Intensified water denitrification by means of a spinning disk reactor and stirred tank in series. Kinetic modelling and computational fluid dynamics

The aim of this work was to investigate the performances of a spinning disk reactor for the removal of nitrate from aqueous solutions, by using iron nanoparticles as reducing agent. The influence of three operating parameters, i.e. rotational velocity, feed injection point position and recirculation flow-rate was investigated through evaluating the nitrate reduction efficiency and kinetics. Increasing the rotational velocity led to a better nitrate reduction efficiency and faster kinetics. The optimal rotational velocity was 147 rad/s, whereas the optimal feed injection point distance from disk centre and recirculation flow-rate were 3 cm and 250 ml/min, respectively. The data were compared with those reported in literature and obtained by classical batch reactor and clearly demonstrated the better performances obtained by this intensified equipment. Finally, a mass transfer based kinetic model was proposed, and a computational fluid dynamic model was implemented to simulate the fluid dynamics of the rotating liquid film.