Abstract
Graphene oxide (GO) is widely used in various fields and has raised concerns regarding its potential environmental fate and effect. However, there are few studies on its influence on coexisting pollutants. In this study, the phototransformation of GO and coexisting sulfamethazine (SMZ) under UV irradiation was investigated, with a focus on the role of reactive oxygen species. The results demonstrated that GO promoted the degradation of SMZ under UV irradiation. The higher the concentration of GO, the higher the degradation rate of SMZ, and the faster the first-order reaction rate. Two main radicals, ∙OH and 1O2, both contributed greatly in terms of regulating the removal of SMZ. Cl−, SO42−, and pH mainly promoted SMZ degradation by increasing the generation of ∙OH, while humic acid inhibited SMZ degradation due to the reduction of ∙OH. Moreover, after UV illumination, the GO suspension changed from light yellow to dark brown with increasing absorbance at a wavelength of 225 nm. Raman spectra revealed that the ID/IG ratio slightly decreased, indicating that some of the functional groups on the surface of GO were removed under low-intensity UV illumination. This study revealed that GO plays important roles in the photochemical transformation of environmental pollutants, which is helpful for understanding the environmental behaviors and risks of nanoparticles in aquatic environments.
Highlights
We systematically investigated the interaction between graphene oxide (GO) and SMZ under UV light, considering the influence of different environmental factors, including pH values, ionic strength and species, and natural organic matter (NOM)
GO could promote the degradation of SMZ under UV light. ·OH
1 O2 were the main free radicals participating in the cotransformation between GO
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. As a kind of two-dimensional layered nanomaterial, graphene oxide (GO) possesses good mechanical, electrical, and thermal properties, and is widely applied in various fields, including biology, medicine, chemistry, and electronic engineering [1]. Due to the presence of a large number of oxygen-containing functional groups, such as hydroxyl, carboxyl, and epoxy groups, GO has excellent hydrophilicity and a high probability of being present in natural aquatic environments, having uncertain environmental impacts and ecological risks. GO could cause developmental genotoxicity in aquatic animals such as zebrafish at trace concentrations [5], and could even accumulate in humans through the food chain [6]. An increasing number of studies on the environmental behaviors of GO have received attention
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