Fluoride removal from water using process residues from the cement, aggregate, and ceramic industries

The escalating demand for drinking water, coupled with the contamination of surface water sources, has intensified interest in harnessing groundwater for water supply. Elevated fluoride levels in groundwater, surpassing recommended limits (1.5 mgL-1), pose a significant challenge, prohibiting the supply of water to the public. Various techniques exist for fluoride removal, with adsorption standing out for its versatility, simplicity, cost-effectiveness, and efficiency. This study assessed the kinetics and adsorption capacity of residues from the ceramic and cement industries, specifically process residues (PR) from red roof tiles, bricks, and cellular concrete. These materials, derived from the construction industry’s waste, were chosen for their accessibility and low-cost preparation. Characterization through X-ray diffractometry, X-ray fluorescence spectroscopy, and isothermal nitrogen adsorption revealed cellular concrete PR as the most promising adsorbent due to its larger specific surface area (28.2 m2 g-1) compared to brick PR (12.6 m2 g-1), and roof tile PR (2.366 m2 g-1). Adsorption capacity followed the order: cellular concrete PR > brick PR > roof tile PR. Kinetics adhered to pseudo-first-order and pseudo-second-order models, while equilibrium studies aligned with Langmuir, Freundlich, and Sips models. Langmuir’s Qmax values were 1.04, 0.709, and 1.66 (mg g-1) for cellular concrete PR, brick PR, and roof tile PR, respectively, illustrating the correlation between adsorption capacity and specific surface area.