Photoreduction of Copper Ions Using Silica-Surfactant Hybrid and Titanium (IV) Oxide under Sulfuric Acid Conditions.

Photoreduction of Cu 2+ ions to Cu metal by titanium(IV) oxide (TiO 2 ) was conducted in the presence of a silica-surfactant hybrid under sulfuric acid conditions. After irradiation, a dark-red color, reflections due to Cu metal in the X-ray diffraction pattern, and peaks due to Cu 2 p 1/2 and 2 p 3/2 in the X-ray photoelectron spectrum indicated the precipitation of Cu metal in the product. In addition, an increase in the Brunauer-Emmett-Teller specific surface area from 36 and 45 m 2 /g for the silica-surfactant and TiO 2 , respectively, to 591 m 2 /g for the product, and a decrease in the intensity of the C-H stretching band in the Fourier-transform infra-red spectra implied the removal of surfactant during the reaction. These characteristics were never observed when TiO 2 was used solely. Therefore, this study indicated that the photoreduction of Cu 2+ ions to Cu metal by TiO 2 was facilitated under the sulfuric acid medium, where the surfactants extracted from silica-surfactant hybrids by protons in the acidic condition were successfully photo-oxidized by TiO 2 . Thus, this study presents a new application of the conversion of a silica-surfactant hybrid into mesoporous silicas.