Use of modified flotation cell as ozonation reactor to minimize mass transfer limitations

Abstract

A novel approach based on high turbulence zones to minimize mass transfer limitation in ozonation and catalytic ozonation processes was investigated. A modified flotation cell (MFC), was used as a reactor because this device is widely used for application where three phases (solid-liquid-gas) must interact. Hydrodynamic parameters such as stirring rate, bubbles production and ozone dispersion were evaluated as well as the catalyst load, ozone mass flow, and catalyst reuse. The results show that by increasing the stirring rate in MCF, the ozone mass transfer coefficient enhanced. Under the best operating condition, complete caffeine degradation and mineralization of 57% is achieved in 20 min. It was demonstrated that the kinetic regime of ozonation for caffeine degradation in MFC was moderated, whereas in other reactors, this kinetic regimen is diffusional and even very slow. The ozone bubbles produced and dispersed have diameters between 1.32 and 1.98 mm. It was identified by using the scavenger that hydroxyl radical is generated in catalytic ozonation, and it is a key species for caffeine degradation and mineralization.