Control of copper element in mesoporous iron oxide photocatalysts towards UV light-assisted superfast mineralization of isopropyl alcohol with peroxydisulfate

Abstract

Isopropyl alcohol (IPA) is one of the most commonly used solvents, and the development of superfast and environmentally-benign mineralization process for IPA-contaminated water is highly required in semiconducting manufacturing industry. Herein, mesoporous copper-doped iron oxide catalysts with a different copper content (Cu(x)-Fe2O3) were simply prepared by the thermal treatment process where the precipitate formed by the complexation of metal precursors with an oxalic acid was calcined at 400 °C. According to various characterizations, it was confirmed that the elemental copper was homogeneously dispersed over the surface of Fe2O3. Under UV light irradiation only, the activation of peroxydisulfate (PDS) itself generated radical species, and the complete mineralization of IPA to carbon dioxide (CO2) was proceeded with moderate kinetics. However, the introduction of Cu-Fe2O3 catalysts accelerated the reaction kinetics, and the decomposition of IPA (10 ppm) and its full mineralization to CO2 were completed within 1 and 30 min, respectively, for the optimized sample (i.e., Cu(0.5)-Fe2O3). The radical scavenging test and electron paramagnetic resonance (EPR) measurement revealed that both sulfate and hydroxyl radicals (SO4− and OH) were generated in terms of UV-photolysis of PDS plus PDS activation by Cu-Fe2O3 photocatalyst. The electrochemical studies clarified that the doping of copper decreased the recombination of electron-hole pairs and facilitated the interfacial charge transfer. Furthermore, the freestanding film immobilizing Cu-Fe2O3 fabricated by an electrospinning method showed a similar catalytic performance compared with that of the powder-type system. The strategy to fulfill a facile synthesis of active catalysts towards the rapid mineralization of IPA will help to advance practical applications in semiconductor industries where processing time and cost are crucial.