Environmental Behavior And Bio-effects Of Graphene Oxide Nanomaterials

Graphene oxide(GO)with excellent physicochemical properties are widely used in many fields.They will inevitably enter the environment in the processes of production,transportation,use and disposal.GO are harmful to microorganisms,plants and animals,which will threaten human health and ecosystem security.When GO are released into the aquatic environments,the co-existing components(cation,anions,and organic matter)in natural surface water and natural light affect the physicochemical properties and colloidal behavior of GO,thus affecting its potential bio-toxicity and environmental effects.On the other hand,when GO is applied to the treatment and remediation of environmental pollution,the radionuclides,heavy metals or antibiotics carried by GO probably change its environmental behavior and biotoxicity,and consequently affect its application safety.In this paper,the environmental behavior and bio-effects of GO nanomaterials were studied by batch experiments,spectral characterization and density functional theory(DFT)calculation.The main results are as follows:(1)The effects of solution chemistry including pH,anions(Cl-,HCO3-,HPO42-and SO42-),and cations(K+,Ca2+,Na+,Mg2+and Al3+)on GO stability were investigated.We found that the GO aggregation induced by K+ or Na+ through electrostatic double layer(EDL)suppression and induced by Al3+or Ca2+through strong complxing.(2)The effects of physicochemical properties of GO,including size,functional groups and disorder degree,on the stability of GO in aqueous solution were discussed.By correlating the critical coagulation concentrations values with the physicochemical properties of GO,we acquired that the disorder degree played a more important effect on the colloidal properties and stability of phototransformed GO than functional groups.(3)The effects of light on the environmental behavior and biological effects of GO were discussed.The effects of UV and visible light on the physicochemical properties,stability,and the toxicity of GO were compared,and the related mechanisms were analyzed.The results revealed that light exposure had effects on the physicochemical properties of GO,and the time of light exposure had an important role in its colloidal stability and biotoxicity.(4)To evaluate the application safety of GO as an adsorbent for radionuclides,the aggregation kinetics,aggregate morphology and aggregation mechanisms of GO in the presence of Th4+,Eu3+,UO22+,Si2+,or Cs+were characterized.We found that Cs+ induced the aggregation of GO through EDL suppression and weak combining with oxygen containing functional groups.The charge transfer and electrostatic potential distribution contributed to the destabilizing ability of radioactive element cations with higher valence.(5)To further evaluate the application safety of GO as an adsorbent for bivalent heavy metal ions,the conjunct toxicity of GO and Me(?)(Cd2+,Co2+and Zn2+)was studied.The results showed that the destabilizing ability of Me(?)was consistent with the adsorption affinity of GO towards Me(?),which is negatively correlated to the hydration shell thickness of Me(?)but positively correlated to the ionic radius of Me(?).Moreover,the adsorption affinity of bacteria towards Me(?)was negatively correlated to Me(?)toxicity.Subsequently,the antibacterial properties of GO in combination with antibiotics(lincomycin hydrochloride,chloramphenicol and gentamycin sulfate)were studied.We found that the combined antibacterial ability of GO and antibiotics was unlikely to be attributed solely either to abiotic factors(e.g.,interaction of antibiotics with GO,physicochemical properties of antibiotics and GO)or to biotic factors(e.g.,the interaction between bacteria and GO,the sensitivity of bacteria to antibiotics,the physicochemical properties of bacteria).In summary,tour findings provide reliable data and experimental support for evaluating and predicting the application security and environmental risks of GO.