Fig. 2: Results of characterization experiment performed with representative seawater reverse osmosis membrane, SW-1, at near 0% recovery rate.
a Water flux as a function of time, showing the various phases and steps. Phase 1 with deionized water as feed solution; phase 2 with 32 g/L NaCl as feed solution (pH 8.0). The fitting line goes through the origin, i.e., no flux at no applied pressure. Empty circles in phase 2 refer to stabilization periods upon changes in feed pressure or cross-flow velocity. b Average of flux data measured in the various phases and steps at steady-state, as a function of applied feed pressure; note that the y axis has a break from 18 to 28 Lm−2 h−1 (LMH). c Average of (bottom) observed rejection (%) and (top) concentration polarization modulus, computed for the various steps in phase 2, as a function of applied feed pressure. Note that the y axis of the inset related to the observed rejection has a break from 97.6 to 98.4%. In all graphs, gray circles refer to deionized water as feed solution, downward blue triangles to steps with saline feed solution and feed pressure of 55 bar, upward green triangles to steps with saline feed solution and feed pressure of 45 bar, red squares to a step with feed pressure of 35 bar and low cross-flow velocity. For the two higher pressure values, colored symbols refer to high cross-flow velocity while empty symbols to medium cross-flow velocity. Values plotted in b are averages of individual flux values observed during at least 20 mins of operation, all under steady-state conditions. Values plotted in c are averages of three individual rejection values, and the averages of the respective values of the concentration polarization modulus, obtained for each step under steady-state conditions. Error bars represent one standard deviation of each of those data samples. The temperature was kept constant at 23 ± 0.5 ∘C.
