Insight into the mode of action of Pd-doped zero-valent iron nanoparticles @graphene (Pd/FePs@G) toward carbon tetrachloride dechlorination reaction in aqueous solution

Abstract

Herein, Pd/Fe bimetallic nanoparticles (Pd/FePs) were uniformly distributed on the surface of graphene sheet structure, and had good combination with the multilayer substrate. The nanocomposites could maintain high reactivity even after five times degradation reactions of carbon tetrachloride (CT) in succession, indicating that the modified technology had a positive effect on achieving high surface activity and prolonging the longevity. The structure evolution and compositional changes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photo-electron spectroscopy (XPS). Also, humic acid (HA) as non-reactive adsorbate could preferentially occupy surface active sites of Pd/FePs to mediate the predominant radical species in the degradation process, which caused a 53% decrease in dechlorination rate of CT. These findings provided an important understanding of the stability and reactive mechanism involved in Pd/Fe bimetallic system toward CT degradation. Moreover, batch experiments were conducted to investigate the actual catalytic activity in view of the effects of common inorganic anions in aqueous solution. The results revealed that the presence of Cl−, HCO3−, and HPO42− was beneficial to the CT degradation while SO42- and NO3− exerted the negative effects. Based on the detection results by means of gas chromatography (GC) and ion chromatography (IC), a possible degradation pathway was propose.