Rejection of ammonium and nitrate from sodium chloride solutions by nanofiltration: Effect of dominant-salt concentration on the trace-ion rejection

Abstract

In this work, the rejection of two ions associated with fertilizer pollution of ground water (NH4and NO3) by a polyamide nanofiltration (NF270) membrane was studied. Sodium chloride was selected as the dominant salt and the effect of its concentration on the NH4 and NO3 rejections was evaluated. Filtration experiments were carried out in a cross-flow setup with a rectangular spacer-filled feed channel. The solution-diffusion-electro-migration-film model (SDEFM), previously developed to model the pressure-driven trans-membrane transfer of electrolyte mixtures consisting of a single dominant salt and (any number of) trace ions, was used to obtain membrane ion permeance from the experimental data. In this way, the membrane permeances with respect to single ions (Na,Cl,NH4,NO3) were obtained for various concentrations of both dominant (0.05–0.3 M NaCl) and trace salts (0.001–0.003 M NH4Cl/NaNO3). It was observed that when the dominant salt concentration increased, the rejections of dominant salt and trace ions decreased, whereas the membrane permeances to ions increased. This information can be useful for developing design tools for nanofiltration of mixed electrolyte solutions in water-treatment applications.Peer ReviewedPostprint (author's final draft

Application of nanofiltration for acidic waters containing rare earth elements: Influence of transition elements, acidity and membrane stability

“…resulting in negative rejection values, which in turn made the rejection of positively charged metal species higher. It is reported that membrane permeances to both salt and ions are dependent on total electrolyte concentration 24 [43]. In this study, values of permeance to single charge ions showed variations mostly lower than 10% over the 25 ionic strength (IS) range evaluated (from 1.5x10 -1 M at pH = 1 to 5x10 -2 M at pH = 2.5), while permeance values to 26 ions with higher charge decreased with the increase of IS.…”

Potential of nanofiltration and reverse osmosis processes for the recovery of high‐concentrated furfural streams

“…Figure shows the furfural rejection percentage using NF and RO membranes as a function of the trans‐membrane flux ( J v ), applying TMP from osmotic pressure to 20 bar. According to the solution‐diffusion model, it is noted that rejections increase with trans‐membrane flux until a constant plateau is reached …”

“…According to the solution-diffusion model, it is noted that rejections increase with trans-membrane flux until a constant plateau is reached. 39,42 In regard to furfural rejection, NF membranes showed different behavior between them, whereas the performance of RO membranes was similar. As can be seen in Fig.…”

“…The experimental set‐up used for NF/RO membrane testing with synthetic furfural solution is described elsewhere . Furfural feed solution was placed in a 30 L thermostatic tank, which was kept at a constant temperature (25 ± 2 °C) during the operational time.…”

“…The experimental set-up used for NF/RO membrane testing with synthetic furfural solution is described elsewhere. 42,43 Furfural feed solution was placed in a 30 L thermostatic tank, which was kept at a constant temperature (25 ± 2 ∘ C) during the operational time. This solution was pumped into a test cell (GE SEPA™ CF II) equipped with an NF or RO membrane (0.014 m 2 active membrane area) working in cross-flow mode (0.7 m s −1 ).…”