Information on the effect of membrane characteristics on the performance of nanofiltration membranes during processing of concentrated sodium chloride solutions is scarce. This hampers membrane selection for these applications. In this study nanofiltration membranes, ranging from very tight to very open, have been evaluated for processing of sodium chloride solutions obtained from solution mining. Sulfate retention of these membranes is inversely related to their pore radius obtained from membrane characterization. The chloride retention during nanofiltration of practically saturated salt solutions is a function of the sulfate concentration difference between concentrate and permeate. The observed relation is explained by the small sodium chloride chemical potential difference between concentrate and permeate, indicating low membrane resistance for sodium chloride transport. This is concluded from the sodium chloride concentration product ratios of permeate over concentrate, which were found to be between 0.9 and 1 for all membranes evaluated. This ratio is proportionally related to the membrane pore radius obtained from characterization. Based on the results the sulfate and chloride retention of nanofiltration membranes for processing of saturated sodium chloride solutions can now be obtained from a simple characterization experiment.
Bargeman, G., Westerink, J. B., Manuhutu, C. F. H., & ten Kate, A. (2015). The effect of membrane characteristics on nanofiltration membrane performance during processing of practically saturated salt solutions. Journal of membrane science, 485, 112-122. https://doi.org/10.1016/j.memsci.2015.03.039