(709f) Crosslinked Mixed Matrix Polyimide Membranes Surface-Modified By Amine Vapor for Organic Solvent Nanofiltration

The modification of a cross-linked mixed matrix polyimide membrane substrate by tris (3-aminopropyl) amine (TAPA) vapor is performed in this work to modify its surface properties for organic solvent nanofiltration (OSN). The TAPA modification is found to increase the surface hydrophilicity and narrow the pore size of the membrane to make it suitable for OSN applications. The effects of the temperature and time of TAPA vapor treatment are investigated. The newly developed TAPA-modified OSN membranes demonstrate good stability in various solvents (water, methanol, ethanol, isopropanol, dimethylformamide, tetrahydrofuran and hexane) and the permeances of these solvents are found to be proportional to the products of their solubility parameters, molar volumes and viscosities (δ_{p, s} MV_s^-1η_s^-1). The study illustrates that the optimal composite membrane retains more than 90% for dyes with a molecular weight higher than 828 gmol^-1 in isopropanol. Moreover, compared with neutral and negatively charge solutes, TAPA-modified membranes show impressive higher rejections towards positively charged dyes possibly because of electrostatic repulsion (e.g., Donnan exclusion). 14-day tests are also conducted to separate Rose Bengal (Mw= 1017 gmol^-1) from isopropanol/dye solutions, both the fluxes and rejections of membranes do not fluctuate significantly. These findings indicate that amine vapor modification is an advantageous technique to develop next-generation OSN membranes for in food and pharmaceutical industries applications.