pollutant adsorption and interaction with active sites. The AN-20/g-C 3 N 4 system forms a Z-scheme heterojunction, which enhances visible light absorption, facilitates effective charge carrier separation/transport, and boosts excellent visible-light photocatalytic activity. Scavenging experiments confirm the dominant roles of photogenerated holes (h⁺) and superoxide radicals ( • O 2 ⁻) in the degradation process. Under optimal conditions (15 ppm ofloxacin, pH 5.0, 50 mg photocatalyst, 2.0 mM KBrO 3 sensitizer, 240 W/cm 2 light intensity), the photocatalyst achieves ≥98.5% degradation within 15 min. QSAR-based toxicological assessments of the degradation products using T.E.S.T. software indicate a significant reduction in environmental risk. Additionally, the AN-20/g-C 3 N 4 photocatalyst demonstrates excellent reusability and structural stability, making it a promising candidate for sustainable environmental remediation under challenging operational conditions.