Baoyu Wang

Novel Protic Ionic Liquid Composite Membranes with Fast and Selective Gas Transport Nanochannels for Ethylene/Ethane Separation

Protic ionic liquids (PILs) were utilized for the fabrication of composite membranes containing silver salt as the C2H4 transport carrier to perform C2H4/C2H6 separation for the first time. The intrinsic nanostructures of PILs were adopted to construct fast and selective C2H4 transport nanochannels. The investigation of structure-performance relationships of composite membranes suggested that transport nanochannels (polar domains of PILs) could be tuned by the sizes of cations, which greatly manipulated activity of the carrier and determined the separation performances of membranes. The role of different carriers in the facilitated transport was studied, which revealed that the PILs were good solvents for dissolution and activation of the carrier due to their hydrogen bond networks and waterlike properties. The operating conditions of separation process were investigated systemically and optimized, confirming C2H4/C2H6 selectivity was enhanced with the increase of silver salt concentration, the flow rate of sweep gas, and the feed ratio of C2H4 to C2H6, as well as the decrease of the transmembrane pressure and operating temperature. Furthermore, the composite membranes exhibited long-term stability and obtained very competitive separation performances compared with other results. In summary, PIL composite membranes, which possess good long-term stability, high C2H4/C2H6 selectivity, and excellent C2H4 permeability, may have a good perspective in industrial C2H4/C2H6 separation.

Preparation of poly(L-lactic acid) membrane from solvent mixture via immersion precipitation

ABSTRACT Poly (L-lactic acid) (PLLA) membranes were fabricated through immersion precipitation method. 1, 4-dioxane (DX), N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethyl-acetamide (DMAc), and DX/NMP, DX/DMF and DX/DMAc were used as solvents severally. With a focus on the PLLA/DX/NMP/H2O system, the effect of solvent mixture on PLLA membrane was investigated by altering the ratio of DX/NMP. Various membrane morphologies were obtained, which were further correlated by mean of solubility parameter and viscosity of casting solution. It was found that the membrane cast with DX/NMP (1/1) exhibited ideal structure and better performance compared with membranes cast with same concentration of PLLA.