IWRA Proceedings

AbstractThis investigation concerns the use of nanofiltration (NF) to remove excess fluoride from drinking water. The regular ingestion of water with fluoride ions concentration higher than 2mg.L-1 causes serious health diseases like dental and bone fluorosis all over the world [1]. The nanofiltration (NF) membrane is a type of pressure-driven membrane which properties is situated between reverse osmosis (RO) and ultrafiltration (UF) membranes. NF offers several advantages such as low operational pressure, high flux, high retention of multivalent anion salts and organics compounds with molecular weight above 300 Da, relatively low investment and low operation and maintenance costs. Because of these advantages, the applications of NF worldwide have increase. The history of NF dates back to the 1970s when RO membranes with a reasonable water flux operating at relatively low pressures were developed. Hence, the high pressures traditionally used in RO resulted in a considerable energy cost. Thus, membranes with lower rejections of dissolved components, but with higher water permeability, would be a great improvement for separation technology. Such low-pressure RO membranes became known as NF membranes. By the second half of the 1980s, NF had become established, and the first applications were reported as detailed in a recent review [2]. Today 10% of brackish waters market in the world is dedicated to nanofiltration (NF) membranes [3]. While nanofiltration is a relatively new membrane process, it is already widely used for water treatment in different parts of Europe, Israel and the US. Striving towards improved quality, efficiency and applicability, research is continuing in an attempt to understand and model the varying parameters involved during NF. A technique that is often used for the evaluation of membranes is the flux and rejection behaviour of uncharged and charged solutes [4]. In this work many commercialized RO and NF membranes have been screened in order to find a suitable membrane for water defluoridation in the future, as illustrated in the Fig. 1. Our work shows that the more efficient NF membrane for water defluorination are those presenting solution-diffusion mass transfer. References : [1] Fluoride SERIE Vol.2, Fluoride and Environment, Elsevier, in press (2006); [2] N. Hilal, H. Al-Zoubi, N. A. Darwish, A. W. Mohammad, M. Abu Arabi, Desalination, 170 (2004) 281; [3] J.M. Rovel, State and behaviour of seawater desalination in the future, Proceedings of CHEMRAWNXV, 21-23 june 2004, Paris, 22-28; [4] H.M. Krieg, S.J. Modise, K. Keizer, H.W.J.P Neomagus, Desalination, 171 (2004) 205.