A comparative study of TiO2 nanoparticles and Cu(II)/TiO2 nanocomposites on photodegradation of cinnamic acid (CA) under natural sunlight and artificial UV light

Surfaces of TiO2 nanoparticles decorated with Cu(II) nanoparticles as Cu(II)/TiO2 nanocomposites, were prepared via a grafting process for a comparative study on photodegradation of recalcitrant cinnamic acid (CA) in aqueous solutions. In this study, CA was used as a model representing for the wastewater from agricultural industries containing phenolic compounds. Photodegradation of CA in the solutions by TiO2 nanoparticles and Cu(II)/TiO2 nanocomposites under natural sunlight and artificial UV light, were investigated. CA concentrations in the solutions were determined from the highest peak intensities at 271 nm, detected by a UV-Vis spectrophotometer. Under 90 min of the irradiation of both light sources, CA concentrations in the solutions were degraded by Cu(II)/TiO2 nanocomposites higher and quicker than those of TiO2 nanoparticles. According to the reusability test results, both TiO2 nanoparticles and Cu(II)/TiO2 nanocomposites have potential to reuse at least three cycles. Intermediate compounds formed during the irradiation of UV light, were identified by XPS analysis confirming that CA gradually changed to be nontoxic compounds. A mechanism for the CA photodegradation pathways in the solutions by Cu(II)/TiO2 nanocomposites was proposed according to the analysis.