Advanced Journal of Environmental Science and Technology

Advanced Journal of Environmental Science and Technology ISSN 2756-3251, Vol. 15 (7), pp. 001-010, July, 2024. Available online at www.internationalscholarsjournals.org © International Scholars Journals

Full Length Research Paper

Laterite-Based Fluoride Removal: Equilibrium Adsorption Studies on Acid-Treated Kenyan Lateritic Mineral

Enos W. Wambu1,2*, Charles O. Onindo2, Willis J. Ambusso3 and Gerald K. Muthakia4

1Department of Chemistry, Bondo University College, P. O. Box 210 -60401, Bondo, Kenya.
2Department of Chemistry, Kenyatta University, P. O. Box 43844 -00100, Nairobi, Kenya.
3Department of Physics, Kenyatta University, P. O. Box 43844 -00100, Nairobi, Kenya.

4Department of Chemistry, Kimathi University College of Technology, P. O. Box 657 -10100 Nyeri, Kenya.

Accepted 5 April, 2024

Adsorption of fluoride (F) ions from water using acid treated lateritic mineral (LM-1) from Kenya was studied by batch experiments. The effect of acid-treatment of adsorbent and change in temperature, mass of LM-1, pH and selected competing ions was evaluated. The adsorption process was strongly influenced by temperature, pH and adsorbent dosage. The percentage F removal increased the presence of the nitrate and the chlorate ions but decreased the presence of sulphates, chloride and phosphate ions. Adsorption isotherms were classified according to Giles’ classification and the adsorption data validated using Langmuir and Freundlich isotherms. The data correlated to both the Langmuir and Freundlich isotherms although the data fit to the Freundlich model was somehow better. This showed that F adsorption onto LM-1 followed a mixed adsorption mechanism in which physisorption reactions involving intra-particle diffusion of F into mesoporous sites in LM-1 became increasingly important at higher concentrations and temperatures whereas ion-exchange mechanism involving surface OH- appear to dominate at low surface coverage in more alkaline conditions. With maximum adsorption capacity of 10.5 mg/g, LM-1 could be used to remove F water.

Key words: Equilibrium analysis, fluoride adsorption, Langmuir and Freundlich isotherms, Lateritic mineral adsorbent, low-cost adsorbents.