Degradation of Orange G by UV/TiO2/IO4 process: Effect of operational parameters and estimation of electrical energy consumption

In the present study, the degradation of an azo dye Orange G (OG) by the UV/TiO2/periodate (IO4-) process has been investigated. OG was totally disappears within 10 min by the UV/TiO2/IO4-compared to UV alone, UV/TiO2 or UV/IO4-. A synergistic effect has been obtained when combining the UV/TiO2 and the UV/IO4-systems, resulting in positive interactions between both processes. Experiments conducted with specific hydroxyl radical scavengers, show that despite the inhibition effect observed, complete degradation has been achieved beyond 10 min, demonstrating that the degradation is not only initiated by hydroxyl radical, but also by other reactive entities; the involvement of iodate radical is confirmed with the use of chromium species as a competitor with periodate ions for the photogenerated electron at the conduction band. The operating parameters influencing the degradation process such as initial dye concentration, initial periodate concentration, light intensity/wavelength and initial pH solution have been explored. The presence of inorganic ions such as chloride, bromide, sulphate, carbonate and bicarbonate ions in the irradiated solution show reverse effects depending on the concentration used. The OG degradation in different water matrices is found to be sensitive to the presence of different species and their nature. Chemical oxygen demand (COD) has been partially removed after 10 min of treatment, and then this COD abatement stabilized, indicating the strength of the by-products from dye degradation by the UV/TiO2/IO4- system during the treatment time. The electrical energy consumption is estimated at 2.21kWhm-3/Order. The results obtained indicate that the UV/TiO2/IO4- process could be used as a hybrid process to the treatment of dye contaminated water.