Fluoride adsorption on carboxylated aerobic granules containing Ce(III)

Aerobic granules (AG) were carboxylated and Ce(III) was incorporated to obtain modified granuels (Ce(III)–MAG) for removal of fluoride from aqueous solutions. The Ce(III)–MAG was characterized by SEM, FTIR, XRD and pHpzc, and the introduction of carboxyl groups and Ce(III) was confirmed. The adsorption capacity of Ce(III)–MAG for fluoride was 45.80 mg/g at neutral pH, an increase of 359% compared to the capacity of pristine AG. Adsorption was highest at pH range of 3.0–5.0. A positive effect on fluoride removal in the order of K+ ≈ Mg2+ > Ca2+ > Na+ and a negative effect in the order of NO3− > Cl− > SO42− > HCO3− > PO43− was observed. Fluoride adsorption followed the Redlich–Peterson model and the pseudo-first order model with correlation factors of 0.999 and 0.950, respectively. Ce(III)–MAG held up to 790 bed volumes and the effluent fluoride concentration remained below 1.0 mg/L (influent fluoride 10 mg/L).