Using PLIF/PIV techniques to investigate the reactive mixing in stirred tank reactors with Rushton and pitched blade turbines

•Reaction progress of a turbulent reactive mixing process is quantified in a stirred reactor.•Laser induced fluorescence and particle image velocimetry techniques are employed.•A criterion is developed for determining the reaction progress based on the reactor mixed pixels.•Impeller type, clearance, and feeding location significantly alter concentration profiles.•System performance is controlled by macromixing in the tank.