Adsorption Of Phosphorus Flame Retardant On Graphene From Wastewater

With the rapid development of the modern industry,a large amount of wastewater containing phosphorus flame retardants were discarded into the environment,which has endangered human body heath.Among many methods of treating phosphorus flame retardant,adsorption technique is widely used due to its many advantages,such as simple operation process,high treating efficiency,low energy consumption and no secondary pollution.High adsorption capacity,low cost and nature stable adsorbents make the key point of adsorption method.In fact,grapheme has been widely used in the field of adsorption because of its unique and excellent adsorption properties since its discovery.In this study,graphene oxide and graphene were prepared by modified Hummers method.X-ray diffraction(XRD),Raman spectroscopy(Roman),Fourier transform infrared spectroscopy(FTIR)and BET were used to characterize the adsorbents.The adsorption properties of several phosphorus flame retardants on graphene materials and several other adsorbents were also studied by batch adsorption experiments and the adsorption dynamics behaviors,thermodynamic behaviors and dynamic adsorption behaviors were explored as well.The main results are as follows:(1)Comparison of adsorption properties of tributyl phosphate on graphene oxide(GO),single-walled carbon nanotubes(SWCNT),actived carbon(AC)and graphene(G)in aqueous solution shows that G has a higher adsorption capacity than the three other adsorbents.The effects of temperature,contact time,pH and initial concentration of TBP on the adsorption properties of graphene were investigated,indicating that the adsorption capacity increases with the increasing initial concentration,pH and temperature.The adsorption isotherms of the four adsorbents were studied,and the results show that compared with Freundlich model,Langmuir model is better to describe the adsorption isotherms with relative higher R2,indicating experimental data were well described by the Langmuir isotherm model.The kinetic data of four adsorbents were fitted to pseudo-second order kinetics.In addition,the adsorption process was an endothermic and spontaneous process.(2)Comparison of adsorption properties of tributyl phosphate on graphene oxide(GO)and graphene(G)in aqueous solution shows that G has a higher adsorption capacity than GO.With the contact time,initial concentration of TCP and temperature increased gradually,the adsorption capacity of adsorbents increased;humic acid had a significant effect on adsorption,and metal ions had little effect on adsorption.The adsorption dynamics data of the two adsorbents were fitted to pseudo-second order kinetics,and the equilibrium data were fitted well with the Langmuir isotherm model.The adsorption process was an endothermic and spontaneous process.(3)Dynamic adsorption was investigated using graphene.The effects of different adsorption conditions,such as column height,initial concentration of wastewater and operating flow rate,on the dynamic adsorption of TCP were studied.The results show that the breakthrough generally occurred earlier with higher flow rate and breakthrough time reaching saturation was increased significantly with a decrease in the flow rate;it was obvious that the breakthrough time decreased with increasing influent TCP concentration;the time of breakthrough extended with increasing the filling height of adsorbent.In addition,the Thomas model described breakthrough data of TCP on G bed well.