Green approach for photocatalytic Cu(II)-EDTA degradation over TiO2: toward environmental sustainability.

A green approach was successfully developed to reap three environmental benefits simultaneously: (1) clean water production, (2) hydrogen (H2) generation, and (3) well-dispersed in situ Cu(2+) recovery for direct TiO2-CuO composite reclamation, by exploiting the synergistic integration of photocatalytic reaction of Cu-EDTA and one-dimensional (1D) ultralong and ultrathin TiO2 nanofibers. In this light-initiated system, Cu-EDTA was oxidized by TiO2 thus releasing Cu(2+) which was reduced and recovered through uniform adsorption onto the long and porous TiO2 surface. A win-win platform was thus attained, on which Cu was recovered while providing active sites for H2 generation via photoreduction of H2O and enhancing photo-oxidation of remaining intermediate oxidation byproducts. Experimental results showed a H2 generation rate of 251 μmol/h concomitantly with TOC reduction. The used TiO2 nanofibers deposited with Cu were reclaimed directly as the TiO2-CuO composite after a facile heat treatment without additional chemicals and subsequently reusable for photocatalytic treatment of other wastewater (glycerol) to cogenerate H2 and clean water under both UV-visible and visible light. This study expounds a significant advancement through an ingenious integration which enhances the environmental sustainability of Cu-EDTA treatment via TiO2 photocatalysis. It also represents a promising and adoptable approach to synthesize other functional composite nanomaterials in a green manner thus broadening its environmental application spectrum, as it promotes industrial environmental management via waste segregation and motivates research to recover more resources from wastewater.