Abstract
Advanced oxidation processes (AOPs), based on hydroxyl radical (
·
OH) induced oxidation, have been widely investigated to develop novel and green technologies for wastewater treatment. In this work, the degradation and mineralization of Basic Red 29 (BR29), a cationic azo dye, by ultrasound (US) at 300 kHz and 80 W was investigated. Even if ultrasound eliminated BR29 (30 mg L
−1
) in 1 h, a low degree of mineralization (~10 %) was obtained due to the hydrophilic character of the byproducts formed during the sono-oxidative process. To overcome this weakness, an innovative technique integrating ultrasound/Fe
2+
/TiO
2
was used and was found to be more effective for the degradation and mineralization of the dye. The amount of each catalyst was optimized for the three systems US/TiO
2
, US/Fe
2+
and US/Fe
2+
/TiO
2
. The degradation rate of BR29 with US/Fe
2+
and US/Fe
2+
/TiO
2
treatments was, respectively, 2 and 2.34 times higher than that obtained with US alone. Correspondingly, the mineralization degree increased from 5 % with ultrasound alone to 10 % with US/TiO
2
, 35 % with US/Fe
2+
and 64 % with US/Fe
2+
/TiO
2
after 30 min of treatment and from 10 % with US to 13, 51, and 81 % with, respectively, US/TiO
2
, US/Fe
2+,
and US/Fe
2+
/TiO
2
processes after 1 h of treatment. These results showed a synergy of 1.41 at 30 min and 1.29 at 1 h between US/Fe
2+
and US/TiO
2
processes toward the mineralization of BR29. The mechanism of the beneficial effect of the US/Fe
2+
/TiO
2
integrating treatment was clarified and discussed.