To account for concentration polarisation on the feed side of the membrane surface during data analysis, the film theory approach was employed. Considering one-dimensional transport of solute to and from the membrane surface at steady-state, and using a single coefficient 𝑘 "# to describe mass transfer through the membrane, the solute concentration at the membrane surface, 𝑐 9("),: , was related to the solute concentration of the feed bulk, 𝑐 9(&),: , as: 𝑐 9("),: -𝑐