Figure 3: Decrease of the normalized permeate flux with increasing feed recovery rate (VP/VF) for three successive nanofiltration steps in a dead-end stirred cell (25°C, 35 bar) using the NF-270 membrane. Permeate from the first step was used as feed for the second step, while permeate from second step was used as feed for the third step. The wastewater contained a mixture of IM14 Cl and IM14 1COO.