部分还原氧化石墨烯-Fe_3O_4对水中Mn(Ⅱ)的快速去除

Fast Removal of Aqueous Mn(Ⅱ) Using Partially Reduced Graphene Oxide-Fe_3O_4

采用改进的Hummers法制备了氧化石墨烯(GO),继而用一步共沉淀法制备了部分还原氧化石墨烯-四氧化三铁复合物(PRGO-Fe_3O_4).采用X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、X射线能量色散光谱(EDX)、高分辨透射电子显微镜(HRTEM)、选区电子衍射(SAED)及傅里叶变换红外光谱(FTIR)等技术对其进行了分析表征;考察了p H值、接触时间、吸附材料用量、共存物质、GO的还原、循环使用次数等因素对Mn(Ⅱ)吸附行为的影响.结果表明,PRGO-Fe_3O_4中Fe_3O_4颗粒分布均匀,大小为15~20 nm,剩磁和矫顽力均很小.因Fe_3O_4颗粒的锚定作用,石墨烯片层很薄,使PRGO-Fe_3O_4对Mn(Ⅱ)表现出高效的吸附性能和良好的循环使用性能:当p H=7、PRGO-Fe_3O_4用量为500 mg/g时,对201.3211 mg/L的Mn(Ⅱ)溶液仅3 min即达吸附平衡,吸附率和吸附量分别为99.35%和404.49 mg/g,磁分离仅需10 s,经5次循环吸附后,容量保持率为首次的78%.机理与热力学研究结果表明,吸附为吸热、自发的单层化学吸附.

Partially reduced graphene oxide-Fe3O4composite（ PRGO-Fe3O4） was prepared by one step coprecipitation onto graphene oxide（ GO） synthesized by modified Hummers method. The as obtained composite was characterized by XRD,FESEM,EDX,HRTEM,SAED,XPS and FTIR. The impact of p H,contact time,dosage,foreign substances,reduction of GO and cycle times on the adsorption performance of the composite towards Mn（ Ⅱ） were investigated and the dsorption isotherm,thermodynamics and kinetics were analyzed. The results indicate that Fe3O4 distribute evenly and uniformly in the as-obtained composite,with a fine particle size of 15—20 nm,resulting in a low remanence and coercivity. The composite shows efficient adsorption property and good recycability towards aqueous Mn（ Ⅱ） owing to the thin GO sheets in its structure caused by the anchoring effect of Fe3O4. Adsorption equilibrium was reached within 3 min with the adsorption percent and capacity of 99.35% and 404.49 mg / g,respectively,under the conditions of p H = 7,dosage 500 mg / L,and initial concentration of Mn（ Ⅱ） of 201.32 mg / L,with the subsequent magnetic separation taking only 10 s. After five consecutive cycles,the adsorption capacity of the composite remians 78% that of the first cycle. Analyses on the mechanism and thermodynamics show that the adsorption is an endothermic,spontaneous and monolayer chemical adsorption step.