Photocatalytic decolorisation and mineralisation of orange dyes on immobilised titanium dioxide nanoparticles.

In this paper the photocatalytic decolorisation and mineralisation of three orange dyes (AO10, AO12 and AO8) in neutral, alkaline and hydrolysed solutions under UV light irradiation in the presence of TiO(2) nanoparticles has been compared. The investigated photocatalyst was Millennium PC-500 TiO(2) (crystallites mean size 5-10 nm) immobilised on non-woven paper. All the experiments were performed in a circulation photochemical reactor equipped with a 15 W UV lamp emitting around 365 nm. Results indicated that complete decolorisation of 250 mL pure dye solutions with initial dye concentration of 30 mg/L could be achieved in 140 min. Photocatalytic mineralisation of the neutral, alkaline and hydrolysed dye solutions was monitored by total organic carbon (TOC) decrease and ammonium ion formation. Results indicated that the photocatalytic decolorisation and mineralisation of the dyes was less efficient with the hydrolysed and alkaline dye solutions in comparison with the neutral pure dye solutions. The amount of NH(4)(+), as N-containing mineralisation product, during UV/TiO(2) process was analysed. The electrical energy consumption for photocatalytic decolorisation of the dyes was calculated and related to the treatment costs.