Bifunctional catalytic degradation of diclofenac over Cu-Pd co-modified sponge iron-based trimetal: Parameter optimization

Abstract

Currently, the pharmaceutical and personal care products (PPCPs) have posed great challenge to advanced oxidation techniques (AOTs). In this study, we decorated sponge iron (s-Fe⁰) with Cu and Pd (s-Fe⁰-Cu-Pd) and further optimized the synthesis parameters with a response surface method (RSM) to rapidly degrade diclofenac sodium (DCF). Under the RSM-optimized conditions of Fe: Cu: Pd = 100: 4.23: 0.10, initial solution pH of 5.13, and input dosage of 38.8 g/L, 99% removal of DCF could be obtained after 60 min of reaction. Moreover, the morphological structure of trimetal was characterized with high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS). Electron spin resonance (ESR) signals have also been applied to capture reactive hydrogen atoms (H*), superoxygen anions, hydroxyl radicals, and single state oxygen (¹O₂). Furthermore, the variations of DCF and its selective degradation products over a series of s-Fe⁰-based bi(tri)metals have been compared. Additionally, the degradation mechanism of DCF has also been explored. To our best knowledge, this is the first report revealing the selective dechlorination of DCF with low toxicity over Pd-Cu co-doped s-Fe⁰ trimetal.

Keywords: Advanced oxidation techniques (AOTs); Bimetal; Pharmaceutical and personal care products (PPCPs); Response surface method (RSM); Zero-valent iron (ZVI).