In the current work, alumina modified natural zeolite (Z-Al) was used for fluoride adsorption in aqueous solution. Effects of process parameters such as pH, temperature, initial concentration and contact time were investigated. Box–Behnken design was found effective in defining the operating conditions for fluoride sorption onto Z-Al. Confirmatory experiments were conducted to examine the reliability of the regression equation. The predicted (2.261 mg g−1) and experimental (2.289 mg g−1) capacities were found similar demonstrating the accuracy of the model. The fluoride adsorption onto Z-Al was well described by Freundlich model. Kinetic studies revealed that the adsorption followed pseudo-second-order reaction. Thermodynamic parameters depicted that the fluoride adsorption on the alumina modified zeolite was a spontaneous and exothermic process. The co-existing ions affected the defluoridation performance significantly. Regeneration of exhausted Z-Al was achieved with H2SO4.
- experimental design
- First received 11 November 2016.
- Accepted in revised form 25 April 2017.
- © IWA Publishing 2017