埃洛石纳米管结构改性后用于Pebax基质中强化气体分离

Nanoporous Structure Derived from Halloysite Incorporated into Pebax Matrix for Gas Separation

基于埃洛石纳米管(HNTs)内外层结构化学性质不同,使用硫酸(H_(2)SO_(4))、盐酸(HCl)对埃洛石进行选择性刻蚀,得到了两种纳米多孔埃洛石,即S-HNTs和H-HNTs。将这两种纳米多孔埃洛石引入Pebax MH 1657(Pebax)基质中制备混合基质膜(MMMs)。纯CO_(2)、CH_(4)气体渗透结果表明,在S-HNTs和H-HNTs填充量分别为6%(质量分数)和8%(质量分数)时,Pebax-S-HNTs MMMs和Pebax-H-HNTs MMMs性能达到最优,与纯Pebax膜相比,CO_(2)渗透系数分别增加了97.8%和125.3%,CO_(2)/CH_(4)的理想分离因子分别增加了69.7%和40.0%。气体分离性能的改善主要是由于HNTs的刻蚀扩孔成功以及微/介孔分级多孔结构的存在。这是因为,首先,对HNTs内[AlO 6]八面体进行选择性刻蚀导致管腔尺寸增加,提高了气体渗透;其次,微/介孔分级多孔结构的存在为气体扩散提供了多种传递路径,曲折路径的存在促进了气体选择性的提高。

Two kinds of modified materials,S-HNTs and H-HNTs,were obtained by selective etching of halloysite with sulfuric acid(H_(2)SO_(4))and hydrochloric acid(HCl)based on the different chemical properties of the inner and outer structures of halloysite nanotubes(HNTs).And the two different nanoporous structure derived from HNTs were incorporated into Pebax MH 1657(Pebax)to make mixed matrix membranes(MMMs).The pure CO_(2)and CH_(4)gas permeability results showed that,Pebax-S-HNTs MMMs and Pebax-H-HNTs MMMs had the best gas permeation performance when the filling amount was 6wt%and 8wt%,respectively.Compared with pure membrane,the permeability of CO_(2)in Pebax-S-HNTs MMMs and Pebax-H-HNTs MMMs increased by 97.8%and 125.3%respectively,and the separation factor of CO_(2)/CH_(4)increased by 69.7%and 40.0%respectively.The improvement of gas separation performance is mainly due to the successful pore expansion of HNTs and the existence of micro/mesoporous graded porous structure.Firstly,the selective etching of HNTs results in the increase of the cavity size of HNTs and which makes the increase of gas permeability;secondly,the existence of multi-layer micro/mesoporous multi-stage pore structure provides a variety of transmission paths for gas diffusion,and the existence of zigzag paths promotes the increase of gas selectivity.