Improvement of sonochemical degradation of Brilliant blue R in water using periodate ions: Implication of iodine radicals in the oxidation process

In this paper, the effect of periodate (IO₄^?) on the ultrasonic degradation at 300 kHz of Brilliant Blue R (BBR), an organic dye pollutant, was investigated. The experiments were realized in the absence and presence of periodate for various operating conditions including initial solution pH (2–8) and delivered ultrasonic power (20–80 W). It was found that periodate greatly enhanced the sonochemical degradation of BBR. The degradation rate increased significantly with increasing IO₄^? concentration up to 10 mM and decreased afterward. With 10 mM of periodate, the degradation rate was 2.4-fold higher than that with ultrasound alone. The chemical probes experiments showed that periodate activation into free radicals (IO₃, IO₄ and OH) takes place by sonolysis and iodine radicals contribute significantly in the oxidation process. It was found that the periodate-enhanced effect was strongly experimental parameters dependent. The advantageous effect of periodate increased significantly with decreasing power and the best enhancing effect was obtained for the lowest power. Correspondingly, the periodate-enhanced effect increased with pH increase in the range 2–8 and it was more remarkable at near alkaline condition (pH 8). A reaction scheme for periodate sonolysis was proposed, for the first time, discussed and then used for interpreting the obtained results.