Preparation And Adsorption Properties Of GO-4A Zeolite Composites

Heavy metal wastewater has become one of the major global concerns due to its large amount of water,long-term toxic effects,complexity,dynamics,diversity of transformation and migration,locality of pollution and biodegradability.The adsorption method has become a research hotspot in the field of heavy metal wastewater treatment in recent years due to its wide material source,simple operation,high selectivity and low cost.Graphene oxide(GO)is a promising adsorbent material.In addition to its excellent hydrophilicity,mechanical properties and electrical properties,its structure is rich in a large number of oxygen-containing functional groups as a binding site for nanoparticles.The huge specific surface area makes the application of GO in water treatment attract the attention of researchers.However,GO is easy to stack between layers due to the inter-layer van der Waals force,which greatly limits its application in real life.4A zeolite is a three-dimensional skeleton-like structural compound composed of silicon oxide and aluminum oxide tetrahedron,which belongs to cubic crystal system and has high ion exchange capacity and specific surface area.In this study,a GO-4A zeolite composites was prepared by ultrasonic and magnetic stirring green and environmentally friendly processes,by X-ray diffraction(XRD),scanning electron microscopy(SEM),and Fourier transform infrared spectroscopy(FTIR).The thermogravimetric analysis(TG)instruments were used to characterize it,and the adsorption properties of Cu2+ and Pb2+ in water were investigated.(1)The structure and morphology of GO-4A prepared by different composite ratios were analyzed by XRD,FTIR and SEM.The results show that different compounding ratios have little effect on the phase composition of GO-4A;the addition of 4A zeolite will reduce the degree of agglomeration of graphene oxide.As the composite ratio increases,the thermal stability of the composites increases continuously;when graphene oxide and the composite ratio of 4A molecular sieve is1:5,the composite effect is the best;and at room temperature,when the solution p H =6,the removal efficiency of copper ions can reach to 95.42%.So we chose a composite ratio of 1:5 for the subsequent experiments.(2)The optimal adsorption conditions of GO-4A were investigated by single factor experiment,orthogonal experiment and response surface analysis.The resultsshowed that the optimum adsorption conditions for Cu2+ were p H 5.52,the dosage was 0.23 g,and the initial concentration of the solution was 76.73mg/L.The optimum adsorption condition of Pb2+ for the composite was 4.97.The dosage was 0.33 g,and the initial concentration of the solution was 154.2 mg/L.(3)The adsorption mechanism of GO-4A was investigated by adsorption isothermal adsorption kinetics model.The results showed that the adsorption of Cu2+and Pb2+ by GO-4A nanocomposites was consistent with Langmuir model and Freundich model,and the maximum adsorption capacity were 48.78mg/g and 142.87mg/g.Both of them have the best correlation with the quasi-secondary reaction rate model.physical and chemical adsorption exist simultaneously in the adsorption process,and chemical adsorption is dominant.It is inferred that a hydrogen bond,the aπ-π conjugation,and an electrostatic interaction are formed between the GO-4A nanocomposite and metal ions.