Ce substituted goethite (Ce0.1Fe0.9OOH) was prepared by isomorphous substitution method and used for the catalytic ozonation of sulfamethazine (SMT). The results showed that acidic and neutral pH is beneficial for SMT mineralization. The mineralization efficiency of SMT was enhanced obviously in the presence of catalyst. Major degradation products of SMT during catalytic ozonation process were quantified and compared at acidic or basic conditions. Among the intermediates, 2-amine-4,6-dimethylpyrimidin accounted for high proportion. The small-molecule organic acids accumulated, which can inhibit the degradation reaction by lowering solution pH value. Based on the competitive degradation results of the intermediates and SMT, the possible pathways for SMT degradation by catalytic ozonation were tentatively proposed. (C) 2016 Elsevier B.V. All rights reserved.