Photodegradation of bisphenol A by ZnS combined with H2O2: Evaluation of photocatalytic activity, reaction parameters, and DFT calculations

Bisphenol A (BFA) is a synthetic emergent contaminant with wide industrial applications and resistant to degradation by conventional treatment methods, which makes the use of heterogeneous photocatalysis a promising alternative. In this context, a theoretical and experimental study on the photodegradation of BFA was carried out under ultraviolet–visible (UV) radiation using a ZnS photocatalyst. The structural, optical, and morphological properties of the samples were investigated. The effect of the reactional parameters (catalyst dose, initial pH, and H2O2 concentration) on the photocatalyst efficiency was studied, and the concentrations of BFA were measured by UV/Vis spectroscopy. Adding an oxidizing agent (H2O2) to ZnS was crucial for achieving photodegradation of 97.2 % after 120 min of exposure to UV light. Based on the results of theoretical calculations, it was possible to evaluate how the pH changes the UV/Vis spectra, the frontier molecular orbitals, the molecular electrostatic potential of the protonated and deprotonated species of bisphenol A and thus evaluate that the neutral pH is the most suitable for the application of the photocatalytic process. The reactivity indices indicated that the BFA is reactive, exhibited a strong electron attraction and thus can react with the radical species formed. The most significant contributions to the electronic transitions are between the HOMO to the LUMOs, which elucidate the main electronic characteristics of the BFA for the photodegradation process. Considering to satisfactory photocatalytic activity and stability, ZnS combined with H2O2 has potential for photocatalytic applications.