BACKGROUND: Advanced oxidation includes a number of technologies, all of them appropriate to achieve environmental remediation. One of them is the organic compounds degradation by ozonation. The ozonation of rhodamine 6G (R6G) was investigated to study the effect of pH and subsequent predominance of the control stage, whether mass transfer from gas to liquid phase or chemical reaction, during oxidation. Several pH conditions are studied to achieve greater efficiency of the process. RESULTS: A mathematical model enables analysis of the controlling stage. It was satisfactorily verified, showing that, initially, the process is controlled by the G-L mass transfer stage but, as the R6G ozonation progresses the process becomes controlled by the kinetic reaction. While 99% of the rhodamine dye is removed during the mass transfer control stage regardless of the pH value, the percentage of TOC removal is increased only during the kinetic reaction control stage. CONCLUSION: The most favourable pH, given the mass transfer characteristics of this case, was found to be an intermediate value around 6.0 where a minimum value for coefficient for R6G mineralization z(av) of about 23mol O-3 mol(-1) R6G mineralized, and near its theoretical value, was obtained. (c) 2016 Society of Chemical Industry