Effect of the size on the aggregation and sedimentation of graphene oxide in seawaters with different salinities

Graphene oxide (GO) with different sizes is inevitably released into the water environment during its production, use, and disposal. Aggregation and sedimentation would occur when GO entered into the water with high ionic strength. However, the environmental behavior and fate of GO in the coastal water are not well known. Therefore, in the present study, the aggregation and sedimentation of GO nanosheets with different sizes in seawater with different salinities were investigated. GO nanosheets with different sizes were prepared by the ultrasonic pulverization. Compared to original GO, the ultrasonically pulverized GO was more stably dispersed in deionized water. In artificial seawater, the aggregation–sedimentation process became more intense with increasing GO concentration and salinity. With the decrease of the GO nanosheet size, the aggregation–sedimentation rate increased, while the critical aggregation and sedimentation salinity decreased. As GO could deposit in wide coastal waters, which might cause potential ecological risks to marine benthic organisms, its environmental behavior, fate, and ecological risks in the coastal water should be further investigated.