Defluoridation of water using neodymium-modified chitosan

Abstract

The water containing high fluoride ions could do harm to human and environment. In this work, the applicability of neodymium-modified chitosan as adsorbents for the removal of excess fluoride ions from water was studied. The effect of various physico-chemical parameters such as temperature (283–323 K), pH (5–9), adsorbent dose (0.2–2.0 g L −1), particle size (0.10–0.50 mm) and the presence of co-anions (NO 3 −, Cl − and SO 4 2−) on removal of fluoride ions were studied. The equilibrium sorption data were fitted reasonably well for Langmuir isotherm model, the maximum equilibrium sorption had found to be 11.411–22.380 mg g −1. Sorption dynamics study revealed that the pseudo-second-order was suitable to describe the kinetics process of fluoride ions sorption onto the adsorbent with the initial sorption rate 1.70, 2.10 and 2.67 mg g −1 min −1 at 283, 303 and 323 K, and the sorption process was complex, both the boundary of liquid film and intra-particle diffusion contributed to the rate-determining step. The used adsorbents could be regenerated in 24 h by 4 g L −1 of sodium hydroxide.