A low cost approach to synthesize sand like AlOOH nanoarchitecture (SANA) and its application in defluoridation of water

• A practical nanostructured adsorbent for the removal of fluoride in water.
• Enhanced removal of fluoride in water.
• Preparation of nanocrystalline AlOOH at room temperature and atmospheric pressure.
• A low cost and eco-friendly approach for the granulation of nanoscale materials.
• Sand like hydraulically stable granules of nanocrystalline AlOOH.

This paper describes a chitosan template assisted synthesis of nanocrystalline aluminium oxyhydroxide (γ-AlOOH) at an ambient temperature (30 ± 2 °C) and atmospheric pressure. High ability of the composite in removing fluoride from water has been demonstrated. The structural, morphological and compositional characteristics of the composite were studied using various spectroscopic and microscopic techniques. The results showed that the composite has nanoarchitecture comprising a number of γ-AlOOH nanoparticles of size less than 10 nm attached to the fibrils of chitosan. Batch and continuous flow adsorption experiments were conducted to assess the parameters that influence the adsorption process. The parameters investigated include contact time, initial fluoride concentration, adsorbent dose, pH of the solution, co-existing ions in water, and size of the adsorbent granules. The composite showed good affinity to fluoride and the maximum uptake capacity was 13.47 (mg/g) (mg/L)−1/n as described by Freundlich isotherm model. The kinetics of adsorption was affected by the size of the granules and the kinetic data followed pseudo-second-order rate equation. Except bicarbonate and sulfate, other competing ions studied did not affect the uptake of fluoride significantly. The high affinity to fluoride, simple and eco-friendly synthesis approach demonstrate the utility of the material for defluoridation of water.