Graphene Adsorption Of Polychlorinated Biphenyls And Their Effects On Phytotoxicity

Graphene is a new nanomaterial with two-dimensional structure composed of carbon atoms sp2 hybrid formation. Because of its excellent physical and chemical properties, it has been used in various fields. With the increasing graphene production and usage, Graphene will inevitably enter into the air, water and soil environments, which have effect on the growth of plants and the pollutants environmental behavior, the study of biological and environmental toxic effects of graphene is necessary. Polychlorinated biphenyls(PCBs) are typical chlorinated organic pollutants in the environment. Since they are semi-volatile, bioaccumulative and high toxic, PCBs were on the list of prior persistant organic pollutants(POPs) by UNEP. Whether it would have an impact on bioavailability and migration of PCBs in the environment after PCBs graphene combination is an urgentenvironmental problemto solve. In this paper, we choice graphene and PCB28 two typical substances, and research on graphene plant toxic effects, the adsorption properties of graphene on PCB28 and possible mechanisms of sorption, we alsostudy the the effect on plant uptake and accumulation ofPCB28 in the presence ofgraphene.The main conclusions are as follows:1, Based on solid phase extraction of chemicals onto the plastic polyoxymethylene(POM-SPE), useing batch equilibrium method to study graphene(SG, GO) on the adsorption properties ofPCB28. Langmuir equation and Freundlich equation could well describe SG, GO adsorption results of the PCB28,using three adsorption isotherm fitting. with increasing of equilibrium concentration,the adsorption capacity of PCB28 on SG, GO is higher in adsorption isotherm. The effects of different environmental factors on the adsorption processes was observed. Adsorption of PCB28 on SG, GO is stronger with the pH value increasing, however, Temperature effects to give the oppositeresults,thetemperature is higher the adsorption capacity is lower,it was proved that adsorption process belongs to the exothermic reaction. To further explore the mechanism of adsorption, we use FTIR spectra change of samples before and after sorption. It showed that the adsorption mechanism SG, GO to PCB28 presence ?-? conjugation and the hydrophobic effect, but it wasnot the main adsorption mechanism. By analyzing the variation of different functional groups on the surface of graphene,weconfirmed the presence of ions(H-?interaction and anion-?interaction), these two effects may be the main mechanism of adsorption.2, The results showed that sulfonated graphene had a significant concentration-doseresponse relationship in the concentration range tested. It can promote the growth of maize seedlingsat low concentrations, butoppositeat high concentrations. The effects of 50 mg·L-1sulfonated graphene are obvious promote, however it has been shown to significantly inhibitin 500 mg·L-1. Antioxidative enzyme activities of maize seedlings undergone different changes, SOD, POD, MDA in root has declined relative to the controlat low concentrations, while they were significantly increased at high concentrations indicating that the oxidative stress occurredin corn seedlings, and research activity and permeability of cell membrane also proved this. To visualize the effects of sulfonated graphene on maize, the content of reactive oxygen species(ROS) and the apical surface morphology were imaging observation. Indicating that little ROS induction in vivo and tightly packed cells, apical full at low concentrations of sulfonated graphene. while a large number of reactive oxygen species content has been observed in vivoand severely damaged cells, the more wrinkles on apical surface were found at high concentrations.3, Under sulfonated graphene and PCB28 coexistence, theintake,accumulation of PCB28 and its metabolites in maize seedlings were analyzed and found that graphene and PCB28 coexistence did not have asignificantly impact on the growth of maize seedlings in a short time, but PCB28 intake and accumulation in the body have a certain effect. sulfonated graphene can reduce the adsorptionof PCB28 on root surface, increasing the intake of PCB28 in roots, the PCB28 content in corn seedling stems and leaves adding sulfonated graphene is higher than the absence of sulfonated graphene. That to say, after the addition of sulfonated graphene it will increase the intakeof PCB28 in root, but reduce transfer to shoots. Two metabolic ways: dechlorination and chlorinerearrangement were exist incorn vivo, PCB8, PCB18 were found in maize. PCB18 content in the seedling is higher than PCB8, showed thatChlorine rearrangements was more important than dechlorination in corn metabolic process.