Abstract
Fluoride forms a common aqueous effluent in many chemical industries. Excess of fluoride in the effluent can cause a health hazard. So, effluent containing fluoride needs treatment to reduce its concentration to a disposable value before discharging into public sewage. Removal of fluoride ion from model water solutions was investigated using polyamide thin film composite reverse osmosis and nanofiltration membranes. The effects of feed pressure, concentration, ionic strength, nature of cation associated to fluoride, and pH on the retention of fluoride ions were studied. Membranes were used to reduce fluoride ions and total salinity of a metal packaging industrial effluent. The retention of fluoride exceeds 90% for both membranes. This was found to depend on feed concentration, ionic strength, pH, and applied pressure. The Spiegler-Kedem model was applied to experimental results to determine phenomenological parameters σ and P
s
, the reflection coefficient of the membrane and the solute permeability coefficient of ions. The convective and diffusive parts of the mass transfer were quantified with predominance of the diffusive contribution.