The influence of sodium chloride on mass transfer in a polyamide nanofiltration membrane at elevated temperatures

The influence of temperature (20–50 °C) and NaCl on mass transfer of pure water and glucose solution (0.0055 M) using an Alfa Laval NFT-50 nanofiltration membrane has been investigated. Addition of 0.017 M NaCl(aq) increased the membrane permeability in comparison to measurements with pure water. Performing cyclic temperature variations using a membrane pre-treated with 0.20 M NaCl(aq) caused the membrane permeability to decrease for each time a new maximum temperature was reached. After NaCl pre-treatment, the relative flux decline measured over 4 h was found to be greater for glucose than for water, and the rate of the flux decline for both water and glucose increased with temperature (20–50 °C). The permeability was found to be unaffected by the pressure if the membrane had previously been rinsed at a lower pressure but at a higher temperature. Changes in permeability due to the presence of NaCl could be related to interactions in the active polymer layer of the membrane. MgCl2 pre-treatment influenced the membrane permeability less that NaCl pre-treatment.