The Effect Of Physical And Chemical Properties Of Water Environment On The Performance Of Graphene Adsorption/desorption Of Organic Pollutants

In recent years,due to its ultra-thin single-layer structure and unique physicochemical properties,graphene has become the hottest carbon nanomaterial in research,and is widely used in various fields such as optoelectronics,biology and environmental protection.Its preparation method is becoming more and more mature and has gradually been transferred to industrial production.With its production,transportation,use and disposal,a large amount of graphene inevitably enters t he water environment,greatly increasing the environmental and human exposure to graphene.Due to its large specific surface area and a large number of surface oxygen-containing functional groups,GO has a strong adsorption capacity for pollutants,which will enrich the organic pollutants in the water environment,which may affect the migration,transformation and return of pollutants.Resisting environmental behaviors,which in turn affect the ecological risks of pollutants.Therefore,studying the adsorption behavior of graphene and pollutants is the premise to accurately evaluate the migration and fate of pollutants in the environment.In the actual water environment,the interaction between the two is not only related to its own nature,but also affected by the physical and chemical properties of the water environment(such as pH,dissolved organic matter and ionic strength).In this study,relatively simple and regular structure of graphene oxide(GO)and reduced graphene oxide(RGO)were selected as mod el adsorbent materials,and hydrophobic pollutants(bisphenol A,nitrobenzene)and antibiotics(ofloxacin)were selected.,norfloxacin)is the model of adsorbate.The effects of physicochemical properties such as coexisting cations(calcium and magnesium ions),water acidity and alkalinity factors and dissolved organic matter(DOM)on the adsorption of organic pollutants by graphene were investigated,and the adsorption mechanism of graphene and organic pollutants was elucidated.This study will establish a basic data reserve for environmental behavior prediction and risk assessment of graphene and organic pollutants.The experimental results show that: 1)The two antibiotics and the adsorbent have strong interaction in the acidic environment,which promote s the adsorption.From the desorption curve,the release of ofloxacin and norfloxacin in the acidic water is also observed.The rate is lower.The acidic or alkaline environment weakens the interaction between bisphenol A and the adsorbent and inhibits its adsorption.The adsorption force of nitrobenzene and GO is obviously weakened in the acidic environment,and the corresponding adsorption amount is low.RGO may be less affected by the pH of the water due to the less active groups it contains.The analysi s shows that in the organic pollutant-graphene-pHs system,the pH value leads to the change of the adsorbate morphology and affects the ionization degree and adsorption.The electrostatic interaction is the dominant mechanism of adsorption of adsorbate on graphene.2)Under the influence of DOM(HA and FA),the two antibiotics generally showed HA>FA.At the same time,the addition of DOM significantly inhibited the action of nitrobenzene and GO,and the adsorption amount was lower than that of GO alone.The presence of HA has the most obvious effect on the adsorption of BPA by RGO,and the adsorption amount is the lowest.The analysis shows that in the organic pollutant-graphene-DOM system,the hydrogen bonding between the reactive functional groups on DOM and the functional groups such as hydroxyl groups and carboxyl groups on the surface of graphene and EDA occupy the dominant mechanism of graphene adsorption.3)The presence of calcium and magnesium divalent cations in the water environment significantly i mpaired the interaction of four organic pollutants with graphene.The adsorption order was as follows: blank >0.1M>0.25M>0.5M.Analysis shows that in the organic pollutant-graphene-calcium-magnesium ion system,the presence of calcium-magnesium cations causes the oppositely charged graphene colloid to compress the electric double layer,weaken the electrostatic repulsion between the colloids,promote colloidal aggregation and deposition,and agglomerate The effect becomes more pronounced as the ionic strength in the water environment increases.In conclusion,under the influence of physical and chemical properties of water environment,the adsorption of graphene and four kinds of aromatic hydrocarbon organic pollutants of ofloxacin,norfloxacin,bisphenol A and nitrobenzene is the result of simultaneous adsorption mechanisms.Therefore,it is not easy to use a single adsorption mechanism to evaluate the environmental behavior and fate of graphene and organic pollutants.