Enhanced photodecomposition of methylene blue in water with Sr1−xKxTiO3−δ@PC-polyHIPEs under UV and visible light

© 2018 Yonghua Gao et al. Photocatalytic method was investigated to remove water pollutant methylene blue (MB) produced in textile, plastic, and dye industries. PC-polyHIPEs were prepared by light-induced polymerization of dopamine in transparent polyHIPEs which were synthesized by polymerization within high internal phase emulsions. Sr1-xKxTiO3-δ (x = 0-0.5) nanoparticles were incorporated and adhered to PC-polyHIPEs to form Sr1-xKxTiO3-δ@PC-polyHIPEs for the first time. The catalysts were characterized by XRD, FTIR, TGA, UV-Vis DRS, and SEM and their photocatalytic properties for MB decomposition were measured over UV-Vis spectrometer. The PC-polyHIPEs were of interconnected porous structure with around 100 μm pores and 30 μm windows. Sr1-xKxTiO3-δ@PC-polyHIPEs showed excellent MB decomposition activity under either UV or visible light although Sr1-xKxTiO3-δalone worked only under UV light. When x = 0.3, Sr1-xKxTiO3-δ@PC-polyHIPEs showed the highest photocatalytic performance due to the existence of more oxygen vacancies. When the water solution with 50 mg L-1MB and 1.6 gcat. L-1Sr0.7K0.3TiO3-δ@PC-polyHIPEs was exposed to visible light for 160 min at room temperature, 88.3% of MB was decomposed. After being used for eight cycles, 87.6% activity of fresh Sr0.7K0.3TiO3-δ@PC-polyHIPEs still remained. The influences of salinity, temperature, and catalyst concentration on the catalytic activity were studied. For MB decomposition under visible light, the activation energy of Sr0.7K0.3TiO3-δ@PC-polyHIPEs was calculated to be 12.3 kJ mol-1and the kinetics analysis revealed that the photocatalysis followed the second-order reaction. These findings demonstrated that Sr1-xKxTiO3-δ@PC-polyHIPEs were an effective candidate for real application in decomposition of MB in water.