Opportunities for high productivity and selectivity desalination via osmotic distillation with improved membrane design

Osmotic distillation (OD) membranes offer selectivity based on vapor pressure and therefore highly reject all non-volatile contaminants. Despite the advantage of high selectivity, OD membranes have not been widely implemented due to poor water fluxes and detrimental heat transfer effects. In this study, we use element-and module-scale computational modeling to examine how OD membrane optimization can improve water treatment performance and compare the productivity of simulated OD membrane modules to conventional FO systems. Several OD membrane parameters are optimized, including thickness, thermal conductivity, porosity, and pore diameter. Among the membrane properties explored, we identify that reducing the OD membrane thickness is the most crucial factor in enabling high performance, and a membrane thickness of approximately 0.1 mu m is needed to achieve water fluxes exceeding those of current commercial FO membranes. Thin membranes are also critical to minimize detrimental heat transfer effects in large-scale systems. Comprehensive comparison of OD with FO membranes showed that optimized OD membranes can outcompete high-performance FO membranes in maximum achievable water flux (25.3 vs. 18.6 kg m(-2) h(-1) for OD and FO membranes, respectively) and modulescale water recovery (0.28 vs. 0.18). Overall, the results of this work demonstrate the promise of OD membranes to overcome the selectivity limitations of conventional polymeric membranes and offer guidelines for future OD membrane design.