Photoelectrocatalytic inactivation of E. coli XL-1 blue colonies in water

BACKGROUND: The aim of the present work was the preparation of TiO2 P-25 working electrodes on Ti substrates (TiO2/Ti), their characterization and the study of their photoelectrocatalytic activity towards the inactivation of E. coli XL-1 blue (E. Coli) colonies, used as model pathogenic bacteria, in a novel batch photoelectrochemical reactor. RESULTS: After annealing of the TiO2/Ti specimens at 500 degrees C, the surface morphology and crystal structure of the TiO2 film electrodes were examined by scanning electronic microscopy (SEM) and X-ray diffraction (XRD), while from differential capacitance measurements the flat band potential was calculated (V-fb = -0.54 V versus Ag/AgCl). The results of photoelectrocatalytic (PEC) experiments concerning the disinfection of E. coli colonies were compared with those of electrochemical (EC) and photocatalytic (PC) inactivation of the pathogen and showed a significant synergy effect in the case of PEC disinfection, leading, at +1.0 V vs Ag/AgCl cell voltage, to a 100% increase of the apparent rate constant, k(o), in comparison with the simple photocatalytic process. Reuse experiments showed that the working electrode retains its effectiveness after, at least, 15 times of reuse. CONCLUSIONS: The photoelectrocatalytic inactivation of E. coli colonies has been studied under artificial illumination in a novel photoelectrocatalytic reactor. The inactivation of 10(3) CFU mL(-1) E. coli colonies followed first-order kinetics, while parameters such as type of semiconductor and concentration of the microorganisms play an important role affecting the reaction rate constant. (C) 2010 Society of Chemical Industry