T.M. VISHNU MAYA, BENCY JOHN, S.R. SARITHA, A. KRISHNAKUMAR, D.S. JAYA AND K. ANOOP KRISHNAN
Abstract
Excessive fluoride in drinking water is a critical global health issue, causing dental and skeletal fluorosis in millions of individuals, particularly in regions dependent on contaminated groundwater. Borewell water often contains elevated fluoride concentrations due to geogenic leaching from fluoride-bearing minerals. This study reports the synthesis and application of a surface tuned metal oxide-clay composite (ZnO-Bentonite clay composite) for efficient fluoride removal from borewell waters. Batch adsorption experiments systematically evaluated the effects of pH (2-10), initial fluoride concentration (5-50 mg/l), agitation time (1-90 min), and temperature (20-50 °C). Optimal removal was achieved at pH 4.0, 30 min contact time, 2 g/l adsorbent dose and 30 °C temperature, yielding 97.2% and 92.5% adsorption for initial fluoride concentrations of 5 and 10 mg/l, respectively. Equilibrium studies showed that the data is fitted the Langmuir isotherm (R²> 0.94), with a maximum adsorption capacity (qm) of 22.22 mg/g. Field-scale validation using borewell samples from the Tungabhadra River Basin demonstrated near-complete fluoride removal (99.9%), confirming the materialâs operational feasibility. The results highlight the potential of the metal oxideâclay composite as a low-cost, scalable, and highly effective adsorbent for fluoride remediation in rural and fluoride-endemic regions.