H2O2/periodate (IO4−): a novel advanced oxidation technology for the degradation of refractory organic pollutants

This study demonstrated, for the first time, that the H2O2/IO4− system could be an efficient advanced oxidation process (AOP) for wastewater treatment. Batch experiments conducted under ambient conditions with toluidine blue (TB), as a model pollutant, showed that 98% of TB and 73% of the initial total organic carbon were removed after only 1 min of treatment when using a H2O2 : IO4− molar ratio of 10. Radical scavengers such as ascorbic acid, tert-butanol, 2-propanol, sodium azide and phenol were used to study the reactive species. It was found that ˙OH, 1O2 and IO3˙ play a key role in TB degradation whereas O2˙− acts mainly as a free-radical precursor. The experimental conditions that affected the performance of the process were carefully examined after discussing the degradation mechanism. The TB removal rates increased with increasing H2O2 and periodate concentrations up to certain optimums and decreased afterward. Increasing the liquid temperature, the solution pH and the initial pollutant concentration adversely affected the degradation rate of TB. Finally, the H2O2/periodate system may serve as a very simple and efficient method of multiple free radical generation in water and, therefore, the process should be involved as an alternative AOP for the degradation of micropollutants in aqueous effluents, although complete by-product identification and toxicity evaluation may still be necessary to establish process viability.