Regeneration and Modeling of Fluoride Adsorption From Well Water in Continuous System Using Fixed-Bed Columns

This article presents studies of the adsorption of fluorides, adding different study variables, which together, to the best of our knowledge, have not been reported in the literature due to the complexity of the system, such as the use of a continuous system, well water, regeneration, and the modeling of the results; also the maximum number of adsorption-desorption cycles was determined, which was 3, with the ultimate aim of reducing operating costs. Specifically, the analyzed well water is in the Calvillito community (Aguascalientes, Mexico), with a fluoride concentration of 8.26 and 8.46 mg/L. Bone char packed in fixed-bed columns was employed and regeneration studies were conducted in the same system using HNO 3 , HCl and NaOH at 0.01, 0.1 and 1 M. The Thomas Model, Artificial Neural Networks (ANNs), Numerical Integration and Mass Transfer Zone were used for the modeling of unsymmetrical breakthrough curves obtained from the fluoride adsorption on bone char. Specifically, they show a sum up to the third adsorption cycle of 7.63, 7.05 and 8.20 mg/g for NaOH 1 M, HCl 1 M and HNO 3 0.1 M respectively, using the Thomas model. Well water and bone char were physicochemical characterized. The bone char used in some fluoride adsorption-desorption experiments was characterized by different analytical techniques: acidity and basicity, pH pzc , SEM/EDX, XRD and FT-IR.