介孔SiO_2/膨胀石墨复合材料的直接合成及其对染料的吸附性能

Direct synthesis and adsorption performance of a mesoporous SiO_2/expanded graphite composites

采用简单的一步水热合成法,在含有模板剂、铝盐、膨胀石墨和硅源的水溶液中,利用铝盐水解后所产生的弱酸性环境,直接制备出介孔SiO_2/膨胀石墨复合材料,考察了铝盐的添加量对所得复合材料结构和性能的影响。采用XRD、N_2吸附和SEM对介孔SiO_2/膨胀石墨复合材料的结构和形貌进行了表征。以亚甲基蓝为目标污染物分子,系统评价了复合材料的吸附性能。结果表明,合成时铝盐的添加量在很大范围内变化(r_(Al/Si)=0.25~2.0,体系pH值为3.1~2.3)均可获得具有较大比表面积和孔体积的介孔SiO_2/膨胀石墨复合材料,且介孔SiO_2以多层膜的形式生长在膨胀石墨碳层上;当r_(Al/Si)=0.25、0.5、1.0时,复合材料孔道有序规整;当rAl/Si=1.0、2.0时,复合材料中介孔孔道规整性下降。介孔SiO_2/膨胀石墨复合材料吸附亚甲基蓝的饱和吸附量在52~55mg·g^(-1)左右,吸附行为主要符合Langmuir方程和伪二级动力学模型。

A series of mesoporous SiO2/expanded graphite（EG）composites were directly synthesized via a facile one-step hydrothermal method in aqueous solutions that contain templates,aluminum salts,expanded graphite and siliceous source.The weak acid environment of reaction solutions were self-generated by the aluminum salts.The effects of the added amount of aluminum salt in the reaction system on the structures and properties of the obtained composites were carefully investigated.The structures and morphologies of the composites were characterized by XRD,N2 physisorption and SEM techniques.Methylene blue（MB）was used as a probe pollutant molecule to systematically evaluate the adsorption properties of the composites.The results show that all mesoporous SiO2/expanded graphite composites have large surface areas and high pore volumes,and they can be prepared by using aluminum salts in a wide range of r（Al/Si）=0.25-2.0（pH =3.1-2.3）.It is further observed that multi-layered mesoporous SiO2 membranes are grown onto the carbon flakes of expanded graphite in SiO2/EG composites.Those SiO2/EG composites synthesized with rAl/Siof 0.25,0.5 and 1.0 have well-ordered mesoporous while those synthesized with rAl/Siof 1.5 and 2.0 have less-ordered mesoporous.Mesoporous SiO2/EG composite adsorption capacity in 52-55mg·g-1,and the adsorption behavior is mainly in accordance with the Langmuir equation and pseudosecond-order kinetic model.