The performance of three anion-exchange membranes (AEMs) in the fluoride ions reduction by electrodialysis (ED) is performed on real and synthetic water. The electric potential method measures the potential difference (PD) between two synthetic anion solutions separated by ACS, AFN and AXE membranes. The selectivity of these three AEMs coupled with the membrane CMX, is a cation-exchange membrane (CEM) towards different ions. The removal rate is influenced by the thickness of the polarization layer (PL) which reduces the material transfer and provides an additional barrier. The greater the thickness δ of the PL, the longer the passage time and consequently the removal rate of anions is small. Using the unstirred layer model, δ for each ion will be determined. According to the potential measurement method, none of the tested AEMs are selective to fluoride ions and the order of selectivity is as follows: AFN> AXE> ACS. Best membrane couple selected for fluoride ion removal is ACS/CMX and ion selectivity follows the order: Cl−> NO−3>F−> HCO−3> SO42−. For ACS membrane, both the demineralization rate (DR) and δ of fluoride ions are influenced by the initial concentration of the co-ion according to the following order: NO−3> Cl−> HCO−3> SO2−4.

In Morocco, water resources are increasingly under threat due to population growth, economic expansion, and climate change. Among the proposed solutions, brackish water desalination using membrane technologies such as nanofiltration (NF) and reverse osmosis (RO) with low‐pressure membranes presents a promising alternative. This study evaluated the impact of salinity on the performance of two nanofiltration membranes (NF270 and NF90) and one reverse osmosis membrane (TM710) using three semisynthetic brackish water samples with salinities of 2, 4, and 6 g L ⁻¹ . Ion transfer mechanisms, particularly for sodium (Na ⁺ ) and chloride (Cl ⁻ ), were analyzed using the Spiegler–Kedem (SK) and Kedem–Katchalsky (KK) mathematical models. Additionally, the effects of salinity on diffusion flux (Jdiff), convection‐induced concentration (Cconv), reflection coefficient ( σ ), and solute permeability (Ps) were examined. Results indicate that the NF270 membrane exhibits the highest permeate flux, while NF90 and TM710 perform similarly. For all three membranes, permeate flux decreases almost linearly as feed water salinity increases. Regarding total dissolved solids (TDS) rejection, the TM710 membrane achieves the highest removal efficiency, followed by NF90 and then NF270. The NF270 membrane shows greater convective transport than NF90, with both diffusive and convective fluxes increasing with salinity. In contrast, the TM710 membrane operates primarily through diffusion, with TDS having little effect on its diffusion flux. NF90 and TM710 exhibit similar σ and Ps values for sodium and chloride ions, independent of TDS, highlighting the NF90's similarity to a reverse osmosis membrane. In contrast, for NF270, the sodium reflection coefficient ( σ ) increases with TDS, while solute permeability (Ps) rises for both ions due to a decline in retention efficiency.

This study aims to optimize ammonium removal from NH₄Cl‐enriched groundwater at different concentrations using an electrodialysis (ED) process. A customized design (CD) based on response surface methodology (RSM) was employed to develop predictive models and improve the performance of the demineralization system. Ion removal efficiency was evaluated in 32 unique experimental configurations, taking into account variations in three input parameters: voltage (A), initial ammonium concentration (B) and demineralization rate (C). These parameters were selected for their impact on two response variables: electric conductivity (Y₁) and final ammonium concentration (Y₂). An in‐depth analysis of variance (ANOVA) was performed to examine the variables and their interactions. The results indicated that Y₁ was significantly influenced by C, while Y₂ was influenced by B. In addition, the predictive models demonstrated strong correlations, with a coefficient of determination (R²) greater than 0.88 for both response variables. The RSM approach applied to optimize the parameters studied identified the following optimum values: 14.17 V for A, 1 mg/L for B and 70 % for C, giving Y₁ of 215.377 μS/cm and Y₂ of 0.279 mg/L.

This study primarily investigates the effect of feed concentration on the fluoride ion permeability coefficient (Ps) and reflection coefficient (σ) for two membranes: TW30 (reverse osmosis) and NF270 (nanofiltration), using three transport models: the Kedem–Katchalsky (KK), Spiegler–Kedem (SK), and the Nernst–Planck model coupled with film theory (NP-TF). Pore size estimation was performed using three distinct models: Steric hindrance pore (SHP), Ferry (neglecting solute-pore wall interactions), and Verniory (accounting for frictional forces). Experiments were conducted with sodium fluoride (NaF) solutions in distilled water across fluoride concentrations ranging from 10 to 25 mg/L. A linear relationship was observed between the initial fluoride concentration and σ for both membranes, accompanied by a progressive decrease in Ps. This concentration dependence was more pronounced for the NF270 membrane than for the TW30 membrane. The NF270 membrane's pore diameter varied significantly by model: 0.193 nm (SHP), 0.221 nm (Ferry), 0.243 nm (Verniory). This highlights complex solute transport involving diffusive-convective flow, influenced by steric exclusion and pore frictional forces. Conversely, TW30's dense polyamide structure facilitates diffusive transport via solution-diffusion. Its hydraulic pore diameter averages 0.17 nm. Thus, size exclusion and frictional effects persist but play a reduced role in fluoride rejection.

This study evaluates the performance of electrodialysis (ED) using the CMX/ACS membrane pair, nanofiltration (NF) with the NF90 or NF270 membranes, and reverse osmosis (RO) with the BW30 membrane for fluoride removal in groundwater from Ben Guerir. This region is characterized by a salinity of 1.2 g/L and a fluoride concentration of 2.32 ppm. The results indicate that ED achieved good water quality with a demineralization rate of 40% at a cost of 0.2275 AMD/m3. NF using the NF270 membrane produced water of acceptable quality for a cost of 0.1033 AMD/m3. In contrast, both RO with the BW30 membrane and NF with the NF90 membrane yielded water with a highly aggressive chemical profile, necessitating remineralization. Remineralization, achieved by adding filtered water, reduced the cost to 0.0650 AMD/m3 for the NF90 membrane and 0.0658 AMD/m3 for the BW30 membrane, whereas remineralization using lime resulted in costs of 0.126 AMD/m3 for NF90 and 0.1343 AMD/m3 for BW30. In conclusion, the findings suggest that the most efficient and cost-effective solution for fluoride removal in this context is either NF using the NF90 membrane or RO with the BW30 membrane, combined with remineralization by adding filtered water.