Study On Removal Of Ionic Dyes And Cr(?) By Modified Graphene Oxide

Dyeing wastewater is a kind of toxic wastewater which is difficult to treat.It has the characteristics of large total amount,complex content,difficult treatment and heavy economic load to deal with.In 2012,China Environmental Protection Administration and the General Administration of Quality Supervision,Inspection and Quarantine jointly issued the discharge requirements of printing and dyeing wastewater.Due to the difficulty of treatment,the discharge standards of hexavalent chromium were suspended after three years,from the standard that could not be detected to the discharge standard of 0.5 mg/L.The adsorption method is widely used in practical applications because of its high efficiency,easy operation,and reusable adsorbent.Graphene oxide is a new type of carbon material with excellent surface properties,large surface area,abundant surface functional groups,strong intermolecular force and good biocompatibility,etc.Therefore,it can be effectively used as a base material for modification to remove ionic dyes and heavy metal.In this paper,the graphene oxide(GO)was prepared by Hummers method,the PANI/GO adsorbent was modified by polymer modification,and the L-Glu/GO adsorbent was prepared by functional modification of organic small molecules.The study selected the representative methyl orange anion and Cr(?)to adsorb.The effects of pH,adsorbent dosage,reaction time and initial concentration on the adsorption of methyl orange and Cr(?) on the two modified materials were studied.Scanning electron microscopy(SEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and other characterization methods were used to analyze the chemical structure and micro morphology of the two materials,combined with adsorption isotherms and adsorption kinetics.The mechanism of the adsorption of methyl orange and Cr(?) by two modified materials was investigated.The main results are as follows:(1)Using graphene oxide as a base material,synthesizing PANI/GO absorbent by aniline,and studying the adsorption properties of methyl orange and Cr(?) by kinetic model and thermodynamic model.The adsorption process was analyzed.The results showed that the equilibrium adsorption capacity of methyl orange was 103.114 mg/g and the adsorption rate was 93.24% in the single adsorption process.The equilibrium adsorption capacity of Cr(?) is 166.55 mg/g,and the adsorption rate is 99.21%,which can meets the Langmuir isotherm adsorption model and the second-order kinetic equation.(2)L-Glu/GO absorbent were synthesized by using graphene oxide as a base material and L-Glu small molecule modification,and the adsorption properties of methyl orange and Cr(?) were studied.The adsorption process was analyzed by kinetic model and thermodynamic model.The results showed that the equilibrium adsorption capacity of methyl orange was 97.41 mg/g and the adsorption rate was 99.16% in the single adsorption process.The experimental results have a good correlation with the Freundlich isotherm adsorption model.The equilibrium adsorption capacity of Cr(?) is 30.62mg/g,and the adsorption rate is 99.51%,which meets the Langmuir isotherm adsorption model.The adsorption of methyl orange and Cr(?) by LGlu/GO absorbent meets the second-order kinetic equation.(3)Through the characterization of SEM,FT-IR,XRD and XPS,it was found that the preparation of two adsorbents,PANI/GO and L-Glu/GO,was successful made and met the expected target of the experiment.