Keywords: photoelectrocatalysis, advanced oxidation processes, titanium dioxide, 4-nitrophenol, e coli, photochemical disinfection, humic acids, water treatment, UV penetration, mass transfer, electrode fouling
Photoelectrocatalysis by titanium dioxide for water treatment
This paper reviews the potential advantages of photoelectrocatalytic treatment of water and considers three general problems – UV penetration, mass transfer and electrode fouling – associated with the practical application of photoelectrocatalytic treatment of water. The three systems selected for these studies, representative of a broad range of possible pollutants, were aqueous solutions of 4-nitrophenol, water inoculated with E. coli, and water with naturally occurring humic acids. Nitrophenol solutions were of particular interest because of the challenges associated with a complex, multi-step degradation process and with UV penetration of water contaminated with substituted aromatic compounds. Possible mass transfer limitations were considered for the nitrophenol solution and also for E. coli suspensions. Electrode fouling was considered in the context of nitrophenol oxidation and humic acid oxidation, whilst the effect of poisoning was investigated by comparing of the effect of phosphate on a) photocatalytic; b) photoelectrocatalytic disinfection of E. coli suspensions. Where appropriate, the results from photoelectrocatalysis were compared with those from photocatalysis under the same conditions.