Photocatalytic and photoelectrocatalytic degradation of small biological compounds: A case study of uridine

Photocatalytic (PC) and photoelectrocatalytic (PEC) degradation of small hazardous biological compounds was accomplished by using uridine as a model compound. The net charge transfer (Qnet) originated from PEC degradation of uridine and blank charge transfer (Qblank) due to photocatalytic oxidation of water remained constant when the light intensity increased from 20 to 40 mW/cm2. The effect of solution pH on Qnet and Qblank showed that the suitable pH range for this proposed analytical application is between 4 and 9. For both PC and PEC, an increase in the uridine concentration within low concentration range led to a rapid decrease in the mineralization percentage for converting organic nitrogens to both NH3/NH4+ and NO3−. With further increase of uridine concentration to 320 μM, the PEC mineralization percentages maintained at about 85% and 56% for N oxidized to NH3 and NO3−, respectively. While for PC treatment, the mineralization percentages decreased steadily. Finally, PC and PEC degradation mechanism of uridine was also clarified on the basis of intermediates identified by HPLC/MS/MS and frontier electron densities calculation. Uridine as well as the intermediates can be eventually mineralized into CO2, H2O and NH3 or NO3− (or both) during PC and PEC degradation with enough reaction time.