Influence of surfactants in improving degradation of polluting dyes photocatalyzed by TiO2 in aqueous dispersion

The role of tetraalkylammonium bromide surfactants on the TiO2 photocatalyzed degradation of Alizarin, Purpurin and Bromothymol Blue has been studied in air-equilibrated aqueous medium under UV light irradiation. Alizarin has also been investigated by carrying out the photodegradation in TiO2/surfactant dispersions irradiated by natural solar light. Absorption spectral analysis showed that the photodegradation efficiency of the dyes was significantly enhanced by the addition of the cationic surfactants. The effect of pre-micellar, micellar and post-micellar concentrations of the surfactants was analyzed to gain insight into the mechanism of the surfactant assisted TiO2-photocatalytic degradation of the three dyes. The findings revealed that various parameters, such as initial pH, dye pK's, type of water and light source exerted their influence on the photocatalytic degradation. The results were explained on the basis of hydrophobic and electrostatic interactions between dye and surfactant/TiO2 in the various forms of aggregation. Density functional theory (DFT) calculations of charge distribution and Gibbs free energy changes of solvation of the species involved were used as a support in rationalizing the surfactant effect on the photodegradation process.

Automated summary

The study indicated that tetraalkylammonium bromide surfactants significantly enhance the efficiency of TiO2 photocatalytic degradation of dyes, with various factors such as initial pH, dye pK's, water type, and light source influencing the process. The hydrophobic and electrostatic interactions between dye and surfactant/TiO2 in different forms of aggregation play a crucial role in explaining the surfactant effect on the photodegradation process.