Evaluation of an ozone diffusion process using a hollow fiber membrane contactor

• Membrane contactors are interesting devices for ozonation processes. • K L a value depends mainly on the liquid flow conditions. • Ozone concentration and liquid flowrate have a major impact on the ozone transfer. • Membrane contactors are efficient for organic pollutant ozonation. • Membrane contactors can be efficient even at very short contact times. Conventional ozonation processes efficiently remove micropollutants in water treatment, but uncontrolled ozone dosing can produce problematic by-products. Bubbleless operation could help overcome this hurdle. To evaluate this alternative, ozonation was carried out using a polytetrafluoroethylene (PTFE) hollow fiber membrane contactor. The objective was to conduct an extensive characterization of the ozone transfer in an in/out configuration. The overall mass transfer coefficient K L a was determined and was higher than in bubble columns. The transfer resistance due to the membrane was estimated to be lower than 1%. The impact of several variables (liquid flowrate, gas flowrate, and ozone concentration) on the ozone transfer was studied. Ozone concentration was the variable that most increased ozone transfer, followed by the liquid flowrate and then to a lesser extent the gas flowrate. The impact of the presence of a reaction in the water was also evaluated using an organic dye (Acid Orange 7). The Hatta number and the acceleration factor were calculated, corresponding to a reaction that took place partially in the liquid film and in the liquid bulk. Finally, the impact of ozone on membrane material over time was evaluated.