Granulation of Fe-Al-Ce nano-adsorbent for fluoride removal from drinking water using inorganic binder

Nano-adsorbents usually have high fluoride adsorption capacity. However, they cannot be used in packed beds because of their low hydraulic conductivity. Granulation with organic binder usually causes a great loss of adsorption capacity due to the active sites of the adsorbent being extensively occupied by the organic binder. Using inorganic sol as a binder is expected to have a potential for reducing the loss of adsorption capacity. In this paper, aluminium, zirconium, titanium and silica sol were employed as binders for Fe-Al-Ce nano-adsorbent granulation. The nano-adsorbent was mixed with sol and dried to form lumps, then calcinated and ground into powder. The morphology, adsorption capacity and structure of the compound powder were analysed. As an optimization, aluminium sol was selected as a binder in the granulation of Fe-Al-Ce nano-adsorbent using extrusion method. The effects of sol on the adsorbent and the granule structure were characterized. The granules showed a high adsorption capacity, reaching over 90% capacity of Fe-Al-Ce nano-adsorbent, much higher than that of using acrylic-styrene copolymer latex as a binder in our previous research. It is inferred that aluminium sol is a suitable binder which does no damage to the active hydroxyl group of Fe-Al-Ce adsorbent.