Ozonation of Phenol with O3/Fe(II) in Acidic Environment in a Rotating Packed Bed

The treatment of acidic phenolic wastewater by ferrous-catalyzed ozonation (O3/Fe(II)) process in a rotating packed bed (RPB) was studied, and the O3/Fe(II) process was compared with the O3 process. It was observed that the phenol degradation rate in the O3/Fe(II) process was roughly 10% higher than that of O3 process in acidic environment in the RPB. It is also found that the degradation efficiency of phenol was significantly affected by the rotation speed and inlet ozone concentration. Phenol degradation efficiency increased with increasing initial pH of the phenolic solution, rotation speed, and concentrations of the inlet ozone gas, as well as a decreasing liquid flow rate and initial concentrations of phenol. Phenol degradation efficiency reached maximum at a temperature of 25 °C and an initial Fe(II) concentration of 0.4 mM. The result of the contrast experiment showed that the biological oxygen demand/chemical oxygen demand (BOD/COD) of the phenol solution increased from 0.2 to 0.59 after the solution was treated by O3/Fe(II) process. The intermediates of the ferrous-catalyzed ozonation process were identified by gas chromatography/mass spectroscopy (GC/MS), and it is deduced that the pathway of phenol degradation in ferrous-catalyzed ozonation is different from that in ozonation. Hydroquinone and 1,4-benzoquinone were the main intermediates, and a small amount of polymeric intermediates was found in the O3/Fe(II) process.