TiO2/Ti rotating disk photoelectrocatalytic (PEC) reactor: a combination of highly effective thin-film PEC and conventional PEC processes on a single electrode.

A TiO2/Ti rotating disk photoelectrocatalytic (PEC) reactor has been developed and successfully applied to degrade Rhodamine B (RB) and other dyes in textile effluents. The innovative concept behind the reactor design is to simultaneously perform two processes on one electrode. These two processes are (1) highly effective thin-film PEC, in which the upper half of the round disk photoanode was coated with a thin layer of wastewater and exposed to UV radiation in air; and (2) the conventional PEC, in which the other half of the disk was immersed in bulk wastewater and irradiated by the same light source. The average aqueous film thickness was about 75 microm. The disk electrode was kept rotating at 90 rpm to continuously refresh the thin aqueous film for the upper side of the electrode and to promote the mass transfer of the target pollutants and the degradation products on the lower part of the disk. Using 20-150 mg L(-1) RB solutions as a model system, thin-film PEC removed total color and total organic carbon (TOC) by 27-84% and 7-48%, respectively, within 1 h, much higher than 3-55% and 0-30% removal by conventional PEC under the same treatment conditions. Results also suggest that the thin-film process was especially superior for treating high concentration solutions. Application of the rotating disk PEC reactor in industrial textile effluents showed a satisfactory result. The recycle experiments demonstrated excellent stability and reliability of the rotating disk PEC electrode. This study proposed a new concept for designing a PEC reactor applicable to industrial wastewater treatment.