title: Sunlight affects aggregation and deposition of graphene oxide in the aquatic environment.
abstract: In this study, we investigate the role of simulated sunlight on the physicochemical properties, aggregation, and deposition of graphene oxide (GO) in aquatic environments. Results show that light exposure under varied environmental conditions significantly impacts the physicochemical properties and aggregation/deposition behaviors of GO. Photo-transformation has negligible effects on GO surface charge, however, GO aggregation rates increase with irradiation time for direct photo-transformation under both aerobic and anaerobic conditions. Under anaerobic conditions, photo-reduced GO has a greater tendency to form aggregates than under aerobic conditions. Aggregation of photo-transformed GO is notably influenced by ion valence, with higher aggregation found in the presence of divalent ions versus monovalent, but adding natural organic matter (NOM) reduces it. QCM-D studies show that deposition of GO on surfaces coated with organic matter decreases with increased GO irradiation time, indicating a potential increase in GO mobility due to photo-transformation. General deposition trends on Suwannee River Humic Acid (SRHA)-coated surfaces are control GO > aerobically photo-transformed GO ≈ anaerobically photo-transformed GO. The release of deposited GO from SRHA-coated surfaces decreases with increased irradiation time, indicating that photo-transformed GO is strongly attached to the NOM-coated surface.
authors.affiliation: National Research Council Associate, National Exposure Research Laboratory, Ecosystems Research Division, U. S. Environmental Protection Agency, Athens, GA 30605, USA. Electronic address: Chowdhury.Indranil@epa.gov.
authors.forename: Indranil
authors.initials: I
authors.lastname: Chowdhury
authors.affiliation: National Research Council Associate, National Exposure Research Laboratory, Ecosystems Research Division, U. S. Environmental Protection Agency, Athens, GA 30605, USA; Department of Environmental Engineering, National Cheng Kung University, Tainan City 70101, Taiwan, ROC.
authors.forename: Wen-Che
authors.initials: WC
authors.lastname: Hou
authors.affiliation: Department of Chemistry, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: David
authors.initials: D
authors.lastname: Goodwin
authors.affiliation: National Exposure Research Laboratory, Ecosystems Research Division, U. S. Environmental Protection Agency, Athens, GA 30605, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Henderson
authors.affiliation: National Exposure Research Laboratory, Ecosystems Research Division, U. S. Environmental Protection Agency, Athens, GA 30605, USA.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Zepp
authors.affiliation: National Exposure Research Laboratory, Ecosystems Research Division, U. S. Environmental Protection Agency, Athens, GA 30605, USA. Electronic address: Bouchard.Dermont@epa.gov.
authors.forename: Dermont
authors.initials: D
authors.lastname: Bouchard
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D006108:Graphite / Q000737:chemistry / Q000528:radiation effects*; D006812:Humic Substances; D007700:Kinetics; D049329:Nanostructures / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry / Q000528:radiation effects; D013472:Sunlight; D013499:Surface Properties; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000528:radiation effects
chemical_list: D006812:Humic Substances; D010087:Oxides; D014874:Water Pollutants, Chemical; D006108:Graphite
keywords: Aggregation; Graphene oxide; Photo-transformation; Sunlight; Transport