Strategies for regeneration of copper(0)-deposited TiO2 photocatalytic film

The treatment of the simulated wastewater containing formic acid and Cu(II) ions was investigated using photocatalytic technology of immobilized TiO2 film. The technology could efficiently remove COD and Cu(II) from the solution. In parallel, a rapid deactivation for COD removal was observed in a successive batch experiment. By XRD, UV-Vis diffuse reflectance spectra, SEM image and TG analysis, it was inferred that the deactivation was attributed to the shield of the deposited Cu(0) from UV light. The Cu(0)-fouled TiO2 film could be regenerated using three kinds of methods, air oxidation, electrochemical oxidation and air-assisted electrochemical oxidation. The regeneration time was mainly dependent on the used regeneration strategy while the regeneration extent was obviously associated with the tested regeneration medium. For the deactivated film with a relative activity of about 20%, the regeneration time is in order air-assisted electrochemical oxidation < electrochemical oxidation < air oxidation, and HNO3 medium has a regeneration extent of 97.2% for the air-assisted electrochemical oxidation, more desirable than HCl and H2SO4 mediums.