乳液法制备石墨烯气凝胶及其吸附水中亚甲基蓝

Fabrication of graphene aerogels by emulsion method and their adsorption of methylene blue

利用乳液法制备多孔石墨烯气凝胶(em GA),改变乳液油水比制备不同的em GA。扫描电子显微镜(SEM)、傅里叶红外光谱(FTIR)、氮气吸附脱附等表征显示,em GA具有多孔结构,经水热还原后含氧官能团大部分被除去,比表面积为103.3~243.1m^2/g。以亚甲基蓝(MB)浓度和温度作为变量,考察em GA对水中MB的吸附效果。结果表明,em GA的比表面积越大,其对MB平衡吸附量越大;当初始浓度越大,温度越高,则吸附有利。吸附动力学数据表明em GA吸附MB符合准二级动力学模型和内扩散模型,吸附过程分为大孔扩散和微孔扩散。吸附等温线数据拟合结果符合Langmuir模型,表明em GA对MB的吸附属于单分子层吸附。Langmuir模型计算出em GA-2饱和吸附量为307.7mg/g,与实验值291.3mg/g较为接近。分析热力学参数发现,em GA吸附MB为自发吸热过程,且吸附过程属于物理吸附。

Porous graphene aerogels（em GA） were fabricated using emulsion method. Different em GA were prepared through changing the emulsion oil/water ratio. Analysis of scanning electron microscopy（SEM）, Fourier transform infrared spectroscopy（FTIR） and nitrogen adsorption showed that em GA had porous structure with specific surface areas of 103.3 — 243.1 m^2/g. Most oxygen-containing functional groups were removed after hydrothermal reduction. The adsorption of em GA to MB in water was investigated by changing the methylene blue（MB） concentration and temperature. The results indicate that the larger the specific surface area of em GA, the greater the equilibrium adsorption capacity of MB. High initial MB concentration and temperature are beneficial for the adsorption of em GA. The adsorption kinetics is well described by the pseudo second-order and intra-particle diffusion models, and the adsorption process can be divided into macropore diffusion and micropore diffusion. The adsorption isotherm data are well fitted by the Langmuir model, indicating that MB adsorption belongs to single molecular layer adsorption. Large specific surface area is favorable for the MB adsorption on em GA. The saturated adsorption capacity of em GA-2 is 307.7 mg/g, given by the Langmuir model, which is to the experimental value of 291.3 mg/g. Analysis of the thermodynamic parameters shows at the adsorption of MB on em GA is a spontaneous endothermic process, and belongs to physical adsorption.