The　recalcitrant　nature　of　sulfonamide　antibiotics　in　aquatic　systems　poses　significant　risks　to　both　ecological　stability　and　public　health　due　to　persistent　bioaccumulation　and　the　promotion　of　antimicrobial　resistance.　To　address　these　challenges,　magnetic　ZnFe2O4　was　synthesized　via　a　urea-assisted　solvothermal　strategy,　followed　by　controlled　interfacial　deposition　of　Bi2S3　to　construct　a　ZnFe2O4/Bi2S3　heterojunction　with　enhanced　charge　separation　efficiency.　The　composite　exhibited　strong　visible-light　responsiveness　and　high　sodium　percarbonate　(SPC)　activation　capability.　Under　visible　light,　the　heterojunction-activated　SPC　achieved　high-degree　mineralization　of　sulfadiazine　(SDZ)　within　60　min,　with　a　synergy　factor　of　2.64.　Quenching　experiments　and　in　situ　electron　spin　resonance　(ESR)　spectroscopy　identified　hydroxyl　radicals　(·OH)　and　superoxide　radicals　(·O2−)　as　the　predominant　reactive　oxygen　species,　contributing　94.7　%　and　78.3　%,　respectively,　while　singlet　oxygen　(1O2)　and　carbonate　radicals　(·CO3−)　showed　minimal　contributions　of　3.6　%　and　1.6　%.　Density　functional　theory　(DFT)　and　Fukui　function　analysis　identified　susceptible　C,　N,　and　S　atoms　in　SDZ,　while　LC-MS　detected　12　key　transformation　products　and　three　degradation　pathways,　elucidating　its　molecular　fragmentation　mechanism.　Ecotoxicity　evaluation　confirmed　reduced　toxicity　of　SDZ　and　intermediates,　supporting　environmental　applicability.　Overall,　the　ZnFe2O4/Bi2S3　heterojunction　enabled　efficient　antibiotic　elimination　with　mechanistic　insight　and　practical　value　for　sustainable　water　treatment.　©　2025