Defluoridation of water using neodymium-modified chitosan.

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 (0.10-0.50mm) 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 24h by 4 g L(-1) of sodium hydroxide.