Defluoridation of water by wasted red brick paving blocks

Abstract

This study assesses the fluoride adsorption characteristics of red brick paving blocks or red pavers which is locally available and a cheap potential adsorbent for defluoridation. Batch experiments were conducted to evaluate basic parameters such as pH, contact time, dosage, and adsorbent capacity. The adsorption data were incorporated with kinetics (Lagergren pseudo-orders) and isotherm models (Langmuir, Freundlich, Dubinin–Radushkevich [DR], and Temkin) to comprehend the mechanism and types of adsorption. The data recorded in the study agreed with the applied models. The mechanism of interaction between red paver and fluoride was of complex nature as Freundlich and DR isotherm models suggest that adsorption is physisorption with little ion exchange mechanism while Lagergren’s pseudo-second order kinetics and Langmuir isotherm model outlined that adsorption could be chemisorption. The highest percentage of fluoride removal was achieved at pH range of 6–7 with 62% removal. Elemental and mineral phases on red paver before adsorption were characterized by X-ray diffraction and wavelength dispersive X-ray fluorescence and WD-XRF, major elemental and mineral components were CaO, Fe2O3, SiO2 and Al2O3 and ankerite, dolomite, calcite, and lime, respectively.