Nanofiltration membrane performance on fluoride removal from water

Fluoride concentration in drinking water is very important for human health. Optimal fluoride content is within the range of 0.5–1.0 mg/L. Nanofiltration (NF) membrane performance on fluoride removal from high fluoride content water was investigated in this study. The membranes used are negatively charged commercial thin-film composite (TFC) membranes (DS-5-DL, DS-51-HL and SR-1). The membrane performance was interpreted in terms of membrane parameters: pure water permeability (LP), pore radius (rP) and constant surface electrical potential (ψ). The parameters were obtained by fitting the 100 and 1000 ppm single salt (NaF) experimental data to a mathematical model that was developed based on the extended Nernst–Planck equation and the Grahame equation. The experimental results indicated that the rejection of NaF increased with the applied pressure and the solution flux increasing and the feed concentration decreasing. The experimental data were compared with the model developed. The model was also used to predict the membrane performance at 20 and 2000 ppm NaF solutions.