Adsorptive Function For U(?) And Cu(?) By The L-glutamic Acid-functionalized Graphene Oxide

With the development of industry,the total amount of copper and uranium wastewater is increasing,which poses a huge threat to the natural environment and human beings.How to deal with heavy metal wastewater has become an urgent problem to be solved.The adsorption method in the treatment of heavy metal wastewater has attracted much attention due to its rapid economy,simplicity and high efficiency.Graphene oxide(GO)is a carbon material with a rich functional group on its surface,which makes it easy to adsorb with heavy metals.However,it has good hydrophilicity,and it is highly prone to agglomeration in aqueous solution to affect the adsorption effect.In order to solve this problem and increase the adsorption capacity,it is often functionally modified.In this study,graphene oxide(GO)was prepared by graphite using Hummers method,and modified with green non-polluting material such as L-glutamic acid.At the same time,the structure was characterized by infrared spectroscopy,scanning electron microscopy and X-ray diffraction.L-glutamic acid functionalized graphene oxide(L-Glu/GO)was used to adsorb uranium and copper.The pH and adsorption were investigated.The effects of time,initial concentration,dosage and temperature on the adsorption effect;the adsorption process was fitted using different kinetic and thermodynamic models.The main findings are as follows:(1)The graphene oxide(GO)synthesized by the Hummers method was functionalized with L-glutamic acid to obtain L-Glu/GO,and the FTIR analysis showed that the reaction between them was L-glutamic acid.The amino group attacks the nucleophilic reaction of the epoxy group on GO.XRD indicates that the crystal structure of GO changes greatly after functionalization.SEM indicates that there is a large amount of gully on the surface of L-Glu/GO,which is an important reason for its efficient adsorption of heavy metals.(2)The static adsorption test of uranium by L-Glu/GO showed that the optimum pH of L-Glu/GO for U(?)adsorption was 4,the optimal dosage was 0.2g/L,and the adsorption reaction reached equilibrium for 40 minutes.The influence of temperature on adsorption is negligible,and the maximum adsorption capacity can reach 309.36mg/g.The adsorption process accords with quasi-secondary kinetics and Langmuir isotherm equation,and the adsorption reaction is dominated by single-layer adsorption.(3)The static adsorption test of copper by L-Glu/GO showed that the optimal pH of adsorption of Cu(?)by L-Glu/GO was 6,the optimal dosage was 0.25g/L,and the adsorption reaction reached equilibrium for 30 minutes.The effect of temperature on adsorption is negligible,and the maximum adsorption capacity can reach 292.45 mg/g.The adsorption process accords with quasi-secondary kinetics and Langmuir isotherm equation.(4)L-Glu/GO has better selective adsorption of uranium in the competitive adsorption of copper and uranium.Copper and uranium can inhibit the adsorption performance of L-Glu/GO.(5)The adsorption-desorption test indicates that L-Glu/GO can be desorbed by HCl for reuse and has high application value.