Effects of operational parameters on decolorisation of C.I. Reactive Black 5 in UV/TiO₂ system

This study utilises a UV/TiO₂ system to decolorise C.I. Reactive Black 5 (RB5). The effects of TiO₂ dosage, pH, RB5 concentration and light power on the decolorisation efficiency using the UV/TiO₂ system were determined. IO₄⁻ was employed as an oxidant to increase the photodegradation efficiency of UV/TiO₂. The decolorisation rate constants (k) of RB5 in the UV/TiO₂ system are consistent with pseudo-first-order kinetics. The k values of 0.1, 0.5, 1.0 and 2.0 g/l TiO₂ were 0.53, 0.52, 0.69 and 0.68 h⁻¹, respectively. The rate constant increases with decreasing pH from 10 to 4. The decolorisation rate approximates linear relationship with RB5 concentration, as given by k=1.05[1/RB5]^0.98; it varies nonlinearly with light power, as given by k=0.178[power]^0.63. The experimental results reveal that the rate of decolorisation obtained using UV/TiO₂/IO₄⁻ exceeds that obtained using UV/TiO₂.