Effect of UV radiation on the structure of graphene oxide in water and its impact oncytotoxicity and As(III) adsorption

Abstract

Graphene oxide (GO) is widely used in different applications, however once released into 19 the environment it can change its structure and affect the transport of important 20 contaminants such as arsenic. In this work we show that UV radiation, even in the range of 21 28-74 μ W/cm2 of irradiance up to 120 h of exposure, can induce important changes in the 22 structure of graphene oxide, by eliminating -OH and C=O functional groups. This reduction 23 affected the stability of graphene oxide in water by decreasing its zeta potential from -41 to 24 -37 mV at pH= 7 with the increase of the exposure time. Our results showed that after 24 25 and 120 h of UV exposure, As(III) adsorption capacity decreased from 5 mg/g to 4.7 and 26 3.8 mg/g, respectively, suggesting a lower capacity to transport contaminants with time. 27 Computer modeling showed that even a degraded GO structure can have an interaction 28 energy of 223.84 kJ/mol with H3AsO3. Furthermore, we observed that the cytotoxicity of 29 graphene oxide changed after being irradiated at 74 μ W/cm2 for 120h, showing 20% more 30 cell viability compared to as-produced GO. Our results stress the importance of considering 31 the microstructural and compositional changes that GO undergoes even under low 32 irradiance and short periods, when studying its fate and behavior in the environment and 33 possible applications in water treatment.