Adsorption of phosphate and fluoride from fertilizer industry effluent using fly ash and chitosan nano-adsorbents

The waste water generated from a chemical fertilizer industry contains different organic and inorganic pollutants. The adoption of low-cost, easily available materials in effluent treatment has recently attracted huge interest. The present study used fly ash and chitosan, modified with titanium dioxide, for the adsorption of phosphate and fluoride from fertilizer industry effluent. Batch adsorption experiments were conducted in the laboratory in order to evaluate the phosphate and fluoride removal efficiency of modified fly ash and chitosan. The adsorption of phosphate and fluoride onto fly ash and chitosan nano-composites as a function of initial ion concentration, adsorbent dosage, contact time and solution pH was investigated for optimization. The adsorbents were characterized by X-ray diffraction and FTIR spectroscopy. Fly ash and chitosan nano-composites showed a removal efficiency of above 90% for phosphate from the effluent sample and the maximum adsorption was at acidic pH. Fly ash removed 60% of the fluoride, whereas chitosan removed fluoride with an efficiency of more than 80%. Effective fluoride adsorption occurs in the pH range of 4–6 and decreases with an increase in pH. The sorption data were represented using Freundlich and Langmuir isotherm models, where the data were best filled by Freundlich isotherm model.