(641d) Investigating the Photocatalytic Performance of Rapid Settling Pnipam-Titania Microcomposites

Novel composites were prepared that were composed of titania (TiO2) nanoparticles embedded within cross-linked microgels of poly(N-isopropylacrylamide). Interpenetrating linear chains of poly(acrylic acid) were used to functionalize the nanoparticles of TiO2 for dispersal within the porous framework of the stimuli responsive microgels. The microcomposite particles showed rapid sedimentation, which is useful for the gravity separation of these particles in applications such as environmental remediation via photocatalytic degradation. The settling behavior of microcomposites was studied optically using turbidity measurenets. The settling of the polymer?titania composites occurred over minutes and was much faster than solid, impermeable spheres. As the content of TiO2 increased within the particles from 10wt% to 75wt%, the increased effective particle density led to significant decrease in the settling time. A simple mathematical model was used to interpret the optical measurements in terms of the distribution of settling velocities of the particles. These microcomposites were also very photocatalytically active and the degradation kinetics in aqueous solutions was investigated using methyl orange as a model contaminant. Kinetics of the photodegradation was evaluated by monitoring the decline in the methyl orange concentration using UV-Vis spectroscopy. Degradation of methyl orange using freely suspended titania (DegussaTM P25) was also conducted for comparison with the composites. The results reported here are a necessary input for the development of processes that could utilize composites for photocatalysis.