Valorization of industrial waste red mud into geopolymer adsorbent for fluoride removal from aqueous solution
DOI:
https://doi.org/10.54939/1859-1043.j.mst.111.2026.79-87Keywords:
Geopolymer; Red mud; Fluoride; Adsorption.Abstract
Red mud, a waste by-product of the Tan Rai alumina plant, was utilized as a precursor for geopolymer synthesis and evaluated for fluoride removal from water. Geopolymers were prepared by alkali activation with NaOH (1%, 5%, and 10%) and subsequently calcined at 200–800 °C. Structural and surface characterizations were performed using XRD and FT-IR. Among the tested conditions, the sample activated with 1% NaOH and calcined at 200 °C exhibited the best performance, achieving a maximum fluoride adsorption capacity of 48.31 mg/g with an equilibrium time of 4 hours, and was effective at pH ≤ 8.4. Adsorption data were best fitted to the Freundlich isotherm model compared with Langmuir and Dubinin–Radushkevich models, indicating multilayer adsorption on a heterogeneous surface. These findings highlight the potential of red mud-based geopolymer as a cost-effective adsorbent for efficient fluoride removal from contaminated water.
References
[1]. Ahmad S. et al., “Fluoride Contamination, Consequences and Removal Techniques in Water: A Review”, Environmental Science Advances, vol. 1, no. 5, pp. 620–661, (2022).
[2]. Tuyen T. N. et al., “Treatment of Fluoride in Well-Water in Khanhhoa, Vietnam by Aluminum Hydroxide Coated Rice Husk Ash”, vol. 5, no. 5, pp. 479–489, (2016).
[3]. Chauhan V., Mukherjee K., Das A., “Fluoride Adsorption on Wet-Chemically Synthesized α-Fe2O3 and γ-Al2O3 Powders: Insights from Composition and Structural Features”, Materials Chemistry and Physics, vol. 346, p. 131334, (2025).
[4]. Luo Y. et al., “Mechanism of Enhanced Fluoride Adsorption Using Amino-Functionalized Aluminum-Based Metal–Organic Frameworks”, Water, vol. 16, p. 2889, (2024). DOI: https://doi.org/10.3390/w16202889
[5]. Tan T. L. et al., “Adsorptive, Kinetics and Regeneration Studies of Fluoride Removal from Water Using Zirconium-Based Metal Organic Frameworks”, RSC Advances, vol. 10, no. 32, pp. 18740–18752, (2020).
[6]. Hettithanthri O. et al., “Temperature Influence on Layered Double Hydroxide Tailored Corncob Biochar and Its Application for Fluoride Removal in Aqueous Media”, Environmental Pollution, vol. 320, p. 121054, (2023).
[7]. Guo S. et al., “Enhanced Fluoride Removal from Drinking Water by Activated Carbon Supported Ce–Al Oxides: Performance and Mechanism”, RSC Advances, vol. 15, no. 18, pp. 14363–14374, (2025).
[8]. Li X. et al., “Kinetic Study of the Fluoride Removal by Gypsum Using Revised Pseudo-Second-Order Model: Insights on the Surface Adsorption and Precipitation”, Surfaces and Interfaces, vol. 62, p. 106304, (2025).
[9]. Gao Y. et al., “Reuse of Waste Alum-Sludge for Fluoride Removal with Nano ZrO2 Modification: Compressive Strength Optimization, Mechanism and Fixed Bed Column Adsorption”, Journal of Water Process Engineering, vol. 70, p. 106912, (2025).
[10]. Genç H. et al., “Adsorption of Arsenate from Water Using Neutralized Red Mud”, Journal of Colloid and Interface Science, vol. 264, no. 2, pp. 327–334, (2003).
[11]. P. Thao et al., “Preparation of Adsorbents from Red Mud for Removal of Fluoride in Industrial Wastewater”, Vietnamese Journal of Chemistry, vol. 51, no. 2, pp. 195–200, (2012).
[12]. Siyal A. A. et al., “A Review on Geopolymers as Emerging Materials for the Adsorption of Heavy Metals and Dyes”, Journal of Environmental Management, vol. 224, pp. 327–339, (2018).
[13]. Liu J. et al., “Investigation on Red Mud and Fly Ash-Based Geopolymer: Quantification of Reactive Aluminosilicate and Derivation of Effective Si/Al Molar Ratio”, Journal of Building Engineering, vol. 71, p. 106559, (2023).
[14]. Sun Z. et al., “Mechanical and Environmental Characteristics of Red Mud Geopolymers”, Construction and Building Materials, vol. 321, p. 125564, (2022).
[15]. Qaidi S. M. A. et al., “Sustainable Utilization of Red Mud Waste (Bauxite Residue) and Slag for the Production of Geopolymer Composites: A Review”, Case Studies in Construction Materials, vol. 16, p. e00994, (2022).
[16]. Cong T. D. et al., “Effect of Calcium Hydroxide on Compressive Strength and Microstructure of Geopolymer Containing Admixture of Kaolin, Fly Ash, and Red Mud”, Applied Sciences, vol. 13, no. 8, p. 5034, (2023).
[17]. Ayawei N., Ebelegi A. N., Wankasi D., “Modelling and Interpretation of Adsorption Isotherms”, Journal of Chemistry, vol. 2017, no. 1, p. 3039817, (2017).
[18]. “4500-F- Fluoride”, in Standard Methods for the Examination of Water and Wastewater, American Public Health Association, (2017).
[19]. Razeghi Tehrani P. et al., “Compatibility Studies of N-A-S-H and C-A-S-H Gels in Alkali-Activated Geopolymer Mortar”, Iranian Journal of Chemistry and Chemical Engineering, vol. 43, no. 10, pp. 3737–3747, (2024).
[20]. Li C. J. et al., “Development of Porous and Reusable Geopolymer Adsorbents for Dye Wastewater Treatment”, Journal of Cleaner Production, vol. 348, p. 131278, (2022).
