Study On The Adsorption Behaviors Of Polycyclic Aromatic Hydrocarbons On Magnetic Graphene Oxide

With the rapid development of industrialization and urbanization,an increasing number of pollutants are released into the environment,cause significant water environmental pollution.Polycyclic aromatic hydrocarbons(PAHs)constitute a group of persistent organic pollutants(POPs),that physical-chemical properties are very stable and widely distributed in the environment,presenting inestimable threats to the ecological environment and human health.Among the techniques for the removal of PAHs from aqueous solutions,adsorption has been proved to be one of the most suitable methods.As a layered two-dimensional material,magnetic graphene oxide has attracted increasing attention as an adsorbent owing to its abundant functional groups and the resulting adsorption sites.Various PAHs are present at the same time in a water environment.Most previous studies have focused on adsorption behaviors of a single pollutant,limited progress has been made for the adsorption behaviorsof multiple pollutants,the mechanism of its action needs to be elucidated further.Adsorption of phenanthrene(Phe),fluoranthene(Flu)and pyrene(Pyr)in a single solute system and its influencing factorsMagnetic graphene oxide(MGO)was synthesized by the chemical co-precipitation method and the adsorption behaviors of Phe,Flu,and Pyr on the graphene surface were studied.The results show that the removal rate of Phe,Flu,and Pyr were positively associated with MGO dosage and the equilibrium adsorption capacity was negatively associated with MGO dosage.The Zeta electric potential of MGO has been depressed due to the rise of pH,which causes the aggregate of MGO so that reducing the removal rate of Phe,Flu,and Pyr.The kinetic experiment results show that the order of equilibrium adsorption capacity of Phe,Flu,and Pyr on MGO was:Flu>Pyr>Phe,the order was consistent with its hydrophobicity(Kow),that indicating that hydrophobic interaction is an important adsorption force.The adsorption equilibria of Phe,Flu,and Pyr on MGO were almost reached within 1 h and the pseudo-second-order kinetic model was more suitable to describe the adsorption process.These implied that the overall rate of the adsorption process was controlled by the chemisorption.The adsorption isotherm experiment shows that the Dubinin-Astakhov isotherm model fits well,and the adsorption sites of Phe,Flu,and Pyr on MGO may vary.The adsorption thermodynamics shows that the adsorption of Phe,Flu,and Pyr on MGO were spontaneous processes at low concentrations and the initial concentration of PAHs will affect its adsorption thermodynamic properties.Adsorption behaviors and Mechanism of Phe,Flu,and Pyr in multi-solutes System.Phe,Flu,and Pyr show strong competitive adsorption behaviors on MGO in the multi-solutes system.The more similar the molecular structure,the closer the molecular size,the stronger the competition Adsorption of Phe,Flu,and Pyr on MGO is mainly surface adsorption,and the main adsorption forces were hydrophobic interaction and π-π interaction.Dubinin-Astakhov isotherm model fits well.The values of E and b fitted by the DA model were all approached 5.71 kJ/mol and 1,respectively.The values of n fitted by the Freundlich model were all tended to 1.Both of these results indicate that the isotherms of the multi-solutes system tend to be linear.The adsorption of phenanthrene,fluoranthene and pyrene on MGO can be multi-layered.The energy of the adsorption sites on the surface of MGO tends to be uniform after adding competitive solutes,that resulting in the adsorption isotherms of multi-solute systems tending to be linear.