Effects of Adsorbent Dosage and Particle Size on Fluoride Removal Using Calcium-Spiked Moringa oleifera Seed Powder
Main Article Content
Keywords
Fluoride removal, moringa oleifera, calcium spiking, biosorption, adsorption efficiency, defluoridation, drinking water safety, Kenya
Abstract
Access to safe drinking water remains a major challenge in fluoride-endemic regions, where excessive fluoride concentrations can lead to dental and skeletal fluorosis. This study evaluated the effects of adsorbent dosage, particle size, and particle size classification (mesh size) on the fluoride removal performance of Moringa oleifera seed powder (MOSP) in both calcium-spiked and non-spiked forms. A three-factor factorial batch adsorption experiment was conducted using initial fluoride concentration of 1ppm, dosages of 0.25–2.0 g/100 mL, particle sizes of <250 µm, 250–500 µm, and >500 µm, and mesh classifications of 20 (850 μm), 40 (425 µm), and 60(250 μm). Response variables included fluoride removal efficiency, residual fluoride concentration, and adsorption capacity (qe), measured using a fluoride ion-selective electrode. ANOVA and linear regression were applied to evaluate the dose and size response relationships. Results showed that calcium-spiked MOSP consistently outperformed non-spiked MOSP across all parameters. Fluoride removal efficiency increased with dosage, reaching 88.95% for spiked and 70.34% for non-spiked MOSP at 2.0 g. Finer particle sizes and smaller mesh fractions significantly enhanced removal efficiency and reduced residual fluoride levels, with spiked MOSP at ≤250 µm achieving 89.80% removal and residual fluoride below WHO guidelines. Regression analysis confirmed strong inverse relationships between particle size/mesh size and fluoride removal performance, and positive correlations with dosage. The improved performance of calcium-spiked MOSP is attributed to increased surface-active Ca²⁺ sites enabling precipitation of CaF₂ and enhanced adsorption via electrostatic attraction and ion exchange. These findings indicate that calcium-spiked MOSP, optimally prepared at fine particle size and moderate dosage, is a viable, locally sourced defluoridation medium suitable for rural water treatment systems.
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Geoffrey Chavaregi , Department of Chemistry & Biochemistry, School of Science, University of Eldoret. PO Box 1125-30100, Eldoret, Kenya
Department of Chemistry & Biochemistry, School of Science, University of Eldoret. PO Box 1125-30100, Eldoret, Kenya
John Kituyi Lusweti, Department of Chemistry & Biochemistry, School of Science, University of Eldoret. PO Box 1125-30100, Eldoret, Kenya
Department of Chemistry & Biochemistry, School of Science, University of Eldoret. PO Box 1125-30100, Eldoret, Kenya
Pius Keronei Kipkemboi , Department of Chemistry & Biochemistry, School of Science, University of Eldoret. PO Box 1125-30100, Eldoret, Kenya
Department of Chemistry & Biochemistry, School of Science, University of Eldoret. PO Box 1125-30100, Eldoret, Kenya