BACKGROUND: Sulfadiazine (SD), a widely used antibiotic chemical, has been detected in contaminated water and soils. Manganese dioxides are common minerals with a high redox potential and can act as active oxidants for SD degradation in wastewater treatment. RESULTS: alpha-MnO2 was used to promote SD oxidative degradation. At pH 4.6 and 25 degrees C, 92.7% of SD (0.02 mmol L-1) was degraded by 1.0 g L-1 alpha-MnO2. SO42- was detected as the inorganic end product from the mineralization of SD. The ecological toxicity index of average well color development (AWCD) in SD solution was 2.01 after the solution was degraded by alpha-MnO2 for 2 h, while the AWCD was 0.48 for the solution without alpha-MnO2 treatment. The degradation rate of SD can be improved by increasing the dosages of alpha-MnO2 and the reaction temperature, but the rate was limited by increased initial SD concentration and reaction pH. CONCLUSION: SD can be effectively degraded and mineralized with alpha-MnO2. These results are helpful for removing antibiotics by manganese dioxides in the environment, and also for exploring new technology for wastewater treatment. (C) 2009 Society of Chemical Industry