Quantum chemical investigation of the degradation of acid orange 7 by different oxidants

Abstract

Acid Orange 7 (AO7) is a common azo dye that have found useful application in textile and other industries. However, its toxic and recalcitrant nature presents significant environmental challenges, making it difficult to degrade in wastewater. This study investigates the degradation of AO7 using Density Functional Theory (DFT) calculations, focusing on the structural and electronic properties of AO7 and the effectiveness of different oxidants (H2O2, O3, •OH, SO4•−). Geometry optimization of AO7 was performed using various DFT methods (B3LYP, M06, wB97XD, mPW1PW91, and CAM-B3LYP) with 6-31G(d) and 6-311G(d,p) basis sets. Natural Population Analysis (NPA) revealed significant electron-withdrawing effects of the azo, carbonyl, and sulfonic groups. Additionally, frontier molecular orbital analysis and quantum chemical predictors indicated that O3 will interact well with AO7. However, the •OH was found to be the most effective oxidant, due to its high oxidation potential and low binding energy. The SO4•− also demonstrated strong potential due to its strong interaction and high oxidation potential. While •OH may facilitate faster degradation, oxidants like SO4•− may form more stable complexes with AO7 before initiating degradation. This study highlights the versatility of •OH in degradation processes, providing valuable insights into advanced oxidation processes for environmental remediation.