This study explores the experimental determination of the mass transfer rate of ozone in a planar falling film reactor at a wavy-laminar flow regime and provides empirical models for predicting the liquid side mass transfer coefficient, K-L, of ozone in the semi-batch and continuous processes. The obtained results show that increasing the superficial gas velocity, U-G, and the liquid Reynolds number (60 <= Re-L <= 240) enhance the K-L of ozone in both the semi-batch and continuous processes. While in the semi-batch process the U-G has the predominant impact on the K-L, in the continuous process the liquid Re-L governs the mass transfer rate of ozone. Based on these findings, empirical models for predicting the K-L as a function of Re-L and U-G in the semi-batch and continuous processes are developed. Comparing the experimental and the calculated K-L values showed that the values calculated by the models match well (R-2 > 0.99) with the experimental values. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.