Role of starch in one pot fabrication of mesoporous gamma-alumina with excellent fluoride sorption capacity

Article Authors: Ojok, W., Moodley, B., Wasswa, J., Ntambi, E., Wanasolo, W., & Bolender, J. (2023)

    • Abstract


    Abstract
    Green synthesis of mesoporous γ-AƖ2O3, a cutting-edge material for sustainable application in medicine, engineering, energy, and water treatment, is still challenging. Our study used a one-pot strategy for facile synthesis of γ-AƖ2O3 by sol-gel method using starch from cassava waste. AƖ(OH)3 were bound to the O-H groups of the starch molecule to form the AƖ(OH)3-starch complex in a nano-network confined in starch polymer cages. Its calcination at 500℃ produced a mesoporous, highly crystalline water stable γ-AƖ2O3 with a pore size of 2.07 nm and an extensive BET surface area (215 cm2/g). Using the response surface methodology (RSM), the as-synthesized γ-AƖ2O3 was optimized for efficient fluoride removal from water. A central composite design (CCD) was used to study the effect of initial fluoride concentration, pH, contact time, and sorbent dose on fluoride removal efficiency and optimization of the process. The relative importance of the sorption process variables to the fluoride removal process was assessed using ANOVA. The quadratic model showed that the predicted response was significantly correlated with the experimental response (R2 = 0.9667), with sorbent dose and pH being the process’s most influential factors. Optimum conditions for 93.6% fluoride removal efficiency were sorbent dose of 0.5 g, initial fluoride concentration of 10 mg/L, pH 7, and contact time of 137.5 min. A weakly acidic medium favored fluoride removal from water, while the presence of PO43- and HCO3- retarded the process. The sorption data fitted well in the Langmuir isotherm (0.9783) and pseudo-second-order kinetic model (0.9999), indicative of a chemisorption process. The maximum sorption capacity towards fluoride was 207.5 mg/g. A thermodynamic study indicated that the sorption process was spontaneous and endothermic, with increased randomness at the solid-solution interface. Sorption, desorption, sustainability, and leaching tests showed that the sorbent could be used for sustainable fluoride removal at 8.3 USD/1000 liters of safe drinking water.

    Bibliographical metadata

    Journal Sustainable Chemistry for the Environment
    Publisher ELSEVIER
    Volume 3
    DOI https://doi.org/10.1016/j.scenv.2023.100034
    Related Faculties/Schools
    Affiliation
      1. School of Chemistry and Physics, University of KwaZulu-Natal, Westville Campus, Durban 4000, South Africa
      2. Department of Chemistry, Faculty of Science, Mbarara University of Science and Technology, P.O Box 1410, Mbarara, Uganda
      3. Department of Chemistry, Faculty of Science, Muni University, P.O Box 725, Arua, Uganda
      4. Department of Chemistry, College of Natural Sciences, Makerere University, P.O Box 7062, Kampala, Uganda
      5. Department of Chemistry, Faculty of Science, Kyambogo University, P.O Box 1 Kyambogo, Kampala, Uganda
      6. Department of Chemistry and Biochemistry, University of San Diego, 5998 Alcala Park, San Diego, CA 92110, USA