| In this paper,the graphene oxide-based magnetic composites were all prepared by different method for the adsoption of typical pollutants from aqueous solution.Magnetic graphene oxide?MGO?was modified to remove methylene blue?MB?.Zirconium?IV?-loaded magnetic chitosan graphene oxide?Zr-MCGO?was used to remove alizarin red?AR?and F–.Iron???-loaded magnetic chitosan graphene oxide?Fe-MCGO?was synthesized to remove sulfosalicylic acid?SSA?.Characterizations of the materials before and after modification were performed using several techniques such as point of zero charge(pHpzc),fourier transform infrared spectroscopy?FT-IR?,raman spectroscopy?Raman?,scanning electron microscopy?SEM?,Brunauer-Emmett-Teller?BET?,vibrating-sample magnetometry?VSM?and X-ray photoelectron spectroscopy?XPS?,which demonstrated the modified materials are successful.In addition,the effect of adsorbent dose,solution pH,common salt concentrations,adsorbate concentration and contacting time were systematically investigated.Isotherm,kinetics and thermodynamics analyses were studied.XPS analysis of adsorbents before and after adsorption was carried out for further discussing the mechanism of the adsorption process.From the study of batch adsorption of MB by MGO,it was demonstrated that the maximum adsorption capacity at 313 K could reach up to 62.7 mg/g.The optimal pH was 9 and the salinity was disadvantageous of MB adsorption.The Equilibrium adsorption data were best fitted by Koble-Corrigan model.The Elovich kinetic model could be used to describe the process of MB adsorption.And the thermodynamic analysis showed that the adsorption process was spontaneous,endothermic and entropic-increasing.Furthermore,MB-loaded MGO could be reused in a secondary adsorption for the removal of congo red.And the HCl solution of pH 3 had relatively better desorption and regeneration capacity for MB adsorption on MGO.The results of adsorption of AR and F–by Zr-MCGO showed that the adsorption capacity had a negative effect with the increase of the initial pH value;the increase of temperature had a positive effect on AR and F–adsorption;ionic strength had little effect on AR adsorption,but was disadvantaged to F–adsorption.The isotherm model of Freundlich could be used to describe the adsorption process of AR by Zr-MCGO,whereas the models of Temkin?Redlich-Peterson and Koble-Corrigan were suitable for F–.The maximum adsorption capacity of AR and F–by Zr-MCGO were 224 mg/g and 6.10 mg/g at 313 K,respectively.The results of kinetic fitting analysis showed that the adsorption process of the two kinds of adsorbates could be described by Elovich equation.The thermodynamic analysis data indicated that the adsorption process were spontaneous,endothermic and entropy-increasing adsorption processes.The best solution for desorption and regeneration of AR and F–were 0.01 mol/L NaOH and 0.01 mol/L NaHCO3,respectively.The competitive adsorption of AR and acid chrome blue K?AK?showed that Zr-MCGO had preferential adsorption on AR.The adsorption using Fe-MCGO to adsorb SSA indicated that pH value was better under acidic condition,salinity had a negative effect on the adsorption process,and the increase of temperature was not conducive to the adsorption process.The best fitting model for isotherm analysis was Koble-Corrigan,and the maximum adsorption capacity was 135 mg/g at 293 K.The Pseudo-first-order kinetic model could describe the adsorption process well.From the thermodynamic data,it could be concluded that the adsorption process was a spontaneous,exothermic and entropy-increasing adsorption process.The desorption and regeneration of SSA adsorbed by Fe-MCGO in 0.01 mol/L NaOH solution was better,and could be reused for many times.The results showed that the adsorption of contaminants by graphene oxide-based magnetic composites were mainly due to electrostatic attraction,?–?interactions with MB,AR and SSA with aromatic rings,complexation between AR and F–after modification with Zr?IV?,and hydrogen bonds and van der Waals force.This topic provided a basis for the application of magnetic graphene materials. |
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