Combination of UVC-LEDs and ultrasound for peroxymonosulfate activation to degrade synthetic dye: influence of promotional and inhibitory agents and application for real wastewater

Abstract

Several efforts have been carried out to present an efficient method for PMS activation. This work presented the use of UVC-LEDs (light emitting diodes) and US (ultrasound) to activate PMS for decolorization of Direct Orange 26 (DO26). The performance of UVC-LEDs/US/PMS process was effective in a broad range of pH (3.0-9.0). Complete decolorization was obtained in only 12 min in pH = 7.0 and 1.5 mM PMS. Bicarbonate and nitrite ions showed inhibitory effect on decolorization while sulfate, chloride, and nitrate had no significant effect on the performance of the process. Transition metals in homogenous (Fe²⁺ and Co²⁺) and heterogeneous forms (Fe₃O₄ and Co₃O₄) accelerated decolorization in UVC-LEDs/US/PMS system. The presence of turbidity declined the performance of UVC-LEDs/US/PMS through the prevention of PMS activation by UV and US. Compared to other oxidants (S₂O₈^2-, H₂O₂ and 2Na₂CO₃.3H₂O₂), PMS proved the higher function in decolorization of DO26 in UVC-LEDs/US/oxidant system. Scavenging experiments showed that ¹O₂, HO^•, and SO₄^•- contributed in the degradation of DO26. Moreover, the UVC-LEDs/US/PMS system could markedly increase the biodegradability of real textile wastewater. These results promised an effective process for degradation of organic pollutants from aquatic environment.

Keywords: Dye degradation; Peroxymonosulfate; Sulfate radical; UVC-LEDs; Ultrasound.