Optimization of the photocatalyst coating and operating conditions in an intimately coupled photocatalysis and biodegradation reactor: Towards stable and efficient performance

Intimately coupled photocatalysis and biodegradation (ICPB) is an attractive novel technology for the mineralization and detoxification of persistent organics. Good photocatalytic performance is essential for an advanced ICPB operation, and the photocatalyst coating and illumination conditions are strong determining factors. In this work, response surface methodology (RSM) involving the central composite design (CCD) was employed to discover optimal operating conditions, by using tetracycline hydrochloride (TCH) as the model pollutant. Polyvinyl butyral (PVB) was employed to form an adhesion layer, enhancing P25 TiO2 activity and stability. We achieved the optimal coating conditions with a mixing time of 20 h, TiO2 dosage of 8 g/L, and PVB concentration of 0.5 wt.%. The optimum running conditions for an ICPB-reactor were found to be at a carrier volume ratio of 40% and light intensity of 6000 μw/cm2. These conditions were essential for the production of desired intermediates and functional microbial survival. At the optimized parameters ranges, ∼98% TCH removal and ∼40% mineralization was achieved, and the inhibition on Q67 illuminance was only 30.32%. This is the first work on optimizing the fabrication and operation of ICPB, which is meaningful for the application of ICPB in practical engineering.