A trimethylamine-carbon dioxide draw solution for osmotic engines

This study evaluates the pressure retarded osmosis performance of TMA-CO2 for potential use in osmotic heat engines. Power densities up to 18.6 W m(-2) were achievable at relatively low pressure (10 bar) using 5 M TMA-CO2 draw solutions. Compared to NaCl control tests, the TMA-CO2 exhibited 20% lower water flux due in large part to its larger molecular size and associated higher solution viscosity and lower diffusion coefficient. Compared to the ammonia-carbon dioxide draw solution, water flux was comparable but reverse solute flux of TMA-CO2 was nearly one order of magnitude lower. Larger solute size was found to create a performance tradeoff as reduced reverse solute flux improved water flux while higher viscosity and lower diffusion coefficient worsened water flux. (c) 2018 American Institute of Chemical Engineers AIChE J, 64: 3369-3375, 2018