BACKGROUNDDecoloration of dyes is a top priority to enhance biodegradability in color-free wastewater post-treatment. A gas-liquid dielectric barrier discharge (DBD) falling film reactor has been developed as a promising approach to the decoloration of dyes. RESULTSRhodamine B was employed as a model compound. The effects of residence time of the liquid film with different initial concentrations, oxygen flow rates and oxygen concentrations (using different diluent gases, e.g. argon and nitrogen) were investigated. Longer liquid film residence time and lower oxygen flow rate resulted in higher decoloration efficiency. The decoloration efficiency in oxygen and nitrogen discharge was slightly higher than that in oxygen and argon discharge at the same oxygen concentration. The mechanisms of decoloration and the production of oxidative species are clearly revealed. The highest decoloration efficiency (up to 97.4%) with initial concentration of 50mgL(-1) was obtained in pure oxygen discharge with liquid residence time of 1.9s at an oxygen flow rate of 100 mL min(-1). CONCLUSIONThe proposed gas-liquid DBD falling film reactor is a promising alternative to advanced oxidation processes (AOPs) for effective treatment of dyes. These results are helpful for further real plasma wastewater treatment. (c) 2014 Society of Chemical Industry