In this research, photocatalytic degradation of acesulfame K, one of the most popular artificial sweeteners, has been carried out under variations of the initial concentration, pH, concentration of persulfate, and amount of natural organic matter (NOM). The removal efficiencies for 30-min, 60-min and 180-min reaction time have been applied to response surface methodology using the experimental responses obtained by a four-factor-three-level Box-Behnken design (BBD). This provided 29 experimental data for the initial concentration of acesulfame K ranging from 300 to 900 mu g/L, pH of solution ranging from 4 to 10, persulfate concentration ranging from 0 to 10 mg/L, and amount of natural organic matter (NOM) ranging from 0 to 5 mg/L, which were consecutively coded as A, B, C, and D at three levels (-1, 0, and 1). The analysis of variance (ANOVA) tests with 95% confidence limits determined the significance of independent variables and their interactions consisting of the polynomial regression equation. The optimum values of the selected variables were determined by numerical optimization, and the experimental conditions were found to reach complete mineralization for 30 min and thereafter, at initial concentration of 887.2 mu g/L; pH of 4; persulfate concentration of 9 mg/L, and NOM concentration of 5 mg/L. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.