A SIMPLE PROCEDURE FOR THE ROUTINE DETERMINATION OF THE STANDARD DEFLUORIDATION CAPACITY OF MEDIA

The ability of defluoridation media to up-take fluoride (F) from water solutions is best described by both the intensity sorption constant and the capacity sorption constant in the best fitting of the two sorption models: Freundlich and Langmuir. However, when it comes to defluoridation of water for drinking purposes, the focus has to be constrained to initial F concentrations that are comparable with the waters that often occur in fluorotic areas and are likely to be considered as raw water sources for drinking and, furthermore, to residual F concentrations that are considered safe for cooking and drinking. This paper defines a "standard defluoridation capacity" for defluoridation media as the capacity in mg of removable F per g of the used medium in a batch experiment, where the initial F concentration is 5 mg/L and the residual concentration is about 1 mg/L. A procedure for the determination of the standard F removal capacity of media is described. The simplicity of the test makes it useful for comparing the defluoridation capacities of large numbers of media and in the routine quality control of the same processed medium, as in factory production. Examples are shown where the standard defluoridation capacity is either determined by this test or derived from literature data. In addition, the standard defluoridation capacity procedure may be a useful tool to standardize the quality check of the defluoridated waters.