Application of PIM-1 for solvent swing adsorption and solvent recovery by nanofiltration

A concept is demonstrated for the separation of two organic solutes from a common solvent by solvent swing adsorption (SSA), coupled with organic solvent nanofiltration (OSN) for solvent recycling. The polymer of intrinsic microporosity PIM-1 was utilized both for the adsorbent and for the nanofiltration membrane. For adsorption from solution in ethanol or water-ethanol (30170) mixture, PIM-1 showed high affinity for a neutral solute (Oil Red 0) with negligible uptake of an anionic solute (Remazol Brilliant Blue R). The obtained equilibrium values of distribution coefficient K revealed that Oil Red 0 can be concentrated in PIM-1 by 4300 times from its ethanol solution, and this value can be significantly improved up to 53,000 times in the case of water/ethanol (30/70) binary mixture. Such difference in the affinity of neutral solute to PIM-1 was explained by means of competitive sorption between solute and solvent molecules, and a clear relationship between distribution coefficient K and solvent solubility parameter was observed. The adsorbent could be regenerated by washing with a less polar solvent (toluene), which gave almost quantitative desorption of the neutral solute (K = 6). PIM-1 membranes as cast and after cross-linking were also successfully utilized for solvent recovery. It was demonstrated that PIM-1 membranes can possess either solvent-selective transport or solute-selective transport in OSN, depending on the nature of the solvent. (C) 2015 Elsevier B.V. All rights reserved.