Efficient photocatalytic degradation of profenofos by CuO-ZnO nanocomposite

Abstract

Exposure to organophosphate pesticides, such as profenofos, poses a serious threat to humans and other living organisms and thus, it needs serious precaution measurements. Herein, we have developed bimetallic nanocomposite CuO-ZnO (2:1 ratio) with two band edges (1.60 eV and 3.1 eV) and two band potentials (1.373 eV and − 0.207 eV) as an appealing heterogeneous photocatalyst for the effective adsorption and photocatalytic degradation of profenofos at an ambient condition. The degradation process occurs rapidly, manifesting within a brief duration under light exposure. Notably, the CuO-ZnO) nanocomposite was directly subjected to the highest profenofos dose (1215 mg/L). Impressively, complete photocatalytic degradation (100 %) was achieved within just 80 min of exposure, emphasizing the efficacy of the photocatalytic process as a degradation/transformation pathway. Furthermore, a proposed degradation/transformation and mineralization pathway for the profenofos pesticide was delineated, based on results obtained from spectroscopic and chromatographic techniques. UV–visible spectrophotometric analysis tracked the degradation and transformation of profenofos (275.5 nm) to 2-chloro-3-bromo phenol (287.2 nm), while its mineralization was confirmed through NMR, ATR-IR, and GC–MS analysis. The explored catalytic activities, and degradation pathway intensely suggested that the hydroxyl radical (HO•) radicals are the central active degradation species produced through the “VB” pathway on the surface of CuO-ZnO nanocomposite.The kinetics models showed that the reaction predominantly follows second-order kinetics. Additionally, thermodynamic parameters, like enthalpy (ΔH), entropy (ΔS) and Gibbs free energy (ΔG) were evaluated, revealing the exothermic and spontaneous nature and of the reaction. Besides, CuO-ZnO nanocomposite possesses the optimal recyclability for up to seven rounds with nominal loss in the degradation efficacy and sustaining its structural features proving its robust nature towards the degradation of profenofos. Additionally, the environmental hazard posed by the profenofos pesticide, and its degradation products was assessed using the Estimation Program Interface (EPI) SuiteTM v.4.11, developed by the US Environmental Protection Agency. The estimation models affirmed that the degradation and transformation products exhibit relatively lower toxicity levels compared to profenofos.