  Graphene oxide (GO) is widely used in different applications, however once
release into the environment it can change its structure and affect the
transport of important contaminants such as arsenic. In this work we show that
UV radiation, even in the range of 28-74 uW/cm2 of irradiance up to 120 h of
exposure, can induce important changes in the structure of graphene oxide, by
eliminating -OH and C=O functional groups. This reduction affected the
stability of graphene oxide in water by decreasing its zeta potential from 41
to 37 mV with the increase of the exposure time. Our results showed that after
24 h of UV exposure, As(III) adsorption capacity decreased from 5 mg/g to 4.7
mg/g, however after 48 h of irradiation the adsorption increased with time,
reaching 5.1 mg/g at 120 h under 74 uW/cm2 of irradiation. Computer modelling
showed that even a degraded GO structure can have an interaction energy of 53
kcal/mol with H3AsO3. Furthermore, we observed that despite clear changes in
surface composition and particle size, the reduction of graphene oxide
maintained a high degree of cytotoxicity since cell viability decreased to 60%
with a 50 ug/ml dose; except for the sample irradiated at 74 uW/cm2 for five
days, which showed 20% with the same concentration.
