Microwave-enhanced UV/H₂O₂degradation of an azo dye (tartrazine): optimization, colour removal, mineralization and ecotoxicity

Abstract

This study optimizes two factors, pH and initial [H2O2], in the ultraviolet (UV)/H2O2/microwave (MW) process through experimental design and assesses the effect of MWs on the colour removal of an azo-dye (tartrazine) solution that was favoured by an acidic pH. The estimated optimal conditions were: initial [H2O2] = 2.0 mmol L(-1) and pH = 2.6, at 30 +/- 2 degrees C. We obtained colour removals of approximately 92% in 24 min of irradiation (EDL, 244.2 W), following zero order kinetics: k = (3.9 +/- 0.52) x 10(-2) a.u. min(-1) and R2 = 0.989. Chemical and biological oxygen demand were significantly removed. On the other hand, the carbon content, biodegradability and ecotoxicity (Lactuca sativa) remained approximately the same. The UV/H2O2/MW process was shown to be eight times faster than other tested processes (MW, H2O2, H2O2/MW, and UV/MW).

Study and application status of microwave in organic wastewater treatment – A review

“…The UV-H 2 O 2 process is one of the oldest AOPs and can treat various organic pollutants based on the generation of OH·. Some of its advantages have attracted the attention of researchers, for example, the commercial availability of the oxidant, the formation of two OH· from each H 2 O 2 molecule under photocatalysis, minimal capital investment, cost-effectiveness, and simple operating procedures [126].…”

Investigation of TiO2 photocatalyst performance for decolorization in the presence of hydrodynamic cavitation as hybrid AOP

“…AOPs involve the generation of hydroxyl radicals and complete oxidization of such pollutants including dyes converted into end products, such as CO 2 , H 2 O, etc [7]. Recent literature has indicated that hybridization of different AOPs has been found to be more efficient for the wastewater treatment than individual oxidation process [8,9].…”

Microwave Assisted Reduction for Screening Banned Aromatic Amines in Azo Dyes

“…One such example is the microwave assisted degradation of Acid orange 7 dye in 10 min, carried out on polyaniline substrate used as catalyst [12]. Microwave energy has also been utilized for degrading dyes in different combinations such as with UV radiation and O 3 [13], and sometimes with UV and H 2 O 2 [14,15]. It has also been reported that decreasing the starting reaction temperature to sub-zero levels can change the products in microwave assisted organic reactions [16].…”