The Photochemistry Of Carbon Nanotubes In Aqueous Solution And Its Impact On The Degradation Of Dye Pollutants

As a new type of functional materials, carbon nanotubes (CNTs) have attracted extensive interests since its discovery. The photochemistry of CNTs is an important property that is related to the transport and transformation of CNTs and the co-existing pollutants in the real environment. Although there are extensive research efforts on CNTs, the photochemistry of CNTs in aqueous solution is still unclear.In this study, the photochemistry of CNTs in steady state and transient state and the effects of CNTs on the photo-degradation of dye pollutants have been investigated. In the transient state, the ability of CNTs to be photo-ionized and to generate reactive oxygen species has been detected by laser flash photolysis and pulse radiolysis methods. In the steady state, the generation of singlet oxygen, superoxide radical and hydroxyl radical by CNTs was investigated with electron paramagnetic resonance and chemical probe methods. Based on the effects of CNTs on the photo-degradation of an azo dye and a triphenylmethane dye, the following conclusions were obtained:(1) The photo-degradation rate of dyes could be increased by CNTs because of the concentration reduction caused by adsorption of dyes to CNTs; (2) The photo-degradation rate of dyes could be decreased by CNTs because of the inner filter effect of CNTs; (3) In aqueous environment, CNTs can scavenge reactive oxygen species, but compared to the adsorption and inner filter effect, the scavenging effect of CNTs on the photo-degradation of dyes was less significant. This research is helpful for a comprehensive understanding of the photochemistry of CNTs and its impact on the fate and transport of other environmental pollutants.