(399j) Ethanolamine Separation By Nanofiltration: A Molecular Simulation Study

Biomass is an abundant resource of renewable feedstock on the Earth and there has been increasing interest to convert biomass into fuels and valuable chemicals (e.g. C, H, and O-based bioethanol, sugar alcohals/polyols, furan and organic acid). Nevertheless, nitrogen-containing chemicals are often more valuable and widely used in pharmaceuticals, textiles and many more. Particularly, ethanolamine (ETA) is extensively being used for scrubbing acidic gases and as an important feedstock in the production of detergents, emulsifiers, pharmaceuticals, chemical intermediates, etc. After the conversion of biomass, however, the solution usually contains ETA, ammonia (used as a nitrogen source during conversion), as well as a large amount of water. Traditional separation using thermal distillation is energy intensive and may decompose ETA. In this context, the technically feasible and economically viable separation of ETA is highly desirable. Herein, we report a molecular simulation study to investigate the separation of ethanolamine (ETA) by nanofiltration (NF) through a polymer of intrinsic microporosity (PIM-1) and two activated carbon membranes namely curved corannulene (CRNL) and curved corannulene functionalized with hydroxylic groups CRNL-(OH)₂. The hierarchy of water flux and permeability through the membranes are CRNL-(OH)₂ > PIM-1 > CRNL. Due to the hydrophilic nature, CRNL-(OH)₂ possesses the highest water flux and permeability compared to the other two. Along with higher water permeation, 100% ETA retention is obtained through CRNL-(OH)₂, indicating its suitability for ETA separation. The survival time-correlation function (STCF) of water around the non-accessible atom of the PIM-1 membrane shows a remarkably faster decay than around the easily accessible atom. The STCF of water in hydrophilic membrane shows a slower decay than in hydrophobic counterpart. Further, the life time of water hydrogen bonds within the membranes follow the reverse trend to water flux. The simulation study provides microscopic insight into the structural and separation properties of ETA through the NF membranes, and suggests that CNRL-(OH)₂ membrane is an interesting candidate for ETA separation.