determination and toxicity evaluation of the generated byproducts from sulfamethazine degradation during catalytic oxidation process sulfamethazine smz a kind of sulfonamide antibiotics can exist for a long periods of time and has been widely detected in the environment which could pose a potential health threat to human beings in this study sludgederived carbon sc catalyst was modified and applied to degrade smz during catalytic oxidation process degradation products and possible transformation pathways were investigated based on data of gcms the toxicity evolution of smz degradation after catalytic oxidation process was tested with zebrafish and microbial degradation respirometer as a consequence sc modified with nitric acid schno3 exhibited highly catalytic efficiency reached 922 smz conversion and 752 total organic carbon toc removal rate after 480min ten kinds of possible products were identified by gcms during degradation process of smz indicating two possible pathways no pronounced malformation was observed in the toxicity experiments with zebrafish until 120h post fertilization hpf however further analysis showed that zebrafish incubated with smz solution had higher mortality lower hatching rate slower spontaneous movement and shorter body length compared with the group used normal nutrient solution while the water after treatment had lower toxicity effects on zebrafish the toxicity experiments with microbial degradation respirometer showed that smz solution had lower value of oxygen uptake which indicated that smz solution had higher values of toxicity and inhibition of pharmaceutical compounds this study provides a catalyst with low cost and high catalytic efficiency for degradation process of smz and gives a deeper insight into the ecotoxicity of treated water