Effect of salt mixture concentration on fractionation with NF membranes

A combined ion exchange–nanofiltration process for water desalination: II. Membrane selection

“…This leads to lower rejection of chloride ions when the concentration of sulphate ions in the NaCl,50% NaCl,30% NaCl,10% feed increases. A number of earlier studies reported a significant decrease in chloride rejection when Na 2 SO 4 was added to the feed solution [13][14][15]. For NF270 membrane rejection of chloride ions is dramatically reduced at high Na 2 SO 4 to NaCl concentration ratios and even negative rejection is observed during treatment of 5000 and 10,000 mg/L salt solutions of 90%-10% Na 2 SO 4 /NaCl concentration ratio (Fig.…”

A combined ion exchange–nanofiltration process for water desalination: III. Pilot scale studies

“…Negative rejection of chloride ions as have been discussed previously is attributed to the Donnan distribution of salt between the solution and the membrane [14][15][16][17]. As almost all of the sulphate ions are rejected and with greater permeation flux of sodium ions at higher feed concentration, more chloride ions are drawn toward the permeate side in order to preserve the electroneutrality principle [18][19][20][21]. Toward the end of the filtration test and at 86% recovery, the membrane rejection of chloride ions fell down to − 87.0%.…”

Removal of Cr(III) ions from salt solution by nanofiltration: experimental and modelling analysis

“…(13) (13) into equation (1) and rearranging it, we get the following expression for the concentration gradient (14). (14) By applying the conditions expressed in equations (10), (11) and (12) to equation (3) and rearranging it, we get the following expression for the electrical potential gradient (15). (15) where Ψ is the electrical potential of ion inside the …”

“…After analysing of the literatures data 15- 25 we have stated that both theoretical and experimental works concerning the ions separation mechanism into nanofi ltration membranes are not still satisfactory and require further actions. Recently the modelling of nanofi ltration of salt solution has been widely investigated [15][16][17][18][19][20][21][22][23][24][25] . The mass transfer through the membrane was described by different models such as Kedem-Katchalsky 19, 20 or Spiegler-Kedem 19, 21, 25 .…”