Ponceau S dye decolorization during the Fe(II)/UV/Chlorine and Cu(II)/UV/Chlorine processes: experimental and theoretical study

Abstract

Researchers are increasingly studying and practicing advanced oxidation processes (AOPs) for micropollutant abatement in drinking water treatment and potable water reuse. This study conducted the comparison of the UV/chlorine, Fe (II)/UV/Chlorine, and Cu (II)/UV/Chlorine processes for the degradation of Ponceau S azo dye aqueous solution. The experimental study shows an enhancement in the degradation rate of PS dye in which complete degradation was obtained at 10 min reaction time when Fe²⁺ and Cu²⁺ were added to the solution. This improvement is due to catalyzing HOCl by ferrous and copper ions.

Using the density functional theory (DFT) with the hybrid method B3LYP by 6–311 + G(d,p) basis set, all theoretical calculations and optimum geometric parameters have been computed. We are able to identify Ponceau's electronic and energetic actions thanks to this investigation. Natural population analysis (NPA) and the Mulliken population method have both been researched. The parr function has been used to study the molecule's \({P}_{k}^{-}\) and \({P}_{k}^{+}\) local reactivity. To visualize the charge transfer between the lone pairs and localized bonds, natural bond orbital (NBO) analysis is performed. DFT is also used to examine molecular electrostatic potential (MEP) and to describe orbital hybridization. The study's findings suggest that both processes are viable for dye removal in water treatment, though further optimization of operating conditions, such as pH and metal ion concentration, could further improve performance.