This research investigates the photocatalytic decolourisation of two selected dyes using multiple thin film coatings (three, four and five layers) of a TiO2 photocatalyst under a low intensity ultraviolet A (UVA) light source. The TiO2 photocatalyst was prepared using a simplified sol–gel process, and the decolourisation efficiencies of the two experimental dyes, indigo carmine and reactive black 5, were studied. The kinetics of the photocatalytic decolourisation reactions under low intensity UVA were described by a pseudofirst order kinetic model, and the photocatalytic kinetic rate constants were reported. An increase in the number of coating layers contributed to the TiO2 photocatalyst's smaller grain size, higher surface area and narrower optical band gap. The findings also revealed a positive relationship between the number of TiO2 coating layers and the efficiencies and kinetics of dye decolourisation in the experimental photocatalytic process. In addition, the TiO2 thin film photocatalyst induced high photocatalytic activity, even under low intensity UVA light.
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