The evaluation of electrical energy per order (E_Eo) for photooxidative decolorization of four textile dye solutions by the kinetic model

Photooxidative decolorization of four textile dyestuffs, C.I. Acid Orange 7 (AO7), C.I. Acid Orange 8 (AO8), C.I. Acid Orange 52 (AO52) and C.I. Acid Blue 74 (AB74), by UV/H₂O₂ was investigated in a laboratory scale photoreactor equipped with a 15 W low pressure mercury vapour lamp. The decolorization of the dyes was found to follow pseudo-first-order kinetics, and hence the figure-of-merit electrical energy per order (E_Eo) is appropriate for estimating the electrical energy efficiency. The E_Eo values were found to depend on the concentration of H₂O₂, concentration and basic structure of the dye. This study shows that these textile dyes can be treated easily and effectively with the UV/H ₂O₂ process with E_Eo values between 0.4 and 5 kW h m^-3 order^-1, depending on the initial concentrations of dyes and H₂O₂. The kinetic model, based on the initial rates of degradation, provided good prediction of the E_Eo values for a variety of conditions.